Microwave-induced dppm ligand substitution in triosmium clusters: Structural and DFT evaluation of Os3 clusters containing multiply activated dppm ligands through cyclometalation, ortho metalation, and PC bond cleavage

• Four new triosmium carbonyl clusters with multiple dppm ligands were synthesized and characterized.
• All of the new clusters contain at least one dppm ligand that has undergone CH and/or CP bond cleavage.
• One new cluster has the longest OsOs bond ever reported.
• First example of an Os3 compound with three dppm ligands.
• Microwave heating improved the synthesis of Os3(CO)8(dppm)2.

Four new triosmium carbonyl complexes containing multiple dppm ligands were produced by microwave heating of solutions containing Os3(CO)12 and excess dppm. Three of these complexes, Os3(μ-H)2(CO)6(μ-dppm)[μ3-Ph2PCHP(C6H4)Ph] (2), Os3(CO)6[μ3-Ph2PCH2P(C6H4)Ph]2 (3), and Os3(μ-H)(CO)6[μ3-PhPCH2P(C6H4)Ph][μ3-PhPCH(C6H4)PPh] (4), contain two dppm ligands per Os3 unit, while the fourth, Os3(μ-H)(CO)5(dppm)[μ3-PhPCH2P(C6H4)Ph][μ3-PhPCH(C6H4)PPh] (5), is the first example of an Os3 cluster containing three dppm ligands. Microwave heating was also used to prepare the known complex Os3(μ-dppm)2(CO)8 (1) more efficiently than previously reported. The new complexes 2–5 have been characterized by IR, NMR, mass spectrometry, and X-ray crystallography. In addition, the bonding in these complexes has been examined by electronic structure calculations. All of the new complexes contain at least one dppm ligand that has undergone CH and/or CP bond activation. Complex 2 is a 48e cluster that contains one intact dppm ligand and one face-capping dppm ligand that coordinates all three osmium sites through the phosphine moieties and cyclometalated and ortho-metalated carbon atoms. Complex 3 is a 48e cluster with two ortho-metalated dppm ligands while complexes 4 and 5 are 50e clusters that possess a common metallic framework with one cyclometalated dppm ligand and one ortho-metalated dppm ligand.

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