Trifluoromethyl Complexes of Osmium(II) by Halogen Oxidation of an Osmium(0) Difluorocarbene Compound and the Structures of Os(CF₃)Cl₂(NO)(PPh₃)₂ and Os(CF₃)Cl_0.666I_1.333(NO)(PPh₃)₂

Abstract

Oxidation of Os(=CF₂) Cl (NO)(PPh₃)₂ by the halogens X₂(X = Cl , I), unexpectedly yields the trifluoromethyl complexes Os(CF₃)CIX(NO)(PPh₃)₂ in a low yield which is improved by the addition of LiF to the reaction mixture. The crystal structures of both Os(CF₃)Cl₂(NO)(PPh₃)₂ and Os(CF₃)Cl_0.666I_1.333(NO)(PPh₃)₂ have been determined. Crystals of Os(CF₃)Cl₂(NO)(PPh₃)₂ are monoclinic, a 24.543(5), b 9.685(1), c 15.951(1) Ǻ, β 115.81(1)°, Z 4, space group C2/c. Least-squares refinement has returned a residual, R, of 0.048 for 3371 observed reflections. The molecule lies on a twofold axis, with the CF₃-group and one Cl-ligand statistically interchanged. Crystals of Os(CF₃)Cl_0.666 I_1.333(NO)(PPh₃)₂ are monoclinic, a 24.562(4), b 9.690(1), c 16.385(2) Ǻ, β 115.51(1)°, Z 4, space group C2/c. Least-squares refinement has returned a residual of 0.058 for 4087 observed reflections. This crystal structure is best described as a 2 : 1 mixture of Os(CF₃) ClI (NO)(PPh₃)₂ and s(CF₃)I₂(NO)(PPh₃)₂, (both with CF₃ and I statistically disordered about the diad axis, as above). Both complexes exhibit octahedral coordination geometries.