Formation of Four Conjugated Osmacyclic Species in a One-Pot Reaction

Treatment of HCCCH(OH)CHCH2 with OsCl2(PPh3)3 in THF produced the η2-allyl alcohol osmacycle OsCl2(PPh3)2(CHC(PPh3)CH(OH)CHCH2) (2) with poor solubility and low stability, which underwent a ligand substitution reaction with PMe3 to give the more stable analogue [OsCl(PMe3)3(CHC(PPh3)CH(OH)CHCH2)]Cl (3). Heating the suspension of 2 in CH2Cl2 led to the formation of four interesting conjugated osmacycles in one pot, including the osmabenzene OsCl2(PPh3)2(CHC(PPh3)CHCHCH) (4), the cyclic osmium η2-allene complex OsCl2(PPh3)2(CHC(PPh3)CHCCH2) (5), the osmafuran OsCl2(PPh3)2(CHC(PPh3)C(CH2CH3)O) (6), and the α,β-unsaturated ketone complex OsCl2(PPh3)2(CHC(PPh3)C(O)CCH2) (7). All of the four products could also be produced in higher yield under appropriate conditions.