Bis(N-octylsalicylideniminato-N,O)copper(II)

In the title compound, [Cu(C₁₅H₂₂NO)₂], the Cu^II cation lies on a centre of symmetry. The coordination geometry about the Cu^II ion is a parallelogram, formed by the N₂O₂ donor set of the two bidentate long alkane chain Schiff base imine-phenol ligands. The Cu-N and Cu-O distances are 2.009 (3) and 1.888 (3) Å, respectively.

S1. Comment

In enzyme systems, metal ions play an important role in terms of both structure and function. Hard cations are not only involved in the structural properties of proteins, but also show catalytic activity. Over the past few decades, metal-Schiff base complexes have been extensively investigated with regard to their function as model compounds for biological enzymes (Espinet et al., 1992; Giroud-Godquin & Maitlis, 1991). Some N,O-containing metal-Schiff base complexes possessing high catalytic activity show potential application in the fields of catalysis and medicine (Jacobsen et al., 1991; Schmidt et al., 1996). Copper-Schiff base complexes play an important role in both synthetic and structural research because they are useful stereochemical models in catalytic chemistry, with their preparative accessibility and structural variety (Garnovskii et al., 1993). Tetracoordinated copper-Schiff base complexes may form trans or cis planar or tetrahedral structures. A strictly planar or slightly distorted coordination is characteristic of transition metal complexes of Cu^II with a CuN₂O₂ coordination sphere (Elerman, Elmali, Kabak & Svoboda, 1998; Elerman, Elmali & Özbey, 1998; Elmali et al., 2000; Kabak et al., 1999). Often, the geometry of a trans-planar copper complex is a parallelogram. Here, we report the results of the reaction of Cu^II with a long alkane chain ligand, N-octylsalicylideneamine, which forms a monomeric copper-Schiff base complex, (I), in a trans-planar parallelogram coordination geometry with the Cu^II ion on a crystallographic centre of symmetry (Fig. 1). \sch

The bond lengths and angles around the Cu^II ion in (I) are in good agreement with the values found in other similar copper complexes (Akhtar & Drew, 1982; Labisbal et al., 1994) and in long alkane chain metal-Schiff base complexes (Asada et al., 2000). The Cu—N distances are longer than the Cu—O distances. No unusual bond lengths and angles are observed in the salen ligands of (I). Long alkane chain C—C bond distances are in the range 1.473 (7)–1.528 (9), phenyl C—C bond distances are in the range 1.371 (6)–1.415 (5), C—O 1.304 (4), C—N 1.470 (4) and C═N 1.288 (5) Å. These values are within the expected ranges for related salen derivatives (Blake et al., 1995; Zamian et al., 1995).

The molecules of the title copper-Schiff base complex exist as monomers, with Cu···Cu separations of 6.804 Å, leading to no dimeric interaction (Fig. 2). The long alkane chain molecules are stacked in columns along the a axis, while no connections are formed between the chain ends of two adjacent copper complexes. The alkane chains are reasonably linear, but the entire molecule is not as planar as some other copper-Schiff base complexes (Elmali et al., 2000; Kabak et al., 1999). No overlap between the aromatic rings of two adjacent [Cu(C₁₅H₂₂NO)₂] units is seen, which is in contrast with the cases of π-stacking of aromatic rings that have recently been reported by Amoroso et al. (1995) and Muñoz et al. (1998).

S2. Experimental

To a solution of salicylaldehyde (2.0 mmol) in boiling absolute ethanol (10 ml), n-octylamine (2.0 mmol) was added dropwise. After stirring for a few minutes, a solution containing [Cu(O₂CCH₃)₂]·H₂O (1.0 mmol) and CH₃CO₂Na·3H₂O (1.5 mmol) in hot water (6 ml) was added slowly to the boiling mixture. During this addition, a large amount of brown powder precipitated. The reaction mixture was refluxed for half an hour and then cooled to room temperature. The crystalline precipitate was filtered off (yield 80%). Brown single crystals of (I) (m.p. 337 K) suitable for X-ray diffraction were grown by slow evaporation over a few weeks. The product was soluble in organic solvents, e.g. chloroform. IR (KBr), ν (C═N): 1618 and 1597 cm^-1.

S3. Refinement

All H atoms were placed at calculated positions and treated as riding, with C—H = 0.93–0.97 Å and U_iso(H) = 1.5U_eq(C) for methyl H and 1.2U_eq(C) for other H atoms. Are these the correct constraints?

Computing details

Data collection: SMART (Bruker, 2001); cell refinement: SMART; data reduction: SHELXTL (Bruker, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. The molecular structure and atom-labelling scheme of (I). Displacement ellipsoids are plotted at the 30% probability level and H atoms are drawn as small spheres of arbitrary radii.
	Fig. 2. A perspective view of the unit cell of (I). H atoms have been omitted for clarity.

Bis(N-octylsalicylideneaminato-N,O)copper(II)

Crystal data

[Cu(C15H22NO)2]	F(000) = 566
Mr = 528.21	Dx = 1.167 Mg m^−3
Monoclinic, P21/c	Melting point: 337 K
a = 16.571 (4) Å	Mo Kα radiation, λ = 0.71073 Å
b = 9.742 (3) Å	Cell parameters from 37 reflections
c = 9.500 (3) Å	µ = 0.75 mm^−1
β = 101.507 (5)°	T = 298 K
V = 1502.9 (7) Å^3	Block, brown
Z = 2	0.20 × 0.20 × 0.15 mm

Data collection

Bruker SMART CCD area-detector Query diffractometer	2656 independent reflections
Radiation source: fine-focus sealed tube	1414 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.056
ϕ and ω scans	θmax = 25.0°, θmin = 2.4°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −19→18
Tmin = 0.864, Tmax = 0.896	k = −11→10
6066 measured reflections	l = −6→11

Refinement

Refinement on F^2	2 restraints
Least-squares matrix: full	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.048	w = 1/[[σ^2(Fo^2) + (0.05P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.126	(Δ/σ)max = 0.017
S = 1.03	Δρmax = 0.27 e Å^−3
2656 reflections	Δρmin = −0.23 e Å^−3
160 parameters

