High-nuclearity ruthenium carbonyl cluster chemistry. 9. Ligand substitution at decaruthenium carbonyl clusters

The mono- to tri-substituted decaruthenium cluster anions [Ru10(μ-H)(μ6-C)(CO)24-x(L)x]- [L = P(C6H4Me-4)3, AsPh3, SbPh3, x = 1-3] were prepared as their [PPh4]+ salts in moderate to good yields from reaction of [PPh4][Ru10(μ-H)(μ6-C)(CO)24] with the corresponding group 15 ligands at room temperature in acetone. The tetrakis-substituted cluster Ru10(μ6-C)(μ3-CO)(μ-CO)(CO)19(P(C6H4Me-4)3)4 was obtained in high yield from [PPh4]2[Ru10(μ6-C)(CO)24] and an excess of the phosphine under the same conditions; a single-crystal X-ray diffraction study revealed that the phosphines ligate at the vertices of the "giant tetrahedral" core. Kinetics studies of the formation of [PPh4][Ru10(μ-H)(μ6-C)(AsPh3)2(CO)22] from [PPh4][Ru10(μ-H)(μ6-C)(AsPh3)(CO)23] shows that ligand substitution at these giant tetrahedral clusters proceeds via a strongly associative pathway with the likely intermediacy of a Ru-Ru bond-cleaved intermediat