WEBVTT 00:00:00.120 --> 00:00:02.460 The following content is provided under a Creative 00:00:02.460 --> 00:00:03.850 Commons license. 00:00:03.850 --> 00:00:06.090 Your support will help MIT OpenCourseWare 00:00:06.090 --> 00:00:10.180 continue to offer high-quality educational resources for free. 00:00:10.180 --> 00:00:12.720 To make a donation or to view additional materials 00:00:12.720 --> 00:00:16.475 from hundreds of MIT courses, visit MIT OpenCourseWare 00:00:16.475 --> 00:00:17.100 at ocw.mit.edu. 00:00:26.032 --> 00:00:27.240 CATHERINE DRENNAN: All right. 00:00:27.240 --> 00:00:31.950 So moving to today's handout, this 00:00:31.950 --> 00:00:33.840 is one of my favorite parts of the course. 00:00:33.840 --> 00:00:37.500 Honestly, when I first started teaching 5.111, 00:00:37.500 --> 00:00:41.430 I said transition metals are rarely covered 00:00:41.430 --> 00:00:43.080 in the intro chemistry courses. 00:00:43.080 --> 00:00:45.810 Is it really necessary to cover it here? 00:00:45.810 --> 00:00:47.940 And I was told it absolutely was. 00:00:47.940 --> 00:00:52.110 It's one of the reasons that a 5 on the AP exam 00:00:52.110 --> 00:00:54.450 is not good enough, that you have to take the Advanced 00:00:54.450 --> 00:00:55.440 Standing exam. 00:00:55.440 --> 00:00:57.690 Because the people who teach inorganic chemistry 00:00:57.690 --> 00:01:00.750 found that people who placed out of 5.111 00:01:00.750 --> 00:01:02.220 didn't do as well in their course 00:01:02.220 --> 00:01:04.620 as people who took 5:111 here. 00:01:04.620 --> 00:01:06.570 So this is one of the reasons. 00:01:06.570 --> 00:01:08.250 And then I started teaching it, and I 00:01:08.250 --> 00:01:10.590 realized this is one of the-- even 00:01:10.590 --> 00:01:12.200 though people haven't seen it before 00:01:12.200 --> 00:01:15.270 and sometimes will get a little scare-- it's actually 00:01:15.270 --> 00:01:16.500 one of the most fun units. 00:01:16.500 --> 00:01:18.720 So I absolutely love it, and hopefully you 00:01:18.720 --> 00:01:19.729 will love it by the end. 00:01:19.729 --> 00:01:21.270 People are like, we never covered it. 00:01:21.270 --> 00:01:22.270 Why are you covering it? 00:01:22.270 --> 00:01:24.090 We're in chapter 16. 00:01:24.090 --> 00:01:24.960 It's fun. 00:01:24.960 --> 00:01:25.860 OK. 00:01:25.860 --> 00:01:31.140 So transition metals, d-block metals, 00:01:31.140 --> 00:01:33.330 because they have those d orbitals. 00:01:33.330 --> 00:01:36.720 Yes, we're going back to talking about orbitals again. 00:01:36.720 --> 00:01:38.280 And they're called transition metals 00:01:38.280 --> 00:01:41.760 because you transition from this part of the periodic table 00:01:41.760 --> 00:01:43.140 with your, what kind of orbitals? 00:01:43.140 --> 00:01:43.895 AUDIENCE: s. 00:01:43.895 --> 00:01:44.770 CATHERINE DRENNAN: s. 00:01:44.770 --> 00:01:46.950 To this part of your periodic table with your, what kind of 00:01:46.950 --> 00:01:47.440 orbitals? 00:01:47.440 --> 00:01:47.930 AUDIENCE: p. 00:01:47.930 --> 00:01:48.805 CATHERINE DRENNAN: p. 00:01:48.805 --> 00:01:51.900 So they are the transition metals, 00:01:51.900 --> 00:01:54.720 and they're often really reactive and very cool. 00:01:54.720 --> 00:01:57.510 And many of them, since we're on a biological theme, 00:01:57.510 --> 00:01:59.850 many of them are super important in biology. 00:01:59.850 --> 00:02:02.100 And I have some of these written down in your notes, 00:02:02.100 --> 00:02:04.140 but here they are up here. 00:02:04.140 --> 00:02:07.980 In the transition metals, you have a lot of metals 00:02:07.980 --> 00:02:10.139 that we could not live without. 00:02:10.139 --> 00:02:13.650 Iron carries oxygen to our blood, very important, 00:02:13.650 --> 00:02:16.020 hemoglobin. 00:02:16.020 --> 00:02:17.940 We talked about cobalt just now. 00:02:17.940 --> 00:02:20.220 That is the metal in vitamin B12. 00:02:20.220 --> 00:02:22.200 So we know why that's important. 00:02:22.200 --> 00:02:24.040 We have zinc everywhere. 00:02:24.040 --> 00:02:27.210 Nickel's important for bacteria, not so much for us. 00:02:27.210 --> 00:02:28.650 But bacteria is important for us, 00:02:28.650 --> 00:02:30.690 so therefore nickel's important to us. 00:02:30.690 --> 00:02:33.480 So all of these are really important. 00:02:33.480 --> 00:02:37.950 Also, this part of the periodic table is a part of the table 00:02:37.950 --> 00:02:41.160 that people love that want to make pharmaceuticals or want 00:02:41.160 --> 00:02:44.100 to make new kinds of electrodes or batteries 00:02:44.100 --> 00:02:46.450 or all sorts of things. 00:02:46.450 --> 00:02:49.080 There's a bunch that are used as probes. 00:02:49.080 --> 00:02:52.470 We talked about imaging agents, detecting cancer, and all sorts 00:02:52.470 --> 00:02:53.970 of different things like that. 00:02:53.970 --> 00:02:58.680 Many of these transition metals are used in those probes 00:02:58.680 --> 00:03:01.590 and also in pharmaceuticals. 00:03:01.590 --> 00:03:04.770 And so this is sort of a very rich part 00:03:04.770 --> 00:03:07.740 of the periodic table, where those d orbitals allow 00:03:07.740 --> 00:03:09.810 for properties that are incredibly 00:03:09.810 --> 00:03:13.410 useful for our health and for doing all sorts of stuff. 00:03:13.410 --> 00:03:15.360 So I love this part. 00:03:15.360 --> 00:03:19.470 Again, some of the biological-- global cycling of nitrogen. 00:03:19.470 --> 00:03:22.110 We talked about nitrogen fixation, that triple bond. 00:03:22.110 --> 00:03:24.570 It's really hard to break nitrogen apart, 00:03:24.570 --> 00:03:26.130 but bacteria can do it. 00:03:26.130 --> 00:03:29.010 It does it using transition metals. 00:03:29.010 --> 00:03:31.640 Fixing carbon, hydrogenase, if you 00:03:31.640 --> 00:03:34.740 want to make hydrogen fuel cells that are more biological. 00:03:34.740 --> 00:03:37.980 Again, biology uses transition metals in this. 00:03:37.980 --> 00:03:41.670 Making vitamins, making deoxynucleotides, respiration, 00:03:41.670 --> 00:03:45.260 photosynthesis, it's all due to transition metals. 00:03:45.260 --> 00:03:45.760 All right. 00:03:45.760 --> 00:03:48.000 So we'll start with just one example, 00:03:48.000 --> 00:03:50.790 or one of In Our Own Words segment. 00:03:50.790 --> 00:03:53.250 And this focuses on nickel, which is something 00:03:53.250 --> 00:03:55.410 very important in bacteria. 00:03:55.410 --> 00:03:58.890 And this is actually an example from a collaborative project 00:03:58.890 --> 00:04:00.780 between my lab and course 6. 00:04:00.780 --> 00:04:02.280 And I know a lot of you are thinking 00:04:02.280 --> 00:04:04.560 about being course 6 majors, so I 00:04:04.560 --> 00:04:07.560 thought I would tell you about some research of Collin 00:04:07.560 --> 00:04:09.390 Stultz, a course 6 professor. 00:04:09.390 --> 00:04:11.910 So he was doing some computational analysis 00:04:11.910 --> 00:04:15.040 on these proteins that we're studying. 00:04:15.040 --> 00:04:17.579 So many of you at this point in the semester 00:04:17.579 --> 00:04:19.730 probably feel like you might be getting an ulcer. 00:04:19.730 --> 00:04:21.579 But unless you have H. pylori in your gut, 00:04:21.579 --> 00:04:24.180 you probably are not actually getting an ulcer. 00:04:24.180 --> 00:04:26.600 And you just take a little B12, you'll feel a lot better. 