Rhenium carbonyl complexes containing bridging SiPh3 and SiPh2 ligands

The reaction of Re-2(CO)(8)[u-C(H)C(H)Bu-n](mu-H) (1) with Ph3SiH at 97 degrees C has yielded the three new compounds Re(CO)(5)(SiPh3) (5), Re-2(CO)(6)(mu-eta(7)-SiPh3)(mu-H) (6), and Re-2(CO)(8)(mu-SiPh2)(SiPh3)(mu-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 eta(6)-coordinated to the other rhenium atom. A hydrido ligand bridges the Re-Re bond. Compound 7 contains a Re-2(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 with Ph3SiH at 125 degrees C yielded 5 and 6 and a new product, Re-2(CO)(8)(mu-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 degrees C via the elimination of benzene. All four new compounds were characterized by IR and H-1 NMR spectroscopy and by single-crystal X-ray diffraction analysis.