Zirconium(IV)-Catalysed Hydrosilylation of Organic Carbonates and Polycarbonates Household Wastes into Alcohol Derivatives.

The Schwartz's reagent Cp2Zr(H)Cl is a well known stoichiometric reagent for the reduction of unsaturated organic molecules but it has rarely been used in catalytic transformations. Herein, we describe the reduction of a variety of organic carbonates using the catalyst Cp2Zr(H)Cl in combination with Me(MeO)2SiH (DMMS) as reductant. This method was further applied to the reductive depolymerization of some polycarbonate materials and yielded silylated alcohols and diols in mild conditions. This method for the recycling polycarbonates is characterized by its stability to the additives contained in household plastics as well as its ability to selectively depolymerize the polycarbonate PC-BPA when mixed with the polyester PET. Experimental investigations brought evidences on a mechanism based on the succession of a three steps sequence comprising the hydrozirconation of the carbonyl fragment, thermal σ C-O bond cleavage, and an ultimate Zr-OR/Si-H σ-bond metathesis reaction to regenerate the hydride catalyst.