Synthesis, structure and reactivity of novel W-Ge chlorocarbonyl compounds.: X-ray crystal structure of [WCl(GeCl3) (CO)3(NCEt)2]

The reaction of GeCl4 with tungsten(0) compounds yielded heterobimetallic W-Ge complexes. The novel dinuclear complex [(CO)(4)W(mu-Cl)(3)W(GeCl3)(CO)(3)] 1 was obtained together with [W(CO)(5)(GeCl2)] 2 in a photochemical reaction of W(CO)(6) with GeCl4. The mononuclear seven-coordinate complex [WCl(GeCl3)(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 GeCl4 in dichloromethane. A single-crystal X-ray diffraction study of the complex [WCl(GeCl3)(CO)(3)(NCEt)(2)]4 showed that the environment of the tungsten atom is a distorted capped octahedron with the GeCl3 anionic ligand occupying the unique capping position above an octahedral face defined by the three carbonyl groups. The position of the GeCl3 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. (C) 1998 Elsevier Science S.A. All rights reserved.