Isocyanide Analogues of the Unsaturated Metal Carbonyls
Consider the highly reactive, mononuclear unsaturated metal carbonyls. For chemists like Cottrell Scholar Joshua Figueroa who are inspired by this grouping of materials, it can be a bit like pursuing will-o'-the-wisps. Metal carbonyls are compounds of carbon and oxygen atoms and various metals like molybdenum, iron and nickel. Normally they're used for metal plating of molds and other products. Depending on the number of "carbonyls"—a carbon monoxide (CO) molecule bound to the center of a metal atom—these molecules can be relatively stable. But when they possess fewer than normal metal-to-CO bonds, metal carbonyls become highly unstable. What fascinates chemists, though, is that they often function as good catalysts - compounds that trigger chemical reactions without themselves being used up in the process. The problem is, such instability makes these compounds impossible to isolate and difficult to study. The "bonds" chemists deal with are actually the shared orbits of electrons, tiny charged particles that flit around the much heavier nuclei—or centers—of a group of atoms (a group of atoms, of course, is called a molecule). So when Figueroa deals with compounds that are like the "mononuclear unsaturated metal carbonyls," he's studying molecules with fewer than normal bonds, and that makes them pretty hard to pin down - they tend to change quickly into other forms. "They've been observed by gas-phase or matrix isolation techniques," he says, referring elaborate laboratory procedures. "But the high reactivity has prevented any systematic study of their properties in the condensed phase" - that is, as solid matter. The reason it's important to study unsaturated molecules is because our modern world is hungry for innovation. If Figueroa can develop a better understanding of the unsaturated metal molecules, he believes they may prove useful as catalysts to create new materials. However, he has to first develop a way to ‘stabilize' inherently unstable molecules. To do this, Figueroa is making analogues of the unstable - or highly reactive - form of metal carbonyl molecules. In chemistry an analogue is a substance of similar molecular structure, although it may not have precisely the same properties as the original. When it comes to studying these elusive forms of metal carbonyls, though, at least it's a good start. He plans to tinker with molybdenum, iron, and nickel atoms by combining them with various customized isocyanides, molecules that mimic the properties of carbon monoxide but allow for protection of the unsaturated metal center against decomposition. In this way, he can isolate mimics of the mononuclear unsaturated metal carbonyls and use them to discover a new world of chemical reactivity.
Figueroa plans to involve undergraduate science students in his advanced research on metal carbonyls. He will also create an Undergraduate Computational Chemistry Research Opportunity program to serve as a resource for members of the UCSD community and a number of regional institutions lacking the infrastructure for computational chemistry. "I believe strongly that with adequate guidance, fundamental and contemporary aspects of chemistry can be taught together," Figueroa says. "By doing so, students at all levels can be productive members of the modern chemical enterprise." Figueroa is a strong believer in undergraduate research, and he is designing his education programs to reach out to Hispanic and other minority students in the San Diego region.