Coordination Compounds of Polyoxovanadates with a Hexametalate Core. Chemical and Structural Characterization of [VV6O13{(OCH2)3CR}2]2−, [VV6O11(OH)2{(OCH2)3CR}2], [VIV4VV2O9(OH)4{(OCH2)3CR}2]2−, and [VIV6O7(OH)6{(OCH2)3CR}2]2−

Qin Chen, David P. Goshorn, Charles P. Scholes, Xiao Ling Tan, Jon Zubieta

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Abstract

Reactions of the tris(hydroxymethyl)methane-derived ligands, (HOCH2)3Cr, R = NO2, CH2OH, and CH3, with [(C4H9)4N]3[H3V10O28] in CH3CN yield the polyoxovanadate coordination complexes [(C4H9)4N]2[V6O13{(OCH2)3Cr}2] (R = NO2, 1; CH2OH, 2; CH3, 3). Complexes of this general class are electrochemically active, displaying a reversible one-electron reduction in the range −0.67 to −1.20 V, relative to the ferrocene/ferrocenium couple. The reduced species [VIVVV5O13- {(OCH2)3CNO2}2]3− exhibits an eight-line EPR spectrum at 4.2 K, approximately centered at g = 1.95. Broadening of EPR spectral features as the temperature is raised from 4.2 to 83 K is evidence for increased motion of the unpaired electron consistent with thermally induced electron transfer between VIV and VV states. In contrast, chemical reductions of [(C4H9)4N]2[V6O13{(OCH2)3CCH3}2] with organohydrazines yield the reduced, hydroxy-bridged species [(C4H9)4N]2[VIV4VV2O9(OH)4{(OCH2)3CCH3}2] (6) and [(C4H9)4N]2[VIV6O7(OH)6{(OCH2)3CCH3}2]·2CH2Cl2·0.5C6H5NNC6H5 (7). The protonation sites have been established by X-ray crystallography. Protonation and reduction can be decoupled such that reaction of 3 with HBF4·O(C2H5)2 yields the diprotonated species [V6O11(OH)2{CH3C(CH2O)3}2] (5) wherein the site of protonation has been established by X-ray crystallography as two of the bridging oxo groups. Crystal data are as follows. 1: triclinic P1; a = 11.470 (2) Å, b = 12.149 (2) Å, c = 12.433 (2) Å, α = 63.24 (1)°, β = 63.45 (1)°, γ = 79.31 (1)°, V= 1383.5 (5) Å3, Z = 1, Dcalcd = 1.55 g cm−3; structure solution and refinement (in all cases: Mo Kα, λ = 0.71073 Å) converged at R = 0.049. 2·DMF: monoclinic P21/c, a = 12.003 (2) Å, b = 16.900 (3) Å, c = 16.769 (3) Å, β = 106.95 (1)°, V= 3253.8 (11) Å3, Z = 2, Dcalcd = 1.37 g cm−3; R = 0.054. 3: triclinic P1, a = 11.460 (2) Å, b = 12.237 (2) Å, c = 12.331 (2) Å, α = 62.88 (1)°, β = 63.50 (1)°, γ = 77.52 (1)°, V= 1377.4 (5) Å3, Z = 1, Dcalcd = 1.49 g cm−3; R = 0.055. 5·2DMF·(C2H5)2O: triclinic P1, a = 10.362 (3) Å, b = 10.513 (3) Å, c = 10.366 (2) Å, α= 116.33 (1)°, β = 93.56 (1)°, γ = 62.40 (1)°, V= 882.2 (7) Å3, Z = 1, Dcalcd = 1.83 g cm−3; R = 0.043. 6: triclinic P1, a = 11.534 (2) Å, b = 12.161 (3) Å, c = 12.483 (4) Å, α = 62.86 (2)°, β = 63.15 (2)°, γ = 78.87 (2)°, V= 1389.7 (7) Å3, Z = 1, Dcalcd = 1.48 g cm−3; R = 0.043. 7: triclinic P1, a = 13.613 (3) Å, b = 16.090 (4) Å, c = 16.077 (4) Å, α = 86.36 (1)°, β = 80.71 (2)°, γ = 80.46 (1)°, V = 3424.1 (12) Å3, Z = 2, Dcalcd= 1.45 g cm−3; R = 0.042.

Original languageEnglish (US)
Pages (from-to)4667-4681
Number of pages15
JournalJournal of the American Chemical Society
Volume114
Issue number12
DOIs
StatePublished - Jun 1 1992

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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