Crystal structure of [Fe(L¹)₂](ClO₄)₂.H₂O having Fe^IIN₆ coordination [L¹= 2,6- bis(pyrazol-1-ylmethyl)pyridine]

Abstract

The structure of the compound [Fe(L¹)₂](ClO₄)₂.H₂O (<b>1)</b>[L¹= 2,6-

bis(pyrazol-1-ylmethyl)pyridine] has been determined by X-ray crystallography at ≈130 K. Temperature-dependent magnetic susceptibility and Mossbauer spectral studies reveal that the iron atom in 1 is in the high-spin state at room temperature and in the low-spin state at low temperature, whereas in [Fe(L²)₂](ClO₄)₂.H₂O (<b>2</b>) and [Fe(L³)₂](ClO₄)₂.H₂O (<b>3</b>) [L² = 2,6-bis(3,5-

dimethylpyrazole-1-ylmethyl)pyridine and L³= 2-(pyrazol-1-ylmethyl)-

6-(3,5-dimethylpyrazol-1-ylmethyl)pyridine) the iron atom is in the high-spin state at both the temperatures [Mahapatra S, Mukherjee R, <i>Polyhedron </i>12 (1993) 1603]. The metal-ligand bond distances in <b>1</b> have been compared with those of <b>3</b>, determined at ≈173 K [Mahapatra S, Butcher R J, Mukherjee, R,

J <i>chem Soc, Dalton Trans </i>(1993) 3723]. The Fe-N_pyridine and Fe-N_pyrazole

bond distances in <b>1</b> are shorter by ~0.23 Å and ~0.14 Å,respectively, than those for the high-spin complex <b>3</b>, revealing its low-spin character. Moreover, a noticeable variation of the N-Fe-N angles, leading to a more regular shape of the Fe^IIN₆ octahedron in <b>1</b>, is observed.