Facile Bismuth-Oxygen Bond Cleavage, C-H Activation, and Formation of a Monodentate Carbon-Bound Oxyaryl Dianion,(C_6H_2~tBu_2-3,5-O-4)~(2-)

摘要

The Bi~(3+)(N,C,N)-pincer complex Ar'BiCl_2 (1) [Ar'= 2,6-(Me_2NCH_2)_2C_6H_3], reacts with 2 equiv of KOC_6H_3Me_2-2,6 and KOC_6H_3~tPr_2-2,6 by ionic metathesis to form the anticipated bis(aryloxide) complexes Ar'Bi-(OC_6H_3Me_2-2,6)_2(2) and Ar'Bi(OC_6H_3~tPr_2-2,6)_2(3), respectively. However, the analogous reaction with 2 equiv of KOC_6H_3~tBu_2-2,6 forms HOC_6H_3~tBu_2-2,6 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(C_6H_2~tBu_2-3,5-O-4) (4), a product of para C—H bond activation. Structural, spectro-scopic, and DFT studies and a comparison with the proto-nated analogue [Ar'Bi(C_6H_2~tBu_2-3,5-OH-4)][BPh_4] (5), which was obtained by treatment of 4 with [HNEt_3] [BPh_4, 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.