
%0 Journal Article
%A Baker, AT 
%A Ferguson, NJ 
%A Goodwin, HA 
%A Rae, AD 
%T Structural, Magnetic and Spectral Properties of Iron(II) and Nickel(II) Complexes of N<sup>1</sup>-(Pyridin-2-yl)-3,5-dimethylpyrazole
%J Australian Journal of Chemistry
%D 1989/05/01
%V 42
%N 5
%P 623-638
%K 
%R https://doi.org/10.1071/CH9890623
%U https://www.publish.csiro.au/paper/CH9890623 
%X Iron(II) and nickel(II) complexes of N1-(pyridin-2-yl)-3,5-dimethylpyrazole (L) are described. Salts of [FeL3]2+ undergo a reversible temperature-induced singlet (1A1) &#8596; quintet (5T2) transition, both in the solid state and in solution. The singlet- quintet change in acetone solution is characterized by &#916;H = 25 ± 2 kJ mol-1 and &#916;S = 95 ± 5 J K-1 mol-1. Mossbauer spectral data for solid [FeL3] [BF4]2 confirm a change in ground state for the metal atom with change in temperature and indicate two low-spin species at low temperatures and two high-spin species at elevated temperatures. The average M-N bond length changes accompanying the spin change have been estimated as 0.19 Å from data obtained by determination of the structures of [FeL3][ClO4]2 at 135 K and 294 K and of [NiL3][BF4]2 at 294 K by single-crystal X-ray diffractometry. The crystals were all refined as disordered structures in space group P3c1 with Z = 2. Crystal data: [FeL3] [ClO4]2 at 294 K, a = b 10.489(2), 17.521(5) Å ;[FeL3][ClO4]2 at 135 K, a = b 10.355(3), c 17.464(5) Å ; [NiL3] [BF4]2 at 294 K, a = b 10.404(3), c 17.618(8) Å . 
