Reactions of carbon dioxide with the electron-rich polyhydride complex [Mo(dmpe)2H4

Abstract

Abstract : The electron rich polyhydride complex molybdenum Mo(dmpe)2H4, formed by reduction of Mo(dmpe)2Cl2 under H2, reacts with CO2 to give a complex manifold of products containing formate, carbon dioxide and carbonate ligands. The final product of the reaction is Mo(dmpe)2(CO3)H2, in which reductive disproportionation of CO2 has led to a formation of a carbonate ligand. Two other products have been identified in which only two of the initial hydrides have been retained, one of which is the crystallographically characterized bis-formate Mo(dmpe)2(OCHO)2. The complex crystallizes in the monoclinic space group P and has an octahedral geometry with trans Eta 1-formate ligands. A precursor to 3 containing an Eta 2-CO2 ligand has been spectroscopically characterized as MKo(dmpe)2(CO2)(OCHO)H. Two complexes formed early in the reaction sequence, before elimination of H2, have been spectroscopically identified as Mo(dmpe)2(CO2)(OCHO)H3 and Mo(dmpe)2(OCHO)2H2. The characteristic absorptions between 1600 and 2800 cm-1 of the formate, carbonate, hydride, and carbon dioxide ligands in these molecules have been assigned on the basis of Carbon 13 and deuterium labelling studies.