Nature of the novel C15H15 ligand in [W(CO)2(η5-C5H5)(η3-C15H15)]

Abstract

A structural study of the compound originally formulated as [W(CO)₂(C₅H₅)₄] has revealed that it is actually [W(CO)₂(η⁵-C₅H₅)(η³-C₁₅H₁₅)]. The substance crystallizes in the monoclinic space group P2₁/c with a= 13.578(8), b= 20.967(9), c= 13.831(8), Å, β= 109.72(6)°, and Z= 8 for D_c= 1.79 g cm^–3. The final R value was 0.079 for 2 458 independent observed reflections. In the two crystallographically independent molecules the W–C(η³) bonds show significant internal variation: the unique W–C lengths average 2.19 Å and the remaining ones, 2.36 Å. The W–C(η⁵) bond lengths average 2.34 Å. The five-membered ring bonded in an allylic fashion to the tungsten atom contains two tetrahedral carbon atoms, each of which is bonded to one C₅H₅ group and one hydrogen atom. The two C₅H₅ sub-units may be viewed as dienes and differ in the location of the tetrahedral carbon atoms. It exists in the 2 position on one and the 3 position on the other. The C₅H₅ groups are in a cis-arrangement, exo to the tungsten atom.