Immobilization of a Soluble Metal Complex in an Organic Network. Remarkable Catalytic Performance of a Porous Dialkoxyzirconium Polyphenoxide as a Functional Organic Zeolite Analogue

Abstract

Treatment of anthracenebisresorcinol 1 (a tetraphenol) with Zr(OtBu)4 in THF results in polycondensation to give an O−Zr−O network and affords a poly(dialkoxyzirconium phenoxide), 14-·2[Zr(OtBu)2] (Zr host), in quantitative yield as an insoluble, amorphous, microporous powder with a particle size of ∼0.7 μm, a pore size of ∼0.7 nm, and a specific surface area of ∼200 m2/g. The powder exhibits reversible Langmuir-type adsorption/desorption of N2 at 77 K and hexane at 298 K. Adsorption and coadsorption of ethyl acetate, benzene, and other polar and apolar guests also occurs readily at 298 K. The Zr host catalyzes the Diels−Alder reaction of acrolein with 1,3-cyclohexadiene in a remarkable manner. As a solid metal−organic catalyst, it has a formula-based turnover rate constant of 40 h-1, which far exceeds those of its components, i.e., the soluble Lewis acid Zr(OtBu)4 (0.1 h-1) and the hydrogen-bonded insoluble organic network 1 (0.3 h-1). The solid catalyst can be easily separated from the organic product, ...