WEBVTT 00:00:00.000 --> 00:00:04.360 Welcome back to another deep dive. Today, I want 00:00:04.360 --> 00:00:06.960 to start with a deception. Oh, a massive deception. 00:00:07.200 --> 00:00:08.820 Yeah. I was looking through the files for this 00:00:08.820 --> 00:00:11.939 week, and I saw this name. Gallium Monoi died. 00:00:12.820 --> 00:00:16.050 And my brain immediately went, OK. Simple. Right. 00:00:16.089 --> 00:00:17.929 It sounds incredibly straightforward, doesn't 00:00:17.929 --> 00:00:19.989 it? Exactly. You picture the periodic table. 00:00:20.089 --> 00:00:23.109 You take one atom of gallium, one atom of iodine. 00:00:23.210 --> 00:00:26.250 You stick them together. Done. A nice, clean 00:00:26.250 --> 00:00:28.129 one -to -one relationship. That's what you would 00:00:28.129 --> 00:00:29.690 think. But then I started reading the actual 00:00:29.690 --> 00:00:33.869 research, and well, it's a lie. It is a total 00:00:33.869 --> 00:00:37.090 lie. If you walked into a lab expecting a simple 00:00:37.090 --> 00:00:39.829 one -to -one molecule, you would be completely 00:00:39.829 --> 00:00:42.700 unprepared for what's actually in that jar. This 00:00:42.700 --> 00:00:45.799 isn't some polite chemical compound. It's chaotic, 00:00:46.119 --> 00:00:48.299 it's confusing, and quite frankly, it's a bit 00:00:48.299 --> 00:00:50.359 of a shapeshifter. That's the exact vibe I got. 00:00:50.420 --> 00:00:52.200 We aren't talking about table cell here. For 00:00:52.200 --> 00:00:54.060 those of you listening, we are talking about 00:00:54.060 --> 00:00:56.859 a pale green powder that has a serious identity 00:00:56.859 --> 00:00:59.539 crisis. It doesn't even seem to know what charge 00:00:59.539 --> 00:01:02.020 it wants to be. No, it really doesn't. And it's 00:01:02.020 --> 00:01:04.739 synthesized by literally screaming at liquid 00:01:04.739 --> 00:01:07.700 metal. Plus, it turns out the version of this 00:01:07.700 --> 00:01:10.260 stuff that chemists used for 20 years was actually 00:01:10.260 --> 00:01:12.599 a mistake. A mistake that ended up unlocking 00:01:12.599 --> 00:01:15.480 entire new fields of inorganic chemistry, though. 00:01:15.780 --> 00:01:18.140 Right. So that is our mission today. We're going 00:01:18.140 --> 00:01:21.640 to unpack the wild story of gallium monoidide. 00:01:22.239 --> 00:01:24.640 We're going to look at how a messy, incomplete 00:01:24.640 --> 00:01:27.420 reaction turned out to be this master key for 00:01:27.420 --> 00:01:29.920 everything from creating chemical sandwiches 00:01:29.920 --> 00:01:33.340 to Uh, bonding with gold. And honestly, I think 00:01:33.340 --> 00:01:35.700 it's a great lesson for everyone and why perfect 00:01:35.700 --> 00:01:38.200 science isn't always the best science. Let's 00:01:38.200 --> 00:01:40.500 start with that identity crisis. The empirical 00:01:40.500 --> 00:01:43.099 formula on paper is Ji, sometimes written as 00:01:43.099 --> 00:01:45.700 J4I4. Yeah. But you're telling me that if I zoom 00:01:45.700 --> 00:01:48.079 in on this powder, I'm not seeing GaRi molecules 00:01:48.079 --> 00:01:50.200 lined up like soldiers. Not even close. If you 00:01:50.200 --> 00:01:52.120 could shrink down and walk through that pale 00:01:52.120 --> 00:01:54.239 green powder, you'd basically be walking through 00:01:54.239 --> 00:01:57.000 a mosh pit. It's a mix, a complete chemical suit. 00:01:57.200 --> 00:01:59.959 A mosh pit, I love that. Yeah, you have gallium 00:01:59.959 --> 00:02:02.459 atoms that have lost electrons standing right 00:02:02.459 --> 00:02:04.799 next to neutral gallium metal that hasn't reacted 00:02:04.799 --> 00:02:07.700 at all. And then there are these big complex 00:02:07.700 --> 00:02:11.139 clusters of gallium and iodine all tangled together. 00:02:11.319 --> 00:02:14.400 So it's not uniform at all? No. We call it mixed 00:02:14.400 --> 00:02:17.599 valent. Usually in a standard salt, the metal 00:02:17.599 --> 00:02:19.599 picks a lane, right? It's plus one or it's plus 00:02:19.599 --> 00:02:22.460 two. Here, gallium is doing everything it wants. 00:02:22.879 --> 00:02:25.650 You've got oxidation states of zero, plus one, 00:02:25.710 --> 00:02:27.930 plus two, and plus three, all just hanging out 00:02:27.930 --> 00:02:31.550 in the same solid. It's juggling electrons. Precisely. 