00:04:26.600 --> 00:04:27.360 OK. 00:04:27.360 --> 00:04:27.650 So here's the video. 00:04:27.650 --> 00:04:28.316 [VIDEO PLAYBACK] 00:04:28.316 --> 00:04:31.740 - My name is Sarah Bowman, and I am a post-doctoral fellow 00:04:31.740 --> 00:04:33.240 at MIT. 00:04:33.240 --> 00:04:36.930 I am working on studying a protein 00:04:36.930 --> 00:04:41.220 from Helicobacter pylori, which is pathogenic bacteria. 00:04:41.220 --> 00:04:46.570 Its kind of ecological niche is in mammalian stomachs. 00:04:46.570 --> 00:04:50.140 It's actually very difficult to treat using antibiotics, 00:04:50.140 --> 00:04:52.480 because a lot of times when you're given 00:04:52.480 --> 00:04:55.900 antibiotics they're going to actually be broken apart 00:04:55.900 --> 00:04:59.050 by the acidity of the stomach before they actually ever 00:04:59.050 --> 00:05:02.980 get to killing the Helicobacter pylori. 00:05:02.980 --> 00:05:05.050 Transition metals in biological systems 00:05:05.050 --> 00:05:07.120 are actually really important. 00:05:07.120 --> 00:05:09.850 They increase the range of reactivity 00:05:09.850 --> 00:05:14.020 that proteins and enzymes are able to access. 00:05:14.020 --> 00:05:16.180 Nickel is a transition metal. 00:05:16.180 --> 00:05:19.000 I mean, it's a transition metal that's actually fairly 00:05:19.000 --> 00:05:22.300 rare in biological systems. 00:05:22.300 --> 00:05:26.380 So one of the big things that H. pylori uses nickel for 00:05:26.380 --> 00:05:29.440 is an enzyme called urease. 00:05:29.440 --> 00:05:36.700 Urease requires something like 24 nickel ions, which is a lot. 00:05:36.700 --> 00:05:38.680 Urease is one of the proteins that 00:05:38.680 --> 00:05:42.730 allows for a lot of buffering capacity of the organism, 00:05:42.730 --> 00:05:45.180 of the H. pylori organism. 00:05:45.180 --> 00:05:50.170 The stomach pH is very low, so pH 2-something. 00:05:50.170 --> 00:05:53.470 And this bacteria has to swim through the stomach 00:05:53.470 --> 00:05:54.820 and then colonize it. 00:05:54.820 --> 00:05:57.460 And you'd think that the stomach would just break it apart 00:05:57.460 --> 00:06:00.700 like it breaks apart your food. 00:06:00.700 --> 00:06:05.560 But in fact, the bacteria itself has mechanisms in place 00:06:05.560 --> 00:06:07.990 that allow it to create buffers that 00:06:07.990 --> 00:06:09.550 allow it to move through the stomach 00:06:09.550 --> 00:06:11.839 and live in the stomach. 00:06:11.839 --> 00:06:14.380 And one of those enzymes, and it's really important for that, 00:06:14.380 --> 00:06:15.015 is urease. 00:06:18.040 --> 00:06:21.600 In humans, nickel, as far as we can tell, 00:06:21.600 --> 00:06:24.560 is not essential for any enzymes, 00:06:24.560 --> 00:06:29.000 whereas in Helicobacter pylori, for instance, nickel 00:06:29.000 --> 00:06:31.280 is an essential transition metal. 00:06:31.280 --> 00:06:35.750 And so a really intriguing thing to kind of think about 00:06:35.750 --> 00:06:42.350 is just whether we could somehow target the nickel requirement 00:06:42.350 --> 00:06:46.220 in this organism and in other bacteria that 00:06:46.220 --> 00:06:50.660 would allow us to kill these pathogenic bacteria while not 00:06:50.660 --> 00:06:55.027 doing anything that would be harmful to humans. 00:06:55.027 --> 00:06:55.610 [END PLAYBACK] 00:06:55.610 --> 00:06:57.350 CATHERINE DRENNAN: So I like that video 00:06:57.350 --> 00:07:02.600 partly because it brings back acid-base and buffers, as well 00:07:02.600 --> 00:07:04.760 as talking about transition metals. 00:07:04.760 --> 00:07:09.650 And I love the bacteria being attacked by the acid 00:07:09.650 --> 00:07:12.080 and then making a buffer and saving itself. 00:07:12.080 --> 00:07:12.770 It's awesome. 00:07:12.770 --> 00:07:14.780 OK. 00:07:14.780 --> 00:07:18.890 So one of the reasons why these transition metals are 00:07:18.890 --> 00:07:21.740 so powerful, they can do so many things, 00:07:21.740 --> 00:07:24.890 is that they like to form complexes, 00:07:24.890 --> 00:07:32.450 and they like to form complexes with small molecules or ions. 00:07:32.450 --> 00:07:36.800 And those ions often will have a lone pair of electrons, 00:07:36.800 --> 00:07:38.865 and the metal wants that electron density. 00:07:38.865 --> 00:07:42.140 It wants the benefit of that lone pair. 00:07:42.140 --> 00:07:46.550 So when you have this lone pair, the metal 00:07:46.550 --> 00:07:48.380 will come in contact with that lone pair, 00:07:48.380 --> 00:07:51.470 and it'll make a very happy, very happy metal. 00:07:51.470 --> 00:07:54.230 And we can think about this interaction 00:07:54.230 --> 00:07:59.510 here as the donor atoms are called ligands. 00:07:59.510 --> 00:08:02.210 And now let's review something we learned before about 00:08:02.210 --> 00:08:05.738 whether this is a Lewis acid or a Lewis base then. 00:08:18.150 --> 00:08:19.407 OK, 10 more seconds. 00:08:35.370 --> 00:08:36.039 That's right. 00:08:36.039 --> 00:08:39.940 So it's a Lewis base. 00:08:39.940 --> 00:08:42.909 So if we put this up here, donor atoms 00:08:42.909 --> 00:08:45.580 are called ligands, which are Lewis bases, 00:08:45.580 --> 00:08:48.750 and the Lewis bases donate the lone pair of electrons. 00:08:48.750 --> 00:08:51.250 And again, we can think about the definition that we've been 00:08:51.250 --> 00:08:55.120 more used to, where a base is taking H . 00:08:55.120 --> 00:08:58.570 It's accepting the proton from the acid. 00:08:58.570 --> 00:09:01.960 But there, when it's taking H , it's taking H without its 00:09:01.960 --> 00:09:02.950 electrons. 00:09:02.950 --> 00:09:06.770 So it's actually donating its loan pairs to form a bond. 00:09:06.770 --> 00:09:09.770 And then we can think about Lewis acids. 00:09:09.770 --> 00:09:13.180 So the acceptor atoms, which are our transition metals, 00:09:13.180 --> 00:09:14.320 are Lewis acids. 00:09:14.320 --> 00:09:16.150 They accept the lone pair. 00:09:16.150 --> 00:09:21.100 And when an acid that has a proton on it loses H , 00:09:21.100 --> 00:09:24.160 it is taking the electrons with it, 00:09:24.160 --> 00:09:26.560 because H is leaving without its electrons. 00:09:26.560 --> 00:09:28.810 So these definitions work, but these are 00:09:28.810 --> 00:09:31.430 sort of more broad definitions. 00:09:31.430 --> 00:09:33.790 So here, our metals, any of our transition metals, 00:09:33.790 --> 00:09:36.370 are going to be our acceptors, our Lewis acids. 00:09:36.370 --> 00:09:37.810 And here are a bunch of ligands. 00:09:37.810 --> 00:09:38.530 We have water. 00:09:38.530 --> 00:09:39.470 We have NH3. 00:09:39.470 --> 00:09:40.600 We have CO. 00:09:40.600 --> 00:09:41.800 They have lone pairs. 00:09:41.800 --> 00:09:43.510 They can be donor atoms. 00:09:43.510 --> 00:09:47.290 And the ligands form complexes with the metals. 00:09:47.290 --> 00:09:48.960 And the kind of complexes-- they're 00:09:48.960 --> 00:09:51.400 often called coordination complexes, 00:09:51.400 --> 00:09:55.300 and that's a metal that's surrounded by ligands. 00:09:55.300 --> 00:09:58.000 And here's a little example, a metal in the middle, 00:09:58.000 --> 00:10:00.520 and it has the ligands around it. 00:10:00.520 --> 00:10:03.850 So let's consider this coordination complex now 00:10:03.850 --> 00:10:08.410 and think about what this picture is telling us. 00:10:08.410 --> 00:10:10.390 So we have our coordination complex. 