Syntheses, structures, and bonding of heteropentametallic clusters [MCo3(CO)12{µ3-M′(EPh3)}](M = Fe or Ru; M′= Cu or Au; E = P or As): X-ray crystal structures of [RuCo3(CO)12{µ3-M′(PPh3)}](M′= Cu or Au)

Abstract

The cluster anions [MCo₃(CO)₁₂]^–[M = Fe (1) or Ru (2)] react with [{Cu(PPh₃)Cl}₄] in toluene to give the neutral pentametallic clusters [FeCo₃(CO)₁₂{µ₃-Cu(PPh₃)}](3) and [RuCo₃(CO)₁₂{µ₃-Cu(PPh₃)}](4). The latter two products react with PPh₃ to give the ionic cluster species [Cu(PPh₃)₃][MCo₃(CO)₁₂]. The pentametallic cluster [RuCo₃(CO)₁₂{µ₃-Au(PPh₃)}](5), obtained by reaction of (2) with Au(PPh₃)Cl in diethyl ether-toluene, also reacts with PPh₃ to give [Au(PPh₃)₂][RuCo₃(CO)₁₂]. The structures of (4) and (5) have been determined by X-ray methods. Crystals of (4) are monoclinic, space group P 2₁/m, with Z= 2 in a unit cell of dimensions a= 9.122(3), b= 15.010(6), c= 12.580(7)Å, and β= 107.86(3)°. Crystals of (5) are monoclinic, space group P2₁/c, with Z= 4 in a unit cell of dimensions a= 8.921 (3), b= 14.165(2), c= 26.72(1)Å, and β= 91.95(4)°. The structures have been solved from diffractometer data by Patterson and Fourier methods and refined by full-matrix least-squares to R= 0.049 and 0.058 for 1 329 and 1 994 observed reflections, respectively. Both structures consist of a trigonal bipyramid of metal atoms with the cobalt atoms occupying the triangular equatorial plane and the copper or gold and ruthenium atoms situated at the apices. Three carbonyl groups bridge the Co–Co edges; the other nine are terminal, three attached to the Ru atom and two to each Co atom. Similarities in the bonding relationships of (4) and (5) are analyzed and rationalized through extended Hückel calculations.