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Facile Bismuth−Oxygen Bond Cleavage, C−H Activation, and Formation of a Monodentate Carbon-Bound Oxyaryl Dianion, (C6H2tBu2-3,5-O-4)2−

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journal contribution
posted on 13.04.2011, 00:00 by Ian J. Casely, Joseph W. Ziller, Ming Fang, Filipp Furche, William J. Evans
The Bi3+ (N,C,N)-pincer complex Ar′BiCl2 (1) [Ar′ = 2,6-(Me2NCH2)2C6H3], reacts with 2 equiv of KOC6H3Me2-2,6 and KOC6H3iPr2-2,6 by ionic metathesis to form the anticipated bis(aryloxide) complexes Ar′Bi(OC6H3Me2-2,6)2 (2) and Ar′Bi(OC6H3iPr2-2,6)2 (3), respectively. However, the analogous reaction with 2 equiv of KOC6H3tBu2-2,6 forms HOC6H3tBu2-2,6 and a dark-orange complex containing only one aryloxide-derived ligand bound via a Bi−C and not a Bi−O linkage. This complex is formulated as Ar′Bi(C6H2tBu2-3,5-O-4) (4), a product of para C−H bond activation. Structural, spectroscopic, and DFT studies and a comparison with the protonated analogue [Ar′Bi(C6H2tBu2-3,5-OH-4)][BPh4] (5), which was obtained by treatment of 4 with [HNEt3][BPh4], suggest that 4 contains an oxyaryl dianion. Complex 4 represents a fully characterizable product of a bismuth-mediated C−H activation and rearrangement of the type postulated in catalytic SOHIO processes.