Search

Mixing an aqueous solution of K8[Nb6O19]⋅16H2O with a DMSO/H2O solution of Cu(ClO4)2 · 6 H2O and cyclen at room temperature afforded crystallization of blue crystals of [(Cu(cyclen))6Nb6O19]⋅[ClO4]4·≈4H2O after slow evaporation of the solvents. The crystal structure contains the Lindqvist anion [Nb6O19]8– which is covalently expanded by six symmetry-related [Cu(cyclen)]2+ complexes via Nb-μ 2-O-Cu bridges yielding the positively charged [(Cu(cyclen))6Nb6O19]4+ cluster shell. The ClO4 − anions and crystal water molecules reside in the empty spaces of the packed clusters. The compound shows two electronic d-d transitions at energetic positions explaining the blue color.

The new compound {[Cu(phen)]2[Cu(phen)2]2Nb6O19}·24H2O (I) (phen = 1,10-phenanthroline) was prepared under ambient conditions. The crystal structure is composed of the [Nb6O19]6– anion which is exp...

Syntheses were performed at room temperature using Ni(NO3)2·6H2O, cyclam (cyclam = 1,4,8,11-tetraazacyclotetradecane) and the precursors Li8[Nb6O19]· ≈22H2O or Na7[HNb6O19]·15H2O in a DMSO-H2O mixture. Yellow crystals of the new compound {[Ni(cyclam)]2H4Nb6O19}·12H2O could be obtained after one week applying the Li+ or Na+ salt as starting materials. The crystal structure is unique in polyoxoniobate (PONb) chemistry and displays two interpenetrating three-dimensional (3D) networks. The [Nb6O19]8– anion is expanded by four Ni2+ centered complexes via Ni–O bonds to terminal O2− anions of the hexaniobate anion. The 3D networks are generated by further Ni–O bond formation between neighboring [Nb6O19]8− anions. The remaining void space is occupied by H2O molecules which form a water cluster.

The room temperature reaction of Hg(NO3)2 · H2O, cyclam (cyclam = 1,4,8,11-tetraazacyclotetradecane) and K8{Nb6O19} · 16 H2O in a mixture of H2O and DMSO led to crystallization of the novel compound {[Hg(cyclam)]6Nb6O19}(NO3)4 · 14 H2O, which is the first mercury containing polyoxoniobate. The structure consists of a {Nb6O19}8− cluster core which is expanded by six [Hg(cyclam)]2+ complexes via Hg–μ 2-O–Nb bond formation. The title compound contains a positively charged polyoxoniobate cluster. The crystal water molecules form small aggregates by O–H · · · O hydrogen bonding which are joined into larger aggregates by N–O · · · H–O hydrogen bonding integrating the nitrate anions.