Isonitril-substituierte Halbsandwich-Komplexe von Wolfram(IV) / Isonitrile Substituted Half Sandwich Complexes of Wolfram(IV)

Abstract

A good entry to cyclopentadienyl substituted isonitrile complexes of W(IV) is provided by CpW(CO)(t-BuNC)(I)3 (4), prepared by oxidative decarbonylation of cis- or trans-CpW(CO)2(t-BuNC)I (2,3) with elemental iodine. The isomers 2 and 3, separable by column chromatography on silica at low temperature, are easily obtained from CpW(CO)3I (1) and t-BuNC using Me3NO as a decarbonylating agent. Compound 4 reacts with t-BuNC to yield a mixture of the cationic complexes [CpW(CO)(t-BuNC)2(I)2]I (5) and [CpW(t-BuNC)3(I)2]I (6). The neutral cyano complex CpW(CN)(t-BuNC)2(I)2 (7), resulting from the dealkylation of one tert-butylisonitrile ligand, is also obtained. The insoluble main product 5 is easily separated from 6 and 7, and is converted with AgBF4 to the corresponding BF4-salt [CpW(CO)(t-BuNC)2(I)2]BF4 (8). The soluble byproducts 6 and 7 have been purified by column chromatography on silica. The composition and structure of the new complexes 4-8 have been derived from elemental analyses and spectroscopic investigations. The ionic nature of 6 and 8 has been confirmed by comparison of their conductivity data in 1,2 dichloroethane with that of NR4 +X- salts (R = alkyl; X = Br, I)