PROPERTIES AND MOLECULAR-STRUCTURES OF OSMIUM(II) PORPHYRIN CARBENE COMPLEXES - (5,10,15,20-TETRA-P-TOLYLPORPHYRINATO)OSMIUM DI-P-TOLYLMETHYLIDENE AND (5,10,15,20-TETRA-P-TOLYLPORPHYRINATO)OSMIUM (TRIMETHYLSILYL)METHYLIDENE

The first molecular structures of two (porphyrinato)osmium(II) alkylid ene complexes are described. The carbene fragments of (5,10,15,20-tetr a-p-tolylporphyrinato)osmium (trimethylsilyl)methylidene (1) and (5,10 ,15,20-tetra-p-tolylporphyrinato)osmium di-p-tolylmethylidene (2) adop t different conformations in the solid state. With respect to the porp hyrin ring nitrogen atoms, a staggered conformation is found for the c omplex 1 carbene moiety (d(Os-C) = k79(2) angstrom, torsion angle phi = 23(1)-degrees). A similar conformation appears in complex 2 (d(Os-C) = 1.865(5) angstrom, torsion angle phi = 28.4(4)-degrees). The carben e fragments in the two molecular structures are distorted and do not p ossess ideal sp2 geometries. Complex 1 displays a large distortion wit h an Os-C-Si angle of 142(2)-degrees. The complex 2 carbene moiety has a C(Ar)-C-C(Ar) angle of 113.0(4)-degrees. Complex 1, C52H46N4OsSi-OC 4H8, crystallizes with a trans-coordinated molecule of THF as 1.THF in the monoclinic space group P2(1)/n with a = 13.954, (2) angstrom, b = 9.522(2) angstrom, c = 17.969(2) angstrom, beta = 101.42(1)-degrees, V = 2340.3(6) angstrom3, Z = 2, R1 = 0.0532, and wR2 = 0.1276. Complex 2, C63H50N4Os.OC4H8.C7H8.1/2OC4H8, crystallizes as a trans-THF adduct , 2.THF, in the monoclinic space group C2/c with a = 28.003(6) angstro m, b = 14.385(3) angstrom, c = 33.748(8) angstrom, beta = 114.51(2)-de grees, V = 12370(5) angstrom3, Z = 8, R1 = 0.0389, and wR2 = 0.1165. O ther metrical parameters and spectroscopic properties of these complex es are discussed.