Research

Research interests of the Ellis group have focused on investigation of the relatively unexplored chemistry of the elements with the objective of creating new and/or useful molecules of fundamental interest. We view the entire periodic table as our playground and delight in the discovery of previously unknown classes of compounds containing elements in rare or unprecedented oxidation states and/or ligand environments, i.e., "textbook molecules." One special emphasis in current research involves studies on the reactions of polycyclic aromatic hydrocarbon or polyarene radical anions with transition metal precursors as a unique route to new types of pure or homoleptic polyarenemetal species, especially anionic ones. Prior to our entry into this area, virtually nothing was known about polyarenemetalate anions. Even their existence was in doubt before our 1994 Angewandte Chemie report on tris(η4-naphthalene)zirconate(2-), the first example of a tris(arene) complex of a d-block element. Polyarenemetalates have proven to be exciting reagents for the exploration of the chemistry of low-valent metals, owing to the substantial lability of the coordinated polyarenes in these compounds in numerous reactions. For example, tris(naphthalene)titanate(2-) was reported in Science in 2002 to react with white phosphorus, P4, to afford the only known "all-inorganic" metallocene, [Ti(η-P5)2]2-. Also, bis(anthracene)ferrate(1-) was documented in 2007 to be the first available storable source of the atomic Fe- ion in its reaction with 1,3-butadiene to provide a previously unknown pure butadiene iron complex, [Fe(η4-C4H6)2]-. Our most recent triumph, and one we are quite proud of, is in the synthesis and characterization of tris(naphthalene)hafnate(2-), the first hydrocarbon-stabilized complex to contain the very electropositive element hafnium in a negative oxidation state, Hf(II-) (http://dx.doi.org/10.1002/anie.200802780). As depicted below in the scheme, this substance functions as the first available source of atomic Hf2- in its reactions with anthracene and 1,3,5,7-cyclooctatetraene. 

Amazingly, homoleptic polyarenemetalates have only been documented for the elements Ti, Zr, Hf, Nb, Ta, Fe and Co to date (all from research in our laboratory), so the "sky is really the limit" in the investigation of related chemistry of other d-block metals, particularly those for which zero- or negative-valent complexes are either unknown or extremely rare. Plans are also in place for extension of this research to 4f-block metals, as well as certain main group metals and metalloids, and promise to afford particularly exciting results in new virtually unexplored low-valent systems.