00:10:10.390 --> 00:10:14.770 We have cobalt in the middle, and we have NH3 groups 00:10:14.770 --> 00:10:16.750 as our donor ligands. 00:10:16.750 --> 00:10:21.810 And here this bracket indicates the overall charge is plus 3. 00:10:21.810 --> 00:10:25.750 Again, the transition metal is going to be the Lewis acid. 00:10:25.750 --> 00:10:29.680 It's going to be accepting the lone pairs from the Lewis 00:10:29.680 --> 00:10:34.250 bases, which are the ligands, or the donor atoms. 00:10:34.250 --> 00:10:36.530 Now, we can think about a new term 00:10:36.530 --> 00:10:39.440 called "coordination number." 00:10:39.440 --> 00:10:41.900 And that's simply the number of ligands 00:10:41.900 --> 00:10:44.950 that are bound to the metal. 00:10:44.950 --> 00:10:51.960 So a CN number of 6 would indicate six ligands make up 00:10:51.960 --> 00:10:54.120 what's called the primary coordination 00:10:54.120 --> 00:10:58.350 sphere, which is the things that are bound directly 00:10:58.350 --> 00:11:00.340 to the metal. 00:11:00.340 --> 00:11:05.250 So CN numbers for transition metals range from 2 to 12, 00:11:05.250 --> 00:11:08.970 but 6 is probably the most common. 00:11:08.970 --> 00:11:12.340 So before we think about the shapes of these molecules, 00:11:12.340 --> 00:11:17.220 let's just look at the notation for this, 00:11:17.220 --> 00:11:20.730 so coordination complex notation. 00:11:20.730 --> 00:11:24.690 So I would write this structure up here 00:11:24.690 --> 00:11:29.970 within brackets-- cobalt bracket NH3. 00:11:29.970 --> 00:11:31.820 You have parentheses around NH3. 00:11:31.820 --> 00:11:33.530 There's six of those. 00:11:33.530 --> 00:11:36.440 Another bracket here with a plus 3 charge, 00:11:36.440 --> 00:11:38.850 indicating the charge on everything, 00:11:38.850 --> 00:11:40.470 this whole structure. 00:11:40.470 --> 00:11:44.400 But often, coordination complexes with a plus charge 00:11:44.400 --> 00:11:46.310 will have counterions around. 00:11:46.310 --> 00:11:50.420 So there might be, say, three chlorine minus ions around, 00:11:50.420 --> 00:11:52.670 and so that could be written like this, 00:11:52.670 --> 00:11:54.150 or it could be written like this. 00:11:54.150 --> 00:11:57.870 If you see Cl3 outside of those brackets, 00:11:57.870 --> 00:12:00.270 it means that they're counterions. 00:12:00.270 --> 00:12:03.480 So if I looked at this, I'd say NH3 is within the brackets. 00:12:03.480 --> 00:12:06.080 That means it's bound to the cobalt. So that would tell you 00:12:06.080 --> 00:12:09.720 there are six things bound to the cobalt. The Cl is outside. 00:12:09.720 --> 00:12:11.310 That indicates it's a counterion. 00:12:11.310 --> 00:12:12.730 There are three of them. 00:12:12.730 --> 00:12:15.630 So there are three counterions, which then tells you 00:12:15.630 --> 00:12:18.281 the charge must be plus 3. 00:12:18.281 --> 00:12:18.780 All right. 00:12:18.780 --> 00:12:20.170 So there is our notation. 00:12:23.281 --> 00:12:23.780 All right. 00:12:23.780 --> 00:12:28.190 So now we're back to thinking about geometries. 00:12:28.190 --> 00:12:30.800 So this is one of the things I love about this part. 00:12:30.800 --> 00:12:32.470 I feel like some people in the course 00:12:32.470 --> 00:12:34.790 are just like, new topic, new topic. 00:12:34.790 --> 00:12:37.005 Oh, man, when is the new material going to end? 00:12:37.005 --> 00:12:40.130 Well, you find you get enough into chemistry, 00:12:40.130 --> 00:12:43.790 and you start revisiting topics you've already seen before. 00:12:43.790 --> 00:12:45.440 So this is great. 00:12:45.440 --> 00:12:45.940 All right. 00:12:45.940 --> 00:12:49.430 So coordination number 6. 00:12:49.430 --> 00:12:51.550 We haven't maybe heard coordination number 6, 00:12:51.550 --> 00:12:53.010 but that's pretty easy to remember. 00:12:53.010 --> 00:12:54.940 It's the number of atoms bound. 00:12:54.940 --> 00:12:57.552 What type of geometry is this? 00:13:00.750 --> 00:13:04.241 You can just yell it out. 00:13:04.241 --> 00:13:04.740 Right. 00:13:04.740 --> 00:13:07.270 So that's octahedral geometry. 00:13:07.270 --> 00:13:11.640 Again, the solid triangles coming out 00:13:11.640 --> 00:13:13.670 indicate they're coming out at you. 00:13:13.670 --> 00:13:17.041 Back dashes are going back, and we have our axial. 00:13:17.041 --> 00:13:17.540 All right. 00:13:17.540 --> 00:13:23.607 So let's see how well you remember CN 5 structures. 00:13:23.607 --> 00:13:25.190 And you can keep this up here, and you 00:13:25.190 --> 00:13:28.310 can tell me what the name of those two geometries are. 00:13:45.050 --> 00:13:45.970 All right. 00:13:45.970 --> 00:13:47.800 Why don't you take 10 more seconds. 00:13:47.800 --> 00:13:50.710 And here are our structures in real life down here. 00:14:02.450 --> 00:14:04.480 People are just like, I want to put see-saw. 00:14:04.480 --> 00:14:05.170 No, no. 00:14:08.145 --> 00:14:10.195 That is the parent geometry of see-saw, 00:14:10.195 --> 00:14:11.600 but not see-saw itself. 00:14:11.600 --> 00:14:12.200 OK. 00:14:12.200 --> 00:14:16.440 So we have the trigonal bipyramidal 00:14:16.440 --> 00:14:17.790 and the square pyramidal. 00:14:17.790 --> 00:14:21.810 So I'm holding up the square pyramidal right now. 00:14:21.810 --> 00:14:26.220 And then we have the trigonal, because it's trigonal 00:14:26.220 --> 00:14:28.320 along here, bipyramidal. 00:14:28.320 --> 00:14:30.620 So it's sort of like one pyramid here, 00:14:30.620 --> 00:14:33.380 one pyramid there, so bipyramidal. 00:14:33.380 --> 00:14:36.950 And if I took off one and we had a lone pair, 00:14:36.950 --> 00:14:41.580 then we would get our friend the see-saw. 00:14:41.580 --> 00:14:43.130 OK. 00:14:43.130 --> 00:14:46.200 Next we have this. 00:14:46.200 --> 00:14:49.020 What's that one called? 00:14:49.020 --> 00:14:49.910 AUDIENCE: Square. 00:14:49.910 --> 00:14:51.502 CATHERINE DRENNAN: Square-- 00:14:51.502 --> 00:14:52.210 AUDIENCE: Planar. 00:14:52.210 --> 00:14:55.100 CATHERINE DRENNAN: Planar, yep. 00:14:55.100 --> 00:14:58.472 And this one? 00:14:58.472 --> 00:14:58.972 Tetrahedral. 00:15:02.790 --> 00:15:09.230 And now CN number of 3. 00:15:09.230 --> 00:15:10.592 What is this one? 00:15:10.592 --> 00:15:12.362 AUDIENCE: Trigonal-- 00:15:12.362 --> 00:15:13.820 CATHERINE DRENNAN: Trigonal planar. 00:15:13.820 --> 00:15:16.110 It's in a plane kind of, if I hold the bonds 00:15:16.110 --> 00:15:20.580 and they don't fall off, and it's kind of trigonal. 00:15:20.580 --> 00:15:23.120 And then what about the last one? 00:15:23.120 --> 00:15:23.997 AUDIENCE: Linear. 00:15:23.997 --> 00:15:25.080 CATHERINE DRENNAN: Linear. 00:15:25.080 --> 00:15:25.770 OK. 00:15:25.770 --> 00:15:29.350 And let's just run through and think about the angles as well. 00:15:29.350 --> 00:15:32.320 With octahedral, what are our angles? 00:15:32.320 --> 00:15:33.580 AUDIENCE: 90. 00:15:33.580 --> 00:15:34.530 CATHERINE DRENNAN: 90. 00:15:34.530 --> 00:15:36.200 Trigonal bipyramidal? 00:15:36.200 --> 00:15:38.670 AUDIENCE: 90 and 120. 00:15:38.670 --> 00:15:41.100 CATHERINE DRENNAN: 90 and 120, that's right. 00:15:41.100 --> 00:15:50.710 So we have one 120 around here, and then the top parts were 90. 