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
Cu1	0.0000	0.0000	1.0000	0.0526 (3)
O1	−0.06756 (17)	0.0048 (3)	0.8149 (3)	0.0677 (8)
N1	0.02423 (17)	0.2014 (3)	0.9901 (3)	0.0498 (9)
C1	0.0908 (2)	0.2654 (4)	1.0952 (4)	0.0558 (11)
H1A	0.0874	0.2345	1.1909	0.067*
H1B	0.0837	0.3643	1.0920	0.067*
C2	0.1746 (2)	0.2301 (4)	1.0658 (5)	0.0658 (12)
H2A	0.1766	0.2558	0.9679	0.079*
H2B	0.1828	0.1316	1.0746	0.079*
C3	0.2437 (3)	0.3021 (5)	1.1678 (5)	0.0805 (15)
H3A	0.2304	0.3989	1.1708	0.097*
H3B	0.2469	0.2652	1.2636	0.097*
C4	0.3257 (3)	0.2881 (6)	1.1284 (6)	0.109 (2)
H4A	0.3225	0.3272	1.0335	0.131*
H4B	0.3379	0.1912	1.1223	0.131*
C5	0.3969 (3)	0.3555 (7)	1.2304 (7)	0.149 (3)
H5A	0.4022	0.3143	1.3248	0.179*
H5B	0.3850	0.4523	1.2390	0.179*
C6	0.4783 (4)	0.3402 (9)	1.1796 (10)	0.194 (4)
H6A	0.4875	0.2441	1.1612	0.233*
H6B	0.4751	0.3900	1.0902	0.233*
C7	0.5480 (5)	0.3928 (11)	1.2870 (11)	0.241 (5)
H7A	0.5541	0.3414	1.3759	0.289*
H7B	0.5403	0.4890	1.3070	0.289*
C8	0.6224 (5)	0.3735 (12)	1.2191 (12)	0.271 (6)
H8A	0.6696	0.4153	1.2787	0.407*
H8B	0.6123	0.4157	1.1259	0.407*
H8C	0.6325	0.2772	1.2096	0.407*
C11	−0.1042 (2)	0.1097 (4)	0.7441 (5)	0.0562 (11)
C12	−0.1667 (3)	0.0867 (5)	0.6226 (5)	0.0708 (13)
H12A	−0.1812	−0.0031	0.5954	0.085*
C13	−0.2067 (3)	0.1929 (5)	0.5432 (5)	0.0778 (14)
H13A	−0.2479	0.1737	0.4637	0.093*
C14	−0.1870 (3)	0.3280 (5)	0.5793 (5)	0.0738 (13)
H14A	−0.2149	0.3998	0.5261	0.089*
C15	−0.1251 (3)	0.3533 (4)	0.6960 (5)	0.0636 (12)
H15A	−0.1106	0.4437	0.7201	0.076*
C16	−0.0832 (2)	0.2479 (4)	0.7797 (4)	0.0495 (10)
C17	−0.0182 (2)	0.2828 (4)	0.8968 (5)	0.0528 (11)
H17A	−0.0049	0.3755	0.9071	0.063*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.0644 (4)	0.0447 (4)	0.0471 (4)	−0.0031 (4)	0.0075 (3)	−0.0023 (4)
O1	0.0948 (19)	0.0436 (16)	0.0562 (18)	−0.0009 (17)	−0.0054 (15)	−0.0035 (17)
N1	0.056 (2)	0.048 (2)	0.046 (2)	−0.0016 (15)	0.0104 (18)	−0.0070 (17)
C1	0.071 (3)	0.047 (2)	0.048 (3)	−0.008 (2)	0.007 (2)	−0.006 (2)
C2	0.063 (3)	0.064 (3)	0.069 (3)	−0.013 (2)	0.010 (2)	−0.002 (2)
C3	0.068 (3)	0.102 (4)	0.068 (3)	−0.014 (3)	0.005 (3)	0.004 (3)
C4	0.066 (3)	0.138 (5)	0.120 (5)	−0.007 (3)	0.010 (3)	0.006 (4)
C5	0.081 (4)	0.220 (9)	0.134 (6)	−0.047 (5)	−0.007 (4)	0.021 (5)
C6	0.075 (5)	0.290 (11)	0.210 (9)	−0.050 (6)	0.011 (6)	−0.001 (8)
C7	0.121 (7)	0.326 (15)	0.282 (14)	−0.036 (8)	0.057 (8)	−0.031 (11)
C8	0.136 (8)	0.381 (18)	0.291 (15)	0.020 (9)	0.028 (9)	0.028 (11)
C11	0.062 (3)	0.060 (3)	0.045 (3)	0.002 (2)	0.009 (2)	0.002 (2)
C12	0.085 (3)	0.054 (3)	0.065 (3)	−0.005 (3)	−0.003 (3)	−0.004 (2)
C13	0.078 (3)	0.078 (4)	0.068 (4)	0.001 (3)	−0.007 (3)	0.007 (3)
C14	0.081 (3)	0.064 (3)	0.074 (4)	0.017 (3)	0.008 (3)	0.017 (3)
C15	0.074 (3)	0.051 (3)	0.065 (3)	0.004 (2)	0.013 (3)	0.005 (2)
C16	0.058 (3)	0.046 (2)	0.046 (3)	−0.001 (2)	0.015 (2)	0.001 (2)
C17	0.061 (3)	0.043 (2)	0.059 (3)	−0.004 (2)	0.021 (2)	−0.006 (2)

Geometric parameters (Å, º)

