Multicomponent Cooperative Assembly of Nanoscale Boron-Rich Polyoxotungstates with 22 and 30 Boron Atoms^a

This work demonstrates that the introduction of positive lanthanide (Ln) and transition metal (TM) cations into polyoxotungstates (POTs) to stabilize negative oxoboron clusters is a feasible and general synthetic strategy for creating not only rare boron-rich POTs but also intriguing multicomponent composite polyoxometalates (POMs). By this strategy, a large family of unprecedented boron-rich POTs with 22 and 30 boron atoms, such as [(B₁₈Si₃Ln₆ O₃₆(OH)₁₄){B₄Ni₄O₁₀(OH)₄(A-α-SiW₉O₃₄)}₃]^44- (1Ln), [(B₁₉Si₂Ln₇O₃₅(OH)₁₅(H₂O)){B₄Ni₄O₁₀(OH)₄ (A-α-SiW₉O₃₄)}₂{B₃Ni₄O₉(OH)₃(A-α-SiW₉-O₃₄)}]^41- (2Ln), where Ln is Gd, Tb, and Dy, and [(B₂₂O₄₂) {LnNi₃(OH)₃(B-α-SiW₉O₃₄)}₄]^34- (3Ln; Ln is Sm, Gd, and Tb), have been obtained. These POTs incorporate the largest number of boron atoms and the highest-nuclearity oxoboron clusters of any molecular POTs reported to date. The results show the fusion of two distinct research areas of POT chemistry and oxoboron cluster chemistry. In addition, they also show a family of unique POMs made from multiple oxo clusters including W-O, B-O, TM-O, and Ln-O. Experiments indicate these novel composite materials can exhibit effective catalytic activity for oxidizing toxic 2-chloroethyl ethyl sulfide.