INCORPORATION OF THIOPHENE RINGS INTO TRIRUTHENIUM AND TETRARUTHENIUMCLUSTERS VIA CYCLOMETALATION AND C-P BOND-CLEAVAGE OF THE LIGAND DIPHENYL-2-THIENYLPHOSPHINE

Diphenyl-2-thienylphosphine, Ph(2)PC(4)H(3)S (1), reacts with [Ru-3(CO )(12)] in refluxing toluene to give the compound [Ru-3(mu(2)-H)(mu(3)- Ph(2)PC(4)H(2)S)(CO)(9)] (2) (59%), cyclometalated at the thiophene ri ng, with smaller amounts of the cluster H)(mu(3)-Ph(2)PC(4)H(2)S)(CO)( 8)(Ph(2)PC(4)H(3)S)] (3) (10%), which is a substituted derivative of 2 and may also be formed by substitution at 2 with ligand 1. The single -crystal X-ray structure of cluster 2 shows that it contains the mu(3) -ligand Ph(2)PC(4)H(2)S bound through phosphorus to one Ru atom, throu gh a sigma-Ru-C bond to another and by an eta(2) interaction to the th ird. There is a dynamic interchange between the sigma and eta(2) inter actions of the thienyl group leading to NMR coalescence and a time-ave raged plane of symmetry. The corresponding process would be nondegener ate in the substituted compound 3 (X-ray structure reported) and is qu enched. Thermal treatment of cluster 2 with [Ru-3(CO)(12)] gave two te tranuclear clusters, [Ru-4(mu(4)-PPh)(mu(4)-C4H2S)(CO)(11)] (5) by eli mination of benzene and the known cluster [Ru-4(mu(4)-PPh)(mu(4)-C6H4) (CO)(11)] (6) by elimination of thiophene. Although compounds 5 and 6 are stoichiometrically equivalent, their single-crystal X-ray structur es show that they adopt different geometries. The structure of 6 was s hown to be the same as that reported previously for the compound deriv ed from PPh(3). Each has an approximate square of metal atoms capped o n one side by mu(4)-PPh and on the other by mu(4)-thiophyne (C4H2S) or mu(4)-benzyne (C6H4), respectively. The C6H4 ligand is coordinated as a 6-electron donor, tilted with respect to the Ru-4 plane, with the c oordinated C-C bond parallel to an Ru-Ru edge, whereas C4H2S is coordi nated as a 4-electron donor, perpendicularly and diagonally across the Ru-4 plane in a manner related to known alkyne clusters of the type [ Ru-4(mu(4)-PPh)(mu(4)-alkyne)(CO)(11)].