ETA(2)-THIOPHENE COMPLEXES OF PENTAAMMINEOSMIUM(II) AND THEIR REVERSIBLE PROTONATION TO FORM NOVEL ETA(2)-2H-THIOPHENIUM SPECIES

A series of complexes of the type [Os(NH3)(5)(4,5-eta(2)-L)](OTf)(2) ( where L = thiophene (1a), 2-methylthiophene (1b), 3-methylthiophene (1 c), 2,5-dimethylthiophene (1d), 2-methoxythiophene (1e), 3-methoxythio phene (1f), and benzo[b]thiophene (1g)) were prepared and characterize d by NMR and cyclic voltammetry (CV). Treatment of 1a-d with 1 equiv o f HOTf yields novel isolable 2H-thiophenium complexes with the osmium bound to C(5) and sulfur.