Incorporation of Substitutionally Labile [V^III(CN)₆]³⁻ into Prussian Blue Type Magnetic Materials

A Prussian blue (PB) type material containing hexacyanovanadate(III), Mn^II_1.5[V^III(CN)₆]·0.30MeCN (1), was formed from the reaction of [V^III(CN)₆]³⁻ with [Mn(NCMe)₆]²⁺ in MeCN. This new material exhibits ferrimagnetic spin- or cluster-glass behavior below a T_c of 12 K with observed magnetic hysteresis at 2 K (H_cr = 65 Oe and M_rem = 730 emu·Oe/mol). Reactions of [V^III(CN)₆]³⁻ with [M^II(NCMe)₆]²⁺ (M = Fe, Co, Ni) in MeCN lead to either partial (M = Co) or complete (M = Fe, Ni) linkage isomerization, resulting in compounds of Fe^II_0.5V^III[Fe^II(CN)₆]·0.85MeCN (2), (NEt₄)_0.10Co^II_1.5−aV^II_a[Co^III(CN)₆]_a[V^III(CN)₆]_1−a(BF₄)_0.10·0.35MeCN (3), and (NEt₄)_0.20V^III[Ni^II(CN)₄]_1.6·0.10MeCN (4) compositions. Compounds 2–4 do not magnetically order as a consequence of diamagnetic cyanometalate anions being present, i.e., [Fe^II(CN)₆]⁴⁻, [Co^III(CN)₆]³⁻, and [Ni^II(CN)₄]²⁻. Incorporation of [V^III(CN)₆]³⁻ into PB-type materials is synthetically challenging because of the lability of the cyanovanadate(III) anion.