Crystal structure of N-[3-(di­methyl­amino)­prop­yl]-N′,N′,N′′,N′′-tetra­methyl-N-(N,N,N′,N′-tetra­methyl­form­amid­in­ium­yl)guanidinium bis­(tetra­phenyl­borate)

Ioannis Tiritiris; Willi Kantlehner

doi:10.1107/S2056989015023336

. 2015 Dec 12;71(Pt 12):o1045–o1046. doi: 10.1107/S2056989015023336

Crystal structure of N-[3-(dimethylamino)propyl]-N′,N′,N′′,N′′-tetramethyl-N-(N,N,N′,N′-tetramethylformamidiniumyl)guanidinium bis(tetraphenylborate)

Ioannis Tiritiris ^a, Willi Kantlehner ^a,^*

PMCID: PMC4719971 PMID: 26870490

Abstract

In the title salt, C₁₅H₃₆N₆ ²⁺·2C₂₄H₂₀B⁻, the three N—C bond lengths in the central C₃N unit of the bisamidinium ion range between 1.388 (3) and 1.506 (3) Å, indicating single- and double-bond character. Furthermore, four C—N bonds have double-bond character. Here, the bond lengths range from 1.319 (3) to 1.333 (3) Å. Delocalization of the positive charges occurs in the N/C/N and C/N/C planes. The dihedral angle between both N/C/N planes is 70.5 (2)°. In the crystal, C—H⋯π interactions between H atoms of the cation and the benzene rings of both tetraphenylborate ions are present. The benzene rings form aromatic pockets, in which the bisamidinium ion is embedded. This leads to the formation of a two-dimensional supramolecular pattern along the ab plane.

Keywords: crystal structure, bisamidinium salt, tetraphenylborate, C—H⋯π interactions

Related literature

For the synthesis of similar salts to the title compound, see: Bauer et al. (1968 ▸). For the crystal structure of N,N,N′,N′-tetramethylchloroformamidinium chloride, see: Tiritiris & Kantlehner (2008 ▸). For the crystal structures of alkali metal tetraphenylborates, see: Behrens et al. (2012a ▸). For the synthesis of N′′-[3-(dimethylamino)propyl]-N,N,N′,N′-tetramethylguanidine, see: Tiritiris & Kantlehner (2012b ▸). For the crystal structure of N,N,N′,N′-tetramethyl-N′′-[3-(trimethylazaniumyl)propyl]guanidinium bis(tetraphenylborate) acetone disolvate, see: Tiritiris (2013a ▸). For the crystal structure of N-[3-(dimethylamino)propyl]-N,N′,N′,N′′,N′′-pentamethylguanidinium tetraphenylborate, see: Tiritiris (2013b ▸). For the use of intensity quotients and differences in absolute structure refinement, see: Parsons et al. (2013 ▸).

Experimental

Crystal data

C₁₅H₃₆N₆ ²⁺·2C₂₄H₂₀B⁻
M _r = 938.92
Monoclinic,
a = 17.1964 (5) Å
b = 17.6641 (7) Å
c = 17.4751 (6) Å
β = 98.752 (1)°
V = 5246.4 (3) Å³
Z = 4
Mo Kα radiation
μ = 0.07 mm⁻¹
T = 100 K
0.22 × 0.18 × 0.15 mm

Data collection

Bruker–Nonius KappaCCD diffractometer
11667 measured reflections
11660 independent reflections
10531 reflections with I > 2σ(I)
R _int = 0.040

Refinement

R[F ² > 2σ(F ²)] = 0.038
wR(F ²) = 0.087
S = 1.06
11660 reflections
651 parameters
2 restraints
H-atom parameters constrained
Δρ_max = 0.21 e Å⁻³
Δρ_min = −0.20 e Å⁻³
Absolute structure: Flack x determined using 4294 quotients [(I ⁺)−(I ⁻)]/[(I ⁺)+(I ⁻)] (Parsons et al., 2013 ▸)
Absolute structure parameter: −0.8 (8)

Data collection: COLLECT (Hooft, 2004 ▸); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997 ▸); data reduction: DENZO-SMN; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▸); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015 ▸); molecular graphics: DIAMOND (Brandenburg & Putz, 2005 ▸); software used to prepare material for publication: SHELXL2014.

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S2056989015023336/nr2062sup1.cif

e-71-o1045-sup1.cif^{(433.9KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989015023336/nr2062Isup2.hkl

e-71-o1045-Isup2.hkl^{(638.4KB, hkl)}

Click here for additional data file.^{(1.4MB, tif)}

. DOI: 10.1107/S2056989015023336/nr2062fig1.tif

The structure of the title compound with displacement ellipsoids at the 50% probability level. All carbon bonded hydrogen atoms were omitted for the sake of clarity.

Click here for additional data file.^{(1.3MB, tif)}

. DOI: 10.1107/S2056989015023336/nr2062fig2.tif

C—H⋯π interactions (brown dashed lines) between the hydrogen atoms of the guanidinium ion and the phenyl rings (centroids) of the tetraphenylborate ions.

