Formation of hexaosmium raft clusters from [Os6(CO)16(MeCN)2]:synthesis, structural characterisation and reactivities of [Os6(CO)16-(m-h2-C5H4NS)2] and [Os6(CO)17(m-H)(m4-h2-C5H4NS)]

Abstract

Reaction of [Os6(CO)16(MeCN)2] with 1 equivalent of 2-Aldrithol in CH2Cl2 under ambient conditions afforded two new raft clusters [Os6(CO)16(µ3-η2-C5H4NS)2] 1 and [Os6(CO)17(µ-H)(µ4-η2-C5H4NS)] 2 in moderate and fair yields, respectively. Cyclic voltammograms of compound 1 exhibited two metal-based, one-electron reduction couples at E1/2 = –0.36 and –0.20 V together with an irreversible ligand-based anodic wave at ca. Epa = +0.31 V vs. Ag–AgNO3. Protonation of 1 with CF3CO2H produced an unstable species [Os6(CO)16(µ3-η2-C5H5NSH)(µ3-η2-C5H5NS)][CO2CF3] 3, which upon standing in CH2Cl2 quickly decomposed. All compounds have been fully characterised by spectroscopic methods, while the molecular structures of 1 and 2 were established by crystallographic techniques. Both 1 and 2 contain ‘ladder’-type and edge-fused raft cluster cores, with the sulfur atom in 2 being drawn intimately into the cluster envelope. These clusters serve as good models for substrates adsorbed onto metal surfaces.