93403-54-4Relevant articles and documents
Substitution by phosphorus ligands on edge-double-bridged triruthenium carbonyl complexes and on Ru2{M-O=C(Et)}2(CO)6: 13C NMR characterization
Kampe, Carsten E.,Kaesz, Herbert D.
, p. 4646 - 4653 (2008/10/08)
Edge-double-bridged triruthenium carbonyl complexes and a double-bridged dinuclear complex undergo facile substitution of a carbonyl group by a phosphorus ligand at 25°C in hexane solution. When a bridging acyl group is present, substitution occurs exclusively on the ruthenium atom to which the acyl oxygen atom is bonded. The starting materials undergo rapid exchange with 13CO, permitting their enrichment for 13C NMR studies. The four systems studied are presented in their order of increasing reactivity. (1) The complex Ru3{μ-H,μ-O=C(Me)}(CO)10 reacts within 4 h with 1 molar equiv of triphenylphosphine to give the substitution product Ru3{μ-H,μ-O=C(Me)}(CO)9PPh3 in 48% yield. Starting material (25%) and some 10% of the complex Ru3(CO)11PPh3 are also obtained. With excess triphenylphosphine less of the monosubstituted acyl hydrido complex is obtained. Reaction with P(OMe)3 requires an excess of phosphite, but then only a 15% yield of Ru3{μ-H,μ-O=C(Me)}(CO)9P(OMe)3 is isolated along with Ru3(CO)11P(OMe)3 (5%). (2) The complexes Ru3{μ-H,μ-X}(CO)10 react within 10 min with 1 equiv of triphenylphosphine to yield the products Ru3{A?-H,μ-X)(CO)9PPh3, X = Cl, Br, I, respectively. When X = I, a carbonyl group is readily lost from the product to give Ru3{M-H,μ3-I}(CO)8PPh3. This transformation is reversible. Variable-temperature 13C NMR study of Ru3{μ-H,μ-Cl}(CO)9PPh3 and Ru3{μ-H,μ-Br}(CO)9PPh3 indicates an intramolecular polytopal rearrangement for the three carbonyl groups of the Ru(CO)3 unit on the bridged edge: coalescence temperature -45°C. (3) The complexes Ru3{μ-X,μ-O=C(Et)}(CO)10, X = Cl, Br, I, react in less than 1 min with triphenylphosphine to give nearly quantitative yields of Ru3{μ-X,μ-O=C(Et)}(CO)9PPh3 (98, 95, and 93%, respectively) or trimethyl phosphite to give Ru3{μ-X,μ-O=C(Et)}(CO)9P(OMe)3 (78, 75, and 68%, respectively). Exposure of Ru3{μ-Cl,μ-O=C(Et)}(CO)10 in chloroform solution to an atmosphere of 13CO leads to initial enrichment at six sites; the enrichment equilibrates with the remaining four carbonyl groups over a period of 8 h. (4) The dinuclear complex Ru2{μ-O=C(Et)}2(CO)6 reacts in less than 1 min with phosphorus ligands to give quantitative yields of the monosubstituted derivative (CO)2(L)Ru{μ-O=C(Et)}2Ru(CO)3, L = PPh3, P(OMe)3, P(OPh)3. Exposure of Ru2{μ-O=C(Et)}2(CO)6 in chloroform solution to an atmosphere of 13CO leads to instantaneous specific enrichment at three sites on the ruthenium atom bonded to the acyl oxygen atoms, equilibrating to the remaining three sites in 8 h.