00:15:50.710 --> 00:15:52.160 OK. 00:15:52.160 --> 00:15:55.530 We have the square pyramidal. 00:15:55.530 --> 00:15:56.340 90. 00:15:56.340 --> 00:15:57.060 Square planar? 00:15:57.060 --> 00:15:58.200 AUDIENCE: 90. 00:15:58.200 --> 00:15:59.220 CATHERINE DRENNAN: 90. 00:15:59.220 --> 00:16:00.090 Tetrahedral? 00:16:00.090 --> 00:16:02.412 AUDIENCE: 109.7? 00:16:02.412 --> 00:16:04.590 CATHERINE DRENNAN: 109.5. 00:16:04.590 --> 00:16:06.465 Give credit for 0.7 too. 00:16:06.465 --> 00:16:07.930 That's quite close. 00:16:07.930 --> 00:16:08.940 Trigonal planar? 00:16:08.940 --> 00:16:09.524 AUDIENCE: 120. 00:16:09.524 --> 00:16:10.481 CATHERINE DRENNAN: 120. 00:16:10.481 --> 00:16:11.170 And linear? 00:16:11.170 --> 00:16:11.820 AUDIENCE: 180. 00:16:11.820 --> 00:16:13.260 CATHERINE DRENNAN: 180, right. 00:16:13.260 --> 00:16:16.779 So you're going to need to remember these for this unit, 00:16:16.779 --> 00:16:19.320 but that's OK because you need to remember them for the final 00:16:19.320 --> 00:16:19.820 anyway. 00:16:19.820 --> 00:16:22.620 So it gives you a nice review. 00:16:22.620 --> 00:16:24.870 All right. 00:16:24.870 --> 00:16:27.770 So we got every one. 00:16:27.770 --> 00:16:28.940 We got them down. 00:16:28.940 --> 00:16:30.300 Can look up your old notes. 00:16:30.300 --> 00:16:31.670 Just review. 00:16:31.670 --> 00:16:32.730 All right. 00:16:32.730 --> 00:16:35.560 So coordination complexes also have another name. 00:16:35.560 --> 00:16:37.620 They can be called chelates. 00:16:37.620 --> 00:16:40.110 Just another name for coordination complex. 00:16:40.110 --> 00:16:42.990 So chelates can be the thing. 00:16:42.990 --> 00:16:44.880 But you can also say that the ligand 00:16:44.880 --> 00:16:47.310 will chelate as another way of saying 00:16:47.310 --> 00:16:50.060 that it will bind to a metal. 00:16:50.060 --> 00:16:53.730 And it can bind more than once with one or more sites 00:16:53.730 --> 00:16:54.990 of attachment. 00:16:54.990 --> 00:16:57.570 And the word "chelate" comes from claws, 00:16:57.570 --> 00:16:58.650 and I like that picture. 00:16:58.650 --> 00:17:02.300 I feel like, yes, these ligands coming in like claws 00:17:02.300 --> 00:17:03.850 and binding that metal. 00:17:03.850 --> 00:17:07.230 They're chelating that metal. 00:17:07.230 --> 00:17:09.720 So there are different names depending 00:17:09.720 --> 00:17:12.960 on how many points of attachment they have. 00:17:12.960 --> 00:17:15.960 And we have what's known as monodentate-- 00:17:15.960 --> 00:17:18.510 "dent" for dentist or tooth. 00:17:18.510 --> 00:17:23.130 So that's one point of attachment. 00:17:23.130 --> 00:17:26.819 And I bet that without having seen this material ever 00:17:26.819 --> 00:17:29.490 before you can tell me what the rest of these are. 00:17:29.490 --> 00:17:31.320 What do you think bidentate means? 00:17:31.320 --> 00:17:32.280 AUDIENCE: Two. 00:17:32.280 --> 00:17:33.330 CATHERINE DRENNAN: Two. 00:17:33.330 --> 00:17:34.350 Tridentate? 00:17:34.350 --> 00:17:35.747 AUDIENCE: Three. 00:17:35.747 --> 00:17:37.080 CATHERINE DRENNAN: Tetradentate? 00:17:37.080 --> 00:17:38.329 AUDIENCE: Four. 00:17:38.329 --> 00:17:39.620 CATHERINE DRENNAN: Hexadentate? 00:17:39.620 --> 00:17:40.180 AUDIENCE: Six. 00:17:40.180 --> 00:17:41.429 CATHERINE DRENNAN: Six, right. 00:17:41.429 --> 00:17:42.490 There's not one for five. 00:17:42.490 --> 00:17:43.450 But this is good. 00:17:43.450 --> 00:17:44.912 So don't lose a point on this. 00:17:44.912 --> 00:17:46.620 I feel like sometimes people lose a point 00:17:46.620 --> 00:17:47.950 on this on the exam. 00:17:47.950 --> 00:17:49.800 You knew it in class before I taught it. 00:17:49.800 --> 00:17:51.790 You don't want to like somehow work backwards. 00:17:51.790 --> 00:17:54.330 So this is easy points right here. 00:17:54.330 --> 00:17:56.190 Just remember on the exam, wait a minute, 00:17:56.190 --> 00:17:59.171 maybe I already know this. 00:17:59.171 --> 00:17:59.670 All right. 00:17:59.670 --> 00:18:03.870 So let's look at some examples of chelating 00:18:03.870 --> 00:18:07.560 ligands that bind with multiple points of attachment. 00:18:07.560 --> 00:18:09.480 And the first one-- we're kind of on a theme 00:18:09.480 --> 00:18:14.020 today-- is vitamin B12 that we're going to look at. 00:18:14.020 --> 00:18:17.940 So this is called the corrin ring. 00:18:17.940 --> 00:18:21.300 Cobalt is in the middle, and that ring 00:18:21.300 --> 00:18:25.050 binds with four points of attachment. 00:18:25.050 --> 00:18:29.430 So it is a tetradentate ligand, this corrin ring. 00:18:29.430 --> 00:18:31.950 There is also an upper ligand, which 00:18:31.950 --> 00:18:35.460 is 5 prime-deoxyadenosine, and a lower ligand that's 00:18:35.460 --> 00:18:37.320 called dimethylbenzimidazole. 00:18:37.320 --> 00:18:38.850 You don't need to know their names. 00:18:38.850 --> 00:18:43.470 Overall, it has six ligands in octahedral geometry. 00:18:43.470 --> 00:18:46.920 But the corrin ring is a very nice biological example 00:18:46.920 --> 00:18:49.590 of a multidentate ligand. 00:18:49.590 --> 00:18:52.050 Heme would be the same. 00:18:52.050 --> 00:18:54.780 I thought I would show you this rotating around so you 00:18:54.780 --> 00:18:57.780 get a better sense and tell you that this structure 00:18:57.780 --> 00:19:01.650 of this vitamin was determined by Dorothy Hodgkin, who 00:19:01.650 --> 00:19:04.950 won the Nobel Prize in 1964 for determining 00:19:04.950 --> 00:19:07.350 the structure by crystallography and also solving 00:19:07.350 --> 00:19:09.990 the structure of penicillin. 00:19:09.990 --> 00:19:12.810 This was the most complicated molecule 00:19:12.810 --> 00:19:15.450 to be solved by crystallography, and a lot of people 00:19:15.450 --> 00:19:17.040 said that technique could never be 00:19:17.040 --> 00:19:18.720 used to do something that big. 00:19:18.720 --> 00:19:20.760 She showed that they were wrong. 00:19:20.760 --> 00:19:24.070 In terms of determining the structure of penicillin, 00:19:24.070 --> 00:19:25.860 it was during the war. 00:19:25.860 --> 00:19:28.110 And people wanted to make more penicillin, 00:19:28.110 --> 00:19:30.270 but they had no idea what the structure was so they 00:19:30.270 --> 00:19:31.704 didn't know what to make. 00:19:31.704 --> 00:19:33.120 And she figured out the structure. 00:19:33.120 --> 00:19:34.536 And it's a weird-looking molecule, 00:19:34.536 --> 00:19:37.380 so no one would have guessed it without knowing the structure. 00:19:37.380 --> 00:19:41.650 So for her pioneering work in crystallography 00:19:41.650 --> 00:19:43.730 she won the Nobel Prize. 00:19:43.730 --> 00:19:44.250 All right. 00:19:44.250 --> 00:19:49.140 So vitamin B12 is one example of a chelate. 00:19:49.140 --> 00:19:52.830 Another that's probably more that you probably hear about 00:19:52.830 --> 00:19:54.850 the most-- it's almost synonymous with the word 00:19:54.850 --> 00:19:58.480 "chelate"-- is EDTA. 00:19:58.480 --> 00:20:01.560 Here is the EDTA molecule, and you 00:20:01.560 --> 00:20:05.070 see that it has lots of lone pairs 00:20:05.070 --> 00:20:08.910 that are just dying to grab onto a metal. 00:20:08.910 --> 00:20:10.010 So we have six. 00:20:10.010 --> 00:20:15.120 We have 1, 2, 3, 4, 5, 6, six things 00:20:15.120 --> 00:20:19.140 that are capable of chelating that metal. 