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organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Volume 69| Part 7| July 2013| Page o1101
https://doi.org/10.1107/S160053681301605X

(2S*,5R*)-2,5-Di­methyl-1,4-bis­­(pyridin-2-ylmeth­yl)piperazine

Christopher Goh,a Lilliana S. Morris,a Michael P. Girouard,a Tamuka Chidanguroa and Jerry P. Jasinskib*

aDepartment of Chemistry, Williams College, Williamstown, MA 01267, USA, and bDepartment of Chemistry, Keene State College, 229 Main Street, Keene, NH 03435-2001, USA
*Correspondence e-mail: jjasinski@keene.edu

(Received 29 May 2013; accepted 9 June 2013; online 15 June 2013)

The title compound, C18H24N4, resides on a crystallographic inversion centre, so that the asymmetric unit comprises one half-mol­ecule. The piperazine ring adopts a chair conformation, with the mean planes of the two equatorial pyridine rings parallel to each other and separated by 2.54 (3) Å. No classical hydrogen bonds are observed.

Related literature

For related work on the synthesis of tetra­dentate pyridine-piperazine ligands and for metal complexes of these ligands, see: Geiger et al. (2011[Geiger, R. A., Chattopadhyay, S., Day, V. W. & Jackson, T. A. (2011). Dalton Trans. 40, 1707-1715.]); Ostermeier et al. (2006[Ostermeier, M., Limberg, C. & Ziemer, B. (2006). Z. Anorg. Allg. Chem. 632, 1287-1292.], 2009[Ostermeier, M., Limberg, C., Herwig, C. & Ziemer, B. (2009). Z. Anorg. Allg. Chem. 635, 1823-1830.]); Nam (2007[Nam, W. (2007). Acc. Chem. Res. 40, 522-531.]); Huuskonen et al. (1995[Huuskonen, J., Schulz, J. & Rissanen, K. (1995). Liebigs Ann. pp. 1515-1519.]); Que & Tolman (2008[Que, L. & Tolman, W. B. (2008). Nature, 455, 333-339.]); Ratilainen et al. (1999[Ratilainen, J., Airola, K., Fröhlich, R., Nieger, M. & Rissanen, K. (1999). Polyhedron, 18, 2265-2273.]); Fuji et al. (1996[Fuji, K., Takasu, K., Miyamoto, H., Tanaka, K. & Taga, T. (1996). Tetrahedron Lett. 37, 7111-7114.]). For the synthesis, see: Halfen et al. (2000[Halfen, J. A., Uhan, J. M., Fox, D. C., Mehn, M. P. & Que, L. (2000). Inorg. Chem. 39, 4913-4920.]).

[Scheme 1]

Experimental

Crystal data

  • C18H24N4

  • Mr = 296.41

  • Orthorhombic, P b c a

  • a = 9.4097 (5) Å

  • b = 9.2191 (5) Å

  • c = 18.7473 (9) Å

  • V = 1626.29 (14) Å3

  • Z = 4

  • Cu Kα radiation

  • μ = 0.57 mm−1

  • T = 173 K

  • 0.22 × 0.18 × 0.04 mm
Data collection

  • Agilent Xcalibur (Eos, Gemini) diffractometer

  • Absorption correction: multi-scan (CrysAlis PRO and CrysAlis RED; Agilent, 2012[Agilent (2012). CrysAlis PRO and CrysAlis RED. Agilent Technologies, Yarnton, England.]) Tmin = 0.817, Tmax = 1.000

  • 10101 measured reflections

  • 1545 independent reflections

  • 1392 reflections with I > 2σ(I)

  • Rint = 0.064
Refinement

  • R[F2 > 2σ(F2)] = 0.044

  • wR(F2) = 0.131

  • S = 1.07

  • 1545 reflections

  • 102 parameters

  • H-atom parameters constrained

  • Δρmax = 0.24 e Å−3

  • Δρmin = −0.19 e Å−3

Data collection: CrysAlis PRO (Agilent, 2012[Agilent (2012). CrysAlis PRO and CrysAlis RED. Agilent Technologies, Yarnton, England.]); cell refinement: CrysAlis PRO; data reduction: CrysAlis RED (Agilent, 2012[Agilent (2012). CrysAlis PRO and CrysAlis RED. Agilent Technologies, Yarnton, England.]); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL2012 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: OLEX2 (Dolomanov et al., 2009[Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339-341.]); software used to prepare material for publication: OLEX2.

