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Issue 21, 2013
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Axially chiral monomeric and dimeric square planar Pd(II) complexes and their application to chiral tectonics

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Abstract

Mononuclear and dinuclear square planar palladium(II) complexes (denoted by [(hfac)Pd(II)(L-LH)] and [(hfac)Pd(II)(L-L)Pd(II)(hfac)], respectively) were synthesized. Here hfac, HL-L and L-L2− denote hexafluoroacetylacetonato, monoprotonated and non-protonated bis-β-diketonato ligands, respectively. Three bis-β-diketones were used as HL-LH: 1,2-diacetyl-1,2-dibenzoylethane (denoted by dabeH2), 1,2-diacetyl-1,2-bis(3-methylbutanoyl)ethane (baetH2) and 1,2-diacetyl-1,2-propanoylethane (dpeH2). Both the monomeric and dimeric Pd(II) complexes were chiral due to the orthogonal twisting of the two non-symmetric diketonato moieties in HL-L and L-L2−, respectively. Optical resolution of [(hfac)Pd(II)(dabe)Pd(II)(hfac)] was achieved chromatographically on a chiral column to obtain a pair of optical antipodes which were stable against racemization. As for the other complexes, resolution was possible only after replacing hfac with a bulky ligand such as dibenzoylmethanato (dbm). Although a dinuclear complex with a symmetric bis-β-diketonato ligand, [(hfac)Pd(II)(taet)Pd(II)(hfac)] (taet2− = 1,1,2,2-tetraacetylethanato), was achiral, the replacement of the terminal ligands with non-symmetric β-diketonates yielded an axially chiral complex such as [(phacac)Pd(II)(taet)Pd(II)(phacac)], wherein phacac denotes 1-phenyl-1,3-butanedionato. The UV and CD spectra of the Pd(II) complexes were analyzed with the help of the TDDFT calculations. The chiral monomeric species, [(dbm)Pd(II)(R- or S-baetH)], formed a heterometallic tetranuclear complex, [Fe(III){(dbm)Pd(II)(R- or S-baet)}3], in methanol solution.

Graphical abstract: Axially chiral monomeric and dimeric square planar Pd(ii) complexes and their application to chiral tectonics

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Publication details

The article was received on 14 Feb 2013, accepted on 02 Mar 2013 and first published on 27 Mar 2013


Article type: Paper
DOI: 10.1039/C3DT50420D
Citation: Dalton Trans., 2013,42, 7579-7585
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    Axially chiral monomeric and dimeric square planar Pd(II) complexes and their application to chiral tectonics

    H. Sato, K. Morimoto, Y. Mori, Y. Shinagawa, T. Kitazawa and A. Yamagishi, Dalton Trans., 2013, 42, 7579
    DOI: 10.1039/C3DT50420D

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