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

Abstract

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 Ni^II cations, with both of them coordinated by one tren ligand into discrete units. Both Ni^II 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.

Keywords: Lindqvist-type anion; crystal structure; layered structure; polyoxidotantalate.