Metallated phosphites and related complexes and their catalytic application

Abstract

The orthometallation of triarylphosphite ligands at a palladium centre is described. The formation of the orthometallated palladium dimeric complex [{Pd(μ-Cl){P(OC6H2-2,6-tBu2)(OC6H3-2,4-tBu2)2}}2] 22 is reported and fully characterised by X-ray, 31P NMR and microanalysis. Complex 22 was found to be an active catalyst in the Heck, Suzuki and Stille coupling reactions. It is an extremely active catalyst in the Heck arylation of alkenes, with turnover numbers of up to 5,750,000 (mol product.mol Pd-1) and turnover frequencies of up to nearly 300,000 (mol product.mol Pd-1.h-1), amongst the highest reported to date. Complex 22 is also an extremely active catalyst in biaryl coupling reactions, giving unprecedented turnover numbers of up to 1,000,000 (mol product.mol Pd-1) and turnover frequencies of nearly 900,000 (mol product.mol Pd-1.h-1) in the Suzuki reaction and turnover numbers of up to 830,000 (mol product.mol Pd-1) in the Stille reaction.