Sorptive Reconstruction of CuMCl₄ (M = Al and Ga) upon Small-Molecule Binding and the Competitive Binding of CO and Ethylene

Carbonyl adducts to CuMCl4 (M = Al and Ga) have been characterized by single-crystal and/or powder X-ray diffraction, IR and diffuse reflectance UV/vis spectroscopy. Up to two equivalents of carbon monoxide (∼200 cm3/g relative to stp) are sorbed at room temperature, with equilibrium binding pressures of below 0.5 atm of CO. The carbonyl bonding is shown to be nonclassical, implicating the dominance of σ-bonding and absence of π-back-bonding. Analysis of the crystalline structures of the parent and adduct phases provides an atomistic picture of the sorptive reconstruction reaction. Comparison of the reactivity of CO and ethylene with these CuMCl4 materials, as well as other copper(I) halide compounds that exhibit classical and nonclassical modes of bonding, demonstrates the ability to tune the reactivity of the crystalline frameworks with selectivity for carbon monoxide or olefins, respectively.