2,2′-[1,1′-(Propane-2,2-diyldiimino)­diethyl­idene]­diphenol

In the crystal structure of the title compound, C₂₁H₃₀N₂O₂, inter­molecular N—H...O hydrogen bonds result in the formation of chains along the b axis. Intra­molecular O—H...N and N—H...O hydrogen bonds are also present.

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.061
• wR factor = 0.207
• Data-to-parameter ratio = 25.9

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT029_ALERT_3_C _diffrn_measured_fraction_theta_full Low .......       0.97
PLAT147_ALERT_1_C su on Symmetry Constrained Cell Angle(s) .......          ?

Alert level G
PLAT793_ALERT_1_G Check the Absolute Configuration of C7     = ...          S
PLAT793_ALERT_1_G Check the Absolute Configuration of C13    = ...          R

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   2 ALERT level C = Check and explain
   2 ALERT level G = General alerts; check

   3 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   1 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

It has been reported by many studies that Schiff bases form mononuclear or dinuclear compounds with phenylboronic and boric acids (Burgess et al., 1999; Höpfl et al., 1998; Maciejewska et al., 1999; Mitra et al., 2006; Mitra et al., 2004). In these studies, the compounds of reduced forms of Schiff bases also exist (Mitra et al., 2006). It has been noted that tri- and tetracoordinated compounds are formed between reduced Schiff bases and organic esters of boric acid. In this study, an ONNO type Schiff base has reduced to phenol imine form with the usage of NaBH₄ in MeOH media. In fact, it was aimed to prepare a new complex from reaction of Schiff base and phenylboronic acid, but Schiff base crystal which is suitable for X-ray analysis was obtained. When ligand is crystallized in the common solvents, the appropriate single crystals for X-ray analysis could not be obtained. It was concluded that first phenylboronic acid and ligand are formed an intermediate complex, which is affected the solubility of Schiff base. Hence it was inferred that this procedure could be a new recrystallization method for organic ligands. We report herein the crystal structure of the title compound, (I).

In the molecule of (I) (Fig. 1), the bond lengths and angles are generally within normal ranges (Allen et al., 1987). In the form of the Schiff base, C=N double bond is about 1.27–1.30 Å (Sanchez et al., 2004). After the reduction reaction of double bond, it was converted to mono bonds (C7—N1 [1.483 (2) Å] and C13—N2 [1.481 (2) Å]). The strong hydrogen bond between iminic nitrogen (in the form of Schiff base) and phenol group continued after reduction (Yalçın et al., 2001).

Rings A (C1—C6) and B (C15—C20) are, of course, planar and the dihedral angle between them is A/B = 89.65 (2)°.

In the crystal structure, intermolecular N—H···O and intramolecular O—H—N and N—H—O hydrogen bonds (Table 1) result in the formation of chains along the b axis (Fig. 2), in which they seem to be effective in the stabilization of the structure.

Related literature

For general backgroud, see: Burgess et al. (1999); Höpfl et al. (1998); Maciejewska et al. (1999); Mitra et al. (2004, 2006); Yalçın et al. (2001). For bond-length data, see: Allen et al. (1987); Sanchez et al. (2004).

S2. Experimental

The ligand was prepared in two steps. In the first step, the Schiff base was synthesized from 2-hydroxy acetophenone (2.72 g. 20 mmol) and 2,2'-dimethyl -1,3-propanediamine (1.02 g, 10 mmol) in MeOH (50 ml) solution. The mixture was heated until boiling temperature and left to stand on air. After one day, the yellow Schiff base was crystallized. In the second step, the Schiff base (2.0 g) was dissolved in hot MeOH (100 ml) and a piece of solid NaBH₄ was added slowly to this solution until it turned colorless. The reduced Schiff base precipitated after addition of ice. The mixture was left to stand at 277 K for 1 d to obtain crystals, and then was filtered. The crystals were allowed to dry on air. For the preparation of the title complex, the ligand (0.689 g, 2 mmol) was dissolved in hot MeOH (50 ml) and the solution of phenylboronic acid (0.244 g, 2 mmol) in hot acetonitrile (40 ml.) was added. The colorless crystals of (I) were obtained by filtration after 2 d and allowed to dry on air.

S3. Refinement

H1N and H2N (for NH₂) were located in difference syntheses and refined isotropically [N—H = 0.846 (19) and 0.95 (2) Å, U_iso(H) = 0.064 (5) and 0.091 (7) Ų]. The remaining H atoms were positioned geometrically, with O—H = 0.82 Å (for OH), C—H = 0.93, 0.98, 0.97 and 0.96 Å for aromatic, methine, methylene and methyl H, and constrained to ride on their parent atoms, with U_iso(H) = xU_eq(C,O), where x = 1.2 for aromatic, methine and methylene H, and x = 1.5 for all other H atoms.

