Chiral Ir(I) and Ir(III) complexes [Ir{(R)-binap} (1,2-diamine)]Cl and trans-[Ir(H)(2){(R)-binap} (1,2-diamine)]Cl: synthesis and catalytic applications
Dahlenburg, L; Kramer, D; Heinemann, FW
The P-2,N-2-coordinated iridium(I) chelate complexes [Ir{(R)-binap}(1,2-diamine)]Cl, where (R)-binap = (R)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl and 1,2-diamine = H2NCMe2 CMe2NH2 (tmen) (1), (1R,2R)-H2NCH(Ph)CH(Ph)NH2 [(R,R)-dpen] (2), or cyclo-(1R,2R)-1,2-(H2N)(2)C6H10 [(R,R)-dach] (3), were formed by treating [{(R)-binap}(2)Ir-2(mu-Cl)(2)] with the respective N,N ligand in inert solvents at ambient conditions. They reacted with methanol in benzene or toluene at reflux producing dihydridoiridium(III) complexes, trans-[Ir(H)(2){(R)-binap}(1,2-diamine)]Cl [1,2-diamine tmen (4), (R,R)-dpen (5), or (R,R)-dach (6)]. Compounds 4-6 are base-free (albeit rather slow) catalysts for both the transfer hydrogenation of acetophenone and the hydrogenation of the ketone with molecular hydrogen, giving (S)-1-phenylethanol with moderate enantioselectivities (ee(max) : 74%). A cyclometallated hydridoiridium(III) complex, characterized as (OC-6-54)-[Ir(H)(Cl){(R,R)-binap}{C6H4-2-[(R,R)-CH(NH2)CH(Ph)N=CMe2]-kappa C-1,kappa N-alpha}] (7) by single-crystal X-ray diffraction, was identified as one of the products formed from [{(R)-binap}(2)Ir-2(mu-Cl)(2)] and the (R,R)-dpen ligand in acetone under hydrogen.