Research
4. Dinitrogen Sequestration and Functionalization.
Our group is currently assembling a series of low-valent complexes capable of activating, and ultimately cleaving the triple bond of N2. More specifically, we are particularity interested in uncovering active species and likely intermediates generated in the Mori reaction.1 Activating and incorporating nitrogen directly from N2 into organic molecules is our ultimate goal. Coordinatively unsaturated complexes of cobalt are expected to be inherently reactive and offer an ideal opportunity to study novel transformations which include the activation of inert substrates such as N2. For the latter type of reactions, the N2 adducts of cobalt are in general prepared via reduction reactions under atmospheric N2. However, speculation as to what the electron rich intermediate is in the absence of such a substrate (or a donor) has been only hinted to in the literature. One credible reason for the lack of isolable intermediates in the N2 fixation process could be likely attributed to ligand disproportionation or degradation reactions occurring without an added π-acceptor or trap. In our research group, we have been isolating reactive intermediates capable of sequestering N2 from the atmosphere. One specific project has been reduction studies of a square planar cobalt(II) species (PNP)CoCl (PNP = N[2-P(CHMe2)2-4-methylphenyl]2-) to afford neutral and dianionic dinitrogen adducts of Co as well as a dinuclear Co(I) diamond-core complex.2 The latter system has been demonstrated to be a three-coordinate Co(I) synthon as well as a key intermediate in the sequestration of atmospheric nitrogen, a step which appears to be reversible for this particular system (Figure shown).2
Selected References
1. Mori, etal. Angew. Chem. Int. Ed. 1998, 37, 636 and J. Am. Chem. Soc. 1998, 120, 7651.
2. Fout, A. R.; Basuli, F.; Fan, H.; Tomaszewski, J.; Huffman, J. C.; Baik, M.-H.; Mindiola, D. J. Angew. Chem. Int. Ed. 2006, 45, 3291-3295.