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ISSN: 2056-9890

N-Cyclo­hexyl-3-methyl­benzamidine

aInstitute of Applied Chemistry, Shanxi University, Taiyuan 030006, People's Republic of China
*Correspondence e-mail: sdbai@sxu.edu.cn

(Received 18 February 2013; accepted 5 March 2013; online 9 March 2013)

The title amidine compound, C14H20N2, prepared by a one-pot reaction, is asymmetric as only one N atom has an alkyl substituent. The terminal cyclo­hexyl group connected to the amino N atom is located on the other side of the N—C—N skeleton to the 4-methylbenzene ring and has a chair conformation. The dihedral angle between the phenyl ring and the NCN plane is 47.87 (12)°. In the crystal, mol­ecules are linked via N—H⋯N hydrogen bonds, forming chains propagating along the a-axis direction.

Related literature

For reviews of related metal amidinates and their applications in olefin polymerization, see: Edelmann (1994[Edelmann, F. T. (1994). Coord. Chem. Rev. 137, 403-481.]); Barker & Kilner (1994[Barker, J. & Kilner, M. (1994). Coord. Chem. Rev. 133, 219-300.]); Collins (2011[Collins, S. (2011). Coord. Chem. Rev. 255, 118-138.]); Bai et al. (2010[Bai, S. D., Tong, H. B., Guo, J. P., Zhou, M. S., Liu, D. S. & Yuan, S. F. (2010). Polyhedron, 29, 262-269.]); Yang et al. (2013[Yang, Q. K., Zhou, M. S., Tong, H. B., Guo, D. L. & Liu, D. S. (2013). Inorg. Chem. Commun. 29, 1-3.]). For a review of neutral amidines, see: Coles (2006[Coles, M. P. (2006). Dalton Trans. pp. 985-1001.]). For a related synthetic method for amidines, see: Wang et al. (2008[Wang, J. F., Xu, F., Cai, T. & Shen, Q. (2008). Org. Lett. 10, 445-448.]). For related silyl-linked bis­(amidinate) ligands, see: Bai et al. (2006[Bai, S. D., Guo, J. P. & Liu, D. S. (2006). Dalton Trans. pp. 2244-2250.]).

[Scheme 1]

Experimental

Crystal data
  • C14H20N2

  • Mr = 216.32

  • Orthorhombic, P 21 21 21

  • a = 9.064 (2) Å

  • b = 11.417 (3) Å

  • c = 12.311 (3) Å

  • V = 1274.0 (5) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 0.07 mm−1

  • T = 200 K

  • 0.30 × 0.25 × 0.20 mm

Data collection
  • Bruker SMART CCD diffractometer

  • Absorption correction: multi-scan (SADABS; Sheldrick, 1996[Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.]) Tmin = 0.980, Tmax = 0.987

  • 7147 measured reflections

  • 2244 independent reflections

  • 1758 reflections with I > 2σ(I)

  • Rint = 0.042

Refinement
  • R[F2 > 2σ(F2)] = 0.040

  • wR(F2) = 0.098

  • S = 1.02

  • 2244 reflections

  • 154 parameters

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

  • Δρmax = 0.15 e Å−3

  • Δρmin = −0.12 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
N1—H1A⋯N2i 0.90 (2) 2.08 (2) 2.975 (2) 168.0 (18)
Symmetry code: (i) [x+{\script{1\over 2}}, -y+{\script{1\over 2}}, -z].

Data collection: SMART (Bruker, 2000[Bruker (2000). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2000[Bruker (2000). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); software used to prepare material for publication: SHELXL97.

