Probing the Reactivity of the Ce=O Multiple Bond in a Cerium(IV) Oxo Complex

Yat-Ming So, Yang Li, Ka-Chun Au-Yeung, Guo-Cang Wang, Kang-Long Wong, Herman H. Y. Sung, Ian D. Williams, Zhenyang Lin, Wa-Hung Leung, Polly Arnold

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Abstract

The reactivity of the cerium(IV) oxo complex [(L-OEt)(2)Ce-IV(=O)(H2O)].MeC(O)NH2 (1; L-OEt(-) = [CoCp{P(O)(OEt)(2)}(3)] (-), where Cp = eta(5)-C5H5) toward electrophiles and Bronsted acids has been investigated. The treatment of 1 with acetic anhydride afforded the diacetate complex [Ce-IV(L-OEt)(2)(O2CMe)(2)] (2). The reaction of 1 with B(C6F5)(3) yielded [Ce-IV(L-OEt)(2)(Me2CONH2)(2)][B(C6F5)(3)(OH)](2) (3), in which the [B-(C6F5)(3)(OH)](-) anions are H-bonded to the O-bound acetamide ligands. The treatment of 1 with HCl and HNO3 afforded [Ce-IV(L-OEt)(2)Cl-2] and [Ce-IV(L-OEt)(2)(NO3)(2)], respectively. Protonation of 1 with triflic acid (HOTf) gave the diaqua complex [Ce-IV(L-OEt)(2)(H2O)(2)](OTf)(2) (4), in which the triflate anions are H-bonded to the two aqua ligands. The treatment of 1 with phenol afforded the phenoxide complex [Ce-IV(L-OEt)2(OPh)(2)] (5). The oxo-bridged bimetallic complex [(L-OEt)(2)(Me2CONH2)Ce-IV(O)NaLOEt] (6) with the Ce-O-oxo and Na-O-oxo distances of 1.953(4) and 2.341(4) angstrom, respectively, was obtained from the reaction of 1 with [NaLOEt]. Density functional theory calculations showed that the model complex [(L-OMe)(2)Ce-IV(Me2CONH2)(O)NaLOMe] (6A; L-OMe(-) = [CoCp{P(O)(OMe)(2)}(3)](-)) contains a polarized Ce=O multiple bond. The energy for dissociation of the {NaLOMe} fragment from 6A in acetonitrile was calculated to be +33.7 kcal/mol, which is higher than that for dissociation of the H-bonded acetamide from [(L-OMe)(2)Ce-IV(=O)(H2O)].MeC(O)NH2 (1A) (calculated to be +17.4 kcal/mol). In hexanes containing trace water, complex 1 decomposed readily to a mixture of a tetranuclear cerium(IV) oxo cluster, [Ce-4(IV)(L-OEt)4(mu(4)-O)(mu(2)-O)(4)(mu(2)-OH)(2)] (7), and a cerium(III) complex, [Ce-III(L-OEt)(2)(H2O)(2)][L-OEt] [8(L-OEt)], whereas the cerium/sodium oxo complex 6 is stable under the same conditions. The crystal structures of 3, 4.H2O, 6, and 8(L-OEt) have been determined.

Original languageEnglish
Pages (from-to)10003-10012
Number of pages10
JournalInorganic Chemistry
Volume55
Issue number20
Early online date19 May 2016
DOIs
Publication statusPublished - 17 Oct 2016

Keywords

  • TERMINAL IMIDO COMPLEX
  • C-H ACTIVATION
  • ENERGY-ADJUSTED PSEUDOPOTENTIALS
  • TRANSITION-METAL-COMPLEXES
  • AB-INITIO PSEUDOPOTENTIALS
  • POTENTIAL BASIS-SETS
  • URANIUM NITRIDE
  • LEWIS-ACID
  • ORGANOMETALLIC CHEMISTRY
  • COORDINATION CHEMISTRY

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