rac-2,2′-Bipiperidine-1,1′-diium dibromide

Abstract

In the title compound, C₁₀H₂₂N₂ ²⁺·2Br⁻, a precursor in the synthesis of organocatalysts, the bipiperidinium ion is located on a twofold rotation axis which passes through the mid-point of the central C—C bond. The piperidinium ring adopts a chair conformation. In the crystal, the cations are linked together by Br⁻ ions through N—H⋯Br hydrogen bonds, forming layers parallel to the ab plane.

Related literature

For the synthesis, see: Krumholz (1953 ▶); Herrmann et al. (2006 ▶). For the application of N-substituted enanti­opure derivatives of the title compound in organocatalysis, see: Laars et al. (2008 ▶). For details of the Cu^II–catalysed Henry reaction, see: Noole et al. (2010 ▶). For related structures, see: Sato et al. (1982 ▶); Baran et al. (1992a ▶,b ▶); Intini et al. (2008 ▶).

Experimental

Crystal data

• C₁₀H₂₂N₂ ²⁺·2Br⁻

• M _r = 330.12

• Monoclinic,

• a = 11.789 (2) Å

• b = 10.6403 (18) Å

• c = 11.6632 (17) Å

• β = 107.687 (5)°

• V = 1393.9 (4) ų

• Z = 4

• Mo Kα radiation

• μ = 5.79 mm⁻¹

• T = 300 K

• 0.40 × 0.30 × 0.20 mm

Data collection

• Bruker SMART X2S diffractometer

• Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ▶) T _min = 0.151, T _max = 0.391

• 4225 measured reflections

• 1225 independent reflections

• 1012 reflections with I > 2σ(I)

• R _int = 0.068

Refinement

• R[F ² > 2σ(F ²)] = 0.038

• wR(F ²) = 0.093

• S = 1.08

• 1224 reflections

• 70 parameters

• H atoms treated by a mixture of independent and constrained refinement

• Δρ_max = 0.47 e Å⁻³

• Δρ_min = −0.94 e Å⁻³

Data collection: GIS (Bruker, 2010 ▶); cell refinement: SAINT (Bruker, 2009 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: Mercury (Macrae et al., 2006 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Supplementary material file. DOI: 10.1107/S1600536811016084/is2700Isup3.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

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

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1NA⋯Br1i	0.95 (4)	2.36 (4)	3.293 (3)	168 (3)
N1—H1NB⋯Br1ii	0.92 (4)	2.34 (4)	3.228 (3)	162 (3)

Symmetry codes: (i) ; (ii) .

supplementary crystallographic information

Comment

N-substituted, enantiopure derivatives of the title phase, rac-2,2'-bipiperidine-1,1'-diium dibromide (I), catalyse stereoselectively both aldol reactions (Laars et al., 2008) and, in the form of their Cu^II–complexes, Henry (nitro-aldol) reactions (Noole et al., 2010).

Owing to the twofold axis, passing the centre of the bond C1—C1ⁱ (Fig. 1), Z'=0.5. Bond lengths and bond angles in the salt are normal. The piperidinium rings adopt chair conformation, with their least-squares planes (defined by their carbon and nitrogen atoms) twisted by about 77° against each other. Parallel to the (0 0 1) plane, the structure is made up of layers with a repeating distance of d₀₀₁/2 of cations, which are hydrogen-bound via bromide ions (Fig. 2).

Experimental

Single crystals of (I) were prepared from 2,2'-bipiperidine (Krumholz, 1953) according to Herrmann et al. (2006).

Refinement

Except for the protonic H atoms H1NA and H1NB, whose positions were refined freely, H atoms were included at calculated positions [d(C—H) = 0.97 (CH₂) or 0.98 Å (CH)] and treated as riding on their base atoms. For all H atoms, U_iso(H) values were set at 1.2U_eq(C or N). The 6 8 10 reflection was excluded from the refinement due to its large Δ(F²)/esd value.

Figures

Fig. 1.

Cationic moiety in the crystal structure of the title compound together with the bromide ions bound to it through N—H···Br hydrogen bonds. Displacement ellipsoids for non–H atoms are drawn at the 50% probability level. Orange dashed lines indicate the hydrogen bonds. Symmetry codes: (i) -x, y, 1/2 - z; (ii) 1/2-x, 1/2 - y, 1 - z; (iii) x, -y, -1/2 + z; (iv) -1/2 + x, 1/2 - y, -1/2 + z; (v) -x, -y, 1 - z.

Fig. 2.

Packing diagram of the title compound. Orange dashed lines indicate N—H···Br hydrogen bonds. H atoms not involved in the hydrogen bonds have been omitted for clarity.

