Synthesis, Characterization, and Reactivity of Cationic Molecular Hydrogen Complexes of Manganese(I)

Abstract

Hydride complexes MnH(CO)3P2 (1), MnH(CO)2P3 (2), and MnH(CO)P4 (3) (P = P(OEt)3 (a), PPh(OEt)2 (b), PPh2OEt (c), PPh(OiPr)2 (d) were prepared by allowing the MnH(CO)5 species to react with an excess of phosphine upon UV irradiation or under reflux conditions. Their formulation and geometry in solution were established by IR and 1H, 13C, and 31P NMR spectroscopy. Protonation reactions with HBF4·Et2O of the monocarbonyls MnH(CO)P4 (3) afford isolable dihydrogen derivatives [Mn(η2-H2)(CO)P4]BPh4 (5), which were characterized by variable-temperature 1H and 31P NMR spectra, T1 measurements, and JHD values. Thermally unstable (above 0 °C) [Mn(η2-H2)(CO)2P3]+ (4) cations were also prepared by protonation of the dicarbonyl hydrides MnH(CO)2P3 (2) and fully characterized in solution. Evolution of H2 from 4 and 5 results in the formation of the unsaturated complexes [Mn(CO)2P3]BPh4 (6) and [Mn(CO)P4]BPh4 (7), which are probably stabilized by an agostic interaction between the metal center and a C−H proton of the p...