A Nonanuclear Copper(II) Polyoxometalate Assembled Around a μ‐1,1,1,3,3,3‐Azido Ligand and Its Parent Tetranuclear Complex

Abstract

Reaction of Cu(II), [gamma-SiW10O36]8-, and N3- affords three azido polyoxotungstate complexes. Two of them have been characterized by single-crystal X-ray diffraction. Complex KNaCs10[{gamma-SiW10O36Cu2(H2O)(N3)2}2].26H2O (1) is obtained as crystals in few hours after addition of CsCl. This linear tetranuclear Cu(II) complex consists in two [gamma-SiW10O36Cu2(H2O)(N3)2]6- units connected through two W=O bridges. When the filtrate is left to stand for one night, a new complex is obtained. From both elemental analysis and IR spectroscopy, it has been postulated that this compound could be formulated K(1.5)Cs(5.5)[SiW10O37Cu2(H2O)2(N3)].14 H2O (1 a), showing the loss of one azido ligand per polyoxometalate unit. Finally, when no cesium salt is added to the reaction medium, the nonanuclear complex K12Na7[{SiW8O31Cu3(OH)(H2O)2(N3)}3(N3)].24 H2O (2) is obtained after three days. Compound 2 crystallizes in the R3c space group and consists in three {Cu3} units related by a C3 axis passing through the exceptional mu-1,1,1,3,3,3-azido bridging ligand. Each trinuclear Cu(II) unit is embedded in the [gamma-SiW8O31]10- ligand, an unprecedented tetravacant polyoxometalate, showing that partial decomposition of the [gamma-SiW10O36]8- precursor occurs with time in such experimental conditions. Magnetically, complex 1 behaves as two isolated {Cu2(mu(1,1)-N3)2} pairs in which the metal centers are strongly ferromagnetically coupled (J = +224 cm(-1), g = 2.20), the coupling through the W=O bridges being negligible. The magnetic behavior of complex 2 has also been studied. Relatively weak ferromagnetic couplings (J1 = +1.0 cm(-1), J2 = +20.0 cm(-1), g=2.17) have been found inside the {Cu3} units, while the intertrimeric magnetic interactions occurring through the hexadentate azido ligand have been found to be antiferromagnetic (J3 = -5.4 cm(-1)) and ferromagnetic (J4 = +1.3 cm(-1)) with respect to the end-to-end and end-on azido-bridged Cu(II) pairs, respectively.

The True Nature of the Di-iron(III) γ-Keggin Structure in Water: Catalytic Aerobic Oxidation and Chemistry of an Unsymmetrical Trimer

“…Since the original synthesis and characterization of [γ-SiW 10 O 36 ] 8- by Tézé and co-workers, this di-defect (“di-lacunary”) polyoxoanion has been used to prepare a variety of 1,2-di-d-metal-substituted derivatives, [γ(1,2)-SiW 10 {M(OH 2 )} 2 O 38 ] n - , complexes with adjacent d-electron centers, including 1 , and other families of POMs. − This growing body of work has largely focused on the synthesis, structures, and occasionally magnetic properties of these complexes. The speciation chemistry in solution including that of the catalytically attractive di-iron derivative, 1 , is lacking.…”

μ1,1-Azide-Bridged Ferromagnetic MnIII Dimer with Slow Relaxation of Magnetization

“…Because of the rich coordination modes and an efficient pathway of magnetic exchange, the azido ligand has attracted considerable interest in the past decade . Complexes with novel magnetic properties have been prepared by using this anion, and their magnetostructural correlations have been extensively studied. , To date, the azido ligand has been found to bridge metal ions in the modes of μ 1,1 -(end-on, EO), μ 1,3 -(end-to-end, EE), μ 1,1,3 , μ 1,1,1 , μ 1,1,1,1 , μ 1,1,3,3 , or unusual μ 1,1,1,3,3,3 fashions . Ferromagnetic interactions are usually transmitted by the EO bridging mode of the azido ligand as are antiferromagnetic interactions by the EE bridging mode …”

Polyoxometalate Immobilized on Graphene via Click Reaction for Simultaneous Dismutation of H2O2 and Oxidation of Sulfur Mustard Simulant

“…Figure d shows the four characteristic peaks of SiW 10 Cu 2 /graphene­(15) that are located at 999, 947, 865, and 788 cm –1 . These peaks correspond to the characteristic stretching vibrations of [γ-SiW 10 O 37 Cu 2 (N 3 ) 2 ] 7– at 999 cm –1 (υ as Si–O a ), 947 (υ as WO d ), 846 cm –1 (υ as W–O–W, interoctahedral), and 781 cm –1 (υ as W–O c –W, intraoctahedral) . Moreover, some shifts are observed for υ as (W–O b –W) and υ as (W–O c –W), which were influenced by the “click” reaction between SiW 10 Cu 2 (N 3 ) 2 and GO–CCH to afford SiW 10 Cu 2 /GO.…”