Intramolecular nucleophilic attack at the α-carbon atom of a µ3-alkynyl ligand in a triosmium cluster
Abstract
The cluster [Os3(CO)12] reacts with but-3-yn-1-ol, HCCCH2CH2OH, in hydrocarbon solvent at 130 °C to give the 2,3-dihydrofuran-4,5-diyl complex [Os3H2(CO)9(µ3-[graphic omitted])](3)(yield 48%). The probable route to this compound is indicated by the formation of the simple alkyne compound [Os3(CO)10(µ3-HCCCH2CH2OH)](1) from [Os3(CO)10(MeCN)2] and the alkynol at room temperature which at higher temperatures converts to compound (3) probably via its isomer [Os3H(CO)9(µ3-CCCH2CH2OH)](2). This isomerisation occurs because α-carbon atoms of µ3-alkynyl ligands are susceptible to nucleophilic attack which in this case occurs intramolecularly with cyclisation. The dynamic behaviour of clusters (1) and (3) is described; in both cases inversion of the chiral Os3(alkyne) group is observed.