Styrene oxidation catalyzed by copper(II) C-scorpionates in homogenous medium and immobilized on sucrose derived hydrochars

Abstract

Mononuclear C-scorpionate copper(II) complexes [CuCl2{κ3-RC(R1-pz)3}[R = R1 = H (1), R = CH2OH, R1 = H (2) and the new R = H, R1 = 3,5-Me2 (3)] supported on sucrose derived hydrochars are the first recyclable tris(pyrazol-1-yl)methane catalysts used so far for the selective oxidation of styrene to benzaldehyde. Remarkably, a benzaldehyde yield of over 60% (100% selectivity) with a TOF = 1.3 × 104 was obtained after only 5 min reaction in homogeneous conditions. The immobilization of 1–3 at functionalized hydrochars led to solvent-free recyclable catalytic systems for the mentioned reaction, that, although leading to slightly modest benzaldehyde yields (up to 52%), require much lower amounts of oxidant than the homogeneous analogs. The effects of scorpionate properties as well as of reaction parameters (e.g., reaction time, amount of catalyst and oxidant or type of solvent) on the performance of the above catalytic systems are discussed.