Synthesis and Crystal Structure of 3-3’-Diaminomethyldipropylammonium Hexachlorobismuthate (III)

Synthesis and crystal structure of 3-3’-diamino-N-methyldipropylammonuim hexachlorobismuthate (III) are reported. The compound crystallizes in the triclinic system with space group P1. The unit cell dimensions are: a = 7.5580(5), b =7.8710(6), c = 8.3709(7) Å with Z=1. The crystal is built up of separated [BiCl 6 ] 3- octahedral anions and 3-3’-diamino-N- methyldipropylammonium cations. The organic layers are arranged in sandwich between the anionic ones. The crystal packing is governed by means of the ionic N–H···Cl hydrogen bonds, forming a three dimensional network.


I. Introduction
Recently, much attention has been focused on organic-inorganic hybrid materials based on metal-halide units; those materials are frequently characterized by their various physical and chemical properties that could lead to technological innovations like magnetic or ferroelectric transitions, conductivity (super conductivity), electroluminescence and photoluminescence [1][2][3][4][5][6]. To date, numerous metal-halide systems involving Sn, Pb, Sb, Bi, and Te have been synthesized and structurally characterized [7][8][9][10][11][12]. The anionic metal-halide species has been observed to range in dimensionality from two-dimensional or one dimensional polymeric anions to discrete anions of various sizes. The polyhedral may be linked by corner-, edge-, or face-sharing into numerous different arrangements; and consequently, halometallate compounds exhibit very great structural diversity [8,10,13]. The identity of the anions formed has been found to depend on the specific reaction conditions employed including the size, shape, the reagent stoichiometry, and ability to form the hydrogen bond system by the cations. The bismuth compounds represent a potential class of materials with unusual structural arche-types, due to the fact that the Bi(III) ion exhibits a variety of coordination modes, depending on crystal packing and on ligands: octahedral coordination being observed.
The polyhedra may be linked by corner-, edge-, or face sharing into numerous different arrangements, leading to an extensive family of bismuth ( [14][15][16][17][18][19]. The structure of the anionic form is related to the size and symmetry of the organic counter-ions and their ability to form hydrogen bonds as well. In fact, besides the rich structural diversity displayed by these systems, some interest has been directed towards halobismuthate(III) compounds in combination with organic cations, due to their very interesting physical properties caused by active lone pairs [20].
In an attempt to study the effects of the size and the coordination mode of the cation in this class of compounds, we have successfully synthesized a new compound of formula [C7H22N3]BiCl6.
In the present paper, we report the synthesis and the structural characterization by X-ray diffraction of the 3-3'-diamino-Nmethyldipropylammonium hexachlorobismuthate (III).

II.1.Synthesis
Single crystals of the title compound were prepared at 300 K by slow evaporation of a saturated aqueous solution obtained by dissolving C7H19N3 and BiCl3 (molar ratio 3/1) in 36% HCl. The resulting solution is kept under ambient conditions which were allowed to evaporate slowly. A few days later prismatic crystals were obtained.

II.2.Single crystal structure determination
The X-ray data collection was carried out on Enraf-Nonius Kappa CCD diffractometer using Ag Kα radiation .The positional parameters for the heavy atoms were obtained from a three-dimensional Patterson map, while the non-H atoms were found from successive difference Fourier Maps. The structure was refined by full-matrix least squares using anisotropic temperature factors for all non-hydrogen atoms and the hydrogen atoms were localized and optimized to restrained positions. Calculations were performed with the programs SHELXS [21], using the scattering factors enclosed therein. The crystal data, collected reflections and parameters of the final refinement are reported in Table 1.

III. Results and discussion
The final atomic coordinates obtained from the single crystal refinement with Ueq are given in Table 2. Table 3 shows the anisotropic displacement parameters. Interatomic distances and bond angles schemes are listed in Table 4.

Fig 2: Projection in the plane (b,c) of the atomic arrangement of [C7H22N3]BiCl6
Each Bi atom is surrounded by six Cl atoms, forming a distorted octahedral configuration, with Bi-Cl bond lengths ranging from 2,668(4) to 2,734(3) Å (Table 4) and a mean value of 2.727(2) Å, and Cl-Bi-Cl bond angles ranging from 71.87 (2) to 97.91(3)° for cis and from 100.21 (2) to 166.56(2)° for trans arrangements. These values are comparable with those reported to date [20]. Mar c h 10, 2 0 1 4 In addition to the bond length differences, the Cl-Bi-Cl bond angles (  (5) angle, which incorporates the two shortest Bi-Cl bonds. This distortion is correlated both to primary deformations resulting from the stereochemical activity of the Bi lone electron pair [20,22] and to secondary deformations resulting from hydrogen bond interactions [23].
The involvement of any particular chlorine atom in hydrogen bonding brings about the shift of the lone electron pair of the Bi atom in the direction of the H atom, which generally results in the shift of the respective Cl atom out of the Bi position. This leads to an increase in the Bi-Cl bond length (Bi-Cl1: 2.73 (3),  and  Å) compared to the others. Figure 2 shows that the 3-3'-diamino-N-methyldipropylammonium cations are interspersed between the anionic plans at z =1/2. The C-N and C-C bond lengths vary respectively from 1.442(2) to 1.56(2) and 1.47(3) to 1.59(2) Å .These values are comparable with those reported by other researchers [24].

Table4. Principal intramolecular distances (Å), bond angles (°) in [C7H22N3] BiCl6
Atoms Distance Atoms Distance formation of these hydrogen bonds, with distances between 2.310 and 3.76 Å. Tow of these bonds are considered as strong, whilst the others are weak [25]. Details of the hydrogen bonding scheme are reported in Table 5.

Conclusion
The 3-3'-diamino-N-methyldipropylammonium hexachlorobismuthate (III) belongs to the triclinic system with P1 space group. The crystal structure consists of the monomeric [BiCl6] 3and one crystallographically independent triprotonated 3-3'-diamino-N-methyldipropylammonium cation. The structure of this compound consists of alternation organic and inorganic layers. These layers are themselves interconnected by means of the ionic N-H…Cl hydrogen bonds.