Non-Template-Centered, Closed Tetravanadium Phosphate and Phosphonate Clusters

Abstract

Tetranuclear V(III) complexes, [HB(pz)(3)](4)V(4)(&mgr;-C(6)H(5)OPO(3))(4) (I), its acetonitrile solvate (I.4CH(3)CN), and [HB(pz)(3)](4)V(4)(&mgr;-O(2)NC(6)H(4)OPO(3))(4).4C(7)H(8).H(2)O (II), and tetranuclear vanadyl complexes, (t-Bupz)(4)V(4)O(4)(&mgr;-C(6)H(5)PO(3))(4).2H(2)O (III) and (t-Bupz)(5)V(4)O(4)(&mgr;-C(6)H(5)PO(3))(4).4CH(3)CN.0.6 H(2)O (IV), have been prepared and characterized by spectroscopic, magnetic, and electrochemical methods (pz = pyrazole, t-Bupz = tert-butylpyrazole). The use of organic solvents and bulky organic groups as ancillary ligands leads to formation of neutral species instead of the anionic clusters commonly found in the hydrothermal synthesis of vanadium organophosphate/phosphonate systems. Complexes I.4CH(3)CN and IV have also been characterized by single-crystal X-ray diffraction. Crystal data: I.4CH(3)CN, triclinic, P&onemacr;, a = 15.495(3) Å, b = 17.000(3) Å, c = 17.949(4) Å, alpha = 89.17(3) degrees, beta = 86.00(3) degrees, gamma = 78.60(3) degrees, Z = 2; IV, triclinic, P&onemacr;, a = 15.541(3) Å, b = 16.340(2) Å, c = 19.069(5) Å, alpha = 83.58(2) degrees, beta = 79.67(2) degrees, gamma = 63.68(1) degrees, Z = 2. Both are closed clusters, the core structure of the first consisting of a cubane-like arrangement of metal octahedra and phosphate tetrahedra and the core structure of the second consisting of a distorted, collapsed variant of the first. Unlike other vanadium phosphate clusters, these compounds form in the absence of a central, templating agent. As such they represent the simplest form of a closed cluster in which steric forces and cluster connectivity requirements play the primary role in organizing the cluster framework.

A journey into the electrochemistry of vanadium compounds

“…The tetranuclear V(III) complex, [HB(pz) 3 ] 4 V 4 (-C 6 H 5 OPO 3 ) 4 [258], was electrochemically investigated in MeCN and in DCM. In acetonitrile two reversible oxidations of the cluster were observed at +0.68 and +1.13 V (vs AgCl/Ag, Bu 4 NPF 6 as supporting electrolyte).…”

Novel mixed-valence vanadium(IV/V) molecule exhibiting unusual electron delocalization over the [V2O3]3+ core

“…There is currently, considerable synthetic interest in the chemistry of vanadium because of its remarkable ability to form a variety of simple mononuclear 1 and polynuclear 2 compounds as well as complex clusters. 3 Besides their scientific significance, many of these complexes are attractive as potential catalysts in biological 4 and industrial 5 processes or their simpler models. Our own involvement in vanadium chemistry reflects a recent interest 6 in the insulin-mimicking ability exhibited by some relatively simple water-soluble vanadyl complexes.…”

Synthesis And Characterization Of A Series Of Vanadium(iv) Complexes With The Kläui Ligand

“…The dissolution process was slow, indicating that the solvent may not be the best choice leading to the failure of the synthesis. The second attempt used acetonitrile as the solvent by employing phenylphosphonic salt, which was reported before by Carrano and his co-workers(64). However, the reaction pathway failed.…”

“…Further interest arises from the small possible cage-like vanadium phosphate clusters that have been observed to form around a variety of template molecules or ions. Carrano and co-workers employed a nitrogen tridentate ligand, hydridotris(pydazolyl)borate, HB(pz)3or Tp -, shown in Figure 8, to synthesize and characterize vanadium clusters (59,(63)(64)(65). Tpligand can serve as a facially coordinating, anionic six-electron donor (66)(67)(68).…”

“…All these vanadium(IV) complexes have a core with a (O=V)(OPO)2(V=O) ring (64,70,(84)(85)(86)89) and varying groups on the aryl moieties attached to the phosphorus atom. According to Carrano and co-workers, there are four unique dimeric components in a hexanuclear vanadium(IV) cluster, H2O⸦[t-Bupz(μ-C6H5OPO3)VO]6(H2O)2-2CH3CH2OH (70), shown in Our group has synthesized series of vanadium-phosph-(on/in)ate dimers with the methyl Kläui ligand (L OMe )and the ethyl Kläui ligand (L OEt ) -.…”