Assessing the Metal-Metal Interactions in a Series of Heterobimetallic Nb/M Complexes (M = Fe, Co, Ni, Cu) and Their
Brett A Barden1, Gursu Culcu2, Jeremy P Krogman2
1Department of Chemistry and Biochemistry , The Ohio State University , 100 West 18th Avenue , Columbus , Ohio 43210 , United States.
Abstract:
A one-pot synthetic procedure for a series of bimetallic Nb/M complexes, Cl-Nb( iPrNPPh2)3M-X (M = Fe (2), Ni (4), Cu (5)), is described. A similar procedure aimed at synthesizing a Nb/Co analogue instead affords iPrN═Nb( iPrNPPh2)2(μ-PPh2)Co-I (3) through cleavage of one phosphinoamide P-N bond under reducing conditions. Complexes 4 and 5 are found to have short Nb-M distances, corresponding to unusual metal-metal bonds between Nb and these first row transition metals. For comparison, a series of heterobimetallic O≡Nb( iPrNPPh2)3M-X complexes (M = Fe (7), Co (8), Ni (9), Cu (10)) was synthesized. In these complexes, the NbV center is engaged in sufficient π-bonding to the terminal oxo ligand to remove the driving force for direct metal-metal interactions. A comparison of the cyclic voltammograms of 2 and 4-10 reveals that the presence of a second metal shifts the redox potentials of both Nb and the late metal center anodically, even when direct metal-metal interactions are not present.
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