Synthesis of Rhenium Complexes That Contain the [(C6F5NCH2CH2)3N]3- Ligand

The reaction between [Et4N]2[ReOCl5] and (C6F5NHCH2CH2)3N (H3[N3NF]) in CH3CN at room temperature in the presence of NEt3 yielded air stable, emerald green, diamagnetic [(C6F5NCH2CH2)2NCH2CH2NHC6F5]Re(O)Cl (1). The reaction between 1 and Ta(CH-t-Bu)(THF)2Br3 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 = H2, ethylene, propylene, CO, N2, phosphines, pyridine, tetrahydrothiophene, acetonitrile, or silanes). An X-ray structure of [N3NF]Re(ethylene) showed η2-ethylene to be bound in the apical “pocket” with its C−C axis lying in one of the Nax−Re−Neq planes. Protonation of the PMe3 complex gave an authentic hydrido phosphine complex, {[N3NF]Re(H)(PMe3)}+, but protonation of other phosphine complexes gave species in which coupling between H and P is relatively large (∼60 Hz) and therefore that are believed to have some {[N3NF]Re(η2-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.