Synthesis and Catalytic Applications of Chiral Hydridoiridium(III) Complexes with Diamine/Bis(monophosphane) and Diamine/Diphosphane Coordination

摘要

The P2/N2-coordinated cis-dihydridoiridium(III) chelate complexes (OC-6-13)-[IrH2(H2N intersect NH2)(PR_3)_2]BF_4 [PR_3 = PPh_3, H2N intersect NH2 = 1,2-(H2N)_2C6H4 (1a); (1R,2R)-(H2N)_2C6H_(10) {(R,R)-dach} (1b); (R)-2,2'-diamino-1,1'-binaphthyl {(R)-dabin} (1c); PR_3 = PiPr_3, H2N intersect NH2 = (R,R)-dach (2a), (R)-dabin (2b); PR_3 = PCy_3, H2N intersect NH2 = (R)-dabin (3)] were obtained by treating the respective diamine ligands with labile precursors such as [IrH2(OCMe2)_2(PPh_3)_2]BF_4, [(eta~4-1,5-C8H_(12))Ir(PPh_3)_2]BF_4, or [IrH5(PR_3)_2]/HBF_4 (R = iPr, Cy). While oxidative addition of HCl to [(eta~4-1,5-C8H_(12))Ir{(S,S)-bdpcp}]BF_4 [(S,S)-bdpcp = (1S,2S)-(Ph_2P)_2C5H8] yields the usual mononuclear adduct [(eta~4-1,5-C8H12)Ir(H)(Cl){(S,S)-bdpcp}]BF_4 (4), similar treatment of [(eta~4-1,5-C8H_(12))Ir{(R)-binap}]BF_4 furnishes the triply chlorido-bridged diiridiumcomplex [{(R)-binap}_2Ir2H2(mu-Cl)_3]BF_4 (5). Opening of the mu-Cl bridges of 5 by N,N nucleophiles was used to synthesise the three diamine/(R)-binap complexes [Ir(H)(Cl)-(H2N intersect NH2){(R)-binapJ]BF_4 [H2N intersect NH2 = (1R,2R)-H2NCH(Ph)CH(Ph)NH2 {(R,R)-dpen} (6a), (R,R)-dach (6b), and H2NCMe2CMe2NH2 {tmen} (6c). Whereas the dihy-drides [IrH2{(R,R)-dach)(PR3)_2]BF_4 and [IrH2{(R)-dabin}-(PR_3)_2]BF_4 (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 [ee_(max) = 82-84% (S)] in the presence of base. The crystal structures of 1a, 4, and 5 have been determined.