Supporting information


Comment top

The exploration of ancillary ligand systems supporting catalytically active metal centers is a long–standing demand in the coordination chemistry. Amidinates represent an important class in the array comparable to the cyclopentadienyl system (Edelmann, 1994; Barker & Kilner, 1994; Collins, 2011). They are four–electron, monoanionic and N–donor bidentate chelates, demonstrating a great diversity by variation of substituents on the conjugated N—C—N backbone. Their steric and electronic properties are easily tunable to meet therequirements of different metal centers. In the course of extending amidinate chemistry, we explored a synthetic pathway to the silyl–linked bis(amidinate) ligands, [SiMe2{NC(Ph)N(R)}2]2- (Bai et al., 2006). They were applied to synthesize the Group 4 complexes, which were good catalysts for ethylene polymerization (Bai et al., 2010; Yang et al., 2013). Amidines are convenient precursors for both monoanionic amidinate ligands and bianionic ansa–bis(amidinate) ligands (Coles, 2006). Some amidines could be prepared by Yb complex catalyzed addtion reactions of aromatic amines and nitriles (Wang et al., 2008). Here, the synthesis and crystal structure of a new amidine will be described.

The title compound I was prepared by a one–pot reaction of cyclohexylamine, LiBu, m–tolunitrile and H2O. The intermediate process involved an addition reaction of lithium amide and nitrile to yield lithium monoamidinate. The suitable for X–ray investigation single–crystal of the title compound was obtained by recrystallization in CH2Cl2. Its molecular structure is shown in Fig. 1. Two N atoms connect the central C atom in different lengths of 1.357 (2)Å and 1.284 (2)Å, composing the characteristic N—C—N skeleton for amidine species. The terminal cyclohexyl with chair–like configuration connects the amino N atom. The phenyl group is attached to the central C atom. The angle between the phenyl plane and the [NCN] plane is 47.87 (12)°. Cyclohexyl and phenyl are in opposite directions. Fig. 2 displays the packing view of compound I. Molecules of I can form the one–dimensional chain extending along a–axis through the intermolecular hydrogen bond. The imino N atom is the acceptor for hydrogen atom. In the chain, every adjacent two molecules have C2 rotation symmetrical relationship with each other and the couple serves as the repeatable unit.

Related literature top

For reviews of related metal amidinates and their applications in olefin polymerization, see: Edelmann (1994); Barker & Kilner (1994); Collins (2011); Bai et al. (2010); Yang et al. (2013). For a review of neutral amidines, see: Coles (2006). For a related synthetic method for amidines, see: Wang et al. (2008). For related silyl-linked bis(amidinate) ligands, see: Bai et al. (2006).

Experimental top

A solution of LiBu (2.2 M, 2.7 ml, 6.0 mmol) in hexane was slowly added into a stirred solution of cyclohexylamine (0.69 ml, 6.0 mmol) in Et2O (ca 30 ml) by syringe at 273 K. The reaction mixture was warmed to room temperature and kept stirring for 3 h. Then m–tolunitrile (0.71 ml, 6.0 mmol) was added by syringe at 273 K. The reaction mixture was warmed to room temperature and kept stirring for 4 h. H2O (0.11 ml, 6.0 mmol) was added by syringe at 273 K. After stirred at room temperature for 4 h, the mixture was filtered and the filtrate was dried in vacuum to remove all volatiles. The residue was recrystallized with CH2Cl2 and gave colourless crystals of the title compound (yield 0.96 g, 74%). 1H NMR (300 MHz, CDCl3): δ = 7.38–7.25 (m, 4H; phenyl), 3.81 (br, 2H; NH), 2.43 (s, 3H; mMePh), 2.15–1.21 (m, 11H; Cy). 13C NMR (75 MHz, CDCl3): δ = 139.3–123.6 (Ph), 50.4 (mMePh), 33.8, 26.5, 25.6, 22.0 (Cy). Anal. Calc. for C14H20N2 (216.32): C, 77.73; H, 9.32; N, 12.95%. Found: C, 77.46; H, 9.22; N, 13.04%.