Supporting information

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S160053681301605X/fj2633sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S160053681301605X/fj2633Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S160053681301605X/fj2633Isup3.cml

checkCIF report


Comment top

Multidentate ligands containing pyridine and amine donor moieties have applications in metal-catalyzed oxidations and in the design of macrocyclic metal-binding receptors. Examples include the manganese, iron, and copper complexes of tetradentate pyridine and amine ligands for biologically-inspired oxidations (Geiger et al., 2011; Ostermeier et al., 2009; Que et al., 2008; Nam, 2007; Ostermeier et al., 2006), copper complexes of pyridine-diazacycloalkanes as catalysts for the aziridination of alkenes (Halfen et al., 2000) and macrocyclic piperazinacyclophanes as complexation agents for a host of metals (Ratilainen et al., 1999; Fuji et al., 1996; Huuskonen et al., 1995). Our group has been interested in the use of neutral tetradentate hetero-aromatic-amine ligands in metal-catalyzed oxidations. Here we report the synthesis and crystal structure of the meso form of the tetradentate ligand, (I), (2S,5R)-2,5-dimethyl-1,4-bis(pyridin-2-ylmethyl)piperazine (Fig. 1).

In the asymmetric unit of the title compound, C18H24N4, (I), a piperazine ring (N1/C2/C3A/N1A/C2A/C3) is formed by a center of symmetry connecting each half (N/C/C) to a methyl group and pyridine ring at the 2,5 and 1,4 positions, respectively. The piperazine ring adopts a chair conformation with puckering parameters Q = 0.5804 (13)Å, θ = 0.00 (1)°, φ = 0.0000°. The mean planes of the two equatorial pyridine rings are parallel to each other and separated by 2.54 (3)Å, respectively. In the formation of this neutral tetradentate hetero-aromatic-amine ligand no classical hydrogen bonds are observed (Fig. 2).

Related literature top

For related work on the synthesis of tetradentate pyridine-piperazine ligands and for metal complexes of these ligands, see: Geiger et al. (2011); Ostermeier et al. (2006, 2009); Nam (2007); Huuskonen et al. (1995); Que & Tolman (2008); Ratilainen et al. (1999); Fuji et al. (1996). For the synthesis, see: Halfen et al. (2000).

Experimental top

The title compound was synthesized under a dinitrogen atmosphere by modifications of a previously published protocol (Halfen et al., 2000). 2-picolyl chloride hydrochloride (2.87 g, 17.5 mmol) and triethylamine (4.88 mL, 35.0 mmol) were added to a suspension of (2R, 5S)-2,5-dimethylpiperazine (1.00 g, 8.76 mmol) in 30 mL of acetonitrile to form a slurry. The mixture was allowed to stir for 48 hours at room temperature and then treated with 100 mL of 1 M sodium hydroxide. The product was extracted with three portions of 50 mL of CH2Cl2. The combined fractions were dried with MgSO4, filtered and the solvent removed to yield the crude product as a brown solid. Further purification by column chromatography with a Biotage IsoleraTM Flash Purification System using a silica cartridge and a gradient of ethyl acetate and a mixture of ethyl acetate/methanol/triethylamine (90/5/5), followed by solvent removal yielded the pure product as a faintly brown transparent solid (1.40 g, 54% yield). Crystallization by evaporation from a concentrated diethyl ether solution led to isolation of crystals suitable for X-ray analysis (m.p.: 405–406K).

Refinement top

All of the H atoms were placed in their calculated positions and then refined using the riding model with Atom—H lengths of 0.95Å (CH), 0.99Å (CH2) or 0.98Å (CH3). Isotropic displacement parameters for these atoms were set to 1.2 (CH, CH2) or 1.5 (CH3times Ueq of the parent atom. Ternary CH were refined with riding coordinates: C2(H2), secondary CH2 refined with riding coordinates: C3(H3A,H3B), C4(H4A,H4B), aromatic/amide H refined with riding coordinates: C6(H6), C7(H7), C8(H8), C9(H9), idealised Me refined as rotating group: C1(H1A,H1B,H1C).

