The structure of tetramethylammonium tetrachloroferrate(II), [(CH3)4N]2[FeCL] has been determined from three-dimensional X-ray data collected by counter techniques. The material crystallizes in the orthorhombic space group D2h 16-Pnma with a = 12.312 (2) Å, b = 9.033 (2) Å, c = 15.580 (3) Å, Z = 4, pmeasd = 1.32 (1) g/cm3, and pealed = 1.326 g/cm3. The structure has been refined by a full-matrix least-squares procedure to a conventional R index (on F) of 0.053 for 1149 observations having Fo2 > 3σ(Fo2). The iron atom has a crystallographically imposed mirror plane and has a slightly distorted tetrahedral geometry. The Fe(II)-Cl bond distances are 2.2902 (23), 2.2958 (16), and 2.2891 (23) Å and average 2.292 (2) Å. Previous studies have shown that in the FeCU anion Fe(III)-Cl bond distances average 2.185 Å. The FeCU2 anion (high-spin Fe(II)) thus has bond lengths 0.11 Å longer than those found in the FeCU anion (high-spin Fe(IIl)). This expansion of the coordination sphere upon reduction is larger than is found in octahedral complexes. Similar changes in bond lengths are to be expected in some of the iron-sulfur proteins.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry