Synthesis, Structure, and Reactivity of Low-Spin Cobalt(II) Imido Complexes [(Me3P)3Co(NAr)]

Abstract

The reactions of [Co(PMe₃)₄] with the bulky organic azides, DippN₃ and DmpN₃ [Dipp, 2,6-diisopropylphenyl; Dmp, 2,6-di(2',4',6'-trimethylphenyl)phenyl], afforded the cobalt(II) terminal imido complexes [(Me₃P)₃Co(NAr)] (Ar = Dipp, 1; Dmp, 2). The cobalt imido complexes in their solid states show trigonal pyramidal coordination geometry and long Co-N(imido) separations (ca. 1.71 Å). Spectroscopic characterization and theoretical studies indicated their low-spin cobalt(II) nature. Reactivity studies on 1 revealed its nitrene-transfer reactions with PMe₃ and CO, the imido/oxo and imido/sulfido exchange reactions with PhCHO and CS₂, and the single-electron oxidation reaction by ferrocenium cation to form cobalt(III) imide.