Iron- and Organo-Catalyzed Borrowing Hydrogen for the Stereoselective Construction of Tetrahydropyrans.

Stereocontrolled oxa-Michael additions are challenging, given the high reversibility of the process, which ultimately leads to racemization of the newly formed stereocenters. When iron-catalyzed borrowing hydrogen from allylic alcohols was combined with a stereocontrolled organocatalytic oxa-Michael addition, a wide array of chiral tetrahydropyrans were efficiently prepared. The reaction could be performed in a diastereoselective manner from pre-existing stereocenters or enantioselectively from achiral substrates.

Mössbauer Spectroscopic and Computational Investigation of An Iron Cyclopentadienone Complex.

(Cyclopentadienone)iron carbonyl complexes have recently received particular attention for their use as catalysts in hydrogenation or transfer hydrogenation reactions including the N-alkylation of amines with alcohols. This is due to their easy synthesis from simple and cheap materials, air and water stabilities, and the crucial metal-ligand cooperation giving rise to unique catalytic properties. Here, we report a Mössbauer spectroscopic and computational investigation of such a complex and its corresponding activated species for dehydrogenation and hydrogenation reactions.

Effect of Distortions on the Geometric and Electronic Structures of One-Electron Oxidized Vanadium(IV), Copper(II), and Cobalt(II)/(III) Salen Complexes.

The ligands '-bis(3--butyl-5-methoxysalicylidene)-1,2-ethanediamine and '-bis(3--butyl-5-methoxysalicylidene)-1,3-propanediamine were chelated to V(IV)═O (, ), Cu(II) (, ), Co(II) (), and Co(III) (). The X-ray crystal structures of - were solved. The vanadium center in - resides in square pyramidal geometry, with an axially bound oxo ligand, whereas the metal ion displays a tetrahedrally distorted square planar geometry in -.

Tetranuclear and dinuclear phenoxido bridged copper complexes based on unsymmetrical thiosemicarbazone ligands.

We report on the synthesis of new dinucleating phenol-based "end-off" compartmental ligands HLMeH and HLMe2 bearing two different binding sites, one bis(2-methylpyridyl)aminomethyl (BPA) and one thiosemicarbazone (TSC) site, and their corresponding copper(ii) complexes 1t and 2d. With the ligand HLMeH, a tetranuclear entity (1t) has been isolated in the solid state, whereas with HLMe2, which differs from HLMeH by a methyl substituent on the N-terminal amino group of the TSC arm, a dinuclear form (2d) is obtained. X-ray crystallography analysis shows that the nuclearity di vs.

Electronic Structure and Reactivity of One-Electron-Oxidized Copper(II) Bis(phenolate)-Dipyrrin Complexes.

The sterically hindered bis(phenol)-dipyrrin ligands LH and LH were reacted with 1 equiv of copper(II) under ambient conditions to produce the copper radical complexes [Cu(L)] and [Cu(L)]. Their X-ray crystal structures show relatively short C-O bond distances (mean bond distances of 1.287 and 1.