Novel approach to intermediates containing a tungsten-arsenic triple bond

Thermolysis of the arsenidene complex [Cp*As{W(CO)(5)}(2)] (1) gave [Cp*(CO )(2)W(eta(3)-As-3)] (2), [{W(CO)(3)Cp*W}(2)(mu(3)-As)4] (3), and [{W(CO)(3) Cp*W}(2)(mu(3)-As)(3){mu(3)-AsW(CO)(5)}] (4) The products show that I has u ndergone a Cp* migration from the sigma-bound state at the As atom to eta(5 ) coordination at the transition metal, presumably via an intermediate of t he type [Cp*(CO)(2)W=As-->W(CO)(5)]. In a second transformation pathway rem oval of the Cp* group of the arsenidene complex 1 occurs to form an unsatur ated species of the type [As{W(CO)(5)}(2)]. Compound 2 exhibits the unusual formation of a cyclo-As-3 ligand, while the tetrahedral tungsten clusters 3 and 4 represent possible tetramers of the intermediates formed in both pa thways. Furthermore, photolysis of arsenidene complex 1 results in [As-2{W( CO)(5)}(3)] (5), which shows that the second pathway prevails under these c onditions.