Derivatized polyoxomolybdates. Synthesis and characterization of oxomolybdate clusters containing coordinatively bound diazenido units. Crystal and molecular structure of the octanuclear oxomolybdate (NHEt3)2(n-Bu4N)2[Mo 8O20(NNPh)6] and comparison to the structures of the parent ...

Tze Chen Hsieh, Shahid N. Shaikh, Jon Zubieta

Research output: Contribution to journalArticle

68 Scopus citations

Abstract

Full title: Derivatized polyoxomolybdates. Synthesis and characterization of oxomolybdate clusters containing coordinatively bound diazenido units. Crystal and molecular structure of the octanuclear oxomolybdate (NHEt3)2(n-Bu4N)2[Mo 8O20(NNPh)6] and comparison to the structures of the parent oxomolybdate α-(n-Bu4N)4[Mo8O26] and the tetranuclear (diazenido)oxomolybdates (n-Bu4N)2[Mo4O10(OMe) 2(NNPh)2] and (n-Bu4N)2[Mo4O8(OMe) 2(NNC6H4NO2)4]. Reactions of α-(n-Bu4N)4[Mo8O26] with phenylhydrazine yield a variety of derivatized polyoxomolybdates containing the cis-bis(diazenido)molybdenum core [Mo(NNPh)2]2+. When the reaction is carried out in methanol with excess (p-nitrophenyl)-hydrazine, (n-Bu4N)2[Mo4O8(OMe) 2(NNAr)4] is the major product. The tetranuclear polyoxomolybdate unit consists of the [Mo2(μ-OMe)2(NNAr)4]2+ core, bridged by two doubly bridging bidentate [MoO4]2- moieties. On the other hand, when the molybdate is present in excess, the unsymmetrically substituted tetranuclear cluster (n-Bu4N)2[Mo4O10(OMe) 2(NNPh)2] is isolated. This species is structurally analogous to [Mo4O8(OMe)2(NNPh)4]2-, presenting the [Mo2O2(μ-OMe)2(NNPh)2] 2+ core, and is characterized by a cis-[MoO2]2+ unit and a single cis-[Mo(NNPh)2]2+ unit, bridged by two methoxy groups. The tetranuclear unit is completed by the doubly bridging [MoO4]2- units. In contrast, reactions of phenylhydrazine and NEt3 with α-(n-Bu4N)4[Mo8O26] in acetonitrile yield the octanuclear polyoxomolybdate (NHEt3)2(n-Bu4N)2[Mo 8O20(NNPh)6]. The structure is related to that of the α-[Mo8O26]4- parent polyoxomolybdate, by substitution of the two terminal oxo groups on each of three alternate molybdenum centers in the Mo6O6 crown and rotation of the pole-capping [MoO4]2- units by ca 45°, so as to engage three doubly bridging Mo2O interactions per unit rather than three triply bridging Mo3O interactions. The 17O NMR spectra of the derivatized species are consistent with the solid-state structures, exhibiting resonances in the regions assigned to doubly bridging Mo2O groups (400-520 ppm) and to terminal MoO groups (700-950 ppm) Crystal data are as follows. α-(n-Bu4N)4[Mo8O26]: monoclinic space group P21/n, with a = 15.093 (3) Å, b = 16.011 (3) Å, c = 18.519(4) Å, β = 91.36 (1)°, V = 4473.9 (3) Å3 and Z = 2. Structure solution based on 3274 reflections converged at R = 0.039. (n-Bu4N)2[Mo4O8-(OMe) 2(NNC6H4-p-NO2)4]: monoclinic space group P21/n, with a = 15.723 (2) Å, b = 14.058 (2) Å, c = 16.607 (3) Å, β = 95.28 (1)°, V = 3655.1 (2) Å3 and Z = 2. Structure solution and refinement based on 2988 reflections converged at R = 0.063. (n-Bu4N)2[Mo4O10(OMe) 2(NNPh)2]: monoclinic space group C2/c, with a = 15.472 (2) Å, b = 20.516 (3) Å, c = 19.077 (2) Å, β = 91.23 (1)° V = 6054.1 (2) and Z = 4. Structure solution and refinement based on 1670 reflections converged at R = 0.066. (NHEt3)2(n-Bu4N)2[Mo 8O20(NNPh)6]: P21/c with a = 18.495 (3) Å, b = 26.783 (5) Å, c = 21.470 (4) Å, β = 95.57 (1)°, V = 10585.0 (9) Å3, and Z = 4; 6525 reflections, R = 0.051.

Original languageEnglish (US)
Pages (from-to)4079-4089
Number of pages11
JournalInorganic Chemistry
Volume26
Issue number24
StatePublished - Dec 1 1987
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

Fingerprint Dive into the research topics of 'Derivatized polyoxomolybdates. Synthesis and characterization of oxomolybdate clusters containing coordinatively bound diazenido units. Crystal and molecular structure of the octanuclear oxomolybdate (NHEt<sub>3</sub>)<sub>2</sub>(n-Bu<sub>4</sub>N)<sub>2</sub>[Mo <sub>8</sub>O<sub>20</sub>(NNPh)<sub>6</sub>] and comparison to the structures of the parent ...'. Together they form a unique fingerprint.

  • Cite this