Refinement top

The methyl H atoms were constrained to an ideal geometry, with C—H distances of 0.98Å and Uiso(H) = 1.5Ueq(C), but each group was allowed to rotate freely about its C—C bond. The methylene H atoms were constrained with C—H distances of 0.99Å and Uiso(H) = 1.2Ueq(C). The methine H atom was constrained with C—H distance of 1.00Å and Uiso(H) = 1.2Ueq(C). The phenyl H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C—H distances in the range 0.95Å and Uiso(H) = 1.2Ueq(C).

The Flack parameter was omitted in CIF because no any atoms heavy Si.

Computing details top

Data collection: SMART (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT (Bruker, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The molecular structure, showing the atom–numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. H atoms are presented as a small spheres of arbitrary radius.
[Figure 2] Fig. 2. The view of one–dimensional chain in crystal structure of I. Symmetry codes: (i) x+1/2, -y+1/2, -z.
N-Cyclohexyl-3-methylbenzamidine top
Crystal data top
C14H20N2F(000) = 472
Mr = 216.32Dx = 1.128 Mg m3
Orthorhombic, P212121Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2abCell parameters from 1347 reflections
a = 9.064 (2) Åθ = 2.8–20.0°
b = 11.417 (3) ŵ = 0.07 mm1
c = 12.311 (3) ÅT = 200 K
V = 1274.0 (5) Å3Block, colourless
Z = 40.30 × 0.25 × 0.20 mm
Data collection top
Bruker SMART CCD
diffractometer
2244 independent reflections
Radiation source: fine–focus sealed tube1758 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.042
ϕ and ω scanθmax = 25.0°, θmin = 2.4°
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
h = 107
Tmin = 0.980, Tmax = 0.987k = 1312
7147 measured reflectionsl = 1414
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.040H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.098 w = 1/[σ2(Fo2) + (0.0452P)2 + 0.0788P]
where P = (Fo2 + 2Fc2)/3
S = 1.02(Δ/σ)max < 0.001
2244 reflectionsΔρmax = 0.15 e Å3
154 parametersΔρmin = 0.12 e Å3
0 restraintsExtinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.020 (3)
Crystal data top
C14H20N2V = 1274.0 (5) Å3
Mr = 216.32Z = 4
Orthorhombic, P212121Mo Kα radiation
a = 9.064 (2) ŵ = 0.07 mm1
b = 11.417 (3) ÅT = 200 K
c = 12.311 (3) Å0.30 × 0.25 × 0.20 mm
Data collection top
Bruker SMART CCD
diffractometer
2244 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
1758 reflections with I > 2σ(I)
Tmin = 0.980, Tmax = 0.987Rint = 0.042
7147 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0400 restraints
wR(F2) = 0.098H atoms treated by a mixture of independent and constrained refinement
S = 1.02Δρmax = 0.15 e Å3
2244 reflectionsΔρmin = 0.12 e Å3
154 parameters
Special details top

Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 (Å2) top
xyzUiso*/Ueq
N10.12298 (18)0.22773 (14)0.08238 (13)0.0434 (4)
N20.08387 (18)0.17325 (15)0.02421 (15)0.0475 (5)
C10.1003 (2)0.14588 (16)0.17183 (15)0.0391 (5)
H1B0.00790.14220.18720.047*
C20.1528 (2)0.02235 (17)0.14538 (16)0.0502 (6)
H2C0.09910.00730.08100.060*
H2D0.25930.02400.12770.060*
C30.1267 (3)0.05956 (17)0.24111 (18)0.0611 (7)
H3A0.01950.06560.25530.073*
H3B0.16380.13870.22280.073*
C40.2041 (3)0.0156 (2)0.34235 (18)0.0612 (7)
H4A0.31220.01700.33080.073*
H4B0.18090.06790.40420.073*
C50.1552 (3)0.10824 (19)0.36872 (17)0.0612 (6)
H5A0.21240.13760.43160.073*
H5B0.04960.10750.38940.073*
C60.1769 (2)0.19043 (17)0.27290 (16)0.0485 (5)
H6A0.13750.26870.29160.058*
H6B0.28370.19890.25810.058*
C70.0332 (2)0.23343 (16)0.00570 (16)0.0382 (5)
C80.0761 (2)0.32275 (16)0.08846 (16)0.0387 (5)
C90.1108 (2)0.43699 (16)0.05829 (17)0.0460 (5)
H9A0.11040.45870.01620.055*
C100.1457 (3)0.51857 (19)0.13683 (18)0.0559 (6)
H10A0.16830.59670.11620.067*
C110.1480 (3)0.48753 (19)0.24477 (19)0.0578 (6)
H11A0.17240.54460.29800.069*
C120.1153 (2)0.37453 (19)0.27700 (17)0.0520 (6)
C130.0782 (2)0.29362 (17)0.19718 (16)0.0446 (5)
H13A0.05360.21600.21810.054*
C140.1184 (3)0.3393 (2)0.3945 (2)0.0864 (9)
H14A0.09280.25620.40100.130*
H14B0.21740.35230.42400.130*
H14C0.04690.38640.43520.130*
H2A0.098 (2)0.1201 (17)0.0303 (17)0.054 (6)*
H1A0.213 (2)0.2603 (17)0.0752 (16)0.052 (6)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0400 (10)0.0501 (10)0.0401 (9)0.0084 (9)0.0028 (8)0.0139 (8)
N20.0419 (10)0.0512 (10)0.0495 (11)0.0071 (9)0.0050 (8)0.0109 (9)
C10.0377 (10)0.0413 (11)0.0384 (11)0.0025 (9)0.0019 (9)0.0065 (8)
C20.0573 (14)0.0481 (12)0.0451 (13)0.0004 (11)0.0039 (11)0.0022 (10)
C30.0705 (17)0.0405 (11)0.0721 (16)0.0032 (12)0.0081 (14)0.0079 (12)
C40.0729 (16)0.0571 (14)0.0536 (15)0.0025 (14)0.0025 (13)0.0189 (11)
C50.0785 (16)0.0640 (15)0.0410 (13)0.0052 (13)0.0004 (12)0.0068 (11)
C60.0565 (13)0.0438 (11)0.0450 (12)0.0025 (11)0.0040 (10)0.0009 (10)
C70.0364 (10)0.0379 (11)0.0402 (12)0.0025 (9)0.0009 (9)0.0016 (9)
C80.0342 (10)0.0392 (11)0.0427 (12)0.0062 (9)0.0006 (9)0.0042 (9)
C90.0502 (13)0.0430 (11)0.0448 (12)0.0024 (10)0.0028 (10)0.0033 (10)
C100.0701 (16)0.0387 (11)0.0590 (15)0.0026 (11)0.0040 (12)0.0082 (11)
C110.0638 (16)0.0524 (13)0.0570 (15)0.0022 (12)0.0016 (12)0.0212 (12)
C120.0552 (14)0.0590 (13)0.0418 (13)0.0052 (12)0.0000 (11)0.0089 (11)
C130.0460 (12)0.0448 (11)0.0431 (12)0.0012 (10)0.0011 (9)0.0006 (10)
C140.123 (2)0.0921 (19)0.0440 (14)0.0059 (19)0.0068 (16)0.0102 (14)
Geometric parameters (Å, º) top
N1—C71.357 (2)C5—H5B0.9900
N1—C11.459 (2)C6—H6A0.9900
N1—H1A0.90 (2)C6—H6B0.9900
N2—C71.284 (2)C7—C81.493 (3)
N2—H2A0.91 (2)C8—C131.379 (3)
C1—C61.513 (3)C8—C91.392 (3)
