Examination of Protonation-Induced Dinitrogen Splitting by EXAFS Spectroscopy.

The splitting of dinitrogen into nitride complexes emerged as a key reaction for nitrogen fixation strategies at ambient conditions. However, the impact of auxiliary ligands or accessible spin states on the thermodynamics and kinetics of N-N cleavage is yet to be examined in detail. We recently reported N-N bond splitting of a {Mo(μ:η:η-N)Mo}-complex upon protonation of the diphosphinoamide auxiliary ligands.

Electronically Asynchronous Transition States for C-N Bond Formation by Electrophilic -Nitrene Radical Complexes Involving Substrate-to-Ligand Single-Electron Transfer and a Cobalt-Centered Spin Shuttle.

The oxidation state of the redox noninnocent tetra-amido macrocyclic ligand (TAML) scaffold was recently shown to affect the formation of nitrene radical species on cobalt(III) upon reaction with PhI=NNs [van Leest N. P.; J.

Ligand Redox Noninnocence in [Co(TAML)] Complexes Affects Nitrene Formation.

The redox noninnocence of the TAML scaffold in cobalt-TAML (tetra-amido macrocyclic ligand) complexes has been under debate since 2006. In this work, we demonstrate with a variety of spectroscopic measurements that the TAML backbone in the anionic complex is truly redox noninnocent and that one-electron oxidation affords . Multireference (CASSCF) calculations show that the electronic structure of is best described as an intermediate spin ( = 1) cobalt(III) center that is antiferromagnetically coupled to a ligand-centered radical, affording an overall doublet (S = /) ground-state.

[FeFe]-Hydrogenase Mimic Employing κ-,-Pyridine Bridgehead Catalyzes Proton Reduction at Mild Overpotential.

Two novel κ-,-pyridine bridged [FeFe]-Hase mimics ( and ) have been prepared and are shown to function as efficient molecular catalysts for electrocatalytic proton reduction. The elemental and structural composition of the complexes are confirmed by NMR and IR spectroscopy, high-resolution mass spectrometry and single-crystal X-ray diffraction. Electrochemical investigations reveal that the complexes reduce protons at their first reduction potential, resulting in the lowest overpotential (120 mV) ever reported for [FeFe]-Hase mimics in proton reduction catalysis when mild acid (phenol) is used as proton source.

Spectroscopic Investigation of the Activation of a Chromium-Pyrrolyl Ethene Trimerization Catalyst.

1-Hexene is an important α-olefin for polyethylene production and is produced from ethene. Recent developments in the α-olefin industry have led to the successful commercialization of ethene trimerization catalysts. An important industrially applied ethene trimerization system uses a mixture of chromium 2-ethylhexanoate, AlEt, AlEtCl, and 2,5-dimethylpyrrole (DMP).