CRYSTAL AND MOLECULAR-STRUCTURE AND SPECTRA OF K4[NI(NO2)6]CENTER-DOT-H2O AND K3[NI(NO2)4(O2N)]

The crystal structure of the orange compound K4[Ni(NO2)6].H2O has been determined. It shows that this contains an octahedral [Ni(NO2)6]4- co mplex anion with six N-bonded nitrite ligands and a water of crystalli zation. Dehydration at 100-degrees-C produces a mixture of red K3[Ni(N O2)4(O2N)] and KNO2, with the latter occurring as microcrystallites al most-equal-to 100 angstrom in size. Rehydration of the hygroscopic mix ture at almost-equal-to 20-degrees-C causes K4[Ni(NO2)6].H2O to be ref ormed. The nickel(II) in K3[Ni(NO2)4(O2N)] has a distorted octahedral ligand environment, with four nitrites co-ordinated via nitrogen, and a fifth chelating. The infrared and electronic spectra of the compound s are discussed in terms of the difference in nitrite co-ordination.