00:02:31.909 --> 00:02:34.169 And that juggling act is exactly what makes it 00:02:34.169 --> 00:02:37.009 so reactive. It's inherently unstable. It desperately 00:02:37.009 --> 00:02:38.990 wants to do something. And it's high maintenance, 00:02:38.990 --> 00:02:41.150 apparently. The notes say you can't just leave 00:02:41.150 --> 00:02:43.110 this stuff sitting out on the counter. Oh, absolutely 00:02:43.110 --> 00:02:45.750 not. It hates moisture. It completely hates air. 00:02:46.050 --> 00:02:48.169 You have to keep it in a glove box under an inert 00:02:48.169 --> 00:02:50.810 gas. Wow. And even then, if you want it to last 00:02:50.810 --> 00:02:53.750 more than a few months, say up to a year, You're 00:02:53.750 --> 00:02:56.610 storing it in a freezer at negative 35 degrees 00:02:56.610 --> 00:02:59.750 Celsius. It's a very fragile chaos. I want to 00:02:59.750 --> 00:03:02.110 talk about how this chaos is actually made, because 00:03:02.110 --> 00:03:04.990 the origin story is fantastic. This goes back 00:03:04.990 --> 00:03:08.530 to 1990 and a chemist named Malcolm Green, and 00:03:08.530 --> 00:03:11.629 the method is called ultrasonication, which sounds 00:03:11.629 --> 00:03:14.569 like a superhero power. The Green Synthesis. 00:03:15.189 --> 00:03:17.569 It completely changed the game. Before this, 00:03:17.610 --> 00:03:20.129 trying to get gallium into these low oxidation 00:03:20.129 --> 00:03:22.789 states was an absolute Nightmare. We're talking 00:03:22.789 --> 00:03:25.650 high temperatures, dangerous chemicals. But Green 00:03:25.650 --> 00:03:27.969 had a completely different idea. He took liquid 00:03:27.969 --> 00:03:29.849 gallium metal, which is already cool because 00:03:29.849 --> 00:03:32.729 it melts in your hand. Like the T1000 from Terminator? 00:03:32.969 --> 00:03:36.150 Yes. Exactly like the T1000. So he takes this 00:03:36.150 --> 00:03:39.250 liquid metal, mixes it with iodine in toluene, 00:03:39.349 --> 00:03:41.789 which is just a solvent, and then hits it with 00:03:41.789 --> 00:03:43.650 ultrasound waves. Intense sound waves. It's a 00:03:43.650 --> 00:03:45.870 process called acoustic cavitation. OK. What 00:03:45.870 --> 00:03:47.780 does that actually do? Well, the sound waves 00:03:47.780 --> 00:03:50.039 create these microscopic bubbles in the liquid 00:03:50.039 --> 00:03:53.120 that expand and then collapse incredibly violently. 00:03:53.800 --> 00:03:56.240 When they collapse, they generate massive amounts 00:03:56.240 --> 00:03:59.319 of localized heat and pressure. It basically 00:03:59.319 --> 00:04:01.659 shreds the metal surface and forces it to react 00:04:01.659 --> 00:04:03.659 with the iodine. So he just screamed at the metal 00:04:03.659 --> 00:04:06.060 until it turned into a green powder. In a manner 00:04:06.060 --> 00:04:08.379 of speaking, yeah, he did. But here is the twist, 00:04:08.439 --> 00:04:10.400 and this is the part that blows my mind. For 00:04:10.400 --> 00:04:13.699 over 20 years, people used this method. They 00:04:13.699 --> 00:04:16.279 made the green powder. They used it in reactions. 00:04:16.819 --> 00:04:19.420 But nobody really knew what it was. That is the 00:04:19.420 --> 00:04:22.819 big detective story here. From 1990 until around 00:04:22.819 --> 00:04:27.459 2012 or 2014, it was basically a black box. Right. 00:04:27.740 --> 00:04:30.540 Chemists knew, if you threw this gallium monoidide 00:04:30.540 --> 00:04:33.319 into a pot, it did really cool things. But they 00:04:33.319 --> 00:04:35.100 didn't have a clear picture of the molecular 00:04:35.100 --> 00:04:37.709 structure. And it turns out the confusion came 00:04:37.709 --> 00:04:40.050 from the cooking time. Right. It wasn't until 00:04:40.050 --> 00:04:42.089 fairly recently that scientists realized there 00:04:42.089 --> 00:04:44.029 were actually two different versions of the powder, 00:04:44.350 --> 00:04:46.870 depending on how long you blasted it. There was 00:04:46.870 --> 00:04:49.410 the incomplete reaction and the complete reaction. 