 I did not realize that the start of this was an effort to embarrass the speaker, thank you both. And perhaps the nicest thing that's ever been said about me was said that he's a regular guy, thank you. I feel honored by that. It's a big general talk, so let's have some fun with the chemistry that we do. So I'll give you some context about our work and that. And so in general, the group does, and I'm gonna point at this screen, I know there's two screens, but I'm right handed, so I'm gonna point over here. The work, one of the major efforts in the group is to think about catalytic ways in which we build main group bonds. And now I have to stop, because this is actually a general audience, so we have to define some things. I've already thrown out two pieces of jargon. The first one is main group, and so here's a periodic table, so this is our commodity. And by main group I'm referring to the elements in the P block, the so-called P block. So elements that are filling their valence P orbital. And a lot of the chemistry's gonna be about phosphorus today, and I like phosphorus, and Chris likes phosphorus too, so this is good. And when I talk about catalysts, I'm gonna think about, in particular, using metals, transition metals as catalysts, and arguably the star of the show for the catalyst site is zirconium, although there'll be some other players too. Okay, so we're back on. Now, so we're trying to find catalysts, we're trying to do main group chemistry, and our goal is pretty simple. We wanna build molecules that have sigma bonds and pi bonds between main group elements, be it phosphorus or anything else. And it's a simple goal, it makes sense. And so the reason to do that is that there are molecules that are known that are valuable. And organic chemists would argue for things like silo-phosphines as precursors to synthetic steps, and you can look at a diphosphine, a phosphorus-phosphorous double bond as an interesting moiety, although you could also put it into a long chain polymer and then it becomes a useful material. And what's important about this, and the connecting point for us is that there are a limited set of methods by which these molecules can be made. So an honest main group chemist, which I'm sure they all are, would tell you that the synthetic tools that you have to build in the main group are largely SN2 and E1, so I'm talking to the chemist again, which is not a whole lot of tricks. And so in any way that we can increase the number of tools in the toolbox in order to do the chemistry, that's a big deal. The other thing is just about everything we make in the main group on any scale is made stoichiometrically, so there's a lot of waste involved in that. Catalysis is our way to get out of that waste. And then finally, building element carbon bonds. So while I'm talking about the main group, we usually exclude carbon, nitrogen, and oxygen when we say main group chemistry. It's because it has its own excellent discipline and you'll hear about it next month from Matthias Brewer and that's organic chemistry. However, building bonds between a lot of main group elements and carbon is still a synthetic challenge and so that's a particular component that we'll talk about today. So what do we actually wanna do? So I'll tell you about why making molecules is hard. I put that in the abstract and I promise to address that. The other thing is I'll tell you about how catalysis makes that easier. It's a questionable idea, but it's possible. And then the way to do that, of course, is I'll tell you about some of this phosphorus carbon bond building, so this EC bond formation chemistry. And what's the whole point of the deal? Sit here, I hope you get something out of it. I'll tell you upfront. I like to make molecules. I think the chemist in here, the molecule makers as opposed to spectroscopists like to make molecules. It's fun, even though it's hard, it's a good challenge, but in particular, catalysis makes that job easier. So that's what makes it good. Okay, why is synthesis challenging? Well, the first problem is that chemical equations lie to us. Sorry, we tell you about this in Gen Chem. That's just what it is. So let me lay out a good example of this. I want hydrogen. Hydrogen's good because if I had hydrogen, it's a clean burning fuel, right? But the problem right now is that we make most of our hydrogen a vast, vast majority of it from oil and coal and natural gas. That's not a clean burning fuel. Okay, so then I would, as a student, rigged out a chemical equation, make hydrogen from something generally available, water. Okay, so this looks good, right? I did my graduate work at the University of Chicago, and it's an academically gritty school. And when I was a graduate student there, there were at least a couple of people who still used to put down on exams and things when questions weren't correct, things like WAS, wrong and stupid. And so this is both wrong and not very useful. This is actually not chemistry that's gonna get us the hydrogen that we need. The wrong part I can fix pretty easily. That's just an arithmetic problem. I'll just balance my chemical equation. And then from a Gen Chem standpoint, I think the question is correct. I didn't answer why this is a problematic reaction. And that's the first real problem with synthesis. And that is the energy matters. So if we think about an energy scale in which energy goes up in the world, we would like to be at the lowest energy possible. So that's the way I've ordered my energy scale. And then in any chemical reaction, if we think about we're starting at the start, which we'll just call it the left because we, you know, in this culture, read from left to right. And then as things go along, we'll move