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) alkylidene complexes are described. The carbene fragments of (5,10,15,20-tetra-p-tolylporphyrinato)osmium (trimethylsily)methylidene (1) and (5,10,15,20-tetra-p-tolylporphyrinato)osmium di-p-tolylmethylidene (2) adopt different conformations in the solid state. With respect to the porphyrin ring nitrogen atoms, a staggered conformation is found for the complex 1 carbene moiety (d_os-c = 1.79(2) Å, torsion angle ϕ= 23(1)°). A similar conformation appears in complex 2 d_os-c = 1.865(5) Å, torsion angle ϕ;= 28.4(4)°). The carbene fragments in the two molecular structures are distorted and do not possess ideal sp² geometries. Complex 1 displays a large distortion with an Os─C─Si angle of 142(2)°. The complex 2 carbene moiety has a C_Ar ─C─C_Ar angle of 113.0(4)°. Complex 1, C₅₂H₄₆N₄OsSi·OC₄H₈, crystallizes with a transcoordinated molecule of THF as 1·THF in the monoclinic space group P2₁/n with a = 13.954(2) Å,b = 9.522(2) Å,c = 17.969(2) Å, β = 101.42(1)°, V = 2340.3(6) ų, Z = 2, R1 = 0.0532, and wR2 = 0.1276. Complex 2, C₆₃H₅₀N₄Os·OC₄H₈·C₇H₈·½OC₄H₈, crystallizes as a trans-THF adduct, 2·THF, in the monoclinic space group C2/c with a = 28.003(6) Å,b = 14.385(3) Å,c = 33.748(8) Å,β = 114.51(2)°, V = 12370(5) ų, Z = 8,R1 = 0.0389, and wR2 = 0.1165. Other metrical parameters and spectroscopic properties of these complexes are discussed.