Tetrabutylammonium tetrakis(trimethylsilanolato-κO)ferrate(III)

In the title salt, (C16H36N)[Fe(C3H9OSi)4], the cation contains a central N atom bonded to four n-butyl alkyl groups in a tetrahedral arrangement, while the anion contains a central FeIII atom tetrahedrally coordinated by four trimethylsilanolate ligands.

In the title salt, (C 16 H 36 N)[Fe(C 3 H 9 OSi) 4 ], the cation contains a central N atom bonded to four n-butyl alkyl groups in a tetrahedral arrangement, while the anion contains a central Fe III atom tetrahedrally coordinated by four trimethylsilanolate ligands.
We thank the University College of the Pennsylvania State University and the Air Force Office of Scientific Research (FA9550-08-1-0213 F A9550-08-1-0213) for their financial support. The CCD-based X-ray diffractometer at Michigan State University was upgraded and/or replaced by departmental funds.
supplementary materials  containing silsesquioxane compounds (Hay et al., 2003;Hay & Geib, 2007, Hay et al., 2009. In order to make a more complete structural study of these compounds, it was useful to have structural data on an analogous tetrabutylammonium iron (III) silanolato compound -the title compound ( Fig. 1). Its structural arrangement contains a pair of tetrabutylammonium cations and tetrakistrimethylsilanolato ferrate (III) anions in a triclinic unit cell (Fig. 2). The tetrabutylammonium cation, C 16 H 36 N + , consists of a tetrahedrally arranged central nitrogen atom, with N-C bond lengths in the range of 1.515 (2)-1.520 (2) Å and C-N-C bond angles in the range of 105.74 (13)

Experimental
The following synthetic protocol is adapted from the previously reported procedure (Shapley, et al., 2003). A yellow solution of [C 16 H 36 N][FeCl 4 ] (1.136 mmol, 0.5000 g) in dichloromethane (10 ml) was treated with four equivalents of solid sodium trimethlysilanate (4.544 mmol, 0.5098 g). Immediately, the yellow solution turned red due to the formation of a dark red precipitate. The reaction mixture was stirred for 40 minutes before the precipitate was removed by filtration through celite. The resulting pale green filtrate was concentrated under reduced pressure to give a pale green powder. The powder was extracted with diethyl ether and filtered to remove any insoluble material. Hexanes were added to the diethyl ether filtrate and the sample was stored at 243 K for about 30 minutes before colorless block crystals formed which were analyzed.

Special details
Experimental. Data was collected using a BRUKER CCD (charge coupled device) based diffractometer equipped with an Oxford low-temperature apparatus operating at 173 K. A suitable crystal was chosen and mounted on a glass fiber or nylon loop using Paratone oil for Mo radiation and Mineral oil for Copper radiation. Data were measured using omega and phi scans of 0.5° per frame for 30 s. The total number of images were based on results from the program COSMO where redundancy was expected to be 4 and completeness to 0.83 Å to 100%. Cell parameters were retrieved using APEX II software and refined using SAINT on all observed reflections. Data reduction was performed using the SAINT software which corrects for Lp. Scaling and absorption corrections were applied using SADABS6 multi-scan technique (Sheldrick, 2008). The structures are solved by the direct method using the SHELXS97 program and refined by least squares method on F 2 , SHELXL97, incorporated in SHELXTL-PC. Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry.