Reactivity of unsaturated [HOs3(CO)8{µ3-Ph2PCH2PPh(C6H4)}] towards activated alkynes RC[tbnd]CR (R=CO2Et, CO2Me)

Abstract

The reactivity of unsaturated [HOs3(CO)8{µ3-Ph2PCH2PPh(C6H4)}] (1) with activated alkynes (RC[tbnd]CR) such as diethyl acetylenedicarboxylate (DEAD, R = CO2Et) and dimethyl acetylenedicarboxylate (DMAD, R = CO2Me) is investigated. Reaction of 1 with DEAD or DMAD at 80 °C affords four different types of products namely [Os3(CO)7(µ-CO)(µ3,η2-RCCR)(µ-dppm)] (2), [Os3(CO)7{µ,η2-RCC(H)R}{µ3,η2,κ1,κ1-Ph2PCH2P(Ph)C6H4}] (3), [Os3(CO)7{µ3,η4-(RCCR)2}(µ-dppm)] (4) and [Os3(CO)8{µ,η2,κ1-RCC(H)R}{µ3,η1,κ1,κ1-Ph2PCH2P(Ph)C6H4}] (5). Cluster 2 is formed by simple coordination of alkyne to the cluster core, whereas 3 and 5 are formed via 1,2-insertion of the alkyne into the Os−H bond of 1. Dimerization of alkynes on cluster surface leads to the formation of 4. Thermolysis of 2 under similar experimental conditions affords another new product [Os3(CO)7(µ-CO){µ3,η2,κ1,κ1-RCCC6H4(Ph)PCH2PPh2}] (6) via C[sbnd]C coupling between the coordinated alkyne and one of the phenyl rings of dppm. The molecular structures of the different types of products isolated from these reactions have been confirmed by single crystal X-ray diffraction analyses. © 2020