00:20:19.140 --> 00:20:21.990 And so here is what the complex looks like. 00:20:21.990 --> 00:20:24.170 So the red oxygen can chelate. 00:20:24.170 --> 00:20:26.430 The green oxygen here can chelate, 00:20:26.430 --> 00:20:29.835 the nitrogen here in dark blue, the other nitrogen 00:20:29.835 --> 00:20:34.530 in dark blue here, light blue oxygen here, and also 00:20:34.530 --> 00:20:38.310 the purple oxygen. So now why don't you 00:20:38.310 --> 00:20:40.860 tell me what the geometry of this 00:20:40.860 --> 00:20:42.560 would be as a clicker question. 00:20:53.250 --> 00:20:53.957 You ready? 00:20:53.957 --> 00:20:54.582 AUDIENCE: Yeah. 00:20:54.582 --> 00:20:54.960 CATHERINE DRENNAN: Yeah. 00:20:54.960 --> 00:20:56.210 10 more seconds. 00:20:56.210 --> 00:20:57.560 Should be fast hopefully. 00:21:09.804 --> 00:21:12.660 Yeah, great, 86%. 00:21:12.660 --> 00:21:14.400 It is octahedral. 00:21:14.400 --> 00:21:16.800 And sometimes it's a little bit hard to see that, 00:21:16.800 --> 00:21:19.690 but I helped you out by drawing those bonds in black 00:21:19.690 --> 00:21:21.390 that you needed to look at. 00:21:21.390 --> 00:21:25.990 So we have four that are in the plane here, one above 00:21:25.990 --> 00:21:28.140 and one below here. 00:21:28.140 --> 00:21:30.820 So that is octahedral geometry. 00:21:30.820 --> 00:21:33.580 Also, how many points of attachment? 00:21:33.580 --> 00:21:35.410 What kind of dentate ligand is this? 00:21:37.685 --> 00:21:39.190 It's hexadentate as well. 00:21:39.190 --> 00:21:44.361 So it has six points of attachment here. 00:21:44.361 --> 00:21:44.860 All right. 00:21:44.860 --> 00:21:49.480 So EDTA is a really good metal chelator. 00:21:49.480 --> 00:21:53.040 And part of the reason that it is such an awesome metal 00:21:53.040 --> 00:21:57.110 chelator is because of entropy. 00:21:57.110 --> 00:21:59.100 So we're back to entropy again. 00:21:59.100 --> 00:22:04.630 So the binding of EDTA to the metal is entropically favored. 00:22:04.630 --> 00:22:07.240 And the reason for this is that metals that are, say, 00:22:07.240 --> 00:22:11.500 in your body, like if you happen to eat some lead paint, 00:22:11.500 --> 00:22:13.540 and that lead is hanging out. 00:22:13.540 --> 00:22:14.800 It's not just by itself. 00:22:14.800 --> 00:22:17.640 It's coordinating hopefully just to water and not 00:22:17.640 --> 00:22:19.670 to proteins in your body. 00:22:19.670 --> 00:22:25.180 But when you take some EDTA to prevent your lead poisoning, 00:22:25.180 --> 00:22:27.900 one molecule of EDTA will bind to metal, 00:22:27.900 --> 00:22:30.760 and all of these waters are going to be released. 00:22:30.760 --> 00:22:34.240 So I have over here some lead with a whole bunch 00:22:34.240 --> 00:22:35.935 of little waters. 00:22:35.935 --> 00:22:39.650 This is quite an ordered system. 00:22:39.650 --> 00:22:45.870 But if I take out all of those waters here, 00:22:45.870 --> 00:22:49.220 that's a lot more entropy going on than what we had. 00:22:49.220 --> 00:22:52.380 And then you have one chelating ligand here, 00:22:52.380 --> 00:22:54.460 and that's a pretty simple system. 00:22:54.460 --> 00:22:56.770 So this is ordered. 00:22:56.770 --> 00:22:58.300 This is disordered. 00:22:58.300 --> 00:23:04.067 So the binding of EDTA, one EDTA releases six water molecules, 00:23:04.067 --> 00:23:11.300 and that makes it very favorable to do this. 00:23:11.300 --> 00:23:14.230 And because of that, chelating molecules, 00:23:14.230 --> 00:23:16.680 or the chelate effect, molecules that are chelates, 00:23:16.680 --> 00:23:20.200 like metal bound to EDTA, are unusually stable 00:23:20.200 --> 00:23:22.540 because of this favorable entropic effect, 00:23:22.540 --> 00:23:24.220 this release of water. 00:23:24.220 --> 00:23:27.730 So the release of water, the release of increasing entropy, 00:23:27.730 --> 00:23:32.620 drives that metal chelation, and you sequester your metal, 00:23:32.620 --> 00:23:36.050 which is really good if you're trying to avoid lead poisoning. 00:23:36.050 --> 00:23:40.090 So I think this is a nice example of our friend entropy 00:23:40.090 --> 00:23:41.630 driving a reaction. 00:23:41.630 --> 00:23:44.350 So a lot of you did really well on the exam talking about 00:23:44.350 --> 00:23:47.770 factors of delta H and entropy and when you'd have favorable 00:23:47.770 --> 00:23:48.730 delta G's. 00:23:48.730 --> 00:23:50.560 Here's another nice example where 00:23:50.560 --> 00:23:54.700 the chelate effect explains why metal chelates are so unusually 00:23:54.700 --> 00:23:56.200 stable. 00:23:56.200 --> 00:23:57.070 All right. 00:23:57.070 --> 00:23:58.690 So uses of EDTA. 00:23:58.690 --> 00:24:01.300 I already just told you one. 00:24:01.300 --> 00:24:05.860 Lead poisoning-- all ambulances have EDTA in case someone 00:24:05.860 --> 00:24:08.910 is eating some lead paint. 00:24:08.910 --> 00:24:12.820 Another thing that EDTA is used for, which I think is fun, 00:24:12.820 --> 00:24:16.030 you should all go check if you buy little packaged goods, 00:24:16.030 --> 00:24:18.460 and they have a long list of chemical ingredients. 00:24:18.460 --> 00:24:19.600 Look for EDTA. 00:24:19.600 --> 00:24:20.680 It's often there. 00:24:20.680 --> 00:24:24.790 And it says it's "added for freshness," which means 00:24:24.790 --> 00:24:27.120 that bacteria need metals. 00:24:27.120 --> 00:24:28.840 You have EDTA. 00:24:28.840 --> 00:24:30.600 EDTA sequesters the metals. 00:24:30.600 --> 00:24:33.850 The bacteria can't live on the food that you're eating. 00:24:33.850 --> 00:24:36.660 So instead of saying, food additive 00:24:36.660 --> 00:24:39.870 added to kill the bacteria that were otherwise growing 00:24:39.870 --> 00:24:42.220 on your food, they say added for freshness. 00:24:42.220 --> 00:24:44.240 And I do think that is an improvement. 00:24:44.240 --> 00:24:44.740 All right. 00:24:44.740 --> 00:24:47.230 Another thing, we've already talked about the importance 00:24:47.230 --> 00:24:49.300 of cleaning bathtubs. 00:24:49.300 --> 00:24:52.650 To chelate calcium out of bathtub scum, 00:24:52.650 --> 00:24:55.650 you have EDTA or other metal chelates. 00:24:55.650 --> 00:25:00.040 And then I have my favorite other example 00:25:00.040 --> 00:25:02.950 of the use of EDTA. 00:25:02.950 --> 00:25:09.730 This favorite example is in Hollywood, the movie Blade. 00:25:09.730 --> 00:25:11.830 How do you kill a vampire? 00:25:11.830 --> 00:25:14.033 Vampires drink what? 00:25:14.033 --> 00:25:14.840 AUDIENCE: Blood. 00:25:14.840 --> 00:25:15.881 CATHERINE DRENNAN: Blood. 00:25:15.881 --> 00:25:16.660 Blood has? 00:25:16.660 --> 00:25:17.530 AUDIENCE: Iron. 00:25:17.530 --> 00:25:19.000 CATHERINE DRENNAN: Iron. 00:25:19.000 --> 00:25:20.740 EDTA chelates? 00:25:20.740 --> 00:25:21.630 AUDIENCE: Iron. 00:25:21.630 --> 00:25:22.950 CATHERINE DRENNAN: Iron. 00:25:22.950 --> 00:25:25.330 So you get a little dart, and you 00:25:25.330 --> 00:25:27.940 have-- you can kind of see them maybe up here-- they're 00:25:27.940 --> 00:25:29.830 filled with liquid. 00:25:29.830 --> 00:25:31.750 That's EDTA. 00:25:31.750 --> 00:25:37.030 You shoot the vampire with EDTA, and the vampire just 00:25:37.030 --> 00:25:39.635 disappears, just kind of turns to sort of dust. 00:25:39.635 --> 00:25:41.050 [LAUGHTER] 00:25:41.050 --> 00:25:43.720 Because it's like mostly iron, and the iron gets chelated. 