Substitutional disorder in the ionic diorganoantimony halide adduct [bromido/chlorido(0.33/0.67)][2-(dimethylaminomethyl)phenyl][2-(dimethylammoniomethyl)phenyl]antimony(III) 0.75-bromide 0.25-chloride

The title complex, [SbBr0.33Cl0.67(C9H13N)(C9H12N)]Br0.75Cl0.25, exhibits substitutional disorder of both halogen atoms in the asymmetric unit, however, with different occupancies. Thus, the halogen atom bonded to Sb has 0.67 (4) occupancy for Cl and 0.33 (4) for Br, while the anionic halogen atom shows 0.75 (4) occupancy for Br and 0.25 (4) for Cl. An N—H⋯Cl/Br hydrogen bond is established between the cation and the halide anion. The coordination geometry of the Sb center in the cation is distorted pseudo-trigonal-bipyramidal as a result of the strong intramolecular N→Sb coordination trans to the Sb—Cl/Br bond. The pendant arm on the second ligand is twisted away from the metal center. The compound crystallizes as a racemate, i.e. a mixture of (R N2,C Sb1) and (S N2,A Sb1) isomers with respect to planar chirality induced by the coordinating N atom and chelate-induced Sb chirality. These isomers are associated through Cphenyl—H⋯Cl/Br hydrogen bonds, forming a three-dimensional architecture.

Financial support from the National University Research Council (Research Project PNII-ID 2052/2009) is greatly appreciated. We also thank the National Center for X-ray Diffraction (Babes-Bolyai University, Cluj-Napoca, Romania) for support of the solid-state structure determinations.  (Opris et al., 2003), having only a slightly smaller cell volume. Coordination of N atom induces planar chirality, with the phenyl ring as chiral plane and the nitrogen as pilot atom (IUPAC, 1979). This intramolecular coordination of the nitrogen atom to antimony induces chirality at the Sb centre (IUPAC, 2005). Thus the compound crystallizes as a racemate, i.e. a mixture of (R N2 ,C Sb1 ) and (S N2 ,A Sb1 ) isomers ( Fig

Experimental
In the attempted synthesis of R 2 SbMes from mesitylmagnesium bromide and R 2 SbCl.(R = 2-Me 2 NCH 2 C 6 H 4 ), crystals of the title compound were isolated from a chloroform-hexane mixture, due to partial hydrolysis followed by the protonation of one of the organic ligands.
supplementary materials sup-2 Refinement All hydrogen atoms, except H1 attached to N1, were placed in calculated positions using a riding model, with C-H = 0.93-0.97 Å and with Uiso=1.5Ueq (C) for methyl H and Uiso= 1.2Ueq (C) for aryl H. The methyl groups were allowed to rotate while retaining tetrahedral geometry. The H1 hydrogen atom attached to N1 nitrogen atom was located from the difference map and the N1-H1 distance was restrained to 0.86 Å. The two halide atoms were refined as substitutional disorder between chlorine and bromine, with 0.67 occupancy for Cl and 0.33 for Br for Cl1/Br1 and 0.75 occupancy for Br and 0.25 for Cl for Cl2/Br2. Fig. 1. A view of the asymmetric unit showing the atom-numbering scheme at 30% probability thermal ellipsoids for the (R N2 ,C Sb1 ) isomer. Fig. 2. Molecular structure at 30% probability ellipsoids of (R N2 ,C Sb1 ) (a) and (S N2 ,A Sb1 ) (b) isomers present in crystals of the title compound. Only the cationic fragment is shown. All hydrogen atoms except H1 atoms have been omitted. Symmetry code: (i) 1-x, 1-y, -z.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ.