N,N'-Bis­(salicyl­idene)-1-4-butane­di­amine

During our studies on the synthesis and structure of simple Schiff base complexes of zinc, we retrieved from the mother liquors a crystalline sample of N,N'-bis­(salicyl­idene)-1,4-butane­di­amine, C₁₈H₂₀N₂O₂. Its structure was determined and is reported here.

Key indicators

• Single-crystal X-ray study
• T = 123 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.063
• wR factor = 0.106
• Data-to-parameter ratio = 9.6

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level C:



WEIGH_01  Alert C Extra text has been found in the
          _refine_ls_weighting_scheme field. This should be in the
          _refine_ls_weighting_details field.
          Weighting scheme given as calc w = 1/[\s^2^(Fo^2^)+(0.0434P)^2^+0.154
          Weighting scheme identified as calc

General Notes



GOODF_01  _refine_ls_goodness_of_fit_obs is an old dataname which has
          been superseded by _refine_ls_goodness_of_fit_ref

REFLE_01  _reflns_observed_criterion is an old dataname which has been
          superseded by _reflns_threshold_expression

REFLG_01  _reflns_number_observed is an old dataname which has been
          superseded by _reflns_number_gt

RFACG_01  _refine_ls_R_factor_obs is an old dataname which has been
          superseded by _refine_ls_R_factor_gt

RFACR_01  _refine_ls_wR_factor_obs is an old dataname which has been
          superseded by _refine_ls_wR_factor_ref

SHFSU_01  _refine_ls_shift/esd_max is an old dataname which has been
          superseded by _refine_ls_shift/su_max


 0 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 1 Alert Level C = Please check

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S1. Comment

During our studies on the synthesis and structure of simple Schiff base complexes of zinc, we retrieved from the mother liquors a crystalline sample of N,N'-bis(salicylidene)-1,4-butanediamine (Pfeiffer et al., 1937) (m. p. 362 K). Although this compound has been known for some time, its structure remains unreported. As a consequence of our current interest in Schiff base complexes with larger diimide backbones and the fact the analogous 1,2-ethylenediamine (Pahor et al., 1978) and 1,3-propylenediamine (Elderman et al., 1991) structures are known, we formed the opinion that it would be instructive to solve and report the structure of this higher homologue.

S2. Refinement

All H atoms were found in the difference synthesese and refined isotropically.

Computing details

Data collection: DENZO (Otwinowski & Minor, 1997) and COLLECT (Hooft, 1988); cell refinement: DENZO and COLLECT; data reduction: DENZO and COLLECT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL93 (Sheldrick, 1993); molecular graphics: ORTEPII (Johnson 1976); software used to prepare material for publication: SHELXL93.

Figures

Fig. 1. ORTEPII view of (I) with the non-H atoms drawn as 50% probability ellipsoids.

N,N'-bis(salicylidene)-1,4,butanediamine

Crystal data

C18H20N2O2	F(000) = 316
Mr = 296.36	Dx = 1.254 Mg m^−3
Monoclinic, P21/a	Mo Kα radiation, λ = 0.71073 Å
a = 8.7330 (2) Å	Cell parameters from 22914 reflections
b = 5.8710 (3) Å	θ = 0.3–25.0°
c = 15.3070 (6) Å	µ = 0.08 mm^−1
β = 90.535 (1)°	T = 123 K
V = 784.78 (5) Å^3	Fragment, yellow
Z = 2	0.40 × 0.30 × 0.15 mm

Data collection

Nonius KappaCCD diffractometer	910 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.069
Graphite monochromator	θmax = 24.9°, θmin = 3.7°
ϕ and ω scans	h = 0→10
2537 measured reflections	k = −6→6
1358 independent reflections	l = −17→18

