Mixed Metal Multinuclear Cr(III) Cage Compounds and Coordination Polymers Based on Unsubstituted Phenolate: Design, Synthesis, Mechanism, and Properties

Abstract

Oxidative substitution reactions of chromium(II) chloride with lithium phenoxide in the presence of water give access to new polynuclear chromium(III) aryloxide complexes and coordination polymers. While a one-dimensional coordination polymer based on chromium(III), [Cr2(μ3-OPh)2(μ-OPh)6(μ-OH)(μ3-Li)4(μ3-Cl)2Li(THF)6]n, is first obtained by serendipity, the controlled addition of water to the initial Cr(II) complex as well as variation of the stoichiometry lead to three new discrete chromium(III) aggregates, namely, [Cr(OPh)4(μ-OH)Li2(THF)3]2, [Cr3Li3(OPh)9(μ3-OH)(μ3-O)(THF)6], and [Cr4(μ-OPh)8(μ3-OH)6(μ-OH)2Cl2Li6(THF)6]·2THF. The use of deuterated species allowed confirmation of the oxidation based on the addition of water by detection of H2, HD, and D2. During these investigations, we have also identified a THF-adduct of chromium(II) chloride, [CrCl2(THF)2], used in the literature as a precursor in numerous syntheses, but with a hitherto unknown structure.