Alexandre Rodrigue-Witchel

Publications (4)13.04 Total impact

• Article: Synthesis and structure of a dinuclear gold(II) complex with terminal fluoride ligands.

  Doris Y Melgarejo, Gina M Chiarella, John P Fackler, Lisa M Perez, Alexandre Rodrigue-Witchel, Christian Reber
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  ABSTRACT: The potential for reductive elimination of fluorine from dinuclear gold(II) for catalysis has prompted our efforts to synthesize a dinuclear gold(II) fluoride complex. This has been achieved with bis(2,6-dimethylphenyl)formamidinate bridging ligands. In order to obtain this product, it was necessary first to synthesize the corresponding dinuclear gold(II) nitrate, which reacts readily with KF in a metathesis reaction. The nitrate complex and fluoride complexes have been structurally characterized. The Au-Au distance in the dinuclear fluoride, 2.595 Å, is longer than the distance found in the analogous chloride complex, 2.567 Å. This result is consistent with the presence of a fluoride "π electron effect" on the filled Au 5d orbitals. The Raman spectrum shows an Au-Au stretch at 206 cm(-1), which agrees with Woodruff's rules and the density functional theory computational model used for modeling the complex.
  Inorganic Chemistry 05/2011; 50(10):4238-40. · 4.60 Impact Factor
• Article: Intramolecular pi-stacking in copper(I) diketiminate phenanthroline complexes.

  Paul O Oguadinma, Alexandre Rodrigue-Witchel, Christian Reber, Frank Schaper
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  ABSTRACT: Diketimines N,N'-dibenzyl-2-amino-4-imino-pent-2-ene (1), S,S-N,N'-di(phenylethyl)-2-amino-4-imino-pent-2-ene (2), N,N'-bis(3,4,5-trimethoxyphenylmethyl)-2-amino-4-imino-pent-2-ene (3), N,N'-bis(pentafluorophenylmethyl)-2-amino-4-imino-pent-2-ene (4) and N,N'-diisobutyl-2-amino-4-imino-pent-2-ene (5) react with CuOtBu in the presence of 2,9-R2-1,10-phenanthroline to give the respective neutral, tetracoordinated diketiminate copper(I) phenanthroline complexes 1a+2a (R = H), 1b, 3b-5b (R = Me) and 1c+3c (R = Ph). Crystal structures were obtained for all complexes except 5b and intramolecular π-stacking between the phenanthroline ligand and one or two N-benzyl substituents were observed in 1a, 2a, 1b and 1c, or 3b and 4b, respectively. UV/vis absorption spectra show two transitions in the visible region, a diketiminate-based transition at 373-386 nm and a transition at 600-666 nm, tentatively assigned as an MLCT to phenanthroline. All complexes were weakly luminescent in the solid state at room temperature with lifetimes of less than 60 ns. Weak luminescence was also observed in solution with lambdamax = 720-830 nm for 1b, 1c, 3b, 4b and 5b and short luminescence lifetimes. Intramolecular pi-stacking interactions, which prevent flattening distortions in the solid state, appear to have advantageous effects on luminescence intensities.
  Dalton Transactions 10/2010; 39(37):8759-68. · 3.84 Impact Factor
• Article: Interaction of SbCl52− and Thioether Groups at the Open Coordination Sites of Platinum(II) Diimine Complexes

  Sayandev Chatterjee, Jeanette A. Krause, William B. Connick, Caroline Genre, Alexandre Rodrigue-Witchel, Christian Reber
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  ABSTRACT: In the solid-state, the approximately square planar cation in orange crystals of [Pt(NO2phen)(ttcn)](PF6)2 (NO2phen = 5-nitro-1,10-phenanthroline; ttcn = 1,4,7-trithiacyclononane) has a short apical Pt···S(ttcn) distance (2.9415(15) Å). In acetonitrile solution, the electronic spectrum shows a long-wavelength absorption band (412 nm; 2200 M−1 cm−1), consistent with the notion that the axial Pt···S(ttcn) interactions stabilize states having metal-to-ligand charge-transfer (MLCT) character. Reaction with the hexachloroantimonate(V) salt of tris(4-bromophenyl)aminium (TBPA+) results in complex redox chemistry, involving the platinum complex, SbCl52− and TBPA+. In the case of Pt(bpy)(ttcn)2+, orange-yellow crystals of [Pt(bpy)(ttcn)]2(Sb4Cl16) were isolated from the reaction, whereas the reaction with Pt(NO2phen)(ttcn)2+ consistently yielded red crystals of [Pt(NO2phen)(ttcn)](SbCl5)·2CH3CN. In the latter case, the geometry of the cation, including the apical Pt···S(ttcn) distance (2.9390(12) Å), is very similar to that of the PF6− salt. However, the basal plane of each square pyramidal SbCl52− opposes the nearly parallel coordination plane of an adjacent Pt(NO2phen)(ttcn)2+ complex, resulting in an unusually short intermolecular Pt···Sb distance of 3.4259(3) Å. The longest wavelength maximum in the diffuse reflectance spectrum and the solid-state emission maximum are shifted by 1200 cm−1 and 700 cm−1, respectively, to the red of those of the PF6− salt, consistent with perturbation of the complex’s electronic structure because of the Pt···Sb interaction.
  02/2010;
• Article: Interaction of SbCl5(2-) and thioether groups at the open coordination sites of platinum(II) diimine complexes.

  Sayandev Chatterjee, Jeanette A Krause, William B Connick, Caroline Genre, Alexandre Rodrigue-Witchel, Christian Reber
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  ABSTRACT: In the solid-state, the approximately square planar cation in orange crystals of [Pt(NO(2)phen)(ttcn)](PF(6))(2) (NO(2)phen = 5-nitro-1,10-phenanthroline; ttcn = 1,4,7-trithiacyclononane) has a short apical Pt...S(ttcn) distance (2.9415(15) A). In acetonitrile solution, the electronic spectrum shows a long-wavelength absorption band (412 nm; 2200 M(-1) cm(-1)), consistent with the notion that the axial Pt...S(ttcn) interactions stabilize states having metal-to-ligand charge-transfer (MLCT) character. Reaction with the hexachloroantimonate(V) salt of tris(4-bromophenyl)aminium (TBPA(+)) results in complex redox chemistry, involving the platinum complex, SbCl(5)(2-) and TBPA(+). In the case of Pt(bpy)(ttcn)(2+), orange-yellow crystals of [Pt(bpy)(ttcn)](2)(Sb(4)Cl(16)) were isolated from the reaction, whereas the reaction with Pt(NO(2)phen)(ttcn)(2+) consistently yielded red crystals of [Pt(NO(2)phen)(ttcn)](SbCl(5)) x 2 CH(3)CN. In the latter case, the geometry of the cation, including the apical Pt...S(ttcn) distance (2.9390(12) A), is very similar to that of the PF(6)(-) salt. However, the basal plane of each square pyramidal SbCl(5)(2-) opposes the nearly parallel coordination plane of an adjacent Pt(NO(2)phen)(ttcn)(2+) complex, resulting in an unusually short intermolecular Pt...Sb distance of 3.4259(3) A. The longest wavelength maximum in the diffuse reflectance spectrum and the solid-state emission maximum are shifted by approximately 1200 cm(-1) and approximately 700 cm(-1), respectively, to the red of those of the PF(6)(-) salt, consistent with perturbation of the complex's electronic structure because of the Pt...Sb interaction.
  Inorganic Chemistry 02/2010; 49(6):2808-15. · 4.60 Impact Factor