00:25:43.720 --> 00:25:45.267 But it happens right away. 00:25:45.267 --> 00:25:46.600 But anyway, I think that's cool. 00:25:46.600 --> 00:25:49.540 Yes, what a good way to kill a vampire. 00:25:49.540 --> 00:25:51.310 EDTA, it's brilliant. 00:25:51.310 --> 00:25:55.450 Excellent use on Hollywood's part for EDTA. 00:25:55.450 --> 00:25:55.950 OK. 00:25:55.950 --> 00:25:59.740 Metal chelates, all sorts of potential values 00:25:59.740 --> 00:26:01.300 that they have. 00:26:01.300 --> 00:26:03.220 OK. 00:26:03.220 --> 00:26:06.220 So when we're talking about coordination complexes, 00:26:06.220 --> 00:26:09.320 we're talking about geometries. 00:26:09.320 --> 00:26:14.260 Sometimes the atoms can be arranged in different ways. 00:26:14.260 --> 00:26:18.450 And when you have these geometric isomers, 00:26:18.450 --> 00:26:20.490 they can have very different properties. 00:26:20.490 --> 00:26:23.560 So just look at an example here. 00:26:23.560 --> 00:26:26.340 It's a platinum compound, a platinum compound 00:26:26.340 --> 00:26:30.600 who has two NH2 groups and two chlorine groups. 00:26:30.600 --> 00:26:33.880 And you could arrange those in two different ways. 00:26:33.880 --> 00:26:37.470 You could put the NH3 groups on one side and the chlorine 00:26:37.470 --> 00:26:40.230 groups on the other side, and that would be cis. 00:26:40.230 --> 00:26:42.520 These are cis to each other. 00:26:42.520 --> 00:26:45.210 Or you could put a transconfiguration, where 00:26:45.210 --> 00:26:47.430 chlorine is here, and then another chlorine 00:26:47.430 --> 00:26:50.070 is trans on the other side. 00:26:50.070 --> 00:26:52.080 And the same with this. 00:26:52.080 --> 00:26:56.340 So cisplatinum here is a potent anti-cancer drug. 00:26:56.340 --> 00:27:01.860 And it has to be cisplatinum because it binds to DNA, 00:27:01.860 --> 00:27:05.800 and the two bases of DNA displace these chlorines. 00:27:05.800 --> 00:27:08.790 So if they're not on the same side, it can't bind to the DNA. 00:27:08.790 --> 00:27:12.840 And so this prevents the cancer cells 00:27:12.840 --> 00:27:15.330 from being repaired from damaging agents. 00:27:15.330 --> 00:27:18.670 Transplatinum does absolutely nothing that anyone knows. 00:27:18.670 --> 00:27:22.020 So it's exactly the same composition, 00:27:22.020 --> 00:27:26.370 but because they are different isomers from each other-- 00:27:26.370 --> 00:27:31.830 and I have, let's see, ah, over here-- different isomers 00:27:31.830 --> 00:27:35.460 of each other-- and so chlorines on the same side, 00:27:35.460 --> 00:27:38.880 cis versus the trans-- have completely different 00:27:38.880 --> 00:27:40.150 properties. 00:27:40.150 --> 00:27:43.440 So cisplatinum got a lot of fame because it cured 00:27:43.440 --> 00:27:45.450 Lance Armstrong of cancer. 00:27:45.450 --> 00:27:48.390 Lance Armstrong now, of course, is a much more controversial 00:27:48.390 --> 00:27:50.880 figure than he was at the time. 00:27:50.880 --> 00:27:53.580 But still he created an amazing charity 00:27:53.580 --> 00:27:57.840 that hopefully is still doing well despite some of his fall 00:27:57.840 --> 00:27:59.280 from fame. 00:27:59.280 --> 00:27:59.970 OK. 00:27:59.970 --> 00:28:04.470 So another type of isomer are called 00:28:04.470 --> 00:28:09.300 optical isomers, also called enantiomers or chiral 00:28:09.300 --> 00:28:10.800 molecules. 00:28:10.800 --> 00:28:14.690 And these are one, again, you have the same composition, 00:28:14.690 --> 00:28:17.520 but they are non-superimposable. 00:28:17.520 --> 00:28:20.080 They are, in fact, mirror images of each other. 00:28:20.080 --> 00:28:22.020 So if my head was a mirror, these 00:28:22.020 --> 00:28:24.460 would be mirror images of each other. 00:28:24.460 --> 00:28:27.810 And I could try very hard to superimpose them, 00:28:27.810 --> 00:28:30.180 bringing the blue molecules over here, 00:28:30.180 --> 00:28:32.820 but then the green and the red don't match. 00:28:32.820 --> 00:28:34.230 You can come and try. 00:28:34.230 --> 00:28:37.170 These are, in fact, non-superimposable mirror 00:28:37.170 --> 00:28:38.910 images from each other. 00:28:38.910 --> 00:28:42.540 And sometimes they can have very similar properties. 00:28:42.540 --> 00:28:43.200 It depends. 00:28:43.200 --> 00:28:45.450 But if you put molecules like that that 00:28:45.450 --> 00:28:48.680 are known as chiral, chiral molecules, 00:28:48.680 --> 00:28:51.630 i.e. enantiomers-- non-superimposable mirror 00:28:51.630 --> 00:28:52.840 images. 00:28:52.840 --> 00:28:55.170 The human body is very much of a chiral environment. 00:28:55.170 --> 00:28:57.180 You have enzymes designed to bind things 00:28:57.180 --> 00:28:58.920 in a particular way. 00:28:58.920 --> 00:29:01.950 So they can have very, very different properties. 00:29:01.950 --> 00:29:02.610 OK. 00:29:02.610 --> 00:29:08.950 So we have to do some d-electron counting before we end today. 00:29:08.950 --> 00:29:13.020 And I love this because it's really pretty simple 00:29:13.020 --> 00:29:14.940 to count d-electrons. 00:29:14.940 --> 00:29:18.390 And so we're going to just take a look at some examples. 00:29:18.390 --> 00:29:20.640 And for doing this part, we're going 00:29:20.640 --> 00:29:26.430 to start using our friend the periodic table again. 00:29:26.430 --> 00:29:30.510 And we need to find oxidation numbers, which we just 00:29:30.510 --> 00:29:33.540 talked about in the last unit. 00:29:33.540 --> 00:29:37.050 So if we have a coordination complex with cobalt, 00:29:37.050 --> 00:29:44.580 and this cobalt has those six NH3 groups and our plus 3 00:29:44.580 --> 00:29:47.550 charge-- so this is the complex that we have been talking 00:29:47.550 --> 00:29:51.660 about-- let's now figure out what the oxidation 00:29:51.660 --> 00:29:53.550 number of this is. 00:29:53.550 --> 00:29:59.490 And so this NH3 is neutral, so that's given as a hint. 00:29:59.490 --> 00:30:04.350 Many of our ligands are going to be neutral ligands. 00:30:04.350 --> 00:30:09.000 So if that is 0, what is the charge on the cobalt? 00:30:09.000 --> 00:30:10.350 AUDIENCE: Plus 3. 00:30:10.350 --> 00:30:12.240 CATHERINE DRENNAN: Plus 3. 00:30:12.240 --> 00:30:17.370 Now we're going to use the rules of d-count. 00:30:17.370 --> 00:30:19.560 So we have a d-count. 00:30:19.560 --> 00:30:25.060 We need to look up the group number from the periodic table, 00:30:25.060 --> 00:30:27.660 which, in this case, is 9. 00:30:27.660 --> 00:30:34.770 Then we have minus the oxidation number, so we have 9 minus 3, 00:30:34.770 --> 00:30:36.120 or 6. 00:30:36.120 --> 00:30:39.900 And so this is a d6 system. 00:30:39.900 --> 00:30:44.280 And that is all there is to doing these counts. 00:30:44.280 --> 00:30:47.640 So let's just try another one. 00:30:47.640 --> 00:30:49.620 So we heard about nickel. 00:30:49.620 --> 00:30:51.530 We'll do nickel. 00:30:51.530 --> 00:30:56.130 Nickel is coordinated by carbon monoxide, 00:30:56.130 --> 00:31:00.150 and there are four of those. 00:31:00.150 --> 00:31:04.140 So what is my charge on the nickel going to be, 00:31:04.140 --> 00:31:06.420 my oxidation number of the nickel? 00:31:06.420 --> 00:31:09.156 So what's my overall charge of this complex? 00:31:09.156 --> 00:31:09.870 AUDIENCE: 0. 00:31:09.870 --> 00:31:11.700 CATHERINE DRENNAN: 0. 