Computing details

Data collection: CrystalClear (Rigaku/MSC, 2005); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. The molecular structure of the title molecule, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. A packing diagram of (I). Hydrogen bonds are shown as dashed lines.

2,2'-[1,1'-(Propane-2,2-diyldiimino)diethylidene]diphenol

Crystal data

C21H30N2O2	F(000) = 744
Mr = 342.47	Dx = 1.119 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 5943 reflections
a = 11.4232 (3) Å	θ = 2.3–30.5°
b = 10.1303 (3) Å	µ = 0.07 mm^−1
c = 18.4399 (4) Å	T = 298 K
β = 107.753 (5)°	Needle, colorless
V = 2032.26 (11) Å^3	0.2 × 0.13 × 0.1 mm
Z = 4

Data collection

Rigaku R-AXIS RAPID-S diffractometer	3287 reflections with I > 2σ(I)
dtprofit.ref scans	Rint = 0.063
Absorption correction: multi-scan (Blessing, 1995)	θmax = 30.9°, θmin = 2.3°
Tmin = 0.986, Tmax = 0.986	h = −16→16
57575 measured reflections	k = −14→12
6244 independent reflections	l = −26→26

Refinement

Refinement on F^2	H atoms treated by a mixture of independent and constrained refinement
Least-squares matrix: full	w = 1/[σ^2(Fo^2) + (0.0883P)^2 + 0.1285P] where P = (Fo^2 + 2Fc^2)/3
R[F^2 > 2σ(F^2)] = 0.061	(Δ/σ)max < 0.001
wR(F^2) = 0.207	Δρmax = 0.19 e Å^−3
S = 1.04	Δρmin = −0.15 e Å^−3
6244 reflections	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
241 parameters	Extinction coefficient: 0.016 (3)
0 restraints

