Synthesis, structure and reactivity of novel W–Ge chlorocarbonyl compounds. X-ray crystal structure of [WCl(GeCl 3)(CO) 3(NCEt) 2

Abstract

The reaction of GeCl 4 with tungsten(0) compounds yielded heterobimetallic W–Ge complexes. The novel dinuclear complex [(CO) 4W( μ-Cl) 3W(GeCl 3)(CO) 3] 1 was obtained together with [W(CO) 5(GeCl 2)] 2 in a photochemical reaction of W(CO) 6 with GeCl 4. The mononuclear seven-coordinate complex [WCl(GeCl 3)(CO) 3(NCMe) 2] 3 was formed in a reaction of complex 1 with acetonitrile or in a reaction of [W(CO) 4(NCMe) 2] with GeCl 4 in dichloromethane. A single-crystal X-ray diffraction study of the complex [WCl(GeCl 3)(CO) 3(NCEt) 2] 4 showed that the environment of the tungsten atom is a distorted capped octahedron with the GeCl 3 anionic ligand occupying the unique capping position above an octahedral face defined by the three carbonyl groups. The position of the GeCl 3 ligand is approximately trans to the W–Cl bond. The dinuclear complex 1 and the mononuclear complex 3 show similar behavior in reaction with alkynes. Complexes were isolated in which CO or/and acetonitrile ligands were replaced by alkyne ligands. The alkyne tungsten(II) complexes 7–13 formed were structurally characterized by IR and NMR spectroscopy. However, the reaction of 1 and 3 with phenylacetylene (PA) leads to polymerization and formation of a high molecular weight polyphenylacetylene (PPA). The structures and mechanisms of the formation of various new types of complexes and their role in the catalytic process are discussed.