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

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posted on 20.12.2018, 00:00 by Trevor D. Lohrey, Laurent Maron, Robert G. Bergman, John Arnold
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).