Structure description top

Multidentate ligands containing pyridine and amine donor moieties have applications in metal-catalyzed oxidations and in the design of macrocyclic metal-binding receptors. Examples include the manganese, iron, and copper complexes of tetradentate pyridine and amine ligands for biologically-inspired oxidations (Geiger et al., 2011; Ostermeier et al., 2009; Que et al., 2008; Nam, 2007; Ostermeier et al., 2006), copper complexes of pyridine-diazacycloalkanes as catalysts for the aziridination of alkenes (Halfen et al., 2000) and macrocyclic piperazinacyclophanes as complexation agents for a host of metals (Ratilainen et al., 1999; Fuji et al., 1996; Huuskonen et al., 1995). Our group has been interested in the use of neutral tetradentate hetero-aromatic-amine ligands in metal-catalyzed oxidations. Here we report the synthesis and crystal structure of the meso form of the tetradentate ligand, (I), (2S,5R)-2,5-dimethyl-1,4-bis(pyridin-2-ylmethyl)piperazine (Fig. 1).

In the asymmetric unit of the title compound, C18H24N4, (I), a piperazine ring (N1/C2/C3A/N1A/C2A/C3) is formed by a center of symmetry connecting each half (N/C/C) to a methyl group and pyridine ring at the 2,5 and 1,4 positions, respectively. The piperazine ring adopts a chair conformation with puckering parameters Q = 0.5804 (13)Å, θ = 0.00 (1)°, φ = 0.0000°. The mean planes of the two equatorial pyridine rings are parallel to each other and separated by 2.54 (3)Å, respectively. In the formation of this neutral tetradentate hetero-aromatic-amine ligand no classical hydrogen bonds are observed (Fig. 2).

For related work on the synthesis of tetradentate pyridine-piperazine ligands and for metal complexes of these ligands, see: Geiger et al. (2011); Ostermeier et al. (2006, 2009); Nam (2007); Huuskonen et al. (1995); Que & Tolman (2008); Ratilainen et al. (1999); Fuji et al. (1996). For the synthesis, see: Halfen et al. (2000).

Computing details top

Data collection: CrysAlis PRO (Agilent, 2012); cell refinement: CrysAlis PRO (Agilent, 2012); data reduction: CrysAlis RED (Agilent, 2012); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2012 (Sheldrick, 2008); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

Figures top
[Figure 1] Fig. 1. Molecular structure of the title compound showing the atom labeling scheme and 30% probability displacement ellipsoids.
[Figure 2] Fig. 2. Packing diagram of the title compound viewed along the b axis. H atoms have been removed for clarity.
(2S*,5R*)-2,5-Dimethyl-1,4-bis(pyridin-2-ylmethyl)piperazine top
Crystal data top
C18H24N4Dx = 1.211 Mg m−3
Mr = 296.41Cu Kα radiation, λ = 1.5418 Å
Orthorhombic, PbcaCell parameters from 4359 reflections
a = 9.4097 (5) Åθ = 4.7–70.6°
b = 9.2191 (5) ŵ = 0.57 mm−1
c = 18.7473 (9) ÅT = 173 K
V = 1626.29 (14) Å3Block, colourless
Z = 40.22 × 0.18 × 0.04 mm
F(000) = 640
Data collection top
Agilent Xcalibur (Eos, Gemini)
diffractometer		1545 independent reflections
Radiation source: Enhance (Cu) X-ray Source1392 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.064
Detector resolution: 16.0416 pixels mm-1θmax = 70.7°, θmin = 6.7°
ω scansh = −10→11
Absorption correction: multi-scan
(CrysAlis PRO and CrysAlis RED; Agilent, 2012)		k = −8→11
Tmin = 0.817, Tmax = 1.000l = −22→21
10101 measured reflections
Refinement top
Refinement on F2Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: fullH-atom parameters constrained
R[F2 > 2σ(F2)] = 0.044 w = 1/[σ2(Fo2) + (0.0744P)2 + 0.3744P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.131(Δ/σ)max < 0.001
S = 1.07Δρmax = 0.24 e Å−3
1545 reflectionsΔρmin = −0.19 e Å−3
102 parametersExtinction correction: SHELXL2012 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 0.0056 (9)
Primary atom site location: structure-invariant direct methods
Crystal data top
C18H24N4V = 1626.29 (14) Å3
Mr = 296.41Z = 4
Orthorhombic, PbcaCu Kα radiation
a = 9.4097 (5) ŵ = 0.57 mm−1
b = 9.2191 (5) ÅT = 173 K
c = 18.7473 (9) Å0.22 × 0.18 × 0.04 mm
Data collection top
Agilent Xcalibur (Eos, Gemini)
diffractometer		1545 independent reflections
Absorption correction: multi-scan
(CrysAlis PRO and CrysAlis RED; Agilent, 2012)		1392 reflections with I > 2σ(I)
Tmin = 0.817, Tmax = 1.000Rint = 0.064
10101 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0440 restraints
wR(F2) = 0.131H-atom parameters constrained
S = 1.07Δρmax = 0.24 e Å−3
1545 reflectionsΔρmin = −0.19 e Å−3
102 parameters
Special details top

