Decoration of the [Nb6O19]8– cluster shell with six Cu2+-centred complexes generates the [(Cu(cyclen))6Nb6O19]4+ moiety: room temperature synthesis, crystal structure and selected properties

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.

Synthesis and crystal structure of bis-[μ-N,N-bis-(2-amino-eth-yl)ethane-1,2-di-amine]-bis-[N,N-bis-(2-amino-eth-yl)ethane-1,2-di-amine]-μ4-oxido-hexa-μ3-oxido-octa-μ2-oxido-tetra-oxido-tetra-nickel(II)hexa-tantalum(V) nona-deca-hydrate

Reaction of K8{Ta6O19}·16H2O with [Ni(tren)(H2O)Cl]Cl·H2O in different solvents led to the formation of single crystals of the title compound, [Ni4Ta6O19(C6H18N4)4]·19H2O or {[Ni2(κ4-tren)(μ-κ3-tren)]2Ta6O19}·19H2O (tren is N,N-bis-(2-amino-eth-yl)-1,2-ethanediamine, C6H18N4). In its crystal structure, one Lindqvist-type anion {Ta6O19}8- (point group symmetry ) is connected to two NiII cations, with both of them coordinated by one tren ligand into discrete units. Both NiII cations are sixfold coordinated by O atoms of the anion and N atoms of the organic ligand, resulting in slightly distorted [NiON5] octa-hedra for one and [NiO3N3] octa-hedra for the other cation. These clusters are linked by inter-molecular O-H⋯O and N-H⋯O hydrogen bonding involving water mol-ecules into layers parallel to the bc plane. Some of these water mol-ecules are positionally disordered and were refined using a split model. Powder X-ray diffraction revealed that a pure crystalline phase was obtained but that on storage at room-temperature this compound decomposed because of the loss of crystal water mol-ecules.