Hydrothermal synthesis and crystal structures of two novel vanadium oxides containing interlamellar transition metal complexes

Two new vanadium oxide compounds, which contain interlamellar transition metal complexes bound to vanadium oxide sheets, were synthesized hydrothermally. The crystal structure of each reveals unusual coordination geometries and interlayer bonding. [Ni(2,2'-bipyridine)]₂[V₁₂O₃₂] (1) was prepared from the reaction of V₂O₅, NiO, H₂O and 2,2'-bipyridyl in the molar ratio 4:8:3312:0.5. The isomorphous compounds [M(2,2'- bipy)]₂[V₁₂O₃₂] (where M is Co (1a) and Cu (1b)) were prepared in a similar fashion. The Ni coordination compound 1 crystallizes as amber needles, and the structure was solved in the space group C2/m (12) with unit cell parameters a=24.344(3) Å, b=6.897(3) Å, c= 12.028(2) Å, β=93.60(2)°(R(Rw)=0.039(0.038)). This compound is composed of vanadium(V) oxide layers with nickel atoms coordinated within a single layer via four Ni-O-V linkages. Bidentate bipyridine (bpy) ligands complete the coordination sphere of the nickel atoms and interdigitate via π-π stacking with bpy ligands from the adjacent layer. Cu(en)₂[V₆O₁₄] (2) crystallizes as black plates in the space group P2₁/n (14) with unit cell parameters a=8.934(2) Å, b=6.558(1) Å, c=15.694(2) Å, β=99.93(2)°(R(Rw)=0.039(0.035)), from the reaction of CuCl₂·2H₂O, V₂O₅, H₂O and ethylenediamine in the ratio 1:1:447:4. This structure consists of mixed-valent vanadium(IV,V) oxide sheets forming weak O-Cu bonds to intercalated copper bis(ethylenediamine) complexes.