Photocatalyzed Synthesis of 3-Substituted Phthalides: A Key Access to (±)-Herbaric Acid

An efficient organophotocatalyzed protocol was developed for the preparation of 3-substituted phthalides. The presented transformation was performed under particularly mild conditions within 6 h and was ultimately applied to a precursor of the herbaric acid.     

T-shaped Ni0 Systems Featuring Cationic Tetrylenes: Direct Observation of L/Z-type Ligand Duality,and Alkene Hydrogenation Catalysis

We report a facile synthetic method for accessing rare T-shaped Ni⁰ species, stabilised by low-coordinate cationic germylene and stannylene ligands which behave as Z-type ligands toward Ni⁰. An in-depth computational analysis indicates significant Ni^d→E^p donation (E=Ge, Sn), with essentially no E→Ni donation. The tetrylene ligand's Lewis acidity can be modulated in situ through the addition of a donor ligand, which selectively binds at the Lewis acidic tetrylene site. This switches this binding centre from a Z-type to a classical L-type ligand, with a concomitant geometry switch at Ni⁰ from T-shaped to trigonal planar. Exploring the effects of this geometry switch in catalysis, isolated T-shaped complexes 3 a – c and 4 a – c are capable of the hydrogenation of alkenes under mild conditions, whilst the closely related trigonal planar and tetrahedral Ni⁰ complexes 5 , D , and E , which feature L-type chloro- or cationic-tetrylene ligands, are inactive under these conditions. Further, addition of small amounts of N-bases to the catalytic systems involving T-shaped complexes significantly reduces turnover rates, giving evidence for the in situ modulation of ligand electronics for catalytic switching.     

Static and Dynamic Magnetic Properties of a Co(II)-Complex with N2O2 Donor Set – A Theoretical and Experimental Study

A representative Co(II) based single ion magnet (SIM) with N₂O₂ donor set and distorted pseudo-tetrahedral geometry has been synthesized and characterized to study the atomic and electronic structure. DC magnetometry results have been evaluated by means of a phenomenological Hamiltonian approach regarding zero field splitting (ZFS) parameters and compared with results from ab-initio multi-reference CASSCF (complete active space self-consistent field) calculations and qualitative ligand field theory (AILFT). Profound investigation of spin-lattice relaxation with the variation of temperature (from 1.8 to about 8 K) and magnetic field (at 14 different fields from zero up to 1 T) have been performed based on AC magnetometry. Under an applied dc magnetic field, spin-lattice relaxation occurs via a direct process with T² temperature dependence due to limited heat transfer at very low temperature and above 5 K relaxation by an Orbach process with an energy barrier of ≈80 K dominates.