Synthesis of Metforminium(2+) Decavanadates – Crystal Structures and Solid‐State Characterization

Three new compounds were formed between decavanadate and diprotonated metformin (H 2 Metf) at different pH values and in the presence or absence of ammonium cations, namely, [H 2 Metf] 3 [V 10 O 28 ] · 8H 2 O ( 1 ), [H 2 Metf] 2 [NH 4 ] 2 [V 10 O 28 ] · 10H 2 O ( 2 ), and [H 2 Metf] 2 [NH 4 ] 2 [V 10 O 28 ] · 4H 2 O ( 3 ). We present their spectroscopic, thermal, and single‐crystal X‐ray diffraction characterization. The solid‐state structure of 1 shows that the three H 2 Metf 2+ dications that counterbalance the charge of the decavanadate anion are in the close vicinity of the latter, as a result of the strong Coulombic forces that arise from the ionic charges. The replacement of one metforminium(2+) cation by two ammonium cations results in two hydrates 2 and 3 , which differ only in their water content. Although 2 and 3 crystallize in the same centrosymmetric space group as 1 , a remarkable difference for 2 and 3 is that the [V 10 O 28 ] 6– anion is placed on an inversion center, which is not the case for 1 .