Organoosmium complexes of imidazole-containing chelate acceptor ligands
摘要:
The complexes [(L)Os(eta(6)-Cym)Cl](PF6), Cym = p-cymene and L = bis(1-methylimidazol-2-yl) ketone (bik) or bis(1-methylimidazol-2-yl) glyoxal (big), were obtained and characterized with respect to spectroscopy, crystal structure (big complex) and (spectro)electrochemical behaviour at variable temperatures. DFT calculations confirm the structure of [(big)Os(eta(6)-Cym)Cl](+) with imidazolyl-N-bonded Os-II in a boat-shaped seven-membered chelate ring with small N-Os-N angles (<84 degrees). Reduction of this compound proceeds reversibly to a neutral complex of the alpha-semidione radical anion ligand big; EPR and IR spectroelectrochemistry indicate very little participation from the heavy metal in the spin distribution. The analogous [(bik)Os(eta(6)-Cym)Cl](+) could not be reduced reversibly to the ketyl radical complex but displayed a more reversible oxidation at high potential. (C) 2010 Elsevier B.V. All rights reserved.
observed for the platinum compound. Both the PdII and PtII complexes undergo reversible one-electron reduction in CH2Cl2/ 0.1 M Bu4NPF6; the reduced palladium compound disintegrates above -30 degrees C. Electron paramagnetic resonance (EPR), UV-vis, and IR spectroelectrochemistry studies were employed to study the monoanions. The anionradicalcomplex [cis-PtCl2(big)]*- exhibits a well-resolved EPR spectrum
Bis(1-methylimidazol-2-yl)glyoxal (big) which has hitherto not been used in coordination chemistry crystallizes to form Two perpendicular 1-methylimidazol-2-yl-carbonyl molecular halves. Out of the various possibilities for mono- and bis-chelate coordination the N,N'-alternative with a seven-membered chelate ring is realized in [Cp*Cl(big)Rh](PF6) as evident from crystal structure analysis. The iridium analogue reacts under hydration of big and elimination of HCl to form a complex cation [Cp*(bigOH)Ir](+) which dimerizes in the crystal through hydrogen bonding and contains one five- and one six-membered chelate ring involving the alcoholate-O. Cu(ClO4)(2) and the ligand big yield a complex ion [Cu(big)(2)](2+) with an ESR spectrum that suggests the coordination of the central metal by four N atoms in an approximately planar setting.
Organoosmium complexes of imidazole-containing chelate acceptor ligands
The complexes [(L)Os(eta(6)-Cym)Cl](PF6), Cym = p-cymene and L = bis(1-methylimidazol-2-yl) ketone (bik) or bis(1-methylimidazol-2-yl) glyoxal (big), were obtained and characterized with respect to spectroscopy, crystal structure (big complex) and (spectro)electrochemical behaviour at variable temperatures. DFT calculations confirm the structure of [(big)Os(eta(6)-Cym)Cl](+) with imidazolyl-N-bonded Os-II in a boat-shaped seven-membered chelate ring with small N-Os-N angles (<84 degrees). Reduction of this compound proceeds reversibly to a neutral complex of the alpha-semidione radical anion ligand big; EPR and IR spectroelectrochemistry indicate very little participation from the heavy metal in the spin distribution. The analogous [(bik)Os(eta(6)-Cym)Cl](+) could not be reduced reversibly to the ketyl radical complex but displayed a more reversible oxidation at high potential. (C) 2010 Elsevier B.V. All rights reserved.
Knoedler, Axel; Wanner, Matthias; Fiedler, Jan, Journal of the Chemical Society, Dalton Transactions, 2002, # 15, p. 3079 - 3084
作者:Knoedler, Axel、Wanner, Matthias、Fiedler, Jan、Kaim, Wolfgang