Some remarkable reactions of the alkylidyne cluster (Os3(n-H)2(CO)9(n3-CNC10H8N)) with electrophiles. Crystal and molecular structures of a novel water-soluble dicationic cluster complex (Os3(n-H)3(CO)9(n3-CNC10

Abstract

Protonation of the µ3-alkylidyne cluster [Os3(µ-H)2(CO)9(µ3-CNC5H4C5H4N)]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-CNC5H4C5H4NH)]+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-CNC5H4C5H4NH)]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-CNC5H4C5H4NMe)]+4, which gave another dicationic complex [Os3(µ-H)3(CO)9(µ3-CNC5H4C5H4NMe)]2+5 on protonation with HBF4 or CF3CO2H. Similar to 3, complex 5 is very soluble in water.