00:04:49.670 --> 00:04:51.529 OK, so walk me through this. The incomplete one 00:04:51.529 --> 00:04:53.970 is the one everyone was using. Yes. If you stop 00:04:53.970 --> 00:04:56.009 the sonication early, you get that messy soup 00:04:56.009 --> 00:04:59.029 we talked about earlier. Structurally, it's two 00:04:59.029 --> 00:05:01.670 neutral gallium atoms, a gallium plus one cation, 00:05:01.930 --> 00:05:04.589 and a gallium iodine complex all mashed together. 00:05:05.079 --> 00:05:08.319 chunks of unreacted metal, some ions, it's chemically 00:05:08.319 --> 00:05:11.240 dirty. But if you leave the sound on for too 00:05:11.240 --> 00:05:14.100 long... If you leave the sonication on, or let 00:05:14.100 --> 00:05:16.740 it sit too long, it converts into something much 00:05:16.740 --> 00:05:20.040 more organized. The free metal disappears, and 00:05:20.040 --> 00:05:23.220 it forms a stable, boring crystal structure. 00:05:23.759 --> 00:05:25.680 A completely reacted mixture. And the boring 00:05:25.680 --> 00:05:27.740 one doesn't work as well. It works differently, 00:05:27.819 --> 00:05:30.720 but for the really exciting chemistry, no. The 00:05:30.720 --> 00:05:33.839 magic was entirely in the mess. That's fascinating. 00:05:34.120 --> 00:05:36.759 Yeah, the unreacted gallium metal in the incomplete 00:05:36.759 --> 00:05:39.660 version was actually crucial for driving a lot 00:05:39.660 --> 00:05:41.579 of the reactions people were discovering. That 00:05:41.579 --> 00:05:43.899 is profound. If they had done the experiment 00:05:43.899 --> 00:05:46.459 perfectly, if they had reacted at 100%, they 00:05:46.459 --> 00:05:48.779 would have missed the discovery entirely. Exactly. 00:05:49.319 --> 00:05:52.420 Laziness, or perhaps just impatience, was the 00:05:52.420 --> 00:05:55.139 secret ingredient. So we have this green powder. 00:05:55.480 --> 00:05:58.360 It's messy. It's weird. How do we even know all 00:05:58.360 --> 00:06:01.319 this? The notes mention Raman spectroscopy and 00:06:01.319 --> 00:06:04.100 NMR. Right, mCot or X -ray diffraction. That's 00:06:04.100 --> 00:06:06.819 how they finally cracked the case. By using these 00:06:06.819 --> 00:06:08.800 advanced characterization techniques, they could 00:06:08.800 --> 00:06:10.500 finally see the difference between the messy 00:06:10.500 --> 00:06:13.379 soup and the fully cooked boring crystal. So 00:06:13.379 --> 00:06:15.600 what do we actually do with the messy soup? Because 00:06:15.600 --> 00:06:17.720 you mentioned it's a shapeshifter. It acts as 00:06:17.720 --> 00:06:21.980 a gateway. Because it's so unstable, it is desperate 00:06:21.980 --> 00:06:24.279 to stabilize itself. It's always looking for 00:06:24.279 --> 00:06:26.959 partners. In chemistry terms, it behaves as a 00:06:26.959 --> 00:06:30.379 precursor, a Lewis acid, meaning it accepts electrons, 00:06:30.879 --> 00:06:33.000 and a reducing agent, meaning it gives them away. 00:06:33.079 --> 00:06:35.360 It's a giver and a taker. It's whatever this 00:06:35.360 --> 00:06:38.339 situation demands. And its favorite dance partners 00:06:38.339 --> 00:06:41.720 are things called Lewis bases. These are molecules 00:06:41.720 --> 00:06:43.959 with a pair of electrons just waiting to be shared. 00:06:44.329 --> 00:06:47.589 Things like phosphines, ethers, or amines. But 00:06:47.589 --> 00:06:49.269 it's not a gentle dance, right? I was reading 00:06:49.269 --> 00:06:51.850 about something called disproportionation, which 00:06:51.850 --> 00:06:54.250 sounds less like a dance and more like a messy 00:06:54.250 --> 00:06:56.089 divorce. That's actually a really good analogy. 00:06:56.290 --> 00:06:59.350 When gallium meets some of these bases, the gallium 00:06:59.350 --> 00:07:01.209 atoms look at each other and say, this isn't 00:07:01.209 --> 00:07:04.149 working. So they split. A chemical divorce. Right. 00:07:04.310 --> 00:07:06.230 Some of the gallium grabs all the electrons and 00:07:06.230 --> 00:07:09.029 turns back into a plain old neutral metal besage. 00:07:09.470 --> 00:07:11.769 It just precipitates right out of the solution. 