along the right. So this gives me what's called a reaction profile diagram. And so I start here with any reaction and it's just an arbitrary energy so I can compare things. I have choices. So the products could be at higher energy or the products could be at lower energy. And that I only mean relative to the starting material. So if I think of the starting material energy coming over, the reaction proceeds to products and the products could be at higher or lower energy. If they're at higher energy, this is not a favorable process. That is I had to put energy into the system for this to occur at all. And so this is not a useful reaction in that it will not be something that will spontaneously happen. The alternative is of course that the react, the energy goes lower and then the reaction is favorable as we say. And so in general, we like favorable reactions. Those that go net downhill. There's another sort of colloquial term that we like to use for this. Okay, so energy is something. Chemists are pretty good. And my water example I go uphill. That's the problem with it is that splitting water is an uphill process. Chemists though, we can game the system. And so this is a reaction that we like in like Rube. This is one, it's called phosphine dehydro coupling. And so we can build a chemical bonds between phosphorus by this process. We can take a couple of phosphines. So organophosphorous, three molecules, bring them together and make a phosphorus-phosphorous bond. The problem is that this is a terrible chemical reaction. This bond here, the phosphorus-phosphorous bond, 50 kKals per mole, so it's a number for you. But what it is, it's a very weak bond. So it's not very favorable to make. Like I said, chemists game the system and so the reason we do this reaction in this way is that we can generate hydrogen as a byproduct. Hydrogen has the strongest sigma bond among molecules. And more than that, we can generate a gas as well. And so then what we can do is convert what should be a very unfavorable reaction that is going to make this weak chemical bond, but by coupling it to this other process, we can make it favorable. So we can game the thermodynamic system, and that's pretty good. That's just one problem. The second problem is still energy related, but it matters, it's not just the products that matter. So this is not referring to how the starting materials get to the product. And there's an energetic pathway that must proceed. And so invariably what happens is there's some sort of an initial barrier. There's a starting energy that's required, an activation energy to make this reaction occur. And that occurs with some kind of measurable amount. And this is regulated and normalized and all that. And this refers to the kinetics, how fast things happen. But there's no guarantee of how big this activation energy is. And so it could be quite large. And so in that regard, very large energy barriers are unfavorable, whereas small energy barriers are more favorable. So faster reactions are ones that have smaller energy barriers. And large energy barriers are slow reactions. And we have less control over this. This is not something that we game as easily. We can game the system a lot on the downside of this and the product energies. OK, so that's two problems. There's four. The third problem is going to be a little bit more subtle. So this looks like a perfectly nice reaction. It's balanced. And in the energetics in the system, it's not too bad. That is actually everything sort of breaks approximately even. I have a hydrogen. I have deuterium, which is just heavy hydrogen. And I can make two equivalents of HD. That is the next molecule. So they have the same number of molecules. They have the same approximate bond energy. Everything seems OK, but this is not going to happen under any reasonable condition. And that's because the third problem is orbitals. So we taught about, you probably learned about orbitals in your initial chemistry forays, particularly for students. Maybe the folks who are a little farther along forgot about this a long time ago. And the problem is that there's no net overlap in this particular reaction. There's no impetus for this occur. And this gives rise to what are called symmetry rules for reactions. So some perfectly reasonable-seeming reactions occur for what appears to be an opaque reason. And it can be understood. It can be known. And that's not the worst thing. The last problem is an entirely pragmatic problem. It's something that I'll call synthetic space. And this is the one that, for people who are practitioners, they know a lot about this. And there was a nice article a few years ago in Jake Hamad about this idea. And that is to say that your maximum yield of product, the total amount of stuff you make, gets optimized based on what's called an environmental function. And that refers to all the stuff. What solvent you're using, what temperature, the order in which you add things, the phase of the moon, whatever it is, whatever factors go into it. And so some reactions are pretty intolerant of the environment. And they have a wide sweep. And you'll still get a high yield, depending upon the variances that you run in reactions. And then some reactions are very persnickety, for lack of a better word, that they are very particular about conditions. And if they're not run properly and exactingly, then you don't get very much stuff. I'm not going to worry too much about this idea. This is more of a practitioner's idea. This is very empirical. When you're running reactions, you try iterations until you get things right. But all these other issues about activation energies are particularly important. And symmetry considerations, things that just shut