Synthesis and structural characterization of bis(2-pyridylthio)(p-tolylthio)methyl zinc complexes and the catalytic hydrosilylation of CO2

Abstract

Bis(2-pyridylthio)(p-tolylthio)methane, [BptmSTol]H, has been synthesized by treatment of a 2:1 mixture of 2-mercaptopyridine and p-thiocresol with NaH, followed by addition of CHI3. Access to zinc complexes is provided by the reaction of [BptmSTol]H with Zn[N(SiMe3)2]2 to afford [BptmSTol]ZnN(SiMe3)2, from which the halide derivatives [BptmSTol]ZnX (X = Cl, Br, I) are obtained via reaction with Me3SiX (X = Cl, Br, I), and the formate complex, [BptmSTol]ZnO2CH, is obtained by treatment with CO2 in the presence of PhSiH3. The molecular structures of [BptmSTol]ZnN(SiMe3)2, [BptmSTol]ZnX (X = Cl, Br, I) and [BptmSTol]ZnO2CH have been determined by single crystal X-ray diffraction, which indicate that the four coordinate zinc centers adopt structures that are intermediate between idealized trigonal monopyramidal and seesaw geometries. [BptmSTol]ZnO2CH is a catalyst for the hydrosilylation of CO2 by (RO)3SiH at room temperature to afford the silyl formate, HCO2Si(OR)3.