Synthesis, characterization, and reactivity of cationic molecular hydrogen complexes of manganese(I)

Hydride complexes MnH(CO)(3)P-2 (1), MnH(CO)(2)P-3 (2), and MnH(CO)P-4 (3) (P = P(OEt)(3) (a), PPh(OEt)(2) (b), PPh2OEt (c), PPh((OPr)-Pr-i)(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 H-1, C-13, and P-31 NMR spectroscopy. Protonation reactions with HBF4.Et2O of the monocarbonyls MnH(CO)P-4 (3) afford isolable dihydrogen derivatives [Mn(eta(2)-H-2)(CO)P-4]BPh4 (5), which were characterized by variable-temperature H-1 and P-31 NMR spectra, T-1 measurements, and J(HD) values. Thermally unstable (above 0 degrees C) [Mn(eta(2)-H-2)(CO)(2)P-3](+) (4) cations were also prepared by protonation of the dicarbonyl hydrides MnH(CO)(2)P-3 (2) and fully characterized in solution. Evolution of H-2 from 4 and 5 results in the formation of the unsaturated complexes [Mn(CO)(2)P-3]BPh4 (6) and [Mn(CO)P-4]BPh4 (7), which are probably stabilized by an agostic interaction between the metal center and a C-H proton of the phosphite. Treatment of the unsaturated complexes 6 and 7 and of the triflate compounds [Mn(eta(1)-OSO2CF3)(CO)(3)P-2] (8) with Li+RC=C- gave the new acetylide derivatives [Mn(C=CR)(CO)P-4] (9), [Mn(C=CR)(CO)(2)P-3] (10), and [Mn(C=CR)(CO)(3)P-2] (11) (R = Ph, p-tolyl). The new series of cationic manganese compounds [Mn(CO)(2)(p-tolylCN)P-3]BPh4 (12), [Mn(CO)(p-tolylCN)P-4]BPh4 (13), [Mn(Co)(2)(p-tolylNC)P-3]BPh4 (14), [Mn(CO)(p-tolylNC)P-4]BPh4 (15), [Mn(CO)(3)P-3]BPh4 (16), and [Mn(CO)(2)P-4]BPh4 (17) were also obtained by reacting the unsaturated compounds 6 and 7 with the appropriate ligands.