Preparation, X-ray Structures, and NMR Spectra of Elongated Dihydrogen Complexes with Four- and Five-Coordinate Tin Centers

Complex OsH3(SnPh2Cl){[η2-CH2C(CH3)]PiPr2}(PiPr3) (1) undergoes protonation−addition of benzoic acid to give
the elongated dihydrogen derivative Os(SnPh2Cl)(κ2-O2CPh)(η2-H2)(PiPr3)2 (2). In solution the tin atom exchanges with the
osmium on the chloride ligand by one of the oxygen atoms of
the carboxylate group to afford (3). Treatment of the latter with 1.0 equiv of benzoic
acid leads to
(4). The elongated dihydrogen ligands of 2 and 3 show blocked
rotation on the NMR time scale, whereas the hydrogen atoms
undergo quantum exchange coupling. The X-ray structures of
3 and 4 are also reported.