Substitution and Reaction Chemistry of Cobalt Complexes Supported by [N2P2] Ligands

The coordination chemistry of mono- and divalent cobalt complexes supported by the monoanionic multidentate ligands, [N2P2] (where [N2P2] = tBuN((-))SiMe(2)N((CH2CH2PPr2)-Pr-i)(2)) and [N2P2tolyl] (where [N2P2tolyl] = MeC6H4N(-)SiMe2((CH2CH2PPr2)-Pr-i)(2)), is presented. The Co(II) halide complex [N2P2]Col (2) serves as a precursor to the alkyl, hydride, and amide species [N2P2]CoMe (3), [N2P2]CoCH2SiMe3 (4), [N2P2]CoH (5), [N2P2]CoNHPh (10), and [N2P2]CoNHC6H4Me (11). Reduction of 2 results in the formation of a stable, monomeric Co(I) species, [N2P2]Co (6). Compound 6 can be trapped with CO to form either [N2P2]Co(CO) (7) or [(BuN)-Bu-t(C=O)SiMe2N((CH2CH2PPr2)-Pr-i)(2)]CO(CO)(2) (8) depending on the number of equivalents of CO introduced. Compound 6 also serves as a precursor to transient Co(Ill) imido species. The Co(II) halide complex [N2P2tolyl]Col (16) is synthesized through an analogues reaction to that of 2. Reduction of 16 results in the formation of [N2P2tolyl]CO (17), and differences in the coordination and reaction chemistry of 6 and 17 are described.