Catalytic hydroxylation of 1-propanol by platinum NCN and PCP pincer complexes using CuCl 2 as oxidant

Abstract

The novel PCP-pincer Pt(II) complex, PtCl { C 6 H 3 - 2 , 6 - ( OPPr 2 i ) 2 } ( 1 ) has been prepared and characterized by 1H, 31P, and 13C NMR spectroscopy. The molecular structure of 1 has been determined through a single-crystal X-ray diffraction study. The pincer-ligated platinum complexes 1 and PtCl{C 6H 3-2,6-(CH 2NEt 2) 2} ( 2) have been explored as catalysts for the hydroxylation of 1-propanol to 1,3-propanediol under mild conditions. Product ratios and turnover numbers achieved with both complexes compare favorably to those obtained with [PtCl 4] 2−. Moreover, the pincer complexes catalyze this transformation even upon replacement of PtCl 4 by the more economical CuCl 2 as the requisite stoichiometric oxidant. Analysis of the reaction mixture by 31P NMR spectroscopy following the hydroxylation of 1-propanol by 1 in the presence of CuCl 2 revealed that 1 is partially converted to the ring substituted complex, PtCl { 3 - Cl - C 6 H 2 - 2 , 6 - ( OPPr 2 i ) 2 } ( 3 ) . The molecular structure of 3 has been determined through a single-crystal X-ray diffraction study.