Chelated η5-cyclopentadienyl-η-ethyl complexes of molybdenum and tungsten; molecular structure of W(η5-C5H4CH2-η-CH2)(CO)3

Molybdenum and tungsten complexes M(η5-C5H4CH2-η-CH2)(CO)3 (M=Mo, W) containing the bidentate ethyl-functionalized cyclopentadienyl ligand C5H4CH2CH2 have been synthesized by the reaction of spiro[2.4]hepta-4,6-diene with M(CO)3L3 (M=Mo; L3=1,3,5-C6H3Me3; M=W; L=NCMe). Reaction of the more stable tungsten complex with C6H5ICl2 and HBF4 gave complexes of the type W(η5-C5H4CH2CH2Cl)(CO)3Cl, W(η5-C5H4CH2CH3)(CO)3Cl and W(η5-C5H4CH2CH3)(CO)3(FBF3), respectively. The crystal structure of the tungsten tricarbonyl complex W(η5-C5H4CH2-η-CH2)(CO)3 has been determined by X-ray crystal diffraction on a single crystal and shows a four-legged piano stool structure.