Syntheses and Reactivity Studies of the Carbido-Alkylidyne Cluster Complexes LWRu₄(μ₅-C)(μ-CPh)(CO)₁₂and LWRu₅(μ₆-C)(μ-CPh)(CO)₁₄, L = Cp and Cp*, Obtained from Reversible Scission of Acetylide Ligand

Abstract

Treatment of a 1:1 mixture of Ru 3 (CO) 12 and the acetylide cluster LWRu 2 (CO) 8 (C 2 Ph) (1, L ) Cp and Cp*) in hydrocarbon solvents afforded two carbido-alkylidyne cluster complexes, LWRu 4 (µ 5 -C)(CO) 12 (µ-CPh) (2) and LWRu 5 (µ 6 -C)(CO) 14 (µ-CPh) (3). Complexes 2 contain a square pyramidal cluster skeleton with a µ 5 -carbide and an accompanying bridging alkylidyne ligand, while WRu 5 complexes 3 possess a distorted octahedral WRu 5 (µ 6 -C) framework. The transformation from 1 to 2 and 3 illustrates a reversible cleavage of an acetylide carboncarbon bond induced by the cluster-building reaction. Moreover, the hydrogenation of complexes 2 and 3 was found to depend on the ancillary ligand on the W atom, showing selective formation of only two hydride complexes, CpWRu 4 (µ 5 -C)(µ-CPh)(µ-H) 2 (CO) 11 ( 4) and Cp*WRu 5 (µ 6 -C)(µ-CPh)(µ-H) 2 (CO) 13 ( 5), respectively. Single-crystal X-ray analysis on complex 4 indicated that the hydrides resided near the apical Ru atom, while the hydrides in complex 5 were associated with the unique W metal atom. Finally, treatment of 2 with thiophenol has led to formation of the wingtip-bridged butterfly complexes LWRu 4 (µ 5 -C)(µ-CPh)(µ-H)-(µ-SPh)(CO) 11 (7a, L ) Cp; 7b, L ) Cp*), in which the thiolate ligand is bonded to the Ru atoms separated by a nonbonding distance of 3.4186(8) Å.

Transition Metal Carbide Complexes

“…While Johnson’s μ 5 -carbide clusters form upon C atom abstraction from alkenes, Chi and Peng established how heterometallic acetylide-carbonyl clusters enact C atom abstraction from their acetylide ligands (Figure ). − For instance, the tungsten–ruthenium cluster, [CpWRu 2 (CCPh)­(CO) 8 ], reacts with [Ru 3 (CO) 12 ] in refluxing heptane to generate a mixture of the carbide–carbyne clusters, [CpWRu 4 (μ 5 -C)­(CPh)­(CO) 12 ] and [CpWRu 5 (μ 6 -C)­(CPh)­(CO) 14 ] . The μ 5 -carbide cluster converts to the μ 6 -carbide cluster upon continued heating with [Ru 3 (CO) 12 ].…”