Jian-Hua Xie

University of Maryland, College Park, Maryland, United States

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Publications (5)22.61 Total impact

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    ABSTRACT: Unprecedented non-interconvertable conformational isomers derived from cyclic amide ligands in a paddlewheel dimetallic framework are reported.
    No preview · Article · Jul 2009 · Chemical Communications
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    Jian-Hua Xie · Michael P. Doyle · Ernest L. Eliel
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    ABSTRACT: A plausible explanation for the unprecedented formation of two conformational isomers of bisphenyldirhodium(III) caprolac- tamate is presented. The presence of acetic acid during the coupling process leading to the formation of bisphenyldirhodium(III) capro- lactamate is shown to increase the propeller conformer at the expense of the biplanar conformer, Acetic acid is also found to catalyze the decomposition of bisphenyldirhodium(III) caprolactamate with the propeller conformation reacting at a rate that is more than ten times greater than that for the biplanar conformation. We speculate that pro- tonation of one of the caprolactamate ligands changes the orientation of the phenyl ring in its approach to rhodium in the product-forming step of the arylation reaction leading to the formation of the two con- formational isomers.
    Full-text · Article · Jul 2009 · Journal of the Mexican Chemical Society
  • Jian-Hua Xie · Lei Zhou · Conrad Lubek · Michael P Doyle
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    ABSTRACT: Fourteen hetero-bis(sigma-aryl)dirhodium(III) caprolactamates that differ by the two aryl groups at the axial positions of dirhodium have been synthesized in good yield and characterized. Copper(II) catalyzed oxidation of dirhodium(II) caprolactamate at room temperature in the presence of two arylboronic acids results in a mixture of a hetero-bis(sigma-aryl)dirhodium(III) caprolactamate and two homo-bis(sigma-aryl)dirhodium(III) caprolactamates for each arylboronic acid combination. The UV-vis lambda(max) values for hetero-bisaryldirhodium(III) caprolactamates fall in between those for the corresponding homo-bisaryldirhodium(III) caprolactamates; electronic interaction between the two aryl groups occurs through dirhodium, but this transmission is probably indirect through the caprolactamate ligands rather than directly between rhodiums. The chemical shift for the carbon bound to Rh shows very limited dependence on the substituent from the aryl group on the adjacent Rh. Bisaryldirhodium(III) caprolactamates with electron-withdrawing substitutions have higher oxidation potentials than those with electron-donating substitutions. A plot of oxidation potentials versus the corresponding UV-visible absorption maxima for the bisaryldirhodium(III) caprolactamates shows a relationship between oxidation potentials and lambda(max) values. The electronic/electrochemical information obtained for hetero-bis(sigma-aryl)dirhodium(III) caprolactamates suggests that communication between aryl substituents occurs.
    No preview · Article · May 2009 · Dalton Transactions
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    ABSTRACT: The unique structural features and chemical stabilities of bis(phenyl) tetracarboxamidatodirhodium(III) are reported, and their electronic structures are mapped through XPS, electrochemical, and computational methods. Comparison with the structures of dirhodium(II,II) and dirhodium(II,III) oxidative precursors portrays the diphenyl dirhodium(III) compounds as two square-pyramidal rhodium units that have undergone conrotatory motion in order to optimize metal-ligand bonding. Axial phenyl ligands are severely distorted from their expected Rh-Rh-C linear array. XPS data for this series of dirhodium compounds are consistent with the absence of a rhodium-rhodium bond for the diphenyl dirhodium(III) compounds, and electrochemical measurement shows a single reversible Rh-2(6+)/Rh-2(7+) redox couple. Notably, they exhibit high thermal stability, and Bronsted acid removal of carboxamidate ligands precedes the formation of benzene. The ability of a phenyl group to impart unusual stability to rhodium(III) compounds is explained by theoretical analysis of the electronic structure of bis-sigma-(pbenyl)-tetrakis-mu-(carboxamido)dirhodium(III), and comparison is made with previously reported dinitrosyl dirhodium(III) complexes. Formally, two phenyl radicals in combination with a rhodium-rhodium bond are transformed into two phenyl-rhodium bonds. The severe distortion of phenyl rings from linearity is suggested to result from a long-range interaction between the electron-deficient rhodium and distal oxygen atoms.
    No preview · Article · Nov 2008 · Organometallics
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    ABSTRACT: Recently discovered stable bis(sigma-phenyl)dirhodium(III) caprolactamate and its substituted derivatives are conveniently prepared in high yields from dirhodium(II) caprolactamate and commercially available arylboronic acids in a copper-catalyzed process.
    No preview · Article · Jul 2008 · Chemical Communications