An Air‐ and Water‐Tolerant Zinc Hydride Cluster That Reacts Selectively With CO₂

Abstract

The reaction of [Zn3Cl3L], in which L3− is a tris(β‐diketiminate) cyclophane, with K(sBu)3BH afforded [Zn3(μ‐H)3L] (2), as confirmed by NMR spectroscopy, NOESY, and X‐ray crystallography. The complex 2 was air‐stable and unreactive towards water, methanol, and other substrates (e.g., nitriles) at room temperature over 24 h but reacted with CO2 (ca. 1 atm) to generate [Zn3(μ‐H)2(μ‐1,1‐O2CH)] (3). In contrast, [Zn3(OH)3L] (4) was found to be unreactive toward CO2 over the course of several days at 90 °C.

Correlating Bridging Ligand with Properties of Ligand-Templated [MnII3X3]3+Clusters (X = Br–, Cl–, H–, MeO–)

“…50 We speculate that the unusually long Mn−H interactions result from the ability of the relatively rigid cyclophanate ligand to impose long M•••M distances, as has been observed for the other previously reported members of the isostructural M 3 H 3 L series (Table 2). 37,39 A similar conclusion is obtained if one considers the metal metal−metal distances rather than the purported metal−hydride bond lengths.…”

“…Similarly, the [Mn 3 X 3 ] 3+ ring is expected to weakly interact with the π-cloud of the two arene caps, thereby allowing polarization of the benzene π-systems that influences Mn II exchange within clusters templated with L 3− . 37 We simultaneously modeled the isothermal magnetization and the dc susceptibility data in our EasySpin simulations. As noted above we placed a constraint on the magnitude of D, primarily because of the expected quenched orbital angular momentum in the d 5 S Mn(II) = 5/2 ions.…”

Cyclophanes as Platforms for Reactive Multimetallic Complexes

“…This specificity persists across the series with the triZn congener even being unreactive towards water over 24 h (Figure 5). 56 Given the invariance of reactivity as a function of metal ion type, the ligand is the likely source of the specificity and substrate selection and dictated by the electrostatics of the pocket surrounding the hydride donor. Changes to the cyclophane ligand to modulate these electrostatics will be key to identifying the factors responsible for this substrate selectivity.…”

“…Undoubtedly, the breadth of accessible reaction manifolds for these hydrides ( i.e., hydride, H-atom, proton) provide precedent for the proposed diverse reactivities for comparable proposed metal hydride intermediates of metallocofactors. 56…”

“…hydride, H-atom, proton) provide precedent for the proposed diverse reactivities for comparable proposed metal hydride intermediates of metallocofactors 56. ■ CONCLUDING REMARKSRecent work on polynuclear metal complexes actualizes the ex vivo reactivity promised from metal cluster cofactors in metalloproteins, opening new opportunities to interrogate the reaction mechanisms for small molecule activation at biological clusters.…”