00:07:12.370 --> 00:07:15.269 The other gallium atoms get oxidized. They lose 00:07:15.269 --> 00:07:17.550 electrons and form a higher charge complex with 00:07:17.550 --> 00:07:20.029 the base. So it sacrifices part of itself to 00:07:20.029 --> 00:07:22.790 upgrade the rest. Exactly. It sheds its skin. 00:07:23.149 --> 00:07:25.569 You see metal falling out of the solution. And 00:07:25.569 --> 00:07:29.129 what's left is a new stable molecule. There is 00:07:29.129 --> 00:07:31.089 a specific example of this in the notes that 00:07:31.089 --> 00:07:34.209 I loved, a showdown between phosphorus and antimony. 00:07:34.639 --> 00:07:37.319 I feel like antimony is the underdog of the periodic 00:07:37.319 --> 00:07:39.540 table. We never talk about it. Oh, it plays a 00:07:39.540 --> 00:07:41.980 starring role right here. This experiment perfectly 00:07:41.980 --> 00:07:45.220 highlights how aggressive Gaiai can be. So round 00:07:45.220 --> 00:07:48.879 one, triphenylphosphine. This is phosphorus connected 00:07:48.879 --> 00:07:52.220 to three carbon rings. Gaiai meets it. What happens? 00:07:52.800 --> 00:07:55.610 Nothing too dramatic. They shake hands. The phosphorus 00:07:55.610 --> 00:07:57.490 shares its electrons, and you get a standard 00:07:57.490 --> 00:08:00.449 gallium three complex. The gallium's happy. The 00:08:00.449 --> 00:08:02.550 phosphorus is happy. It's just a normal coordination 00:08:02.550 --> 00:08:05.389 complex. OK, round two. Swap the phosphorus for 00:08:05.389 --> 00:08:07.629 antimony, triphenylstabine. Antimony is just 00:08:07.629 --> 00:08:09.709 one step down on the periodic table. It should 00:08:09.709 --> 00:08:11.850 be similar, right? You would think so. But antimony 00:08:11.850 --> 00:08:14.970 is bigger, and it's softer. And its grip on those 00:08:14.970 --> 00:08:17.870 carbon rings is a lot weaker because the SBC 00:08:17.870 --> 00:08:21.069 bond isn't as strong as the PC bond. OK. So when 00:08:21.069 --> 00:08:23.819 Guy meets the antimony compound, It doesn't just 00:08:23.819 --> 00:08:25.980 want to hold hands. It turns into a thief. It 00:08:25.980 --> 00:08:28.600 steals the carbon rings. It effectively robs 00:08:28.600 --> 00:08:31.420 the antimony. The gallium acts as a powerful 00:08:31.420 --> 00:08:34.279 reducing agent, breaks the bond between the antimony 00:08:34.279 --> 00:08:36.080 and the carbon, and just takes a phenyl group 00:08:36.080 --> 00:08:39.279 for itself. That is wild. It went from a polite 00:08:39.279 --> 00:08:41.419 handshake to grand theft auto just because we 00:08:41.419 --> 00:08:43.779 moved one row down the periodic table. That's 00:08:43.779 --> 00:08:46.019 the power of the green powder. It can manipulate 00:08:46.019 --> 00:08:48.360 bonds that other compounds just can't touch. 00:08:48.570 --> 00:08:50.730 And we see this in the structural details, too. 00:08:50.950 --> 00:08:53.610 If you react it with bipyridine, you get a distorted 00:08:53.610 --> 00:08:56.090 octahedral geometry where the gallium -nitrogen 00:08:56.090 --> 00:09:00.289 bond is exactly 2 .063 angstroms. Very precise. 00:09:00.490 --> 00:09:03.269 But if you use phenylpyridine, it twists into 00:09:03.269 --> 00:09:06.990 a distorted trigonal bipyramidal shape. It constantly 00:09:06.990 --> 00:09:09.289 adapts its geometry based on what it's reacting 00:09:09.289 --> 00:09:12.090 with. Speaking of adapting and manipulating bonds, 00:09:12.149 --> 00:09:14.669 let's talk about the welder. The notes mention 00:09:14.669 --> 00:09:16.789 something called reductive coupling. Oh, this 00:09:16.789 --> 00:09:19.399 is a holy grail. type of reaction in chemistry. 00:09:19.759 --> 00:09:21.759 Because usually making carbon connect to another 00:09:21.759 --> 00:09:23.879 carbon is really hard, right? It's like the absolute 00:09:23.879 --> 00:09:26.220 foundation of organic synthesis, but it's not 00:09:26.220 --> 00:09:29.039 always easy. Here you take two separate molecules, 00:09:29.340 --> 00:09:31.799 specifically immunosubstituted pyridines, if 00:09:31.799 --> 00:09:34.620 you want the technical term. Got it. The gallium 00:09:34.620 --> 00:09:37.899 sits in the middle and literally welds them together. 