UNUSUAL STEREOCHEMICAL RIGIDITY IN 7-COORDINATION - SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF REH2(SIPH3)(CO)(PME2PH)3, REH2(SNPH3)(CO)(PME2PH)3

Reaction of ReH3(CO)(PMe2Ph)3(1) with Ph3SiH and Ph3SnH in refluxing THF leads to the formation of ReH2(EPh3)-(CO)(PMe2Ph)3(E = Si (2), Sn (3)). The solution spectroscopic data are consistent with the formulation of 2 and 3 as seven-coordinate with no H⋯H or Si⋯H interactions, but they are stereochemically rigid on the NMR time scale even at elevated temperatures, which is unusual for seven-coordinate complexes containing only monodentate ligands. Compound 2 has been structurally characterized by single-crystal X-ray crystallography in solvated and unsolvated forms. Crystal data for 2: monoclinic, space group p21, a = 9.958 (3) Å, b = 18.268 (6) Å, c = 12.175 (2) Å, β = 112.47(2)°, ν = 2047 (2) Å3, and Z = 2. Crystal data for 2 THF: monoclinic, space group P21/c, a = 15.341 (2) Å, b = 15.178 (2) Å, c = 19.074 (1) Å, β = 93.055 (8)°, ν = 4435.0 (7) Å3, and Z = 4. Unexpected distortions from standard seven-coordination polyhedra are present in both forms, and possible reasons are discussed. © 1990, American Chemical Society. All rights reserved.