Pd-pincer complexes containing six-membered rings that are more active allylation catalysts than five-membered ring analogues

A series of symmetric and non-symmetric PCP-pincer complexes have been prepared and an evaluation of their activity in catalytic allylic alkylation carried out. The X-ray crystallography and NMR spectroscopy data suggest that metallacycles containing one (or two) 6-membered rings are inherently more rigid than initially anticipated. The observed catalyst activity is found to increase as the metallacycle size increases from 5 to 6.