: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

This review covers the recent advances in hydrosilylation chemistry mainly published in the last decade. Hydrosilylation of olefins is an important reaction for the production of various organosilicon compounds such as industrially important silicone products. Although the utility of platinum catalysts, Speier's and Karstedt's catalysts, has been widely recognized in this field for decades, development of more efficient, selective, and cheaper catalyst systems are still desired for more economical production of organosilicon materials having superior properties. In these contexts, much progress has been made in recent years. In the platinum catalysis systems, continuous progress has been made to further improve selectivity and activity. Several non-precious metal catalysts, such as Fe and Ni catalysts, with good efficiency and selectivity have been developed. Furthermore, unique chemo- and regioselectivity have been achieved not only by precious metal catalysts but also by non-precious metal catalysts. The utility of non-transition metal catalysts including early main group metals, Lewis acidic alane, borane and phosphonium salts as well as N-heterocyclic carbenes has also been disclosed.

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Hydrosilylation reaction of olefins: recent advances and perspectives

Well-defined transition metal hydrides in catalytic isomerizations

Chiral bicyclic NHC/Ir complexes for catalytic asymmetric transfer hydrogenation of ketones

https://digital.csic.es/bitstream/10261/155535/1/Revised%20Manuscript.pdf

Rhodium(I) Complexes with Ligands Based on N-Heterocyclic Carbene and Hemilabile Pyridine Donors as Highly E Stereoselective Alkyne Hydrosilylation Catalysts

The novel rhodium(I) complexes [RhCl(NBD)(NHC)] [NBD = norbornadiene, NHC = 1-benzyl-3-R-imidazolin-2-ylidene; R = Me (3a), Bz (3b), Tr (3c), tBu (3d)], containing on one nitrogen the benzyl substituent and on the other increasing bulky alkyl substituents were prepared. All the complexes display restricted rotation around the metal–carbene bond and yield conformational enantiomers. The stereodynamics and racemization barriers about the Rh–carbene have been determined by means of NMR spectroscopy for 3a–c, whereas for the bulkiest 3d only the lower limit (91 kJ mol−1) could be calculated. Whilst the racemization barriers obtained by DFT calculations for 3a,b and 3d matched the experimental values, in the case of 3c the latter (62.3 kJ mol−1) was much smaller with respect to the calculated one (101.7 kJ mol−1). The lower experimental barrier has been attributed to a dissociative pathway that produces a solvated ionic pair in the transition state. The catalytic activity of the neutral rhodium(I) complexes 3a and 3d in the hydrosilylation with HSiMe2Ph of the terminal alkynes PhC≡CH, TolC≡CH, nBuC≡CH, Et3SiC≡CH, and (CPh2OH)C≡CH has been investigated, and compared with the amide-functionalized [RhCl(NBD){1-(2-NHBoc-ethyl)-3-Me-imidazolin-2-ylidene}] (4) and with [RhCl(NBD){1-butyl-3-Me-imidazolin-2-ylidene}] (5).

N-Heterocyclic carbene rhodium(I) complexes containing an axis of chirality: dynamics and catalysis

A convenient method for the bulk preparation of environmentally safe perfluoroalkyl propen-1-yl ethers via isomerization of primary allyl ethers is presented. Herein the solvent-free isomerization was carried out in the presence of two ruthenium(II) complexes: the ruthenium-hydride [RuClH(CO)(PPh3)3] and the second generation Grubb's type catalyst dichloro[1,3-bis-(2,4,6-trimethylphenyl)-4,5-dimethylimidazol-2-ylidene](thien-2-ylmethylidene)(PCy3) ruthenium(II) known as CatMETium_RF3™. A variety of reaction parameters such as the catalyst loading, the use of a base and UV photoirradiation have been investigated. We found that the presence of Bu3N is beneficial to both catalytic systems and although CatMETium_RF3™ was shown to be more active than [RuClH(CO)(PPh3)3], the catalytic activity of the latter can also be sensibly improved by UV irradiation. Carrying out the isomerization reaction with 0.1 mol% of [RuClH(CO)(PPh3)3] under UV-irradiation led to a ca. 30% improvement of the conversion compared to the same reaction carried out under sunlight and to a 60% improvement when the reaction is carried out in the dark thus mimicking the conditions present in an autoclave.

Marta Anna Brucka

Papers

N-Heterocyclic carbene rhodium(I) complexes containing an axis of chirality: dynamics and catalysis

Solvent-free catalytic isomerization of perfluoroalkyl allyl ethers

Solvent-Free Catalytic Isomerization of Perfluoroalkyl Allyl Ethers.