off reactions, these are things that we need to fix. And so the fix is, of course, something simple, like pixie dust. We could use some pixie dust. And that's the whole search here, right? So everybody knows that pixie dust, of course, comes from pixies. That doesn't look right. That's pixie. So what I really mean, though, is there is a very good and valid substance that will do this sort of pixie dust transformation for us. And that's a catalyst. And what's nice sometimes is that when science words and everyday words kind of come together, and we use catalysts, that guy's a catalyst for change, for example. So we use that word in our regular speech. But it doesn't quite have the same meaning. And my favorite definition of catalysis comes from the person who coined it in a guy called Brazilius. Some substances awaken activities that are slumbering the molecules. And he published that. And if I wrote that in a paper, I'd get such heat from reviewers about that. But it's a beautiful idea. In truth, the Merriam-Webster definition does us well. It facilitates a chemical reaction. It allows it to happen. It allows it to happen faster or more selectively or work better. So what does that really look like? The idea is that if nothing else, catalysts make reactions easier. And so I talked about this idea of these barriers, these activation energies that allow reactions to occur. And if we have a high, uncatalyzed barrier, the reactions are simply not going to happen, as opposed to having a lower barrier and a catalyzed reaction. Now, I have this here. And this is a good first pathway of looking at it. But in truth, most catalysts don't do this. Because this suggests that the catalyst is doing exactly what the reaction would inherently do. That the path of the reaction is doubtlessly changed by the addition of the catalyst. And so the energetics look different. And that's OK. Because at the end of the day, the energy is lower. And so the reaction is more likely to occur. And in fact, by changing the pathway, we may get around that orbital requirement, that symmetry requirement. And so these are good things. So we can potentially solve more than one problem at once with the catalyst. We can both make the reaction more fast and we both can turn on reactions that are unlikely to occur otherwise. OK, so catalyst works for synthesis. That's the basic idea. And then I'd like to just briefly convince you that it's a valid activity. And so catalyst is good. And I mean this in the Superman is good kind of way. So this is the cover of green chemistry theory and practice. So before sustainability was a real world, we had this word green. Folks may remember that. We used to say everything was green as opposed to sustainable. And then we changed the word. So chemists haven't changed. I don't know if we're just lazy or whatever. We can't spell sustainable or whatever it is. But we continue to say green. We have 12 principles of green chemistry. And in fact, catalysis is explicitly one of them. It's number nine. And so in these defined principles, they talk about increasing safety, decreasing waste, improving the ability of degrading products that is so things don't last forever in terms of waste streams, and reducing hazards and problems. And catalysis is, in fact, one way to achieve these kinds of goals. That's still an internal definition. Let's go a little bigger than just what chemists say about chemistry in itself. Catalysis is important. And I'll make the Nobel argument. So the last, there are three Nobel prizes in chemistry in the current millennium for catalysis. Asymmetric catalysis, it was awarded to these three folks, Nils, Nouriery, and Sharpless. 2005, there was a second prize about olefin metathesis. And 2012, there was a third prize about palladium coupling. And so statistically speaking, pretty good odds, about 20% odds of a catalysis award in the 21st century. And that's nice. And this is all OK. I point specifically to Nils because it comes back to our phosphorus chemistry. And I steal the diagram from the Nobel Prize website. Nils specifically had discovered a way to hydrogenate a precursor to ultimately make al-dopa. Al-dopa still uses a treatment for Parkinson's disease. This is a more efficient route to making al-dopa and making specifically the enantimer that is effective. I suppose the one is ineffective. And part of that innovation was that Nils had designed these phosphorus-containing auxiliaries for the metal that does the catalytic reaction. Nils in particular has the fantastic quotation of saying phosphorus is where the action is. And as a phosphorus chemist, I like that. So my point to Nils is contribution. Now, I'm still pretty internal. The Nobel Prize in chemistry is awarded to chemists by chemists. So let's get bigger and really important. And so this is a lot of text. I'll read it to you briefly. Catalysis counts for around $3 billion per annum in the US chemical industry alone. And it can be estimated that each dollar spent on catalysis creates around $150 worth of products. So it's a lot of money, and it makes a lot of stuff. So as an industry, that's pretty good. That's a big economic driver. So if it's money you're about, this is a winning strategy. I'll point to another unrelated reaction involving catalysis because it is incredibly important by any measure. So this is what's called nitrogen fixation. So we, all living things, not just human beings, not just animals, all living things need nitrogen. We need it in various forms for various processes. And the way we get it is from the atmosphere. It's the conversion of atmospheric nitrogen to ammonia. When this happens in nature, it happens through an enzyme called nitrogenase, lives in little bacteria