00:09:38.320 --> 00:09:41.320 It acts as a reducing agent to form a brand new 00:09:41.320 --> 00:09:43.860 carbon -carbon bond between them. So it's not 00:09:43.860 --> 00:09:46.100 just reacting, it's building. Yes, it's acting 00:09:46.100 --> 00:09:49.139 as a template. It pulls the pieces together, 00:09:49.679 --> 00:09:51.559 facilitates the electron transfer to make the 00:09:51.559 --> 00:09:54.120 connection, and stabilizes the result. Okay, 00:09:54.179 --> 00:09:56.059 so it's a thief, it's a welder. Now I want to 00:09:56.059 --> 00:09:58.460 talk about how it plays dress up, because apparently 00:09:58.460 --> 00:10:02.259 Gallium Monoi died likes to hide inside rings. 00:10:02.480 --> 00:10:05.929 Ah! Gallium heterocycles. This is where we start 00:10:05.929 --> 00:10:07.889 substituting gallium into structures where it 00:10:07.889 --> 00:10:09.889 doesn't normally belong at all. Usually rings 00:10:09.889 --> 00:10:12.110 are made of carbon, maybe some nitrogen. Right, 00:10:12.110 --> 00:10:14.269 but we can swap gallium in there. They use things 00:10:14.269 --> 00:10:17.350 like diaz, abutidines. And the weird thing is 00:10:17.350 --> 00:10:19.789 how the size of the other atoms changes the result. 00:10:19.929 --> 00:10:22.490 It's all about steric hindrance. So steric hindrance 00:10:22.490 --> 00:10:24.769 is just a fancy way of saying too fat to fit, 00:10:24.850 --> 00:10:27.250 right? Essentially, yes. Imagine the gallium 00:10:27.250 --> 00:10:28.909 is trying to hold hands with another gallium. 00:10:29.169 --> 00:10:30.990 If the chemical groups attached to it are wearing 00:10:30.990 --> 00:10:35.950 giant puffy coats, big, bulky groups, the galliums 00:10:35.950 --> 00:10:38.429 can't get close enough to bond. So they stay 00:10:38.429 --> 00:10:41.509 separate. Monomers. Exactly. But if they take 00:10:41.509 --> 00:10:43.769 the coats off, meaning the groups are smaller 00:10:43.769 --> 00:10:46.309 and less sterically hindering, the galliums can 00:10:46.309 --> 00:10:48.830 get close, and they bond together to form a pair, 00:10:49.470 --> 00:10:51.669 a dimer. But here's the spooky part that you 00:10:51.669 --> 00:10:54.750 guys found. They looked at these rings with EPR 00:10:54.750 --> 00:10:57.590 spectroscopy, which basically detects magnets, 00:10:58.149 --> 00:11:01.769 and they found a paramagnetic anomaly. Yes, the 00:11:01.769 --> 00:11:04.509 zombie electron moment. Explain that to me. What's 00:11:04.509 --> 00:11:07.769 a zombie electron? So, in stable molecules, electrons 00:11:07.769 --> 00:11:09.769 are usually paired up. One spins up, one spins 00:11:09.769 --> 00:11:11.909 down. They cancel each other out. It's quiet 00:11:11.909 --> 00:11:14.429 chemically. But in some of these gallium rings, 00:11:14.750 --> 00:11:17.809 the EPR picked up a distinct signal. it found 00:11:17.809 --> 00:11:20.450 unpaired electrons. So the electrons are just 00:11:20.450 --> 00:11:22.929 spinning on their own? Yes. The molecule is a 00:11:22.929 --> 00:11:25.389 paramagnetic mononanian. It's acting like a radical 00:11:25.389 --> 00:11:27.389 even though it looks like it should be a neutral 00:11:27.389 --> 00:11:30.480 stable ligand. It tells us that the electronic 00:11:30.480 --> 00:11:32.519 structure of these things is way more complex 00:11:32.519 --> 00:11:34.600 than just drawing lines on a piece of paper. 00:11:34.740 --> 00:11:36.860 It's breaking the rules again. It's accessing 00:11:36.860 --> 00:11:39.139 states that shouldn't really be accessible. It 00:11:39.139 --> 00:11:41.460 loves breaking rules. And that's why it's so 00:11:41.460 --> 00:11:44.360 useful for making n -heterocyclic carbene analogs. 00:11:44.740 --> 00:11:47.080 Right. NHCs are hugely important in catalysis. 00:11:47.860 --> 00:11:51.360 GI allows us to create heavier gallium analogs 00:11:51.360 --> 00:11:53.779 of these carbenes that were previously almost 00:11:53.779 --> 00:11:56.340 impossible to make. It opens up entirely new 00:11:56.340 --> 00:11:58.320 coordination chemistry. Okay, let's move to my 00:11:58.320 --> 00:12:00.399 favorite visual in the whole file. The sandwich. 00:12:01.120 --> 00:12:03.679 Or I guess the half sandwich. Ah, the cyclopentadienyl 00:12:03.679 --> 00:12:07.019 complexes. An absolute staple of organometallic 00:12:07.019 --> 00:12:10.360 chemistry. Picture... a flat ring of carbon atoms 00:12:10.360 --> 00:12:12.759 for a second, like a slice of bread, and then 00:12:12.759 --> 00:12:15.740 you drop a metal atom right in the center, just 00:12:15.740 --> 00:12:17.399 hovering above it. That's the half sandwich. 