Chromium‐Arene Complexes

and, Hans-Günther Schmalz; Dehmel, Florian

doi:10.1002/9783527619405.ch3l

Cited by 9 publications

(2 citation statements)

References 161 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The fragility of (arene)chromium-based phosphine-olefin ligands 1 is ascribed to the presence of the (arene)chromium substructure, since they suffer from photoinduced oxidative degradation (Scheme ). We envisioned that the replacement of the (arene)chromium(0) moiety in 1 with an isoelectronic and more robust (cyclopentadienyl)manganese(I) moiety might be an answer to this problem. The enantiospecific and scalable synthesis of these (cyclopentadienyl)manganese(I)-based phosphine-olefin ligands 2 has been developed.…”

Section: Introductionmentioning

confidence: 99%

Planar-Chiral Phosphine-Olefin Ligands Exploiting a (Cyclopentadienyl)manganese(I) Scaffold To Achieve High Robustness and High Enantioselectivity

et al. 2017

View full text Add to dashboard Cite

A series of 2-methyl-1,3-propenylene-bridged (η-diarylphosphinocyclopentadienyl)(phosphine)manganese(I) dicarbonyl complexes 2 have been developed as a new class of phosphine-olefin ligands based on a planar-chiral transition-metal scaffold, which show better robustness as well as higher enantioselectivity over phosphine-olefin ligands 1 with a planar-chiral (η-arene)chromium(0) framework. The practical enantiospecific and scalable synthesis of 2 has been established. Phosphine-olefin ligands 2 enable construction of an effective chiral environment around a transition-metal center upon coordination, and thus their rhodium(I) complexes exhibit excellent catalytic performance in the various asymmetric addition reactions of arylboron nucleophiles. Complex 2b, which has a bis(3,5-dimethylphenyl)phosphino group on the cyclopentadienyl ring, is found to be a superior chiral ligand in the rhodium-catalyzed asymmetric 1,4-addition reactions of arylboronic acids to various cyclic/acyclic enones giving the corresponding arylation products in over 99% ee. On the other hand, 2c and 2d, which have bis[3,5-bis(trifluoromethyl)phenyl]phosphino and bis(3,5-di-tert-buthyl-4-methoxyphenyl)phosphino groups, respectively, are highly efficient chiral ligands in the rhodium-catalyzed asymmetric 1,2-addition reactions of the arylboron nucleophiles to imines or aldehydes showing up to 99.9% ee. The X-ray crystallographic studies of (R)-2b and [RhCl((S*)-2b)] reveal the absolute configuration of 2b and its phosphine-olefin bidentate coordination to a rhodium(I) cation. Structural comparison with [RhCl((R*)-1b)] postulates the origins of the higher enantioselectivity of newly developed phosphine-olefin ligands 2.

show abstract

Section: Introductionmentioning

confidence: 99%

Planar-Chiral Phosphine-Olefin Ligands Exploiting a (Cyclopentadienyl)manganese(I) Scaffold To Achieve High Robustness and High Enantioselectivity

et al. 2017

View full text Add to dashboard Cite

show abstract

“…In these cases, readily accessible aryl- or vinylcarbene chromium complexes serve as starting materials for the [3 + 2 + 1]-benzannulation reaction with alkynes, providing a straightforward approach to densely functionalized benzenoids and fused arenes regioselectively labeled with a Cr(CO) 3 fragment. These arene−Cr(CO) 3 complexes are interesting reagents for haptotropic metal migration experiments or for asymmetric syntheses due to their planar chirality .…”

Section: Introductionmentioning

confidence: 99%

Mass Spectrometric Detection and Fragmentation Patterns of Synthetically Useful Chromium and Tungsten Carbene Complexes

et al. 2005

View full text Add to dashboard Cite

A novel method for the detection of synthetically useful pentacarbonyl chromium and tungsten carbene complexes by electrospray ionization Fourier transform ion cyclotron resonance (ESI-FTICR) mass spectrometry is presented which utilizes the addition of CNanions to the electrophilic carbene carbon. This method is nondestructive, provided the ionization proceeds under soft conditions. The scope and limitations of this method are examined by utilizing different types of carbene complexes. Depending on the R-CH acidity of the carbene complexes, [M -H]anions can be observed either in competition with the CNadducts or as the only ions, even in the presence of cyanide. Secondary aminocarbene complexes exclusively form [M -H]anions by deprotonation of the NH moiety. The ions under study have been mass-selected and subjected to collision-induced decay (CID) experiments in order to examine their fragmentation reactions. CO loss is not the only observable process. Most prominently, 1,2-eliminations and a retro-aldol reaction within a sugar carbene complex compete with decarbonylation and thus have rather low activation barriers. Some reactions can be attributed to coordinatively unsaturated chromium atoms formed through preceding CO losses.

show abstract