that tend to hang out and around the root systems of legumes, and that fixes a good bit of nitrogen. It is, when it is done by human beings, it's called the Haber-Bosch process. It was discovered around the turn of the last century. It was really ramped up around 1910. And just to give you an idea about how important this reaction is, I'll plot for you the population of the earth and humans over time. And so from 1750, and this projects, so we're about here, population has gone up incredibly, and incredibly fast since the Haber-Bosch process went online. And the reason is very simple. The ammonia gets converted to ammonium nitrate, and that is a base fertilizer. We can feed ourselves. And so because we could feed ourselves better than we ever could, crop yields went up astronomically as a result of this process, then people simply could reproduce, mortality rates increase, people live longer, and there are more people. It's just the simple result. You may make whatever value and judgment you want of that information. And for numbers, just to give this another set of scope, it's about 2% of the world's energy goes to fixing nitrogen every year. So that's a pretty substantial investment. The estimates are about 80% of the nitrogen in your body is the result of the Haber-Bosch process, as opposed to the biogenic process. And if we stopped doing this right now, approximately half of the people on Earth would die, because they would not be able to feed themselves. So the scope and scale of catalysis is quite large, and that ignores all the other examples. Catalysis touches you in every way you can imagine, but this is just one example. I can group kinds of catalytic reactions for you. I started drawing a slightly silly Venn diagram about the different ways in which we could think about things. You could talk about energy input or phases or the kinds of reactions that it's doing, whatever you wanna think about. But today I actually wanted to focus on two specific transformations. One of them being the cleavage of element hydrogen bonds. So back to this main group chemistry, so all of those elements can conceivably bond hydrogen. They make for reasonable precursors. So we can snap those open, and that's the idea. And then we can start to do chemistry with that at these metals. And in particular, the reaction I wanted to think about today was the idea that we could add those element hydrogen bonds across unsaturated substrates. And in general, people call that heterofunctionalization, and I'll give you an example. So this is an unsaturated substrate in olefin, for example. And here's an organosilane that has a silicon hydrogen bond, one of these EH bonds that I mentioned. And with a catalyst, one can add that SIH bond across the olefin to make this organosilane product. And then our reaction's called hydrosilation, or hydrocyylation, if you like, extra syllables. And so this reaction is also pretty important. So literally, billions of pounds of hydrocyylated products are made. One catalyst for making, for example, siloxane derivatives of this is platinum-based. And we literally consume about five and a half, or sorry, five and a half metric tons of platinum is unrecovered annually making siloxanes, which you're probably wondering why I'm bringing up siloxanes. You may have no idea what that is. The most ubiquitous siloxane in your life is probably post-it note glue. So the back of every post-it note has a little platinum in it, just a little bit. But the reaction is so important and so efficient it's worth throwing out all that platinum in order to have all these siloxanes that we use for a lot of different things. So there's a good bit of utility way. I'd like to define a couple of kinds of catalysts, and so I'll tell you what they are as we go. One of them is based on this phosphine-dehydro coupling reaction. So I mentioned this earlier. This is an important reaction. We've been doing it for about a decade. This is the idea that we can take an organophosphine, make this phosphorus-phosphorus bond, and the byproduct is hydrogen gas. What's interesting about phosphine-dehydro coupling is that it absolutely requires the catalyst. It will not happen. This is one of those symmetry forbidden reactions. I can't bring the pH bonds together, and they'll have them overlapping in an effective way to make H2. So the catalyst allows us to happen. And the reason we targeted this reaction is that we thought there was a couple of good things that could be done with it. One of them is that we could make new, complicated molecules as precursors to other things or important for their own purposes. They also have the possibility that we could make some interesting materials. And so we've had some successes with that. In particular, we've been focused on these zirconium catalysts, and I'll tell you a little bit about zirconium in a minute. But what has worked well for us is that we have in fact been able to make molecular structures that are unusual and complex in that regard. We can make some new kinds of materials, so polymers that have phosphorus repeating in the main chain, which is a somewhat rare system, and indeed may have interesting electronic properties. And at the end of the day as a synthetic tool, we're able to make phosphorus, phosphorus, since phosphorus element bonds using this technique. And so it works for a variety of different purposes. And it's all rested on the shoulders of this molecule. It's so important that I wrote it in the bottom right corner of the slide. This is zirconium. And this is zirconium that's supported by an organic ligand. So this is an organometallic system. And we focus on this particular ligand, it's a trend for lack of a better word. It's a