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 an d H-1, C-13, and P-31 NMR spectroscopy. Protonation reactions with HBF 4.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, an d 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 di carbonyl hydrides MnH(CO)(2)P-3 (2) and fully characterized in solutio n. Evolution of H-2 from 4 and 5 results in the formation of the unsat urated 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 c enter 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 [M n(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 ligan ds.