1 Dipartimento di Chimica Organica e Industriale, Centro Interdipartimentale C.I.S.I., Università degli Studi di Milano, Via G. Venezian 21, 20133 Milano, Italy.
Heteroleptic complexes, formed selectively by using a 1 : 1 combination of a sigma-donor and a pi-acceptor ligand, are involved in Rh- and Pd-catalysed reactions.