Reactivity of a triruthenium alkenyl cluster complex with conjugated diynes: Coupling of two diyne molecules via a face-capping diyne intermediate

The cluster [Ru3(μ3-κ2-HNNMe2)(μ-κ2-PhCHCPh)(μ-CO)2(CO)6], which has a face-capping 1,1-dimethylhydrazido and an edge-bridging 1,2-diphenylethenyl ligand, reacts with diphenylbutadiyne or 2,4-hexadiyne to give the isomeric triruthenium carbonyl cluster complexes [Ru3(μ3-κ2-HNNMe2)(μ-κ2-PhCHCPh){μ3-κ4-RCCCC(R)C(R)CCCR}(CO)6] (3a, R = Ph; 3b, R = Me) and [Ru3(μ3-κ2-HNNMe2)(μ-κ2-PhCHCPh){μ3-κ4-RCCCC(R)C(CCR)CR}(CO)6] (4a, R = Ph; 4b, R = Me). These compounds contain a large unsaturated hydrocarbyl ligand that arises from a metal-cluster-mediated head-to-head (3) or head-to-tail (4) coupling of two diyne molecules and maintain the original hydrazido and ethenyl ligands. Metal clusters that contain a face-capping diyne coordinated through only one alkyne fragment, such as [Ru3(μ3-κ2-HNNMe2)(μ-κ2-PhCHCPh)(μ3-κ2-RCCCCR)(CO)7], have also been isolated (2a, R = Ph; 2b, R = Me). They are the intermediates that incorporate a second diyne reagent to give 3 and 4. The structural parameters of intermediate 2b have been obtained from DFT calculations.