Synthesis and characterization of an octanuclear nickel(II) polyoxometalate cluster

Abstract

A high-nuclearity nickel-substituted polyoxotungstate, Na₆K_5.5H_4.5 {[Ni₈(OH)₆(H₂O)₂](CO₃)₃(SiW₉O₃₄)₂}·22H₂O (1), has been obtained by the reaction of Na₁₀[α-SiW₉O₃₄]·18H₂O, Ni(NO₃)₂·6H₂O and K₂CO₃ in aqueous solution and characterized by IR spectroscopy, single crystal X-ray diffraction, thermal gravimetric analysis and elemental analysis. Carbonate is not only used to adjust the pH of the solution, but also is a structure-stabilizing agent. The polyoxoanion {[Ni₈(OH)₆(H₂O)₂](CO₃)₃(SiW₉O₃₄)₂}^16- (1a) can be regarded as two {[Ni₄(OH)₃(H₂O)](SiW₉O₃₄)} subunits connected by three carbonate groups, which represents the first polyanion containing an octanuclear nickel cluster based on trivacant Keggin-type polyoxotungstate {XW₉} (X = heteroatom). The subunit {[Ni₄(OH)₃(H₂O)](SiW₉O₃₄)} can be viewed as a tetranuclear nickel cluster linked to a trivacant Keggin-type polyoxotungstate {SiW₉O₃₄}. Furthermore, magnetic measurements show that 1 exhibits antiferromagnetic interactions.

Keywords:

• Silicotungstate
• high-nuclearity
• crystal structure
• magnetism
• polyoxometalate

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

We thank the National Natural Science Foundation of China (Grants 21771054, 21571050, 21573056 and 21771053) and the Natural Science Foundation of Henan Province (Grant 162300410015) for support.