SYNTHESIS OF NEW ALKYNE-BRIDGED DITUNGSTEN COMPLEXES [W2(CO)4(MU-HC(2)R)(ETA-C5H5)2] (R=ME OR PH) AND THE REACTIONS OF THESE AND RELATED ALKYNE-BRIDGED COMPLEXES WITH CHLORODIPHENLPHOSPHINE

The new ditungsten alkyne-bridged complexes [W-2(CO)(4)(mu-R(1)C(2)R(2 ))(eta-C5H5)(2)] (R(1) = H, R(2) = Ph 1C or Me 1d) have been prepared. These and the related complexes with R(1) = R(2) = Ph 1a or CO(2)Me 1 b were treated with PPh(2)Cl in refluxing xylene or toluene. The ident ity of the products depends on the nature of the R group but in genera l their formation involves the oxidative addition of one or more molec ules of PPh(2)Cl to 1. From 1a two species, [W2Cl(mu-PPh(2))(mu-PhC(2) Ph)(CO)(eta-C5H5)(2)] 2a and [W-2(O)Cl(mu-PPh(2))(mu-PhC(2)Ph)(eta-C5H 5)(2)] 4a, in which the alkyne bridge remains intact were isolated, al ong with a paramagnetic complex, [W2Cl(mu-PPh(2))(2)(CO)(eta-C5H5)(2)] 3a. from which the alkyne bridge has been displaced by a diphenylphos phide group. Reaction of 1b with PPh(2)Cl gave [W2Cl(mu- PPh(2)){mu-C- 2(CO(2)Me)(2)}(CO)(eta-C5H5)(2)] 2b, an analogue of 2a, together with two complexes involving phosphorus-carbon bond formation, -PPh(2)C(CO( 2)Me)=C(CO(2)Me)}(CO)(2)(eta-C5H5)(2)] 6b and 2(mu-PPh(2)){mu-PPh(2)C= CH(CO(2)Me)}(eta-C5H5)(2)] 5b. The formation of 5b, involves, in addit ion, cleavage of a carbon-carbon bond. From 1c, both of the products, [W2Cl2{mu-PPh(2)C-CPPh}(eta-C5H5)(2)] 5c and [W2Cl2(mu-Cl)(mu-PPh(2)C= CHPh)(eta-C5H5)(2)] 7c, involve phosphorus-carbon bond formation. Fina lly from 1d the only well characterised product is a terminal oxo spec ies, [W2O(mu-PPh(2))(mu-CH=CHMe)(CO)(eta-C5H5)(2)] 8d, in which a viny l group and a phosphide fragment bridge the two metal centres. A compl ex related to 8d, h(2)){mu-C(CO(2)Me)=CH(CO(2)Me)}(CO)(eta-C5H5)(2)] 8 b, is formed on treatment of 2b with silica. Thermolysis of complex 6b results in phosphorus-carbon bond cleavage to give 2b. In contrast, p hotolysis of 6b gives, as the only well characterised product, paramag netic {mu-PPh(2)C(CO(2)Me)=C(CO(2)Me)}(CO)(eta-C5H5)(2)] 9b. The struc tures of complexes 2a, 3a and 9b have been determined by X-ray crystal lography.