Synthesis of rhenium complexes that contain the [(C6F5NCH2CH2)3N]3- ligand

The reaction between [Et4N](2)[ReOCl5] and (C6F5NHCH2CH2)(3)N (H-3[N3NF]) in CH3CN at room temperature in the presence of NEt3 yielded air stable, emerald green, diamagnetic [(C6F5NCH2CH2)(2)NCH2CH2NHC6F5]Re(O)Cl (1). The reaction between 1 and Ta(CH-t-Bu)(THF)(2)Br-3 gave paramagnetic [N3NF]ReBr (2). An X-ray structure of a sample of 2 showed it to be analogous to that of [N3NF]MoCl. Reduction of 2 by methyllithium (or more conveniently by Mg) in the presence of a variety of two-electron ligands gave complexes of the type [N3NF]Re(L) (L = H-2, ethylene, propylene, CO, N-2, phosphines, pyridine, tetrahydrothiophene, acetonitrile, or silanes). An X-ray structure of [N3NF]Re(ethylene) showed eta(2)-ethylene to be bound in the apical "pocket" with its C-C axis lying in one of the N-ax-Re-N-eq planes. Protonation of the PMe3 complex gave an authentic hydride phosphine complex, {[N3NF]Re(H)(PMe3)}(+), but protonation of other phosphine complexes gave species in which coupling between H and P is relatively large (similar to 60 Hz) and therefore that are believed to have some {[N3NF]Re(eta(2)-HPRxH3-x)}(+) character. An X-ray study of {[N3NF]Re(H)(PHPh2)}(+) confirmed that one proton is terminally bound to phosphorus and that the phosphorus is "off-axis" in order to accommodate the "hydride" in the same plane.