The anion of P-dicyclohexylphosphaguanidine, Cy2PC{NiPr}{NHiPr}, forms a P,N-chelate at lithium and cobalt(II); bridging through the Nimine atom forms cyclic hexamers in the former complex.
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http://dx.doi.org/10.1039/b601235c | DOI Listing |
ACS Omega
September 2023
Key Laboratory for Advanced Materials and Institute of Fine Chemicals, School of Chemistry & Molecular Engineering, East China University of Science and Technology, 130 Mei Long Road, Shanghai 200237, China.
A new class of highly active ethylene tri-/tetramerization chromium catalysts supported by iminophosphine ligands has been studied. The impact of electronic and steric changes of these ligands on selectivity and activity has been investigated by varying - and/or -substituents. Upon activation with MMAO, the ligand bearing a -cyclohexyl group displayed a high activity of 307 kg/(g Cr/h) with a high trimerization selectivity of 92.
View Article and Find Full Text PDFChem Sci
April 2018
Department of Chemistry , Faculty of Science , Hokkaido University, Sapporo 060-0810 , Japan . Email:
Copper-catalyzed asymmetric direct alkynylation of α-ketoesters with terminal alkynes with chiral prolinol-phosphine ligands, most preferably (α,2)-1-(2-dicyclohexylphosphinobenzyl)-α-neopentyl-2-pyrrolidinemethanol, afforded various enantioenriched chiral propargylic tertiary alcohols. Quantum-chemical calculations using the BP86 density functional including Grimme's empirical dispersion correction [DF-BP86-D3(BJ)-PCM(BuOH)/TZVPP//DF-BP86-D3(BJ)/SVP] show the occurrence of OH···O/sp-CH···O two-point hydrogen bonding between the chiral ligand and the carbonyl group of the ketoester in the stereo-determining transition states. Combined with the hydrogen-bonding interactions orienting the ketoester substrate, dispersive attractions between the chiral ligand (-cyclohexyl groups) and the ketoester in the favored transition states, rather than steric repulsions in the disfavored transition state explain the enantioselectivity of the asymmetric copper catalysis.
View Article and Find Full Text PDFDalton Trans
May 2006
Department of Chemistry, University of Sussex, Falmer, Brighton, UK BN1 9QJ.
The anion of P-dicyclohexylphosphaguanidine, Cy2PC{NiPr}{NHiPr}, forms a P,N-chelate at lithium and cobalt(II); bridging through the Nimine atom forms cyclic hexamers in the former complex.
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