Stoichiometric CO Bond Oxidative Addition of Benzophenone by a Discrete Radical Intermediate To Form a Cobalt(I) Carbene

• Published in: Journal of the American Chemical Society Vol. 135; no. 16; pp. 6018 - 6021
• Main Authors: Marquard, Seth L, Bezpalko, Mark W, Foxman, Bruce M, Thomas, Christine M
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 24-04-2013
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja4022683

Single electron transfer from the ZrIIICo0 heterobimetallic complex (THF)Zr(MesNP i Pr2)3Co–N2 (1) to benzophenone was previously shown to result in the isobenzopinacol product [(Ph2CO)Zr(MesNP i Pr2)3Co–N2]2 (2) via coupling of two ketyl radicals. In this work, thermolysis of 2 in an attempt to favor a monomeric ketyl radical species unexpectedly led to cleavage of the C–O bond to generate a Zr/Co μ-oxo species featuring an unusual terminal CoCPh2 carbene linkage, (η2-MesNP i Pr2)Zr(μ-O)(MesNP i Pr2)2CoCPh2 (3). This complex was characterized structurally and spectroscopically, and its electronic structure is discussed in the context of density functional theory calculations. Complex 3 was also shown to be active toward carbene group transfer (cyclopropanation), and silane addition to 3 leads to PhSiH2O–Zr(MesNP i Pr2)3Co–N2 (5) via a proposed Co–alkyl bond homolysis route.