Experimental. 1H-NMR (CDCl3, 298 K): δ 8.55 (d, J = 3.5 Hz, 2H, py), 7.65 (m, 2H, py), 7.44 (d, J = 7.5 Hz, 2H, py), 7.15 (m, 2H, py), 4.15 (d, J = 14 Hz, 2 H, py-CH2N), 3.38 (d, J = 14 Hz, 2H, py-CH2N), 2.68 (m, 2H, NCH2), 2.50 (m, 2H, NCH), 2.14 (m, 2H, NCH2), 1.07 (d, J = 6.1 Hz, 6H, CH3) ppm. 13C-NMR (CDCl3, 298K): δ 159.6 (py), 150.0 (py), 136.3 (py), 123.2 (py), 121.8 (py), 60.5, 59.7, 56.0, 17.8 (CH3) ppm. MS: m/z 204 (py-CH2N2C6H12), m/z 175 (py-CH2NC5H9), m/z 149 (py-CH2NC3H7), m/z 135.0 (py-CH2NC2H4), m/z 112 (N2C6H12), m/z 93 (py-CH3).

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N10.35844 (11)0.53852 (12)0.52226 (5)0.0296 (3)
N20.05342 (13)0.49301 (14)0.64052 (7)0.0433 (4)
C10.31099 (16)0.64089 (18)0.40179 (8)0.0431 (4)
H1A0.32270.73800.42220.065*
H1B0.21000.61480.40180.065*
H1C0.34690.64030.35270.065*
C20.39382 (14)0.53155 (14)0.44625 (7)0.0309 (4)
H20.37400.43160.42810.037*
C30.44872 (13)0.43666 (15)0.56137 (7)0.0316 (4)
H3A0.42970.33720.54390.038*
H3B0.42300.43990.61260.038*
C40.20889 (13)0.50891 (17)0.53835 (7)0.0352 (4)
H4A0.19070.40360.53330.042*
H4B0.14820.56040.50340.042*
C50.16893 (14)0.55639 (15)0.61287 (7)0.0319 (3)
C60.24476 (15)0.66281 (16)0.64872 (7)0.0339 (4)
H60.32630.70570.62750.041*
C70.20015 (15)0.70565 (18)0.71574 (7)0.0411 (4)
H70.25080.77790.74140.049*
C80.08112 (17)0.64193 (19)0.74468 (8)0.0476 (4)
H80.04760.66930.79050.057*
C90.01202 (18)0.53765 (18)0.70546 (9)0.0507 (5)
H9−0.07040.49430.72560.061*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0247 (6)0.0370 (6)0.0270 (6)0.0004 (4)0.0020 (4)0.0000 (4)
N20.0353 (7)0.0432 (7)0.0513 (8)−0.0014 (5)0.0150 (5)−0.0023 (6)
C10.0377 (8)0.0577 (10)0.0340 (7)0.0097 (7)0.0010 (6)0.0065 (6)
C20.0296 (7)0.0365 (7)0.0266 (7)0.0013 (5)0.0006 (5)−0.0020 (5)
C30.0315 (7)0.0345 (7)0.0288 (7)−0.0004 (5)0.0043 (5)0.0021 (5)
C40.0268 (7)0.0452 (8)0.0335 (7)−0.0029 (5)0.0015 (5)−0.0039 (6)
C50.0253 (6)0.0356 (7)0.0347 (7)0.0050 (5)0.0028 (5)0.0033 (5)
C60.0279 (7)0.0420 (8)0.0317 (7)0.0033 (5)−0.0001 (5)0.0019 (5)
C70.0380 (8)0.0503 (9)0.0349 (7)0.0098 (6)−0.0043 (6)−0.0040 (6)
C80.0485 (9)0.0590 (10)0.0353 (8)0.0155 (7)0.0111 (6)0.0009 (7)
C90.0447 (9)0.0509 (10)0.0566 (10)0.0024 (7)0.0245 (8)0.0042 (8)
Geometric parameters (Å, º) top
N1—C21.4648 (16)C3—H3B0.9900
N1—C31.4633 (17)C4—H4A0.9900
N1—C41.4649 (17)C4—H4B0.9900
N2—C51.3385 (18)C4—C51.5115 (18)
N2—C91.343 (2)C5—C61.387 (2)
C1—H1A0.9800C6—H60.9500
C1—H1B0.9800C6—C71.3824 (19)
C1—H1C0.9800C7—H70.9500
C1—C21.5226 (19)C7—C81.376 (2)
C2—H21.0000C8—H80.9500
C2—C3i1.5171 (17)C8—C91.374 (3)
C3—C2i1.5171 (17)C9—H90.9500
C3—H3A0.9900
C2—N1—C4114.24 (10)N1—C4—H4A109.2
C3—N1—C2109.11 (10)N1—C4—H4B109.2
C3—N1—C4109.57 (10)N1—C4—C5112.04 (11)
C5—N2—C9116.93 (14)H4A—C4—H4B107.9
H1A—C1—H1B109.5C5—C4—H4A109.2
H1A—C1—H1C109.5C5—C4—H4B109.2
H1B—C1—H1C109.5N2—C5—C4115.69 (12)
C2—C1—H1A109.5N2—C5—C6122.62 (13)
C2—C1—H1B109.5C6—C5—C4121.65 (12)
C2—C1—H1C109.5C5—C6—H6120.4
N1—C2—C1112.78 (11)C7—C6—C5119.10 (13)
N1—C2—H2109.2C7—C6—H6120.4
N1—C2—C3i107.77 (10)C6—C7—H7120.5
C1—C2—H2109.2C8—C7—C6118.91 (14)
C3i—C2—C1108.69 (11)C8—C7—H7120.5
C3i—C2—H2109.2C7—C8—H8120.9
N1—C3—C2i113.32 (11)C9—C8—C7118.22 (14)
N1—C3—H3A108.9C9—C8—H8120.9
N1—C3—H3B108.9N2—C9—C8124.22 (15)
C2i—C3—H3A108.9N2—C9—H9117.9
C2i—C3—H3B108.9C8—C9—H9117.9
H3A—C3—H3B107.7
N1—C4—C5—N2−158.76 (12)C4—N1—C2—C3i−179.58 (11)
N1—C4—C5—C623.55 (18)C4—N1—C3—C2i−174.32 (11)
N2—C5—C6—C70.1 (2)C4—C5—C6—C7177.62 (12)
C2—N1—C3—C2i59.93 (15)C5—N2—C9—C8−0.6 (3)
C2—N1—C4—C5−164.47 (11)C5—C6—C7—C8−0.4 (2)
C3—N1—C2—C1−176.54 (12)C6—C7—C8—C90.2 (2)
C3—N1—C2—C3i−56.57 (14)C7—C8—C9—N20.3 (3)
C3—N1—C4—C572.78 (14)C9—N2—C5—C4−177.26 (13)
C4—N1—C2—C160.45 (15)C9—N2—C5—C60.4 (2)
Symmetry code: (i) −x+1, −y+1, −z+1.

