Preparation and reactivity of halide-bridged binuclear carbonyl manganese and rhenium anions, [M2(µ-X)(CO)8–2n{(EtO)2POP(OEt)2}n]–(X = halide; M = Mn, n= 1 or 2; M = Re, n= 1). X-Ray crystal structure of [Mn2Au(µ-Br)(CO)6–(µ-tedip)(PPh3)

Abstract

Reactions of bis halide-bridged carbonyl compounds of the type [Mn2(µ-X)(CO)8–2n(µ-L–L)n][n= 1 or 2, M = Mn, L–L =(EtO)2POP(OEt)2(tedip), X = Br or I; n= 1, M = Re, L–L = tedip, X = Br; n= 1, M = Mn, L–L = Ph2PCH2PPh2, X = Cl] with excess of sodium amalgam afforded the corresponding binuclear carbonyl metalates of general formula [M2(µ-X)(CO)8–2π(µ-L–L)n]– as Na+ salts. Protonation of these anionic species gave the corresponding µ- hydrido complexes [M2(µ-X)(µ-H)(CO)8–2n(µ-L–L)n] and reaction with [{M′Cl(PPh3)}n](n=4, M′= Cu or Ag; n= 1, M′= Au) afforded the triangular mixed-metal clusters [M2M′(µ-Br)(CO)8–2n(µ-tedip)n–(PPh3)](M = Mn, n= 1 or 2; M = Re, n= 1). The compounds were characterized by i.r., 1H and 31P-{1H} n.m.r. spectroscopy, and the crystal structure of [Mn2Au(µ-Br)(CO)6(µ-tedip)(PPh3)] was determined by X-ray diffraction methods. Crystals are monoclinic, space group P21/a with Z= 4 in a unit cell of dimensions a= 18.581(8), b= 17.652(6), c= 12.326(6)A, and β= 104.42(3)°. The structure has been solved from diffractometer data by direct and Fourier methods and refined by full-matrix least squares to R= 0.058 for 3 812 observed reflections. The structure shows two Mn atoms at a distance of 3.090(3)A, bridged by a gold atom from the Au(PPh3) group [Mn–Au 2.640(3) and 2.679(3)A], a bromine atom [Mn–Br 2.458(3) and 2.477(3)A], and by a tedip ligand through the two P atoms. The slightly distorted octahedral co-ordination around each Mn atom is completed by three carbon atoms.