Lars A. van der Veen

Hydroformylation of Internal Olefins to Linear Aldehydes with Novel Rhodium Catalysts

Unprecedented high activities and selectivities were observed in the hydroformylation of internal octenes to linear products using rhodium catalysts with rigid diphosphane ligands. Dibenzophosphole 1 and a phenoxaphosphane analogue with bite angles of 120 and 119°, respectively, are suited for this.

A robust, environmentally benign catalyst for highly selective hydroformylation

By a sol-gel process a rhodium complex containing a diphosphane with a large natural P-Rh-P bite angle is covalently anchored in a silica matrix (see picture). The immobilized catalyst is a very selective hydroformylation catalyst that is completely and conveniently separated from the product and can be reused in numerous cycles.

Hydroxycarbonylation of styrene with palladium catalysts The influence of the mono- and bidentate phosphorus ligand.

Abstract A systematic study of the hydroxycarbonylation reaction of styrene is described. The effect of the catalytic precursor and the reaction conditions on the results of the reaction was investigated. Several monophosphines (PPh 3 , P(p-Tol) 3 , P(p-C 6 H 4 OMe) 3 , P(p-C 6 H 4 F) 3 , PPh 2 (o-Tol), PMe 3 , PCy 3 ) and diphosphines (dppe, dppp, dppb, dppf, HomoXantphos, DPEphos, Xantphos, BDPP, BINAP, BPPFA, DIOP) were applied to control the regioselectivity of the reaction. The effect of the bite angle of the diphosphines has also been studied. Catalysts containing monophosphines as ligands give 2-phenylpropanoic acid as the major product and the 3-phenyl propanoic acid is obtained when diphosphines are used. Two catalytic cycles are proposed to explain the influence of the different palladium precursors with mono- and diphosphines.

Neuartige Rhodiumkatalysatoren für die Hydroformylierung interner Olefine zu linearen Aldehyden

Ausergewohnlich hoch sind die Aktivitaten und die Selektivitaten bei der Hydroformylierung interner Octene zu linearen Produkten mit Rhodiumkatalysatoren, die starre Diphosphanliganden enthalten. Hierfur eignen sich das Dibenzophosphol 1 und ein analoger Phenoxaphosphanligand mit Biswinkeln von 120° bzw. 119°.

The Sulfonium Ion Linkage in Myeloperoxidase DIRECT SPECTROSCOPIC DETECTION BY ISOTOPIC LABELING AND EFFECT OF MUTATION

The heme group of myeloperoxidase is covalently linked via two ester bonds to the protein and a unique sulfonium ion linkage involving Met243. Mutation of Met243 into Thr, Gln, and Val, which are the corresponding residues of eosinophil peroxidase, lactoperoxidase, and thyroid peroxidase, respectively, and into Cys was performed. The Soret band in the optical absorbance spectrum in the oxidized mutants is now found at approximately 411 nm. Both the pyridine hemochrome spectra and resonance Raman spectra of the mutants are affected by the mutation. In the Met243 mutants the affinity for chloride has decreased 100-fold. All mutants have lost their chlorination activity, except for the M243T mutant, which still has 15% activity left. By Fourier transform infared difference spectroscopy it was possible to specifically detect the13CD3-labeled methionyl sulfonium ion linkage. We conclude that the sulfonium ion linkage serves two roles. First, it serves as an electron-withdrawing substituent via its positive charge, and, second, together with its neighboring residue Glu242, it appears to be responsible for the lower symmetry of the heme group and distortion from the planar conformation normally seen in heme-containing proteins.

The effect of ligand donor atoms on the regioselectivity in the palladium catalyzed allylic alkylation.

Abstract The regioselectivity of the palladium catalyzed allylic alkylation was studied systematically using bidentate ligands based on a xanthene backbone, bearing different donor atoms. The nature of the ligand donor atoms has a pronounced influence on the regioselectivity of the reaction. The results can be explained by a mechanism that distinguishes two ‘stages’ in the alkylation reaction. Ligands bearing strong π-acceptor donor atoms induce the formation of branched products (60% for the PP derivative), whereas the use of ligands with weak π-acceptor donor atoms mainly yields linear products (>99% for the NN derivative).

Novel arsine ligands for selective hydroformylation of alk-1-enes employing platinum/tin catalysts

The synthesis and application of new wide bite angle arsine based ligands in the platinum/tin-catalysed hydroformylation of oct-1-ene is reported; an unprecedented high activity and selectivity is obtained employing a mixed phosphine/arsine ligand.

Wide Bite Angle Amine-, Arsine, and Phosphine Ligands in Rhodium-, and Platinum/tin-catalysed Hydroformylation.

New wide bite angle amine, arsine and mixed phosphineamine and phosphinearsine ligands based on xanthene backbones were synthesized. The co-ordination chemistry and the catalytic performance of these ligands were compared to those of the parent phosphine ligands. The amine based xanthene ligands do not form rhodium–hydride complexes and therefore give very poor rhodium hydroformylation catalysts. The catalytic performance of the xantarsine and the mixed xantphosarsine ligands is comparable with that of the xantphos ligands and they form similar (ligand)Rh(CO)2H and [(ligand)Rh(CO)2]2 complexes. In the platinum/tin-catalysed hydroformylation the xantarsine and the mixed xantphosarsine ligands proved to be superior to the xantphos ligands. The remarkably high selectivity and activity that is displayed by the mixed xantphosarsine ligand is explained by its wide natural bite angle and the formation of cis co-ordinated platinum complexes.