89463-02-5Relevant academic research and scientific papers
Molecular Cobalt Complexes with Pendant Amines for Selective Electrocatalytic Reduction of Carbon Dioxide to Formic Acid
Roy, Souvik,Sharma, Bhaskar,Pécaut, Jacques,Simon, Philippe,Fontecave, Marc,Tran, Phong D.,Derat, Etienne,Artero, Vincent
, p. 3685 - 3696 (2017)
We report here on a new series of CO2-reducing molecular catalysts based on Earth-abundant elements that are very selective for the production of formic acid in dimethylformamide (DMF)/water mixtures (Faradaic efficiency of 90 ± 10%) at moderate overpotentials (500-700 mV in DMF measured at the middle of the catalytic wave). The [CpCo(PR2NR′2)I]+ compounds contain diphosphine ligands, PR2NR′2, with two pendant amine residues that act as proton relays during CO2-reduction catalysis and tune their activity. Four different PR2NR′2 ligands with cyclohexyl or phenyl substituents on phosphorus and benzyl or phenyl substituents on nitrogen were employed, and the compound with the most electron-donating phosphine ligand and the most basic amine functions performs best among the series, with turnover frequency >1000 s-1. State-of-the-art benchmarking of catalytic performances ranks this new class of cobalt-based complexes among the most promising CO2-to-formic acid reducing catalysts developed to date; addressing the stability issues would allow further improvement. Mechanistic studies and density functional theory simulations confirmed the role of amine groups for stabilizing key intermediates through hydrogen bonding with water molecules during hydride transfer from the Co center to the CO2 molecule.
Steric and electronic control of the Arbuzov reaction in transition-metal halides: A 1H and 31P NMR study of the reaction of [CpCo(L L)X]+ complexes (L L = N, P, as chelate ligands; X- = Cl-, Br-, I-, CN-) with P(OCH3)3
Landon, Shayne J.,Brill, Thomas B.
, p. 1266 - 1271 (2008/10/08)
Synthesis of a series of complexes, [CpCo(L L)X]+ (L L = N, P, As chelate ligands; X- = Cl-, Br-, I-, CN-), was undertaken with the goal of characterizing the Michaelis-Arbuzov reaction between these complexes and P(OCH3)3. 1H and 31P NMR results provide support for the previously postulated two-step mechanism involving an initial equilibrium reaction [CpCo(L L)X]+ + P(OCH3)3 ? {CpCo(L L)[P(OCH3)3]}2+ + X- followed by alkylation of X- to produce an organometal-phosphonate complex, {CpCo(L L)[P(OCH3)3]}2+ + X- → {CpCo(L L)[P(O)(OCH3)2]}+ + CH3X. Several of the intermediate phosphite dications were synthesized and characterized. They enable the above reactions to be qualitatively separated. The initial reaction was quenched by sterically bulky chelate ligands. The rate of the overall reaction parallels the electron donor power of the attacking nucleophile (CN- > I- > Br- > Cl-) and also depends on the donor atoms of L L (N > P). Chelate dissociation occurs when L L = As. The results for [CpCo(L L)X]+ and other transition metal-halide complexes are discussed in terms of why the Arbuzov reaction takes place in some of these complexes but not with others.
