1,1′-Methylenebis[3-(2,6-diisopropylphenyl)-3,4,5,6-tetrahydropyrimidin-1-ium] dibromide ethanol monosolvate monohydrate

In the title methylene-bridged di(tetrahydropyrimidinium) salt, C33H50N4 2+·2Br−·C2H5OH·H2O, the two tetrahydropyrimidinium rings have envelope conformations with the central CH2 C atom as the flap. Their mean planes are inclined to one another by 73.31 (13)° and the attached benzene rings are inclined to one another by 67.39 (15)°. The methylene-C—N bond lengths in the tetrahydropyrimidinium rings are 1.314 (3) and 1.304 (3) Å, values typical for C=N double bonds. The distances between the methylene-bridge C atom and the linked tetrahydropyrimidinium N atom are 1.457 (3) and 1.465 (3) Å, values typical for C—N single bonds. The molecules co-crystallized with H2O and EtOH molecules from the solvent. In the crystal, there is a zigzag chain along [010] of water molecules linked by one of the Br− anions via O—H⋯Br hydrogen bonds. The second Br− anion is hydrogen bonded (O—H⋯Br) to the ethanol solvent molecule. There are also a number of C—H⋯Br and C—H⋯O hydrogen bonds present, leading to the formation of a two-dimensional network lying parallel to the bc plane.


Related literature
For the synthesis of the precursor bis(3-(2,6-diisopropylphenyl)-hexahydropyrimidinyl)methane, see: Bisceglia et al. (2004). For metal complexes of substituted 1,4,5,6-tetrahydropyrimidines, see: Mao et al. (2012). H atoms treated by a mixture of independent and constrained refinement Á max = 0.53 e Å À3 Á min = À0.40 e Å À3 Table 1 Hydrogen-bond geometry (Å , ). tetrahydropyrimidinium salts, we observed that the methylene linkage broke during the metallation process. In the search for possible reasons leading to the breakage of the linkage, we carried out the X-ray crystal structure analysis of the methylene bridged tetrahydropyrimidinium dibromide.
In the structure of the title compound, Fig. 1, the C-N of the tetrahydropyrimidinium ring and the linkage showed typical values of double and single bonds, respectively. The title molecule co-crystallized with H 2 O and EtOH molecules from the solvent. The two tetrahydropyrimidinium rings have envelope conformations with the central CH 2 C atoms, C2 and C7, as the flaps. Their mean planes are inclined to one another by 73.31 (13) ° and the attached benzene rings are inclined to one another by 67.39 (15) °.
In the crystal, there is a zigzag chain along [010] of water molecules linked to one of the Branions via O-H···Br hydrogen bonds (Table 1). The second Branion is hydrogen bonded (O-H···Br) to the ethanol solvent molecule (Table   1). There are also a number of C-H···Br and C-H···O hydrogen bonds present, leading to the formation of a twodimensional network lying parallel to the bc plane (Table 1).

Refinement
The water H-atoms were located in a difference electron-density map and freely refined. The OH and C-bound H-atoms were included in calculated positions and treated as riding atoms: O-H = 0.82 Å, C-H = 0.93, 0.97 and 0.96 Å for CH, CH 2 , and CH 3 H-atoms, respectively, with U iso (H) = k × U eq (C), where k = 1.5 for OH and CH 3 H-atoms, and = 1.

Figure 1
The molecular structure of the title molecule, with atom labelling. The displacement ellipsoids are drawn at the 30% probability level. Hydrogen atoms and solvent molecules have been omitted for clarity.
Special details 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. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 R-factors(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