Printed in Great Britain . ISOCYANIDE , CARBENE , AND RELATED CHEMISTRY OF PALLADIUN ( II ) AND PLATINUN ( II )

Previous studies of the inter—relationships between isocyanide, imine, and carbene ligands on platinum(II), and of the stereochemistries of the latter two ligands will be briefly reviewed. Attempts to use these relationships to prepare platinum—olefin—carbene complexes have been unsuccessful but have led to an interesting ortho—metallated carbene derivative. The insertion of isocyanide into the Pd—CH3 gives the stable carbon—bonded mine ligand, e.g. Pd[C(CH3)=N(p—tolyl)1. The reaction of this ligand with dimethylacetylene dicarboxylate gives, as the major product, a complex containing the l—p—tolyl—3—oxo—2—E—carbomethoxymethylidene—2,3—dihydropyrrole ligand. The mechanism of its formation requires the occurrence of the enamine—ketimine tautornerism.