Rhenium Carbonyl Complexes Containing Bridging SiPh₃ and SiPh₂ Ligands

The reaction of Re2(CO)8[μ-C(H)C(H)Bun](μ-H) (1) with Ph3SiH at 97 °C has yielded the three new compounds Re(CO)5(SiPh3) (5), Re2(CO)6(μ-η7-SiPh3)(μ-H) (6), and Re2(CO)8(μ-SiPh2)(SiPh3)(μ-H) (7) in 13, 10, and 30% yields, respectively. Compound 5 consists of a single rhenium atom with five carbonyl ligands and a terminal SiPh3 ligand. Compound 6 contains two rhenium atoms with a bridging SiPh3 ligand in which the silicon atom is bonded to one rhenium atom and one phenyl ring is η6-coordinated to the other rhenium atom. A hydrido ligand bridges the Re−Re bond. Compound 7 contains a Re2(CO)8 group with one bridging SiPh2 ligand and one terminal SiPh3 ligand. A hydrido ligand bridges one of the Re−Si bonds of the bridging SiPh2 ligand. The reaction of 1 with Ph3SiH at 125 °C yielded 5 and 6 and a new product, Re2(CO)8(μ-SiPh2)2 (8), which contains two bridging SiPh2 ligands, one on each side of the Re−Re single bond. Compound 7 is a precursor to 8. Compound 7 was converted into 8 at 125 °C via the elimination of benzene. All four new compounds were characterized by IR and 1H NMR spectroscopy and by single-crystal X-ray diffraction analysis.