tris-aminoethylamine. We've been working on this for a while, and we had developed a pretty good and useful synthesis for this, which is based on near-commercial or near-commercial precursors in a single step, and we can make this zirconium compound that features in particular, which is very important to us, this sila azimutallicyclobutane, that four-membered ring. And that four-membered ring is very reactive. It does a lot of things. And one of the most important things for us is that you can open it up again. And we can open it up with any polarized element hydrogen pond. And so a good example of that would be phosphorus. So phosphines, primary and secondary phosphines, readily open the sila azimutallicyclobutane and form terminal phosphidocom compounds of zirconium. So we have access to these reactive zirconium phosphorus chemical bonds. And I show here the molecular structures as determined by X-ray crystallography. And this I note specifically, I'll have some names at the bottom. This is the work of a former PhD student, Andy Raring. We can extend this chemistry to a lot of different systems. So for example, we can build zirconium arsenic bonds in the same way. So there's a structure of an arsenide derivative. We can go further down the periodic table and group 15 and build antimony zirconium bonds with a stebido derivative. We can branch back up in group 15 to make the amido derivatives work of Annalyze Maddox, a former master's student. We can also do, we can jump over to group 16 and make file derivatives. So Taylor Elrod was a bachelor's student. And amusingly, we talked about this, we developed this project. And for people who don't know, files. Files are smelly. Files are the thing that make your natural gas smell. That's so you know. And I said, Taylor, just so you know, I'm deliberately trying to ruin your sex life in lab by making you work with files. And so we can also use oxygen and make alkoxide and aryl oxide derivatives. So still sticking into group 16. And finally, we can even cleave carbon hydrogen bonds. And so this alkynal derivative, for example, can be prepared right reaction of a terminal alkyne with this sila, is a metallocyclobutane. And so this whole pinwheel thing just represent the basic utility of opening that ring. Okay, so the other kind of catalysis I wanted to tell you about is that where we do not require the catalyst. And that is hydrofosphination. So I told you about this EH addition chemistry and I showed you specifically hydrosilation. And hydrosilation does require a catalyst. Hydrofosphination is weird because hydrofosphination does not always require a catalyst. Sometimes an organophosphine like this will add to an unsaturated substrate. It won't happen all the time. It doesn't happen for all the substrates, but it'll happen sometimes. So the catalyst is important because the catalyst allows us to open up the substrate scope. It allows us to think better about what kind of reactions are possible. And this kind of transformation has been under investigation for like 30 years. And maybe not that long, 25 or 30 years. Relatively new transformation. And so Christina and I, Christine's a current PhD student. We sort of sat down and thought about what's going on in hydrofosphination. What's useful, what's not? What are the challenges? And so we wrote this article earlier this year and talked about specifically the challenges in metal catalyzed hydrofosphination. And so the yellow might be tough to read there. And so the three challenges are the identity of the catalyst. So what it is that does this. The substrate scope. So both the phosphorus and the unsaturated system. And then the selectivity. Are you actually making the kinds of things you want? Do you have some choice in it? And so these are the kinds of challenges that are set forth for us as chemists that do this kind of reaction. I won't address these specific things in detail. I'm gonna tell you a little bit about our work in hydrofosphination now. Only as an example of the kinds of chemistries that we do. And then in fact, we do try to address at least some, if not all of these. The way our hydrofosphination chemistry started was through the logical progression by which organometallic chemists do chemistry. And so this molecule I showed you, there's a lot of derivatives here. I talked about that ring opening reaction of the Psylasa Metallicycle butane and it made these phosphatode derivatives. And Andy and I confronted with these new compounds thought about the way we understand molecules in organometallic chemistry. And that's typically to take those and react them with small molecule substrates and see what the products are and the reactions are because if we emulate what's known, then we understand it. And if we don't, we've discovered something new. This is a reasonable pathway to ask questions about stuff. And in a whole series of reactions, we found that we were doing insertion. So one, two insertion. And that's the idea that the two atoms in the multiple bond are inserting literally into the zirconium phosphorous bond. So nitrogen, carbon go into zirconium between zirconium and phosphorous. And these one, two insertion reactions are reasonable, persistent. And we can structurally characterize the products so everything made perfect sense at the time. And as we stood there, we said, okay, we can do insertion of these zirconium phosphatode compounds. They activate phosphorous hydrogen bonds. So the reasonable next thing is to think about hydrophosphonation. Can we do this catalytic reaction? And so we tried and it succeeded. So we could take terminal all kinds and phosphines and hydrophosphonate. We can also take arsenines and hydro arsenate and perhaps people have