Synthesis and Chemical Characterization of Complexes Containing Semiquinone Units Bridged by Pentaoxodimolybdate Groups: Structural and Electrochemical Studies of [(n-C4H9)4N]2[Mo4O10(C6H2O4)2] and [(n-c4h9)4n]3[mo 6O15(C6O6)2] and of an Analogous Tetraoxydibenzofuran Complex, [(n-c4h9)4n]2[mo 4O10(C12H4O5)2], Prepared from Metal-Mediated Radical Coupling of 1,2,4-Trihydroxybenzene Precursors

Shuncheng Liu, Shahid N. Shaikh, Jon Zubieta

Research output: Contribution to journalArticle

36 Scopus citations

Abstract

Reaction of (Bu4N)2[Mo207] with 2,5-dihydroxybenzoquinone in acetonitrile yields (Bu4N)2[Mo4O10(C6H2O4)2] (I), a tetranuclear complex with two [Mo205]2+units bridging two planar (C6H2O4)n-groups, stacked in a parallel staggered orientation. The most significant feature is the short interplanar distance between ligands of 2.67 A, allowing magnetic coupling of the radical anion semiquinoid-type ligands. Reactions of organic solvent soluble polyoxomolybdates with tetrahydroxybenzoquinone and 1,2,4-trihydroxybenzene yield the structurally analogous complexes (Bu4N)3[Mo6O15(C6O6)2] (III) and (Bu4N)2(Mo4O10(C12H4O5)2] (IV). In contrast to I and IV, III is paramagnetic with an EPR spectrum consistent with electron localization in a ligand-centered orbital. The steric constraints introduced with the chlorine substituents of chloranilic acid, C6Cl2O4H2, prevent parallel stacking of the ligands, and the mononuclear complex (Bu4N)[MoO2(C6Cl2O4)(C6Cl2O4H)] (II) is isolated from the reaction of chloranilic acid with (Bu4N)2[Mo2O7]. Crystal data for I: orthorhombic space group Pbca, a = 15.527 (3) A, b = 17.192 (3) A, c = 21.094 (4) A, Z = 4, Dcalc= 1.54 g cm-123; structure solution and refinement based on 1022 reflections (F0> 6<r(F0); Mo Ka radiation X = 0.71073 a in all cases), R = 0.060. Crystal data for II: triclinic PI, a = 10.383 (2) A, b = 13.197 (3) A, c = 14.191 (3) A, a = 88.11 (1)°, (3 = 87.57 (1)°, y = 78,11 (2)°, Z = 2, Di = 1.37 g cm-3; 4239 reflections, R = 0.055. Crystal data for III: monoclinic Plja, a = 27.384 (5) A, b = 10.290 (2) A, c = 29.338 (6) A, 0 = 110.98 (1)°, Z = 4, D^ = 1.62 g cm-3; 6125 reflections, R = 0.053. Crystal data for IV: monoclinic P2x/n, a = 16.789 (3) A, b = 9.395 (2) A, c = 20.832 (3) A, 0 = 112.72 (1)°, Z = 2, D^c = 1.63 g cm'3; 3030 reflections, R = 0.052.

Original languageEnglish (US)
Pages (from-to)723-732
Number of pages10
JournalInorganic Chemistry
Volume28
Issue number4
DOIs
StatePublished - Feb 1 1989
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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