Synthesis, Characterization, and Dynamic Behaviour of Triosmium Clusters Containing the Tridentate Ligand {Ph2PCH2CH2}2S (PSP)

Reaction of [Os3(CO)11(NCMe)] with bis-diphenylphosphanylethylene sulfide, {Ph2PCH2CH2}2S (PSP), leads to the formation of [Os3(CO)11(PSP)] and [{Os3(CO)11}2(μ-PSP)] in good yield. Similarly, treatment of [Os3(CO)10(NCMe)2] with PSP affords the cluster [Os3(CO)10(μ-PSP)], in which the two phosphanes of the PSP ligand coordinate to different osmium atoms of the same triosmium unit. Reaction of [Os3(CO)11- (PSP)] with [Os3(CO)10(NCMe)2] yields the compound 1,2- [{Os3(CO)11}(μ3-PSP){Os3(CO)10}] in which the thioether moiety and one of the phosphane groups of the PSP ligand are coordinated equatorially to the {Os3(CO)10} subunit. The cluster 1,2-[{Os3(CO)11}(μ3-PSP){Os3(CO)10}] is also formed when [Os3(CO)11(PSP)] is oxidatively decarbonylated by reaction with trimethylamine N-oxide. The metastable cluster 1,2-[{Os3(CO)11}(μ3-PSP){Os3(CO)10}] undergoes slow isomerisation at room temperature to form 1,1-[{Os3(CO)11}(μ3- PSP){Os3(CO)10}] in which the thioether and phosphane moieties coordinate in a chelating mode to one of the {Os3- (CO)10} subunits with the thioether moiety in an axial position. The dynamic behaviour of these clusters has been investigated by variable-temperature 13C{1H} and 13P{1H} NMR spectroscopy. The solid-state structures of [{Os3- (CO)11}2(μ-PSP)] and [Os3(CO)10(μ-PSP)] are reported.