The synthesis of some bi- and tri-metallic clusters containing rhodium; X-ray crystal structures of [MoRh3(µ3-CO)3(CO)3(PPh3)3(η-C5H5)]·CH2Cl2and [MoRhPt(µ-CO)2(µ-PPh2)(µ-1-σ:1–2-η-C6H5)-(PPh3)2(η-C5H5)

Abstract

Treatment of the complexes [MRh(µ-CO)2(CO)(PPh3)2(η-C5H5)](M = Mo or W) with [Fe2(CO)9] in tetrahydrofuran at room temperature affords the tetranuclear 56 valence-electron cluster compounds [MRh3(µ3-CO)3(CO)3(PPh3)3(η-C5H5)]. The structure of the molybdenumtrirhodium species, which crystallises with a molecule of CH2Cl2, has been established by a single-crystal X-ray diffraction study. The metal-atom core approximates to a regular tetrahedron, with Rh–Rh separations 2.710(1)–2.729(1)A, and Mo–Rh distances 2.764(1)–2.778(1)A. The molybdenum atom carries the η-C5H5 ligand, and a CO and a PPh3 group are attached to each rhodium atom. These terminal carbonyl ligands are directed below the Rh3 triangle, and the three ligated phosphorus atoms lie above. In addition, a CO group triply bridges each of the MoRh2 faces of the cluster. The reaction between [MoRh(µ-CO)2(CO)(PPh3)2(η-C5H5)] and [Pt(C2H4)(PPh3)2] in tetrahydrofuran at 50 °C yields the complexes [MoPt(µ-PPh2)(CO)2(PPh3)2(η-C5H5)] and [MoRhPt(µ-CO)2(µ-PPh2)(µ-1-σ:1–2-η-C6H5)(PPh3)2(η-C5H5)]. The structure of the 44 valence-electron trimetal compound has been determined by X-ray diffraction. The three metal atoms form a triangle [Mo–Pt 2.958(1), Mo–Rh 2.619(1), and Pt–Rh 2.662(1)A], the molybdenum atom carries the η-C5H5 ligand, and the platinum and rhodium atoms are co-ordinated by PPh3 groups. The three edges of the metal triangle are bridged; the Mo–Rh edge by two CO ligands, the Mo–Pt by PPh2, and the Rh–Pt by a C6H5 group. One carbon of the phenyl group is σ bonded to platinum and together with an adjacent carbon is η2-co-ordinated to the rhodium. The n.m.r. data (1H, 13C-{1H}, and 31P-{1H}) for the new compounds are reported and discussed.