50777-69-0Relevant articles and documents
Enantioselective supramolecular catalysis induced by remote chiral diols
Van Leeuwen, Piet W. N. M.,Rivillo, David,Raynal, Matthieu,Freixa, Zoraida
, p. 18562 - 18565 (2012/01/31)
A new method of creating libraries of chiral diphosphines is presented. Supramolecular coordination compounds based on Ti, Rh, achiral ditopic ligands, and chiral diols were synthesized by in situ mixing and used as catalysts in the asymmetric hydrogenation of (Z)-methyl 2-acetamido-3-phenylacrylate, giving ee's of up to 92%. The ditopic ligands contain a Schiff base that coordinates to the assembly metal Ti and a phosphine as a ligand for Rh. Chirality is introduced by coordination of the chiral diols to Ti. The controlling chiral center and the substrate are separated by as much as 13 A.
Catalysis by design: Wide-bite-angle diphosphines by assembly of ditopic ligands for selective rhodium-catalyzed hydroformylation
Rivillo, David,Gulyas, Henrik,Benet-Buchholz, Jordi,Escudero-Adan, Eduardo C.,Freixa, Zoraida,Van Leeuwen, Piet W. N. M.
, p. 7247 - 7250 (2008/09/17)
The assembly makes the bite! Ditopic ligands comprising an anionic N-O or N-N moiety (shown in blue and gray) and a phosphine moiety (orange) can be assembled with hard metals such as zinc(II) (green) to form bidentate phosphine ligands. This approach led to a rhodium catalysts for the selective hydroformylation of 1-octene with linear-to-branched ratios up to 21:1 and rates comparable to covalently bound wide-bite-angle diphosphine ligands. (Figure Presented).
Towards co-operative reactivity in conjoint classical-organometallic heterometallic complexes: The co-ordination chemistry of novel ligands with triphenylphosphine and bis(pyridylethyl)amine or triazacyclononane domains
Watkins, Scott E.,Craig, Donald C.,Colbran, Stephen B.
, p. 2423 - 2436 (2007/10/03)
With a view towards later studies of co-operativity in heteronuclear complexes with hard classical (oxygen-activating) and soft organometallic (organic-substrate binding) metal centres, four novel ditopic N3P-donor ligands (L1-L4), each comprising triphenylphosphine tethered to an N,N′-bis(2-pyridyl-2-ethyl)amine (bpea) or a 1,4-diisopropyl-1,4,7-triazacyclononane (tacn*) N3-donor group, have been designed and prepared by reductive aminations of ortho- and meta-(diphenylphosphino)benzaldehydes with bpea (for L1 and L3) and tacn* (for L2 and L4). A range of κNn, κP-chelate mononuclear complexes have been isolated from the reactions of the ortho-substituted ligands, L1 and L2, with Cu(I), Zn(II) and Pt(II) sources, and the X-ray crystal structures of [Cu(L1)][PF6], [Cu(L2)][PF6] (communicated in: S. E. Watkins, D. C. Craig and S. B. Colbran, J. Chem. Soc., Dalton Trans., 1999, 1539) and [PtCl(L1)][PF6] have been determined. Six complexes with the phosphine of L1-L4 co-ordinated to a softer [Pt(II), Ir(I) or W(O)] metal centre and with dangling, metal-free N3-donor domains have been prepared: for the ortho-substituted ligands L1 and L2, it was necessary to protect the hard, more basic N3-donor domains by protonation (pH control) to prevent formation of κNn, κP-chelate mononuclear complexes; for the meta-substituted ligands L3 and L4, pH control was unnecessary as the phosphine group selectively binds to the softer metal ions. The complex trans-[IrCl(CO)(L3)2] reversibly forms a dioxygen adduct. An Ir(III)Cu(II)2 and four Pt(II)Cu(II)2 heterometallic complexes were prepared by adding hard Cu(II) ions to the Ir(I) and Pt(II) complexes with metal-free N3-donor domains, and the full characterisation of these is described. The tungsten(O) carbonyl complex [W(CO)5(L3)], with a metal-free N3-bpea domain, was prepared for a study of metal ion recognition. No perturbation of the carbonyl region of the IR spectrum was observed when metal ions were added. The effect of submolar quantities of heterometallic complexes, obtained by adding a first d-series metal(II) ion (2 equivalents) to [IrCl(CO)(L3)2], on the oxidation of styrene by oxygen in methylethyl ketone has been assayed: inhibition of the oxidation is observed with the %conversion and the product selectivity dependant on the metal(II) ion.
