New Tetraruthenium Cluster from the Thermolysis of [Ru 3 (CO) 10 (μ-dppm)]: Crystal Structure of [HRu 4 (CO) 9 (μ 3 -PhPCH 2 PPh 2 ) (μ 3 ,η 2 :η 1 :η 1 -C 6 H 4 )]

Thermolysis of [Ru 3 (CO) 10 (μ-dppm)] ( 1 ) in refluxing benzene, followed by chromatographic separation by TLC, afforded the new cluster [HRu 4 (CO) 9 (μ 3 -PhPCH 2 PPh 2 )(μ 3 ,η 2 :η 1 :η 1 -C 6 H 4 )] ( 10 ) in 7% yield in addition to the previously reported clusters [Ru 3 (CO) 9 {µ 3 -PhPCH 2 PPh(C 6 H 4 )}] ( 2 ) and [HRu 4 (CO) 9 (μ 4 -PhPCH 2 PPh 2 )(μ 4 ,η 6 :η 1 :η 1 -C 6 H 4 )] ( 8 ) in 70% and 4% yields, respectively. The molecular structure of 10 has been determined by single-crystal X-ray diffraction analysis. Compound 10 possesses a Ru 4 metal core where two of the six triangular faces are capped by μ 3 ,η 2 :η 1 :η 1 -C 6 H 4 (benzyne) and µ 3 -PhPCH 2 PPh 2 ligands. Compound 10 transforms to the known cluster [HRu 4 (CO) 9 (μ 3 -PhPCH 2 PPh 2 )(μ 4 ,η 6 :η 1 :η 1 -C 6 H 4 )] ( 8 ) slowly at 80 °C. The bonding in the new cluster 10 has been investigated by electronic structure calculations. Graphical Abstract A new tetraruthenium cluster has been isolated and structurally characterized from the thermolysis of [Ru 3 (CO) 10 (μ-dppm)] at 80 °C.