SOLUTION STRUCTURES AND DYNAMICS OF RU-4(MU-H)(4)(CO)(12-X)L(X) (X=1-4, L=P(OET)(3), PPH(3) X=1, 2, L=ASPH(3)) DERIVATIVES BY VT MULTINUCLEAR NMR-SPECTROSCOPY - X-RAY STRUCTURE DETERMINATION OF RU-4(MU-H)(4)(CO)(10)(P(OET)(3))(2)

The addition of the catalyst (FeCp(CO)(2))(2) to the solution reaction s of Ru-4(mu-H)(4)(CO)(12) with L (L = P(OEt)(3), PPh(3), AsPh(3)) aff ords the substitution derivatives RU(4)(mu-H)(4)(CO)(12-x)L(x) (x = 1- 4, L = P(OEt)(3), PPh(3); x = 1, 2, L = AsPh(3)) with good selectivity modulated by the carbonyl to ligand ratio and in satisfactory yield. Multinuclear variable temperature NMR studies at different temperature s show that the tri- and tetrasubstituted products are each obtained i n only one isomeric form while for L = P(OEt)(3) the monosubstituted d erivative exists as two isomers in solution. The disubstituted derivat ives form only one isomer for L = P(OEt)(3), whereas two isomers are o bserved for L = PPh(3), AsPh(3). The stereochemical nonrigidity of the title compounds has been investigated, and correlations between solid -state and solution structures are discussed.