Kh. Sugiyarto et al., STRUCTURAL AND ELECTRONIC-PROPERTIES OF IRON(II) COMPLEXES OF 2-(1,2,4-TRIAZOL-3-YL) PYRIDINE AND SUBSTITUTED DERIVATIVES, Australian Journal of Chemistry, 48(1), 1995, pp. 35-54
Iron(II) and nickel(II) tris(ligand) complexes of 2-(triazol-3-yl)pyri
dine and the substituted derivatives 2-(1(N)-methyltriazol-3-yl) pyrid
ine and 2-(1,5-dimethyltriazol-3-yl)pyridine have been prepared. Coord
ination of the dimethyl-substituted ligand via N(4) of the triazolyl m
oieties is confirmed by structure determination of [FeL(3)][BF4](2), w
hich has the mer configuration. Tris(2-(1,5-dimethyltriazol-3-yl)pyrid
ine)iron(II) bis(tetrafluoroborate): orthorhombic, space group Pbca, a
11.568(3), b 19.442(4), c 30.551(8) Angstrom, Z 8. The methyl substit
uents appear to have only a minor influence on the donor properties of
the ligands, all three of which have field strengths in the iron(Ir)
quintet reversible arrow singlet crossover region. Temperature-induced
singlet reversible arrow quintet transitions occur in salts of the [F
eN6](2+) derivatives in both the solid and solution states. Mossbauer
effect studies reveal the complexity of the solid state properties of
salts of the iron complex of 2-(1(N)-methyltriszol-3-yl)pyridine and s
uggest that there is a fundamental change with time in the geometry of
the complex cation. The metastable form of the complex hexafluorophos
phate salt shows virtually no quadrupole splitting in the spectrum for
the quintet state species, which implies high symmetry for the metal
ion environment. Mossbauer studies further reveal the presence of mult
iple iron(II) sites in the lattice for salts containing either the N-m
ethyl or the unsubstituted ligand.