142340-53-2Relevant academic research and scientific papers
Synthesis and catalytic applications of chiral hydridoiridium(III) complexes with diamine/bis(monophosphane) and diamine/diphosphane coordination
Dahlenburg, Lutz,Menzel, Ralf,Heinemann, Frank W.
, p. 4364 - 4374 (2008/03/13)
The P2/N2-coordinated cis-dihydridoiridium(III) chelate complexes (OC-6-13)-[IrH2(H2N∩NH 2)(PR3)2]BF4 [PR3 = PPh3, H2N∩NH2 = 1,2-(H2N) 2C6H4 (1a); (1R,2R)-(H2N) 2C6H10 {(R,R)-dach) (1b); (R)-2,2′- diamino-1,1′-binaphthyl {(R)-dabin} (1c); PR3 = PiPr 3, H2N∩NH2 = (R,R)-dach (2a), (R)-dabin (2b); PR3 = PCy3, H2N∩NH2 = (R)-dabin (3)] were obtained by treating the respective diamine ligands with labile precursors such as [IrH2(OCMe2) 2(PPh3)2]BF4, [(η4-1, 5-C8H12)Ir(PPh3)2]BF4, or [IrH5(PR3)2]/HBF4 (R = iPr, Cy). While oxidative addition of HCl to [(η4-1,5-C8H 12)Ir{(S,S)-bdpcp}]BF4 [(S,S)-bdpcp = (1S,2S)-(Ph 2P)2C5H8] yields the usual mononuclear adduct [(η4-1,5-C8H12)Ir(H)(Cl) {(S,S)-bdpcp}]BF4 (4), similar treatment of [(η4-1,5- C8H12)Ir{(R)-binap}]BF4 furnishes the triply chlorido-bridged diiridium complex [{(Ae)-binap}2Ir 2H2(μ-Cl)3]BF4 (5). Opening of the μ-Cl bridges of 5 by N,N nucleophiles was used to synthesise the three diamine/(R)-binap complexes [Ir(H)(Cl)-(H2N∩NH 2){(R)-binap}]BF4 [H2N∩NH2 = (1R,2R)-H2NCH(Ph)CH(Ph)NH2 {(R,R)-dpen} (6a), (R,R)-dach (6b), and H2NCMe2CMe2NH2 {tmen} (6c). Whereas the dihydrides [IrH2{(R,R)-dach)(PR3) 2]BF4 and [IrH2{(R)-dabin}-(PR 3)2]BF4 (R = iPr, Ph) are only poor (pre)catalysts for the enantioselective hydrogenation of acetophenone, complexes 6a-c catalyze the formation of 1-phenylethanol in good enantiomeric excess [eemax = 82-84 % (S)] in the presence of base. The crystal structures of 1a, 4, and 5 have been determined. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
Oxidative addition of dihydrogen to [Ir(bisphosphine)(1,5- cyclooctadiene)]BF4 complexes: Kinetic and thermodynamic selectivity
Kimmich, Barbara F. M.,Somsook, Ekasith,Landis, Clark R.
, p. 10115 - 10125 (2007/10/03)
The activation of dihydrogen by cationic diphosphine complexes of Rh is the rate-determining and enantiodetermining step in the catalytic asymmetric hydrogenation of prochiral enamides. The addition of H2 to [Ir(bisphosphine)(COD)]+ (COD = 1,5-cyclooctadiene) complexes is examined herein as a model for stereocontrol and dynamic processes related to catalytic hydrogenation. The diastereoselectivity of H2 oxidative addition to form diastereomeric [Ir(chiral bisphosphine)(H)2(COD)]+ complexes at - 80 °C is kinetically controlled and varies substantially with the structure of the diphosphine. In one instance (chiral bisphosphine = CHIRAPHOS), the kinetic and thermodynamic selectivities of H2 addition are inverted; i.e., the dominant kinetic product is thermodynamically less stable than the minor kinetic product. For the [IrH2(Me-DuPhos)- (COD)]+ system, quantitative analysis of the 2D NOE data using two-dimensional conformer population analysis (2DCPA) establishes the absolute stereochemistry and the three- dimensional structures of the predominant conformers. Kinetic analysis of the interconversion of the [IrH2(MeDuPhos)(COD)]+ diastereomers, and of their exchange with D2, reveals a complex pathway for isotope scrambling and diastereomer interconversion that does not involve reductive elimination of H2 to form [Ir(Me-DuPhos)(COD)]+. During the isotope scrambling, exquisite selectivity is seen for exchange in only two ligand sites, one on the Me- DUPHOS ligand and one on the COD ligand.
