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 5 R 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 5 R 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 5 R 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.