(NBu4)Ni(mnt)2: A novel bistable high temperature spin-Peierls-like system

Abstract The title compound, tetrabutylammonium bis(1,2-dimercaptoethene-1,2-dicarbonirtilato-S,S′)-nickel (III) [henceforth (NBu4)Ni(mnt)2] undergoes a hysteretic phase transition that occurs at 172 K upon cooling. Crystallographic studies show that the phase transition is an order–disorder type involving one arm of the NBu 4 + cation. Both phases are monoclinic, space group C2/c with a = 30.860(3), b = 13.804(2), c = 15.678(2) A and β = 115.642(3)° with V = 6020.8(11) A3 at room temperature and with a = 31.073(3), b = 13.928(1), c = 14.414(1) A and β = 115.073(2)° and V = 5652.1(9) A3 at 84 K. In both phases, the anions form non-uniform stacks parallel to the crystallographic c direction.…