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A series of rhenium(I) dinitrogen complexes were prepared containing predominantly amine ligands. On the basis of infrared and electrochemical data, a system was selected that was anticipated to be a suitable precursor for an elongated dihydrogen complex. Upon oxidation by AgOTf, the dinitrogen ligand of fac-[Re(PPh(3))(PF(3))(dien)(N(2))](+) (3) is replaced with triflate to generate 13, fac-[Re(PPh(3))(PF(3))(dien)(OTf)]OTf, a convenient precursor to rhenium(II) and rhenium(I) amine complexes. Reduction of the rhenium(II) triflate 13 under 1 atm of hydrogen gas generates the complex fac-[Re(dien)(PPh(3))(PF(3))(dien)(H(2))](+) (fac-14). T(1) measurements indicate a dihydrogen species with a H-H distance of 1.38 +/- 0.03 Å. The HD analog displays a J(HD) of 6.7 Hz, corresponding to a H-H distance of 1.31 +/- 0.03 Å, a value in good agreement with that determined from T(1) data and among the largest ever measured for an elongated dihydrogen system.

The complex trans-[Re(terpy)(Br)(PPh3)2][OTf] (2) (terpy = 2,2‘:6‘,2‘ ‘-terpyridine) is a convenient precursor to the electron-rich π-basic fragment {(terpy)(L)2Re}+ (L = t BuNC or PMe3). Reduction of 2 with activated magnesium in the presence of unsaturated organic molecules and an excess of either t BuNC or PMe3 yields complexes of the type trans-[(terpy)(L)2Re(η2-π)][OTf] (L = t BuNC or PMe3; π = olefin, aldehyde, or ketone). The dihapto-coordinated organic moieties show a preference for binding in the plane of the terpy ligand. Reaction of trans-[Re(terpy)( t BuNC)2(η2-acetone)][OTf] (9) with MeOTf yields an observable η2-ketonium complex. The electronic environment of these complexes has been probed by cyclic voltammetry, and the details of ligand exchange for the η2-ketone complexes are presented. Geometric features determined from X-ray crystal structure analyses of trans-[(terpy)( t BuNC)2Re(η2-cyclopentene)][OTf] (4) and trans-[(terpy)( t BuNC)2Re(η2-acetophenone)][OTf] (11) are reported.

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