Heterotetrametallic Re–Zn–Zn–Re Complex Generated by an Anionic Rhenium(I) β‑Diketiminate

We
report the synthesis of an anionic rhenium­(I) compound, Na­[Re­(η5-Cp)­(BDI)] (1; Cp = cyclopentadienide, BDI = N,N′-bis­(2,6-diisopropylphenyl)-3,5-dimethyl-β-diketiminate)
and initial investigations of its use as a strong chemical reductant
and metalloligand. Chemical oxidation of 1 gives a rare
example of a rhenium­(II) compound Re­(η5-Cp)­(BDI)
(2), while protonation of 1 yields the rhenium­(III)
hydride complex Re­(H)­(η5-Cp)­(BDI) (3). The reaction of 1 with ZnCl2 generated
both 2 and the zinc­(I) compound [ZnRe­(η5-Cp)­(BDI)]2 (4), which features a linear,
tetrametallic Re­(I)–Zn­(I)–Zn­(I)–Re­(I) core. Computational
studies of 4 were performed to characterize the metal–metal
bonding interactions; the results indicate a dative interaction from
rhenium to zinc and covalent bonding between the two zinc centers.
One-electron oxidation of 4 yielded both 2 and the triflate-bridged zinc­(II) complex [(μ-OTf)­ZnRe­(η5-Cp)­(BDI)]2 (5, OTf = trifluoromethanesulfonate).