Activated Mn-MACHO Complexes Form Stable CO Adducts.

Manganese(I) carbonyl complexes bearing a MACHO-type ligand (HN(CH CH PR ) ) readily react in their amido form with CO to generate 4-membered {Mn-N-C-O} metallacycles. The stability of the adducts decreases with the steric demand of the R groups at phosphorous (R=isopropyl>adamantyl). The CO -adducts display generally a lower reactivity as compared to the parent amido complexes.

Pd(II)-catalyzed carboxylation of aromatic C─H bonds with CO.

The carboxylation of nonactivated C─H bonds provides an attractive yet hitherto largely elusive chemical process to synthesize carboxylic acids by incorporation of CO into the chemical value chain. Here, we report on the realization of such a reaction using simple and nonactivated arenes as starting materials. A computationally designed Pd(II) complex acts as organometallic single-component catalyst, and apart from a base, necessary for thermodynamic stabilization of the intermediates, no other additives or coreagents are required.

Factors Governing the Catalytic Insertion of CO into Arenes - A DFT Case Study for Pd and Pt Phosphane Sulfonamido Complexes.

The potential of Pd/Pt complexes for catalytic carboxylation of arenes with CO is investigated by means of computational chemistry. Recently we reported that the bis[(2-methoxyphenyl)phosphino]-benzenesulfonamido palladium complex 1 inserts CO reversibly in its Pd-C(aryl) bond generating carboxylato complex 2. In the present work we study how geometric and electronic factors of various ligands and substrates influence the overall activation barrier (energy span, ES) of a potential catalytic cycle for arene carboxylation comprising this elementary step.

Chiral colloids: homogeneous suspension of individualized SiO2 helical and twisted nanoribbons.

Finely tuned chiral nanometric silica fibers were synthesized based on sol-gel chemistry using organic self-assembly as a template. The optimization of the sol-gel process in acidic conditions allowed us to reduce the transcription time by a factor of 10. These nanohelices were successfully fragmented while preserving the fine internal structures from several micrometers to several hundreds of nanometers in length by a sonication method previously reported for carbon nanotubes.