Monocationic Trihydride and Dicationic Dihydride−Dihydrogen and Bis(dihydrogen) Osmium Complexes Containing Cyclic and Acyclic Triamine Ligands: Influence of the N−Os−N Angles on the Hydrogen−Hydrogen Interactions

New monocationic trihydride and dicationic dihydride−dihydrogen and bis(dihydrogen) osmium complexes with cyclic and acyclic triamines have been prepared and characterized. The treatment of OsH3Cl(PiPr3)2 (1) with 1,4,7-triazacyclononane (TACN) in toluene at 60 °C affords the monocationic trihydride [OsH3(TACN)(PiPr3)]Cl (2), which reacts with HBF4 to give the dicationic dihydride−dihydrogen [OsH2(TACN)(η2-H2)(PiPr3)](BF4)2 (3). Complex 1 also reacts with 1,4,7-triazacyclodecane (TACD) and bis(2-aminoethyl)amine (BAEA). Similarly to TACN, the reaction of 1 with TACD gives a monocationic trihydride derivative [OsH3(TACD)(PiPr3)]Cl (4), which in the presence of HBF4 generates a dicationic dihydride−dihydrogen [OsH2(TACD)(η2-H2)(PiPr3)](BF4)2 (5). However, the treatment of 1 with BAEA leads to the monocationic trihydride [OsH3(BAEA)(PiPr3)]Cl (6), which in the presence of HBF4 affords the dicationic bis(dihydrogen) [Os(BAEA)(η2-H2)2(PiPr3)](BF4)2 (7). The structures of 2−4 and 6 have been determined by X-ray diffraction analysis, and the position of the hydrogen atoms bonded to the metal center was confirmed by density functional theory calculations. The geometries of 2, 4, and 6 have been rationalized as pentagonal bipyramids and their behavior on the basis of the Nmeridional−Os−Nmeridional angle of the bipyramids.