Technetium and rhenium pentacarbonyl perchlorates: Structure and reactivity

Carbonyl perchlorates [M(ClO4)(CO)5] (M = Tc, Re) were prepared by treatment of [TcI(CO)5] and [ReCl(CO)5], respectively, with AgClO4 in dichloromethane. The complexes were isolated in the form of yellowish and colorless crystals, respectively, and characterized by IR spectroscopy and single crystal X-ray diffraction (XRD). Perchlorate ion is coordinated to the central atom in the monodentate fashion. Perchlorate ligand in the coordination sphere of [M(ClO4)(CO)5] (M = Tc, Re) can be readily substituted by a molecule of a coordinating solvent (acetonitrile). [Re(CO)5(CH3CN)]ClO4 is stable with respect to thermal decarbonylation and was isolated and characterized by single crystal XRD. The coordination polyhedron of rhenium in [Re(CO)5(CH3CN)]ClO4 is less distorted than that in [M(ClO4)(CO)5]. [Tc(CO)5(CH3CN)]ClO4, contrary to its rhenium analog, is unstable in acetonitrile solution and undergoes rapid decarbonylation to form [Tc(CO)3(CH3CN)3]ClO4.