00:12:17.700 --> 00:12:19.519 Okay. And gallium is excellent at this. It puts 00:12:19.519 --> 00:12:22.279 on this carbon ring like a hat. And there are 00:12:22.279 --> 00:12:25.399 two main sizes of hats. Right. You have the standard 00:12:25.399 --> 00:12:27.860 hat, gaseous, which is the basic ring in the 00:12:27.860 --> 00:12:30.019 gallium, and then you have the star version, 00:12:30.200 --> 00:12:31.879 gaseous star. The star makes it sound fancy. 00:12:32.019 --> 00:12:33.980 It's definitely fancy. It's the supersized version. 00:12:34.200 --> 00:12:37.570 It's a pentamethylcyclopentadienyl ring. Every 00:12:37.570 --> 00:12:39.909 single hydrogen on the normal ring is replaced 00:12:39.909 --> 00:12:43.090 with a methyl group. It's big, it's bulky, and 00:12:43.090 --> 00:12:45.029 it pushes a lot of electrons toward the metal. 00:12:45.309 --> 00:12:48.330 So we have the polite small hat, the Cp, and 00:12:48.330 --> 00:12:52.309 the big aggressive bulky hat, the Cp star. Let's 00:12:52.309 --> 00:12:55.289 see how these compare to transition metals. The 00:12:55.289 --> 00:12:57.789 notes talk about chromium and cobalt. Let's start 00:12:57.789 --> 00:13:00.190 with chromium. So if you take the small one... 00:12:59.879 --> 00:13:02.480 gang P, and react it with a chromium carbonyl 00:13:02.480 --> 00:13:05.000 complex, the gallium attaches directly to the 00:13:05.000 --> 00:13:06.860 chromium. And what does that do? It triggers 00:13:06.860 --> 00:13:09.899 the trans effect. The bond on the complete opposite 00:13:09.899 --> 00:13:12.279 side of the chromium atom actually gets shorter. 00:13:12.519 --> 00:13:14.899 It contracts. That proves the gallium ligand 00:13:14.899 --> 00:13:17.600 is strongly influencing the geometry of the entire 00:13:17.600 --> 00:13:20.409 molecule from across the room. Exactly. But the 00:13:20.409 --> 00:13:22.549 cobalt example is where it gets really wild. 00:13:22.970 --> 00:13:24.929 We call it the cobalt divergence. This is one 00:13:24.929 --> 00:13:27.529 of the clearest examples of how size matters 00:13:27.529 --> 00:13:29.690 in chemistry. So the setup is the same. You have 00:13:29.690 --> 00:13:32.049 a cobalt complex. It's happy. You introduce the 00:13:32.049 --> 00:13:33.830 gallium half sandwiches. First, you send in the 00:13:33.830 --> 00:13:36.850 big one, the GayMP star. It's huge. It approaches 00:13:36.850 --> 00:13:39.070 the cobalt complex, but it's too big to do anything 00:13:39.070 --> 00:13:42.330 drastic. So it just nudges a bridging carbon 00:13:42.330 --> 00:13:44.389 monoxide molecule out of the way and takes its 00:13:44.389 --> 00:13:46.830 place. It just bridges the gap very gentlemanly. 00:13:46.909 --> 00:13:49.830 Now the little guy. The standard GAKP. The little 00:13:49.830 --> 00:13:52.629 guy has absolutely no chill. Because it's smaller, 00:13:52.750 --> 00:13:55.389 it can get right in there. It performs an oxidative 00:13:55.389 --> 00:13:57.450 addition. Which is what exactly? Think of it 00:13:57.450 --> 00:14:00.629 as a bear hug that turns into a tackle. It completely 00:14:00.629 --> 00:14:02.889 breaks the bond between the two cobalt atoms 00:14:02.889 --> 00:14:06.070 and inserts itself right into the middle of the 00:14:06.070 --> 00:14:08.750 structure. It interacts with both cobalt units 00:14:08.750 --> 00:14:12.029 and changes their oxidation state. It fundamentally 00:14:12.029 --> 00:14:15.070 rewires the molecule. Completely. The big scary 00:14:15.070 --> 00:14:18.679 looking molecule was gentle. and the small unassuming 00:14:18.679 --> 00:14:22.200 one was the home invader. The lack of bulk allowed 00:14:22.200 --> 00:14:24.899 it to get close enough to wreak havoc. It really 00:14:24.899 --> 00:14:27.600 is a shapeshifter. It changes its behavior entirely 00:14:27.600 --> 00:14:29.980 based on what it's wearing. It does. But we haven't 00:14:29.980 --> 00:14:32.200 even reached the final form yet. We've done sandwiches. 