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)Å, 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)Å, bridged by a gold atom from the Au(PPh₃) group [Mn–Au 2.640(3) and 2.679(3)Å], a bromine atom [Mn–Br 2.458(3) and 2.477(3)Å], 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.