CCDC reference: 822198

Additional supporting information: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

Cg1, Cg2 and Cg3 are the centroids of the C22–C27, C28–C33 and C58–C63 rings, respectively.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C4—H4B⋯Cg1	0.98	2.63	3.597 (2)	171
C4—H4A⋯Cg3	0.98	2.64	3.580 (2)	161
C11—H11A⋯Cg2	0.99	2.94	3.500 (2)	117
C13—H13B⋯Cg3	0.99	2.97	3.950 (2)	170

Open in a new tab

Acknowledgments

The authors thank Dr F. Lissner (Institut für Anorganische Chemie, Universität Stuttgart) for measuring the diffraction data.

supplementary crystallographic information

S1. Comment

ω-Aminoalkylguanidines like N''-[3-(dimethylamino)propyl]- N,N,N',N'-tetramethylguanidine (I) (Tiritiris & Kantlehner, 2012b), in which two nitrogen atoms with different basicity are present, are considered as ambident nucleophiles. Electrophiles can attack at both, on the imine nitrogen of the guanidine function, as well as on the nitrogen atom of the (dimethylamino)propyl group. By reaction of (I) with one equivalent N,N,N',N'- tetramethylchloroformamidinium chloride (Tiritiris & Kantlehner, 2008), the hygroscopic bisamidinium dichloride (II) was formed exclusively. As expected, the reaction occurred preferably at the imine nitrogen of the guanidine function because it is the most basic site. Two similar bisamidinium dichlorides are known in the literature. They where obtained by reaction of N,N,N',N'- tetramethylchloroformamidinium chloride (Tiritiris & Kantlehner, 2008) with N,N,N',N',N''-pentamethylguanidine or N-phenyl-N',N',N'',N''-tetramethylguanidine, respectively (Bauer et al., 1968). In our case, by anion exchange with sodium tetraphenylborate it was possible to obtain a stable, non-hygroscopic salt. The here presented crystal structure is the first structural study of a dicationic nonasubstituted bisamidinium salt. The asymmetric unit contains one twofold charged cation and two tetraphenylborate ions (Fig. 1). Prominent bond parameters in the bisamidinium ion are: N5–C6 = 1.388 (3) Å, N5–C1 = 1.407 (3) Å, N5–C11 = 1.506 (3) Å, indicating N–C single- and double-bond character of the central C₃N unit. The C–N–C angles are 117.51 (17)°, 118.92 (17)° and 123.16 (17)°, indicating a nearly ideal trigonal-planar surrounding of the central nitrogen atom N5 by the carbon atoms C1, C6 and C11. The carbon atoms C1 and C6 are further surrounded by the nitrogen atoms N1, N2, N3 and N4. Here, the C–N bonds show double-bond character and the bond lengths range from 1.319 (3) Å to 1.333 (3) Å. The N–C–N angles range from 118.24 (19)° to 121.87 (19)°, indicating again nearly ideal trigonal-planar surroundings of both carbon centres by the nitrogen atoms. The positive charges are delocalized in the planes N1/C1/N2, N3/C6/N4 and C1/N5/C6. The dihedral angle between the plane N1/C1/N2 and N3/C6/N4 is 70.5 (2)°. The bond lengths and angles in both tetraphenylborate ions are in good agreement with the data from the crystal structure analysis of the alkali metal tetraphenylborates (Behrens et al., 2012a). C–H···π interactions between the bisamidinium hydrogen atoms of –N(CH₃)₂ and –CH₂ groups and the phenyl carbon atoms [centroids: Cg1 = C22–C27, Cg2 = C28–C33 and Cg3 = C58–C63] of the tetraphenylborate ion are present (Fig. 2), ranging from 2.63 to 2.97 Å (Tab. 1). Such type of C–H···π interactions have been observed in tetraphenylborate salts with pentasubstituted or hexasubstituted guanidinium ions [for example: N,N,N',N'- tetramethyl-N''-[3-(trimethylazaniumyl)propyl]guanidinium bis(tetraphenylborate) acetone disolvate (Tiritiris, 2013a); N-[3-(Dimethylamino)propyl]- N,N',N',N'',N''- pentamethylguanidinium tetraphenylborate (Tiritiris, 2013b)]. The phenyl rings form aromatic pockets, in which the cation is embedded. This leads finally to the formation of a two-dimensional supramolecular pattern along the ab plane.

S2. Experimental

The title compound has been obtained by reaction of N''-[3-(dimethylamino)propyl]-N,N,N',N'-tetramethylguanidine (I) (Tiritiris & Kantlehner, 2012b) with one equivalent of N,N,N',N'- tetramethylchloroformamidinium chloride (Tiritiris & Kantlehner, 2008) in acetonitrile at room temperature. After evaporation of the solvent the crude N-[3-(dimethylamino)propyl]-N-(N,N,N',N'-tetramethyl-formamidinio)-N',N',N'',N''-tetramethyl-guanidinium dichloride (II) was washed with diethylether and dried in vacuo. 1.0 g (2.7 mmol) of (II) was dissolved in 20 ml acetonitrile and 1.83 g (5.4 mmol) of sodium tetraphenylborate in 20 ml acetonitrile were added. After stirring for one hour at room temperature, the precipitated sodium chloride was filtered off. The title compound crystallized from a saturated acetonitrile solution after a few months at 273 K, forming colorless single crystals. Yield: 2.15 g (84.9%).