Multidimensional CuII incorporated POMs [KI2CuII(en)2(β-Mo8O26)]n and [KI2CuII3(H2O)10(W12O40)0.2(H2O)]n: Syntheses, structures and catalytic epoxidation

Abstract

Two CuII incorporated polyoxometalate compounds, [KI2CuII(en)2(β-Mo8O26)]n (1) and [KI2CuII3(H2O)10(W12O40)·2(H2O)]n (2), have been synthesized and structurally characterized. In complex 1, the Mo8O264− anion shows an archetypal β-type octamolybdate that contains eight {MoO6} subunits which are further attached by a KIO8 unit to present a 1D chain. Consecutive 1D layers are connected by a mononuclear [Cu(en)2O2]2+ subunit to generate a 2D framework in the crystallographic ab plane. In complex 2, the W12O408− anion is a typical Keggin-type polyoxo anion containing twelve {WO6} octahedra which are alternately coordinated to KIO4 tetrahedra to generate a 1D chain. These 1D layers are interconnected by [Cu(H2O)]2+ synchronously to form a 2D framework in the crystallographic ac plane. Catalytic activity studies of complex 1 gave 91% styrene conversion with 72% epoxide selectivity and 85% cyclohexene conversion with 65% epoxide selectivity and those for complex 2 showed 88% styrene conversion with 70% epoxide selectivity and 81% cyclohexene conversion with 63% epoxide selectivity.