Some remarkable reactions of the alkylidyne cluster [Os₃(μ-H)₂(CO)₉(μ₃-CNC ₅H₄C₅H₄N)] (NC₅H₄C₅H₄N = 4,4′-bipyridine) with electrophiles. Crystal and molecular structures of the novel water-soluble dicationic cluster complex [Os₃...

Full title: Some remarkable reactions of the alkylidyne cluster [Os3(μ-H)2(CO)9(μ3-CNC 5H4C5H4N)] (NC5H4C5H4N = 4,4′-bipyridine) with electrophiles. Crystal and molecular structures of the novel water-soluble dicationic cluster complex [Os3(μ-H)3(CO)9(μ3-CNC 5H 4C5H4NH)][BF4] 2·H2O. Protonation of the μ3-alkylidyne cluster [Os3(μ-H)2(CO)9(μ3-CNC 5H4C5H4N)] 1 (NC5H4C5H4N = 4,4′-bipyridine) took place in two consecutive steps upon treatment with strong protonic acids such as HBF4 or CF3CO2H in dichloromethane. Initial protonation occurs at the organic ligand to give quantitatively the monocationic dihydrido species [Os3(μ-H)2(CO)9(μ3-CNC 5H4C5H4NH)]+ 2. In the presence of an excess of acid a second protonation takes place at the metal core and 2 is rapidly converted into a water-soluble dicationic trihydrido cluster [Os3(μ-H)3(CO)9(μ3-CNC 5H4C5H4NH)]2+ 3. The crystal structure of the bis(tetrafluoroborate) salt as its monohydrate has been determined, and reveals the presence of extensive hydrogen bonding. The formation of complexes 1-3 is found to be reversible by successive protonation and deprotonation processes, and is reminiscent of typical acid-base equilibria. On the other hand, the reaction of 1 with [Me3O]+BF4- in dichloromethane afforded the N-methylated derivative, [Os3(μ-H)2(CO)9(μ3-CNC 5H4C5H4NMe)]+ 4, which gave another dicationic complex [Os3(μ-H)3(CO)9(μ3-CNC 5H4C5H4NMe)]2+ 5 on protonation with HBF4 or CF3CO2H. Similar to 3, complex 5 is very soluble in water.