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.063	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.135	All H-atom parameters refined
S = 1.19	Calculated w = 1/[σ^2(Fo^2) + (0.0434P)^2 + 0.1547P] where P = (Fo^2 + 2Fc^2)/3
1349 reflections	(Δ/σ)max < 0.001
140 parameters	Δρmax = 0.17 e Å^−3
0 restraints	Δρmin = −0.17 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 on F² for ALL reflections except for 9 with very negative F² or flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The observed criterion of F² > σ(F²) is used only for calculating _R_factor_obs 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
O1	0.1790 (2)	0.7137 (3)	0.32013 (12)	0.0290 (5)
N1	0.0452 (2)	0.3245 (4)	0.34121 (14)	0.0244 (6)
C9	0.0451 (3)	0.0878 (5)	0.4742 (2)	0.0248 (7)
C8	−0.0418 (3)	0.1595 (5)	0.3919 (2)	0.0270 (7)
C7	0.0870 (3)	0.2682 (5)	0.2638 (2)	0.0232 (7)
C6	0.1796 (3)	0.4203 (5)	0.2104 (2)	0.0209 (7)
C5	0.2285 (3)	0.3505 (5)	0.1278 (2)	0.0248 (7)
C4	0.3224 (3)	0.4866 (5)	0.0780 (2)	0.0284 (7)
C3	0.3686 (3)	0.6968 (5)	0.1103 (2)	0.0281 (7)
C2	0.3201 (3)	0.7715 (5)	0.1909 (2)	0.0260 (7)
C1	0.2250 (3)	0.6354 (5)	0.2414 (2)	0.0233 (7)
H5	0.193 (3)	0.199 (5)	0.1071 (16)	0.027 (7)*
H6	0.059 (3)	0.116 (5)	0.2399 (16)	0.028 (7)*
H8	−0.068 (3)	0.020 (5)	0.3579 (17)	0.030 (7)*
H2	0.352 (2)	0.918 (5)	0.2138 (15)	0.020 (7)*
H7	−0.144 (3)	0.238 (5)	0.4099 (17)	0.038 (8)*
H9	0.146 (3)	0.016 (4)	0.4559 (15)	0.018 (6)*
H3	0.436 (3)	0.797 (5)	0.0770 (17)	0.033 (8)*
H4	0.351 (3)	0.433 (5)	0.0200 (18)	0.032 (7)*
H10	0.069 (3)	0.233 (5)	0.5100 (19)	0.044 (9)*
H1	0.119 (4)	0.583 (7)	0.348 (3)	0.094 (13)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0353 (11)	0.0290 (12)	0.0227 (12)	0.0018 (9)	0.0022 (9)	−0.0056 (10)
N1	0.0220 (12)	0.0303 (15)	0.0208 (14)	0.0003 (10)	0.0003 (10)	0.0029 (12)
C9	0.023 (2)	0.030 (2)	0.022 (2)	−0.0018 (13)	0.0002 (12)	0.0027 (14)
C8	0.024 (2)	0.032 (2)	0.025 (2)	−0.0052 (14)	−0.0016 (13)	0.0043 (15)
C7	0.0210 (14)	0.026 (2)	0.022 (2)	0.0013 (13)	−0.0044 (12)	0.0016 (14)
C6	0.0207 (14)	0.024 (2)	0.018 (2)	0.0019 (12)	−0.0022 (12)	0.0022 (13)
C5	0.031 (2)	0.024 (2)	0.019 (2)	0.0013 (13)	−0.0037 (13)	0.0013 (14)
C4	0.033 (2)	0.034 (2)	0.018 (2)	0.0006 (14)	0.0028 (13)	0.0001 (15)
C3	0.027 (2)	0.031 (2)	0.026 (2)	−0.0003 (14)	0.0045 (13)	0.0113 (15)
C2	0.027 (2)	0.023 (2)	0.028 (2)	−0.0004 (13)	−0.0032 (13)	0.000 (2)
C1	0.0220 (14)	0.026 (2)	0.022 (2)	0.0044 (13)	−0.0039 (12)	0.0031 (14)

Geometric parameters (Å, º)

O1—C1	1.354 (3)	C7—H6	1.00 (3)
O1—H1	1.03 (4)	C6—C5	1.399 (3)
N1—C7	1.286 (3)	C6—C1	1.405 (4)
N1—C8	1.460 (3)	C5—C4	1.380 (4)
C9—C9^i	1.522 (5)	C5—H5	0.99 (3)
C9—C8	1.524 (4)	C4—C3	1.388 (4)
C9—H9	1.02 (2)	C4—H4	0.98 (3)
C9—H10	1.03 (3)	C3—C2	1.380 (4)
C8—H8	1.00 (3)	C3—H3	0.98 (3)
C8—H7	1.05 (3)	C2—C1	1.392 (4)
C7—C6	1.460 (4)	C2—H2	0.97 (3)
C1—O1—H1	106 (2)	C5—C6—C7	120.1 (3)
C7—N1—C8	118.2 (2)	C1—C6—C7	121.1 (2)
C9^i—C9—C8	111.1 (3)	C4—C5—C6	121.2 (3)
C9^i—C9—H9	108.4 (13)	C4—C5—H5	121.7 (14)
C8—C9—H9	108.2 (13)	C6—C5—H5	117.1 (14)
C9^i—C9—H10	112.7 (15)	C5—C4—C3	119.3 (3)
C8—C9—H10	107.7 (16)	C5—C4—H4	118.5 (16)
H9—C9—H10	108.5 (19)	C3—C4—H4	122.1 (16)
N1—C8—C9	111.4 (2)	C2—C3—C4	120.7 (3)
N1—C8—H8	112.7 (15)	C2—C3—H3	117.9 (16)
C9—C8—H8	108.5 (15)	C4—C3—H3	121.5 (16)
N1—C8—H7	107.4 (15)	C3—C2—C1	120.3 (3)
C9—C8—H7	109.0 (15)	C3—C2—H2	121.0 (13)
H8—C8—H7	108 (2)	C1—C2—H2	118.8 (14)
N1—C7—C6	121.4 (3)	O1—C1—C2	118.9 (3)
N1—C7—H6	119.8 (14)	O1—C1—C6	121.4 (2)
C6—C7—H6	118.7 (14)	C2—C1—C6	119.7 (3)
C5—C6—C1	118.7 (3)

Symmetry code: (i) −x, −y, −z+1.