Crystal structure of di-µ-tropolonato-bis[aquo(tropolonato)nickel( II )]

Crystals of the title compound are monoclinic, a= 9·720(7), b= 18·888(17), c= 7·146(3)Å, β= 97·97(5)°, Z= 4, space group P21/n. The structure was determined from diffractometer data by the heavy-atom method and refined by full-matrix least squares to R 0·082 for 1191 observed reflections. The molecule exists as a centrosymmetric dimer and contains two types of tropolone ligand: one co-ordinated to one nickel atom only, the other, co-ordinated both to the first nickel atom, and to a second nickel via a bridging oxygen atom. This, together with a co-ordinated water molecule gives the nickel atoms six-co-ordination. There is evidence for hydrogen bonding, via the water molecule, between adjacent dimers.