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

Abstract

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 OsH(3)Cl(P(i)Pr(3))(2) (1) with 1,4,7-triazacyclononane (TACN) in toluene at 60 degrees C affords the monocationic trihydride [OsH(3)(TACN)(P(i)Pr(3))]Cl (2), which reacts with HBF(4) to give the dicationic dihydride-dihydrogen [OsH(2)(TACN)(eta(2)-H(2))(P(i)Pr(3))](BF(4))(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 [OsH(3)(TACD)(P(i)Pr(3))]Cl (4), which in the presence of HBF(4) generates a dicationic dihydride-dihydrogen [OsH(2)(TACD)(eta(2)-H(2))(P(i)Pr(3))](BF(4))(2) (5). However, the treatment of 1 with BAEA leads to the monocationic trihydride [OsH(3)(BAEA)(P(i)Pr(3))]Cl (6), which in the presence of HBF(4) affords the dicationic bis(dihydrogen) [Os(BAEA)(eta(2)-H(2))(2)(P(i)Pr(3))](BF(4))(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 N(meridional)-Os-N(meridional) angle of the bipyramids.