00:31:11.700 --> 00:31:15.300 CO is also going to be 0. 00:31:15.300 --> 00:31:17.310 There's no charge on CO. 00:31:17.310 --> 00:31:20.230 So what is the oxidation number of nickel? 00:31:20.230 --> 00:31:20.730 AUDIENCE: 0. 00:31:20.730 --> 00:31:22.680 CATHERINE DRENNAN: 0. 00:31:22.680 --> 00:31:26.212 So then we can do our d-count. 00:31:26.212 --> 00:31:30.316 The d-count, what is the group number for nickel? 00:31:30.316 --> 00:31:31.250 AUDIENCE: 10. 00:31:31.250 --> 00:31:31.920 CATHERINE DRENNAN: What is it? 00:31:31.920 --> 00:31:32.461 AUDIENCE: 10. 00:31:32.461 --> 00:31:34.770 CATHERINE DRENNAN: 10. 00:31:34.770 --> 00:31:37.680 This is the kind of math that always makes me very happy. 00:31:37.680 --> 00:31:41.540 10 minus 0 is 10. 00:31:41.540 --> 00:31:46.621 So that is a d10 system. 00:31:46.621 --> 00:31:47.120 All right. 00:31:47.120 --> 00:31:48.286 We'll do one more over here. 00:31:48.286 --> 00:31:50.350 And the next one is a clicker question. 00:32:01.080 --> 00:32:24.837 Gives me time to write 00:32:24.837 --> 00:32:26.170 AUDIENCE: Whenever you're ready. 00:32:26.170 --> 00:32:27.120 We're out of time. 00:32:27.120 --> 00:32:27.600 CATHERINE DRENNAN: Yep. 00:32:27.600 --> 00:32:28.150 All right. 00:32:28.150 --> 00:32:29.730 Let's just do 10 more seconds. 00:32:43.760 --> 00:32:45.360 Yep. 00:32:45.360 --> 00:32:49.620 So here our overall charge is minus 1. 00:32:49.620 --> 00:32:54.310 We have the chlorines are minus 1. 00:32:54.310 --> 00:32:56.220 NH3 is 0. 00:32:56.220 --> 00:32:58.560 Water is 0. 00:32:58.560 --> 00:33:05.040 So this has to be plus 2 because plus 2 minus 3 is minus 1. 00:33:05.040 --> 00:33:14.120 We have 9 minus 2 is 7, so it's a d7 system. 00:33:14.120 --> 00:33:14.850 All right. 00:33:14.850 --> 00:33:18.510 So Wednesday, d orbitals. 00:33:18.510 --> 00:33:20.260 I cannot wait. 00:33:31.070 --> 00:33:32.060 Yes. 00:33:32.060 --> 00:33:33.040 All right, 10 seconds. 00:33:50.930 --> 00:33:51.500 OK. 00:33:51.500 --> 00:33:56.153 Does someone want to tell me why that's the right answer? 00:34:02.225 --> 00:34:02.725 Anybody? 00:34:07.570 --> 00:34:13.121 We got a nice dangly thing for your keys or ID. 00:34:13.121 --> 00:34:13.621 No? 00:34:16.513 --> 00:34:19.600 All right. 00:34:19.600 --> 00:34:22.000 So here we're thinking about whether things are better 00:34:22.000 --> 00:34:25.780 reducing agents or better oxidizing agents. 00:34:25.780 --> 00:34:29.960 And here we're given two different redox potentials-- 00:34:29.960 --> 00:34:33.460 minus 600 and minus 300. 00:34:33.460 --> 00:34:38.620 So the one that is going to be the lower number 00:34:38.620 --> 00:34:41.780 is going to be better at reducing other things. 00:34:41.780 --> 00:34:45.340 It wants to be oxidized itself. 00:34:45.340 --> 00:34:48.159 And then we can think about whether it's 00:34:48.159 --> 00:34:53.320 a favorable process in terms of whether the thing that 00:34:53.320 --> 00:34:56.469 likes to reduce is actually doing the reducing. 00:34:56.469 --> 00:34:59.271 That's going to make it a spontaneous process. 00:34:59.271 --> 00:34:59.770 All right. 00:34:59.770 --> 00:35:03.070 So these are the kinds of questions 00:35:03.070 --> 00:35:06.550 for the oxidation-reduction unit that we just finished. 00:35:06.550 --> 00:35:10.660 And this will be on exam 4, which, amazingly, we just 00:35:10.660 --> 00:35:13.150 finished an exam, and there's another one. 00:35:13.150 --> 00:35:17.790 So exam 4 is two weeks from today. 00:35:17.790 --> 00:35:18.880 All right. 00:35:18.880 --> 00:35:21.440 From Friday, sorry, two weeks from Friday. 00:35:21.440 --> 00:35:21.940 All right. 00:35:21.940 --> 00:35:24.640 So today we're going to continue with this unit on transition 00:35:24.640 --> 00:35:25.240 metals. 00:35:25.240 --> 00:35:27.970 The next exam is going to have oxidation-reduction 00:35:27.970 --> 00:35:30.280 and transition metals and a little bit of kinetics. 00:35:30.280 --> 00:35:31.454 Kinetics is our last unit. 00:35:31.454 --> 00:35:33.745 So we're getting very close to the end of the semester. 00:35:36.380 --> 00:35:38.860 So we're finishing up the handout from last time. 00:35:38.860 --> 00:35:41.180 Again, we're back to the periodic table. 00:35:41.180 --> 00:35:43.000 We're thinking about transition metals. 00:35:43.000 --> 00:35:46.660 We're thinking about that middle part of the periodic table, 00:35:46.660 --> 00:35:48.505 and so we're thinking about d orbitals. 00:35:52.140 --> 00:35:54.990 So there are five d orbitals. 00:35:54.990 --> 00:35:58.317 How many s orbitals are there? 00:35:58.317 --> 00:35:58.900 AUDIENCE: One. 00:35:58.900 --> 00:35:59.858 CATHERINE DRENNAN: One. 00:35:59.858 --> 00:36:01.140 How many p orbitals are there? 00:36:01.140 --> 00:36:01.680 AUDIENCE: Three. 00:36:01.680 --> 00:36:02.721 CATHERINE DRENNAN: Three. 00:36:02.721 --> 00:36:04.649 And so d orbitals have five. 00:36:04.649 --> 00:36:06.690 And we're not going to talk about really anything 00:36:06.690 --> 00:36:08.340 beyond d orbitals in this class. 00:36:08.340 --> 00:36:10.740 And frankly, not very many people do. 00:36:10.740 --> 00:36:13.300 But d orbitals are amazing, so we have to fit them in. 00:36:13.300 --> 00:36:13.800 All right. 00:36:13.800 --> 00:36:15.870 So there are five d orbitals. 00:36:15.870 --> 00:36:18.630 And they're up here, and you need 00:36:18.630 --> 00:36:20.820 to be able to draw their shapes. 00:36:20.820 --> 00:36:25.420 And the bar for drawing the shapes is actually pretty low. 00:36:25.420 --> 00:36:28.900 So these are my drawings that I made. 00:36:28.900 --> 00:36:32.351 And so you can probably do just about as well. 00:36:32.351 --> 00:36:32.850 All right. 00:36:32.850 --> 00:36:36.930 So the one that has the most unusual shape 00:36:36.930 --> 00:36:40.590 is the dz squared. 00:36:40.590 --> 00:36:44.740 And so it has its maximum amplitude along the z-axis. 00:36:44.740 --> 00:36:46.980 And for this unit, our z-axis is always 00:36:46.980 --> 00:36:49.080 going to be up and down here. 00:36:49.080 --> 00:36:53.790 y is in the plane of the screen, and x is coming out toward you 00:36:53.790 --> 00:36:55.560 and also going into the screen. 00:36:55.560 --> 00:37:00.300 And so dz squared has its maximum amplitude along z, 00:37:00.300 --> 00:37:05.610 and it also has a doughnut in the xy-plane. 00:37:05.610 --> 00:37:09.180 And so I also brought a little model of this. 00:37:09.180 --> 00:37:11.310 So here's dz squared. 00:37:11.310 --> 00:37:16.540 We have maximum amplitude along the z-axis, up and down. 00:37:16.540 --> 00:37:22.050 And we have our little doughnut in our xy-plane. 00:37:22.050 --> 00:37:25.950 So then we have dx squared minus y squared, which 00:37:25.950 --> 00:37:31.590 has maximum amplitude along x and along y. 00:37:31.590 --> 00:37:35.100 And that would look like this. 00:37:35.100 --> 00:37:37.620 So we have our maximum amplitudes 00:37:37.620 --> 00:37:39.340 that are right on axis. 00:37:39.340 --> 00:37:43.530 So if this is y-axis and x is coming out toward you, 00:37:43.530 --> 00:37:46.680 those orbitals are pointing right along 00:37:46.680 --> 00:37:49.320 that coordinate frame. 