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.65507 (14)	0.05781 (12)	0.93601 (8)	0.0828 (4)
H1O	0.6018	0.0768	0.8962	0.124*
O2	0.20908 (13)	0.27291 (14)	0.74075 (8)	0.0812 (4)
H2O	0.2582	0.2978	0.7192	0.122*
N1	0.49252 (14)	0.21069 (13)	0.83918 (7)	0.0574 (3)
H1N	0.4199 (18)	0.1886 (17)	0.8146 (10)	0.064 (5)*
N2	0.34204 (12)	0.25810 (14)	0.64438 (8)	0.0575 (3)
H2N	0.361 (2)	0.329 (2)	0.6160 (12)	0.091 (7)*
C1	0.65405 (19)	0.3908 (2)	1.01181 (10)	0.0720 (5)
H1	0.6049	0.4659	1.0031	0.086*
C2	0.7652 (2)	0.3934 (3)	1.06795 (12)	0.0892 (7)
H2	0.7908	0.4689	1.0972	0.107*
C3	0.8377 (2)	0.2830 (3)	1.08019 (12)	0.0967 (8)
H3	0.9127	0.2833	1.1186	0.116*
C4	0.80105 (19)	0.1706 (3)	1.03618 (12)	0.0880 (6)
H4	0.8516	0.0966	1.0447	0.106*
C5	0.68921 (17)	0.16917 (19)	0.97972 (10)	0.0679 (5)
C6	0.61266 (15)	0.27926 (17)	0.96746 (9)	0.0591 (4)
C7	0.48655 (16)	0.27559 (17)	0.91006 (9)	0.0618 (4)
H7	0.4574	0.3664	0.8981	0.074*
C8	0.39556 (19)	0.2018 (2)	0.94084 (12)	0.0862 (6)
H8A	0.3158	0.2028	0.9035	0.129*
H8B	0.3912	0.2439	0.9866	0.129*
H8C	0.4224	0.1121	0.9518	0.129*
C9	0.56465 (14)	0.23663 (14)	0.72343 (9)	0.0519 (4)
C10	0.60725 (17)	0.34573 (17)	0.67959 (10)	0.0658 (4)
H10A	0.5446	0.4122	0.6642	0.099*
H10B	0.6222	0.3086	0.6353	0.099*
H10C	0.6816	0.3847	0.7118	0.099*
C11	0.66557 (16)	0.13156 (17)	0.74808 (10)	0.0661 (4)
H11A	0.7405	0.1719	0.7785	0.099*
H11B	0.6785	0.0922	0.7038	0.099*
H11C	0.6409	0.0648	0.7774	0.099*
C12	0.44819 (14)	0.17011 (15)	0.67180 (9)	0.0550 (4)
H12A	0.4668	0.1326	0.6282	0.066*
H12B	0.426	0.0979	0.6996	0.066*
C13	0.23218 (15)	0.18842 (18)	0.59568 (10)	0.0641 (4)
H13	0.2578	0.1299	0.561	0.077*
C14	0.14172 (19)	0.2887 (2)	0.54867 (12)	0.0884 (6)
H14A	0.1159	0.3468	0.582	0.133*
H14B	0.0715	0.2435	0.5159	0.133*
H14C	0.1806	0.3391	0.5184	0.133*
C15	0.17410 (15)	0.10502 (18)	0.64405 (10)	0.0632 (4)
C16	0.12464 (17)	−0.0173 (2)	0.61865 (13)	0.0813 (6)
H16	0.1345	−0.0517	0.5741	0.098*
C17	0.0609 (2)	−0.0898 (3)	0.65776 (16)	0.0990 (8)
H17	0.0277	−0.1715	0.6396	0.119*
C18	0.0474 (2)	−0.0394 (3)	0.72403 (17)	0.1016 (8)
H18	0.0038	−0.087	0.7505	0.122*
C19	0.09767 (19)	0.0807 (3)	0.75152 (12)	0.0875 (6)
H19	0.089	0.1134	0.7967	0.105*
C20	0.16146 (16)	0.1535 (2)	0.71185 (11)	0.0691 (5)
C21	0.54208 (16)	0.30049 (15)	0.79304 (9)	0.0555 (4)
H21A	0.619	0.3368	0.8251	0.067*
H21B	0.4852	0.3733	0.776	0.067*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0960 (11)	0.0667 (8)	0.0763 (9)	0.0131 (7)	0.0124 (7)	−0.0003 (6)
O2	0.0779 (9)	0.0896 (10)	0.0826 (9)	0.0055 (7)	0.0342 (7)	−0.0072 (7)
N1	0.0613 (9)	0.0585 (8)	0.0518 (7)	−0.0081 (6)	0.0166 (6)	−0.0042 (6)
N2	0.0516 (7)	0.0576 (8)	0.0621 (8)	−0.0012 (6)	0.0154 (6)	0.0016 (6)
C1	0.0836 (13)	0.0765 (12)	0.0631 (10)	−0.0157 (10)	0.0333 (9)	−0.0123 (9)
C2	0.0855 (15)	0.1143 (18)	0.0714 (12)	−0.0345 (14)	0.0292 (11)	−0.0239 (12)
C3	0.0632 (12)	0.153 (2)	0.0696 (12)	−0.0242 (14)	0.0133 (10)	−0.0096 (14)
C4	0.0650 (12)	0.1197 (18)	0.0743 (12)	0.0107 (12)	0.0136 (10)	0.0034 (12)
C5	0.0672 (11)	0.0762 (11)	0.0596 (9)	−0.0021 (9)	0.0185 (8)	−0.0016 (8)
C6	0.0619 (9)	0.0672 (10)	0.0515 (8)	−0.0046 (8)	0.0222 (7)	−0.0038 (7)
C7	0.0648 (10)	0.0678 (10)	0.0555 (9)	0.0005 (8)	0.0223 (8)	−0.0035 (7)
C8	0.0695 (12)	0.1258 (18)	0.0692 (11)	−0.0129 (12)	0.0297 (10)	−0.0042 (11)
C9	0.0525 (8)	0.0499 (8)	0.0542 (8)	−0.0012 (6)	0.0175 (6)	−0.0008 (6)
C10	0.0642 (10)	0.0676 (10)	0.0680 (10)	−0.0069 (8)	0.0239 (8)	0.0051 (8)
C11	0.0620 (10)	0.0659 (10)	0.0699 (10)	0.0075 (8)	0.0192 (8)	−0.0002 (8)
C12	0.0568 (9)	0.0522 (8)	0.0566 (8)	0.0005 (7)	0.0179 (7)	−0.0043 (7)
C13	0.0528 (9)	0.0762 (11)	0.0615 (9)	−0.0068 (8)	0.0148 (7)	−0.0012 (8)
C14	0.0641 (11)	0.1088 (16)	0.0826 (13)	−0.0033 (11)	0.0081 (10)	0.0301 (12)
C15	0.0496 (8)	0.0690 (10)	0.0691 (10)	0.0006 (7)	0.0154 (7)	0.0088 (8)
C16	0.0647 (11)	0.0791 (13)	0.0945 (14)	−0.0097 (10)	0.0160 (10)	0.0026 (11)
C17	0.0769 (14)	0.0833 (15)	0.127 (2)	−0.0152 (11)	0.0160 (14)	0.0230 (14)
C18	0.0696 (13)	0.117 (2)	0.1165 (19)	−0.0062 (13)	0.0258 (13)	0.0496 (16)
C19	0.0674 (12)	0.1145 (17)	0.0850 (13)	0.0118 (12)	0.0297 (10)	0.0290 (13)
C20	0.0537 (9)	0.0791 (12)	0.0752 (11)	0.0087 (8)	0.0204 (8)	0.0151 (9)
C21	0.0601 (9)	0.0494 (8)	0.0556 (8)	−0.0038 (7)	0.0157 (7)	−0.0022 (6)