misgivings about arsenic and I'd be glad to talk with them about that later because they're probably ill founded. But anyway, so we can do this hydrophosphonation, hydro arsenation. But what was weird is that we were running through this chemistry and we were finding big, big limitations. One of the biggest ones was on the unsaturated substrate side. It really only worked for the terminal alkyne. It didn't work for internal alkynes. That is alkynes that had R groups on both sides. It didn't work for alkenes, so double bonds. Didn't work for much other than the carbon-carbon triple bond. And so Andy and I reasonably said, you know, this is not going anywhere. We just sort of need to back out of this and kind of be done with it. And while we were getting in that sort of mindset about it, we observed an apparent equilibrium between the phosphatocompound and this terminal alkyne alkyne. And I showed that to you before. It was the product of an alkyne with acylase and metallocyclobutane. What was important about this observation is that we said, you know, this is good. OK, it makes sense because these are both valid ligands. But the issue is that maybe the reason why this is the only substrate we can do this chemistry on is not because alkynes are uncertain to zirconium phosphorous bonds, but maybe it's because phosphines just add spontaneously to an activated alkyne. That is one that is bound to zirconium. That's a reasonable supposition. Now, we thought about that for a long time, and it seemed really difficult to test. And given that this wasn't very good catalysis, Andy and I, like, two, I hope, reasonably intelligent people said, we're not going to test it. The heck with that knowledge. So we moved on. But being at least moderately thorough chemist, we said, you know, there is one question to ask. If I rewrite this as a proper equilibrium, these two starting materials, these two products, going back and forth, can we at least measure the equilibrium constant? That would be a useful thing to know. And so, like good chemists, we set up the two reactions, the one on the right and the one on the left, and wanted to measure the equilibrium constant of each. And if they matched, then we had a good constant. So the reaction on the right, if we take the terminal alkyne compound and diphenylphosphine, a whole lot of nothing happens. And this was perplexing to us, because there was catalysis before. So why was a whole lot of nothing happen? We realized a good way to assess that was actually to replace that hydrogen with deuterium and look at this reaction with deuterated phosphine. And in fact, when we do that, we see 100% conversion to the protonated phosphine. So nothing apparently changes, except all the deuterium comes off of phosphorous. Now, it doesn't just go anywhere. The deuterium actually specifically goes onto these trimethylsal substituents. And so what we learned that was pretty important is that, in fact, the alkyne comes right off. It leaves zirconium. The phosphorous can come onto zirconium, open that psilase and metallocycline butane. The energetics of the system or the deuterium would prefer to be on the trimethylsal substituent. The phosphorous comes up and then the alkyne comes back. And so if we learned nothing else, we knew that KEQ was very large favoring the right side. We didn't know what the magnitude was, but we knew it was very big because we could only see this product even though there was actual chemical exchange occurring. To be thorough, we did the left side of the reaction as well. And indeed, as expected, it primarily made the terminal alkynal compound. That's the most stable compound in the system. So that made sense. There was some phosphidocompound that was preserved and the reason is that we made some product. We made some of this vinyl phosphine. And the reason that we had made some vinyl phosphine was that some insertion was allowed to occur. And so we put all those pieces together and figured ourselves out a mechanism that was indeed based on insertion. So the phosphidocompound reacts directly with the alkyne to form this vinyl insertion intermediate, which is then released via cyclometallation and then the catalyst is restored. The whole thing with the alkynal compound is that it's actually a substrate inhibition. The substrate comes in, forms this terminal alkynal compound which has no reactivity that's productive with respect to catalysis. So we simply have to wait for this to come back into the cycle and activate again. So this was back in 2010, this was a while ago. And so, reasonably so, we said we're not doing any more hydrophosphonation. This is not that good. And then a few years later, what had happened was another PhD student, Mike Gabreib, was working on this dehydro coupling. And so Mike was in the middle of this and he was fretting about this because this reaction is awful at low temperatures. Phosphid dehydro coupling has a lot of problems for reasons that I don't have time to talk about but it is indeed quite slow. And so Mike had a reasonable hypothesis. He said, you know, if I could get the hydrogen out better, then this reaction may be faster. And he said, one good way to get hydrogen out better would be to add something to accept the hydrogen chemically. And alkenes can do that. You can hydrogenate alkenes. And so he considered adding an alkene to this reaction. That hypothesis is importantly predicated on the idea that this catalyst is both a dehydro coupling catalyst and a hydrogenation catalyst. It has to be. Hydrogen doesn't spontaneously add to alkenes. Turns out our zirconium compounds are not very good hydrogenation catalysts. However, under these reaction conditions we get very good hydrophosphination. And