η2-Thiophene Complexes of Pentaammineosmium(II) and their Reversible Protonation to Form η2-2H-Thiophinium Species

Summary: A series of complexes of the type [OsfNH&s- (4,5-rf2-L)](OTf)2 (where L= thiophene (la), 2-methyl-thiophene (lb), 3-methylthiophene (lc), 2,5-dimethyl-thiophene (Id), 2-methoxythiophene (le), 3-methoxythio-phene (If), and benzofbjthiophene (lg))were prepared and characterized by NMR and cyclic voltammetry (CV). Treatment of la-d with 1 equiv of HOTf yields novel isolable 2H-thiophenium complexes with the osmium bound to C(5) and sulfur.