Geometric parameters (Å, º)

O1—C5	1.372 (2)	C9—C10	1.534 (2)
O1—H1O	0.82	C10—H10A	0.96
O2—C20	1.366 (2)	C10—H10B	0.96
O2—H2O	0.82	C10—H10C	0.96
N1—C21	1.472 (2)	C11—H11A	0.96
N1—C7	1.483 (2)	C11—H11B	0.96
N1—H1N	0.846 (19)	C11—H11C	0.96
N2—C12	1.465 (2)	C12—C9	1.536 (2)
N2—C13	1.481 (2)	C12—H12A	0.97
N2—H2N	0.95 (2)	C12—H12B	0.97
C1—C2	1.372 (3)	C13—C14	1.518 (3)
C1—H1	0.93	C13—H13	0.98
C2—H2	0.93	C14—H14A	0.96
C3—C2	1.370 (4)	C14—H14B	0.96
C3—C4	1.386 (3)	C14—H14C	0.96
C3—H3	0.93	C15—C16	1.383 (3)
C4—H4	0.93	C15—C20	1.391 (3)
C5—C4	1.380 (3)	C15—C13	1.520 (2)
C6—C1	1.390 (2)	C16—H16	0.93
C6—C5	1.392 (3)	C17—C18	1.376 (4)
C6—C7	1.506 (2)	C17—C16	1.382 (3)
C7—C8	1.524 (3)	C17—H17	0.93
C7—H7	0.98	C18—H18	0.93
C8—H8A	0.96	C19—C18	1.375 (4)
C8—H8B	0.96	C19—H19	0.93
C8—H8C	0.96	C20—C19	1.391 (3)
C9—C21	1.528 (2)	C21—H21A	0.97
C9—C11	1.533 (2)	C21—H21B	0.97
C5—O1—H1O	109.5	H10B—C10—H10C	109.5
C20—O2—H2O	109.5	C9—C11—H11A	109.5
C21—N1—C7	111.39 (13)	C9—C11—H11B	109.5
C21—N1—H1N	109.9 (12)	H11A—C11—H11B	109.5
C7—N1—H1N	106.8 (12)	C9—C11—H11C	109.5
C12—N2—C13	112.24 (14)	H11A—C11—H11C	109.5
C12—N2—H2N	110.3 (13)	H11B—C11—H11C	109.5
C13—N2—H2N	108.4 (13)	N2—C12—C9	114.61 (13)
C2—C1—C6	122.0 (2)	N2—C12—H12A	108.6
C2—C1—H1	119	C9—C12—H12A	108.6
C6—C1—H1	119	N2—C12—H12B	108.6
C3—C2—C1	118.9 (2)	C9—C12—H12B	108.6
C3—C2—H2	120.6	H12A—C12—H12B	107.6
C1—C2—H2	120.6	N2—C13—C14	109.33 (16)
C2—C3—C4	121.0 (2)	N2—C13—C15	110.49 (14)
C2—C3—H3	119.5	C14—C13—C15	111.35 (15)
C4—C3—H3	119.5	N2—C13—H13	108.5
C5—C4—C3	119.7 (2)	C14—C13—H13	108.5
C5—C4—H4	120.1	C15—C13—H13	108.5
C3—C4—H4	120.1	C13—C14—H14A	109.5
O1—C5—C4	118.94 (18)	C13—C14—H14B	109.5
O1—C5—C6	120.74 (16)	H14A—C14—H14B	109.5
C4—C5—C6	120.31 (18)	C13—C14—H14C	109.5
C1—C6—C5	118.12 (17)	H14A—C14—H14C	109.5
C1—C6—C7	120.96 (16)	H14B—C14—H14C	109.5
C5—C6—C7	120.88 (15)	C16—C15—C20	118.47 (18)
N1—C7—C6	109.83 (14)	C16—C15—C13	120.38 (17)
N1—C7—C8	109.31 (15)	C20—C15—C13	120.99 (16)
C6—C7—C8	111.43 (14)	C17—C16—C15	121.7 (2)
N1—C7—H7	108.7	C17—C16—H16	119.2
C6—C7—H7	108.7	C15—C16—H16	119.2
C8—C7—H7	108.7	C18—C17—C16	119.1 (2)
C7—C8—H8A	109.5	C18—C17—H17	120.5
C7—C8—H8B	109.5	C16—C17—H17	120.5
H8A—C8—H8B	109.5	C19—C18—C17	120.6 (2)
C7—C8—H8C	109.5	C19—C18—H18	119.7
H8A—C8—H8C	109.5	C17—C18—H18	119.7
H8B—C8—H8C	109.5	C18—C19—C20	120.1 (2)
C21—C9—C11	110.45 (13)	C18—C19—H19	119.9
C21—C9—C10	107.44 (13)	C20—C19—H19	119.9
C11—C9—C10	109.02 (14)	O2—C20—C19	118.30 (19)
C21—C9—C12	111.75 (13)	O2—C20—C15	121.65 (16)
C11—C9—C12	108.07 (13)	C19—C20—C15	120.0 (2)
C10—C9—C12	110.09 (13)	N1—C21—C9	114.66 (12)
C9—C10—H10A	109.5	N1—C21—H21A	108.6
C9—C10—H10B	109.5	C9—C21—H21A	108.6
H10A—C10—H10B	109.5	N1—C21—H21B	108.6
C9—C10—H10C	109.5	C9—C21—H21B	108.6
H10A—C10—H10C	109.5	H21A—C21—H21B	107.6
C21—N1—C7—C6	−77.69 (17)	C11—C9—C21—N1	−65.04 (18)
C21—N1—C7—C8	159.77 (15)	C10—C9—C21—N1	176.16 (13)
C7—N1—C21—C9	173.51 (13)	C12—C9—C21—N1	55.30 (18)
C13—N2—C12—C9	−179.33 (13)	N2—C12—C9—C21	57.33 (17)
C12—N2—C13—C14	−161.12 (15)	N2—C12—C9—C11	179.05 (13)
C12—N2—C13—C15	76.00 (17)	N2—C12—C9—C10	−61.98 (17)
C6—C1—C2—C3	0.5 (3)	C16—C15—C13—N2	−142.22 (16)
C2—C3—C4—C5	−0.7 (3)	C20—C15—C13—N2	42.5 (2)
C4—C3—C2—C1	0.9 (3)	C16—C15—C13—C14	96.1 (2)
O1—C5—C4—C3	179.13 (19)	C20—C15—C13—C14	−79.2 (2)
C6—C5—C4—C3	−0.8 (3)	C20—C15—C16—C17	1.7 (3)
C5—C6—C1—C2	−2.0 (3)	C13—C15—C16—C17	−173.71 (18)
C7—C6—C1—C2	175.56 (16)	C16—C15—C20—O2	179.33 (17)
C1—C6—C5—O1	−177.83 (16)	C13—C15—C20—O2	−5.3 (3)
C7—C6—C5—O1	4.7 (2)	C16—C15—C20—C19	−1.5 (3)
C1—C6—C5—C4	2.1 (3)	C13—C15—C20—C19	173.86 (16)
C7—C6—C5—C4	−175.45 (17)	C16—C17—C18—C19	−0.7 (3)
C1—C6—C7—N1	138.62 (16)	C18—C17—C16—C15	−0.6 (3)
C5—C6—C7—N1	−43.9 (2)	C20—C19—C18—C17	0.9 (3)
C1—C6—C7—C8	−100.1 (2)	O2—C20—C19—C18	179.43 (18)
C5—C6—C7—C8	77.3 (2)	C15—C20—C19—C18	0.3 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1N···O2	0.85 (2)	2.53 (2)	3.254 (2)	144.9 (15)
O1—H1O···N1	0.82	1.92	2.648 (2)	147
N2—H2N···O1^i	0.95 (2)	2.49 (2)	3.3833 (19)	156.00
O2—H2O···N2	0.82	1.95	2.671 (2)	147

Symmetry code: (i) −x+1, y+1/2, −z+3/2.