Sulfur substitution in a Ni(cyclam) derivative results in lower overpotential for CO2 reduction and enhanced proton reduction.

The replacement of the opposing nitrogen atoms in 1,4,8,11-tetraazacyclotetradecane (cyclam) with two sulfur atoms in 1,8-dithia-4,11-diazacyclotetradecane (dithiacyclam) enables the electrochemical reduction of protons and CO2via the corresponding nickel(ii) complex at more positive potentials. In addition, a 10-fold enhancement in the proton reduction rate of [Ni(dithiacyclam)]2+ relative to [Ni(cylcam)]2+ was observed. The study provides vital insight into Nature's choice of employing predominantly sulfur based ligand platforms in achieving biological proton and CO2 reductions.

Spectroscopic and reactivity differences in metal complexes derived from sulfur containing Triphos homologs.

Herein, we report a simplified method for the synthesis of Triphos homologs H3CC(CH2X)n(CH2Y)3-n (X = SPh, Y = PPh2, n = 0-3). The multidentate compounds were tested for their potential to coordinate metals such as Ni, Fe, and Mo under the same experimental conditions. Cyclic voltammetry, spectroelectrochemical IR investigations as well as DFT calculations were used to examine the electronic alterations in a series of [{H3CC(CH2X)n(CH2Y)3-n}Mo(CO)3] complexes and to evaluate their potential to open coordination sites or to release CO upon oxidation or in the presence of different solvents. In addition, we demonstrate that the catalytic hydrosilylation of N,N-dimethylbenzamide to N,N-dimethylbenzylamine is influenced by the applied tripodal ligand. Our investigations show the high potential of such manipulations to selectively alter the dynamics of the binding properties of Triphos-metal complexes and their reactivity.