Trichlorogermyl complexes of molybdenum and tungsten bearing cyclopentadienyl ligands: Synthesis, structure and isomerization studies

Abstract

Molybdenum and tungsten trichlorogermyl complexes of the type cis-( η 5-C 5R 5)M(CO) 2 (PMe 3) GeCl 3 ( 2b-2d) ( 2 b: M = W; R = H ; 2 c: M = Mo; R = Me ; 2 d: M = W; R = Me ) were obtained by the stereoselective insertion reaction of GeCl 2 into the metal-chlorine bond of cis-( η 5-C 5R 5)M(CO) 2(PMe 3)Cl ( 1b-1d). Simultaneous thermal analysis (TG-DTA) of 2b-2d revealed an exothermic solid-state isomerization of 2b-2d to trans-( η 5-C 5R 5)M(CO) 2(PMe 3)GeCl 3 ( 3b-3d) and the thermoanalytical results were used to prepare the trans isomers 3b-3d in large scale. In comparison, the trichlorogermyl complex cis-CpW(CO) 2(CNEt)GeCl 3 ( 5) was found to undergo an endothermic isomerization in the melt to afford a mixture of 5 and trans-CpW(CO) 2(CNEt)GeCl 3 ( 6) in a 1:1.2 ratio. The complexes 2b-2d, 3b-3d and 6 were fully characterized and the solid-state structures of the isomers 2d and 3d were determined by single-crystal X-ray diffraction analyses.