SYNTHESIS, REACTIVITY, AND CHARACTERIZATION OF THE 1ST DONOR-STABILIZED SILYLENE COMPLEXES OF OSMIUM MESO-TETRA-PARA-TOLYLPORPHYRIN (TTP)OS=SIR2.THF (R = ME, ET, ISO-PR) AND THE MOLECULAR-STRUCTURE OF (TTP)OS=SIET2.2THF

The preparation and characterization of the first donor-stabilized silylene complexes of osmium meso-tetra-p-tolylporphyrin are described. The silyene complex (TTP)Os = SiMe2.THF (1.THF) is prepared by the reaction of [Os(TTP)]2 with hexamethylsilacyclopropane. Treating K2[Os(TTP)] with Cl2SiR2 also generates the silylene complexes (TTP)Os = SiR2.THF [R = Me (1.THF), Et (2.THF), (i)Pr (3.THF)]. H-1 NMR spectroscopy indicates that, in solution, one molecule of THF is coordinated to the silicon in all of these complexes. This has been verified by 2D-NOESY experiments. In 2.THF, the methylene protons are diastereotopic, indicating that the silicon is pyramidalized. Addition of 1 equiv of pyridine to 1.THF or 2.THF replaces the THF on silicon with pyridine. Coordination of pyridine to silicon was also confirmed by a 2D-NOESY experiment. The structure of 2.THF was determined by a single-crystal X-ray diffraction experiment. The diethyl complex 2.2THF crystallizes with two additional THF molecules as solvates in the monoclinic space group P2(1)/c with a = 21.649 (5) angstrom, b = 13.829 (3) angstrom, c = 19.526 (3) angstrom, beta = 98.08 (2)-degrees, V = 5788 (4) angstrom 3, Z = 4, R = 5.0%, and R(w) = 5.7%. The Os-Si distance (2.325 (8) angstrom) is the shortest observed to date. Other metrical parameters of this complex are discussed.