NIOBIUM-CENTERED C-C COUPLING OF ISONITRILES

The complexes [NbI2(CNtBu)(6)]I (1), [NbI2(CNtBu)(4)(tBuNHC=CNHtBu)]I (2), and cis-[NbI(CO)(2)(CNR)(2)dppe] (R = tBu (3a), Cy (3b)), have be en prepared by oxidation of [Nb(CO)(6)(]-) with iodine in the presence of isonitrile either in a direct reaction (1 and 2) or, in the case o f 3, by substitution in the intermediate [NbI(CO)(4)dppe]. While 1 and 3 are generated in absolute THF, 2 forms in moist THF. The X-ray stru cture analysis of 1 . THF, 2, and 3b toluene reveals trigonal-prismati c basic structures with the iodines capping tetragonal faces. 1 and 3b exhibit interatomic C ... C distances sufficiently close to enable C- C coupling. The relevance of the coupling product 2 for reductive C-C coupling mediated by low-valent niobium is discussed.