Structural\nand Reactivity Implications of Homo- and\nHeterobimetallic Co(II) Amides Prepared via Trans(amination) Reactions

Cobalt­(II) bis­(amides)­are widely\napplied in catalysis and material\nscience. Typically, they are prepared via salt metathesis, by reacting\na lithium amide with a CoX<sub>2</sub> (X = Cl, Br) salt, requiring,\nin many cases, the use of low temperatures and other solvents. This\nwork introduces an alternative approach, assessing the reactivity\nof classical Co­(II) amide [Co­(HMDS)<sub>2</sub>] (<b>1</b>)\n[HMDS = N­(SiMe<sub>3</sub>)<sub>2</sub>] and heterobimetallic [NaCo­(HMDS)<sub>3</sub>] (<b>6</b>) as precursors for trans­(amination) reactions\nwith DPA­(H) (2,2′-dipyridylamine), <i>N</i>-methylaniline,\nand piperidine. When reacted with the most acidic amine DPA­(H), both\nshowed polybasic behavior with excellent stoichiometric control according\nto the equivalents of DPA­(H) employed. Reactions with and piperidine\nled to an incomplete exchange of the HMDS groups present in <b>1</b>, even when an excess of the relevant amine is employed.\nContrastingly, when assessing the reactivity of sodium cobaltate <b>6</b> with these amines, kinetic activation of two (or three)\nof its HMDS-arms was observed, forming new heterobimetallic species\nwhich in all cases proved unstable, undergoing dissociation into their\nmonometallic components or a ligand redistribution process. The catalytic\npotential of the novel Co­(II) complexes was investigated for the hydrosilylation\nof acetophenone, finding that faster reaction rates and higher chemoselectivities\nwere achieved when using the heterobimetallic Na/Co systems.