the reason we see this reactivity now when we missed it before is that this is a primary phosphine. There's only one organic substituent on it. All that other chemistry that Andy had been working on was with a secondary phosphine, two organic substituents on it. So the number of organics on the phosphorus makes a big difference. Andy and I were doing this chemist, sorry, Mike and I were doing this chemistry and we were thinking about it going, boy, this is not good. We can't have mixtures of products. That's not good catalysis. We're never gonna be able to report this in a self-respecting journal. And so the reality is that we needed to be able to selectively make either of these products. And the second product, the one in which we've done two pH addition steps. So the tertiary phosphine product, the one that has now three organic substituents as opposed to the secondary product, the one that has two organic substituents, it's actually easier to make. We simply push this reaction forward. We add excess olefin, we heat it, whatever we wait, we patient, and we can convert everything to the tertiary phosphine. And now I specifically draw this as a styrene derivative and we did a lot of work with styrene derivatives to start with. The real question though is could we actually selectively make the secondary product because the secondary product is the one that is of more interest. It has the potential for additional chemistry and it's the one that says you have a little more finesse because you haven't actually had to force this thing into completion. And it turns out actually it works quite well. Mike was able to succeed at doing this in about 80% isolated yield. So not just in a measurable sense, but he was able to get his hands on this product in good conversions. And Mike went through these things and he identified a whole slew of styrenes. They all work well. We can talk about electronics and sterics and blah, blah, blah until people would, if they would like to, I assume not everybody would. So that's a table. The second table is the non-styrene derivative. So we worked on other alkenes. And I highlight one specific derivative. This is one hexine. And this is pretty special. The yield is terrible. And this is really bad. This is less than 50%. But there's nothing out there that does this reaction. Of all the catalysts that have been reported for all the hydrophosphonation, none of them can hydrophosphonate one hexine. And that's weird because it actually is this set of molecules, these very simple alkenes, alpha olefins with unactivating substituents on it. And it's a big hole in the chemistry and we've stumbled onto this. And so one of the areas that Christine has been working on is trying to figure out better why that is. Why do we do this chemistry that cannot be done by anything else? And so that is of a particular interest in it. It continues to allow us to ask interesting questions about this kind of reactivity. In the meantime, however, we've had some other successes. And so Christine in particular has been working on what's called double hydrophosphonation. So instead of doing two additions at phosphorus, doing two additions at the unsaturated substrate. So we're back to alkenes and we're using these internal alkenes, so that is two organic substituents, no hydrogens, and adding two phosphines to that, to make these diphosphinoethanes. And for Christine, this has worked quite well is that she can use substituents that have both aryl and alkyl and dialkyl substituents on the alkynes. So there's generality to this, I'm not gonna show another table. This is not an unknown transformation, but this is actually, this year's the third report of it. The first report comes from Nakazawa and coworkers who showed with iron they could do this reaction and make diphosphines as well. But what's important is actually how complementary these two systems are. That is the iron case, it's only terminal alkynes, whereas we're only internal alkynes. So we've covered the whole set of triple bond carbon. And Nakazawa's chemistry is exclusively with secondary phosphine. And I'll come back to this in a couple of minutes because it continues to be adventurous, but it's nice that this actually overlaps well. So in the process of these things, we understand this chemistry a little bit better than we did before, which is that it proceeds in the way that you might imagine. There's a single addition step. So we make the vinyl phosphine as the initial product of the reaction. And then the second phosphine comes in to make the diphosphine. So this is sequential and it makes sense. And in fact, we've had a lot of success isolating a whole family of vinyl phosphines from this very cleanly, very reliably. What's unusual for our chemistry and all of our chemistry's been thermal, that is we can heat things and make them react, but this is actually light dependent. And we've never had chemistry that's been specifically light dependent. And what's more interesting than that is that it's not high energy light dependent. It's basic ambient visible light with low energy light sources, which is also amusing. So in LED, we literally use LED bulbs and desk lamps and accelerate this process to make it go in a facile sense. So that's pretty fun. The whole rationale to make these kinds of molecules is that they can undergo further functionalization. That is, we could, oh sorry, the slow step, of course, is the second step, is that they can undergo further functionalization. And there is actually well-developed phosphorous chemistry. You don't need to reinvent the wheel to make these into chiral tertiary phosphines. Exactly the kinds of molecules that Knowles had used back in the 60s to make Aldopa. So