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.