Wikipedia
The nitronickelates are a class of chemical compounds containing a nickel atom complexed by nitro groups, -NO. Nickel can be in a +2 or +3 oxidation state. There can be five (pentanitronickelates), or six, (hexanitronickelates) nitro groups per nickel atom. The can be considered the double nitrites of nickel nitrite.
formula
name
structure
Remarks
references
Rb[Ni(NO)]
trirubidium pentanitronickelate(II)
Cs[Ni(NO)]
tricesium pentanitronickelate(II)
dark red, formed from cesium nitrite and nickel nitrite in water
K[Ni(NO)]
potassium hexanitronickelate
4 nitro groups bonded to Ni by N, 2 by O (-ONO)
formed by heating monohydrate at 100 °C dark purple; hygroscopic
K[Ni(NO)]•HO
potassium hexanitronickelate monohydrate
hexagonal a=7.634 Å c=22.45 Å Z=3; nitro groups bonded to Ni via N; water not coordinated
formed from KNO and NiCl mix in water; orange brown; stable in vacuum
KCa[Ni(NO)]
potassium calcium hexanitronickelate
cubic a=10.31 Z=4
buff
KSr[Ni(NO)]
potassium strontium hexanitronickelate
cubic a=10.5063 Z=4 density=2.867
brown yellow
KBa[Ni(NO)]
potassium barium hexanitronickelate
cubic Fm3 (and m3m) a=10.7800 Z=4 density=2.918
brown yellow
KPb[Ni(NO)]
potassium lead hexanitronickelate
cubic Fm3 a=10.577 Z=4 density=3.480: No NO group disorder
buff colour;
N(CH)[Ni(NO)]
tetramethylammonium nickel nitrite TMNIN
Hexagonal Perovskite Pm1 a=9.103 Å c=7.082 Å V=508.2 Å Z=2 density=1.770 all nitros are bidentate, nickel either links to N or O of the NO, forming a chain of nickel alternating with ONO
yellow brown; one-dimensional Heisenberg antiferromagnet; Haldane material; phase transitions at 409.1 and 428.4 K due to rotation of N(CH)