Electrochemical Characterization and CO2 Reduction Reaction of a Family of Pyridazine-Bridged Dinuclear Mn(I) Carbonyl Complexes

Three recently synthesized neutral dinuclear carbonyl manganese complexes with the pyridazine bridging ligand, of general formula [Mn₂(μ-ER)₂(CO)₆(μ-pydz)] (pydz = pyridazine; E = O or S; R = methyl or phenyl), have been investigated by cyclic voltammetry in dimethylformamide and acetonitrile both under an inert argon atmosphere and in the presence of carbon dioxide. This family of Mn(I) compounds behaves interestingly at negative potentials in the presence of CO₂. Based on this behavior, which is herein discussed, a rather efficient catalytic mechanism for the CO₂ reduction reaction toward the generation of CO has been hypothesized.

Electrocatalytic proton reduction by an air-stable nickel(ii)-thiolato PNN pincer complex

We report an air-stable nickel(ii)-thiolato PNN pincer complex [(PNN)NiII(SC6H4Me)]+[MeC6H4SO3]- (PNN = 2-((di-tert-butylphosphinomethyl-6-diethylaminomethyl)pyridine)) which is capable of reducing protons at an overpotential of 0.54 V at low acid concentrations. The proton reduction can be catalysed using weak or strong acids such as acetic acid and trifluoroacetic acid respectively. In contrast, the chloro and nitrate derivatives of the nickel pincer complex behave as poorer catalysts. A mechanism accounting for the role of the ligand in proton reduction is also briefly outlined.

Mono- and bimetallic manganese-carbonyl complexes and clusters bearing imidazol(in)ium-2-dithiocarboxylate ligands

Five complexes with the generic formula fac-[MnBr(CO)₃(S₂C·NHC)] were obtained by reacting [MnBr(CO)₅] with a set of representative imidazol(in)ium-2-dithiocarboxylate zwitterions. These ligands are the adducts of N-heterocyclic carbenes (NHCs) and carbon disulfide. The mononuclear Mn(i) derivatives were coupled with Na[Mn(CO)₅] to afford bimetallic [Mn₂(CO)₆(S₂C·NHC)] clusters. Yet, the most convenient strategy to access these dinuclear Mn(0) products implied a direct carbonyl substitution from the [Mn₂(CO)₁₀] dimer. The molecular structures of three monometallic and four bimetallic compounds were elucidated by single crystal X-ray diffraction analysis. In the monometallic complexes, the NHC·CS₂ ligands exhibited a bidentate κ²-S,S' coordination mode with an S-C-S bite angle of about 116°. In the dinuclear clusters, the CS₂^- unit acted as a chelate toward one manganese center and as a pseudoallylic ligand toward the other one. The S-C-S bite angle was reduced to ca. 104°. Thus, the zwitterions displayed a remarkable flexibility, which also permitted a staggered arrangement of the carbonyl groups in the bimetallic systems. Examination of the [small nu, Greek, macron]_CO absorption bands on IR spectroscopy helped identify the presence of fac-Mn(CO)₃ or Mn₂(CO)₆ motifs, while the ¹³C NMR chemical shift of the CS₂^- moiety was a reliable indicator for monitoring its hapticity. Whereas the dinuclear clusters were air- and moisture-stable crystalline solids, mononuclear halido derivatives displayed only a limited stability under aerobic conditions. Both types of compounds underwent rather unselective, extensive fragmentations in the gas phase, in sharp contrast with the analogous rhenium derivatives that led to clean sequential decarbonylation processes upon collision-induced dissociation.

DFT study of the mechanism of hydrogen evolution catalysed by molecular Ni, Co and Fe catalysts containing a diamine–tripyridine ligand

Electrolysis of water to obtain hydrogen is a practical way to transform surplus electrical power into clean and sustainable hydrogen fuels.

Geometries, stabilities and fragmental channels of neutral and charged sulfur clusters: SnQ(n = 3–20, Q = 0, ±1)

We have performed unbiased searches for the global minimum structures of neutral and charged sulfur clusters relying on the CALYPSO method combined with DFT geometric optimization.

Electrochemical proton reduction catalysed by selenolato-manganese carbonyl complexes

Four manganese selenolato carbonyl complexes have been synthesized and used as electrocatalyst for proton reduction.