The synthesis of di- and tetra-nuclear p-cymene–osmium hydride complexes; characterisation by1H(187Os) reverse INEPT two-dimensional nuclear magnetic resonance spectroscopy

Abstract

[(p-MeC6H4CHMe2)2Os2(µ-H)(µ-Cl)Cl2] was formed from reaction of propan-2-ol with either [(p-MeC6H4CHMe2)2Os2Cl4](in the presence of KPF6 or HPF6 as catalyst) or [(p-MeC6H4CHMe2)2Os2(µ-Cl)3][PF6]. The dinuclear trihydride [(p-MeC6H4CHMe2)2Os2(µ-H)3]+(5) and the tetranuclear tetrahydride [(p-MeC6H4CHMe2)4Os4(µ-H)4]2+ were obtained from reaction of [(p-MeC6H4CHMe2)2Os2(µ-OH)3]+(4) with propan-2-ol, and the trihydride (5) was also prepared by reaction of (4) with formaldehyde. The chloro-acetate [(p-MeC6H4CHMe2)Os(O2CMe)Cl] gave a mixture of [(p-MeC6H4CHMe2)2Os2(µ-H)(µ-Cl)-(µ-O2CMe)]+ and [(p-MeC6H4CHMe2)Os2(µ-H)2(µ-O2CMe)]+(13); while the diacetate [(p-MeC6H4CHMe2)Os(O2CMe)2](8a) gave a mixture of (13), [(p-MeC6H4CHMe2)2Os2(µ-H)-(µ-O2CMe)2]+(14), and (5) on reaction with propan-2-ol at 80 °C. The bis(trifluoroacetate)[(p-MeC6H4CHMe2)Os (O2CCF3)2] reacted analogously with propan-2-ol to give a mixture of two neutral complexes, [(p-MeC6H4CHMe2)2Os2(µ-H)(µ-O2CCF3)(O2CCF3)2] and [(p-MeC6H4CHMe2)2Os2(µ-H)2(O2CCF3)2]. In each reaction the proportions of each product depended on the time of reaction, longer times favouring more highly hydrided complexes. The new hydride complexes were characterised with the help of n.m.r. spectroscopy including 1H(187Os) reverse INEPT two-dimensional n.m.r. spectra. The diacetate (8a) underwent hydrolysis to give [(p-MeC6H4CHMe2)2Os2(µ-OH)2(µ-O2CMe)]+ and methanolysis to give [(p-MeC6H4CHMe2)2Os2-(µ-OMe)3]+, and on work-up (14) was hydrolysed to [(p-MeC6H4CHMe2)2Os2(µ-H)(µ-OH)-(µ-O2CMe)2].