Département de chimie moléculaire

One advantage of using homogeneous mol. catalysts vs. their heterogeneous counterparts for CO2 redn. is the greater degree of control one usually retains over the selectivity of the catalyst. In this context, a pair of new Mn(I) tricarbonyl species, based on the N,N'-coordinated 1,10-phenanthroline- 5, 6- dione (phen-dione) ligand, were synthesized and characterized by spectroscopic methods and x-ray diffraction. They exhibit excellent selectivity for homogeneous catalytic CO2 redn. to CO or HCOOH through electrochem. or photochem. activation, resp. Under the latter particularly, switching the solvent from DMF to MeCN remarkably enhances the selectivity of the redn. reaction towards formic acid. To obtain deeper mechanistic insight, the evolution of the catalysts and products in soln. during the catalytic processes was studied by combined electrochem., chromatog. and spectroscopic methods the presence of the $π$-accepting, redox-active phen-dione ligand leads to different reduced intermediates compared with std. 2,2'-bipyridine and 1,10-phenanthroline complexes, with the two 1st redox processes remaining localized on the ligand. [on SciFinder(R)]