SYNTHESIS AND STEREOCHEMISTRY OF THE FIRST CHIRAL (IMIDAZOLINYLIDENE)PALLADIUM(II) AND (TRIAZOLINYLIDENE)PALLADIUM(II) COMPLEXES

The reaction of three equiv, of a chiral imidazolium or triazolium per chlorate with one equiv, of Pd(OAc)(2), an excess of NaI and a base le ads to the corresponding chiral dicarbene-diiodopalladium(II) complexe s in chemical yields up to 98% and with the trans isomer as the major product (1, 2). If only one equiv. of the imidazolium or triazolium pe rchlorate is used, then dinuclear complexes with bridging iodine atoms are formed (3, 4, chemical yield 92-94 %). The latter can add Lewis b asic ligands, e.g, amines, phosphanes or other carbenes, to give monon uclear complexes with one carbene ligand coordinated to the PdI2 fragm ent (5, 6). Preliminary test experiments with these Pd(II) complexes a s catalysts for an enantioselective Heck-type reaction have been carri ed out.