P‐Modular Homochiral Bis(phosphanes) with 1,2‐Disubstituted Cyclopentane Backbones in Asymmetric Hydrogenation

Abstract

The review surveys synthetic aspects of a class of bidentate phosphanes based on the trans-1,2-disubstituted cyclopentane framework and the application of such ligands in transition-metal-catalyzed enantioselective hydrogenation. In particular, we address the preparative potential of the isomerically pure multi-purpose P−H and P−Cl reagents (R,R)-and (S,S)-C 5 H 8 (PX 2 ) 2 (X = H, Cl), which can serve to construct a family of optically active bis(phosphanes) with structural components (''modules'') that are easily and systematically interchanged. The so-designed chelate ligands

A Tetraphosphane Imine Ligand Which Enforces Square‐Pyramidal Coordination

“…When Co(BF 4 ) 2 ·6H 2 O is used, the corresponding tetrafluoroborate salt 5 is formed (52 %). (3) Both compounds are soluble in CH 2 Cl 2 and sparingly soluble in methanol and THF. They are paramagnetic 17-valence-electron complexes of square-pyramidal coordinated cobalt(), with the parent ion as the base peak in the mass spectra (m/z = 986, [(py{PPh 2 } 4 )Co] + , 100 %).…”

“…[1,2] The vast majority of applications in homogeneous catalysis requires bidentate ligands (e.g., in asymmetric hydrogenation). [3] Owing to the necessity for "labile" donors and/or vacant coordination sites in molecular catalysts, ligands of higher denticity such as tridentate H 3 CC(CH 2 PPh 2 ) 3 , "triphos", or tetradentate P(CH 2 CH 2 PPh 2 ) 3 , "pp3", are less prone to give catalytically active species, although specialised applications in the "heterogenisation" of homogeneous catalysts do make use of the increased thermal and kinetic complex stability that such ligands impart. [4] Complexes of polypodal phosphane ligands show a rich coordination and reaction chemistry in their own right, however.…”

Mechanistic Insights into Transfer Hydrogenation Catalysis by [Ir(cod)(NHC)2]+Complexes with Functionalized N-Heterocyclic Carbene Ligands

“…Late-transition-metal-catalyzed transfer hydrogenation of unsaturated substrates has been explained through different mechanisms involving both monohydride or dihydride species, according to an inner-sphere mechanism, or concerning the participation of a ligand in the catalytic reaction, according to an outer-sphere metal–ligand bifunctional catalysis mechanism . However, in the case of Ir(I) complexes, the monohydride mechanism seems to be preferred . Mechanistic studies on cationic complexes having a methoxy-functionalized NHC ligand (NHC∩Z, type I; Chart ), in combination with DFT calculations, allowed us to disclose that the interaction of the MeO– fragment of the NHC ligand within an alkoxo intermediates species facilitates the β-H elimination step en route to the key hydrido [IrH(cod)(NHC∩Z)] intermediate species .…”

Phosphines and Related Tervalent Phosphorus Systems

“…Useful general reviews of phosphine chemistry which have appeared in the past two years include coverage of the synthesis and applications of primary phosphines, 285 recent developments in the synthesis of chiral phosphetanes, 286 the synthesis of P-modular homochiral bis(phosphines) having a 1,2-disubstituted cyclopentane backbone 287 and new chiral phosphorus ligands for enantioselective hydrogenation. 288 Reviews of the design of chiral ligands for asymmetric catalysis, covering C 2 -symmetric P,P-ligands to sterically and electronically non-symmetrical P,N-ligands, 289 chiral P,N-ligands involving pyridine and phosphorus donor centres, 290 mixed donor phosphine-phosphine oxide ligands, 291 and combinatorial libraries of chiral ligands 292 have also appeared.…”