Mixed-metal carbido carbonyl clusters. Part 3. Synthesis and structural characterization of [Rh6C(CO)15{Ag(NCMe)}2]·0.5MeOH, [Rh6C(CO)15{M-(PPh3)}2](M = Cu, Ag, or Au), and of the anion [Rh6C(CO)15{Au(PPh3)}]– as its PPh4+ salt

Abstract

The new mixed-metal carbido carbonyl clusters [Rh₆C(CO)₁₅{Ag(NCMe)}₂](1), [Rh₆C(CO)₁₅-{M(PPh₃)}₂][M = Ag (2), Cu (3), or Au (5)], and [Rh₆C(CO)₁₅{Au(PPh₃)}]^–(4) have been obtained by reaction in MeOH solution of [Rh₆C(CO)₁₅]^2– with AgBF₄(in the presence of MeCN), [{MCl(PPh₃)}₄](M = Cu or Ag), or [AuCl(PPh₃)]. Their molecular structures have been determined by single-crystal X-ray diffractometry: (1), monoclinic, space group C2/c, a= 18.110(3), b= 10.455(3), c= 20.553(4)Å, β= 125.99(1)°, and Z= 4; (2), triclinic, space group P, a= 11.397(3), b= 16.519(2), c= 16.879(3)Å, α= 116.07(1), β= 98.86(2), γ= 87.77(2)°, and Z= 2; (3), triclinic, space group P, a= 11.474(3), b= 16.012(9), c= 16.688(4)Å, α= 114.25(3), β= 97.82(2), γ= 89.59(4)°, and Z= 2; (4), monoclinic, space group P2₁/c, a= 23.009(3), b= 14.583(2), c= 36.726(4)Å, β= 97.54(1)°, Z= 8; (5), triclinic, space group P, a= 11.438(1), b= 16.330(7), c= 16.813(2)Å, α= 115.58(2), β= 98.68(1), γ= 88.37(2)°, and Z= 2. The structural analysis shows that the heterometallic ligands selectively cap one [(4)] or both [(1)–(3), (5)] triangular faces of the Rh₆ prismatic framework leaving the CO-ligand stereogeometry almost unaltered. Differences in the heterometallic interactions established by the various metal fragments are discussed.