Synthesis, Structure, and Reactivity of an Osmacyclopentene Complex

Treatment of OsCl2(PPh3)2(CH═C(PPh3)CH(OH)-η2-C≡CH) (1) with PPh3 and Bu4NCl in CH2Cl2 under air gave paramagnetic osmacyclopentene [OsCl2(PPh3)2(CH═C(PPh3)CH(OH)C(═CH(PPh3)))]Cl (5). Heating the suspension of 5 in CH2Cl2 under a nitrogen atmosphere led to the formation of η2-allene-coordinated osmacycle OsCl2(PPh3)(CH═C(PPh3)CH═C═CH(P(C6H4)Ph2)) (6) and chloro-osmabenzene OsCl2(PPh3)2(CHC(PPh3)CHCClCH) (7) via disproportionation reaction. Oxidative transformation of 5 under an oxygen atmosphere yielded osmafuran [OsCl(PPh3)2(CHC(PPh3)CHO)(C≡C(PPh3))]Cl (10). In addtion, complexes 6, 7, and 10 can also undergo ligand substitution reactions with NaSCN to afford more stable analogues.