Replacement of hydrido-ligands in triruthenium complexes by triphenylphosphinegold groups. Crystal structures of [AuRu3(µ-COMe)(CO)10(PPh3)], [AuRu3(µ-H)2(µ3-COMe)(CO)9(PPh3)], and [Au3Ru3(µ3-COMe)(CO)9(PPh3)3]

Abstract

The compound [AuMe(PPh₃)] reacts under mild conditions (diethyl ether, ambient temperatures) with the compounds [M₃(µ-H)(µ-COMe)(CO)₁₀] and [Ru₃(µ-H)₃(µ₃-COMe)(CO)₉] to give the complexes [AuM₃(µ-COMe)(CO)₁₀(PPh₃)][M = Fe (1) or Ru (2)], [AuRu₃(µ-H)₂(µ₃-COMe)(CO)₉(PPh₃)](3), [Au₂Ru₃(µ-H)(µ₃-COMe)(CO)₉(PPh₃)₂](4), and [Au₃Ru₃(µ₃-COMe)(CO)₉(PPh₃)₃](5). Spectroscopic properties of the new species are reported and discussed, and the structures of (2), (3), and (5) have been established by X-ray diffraction studies. The structure of [AuRu₃(µ-COMe)(CO)₁₀(PPh₃)](2) can be regarded as a molecule of [Ru₃(µ-H)(µ-COMe)(CO)₁₀] in which the bridging hydrido-ligand is replaced by a bridging AuPPh₃ group, thus producing a ‘butterfly’ metal atom core (interplanar angle 117°) with the gold atom occupying a ‘wing-tip’ site. The COMe ligand bridges the body of the butterfly on the convex side. The Au–Ru bonds [2.760(2) and 2.762(2)Å] are ca. 0.1 Å shorter than the non-bridged Ru–Ru bonds [2.845(2) and 2.839(3)Å] but the bridged Ru–Ru bond is significantly longer at 2.879(2)Å. Crystals of (2) are triclinic, space group P, and the asymmetric unit comprises two molecules of complex. The structure has been refined to R 0.075 for 4 868 intensities measured to 20 = 40° at 220 K. In [AuRu₃(µ-H)₂(µ₃-COMe)(CO)₉(PPh₃)](3) the carbyne ligand triply bridges an equilateral triangle [Ru–Ru 2.865(2)–2.879(2)Å] of ruthenium atoms, while on the opposite side of the triangle there are two edge-bridging hydrido-ligands and one edge-bridging AuPPh₃ group. Each ruthenium atom carries three terminal carbonyl ligands, giving octahedral co-ordination if the Ru–Ru bonds are ignored. The molecule has approximate C_s symmetry, not required crystallographically. The structure is triclinic, space group P, and has been refined to R 0.042 for 3 247 intensities measured to 2θ= 45° at 293 K. The complex [Au₃Ru₃(µ₃-COMe)(CO)₉(PPh₃)₃](5) crystallises with half a molecule of CH₂Cl₂ per molecule of (5) incorporated into the crystals. Again the carbyne ligand triply bridges a near-equilateral triangle of Ru atoms [Ru–Ru 2.895(3)–2.929(2)Å], but on the opposite side of this triangle one gold atom is co-ordinated to form a tetrahedron [Au–Ru 2.818(2), 2.825(2), and 2.987(2)Å]. The two faces of this tetrahedron adjacent to the long Au–Ru bond are each further triply bridged by AuPPh₃ ligands. The two Au–Au distances in this bicapped tetrahedral structure are 2.930(1) and 3.010(1)Å; the difference between these probably arises from the packing of the bulky triphenylphosphine ligands. Crystals of (5) are monoclinic, space group P2₁/n, and the structure has been refined to R 0.050 for 4 279 intensities measured to 2θ= 45° at 293 K.