Experimental details

Crystal data
Chemical formulaC18H24N4
Mr296.41
Crystal system, space groupOrthorhombic, Pbca
Temperature (K)173
a, b, c (Å)9.4097 (5), 9.2191 (5), 18.7473 (9)
V (Å3)1626.29 (14)
Z4
Radiation typeCu Kα
µ (mm−1)0.57
Crystal size (mm)0.22 × 0.18 × 0.04
Data collection
DiffractometerAgilent Xcalibur (Eos, Gemini)
Absorption correctionMulti-scan
(CrysAlis PRO and CrysAlis RED; Agilent, 2012)
Tmin, Tmax0.817, 1.000
No. of measured, independent and
observed [I > 2σ(I)] reflections		10101, 1545, 1392
Rint0.064
(sin θ/λ)max (Å−1)0.612
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.044, 0.131, 1.07
No. of reflections1545
No. of parameters102
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å−3)0.24, −0.19

Computer programs: CrysAlis PRO (Agilent, 2012), CrysAlis RED (Agilent, 2012), SHELXS97 (Sheldrick, 2008), SHELXL2012 (Sheldrick, 2008), OLEX2 (Dolomanov et al., 2009).

 

Acknowledgements

CG acknowledges the Donors of the American Chemical Society Petroleum Research Fund for support of this research. JPJ acknowledges the NSF–MRI program (grant No. CHE-1039027) for funds to purchase the X-ray diffractometer.

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Journal logoCRYSTALLOGRAPHIC
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ISSN: 2056-9890
Volume 69| Part 7| July 2013| Page o1101
https://doi.org/10.1107/S160053681301605X
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