The approximate structure of the tris-(2-aminoethylpyridine)-nickel(II) complex ion

Abstract

Tris-(2-aminomethylpyridine)Ni(II) perchlorate crystallizes in space group P~t3n with a= 16.95 (1)A. The complexed Ni(II) ion must exhibit threefold symmetry and each pyridine ring must be cis to the other two.Ni(CsHsN-CH2-NH2)3(CIO4)2, tris(2-aminomethylpyridine)nickel(II) perchlorate, was prepared by mixing acetoneethanol solutions of Ni(C104)z and 2-aminomethylpyridinc. Slow evaporation yielded magenta prismatic crystals.From Weissenberg and precession X-ray photographs the crystals were found to be cubic with space group P~3n Fig. 1. View prepared from a scale model of the structure in which an approximate dihedral angle of 15 °, natural to the model, was used for the exocyclic C-C bond.* Author to whom correspondence should be addressed.(hkl, no conditions; hhl, 1= 2n; and cyclicly). These photographs do not suggest disorder. The cell constant, as determined by a least-squares refinement of fifteen intense reflections with 20 values up to 23 °, is a= 16.95 (1) A at 19°C. For this, a Syntex computercontrolled diffractometer with MoKc~ (2=0.71069 /~) radiation was used. Using a molecular weight of 585.06 amu and assuming eight formula-weights per unit cell, a density of 1.595 g.cm -3 can be calculated which agrees well with the observed value, 1.585 g.cm -a, measured by flotation in CCL (0 = 1.585 g.cm-a).Considering the symmetry of the ligand, and assuming that the complexed cation is not disordered, these conclusions follow: the Ni(II) ions are at Wyckoff positions 8(e) of PT~3n on the threefold axes; the complexed Ni(II) ions contain a molecular threefold axis; and each of the three pyridine rings must be cis to each of the other two. It is felt that the coordination configuration is nearer to trigonal antiprismatic (pseudo-octahedral) (see, for instance, Swink & Atoji, 1960) than to trigonal prismatic, which has been found only where the ligands impose particularly severe constraints (see Parks, Wagner & Holm, 1970) on the coordination geometry. Since the five-membered NiNCC'"N rings cannot deviate greatly from planarity due to ring strain, an apt~roximate model (see Fig. 1) of the complexed cation was, e .dily assembled. No further work is planned. Acta Cryst. (1972). B28, 2298Strucfu.'e cristalline du radical nitroxyde: sub6rate de di-t6tram6thy1-2,2,6,6-pip6ridinyl-4-oxyle 1. Par At~-m CAPIOMONT, Laboratoire de Spectromdtrie Physique, Universitd Scientifique et M~dicale de Grenoble, Cedex 53, 38 -Grenoble-Gate, France (Recu le 6 mars 1972) Di-(2,2,6,6-tetramethyl-4-piperidinyl-l-oxyl) suberate C26H46N206 is a nitroxide radical which crystallizes in the monoclinic system, space group P21/c. The dimensions of the unit cell are a= 6.041, b =21.52, c= 13.62 A, ,8= 126.360 °. There are two molecules in a cell, each at a centre of symmetry.Le sub6rate de di-t6tram6thyl-2,2,6,6-piperidinyl-4-oxyle 1 a 6t6 synth6tis6 au Laboratoire de Chimie Organique Physique du CENG (Professor Rassat) (Rey, 1967). II fait, d'autre part, l'objet d'6tudes de r.p.e., de chaleur sp6cifique et de susceptibilit6 magn6tique ~t...