AN UNPRECEDENTED BENDING OF A BRIDGING DIYNYL LIGAND IN AN UNSYMMETRICAL BINUCLEAR RHODIUM(I) COMPLEX

The reaction of [Rh(eta(2)-(OCCH3)-C-2)(PiPr(3))(2)] (2) with 2 equiv of phenylbutadiyne leads, in the presence of Na2CO3, to the formation of the five -coordinate bis(diynyl)hydridorhodium(III) complex [RhH(C=CC=CPh)(2)(PiPr(3))(2)] (3) While 3 reacts with pyridine to give the stable octahedral compound [RhH(C=CC=CPh)(2)(py)(PiPr(3))(2)] (4), On treatment with carbon monoxide the square-planar complex trans-[Rh(C=CC=CPh)(CO)(PiPr(3))(2)] (6) is formed via the spectroscopically characterized 1:1 adduct 5 as a labile intermediate, Compound 6, which has also been prepared from [Rh(eta(3)-CH2C6H5)(PiPr(3))(2)] (7), CO, and phenylbutadiyne, reacts with [RhCl(PiPr(3))(2)](n) (1) to yield the binuclear complex [Rh(CO)(PiPr(3))(2)(eta(1),eta(2)-C=CC=CPh)-RhCl(PiPr(3))(2)] (8). The X-ray structural analysis of 8 (triclinic space group P1 (No, 2) with a 12.460(2) Angstrom, b = 13.954(2) Angstrom, c = 16.431(2) Angstrom, alpha = 97.98(1)degrees, beta = 91.47(1)degrees, gamma = 109.61(1)degrees, V = 2657(1) Angstrom(3), and Z = 2) reveals a square-planar coordination around each of the metal centers which are bridged by a strongly bent diynyl ligand. The reaction of 1 with phenylbutadiyne leads, via the isomeric diyne and diynyl hydride species 9 and 10 as intermediates, to the alkynyl-substituted vinylidenerhodium(I) complex trans-[RhCl-(=C=CHC=CPh)(PiPr(3))(2)] (11). In the presence of pyridine the diynyl(hydrido)rhodium derivative [RhH(C=CC=CPh)Cl(py)(PiPr(3))(2)] (12) is obtained.