BIS(TRIISOPROPYLARSANE)RHODIUM(I) AND BIS(TRIISOPROPYLSTIBANE)RHODIUM(I) COMPLEXES WITH ISONITRILES OLEFINS, ALKYNES AND DIYNES AS LIGANDS

The synthesis of a series of monomeric rhodium(I) complexes of general composition trans-[RhCl(L)(AsiPr(3))(2)] and trans-[RhCl(L)(SbiPr(3))(2)] is reported. All compounds are prepared by displacement of the ethene ligand in trans-[RhCl(C2H4)(EiPr(3))(2)] (1: E=As; 2: E=Sb) by isocyanides CNR, alpha,beta-unsaturated carbonyl compounds CH2=CHO(=O)R, alkynes RC=CR' and diynes RC=C-C=CR. The isolated complexes 3-21 have been characterized by elemental analysis, IR and NMR spectroscopy, and in the case of trans-[RhCl(CNMe)(SbiPr(3))(2)] (5) by X-ray crystal structure determination. The bis(triisopropylstibane)rhodium compound 2 reacts with HC=CR (R=Ph, CO(2)Me, tBu) not to give the expected vinylidene complexes trans-[RhCl(=C=CHRXSbiPr(3))(2)] but instead catalyzes the formation of the corresponding E-enynes RCH=CHC=CR. The mechanism of this stereoselective dimerization process will be discussed.