that's the whole connection. The reason why we're doing this is that it provides us molecules that are of importance to other industries. We've started doing this chemistry, but man, it's a pain. And the real pain here is that you make, actually in this process, you don't just set the phosphorous as chiral centers. There's one, two, three, fours. You have two phosphorous and two carbons that get set at the same time. So we said, boy, that's really hard and irritating. So what would be better is if we could simplify this. And initially, we thought, oh, the same R's, substituents, but it doesn't really simplify things. We didn't change the number of chiral centers. We just said, if it weren't chiral, that would be good. And the way to solve that is to use acetylene. And surprisingly, although we can't work with terminal alkynes, acetylene is actually a viable substrate, and we're able to do the double hydrophosphonation on acetylene. And that was pretty good. And there's an unusual intermediate, and I show this just because it's a pretty fun molecule of the acetylene-bridged disarconium compound that is present in that catalysis. And much like with the original alkyne chemistry, it is an intermediate that is nonproductive, but it is something that is present. So I mentioned Nakazawa's chemistry, and I show that exact reaction here again. So the double hydrophosphonation of terminal arylalkynes with iron. And this is a thermal process as well. This is refluxing toluene, basically. And it makes this product. Now, Justin Baganow had been working on some other phosphorus-related chemistry using iron. So completely different catalysis. This is what we call alpha elimination. And he was delivering a phosphinidine equivalent to these unsaturated substrates to make various kinds of phosphols separate, although there's clear relationships. But what we were doing at the time was wondering how much does light play a role in this? And through those studies, and lacking in time to explain the detailed connection, what Justin's observed is, in fact, that using a precursor to this catalyst, and it's actually commercially available, very simple precursor to this catalyst, we can do Nakazawa's catalysis at ambient temperature in significantly less time, because in this case, we're simply irradiating. This is, again, a photo process versus a thermal process. So it's considerably more efficient. So there are advances to be made on the known reaction set that are also there. We've done a couple other things. I'm just going to highlight them quickly. So the one thing about these primary phosphines that I mentioned to you before is that, boy, howdy, they smell. Organophosphines are kind of stinky, in general, just saying. And they oxidize quite readily. So as phosphorus is phosphorus in its plus three oxidation state, it likes to go to phosphorus 5 in the presence of molecular oxygen. And that is such a favorable reaction that the heat of that reaction is enough to combust both the starting material and the products. Therefore, it is pyrophoric. So organophosphines, if you put them on the bench, or say primary organophosphines if you put them on the bench will immediately catch fire and smell bad. It's tough. We do it again. Anyway, so these are a part of a broader class of organophosphines that are, in fact, tolerant to oxygen. These are air stable phosphines. And because they're significantly larger, they potentially have less chemical reactivity, but also are more stable with respect to some other features as well. And so what we found, what Christine and colleagues have found, is that we can do these hydrophosphination catalysis with these air stable phosphines, primary phosphines, which actually expands the utility of this chemical reaction. John Stelmack, who's a recent graduate, was working on 10 catalysis. So again, changing the metal up and seeing are really unusual behaviors that the hydrophosphination catalysis would occur. But surprisingly, what would happen is we get competitive dehydro coupling, which never really happens with our other caliscus because dehydro coupling is so difficult for most of the other species that we investigate. So that's also an unusual observation. But in light of the hour, I will wrap things up. And so this is the reaction I was telling you about. This is it. Just hydrophosphination. So we're taking a pH bond. We're adding it across an unsaturated substrate. And whether that catalyst is iron or zirconium, it's a variety of kinds of advances, whether it be the type of substrate, the type of energy that we're using, the efficiency of those reactions, and ultimately the selectivity as well. So there's a lot of places that we're looking at and a lot of things that we're looking at doing this. But ultimately, this is pretty tough stuff. And the catalyst makes our lives easier. And so that's really, that's the punchline, is that we like to do synthesis. We like to make molecules in the catalysis. Makes it easier. And it allows us to have more fun doing it. So I mentioned here, I mentioned on the slides some of the folks that had done the phosphorus-based chemistry here is that the current group is largely an NSF-funded project. There have been a lot of people in the lab that have worked on a lot of different things. I actually started making the slide of all the grad students, the undergrads, the postdocs. And it was illegible, so I didn't make it. It's not because they're not here to see it, which is also kind of good, I guess. But I do appreciate working with everybody that I've worked with over the years. I have a great time doing it. This is a wonderful place to be. I am very grateful that you all came and I will happily answer questions. Thank you.