00:37:49.320 --> 00:37:52.020 The other three orbitals look a little bit 00:37:52.020 --> 00:37:57.120 like dx squared minus y squared, but they're not on-axis. 00:37:57.120 --> 00:37:58.170 They're off-axis. 00:37:58.170 --> 00:38:00.570 They're in between the axes. 00:38:00.570 --> 00:38:03.120 So we have dyz. 00:38:03.120 --> 00:38:07.740 It has its maximum amplitude 45 degrees off 00:38:07.740 --> 00:38:11.650 of the y and the z-axis. 00:38:11.650 --> 00:38:14.490 So if this is z-axis here, there's 00:38:14.490 --> 00:38:16.840 no maximum amplitude along here. 00:38:16.840 --> 00:38:18.300 It's 45 degrees off. 00:38:18.300 --> 00:38:24.540 So it's right in the middle between the z and the y. 00:38:24.540 --> 00:38:33.870 So dxz has its maximum amplitude 45 degrees between x and z. 00:38:33.870 --> 00:38:37.110 So that would be pointing the other way. 00:38:37.110 --> 00:38:39.990 And so I tried to draw this keeping 00:38:39.990 --> 00:38:42.330 the reference frame the same. 00:38:42.330 --> 00:38:44.040 It's a little hard to see the orbitals, 00:38:44.040 --> 00:38:45.570 but it would be kind of this. 00:38:45.570 --> 00:38:48.690 So we rotate that around, and so that's 00:38:48.690 --> 00:38:50.220 what that would look like. 00:38:50.220 --> 00:38:56.340 And then dxy we have maximum amplitude 45 degrees in 00:38:56.340 --> 00:38:59.880 between the x and the y. 00:38:59.880 --> 00:39:02.790 So x coming out, y in the plane. 00:39:02.790 --> 00:39:05.100 And so this is, again, a little bit hard to draw. 00:39:05.100 --> 00:39:07.530 If I drew it absolutely perfectly and not tilted 00:39:07.530 --> 00:39:09.630 at all, you kind of wouldn't see anything. 00:39:09.630 --> 00:39:12.130 But that's what that would look like. 00:39:12.130 --> 00:39:14.130 So again, the names of this, it tells you 00:39:14.130 --> 00:39:17.910 about the relationship between that orbital, 00:39:17.910 --> 00:39:23.730 that maximum amplitude, and the axis that we have defined. 00:39:23.730 --> 00:39:27.510 So this is very important to know 00:39:27.510 --> 00:39:30.660 that these guys are in between the axes, right 00:39:30.660 --> 00:39:32.430 in the middle, 45 degrees. 00:39:32.430 --> 00:39:36.150 And you'll see why in a few minutes why that's important. 00:39:36.150 --> 00:39:36.840 OK. 00:39:36.840 --> 00:39:41.670 So just to practice, here are some slightly better pictures 00:39:41.670 --> 00:39:42.960 of the orbitals. 00:39:42.960 --> 00:39:48.010 And this is the coordinate frame over here, 00:39:48.010 --> 00:39:50.800 and now we have the orbitals inside that. 00:39:50.800 --> 00:39:55.680 So again, z is going up, y is in the plane of the screen, 00:39:55.680 --> 00:39:58.860 and x is going back and also coming out toward us. 00:39:58.860 --> 00:40:01.540 So which is this d orbital? 00:40:01.540 --> 00:40:03.006 You can just yell it out. 00:40:03.006 --> 00:40:03.880 AUDIENCE: dz squared. 00:40:03.880 --> 00:40:04.796 CATHERINE DRENNAN: dz. 00:40:04.796 --> 00:40:06.360 Yeah, that's easy to remember. 00:40:06.360 --> 00:40:09.120 That's the unique-looking one. 00:40:09.120 --> 00:40:11.430 What about this one? 00:40:11.430 --> 00:40:13.110 First think about the plane. 00:40:13.110 --> 00:40:15.300 So it's the xy-plane. 00:40:15.300 --> 00:40:17.160 And then, is it on or off-axis? 00:40:17.160 --> 00:40:18.166 So which one is this? 00:40:18.166 --> 00:40:19.311 AUDIENCE: [INAUDIBLE] 00:40:19.311 --> 00:40:20.310 CATHERINE DRENNAN: Yeah. 00:40:20.310 --> 00:40:21.750 So this one is on-axis. 00:40:21.750 --> 00:40:23.940 You can see the maximum amplitude 00:40:23.940 --> 00:40:26.810 of the orbital pointing right along those axes. 00:40:26.810 --> 00:40:31.170 So it's right in the corners of that square there. 00:40:31.170 --> 00:40:33.515 And then what about this one down here? 00:40:33.515 --> 00:40:34.390 AUDIENCE: [INAUDIBLE] 00:40:34.390 --> 00:40:35.550 CATHERINE DRENNAN: Yep. 00:40:35.550 --> 00:40:37.230 So that would be dxy. 00:40:37.230 --> 00:40:41.605 So it's in the xy-plane, but it's 45 degrees off the axes. 00:40:41.605 --> 00:40:44.730 So it's in between the axes here. 00:40:44.730 --> 00:40:46.222 And what about that one? 00:40:46.222 --> 00:40:47.699 AUDIENCE: . 00:40:47.699 --> 00:40:48.740 CATHERINE DRENNAN: Right. 00:40:48.740 --> 00:40:55.260 So it's along both z and y here. 00:40:55.260 --> 00:40:57.240 And then this last one, which is drawn 00:40:57.240 --> 00:41:01.770 to kind of come out toward you, so that is along x as well. 00:41:01.770 --> 00:41:05.754 So that's dxz, and it's going up along z. 00:41:05.754 --> 00:41:07.920 So you can look at the coordinate frame, which we'll 00:41:07.920 --> 00:41:11.610 try to keep consistent, and ask yourself, 00:41:11.610 --> 00:41:14.700 is it on-axis or off-axis, and which plane is it in? 00:41:14.700 --> 00:41:19.230 And that will allow you to name them and also to draw them. 00:41:19.230 --> 00:41:23.180 So just to kind of give you more of a three-dimensional sense, 00:41:23.180 --> 00:41:26.420 there's these little movies that I'll show you now. 00:41:26.420 --> 00:41:29.581 And so you can get a better sense of that awesome doughnut. 00:41:29.581 --> 00:41:30.830 It's going to make you hungry. 00:41:30.830 --> 00:41:34.410 They even colored it like a really nice original doughnut 00:41:34.410 --> 00:41:36.090 that you would get at Dunkin' Donuts. 00:41:36.090 --> 00:41:42.240 So the doughnut is in the xy-plane, 00:41:42.240 --> 00:41:47.220 and these other lobes are along z. 00:41:47.220 --> 00:41:51.570 So now we have dx squared minus y squared, 00:41:51.570 --> 00:41:54.900 and you can see that the maximum amplitudes, again, 00:41:54.900 --> 00:41:56.350 are along the axes. 00:41:56.350 --> 00:41:59.910 Key-- they're along the axes here. 00:41:59.910 --> 00:42:01.650 I don't know why it comes out towards you 00:42:01.650 --> 00:42:03.720 and-- I didn't, yeah. 00:42:03.720 --> 00:42:06.810 But it gives you a good three-dimensional sense 00:42:06.810 --> 00:42:07.991 of this. 00:42:07.991 --> 00:42:08.490 All right. 00:42:08.490 --> 00:42:13.470 So dxy now, again, in the xy-plane. 00:42:13.470 --> 00:42:16.920 But instead of being on-axis, it's 45 degrees off-axis. 00:42:16.920 --> 00:42:19.750 So you can see, I think, in this really nicely, 00:42:19.750 --> 00:42:23.610 it's right between the axes, but it's not touching them. 00:42:23.610 --> 00:42:26.232 The axes sort of separate these orbitals. 00:42:28.830 --> 00:42:33.000 And then we have xz. 00:42:33.000 --> 00:42:37.380 So now we're going up along the z-axis and in the x-plane. 00:42:37.380 --> 00:42:44.730 And here it comes at you again, 45 degrees in between z and x. 00:42:44.730 --> 00:42:51.850 And then our last one, we have yz. 00:42:54.380 --> 00:42:57.230 So the shapes of those later three, 00:42:57.230 --> 00:42:59.780 actually even four of them, are the same. 00:42:59.780 --> 00:43:01.910 It's just a matter if they're on or off-axis 00:43:01.910 --> 00:43:03.620 and which plane they're in. 00:43:03.620 --> 00:43:06.211 So this is not too hard to draw. 00:43:06.211 --> 00:43:06.710 All right. 00:43:06.710 --> 00:43:08.460 So why is this important? 00:43:08.460 --> 00:43:13.220 Why should we care exactly how the orbitals are oriented? 00:43:13.220 --> 00:43:15.860 And the reason that you should care about that 00:43:15.860 --> 00:43:19.550 is because it can explain a lot of the special properties 00:43:19.550 --> 00:43:21.760 of transition metals.