Palladium carbene complexes derived from imidazolium-linked ortho-cyclophanes

Reaction of imidazolium-linked ortho-cyclophanes with nickel(II) and pallad ium(II) salts in the presence of acetate base led to the formation of compl exes where a metal centre is bound by a pair of heterocyclic carbenes which themselves are part of a cyclophane skeleton. These cyclophane-metal compl exes have been characterised by NMR spectroscopy and (for five complexes) X -ray diffraction studies. The complexes are highly active as promoters of H eck and Suzuki couplings, with preliminary studies showing Heck reactions w ith turnover numbers approaching 10(7).