Cu1—O1	1.888 (3)	C2—H2A	0.97
Cu1—N1	2.009 (3)	C2—H2B	0.97
O1—C11	1.304 (4)	C3—H3A	0.97
N1—C17	1.288 (5)	C3—H3B	0.97
N1—C1	1.470 (4)	C4—H4A	0.97
C1—C2	1.511 (5)	C4—H4B	0.97
C2—C3	1.516 (5)	C5—H5A	0.97
C3—C4	1.487 (6)	C5—H5B	0.97
C4—C5	1.518 (7)	C6—H6A	0.97
C5—C6	1.528 (9)	C6—H6B	0.97
C6—C7	1.473 (7)	C7—H7A	0.97
C7—C8	1.512 (8)	C7—H7B	0.97
C11—C12	1.406 (5)	C8—H8A	0.96
C11—C16	1.415 (5)	C8—H8B	0.96
C12—C13	1.371 (6)	C8—H8C	0.96
C13—C14	1.383 (6)	C12—H12A	0.93
C14—C15	1.374 (5)	C13—H13A	0.93
C15—C16	1.395 (5)	C14—H14A	0.93
C16—C17	1.426 (5)	C15—H15A	0.93
C1—H1A	0.97	C17—H17A	0.93
C1—H1B	0.97
O1^i—Cu1—O1	180.0	C4—C3—H3B	109
O1^i—Cu1—N1	88.91 (13)	H3A—C3—H3B	108
O1—Cu1—N1	91.09 (13)	C3—C4—H4A	108
N1—Cu1—N1^i	180.0	C3—C4—H4B	108
C11—O1—Cu1	128.9 (3)	C5—C4—H4A	108
C17—N1—C1	116.0 (3)	C5—C4—H4B	108
C17—N1—Cu1	123.1 (3)	H4A—C4—H4B	107
C1—N1—Cu1	120.8 (2)	C4—C5—H5A	109
N1—C1—C2	111.8 (3)	C4—C5—H5B	109
C1—C2—C3	112.4 (4)	C6—C5—H5A	109
C4—C3—C2	114.1 (4)	C6—C5—H5B	109
C3—C4—C5	115.6 (5)	H5A—C5—H5B	108
C4—C5—C6	112.2 (6)	C5—C6—H6A	109
C7—C6—C5	111.5 (7)	C5—C6—H6B	109
C6—C7—C8	104.8 (7)	C7—C6—H6A	109
O1—C11—C12	119.3 (4)	C7—C6—H6B	109
O1—C11—C16	123.8 (4)	H6A—C6—H6B	108
C12—C11—C16	117.0 (4)	C6—C7—H7A	111
C13—C12—C11	121.9 (4)	C6—C7—H7B	111
C12—C13—C14	121.1 (4)	C8—C7—H7A	111
C15—C14—C13	118.1 (4)	C8—C7—H7B	111
C14—C15—C16	122.3 (4)	H7A—C7—H7B	109
C15—C16—C11	119.5 (4)	C7—C8—H8A	110
C15—C16—C17	118.8 (4)	C7—C8—H8B	110
C11—C16—C17	121.6 (4)	C7—C8—H8C	110
N1—C17—C16	127.9 (4)	H8A—C8—H8B	110
N1—C1—H1A	109	H8B—C8—H8C	110
N1—C1—H1B	109	H8C—C8—H8A	110
C2—C1—H1A	109	C11—C12—H12A	119
C2—C1—H1B	109	C13—C12—H12A	119
H1A—C1—H1B	108	C12—C13—H13A	119
C1—C2—H2A	109	C14—C13—H13A	119
C1—C2—H2B	109	C13—C14—H14A	121
C3—C2—H2A	109	C15—C14—H14A	121
C3—C2—H2B	109	C14—C15—H15A	119
H2A—C2—H2B	108	C16—C15—H15A	119
C2—C3—H3A	109	C16—C17—H17A	116
C2—C3—H3B	109	N1—C17—H17A	116
C4—C3—H3A	109

Symmetry code: (i) −x, −y, −z+2.