00:14:32.580 --> 00:14:35.799 Now we have to talk about skyscrapers. The clusters. 00:14:36.059 --> 00:14:38.000 This is where we leave simple molecules behind 00:14:38.000 --> 00:14:40.220 and start building real architecture. We are 00:14:40.220 --> 00:14:43.860 talking about giant clusters of 9, 10, even more 00:14:43.860 --> 00:14:46.940 gallium atoms. The notes mention a specific gannine 00:14:46.940 --> 00:14:49.919 cluster, and the shape sounds impossible. A pentagonal 00:14:49.919 --> 00:14:52.960 bipyramid. Picture a diamond shape, but with 00:14:52.960 --> 00:14:54.779 five sides around the middle equator instead 00:14:54.779 --> 00:14:58.299 of four. It's a beautiful geometric solid made 00:14:58.299 --> 00:15:01.090 almost entirely of gallium. And it has these 00:15:01.090 --> 00:15:03.750 weird outer attachments, too. Yes, it's surrounded 00:15:03.750 --> 00:15:08.230 by six massive, silly groups. Specifically, silicon 00:15:08.230 --> 00:15:11.669 atoms attached to three trimethylsil groups each. 00:15:12.350 --> 00:15:14.909 But the math on the gallium atoms doesn't add 00:15:14.909 --> 00:15:16.909 up. Right. If you try to calculate the oxidation 00:15:16.909 --> 00:15:19.789 state, you get something like 0 .56. That's not 00:15:19.789 --> 00:15:22.830 a real number in chemistry class. It's an average. 00:15:23.110 --> 00:15:25.490 It tells us that the electrons are highly delocalized. 00:15:25.750 --> 00:15:27.889 They're smeared out over the whole skeleton of 00:15:27.889 --> 00:15:30.450 the cluster. It's acting less like a molecule 00:15:30.450 --> 00:15:32.649 and more like a tiny, tiny chunk of bulk metal. 00:15:32.960 --> 00:15:35.480 It's a metalloid cluster. And you notice there 00:15:35.480 --> 00:15:38.659 are only six silly groups protecting nine gallium 00:15:38.659 --> 00:15:41.200 atoms. Fewer attachments than corners. Highly 00:15:41.200 --> 00:15:43.320 unusual. And then there's the cobalt cubane, 00:15:43.539 --> 00:15:45.460 which sounds like a specialized cigar, but I 00:15:45.460 --> 00:15:47.320 know it's a shape. It's a cube. Well, mostly 00:15:47.320 --> 00:15:50.200 a cube. Imagine a sugar cube made of atoms, cobalt, 00:15:50.240 --> 00:15:52.360 and gallium, alternating at the corners. Now 00:15:52.360 --> 00:15:54.480 just rip one corner off. That's the shape. That's 00:15:54.480 --> 00:15:56.879 the shape. It's called a niter -type cluster, 00:15:57.139 --> 00:16:00.320 like a nest. But the mind -bending part isn't 00:16:00.320 --> 00:16:02.759 the shape. It's what holds it together. Because 00:16:02.759 --> 00:16:05.019 usually atoms in a cluster are bonded to their 00:16:05.019 --> 00:16:07.539 neighbors. You'd expect the gallium atoms to 00:16:07.539 --> 00:16:09.720 be holding hands with the other gallium atoms. 00:16:09.879 --> 00:16:12.200 Right. But when they ran the complex computer 00:16:12.200 --> 00:16:15.919 simulations, specifically QTAME analysis, For 00:16:15.919 --> 00:16:19.039 the structural nerds out there, they found absolutely 00:16:19.039 --> 00:16:22.000 nothing between the galliums. No bonds? Zero 00:16:22.000 --> 00:16:24.679 gallium -gallium bonds. The galliums are tightly 00:16:24.679 --> 00:16:27.700 bonded to the cobalt atoms, but they are completely 00:16:27.700 --> 00:16:29.620 ignoring each other. So it's a go structure. 00:16:29.639 --> 00:16:31.519 It looks like a solid block, but the internal 00:16:31.519 --> 00:16:33.960 horizontal supports are missing. It's held together 00:16:33.960 --> 00:16:36.139 entirely by the transition metal interactions. 00:16:37.000 --> 00:16:39.200 The cobalt is doing all the heavy lifting, keeping 00:16:39.200 --> 00:16:41.740 these gallium atoms locked in formation. That 00:16:41.740 --> 00:16:44.379 is bizarre. And finally, we have to talk about 00:16:44.379 --> 00:16:47.039 the bling. Because apparently our messy groom 00:16:47.039 --> 00:16:50.299 powder can even bond with gold. This was a huge 00:16:50.299 --> 00:16:54.639 deal in the field. For a long time, a true crystallographically 00:16:54.639 --> 00:16:57.639 confirmed gallium -gold bond was mostly theoretical. 