METAL-COMPLEXES OF 1,3-BIS(PYRIDIN-2-YL)PYRAZOLE - SPECTRAL, MAGNETICAND STRUCTURAL STUDIES

Bis(ligand) iron(II) and nickel(II) complexes of the asymmetric triden tate ligand 1,3-bis(pyridin-2-yl)pyrazole, L, have been prepared. The iron(II) complex, [FeL(2)] [PF6](2), is high-spin in the solid state o ver the temperature range 304-102 K, with a magnetic moment of 5 . 27 BM at room temperature. The crystal structure of bis(1,3-bis(pyridin-2 -yl)pyrazole)iron(II) bis(hexafluorophosphate) has been determined by single-crystal X-ray diffractometry. The compound crystallized as yell ow prisms, with the structure being disordered in the tetragonal space group P (4) over bar 2(1)c with Z = 2. Crystal data a = b = 8 . 785(1 ) Angstrom, c = 19 . 804(6) Angstrom. The iron(II) centre is in an N-6 environment, where the six donor nitrogen atoms are provided by the t wo tridentate heterocyclic ligands. The complex cation has an approxim ately octahedral structure exhibiting tetragonal compression. The obse rved Fe-N(pyridine) and Fe-N(pyrazole) distances are 2 . 308(4) and 2 . 019(7) Angstrom respectively, with the Fe-N(pyridine) distance being the longest observed to date.