The crystal structure of Fe(q-6-mesitylene)22 (1) is reported. The structure is intricately disordered with the Fe-atom occupying an m3m cubic site, but nonetheless the conformation and bonding is confirmed. The structure is discussed in the general context of Fe" sandwich complexes.
1. Introduction.
-A wide range of neutral and monocationic sandwich compounds has been characterized crystallographically [ 11 [2]. However, dicationic analogues have received comparatively little attention until recently, when it was realized that bis(arene)iron(II) dications, amongst other sandwich compounds, are capable of adopting stacked solid-state structures [3] [4]. Our interest in the chemistry of [Fe(r b-arene),]2+ dications, and the structure and bonding in their derivatives [5-71 prompted us to examine the crystal structure of Fe(q6-mesitylene),, (1).
2. X-Ray Crystallography.
-Orange crystals of the title complex were sealed in thin walled capillaries. An Enraf-Nonius CAD4 diffractometer (graphite monochromator, MoK, radiation) was used to determine lattice parameters and for data collection. The lattice parameters were later confirmed by long-exposure rotation photographs and by upper-layer Weissenberg photographs. There was no evidence from these photographs to support a doubling (or greater factor) of the axial lengths. The photographs were also used to confirm that the systematic absences were consistent with an F-centred unit cell, and that none of the systematically absent reflections were even weakly observed. Data collection and refinement parameters are given in Table I . Scattering factors for neutral atoms were taken from the International Tables for X-Ray Crystallography [8] and were corrected for the real part of the anomalous dispersion. The data were collected as for an F-centred orthorhombic cell. The intensities were reduced to a standard scale by routine procedures, [9] and Lorentz, polarisation, and absorption corrections (DIFABS [ 101) were applied. The reflections were merged to a unique set [I 11. Three reflections were found to have widely varying measurements, and these were excluded from the subsequent refinement. The structure was refined on F by full-matrix least-squares procedures, ')