00:16:58.320 --> 00:17:00.720 But Gray made it happen. What does a gold cluster 00:17:00.720 --> 00:17:04.039 even look like? In this specific case, it was 00:17:04.039 --> 00:17:07.240 a triangle of three gold atoms surrounded by 00:17:07.240 --> 00:17:09.839 these gallium ligands protecting them like bodyguards. 00:17:10.019 --> 00:17:12.279 And are they sharing electrons nicely? That's 00:17:12.279 --> 00:17:14.720 the interesting part. It completely depends on 00:17:14.720 --> 00:17:16.839 where the gallium is standing. If the gallium 00:17:16.839 --> 00:17:19.940 is just attached to one single gold atom, the 00:17:19.940 --> 00:17:22.940 bond is super polarized. It's a very unequal 00:17:22.940 --> 00:17:24.819 relationship. There's a big charge difference. 00:17:25.220 --> 00:17:27.160 And the gallium is basically throwing electron 00:17:27.160 --> 00:17:29.980 density at the gold. But if it bridges? If the 00:17:29.980 --> 00:17:32.380 gallium sits right between two gold atoms, holding 00:17:32.380 --> 00:17:35.099 onto both, the bond becomes much more covalent. 00:17:35.230 --> 00:17:38.349 more sharing. It becomes more like a true partnership. 00:17:38.670 --> 00:17:41.029 So even with gold, gallium is adapting. It says, 00:17:41.130 --> 00:17:43.150 if I'm here, I act this way. If I'm there, I 00:17:43.150 --> 00:17:45.549 act that way. Exactly. It creates polarity where 00:17:45.549 --> 00:17:47.670 you need reactivity and it creates covalency 00:17:47.670 --> 00:17:49.910 where you need stability. It is the ultimate 00:17:49.910 --> 00:17:52.250 chemical diplomat. So let's zoom out for you 00:17:52.250 --> 00:17:54.890 guys listening. We started with a scientist screaming 00:17:54.890 --> 00:17:57.329 at liquid metal in 1990 to make a pale green 00:17:57.329 --> 00:17:59.509 powder. A powder that everyone thought was a 00:17:59.509 --> 00:18:01.549 simple one to one salt, but turned out to be 00:18:01.549 --> 00:18:04.220 a chaotic mixture of everything at once. We learned 00:18:04.220 --> 00:18:06.519 that this mistake, this incomplete reaction, 00:18:06.740 --> 00:18:09.819 was actually the secret weapon all along. It 00:18:09.819 --> 00:18:12.900 allowed chemists to steal carbon rings from antimony, 00:18:13.380 --> 00:18:16.079 weld molecules together, build sandwiches that 00:18:16.079 --> 00:18:19.319 break cobalt bonds, and construct massive clusters 00:18:19.319 --> 00:18:21.900 with weird math. It really challenges the way 00:18:21.900 --> 00:18:25.059 we think about purity in science. In school, 00:18:25.240 --> 00:18:28.319 you're taught that pure is good and pure is bad. 00:18:28.640 --> 00:18:32.059 But here... The impurity was the actual engine 00:18:32.059 --> 00:18:35.000 of discovery. The unreacted metal, the mixed 00:18:35.000 --> 00:18:37.799 valence, states that chaotic energy drove the 00:18:37.799 --> 00:18:40.079 chemistry. It makes me wonder about all the other 00:18:40.079 --> 00:18:42.140 failed experiments sitting in lab notebooks right 00:18:42.140 --> 00:18:44.089 now. Oh, absolutely. Think about how many times 00:18:44.089 --> 00:18:46.230 a graduate student has thrown away a weird gunk 00:18:46.230 --> 00:18:48.609 or a sludge because it wasn't the beautiful pure 00:18:48.609 --> 00:18:50.630 crystal they were looking for. When the sludge 00:18:50.630 --> 00:18:52.809 might have been a massive breakthrough, gallium 00:18:52.809 --> 00:18:55.210 anodide teaches us to look closer at the mess. 00:18:55.329 --> 00:18:57.970 It does. Because if a simple mix of gallium and 00:18:57.970 --> 00:19:00.390 iodine can hide this much complexity for over 00:19:00.390 --> 00:19:03.509 20 years, imagine what other simple compounds 00:19:03.509 --> 00:19:06.289 sitting on a shelf right now are actually misunderstood 00:19:06.289 --> 00:19:08.990 treasure troves of reactivity. Never throw away 00:19:08.990 --> 00:19:12.670 the sludge. Never throw away the sludge. That's 00:19:12.670 --> 00:19:15.150 a terrifying and exciting thought for anyone 00:19:15.150 --> 00:19:17.589 working in a lab today. Thanks for diving deep 00:19:17.589 --> 00:19:20.869 with us into the weird chaotic world of gallium 00:19:20.869 --> 00:19:22.970 mannoyidae. Always a pleasure to be here. We'll 00:19:22.970 --> 00:19:24.930 catch you on the next deep dive. Stay curious.