Synthesis, Structure, and Reactivity of Four-, Five-, and Six-Coordinate Ruthenium Carbyne Complexes

Abstract

Square-planar carbyne complexes of the form Ru(⋮CR)(PCy3)2X (X = F, Cl, Br, I, O3SCF3) are prepared by net dehydrohalogenation of the Grubbs catalysts Ru(CHR)(PCy3)2Cl2 followed by substitution of the chloride ligand (when X ≠ Cl). The dehydrohalogenation can be effected in one step (R = n-Bu, Ph, p-C6H4Me) by Ge(CH[SiMe3]2)2 or in two steps via treatment with excess aryloxide such as NaO-p-C6H4-t-Bu followed by SnCl2. The latter route gives greater yields but is more restricted in scope. Addition of HCl (1 equiv) to Ru(⋮CR)(PCy3)2X (X = Cl, Br, I) affords Ru(CHR)(PCy3)2ClX; those with mixed halide ligand sets undergo rapid halide exchange in solution. Upon treatment with the appropriate oxidant, each Ru(⋮C-p-C6H4Me)(PCy3)2X complex undergoes two-electron oxidation. Oxidation of Ru(⋮C-p-C6H4Me)(PCy3)2X (X = F, Cl, Br, I) by XeF2, C2Cl6, Br2, and I2, respectively, yields either six-coordinate bis-phosphine complexes Ru(⋮C-p-C6H4Me)(PCy3)2X3 (X = F, Cl) or square-pyramidal mono-phosphine complexes Ru(⋮C-p-C...