4,4′,4′′-(Methanetriyl)triphenyl tris(2,2,5,5-tetramethyl-1-oxyl-3-pyrroline-3-carboxylate) benzene trisolvate

In the asymmetric unit of the title compound, C46H52N3O9·3C6H6, two of the benzene solvent molecules are located in general positions and two are disposed about inversion centers. One of the benzene molecules on an inversion center was grossly disordered and was excluded using the SQUEEZE subroutine in PLATON [Spek (2009 ▶). Acta Cryst. D65, 148–155]. In addition, one of the 2,2,5,5-tetramethyl-1-oxyl-3-pyrrolin-3-ylcarbonyl groups is disordered over two orientations with refined occupancies of 0.506 (2) and 0.494 (2). The 1-oxyl-3-pyrroline-3-carboxylate groups are essentially planar, with mean deviations from the planes of 0.026 (2), 0.012 (2), 0.034 (4) and 0.011 (4) Å. In the crystal structure, molecules are connected by five weak intermolecular C—H⋯O and four weak intermolecular C—H⋯π(benzene) interactions.


Related literature
For the preparation of the title compound see: Godt et al. (2000). For a related structure, see: Margraf et al. (2009). For the treatment of the disordered solvent, see: Spek (2009 Table 1 Hydrogen-bond geometry (Å , ).

Comment
The title compound was prepared as a reference compound for pulsed electron-electron double resonance measurements (Godt et al., 2000).
The crystal packing is shown in Fig. 2. The asymmetric unit contains a triphenylmethane-4,4',4"-triyl tris(2,2,5,5-tetramethyl-1-oxyl-3-pyrroline-3-carboxylate) molecule, two benzene solvent molecules in general positions and two benzene solvent molecules positioned about inversion centers. One of the latter groups was found to be seriously disordered and was included in the calculations by using program PLATON/SQUEEZE (Spek, 2009). There are five intermolecular C-H···O contacts with H···O distances between 2.44 and 2.58 Å and four intermolecular C-H···π benzene contacts with H···Cg distances between 2.78 and 2.94 Å (Table 1, Cg represents the centroid of the benzene ring).

Experimental
The title compound was prepared from tris(4-hydroxyphenyl)methane in analogy to the procedure described by Godt et al. (2000). Single crystals were obtained by recrystallization of the compound from benzene.
The electron density count in this region was found to be 42 electrons, in perfect agreement with the value expected for a benzene molecule and the contribution from the additional benzene molecule was added to the empirical formula. The supplementary materials sup-2 2,2,5,5-tetramethyl-1-oxyl-3-pyrroline-3-carbonyl group attached to atom O7 was found to be disordered over two possible orientations. Consequently, atoms in this group were refined as split atoms and treated as isotropic, except for the O atoms which were refined with anisotropic displacement parameters. The occupancy factor refined to 0.494 (2) for atoms, O8, O9, N3 and C38 → C46 and to 0.506 (2) for atoms O8', O9', N3' and C38' → C46'. A refinement as an ordered structure in space group P 1 converged at wR(F 2 )=0.295, R[F 2 >2σ(F 2 )]=0.107 and showed residual density up to 1.21 e.A -3 in the 2,2,5,5-tetramethyl-1-oxyl-3-pyrroline-3-carbonyl group, which was disordered in space group P 1. Thus an ordered structure can be excluded. Oxygen atom O7 could not be split to meaningful positions within the experimental resolution. As a result, the observed values of the C35-O7-C38 and C35-O7-C38' angles [128.4 (3) and 140.5 (3)° ] are too large.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.