Crystal data

C10H22N22+·2Br−	F(000) = 664
Mr = 330.12	Dx = 1.573 Mg m−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 1621 reflections
a = 11.789 (2) Å	θ = 2.6–24.9°
b = 10.6403 (18) Å	µ = 5.79 mm−1
c = 11.6632 (17) Å	T = 300 K
β = 107.687 (5)°	Prism, colourless
V = 1393.9 (4) Å3	0.40 × 0.30 × 0.20 mm
Z = 4

Data collection

Bruker SMART X2S diffractometer	1225 independent reflections
Radiation source: XOS X-beam microfocus source	1012 reflections with I > 2σ(I)
doubly curved silicon crystal	Rint = 0.068
ω scans	θmax = 25.0°, θmin = 2.6°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −13→14
Tmin = 0.151, Tmax = 0.391	k = −12→12
4225 measured reflections	l = −13→13

Refinement

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.038	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.093	H atoms treated by a mixture of independent and constrained refinement
S = 1.08	w = 1/[σ2(Fo2) + (0.P)2 + 0.0285P] where P = (Fo2 + 2Fc2)/3
1224 reflections	(Δ/σ)max < 0.001
70 parameters	Δρmax = 0.47 e Å−3
0 restraints	Δρmin = −0.94 e Å−3

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 F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 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 (Ų)

	x	y	z	Uiso*/Ueq
Br1	0.19514 (3)	0.07309 (4)	0.77393 (4)	0.0429 (2)
N1	0.1066 (3)	0.1990 (3)	0.1590 (3)	0.0319 (7)
H1NA	0.156 (3)	0.271 (4)	0.183 (3)	0.038*
H1NB	0.146 (3)	0.132 (4)	0.202 (4)	0.038*
C1	−0.0106 (3)	0.2219 (3)	0.1814 (3)	0.0287 (8)
H1	−0.0630	0.1510	0.1473	0.034*
C2	−0.0661 (3)	0.3394 (4)	0.1136 (3)	0.0385 (9)
H2A	−0.1423	0.3553	0.1265	0.046*
H2B	−0.0148	0.4111	0.1438	0.046*
C3	−0.0836 (4)	0.3232 (5)	−0.0213 (4)	0.0524 (11)
H3A	−0.1393	0.2553	−0.0526	0.063*
H3B	−0.1169	0.3997	−0.0635	0.063*
C4	0.0349 (4)	0.2940 (4)	−0.0433 (3)	0.0489 (11)
H4A	0.0213	0.2782	−0.1284	0.059*
H4B	0.0872	0.3662	−0.0208	0.059*
C5	0.0944 (4)	0.1811 (4)	0.0280 (4)	0.0442 (10)
H5A	0.0474	0.1064	−0.0017	0.053*
H5B	0.1725	0.1694	0.0182	0.053*

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
Br1	0.0502 (3)	0.0283 (3)	0.0495 (4)	−0.01100 (16)	0.0142 (3)	−0.00332 (18)
N1	0.0415 (17)	0.0201 (16)	0.0361 (19)	0.0024 (14)	0.0146 (16)	0.0033 (15)
C1	0.0344 (18)	0.0208 (18)	0.031 (2)	−0.0017 (15)	0.0101 (16)	−0.0031 (17)
C2	0.042 (2)	0.034 (2)	0.037 (2)	0.0072 (18)	0.0088 (19)	0.0033 (19)
C3	0.069 (3)	0.053 (3)	0.029 (2)	0.006 (2)	0.005 (2)	0.004 (2)
C4	0.075 (3)	0.044 (3)	0.031 (2)	−0.004 (2)	0.020 (2)	0.000 (2)
C5	0.068 (3)	0.033 (2)	0.040 (2)	−0.006 (2)	0.030 (2)	−0.012 (2)

Geometric parameters (Å, °)

N1—C1	1.501 (4)	C2—H2A	0.9700
N1—C5	1.503 (5)	C3—C4	1.528 (5)
N1—H1NB	0.92 (4)	C3—H3A	0.9700
N1—H1NA	0.95 (4)	C3—H3B	0.9700
C1—C2	1.517 (5)	C4—C5	1.508 (6)
C1—C1i	1.542 (6)	C4—H4A	0.9700
C1—H1	0.9800	C4—H4B	0.9700
C2—C3	1.533 (5)	C5—H5A	0.9700
C2—H2B	0.9700	C5—H5B	0.9700
C1—N1—C5	112.9 (3)	C4—C3—C2	110.5 (3)
C1—N1—H1NB	112 (2)	C4—C3—H3A	109.5
C5—N1—H1NB	110 (2)	C2—C3—H3A	109.5
C1—N1—H1NA	109 (2)	C4—C3—H3B	109.5
C5—N1—H1NA	106 (2)	C2—C3—H3B	109.5
H1NB—N1—H1NA	107 (3)	H3A—C3—H3B	108.1
N1—C1—C2	108.5 (3)	C5—C4—C3	111.4 (3)
N1—C1—C1i	108.3 (3)	C5—C4—H4A	109.3
C2—C1—C1i	116.7 (2)	C3—C4—H4A	109.3
N1—C1—H1	107.7	C5—C4—H4B	109.3
C2—C1—H1	107.7	C3—C4—H4B	109.3
C1i—C1—H1	107.7	H4A—C4—H4B	108.0
C1—C2—C3	110.2 (3)	N1—C5—C4	110.2 (3)
C1—C2—H2B	109.6	N1—C5—H5A	109.6
C3—C2—H2B	109.6	C4—C5—H5A	109.6
C1—C2—H2A	109.6	N1—C5—H5B	109.6
C3—C2—H2A	109.6	C4—C5—H5B	109.6
H2B—C2—H2A	108.1	H5A—C5—H5B	108.1

Symmetry codes: (i) −x, y, −z+1/2.

Hydrogen-bond geometry (Å, °)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1NA···Br1ii	0.95 (4)	2.36 (4)	3.293 (3)	168 (3)
N1—H1NB···Br1iii	0.92 (4)	2.34 (4)	3.228 (3)	162 (3)

Symmetry codes: (ii) −x+1/2, −y+1/2, −z+1; (iii) x, −y, z−1/2.