C1—C21.524 (3)C9—C101.379 (3)
C1—H1B1.0000C9—H9A0.9500
C2—C31.523 (3)C10—C111.375 (3)
C2—H2C0.9900C10—H10A0.9500
C2—H2D0.9900C11—C121.382 (3)
C3—C41.516 (3)C11—H11A0.9500
C3—H3A0.9900C12—C131.390 (3)
C3—H3B0.9900C12—C141.502 (3)
C4—C51.517 (3)C13—H13A0.9500
C4—H4A0.9900C14—H14A0.9800
C4—H4B0.9900C14—H14B0.9800
C5—C61.520 (3)C14—H14C0.9800
C5—H5A0.9900
C7—N1—C1123.32 (16)C1—C6—C5111.80 (17)
C7—N1—H1A116.5 (13)C1—C6—H6A109.3
C1—N1—H1A117.7 (13)C5—C6—H6A109.3
C7—N2—H2A110.1 (13)C1—C6—H6B109.3
N1—C1—C6109.93 (15)C5—C6—H6B109.3
N1—C1—C2112.82 (15)H6A—C6—H6B107.9
C6—C1—C2110.11 (16)N2—C7—N1127.70 (18)
N1—C1—H1B107.9N2—C7—C8117.35 (18)
C6—C1—H1B107.9N1—C7—C8114.94 (16)
C2—C1—H1B107.9C13—C8—C9118.79 (18)
C3—C2—C1110.77 (16)C13—C8—C7120.08 (17)
C3—C2—H2C109.5C9—C8—C7121.12 (18)
C1—C2—H2C109.5C10—C9—C8119.8 (2)
C3—C2—H2D109.5C10—C9—H9A120.1
C1—C2—H2D109.5C8—C9—H9A120.1
H2C—C2—H2D108.1C11—C10—C9120.4 (2)
C4—C3—C2111.18 (18)C11—C10—H10A119.8
C4—C3—H3A109.4C9—C10—H10A119.8
C2—C3—H3A109.4C10—C11—C12121.0 (2)
C4—C3—H3B109.4C10—C11—H11A119.5
C2—C3—H3B109.4C12—C11—H11A119.5
H3A—C3—H3B108.0C11—C12—C13118.0 (2)
C3—C4—C5110.44 (19)C11—C12—C14121.5 (2)
C3—C4—H4A109.6C13—C12—C14120.5 (2)
C5—C4—H4A109.6C8—C13—C12121.95 (19)
C3—C4—H4B109.6C8—C13—H13A119.0
C5—C4—H4B109.6C12—C13—H13A119.0
H4A—C4—H4B108.1C12—C14—H14A109.5
C4—C5—C6111.80 (18)C12—C14—H14B109.5
C4—C5—H5A109.3H14A—C14—H14B109.5
C6—C5—H5A109.3C12—C14—H14C109.5
C4—C5—H5B109.3H14A—C14—H14C109.5
C6—C5—H5B109.3H14B—C14—H14C109.5
H5A—C5—H5B107.9
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1A···N2i0.90 (2)2.08 (2)2.975 (2)168.0 (18)
Symmetry code: (i) x+1/2, y+1/2, z.

Experimental details

Crystal data
Chemical formulaC14H20N2
Mr216.32
Crystal system, space groupOrthorhombic, P212121
Temperature (K)200
a, b, c (Å)9.064 (2), 11.417 (3), 12.311 (3)
V3)1274.0 (5)
Z4
Radiation typeMo Kα
µ (mm1)0.07
Crystal size (mm)0.30 × 0.25 × 0.20
Data collection
DiffractometerBruker SMART CCD
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 1996)
Tmin, Tmax0.980, 0.987
No. of measured, independent and
observed [I > 2σ(I)] reflections
7147, 2244, 1758
Rint0.042
(sin θ/λ)max1)0.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.040, 0.098, 1.02
No. of reflections2244
No. of parameters154
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.15, 0.12

Computer programs: SMART (Bruker, 2000), SAINT (Bruker, 2000), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1A···N2i0.90 (2)2.08 (2)2.975 (2)168.0 (18)
Symmetry code: (i) x+1/2, y+1/2, z.
 

Acknowledgements

This work was supported by grants from the Natural Science Foundation of China (20702029) and the Natural Science Foundation of Shanxi Province (2008011024).

References

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