TRICHLOROGERMYL COMPLEXES OF MOLYBDENUM AND TUNGSTEN BEARING CYCLOPENTADIENYL LIGANDS - SYNTHESIS, STRUCTURE AND ISOMERIZATION STUDIES

Molybdenum and tungsten trichlorogermyl complexes of the type cis-(eta (5)-C5R5)M(CO)(2) (PMe3) GeCl3 (2b-2d) (2b: M = W; R = H; 2c: M = Mo; R = Me; 2d: M = W; R = Me) were obtained by the stereoselective insert ion reaction of GeCl2 into the metal-chlorine bond of cis-(eta(5)-C5R5 )M(CO)(2)(PMe3)Cl (1b-1d). Simultaneous thermal analysis (TG-DTA) of 2 b-2d revealed an exothermic solid-state isomerization of 2b-2d to tran s-(eta(5)-C5R5)M(CO)(2)(PMe3)GeCl3 (3b-3d) and the thermoanalytical re sults were used to prepare the trans isomers 3b-3d in large scale. In comparison, the trichlorogermyl complex cis-CpW(CO)(2)(CNEt)GeCl3 (5) was found to undergo an endothermic isomerization in the melt to affor d a mixture of 5 and trans-CpW(CO)(2)(CNEt)GeCl3 (6) in a 1:1.2 ratio. The complexes 2b-2d, 3b-3d and 6 were fully characterized and the sol id-state structures of the isomers 2d and 3d were determined by single -crystal X-ray diffraction analyses. (C) 1998 Elsevier Science Ltd. Al l rights reserved.