Preparation of rhenium(I) and rhenium(II) amine dinitrogen complexes and the characterization of an elongated dihydrogen species

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(PPh3)(PPh3)-(dien)(N-2)](+) (3) is replaced with triflate to generate 13,fac-[Re(PPh3)(PF3)(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)(PPh3)(PF3)(dien)(H-2)](+) (fac-14). T-1 measurements indicate a dihydrogen species with a H-H distance of 1.38 +/- 0.03 Angstrom. The HD analog displays a J(HD) Of 6.7 Hz, corresponding to a H-H distance of 1.31 +/- 0.03 Angstrom; a value in good agreement with that determined from T-1 data and among-the largest ever measured for an elongated dihydrogen system.