Bis[4-(4-bromophenylimino-κN)pent-2-en-2-olato-κO]copper(II)

Paul S E Bungu; Marietjie Schutte; G Steyl

doi:10.1107/S1600536812042420

. 2012 Oct 20;68(Pt 11):m1373. doi: 10.1107/S1600536812042420

Bis[4-(4-bromophenylimino-κN)pent-2-en-2-olato-κO]copper(II)

Paul S E Bungu ^a,^*, Marietjie Schutte ^a, G Steyl ^a

PMCID: PMC3515125 PMID: 23284352

Abstract

In the title compound, [Cu(C₁₁H₁₁BrNO)₂], the Cu^II atom is in a distorted square-planar geometry, with the two bidentate ketimine ligands positioned in a trans geometry. Two intermolecular C—H⋯O hydrogen bond interactions are present which link the molecules in a zigzag manner along the a axis. The molecules pack in layers along the diagonal of the bc plane.

Related literature

For similar structures, see: Bourget-Merle et al. (2002 ▶); Bryndin et al. (2008 ▶) Hsu et al. (2004 ▶, 2007 ▶) John et al. (2007 ▶); Stender et al. (2001 ▶).

Experimental

Crystal data

[Cu(C₁₁H₁₁BrNO)₂]
M _r = 569.77
Monoclinic,
a = 12.493 (3) Å
b = 11.559 (4) Å
c = 15.415 (4) Å
β = 92.306 (14)°
V = 2224.2 (11) Å³
Z = 4
Mo Kα radiation
μ = 4.60 mm⁻¹
T = 100 K
0.64 × 0.25 × 0.15 mm

Data collection

Bruker APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2008 ▶) T _min = 0.262, T _max = 0.502
13700 measured reflections
5558 independent reflections
4291 reflections with I > 2σ(I)
R _int = 0.034

Refinement

R[F ² > 2σ(F ²)] = 0.034
wR(F ²) = 0.082
S = 1.00
5558 reflections
266 parameters
H-atom parameters constrained
Δρ_max = 0.65 e Å⁻³
Δρ_min = −0.89 e Å⁻³

Data collection: APEX2 (Bruker, 2008 ▶); cell refinement: SAINT-Plus (Bruker, 2008 ▶); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: DIAMOND (Brandenburg & Putz, 2005 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶).

Supplementary Material

Click here for additional data file.^{(19.4KB, cif)}

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536812042420/gg2104sup1.cif

e-68-m1373-sup1.cif^{(19.4KB, cif)}

Click here for additional data file.^{(265.3KB, hkl)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812042420/gg2104Isup2.hkl

e-68-m1373-Isup2.hkl^{(265.3KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected bond lengths (Å).

N1—Cu1	1.958 (2)
N2—Cu1	1.948 (2)
O1—Cu1	1.9110 (17)
O2—Cu1	1.9085 (19)

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Table 2. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C115—H115⋯O1ⁱ	0.95	2.47	3.370 (3)	157
C215—H215⋯O2ⁱⁱ	0.95	2.54	3.378 (3)	147

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

We would like to thank the crystallographer, Ricky Kotze, for the data collection, and the University of the Free State, the Chemistry Department, the NRF, Sasol Ltd and Inkaba YeAfrica for funding.

supplementary crystallographic information

Comment

Beta-diketimine ligands are a versatile class of molecules that display an impressive range of diverse applications in coordination chemistry (Bourget-Merle et al. 2002). The success of these ligands (Stender et al. 2001) is presumably due to the scope for suitable tuning of the steric and electronic properties and due to its easy synthetic accessibility to coordinate to early transition metals (Hsu et al. 2004). Here we report the crystal structure of the Cu(II) complex containing a ketiminate ligand, [OC(Me)CHC(Me)NH (Ar)] where Ar = 4-bromophenyl. Structural analysis shows that the title compound crystallized as black cuboidal crystals in the monoclinic space group, P2₁/c, with one molecule in the asymmetric unit and with approximately non-crystallographic C2 symmetry. The complex shows a four coordinate environment around the copper atom where two ketimine ligands act as bidentate N,O-chelators and lie in the trans conformation to create two six-membered chelate rings (Cu—O—C—C—C—N). Similar structures are reported in literature and the bond distances and angles of this structure compare well to those in literature (Bryndin et al. 2008, Hsu et al. 2007, John et al.2007).

In this structure, the dihedral angles of the two coordinate planes, O1—Cu1—N2 and O2—Cu1—N1, are 24.1 (2)° and 21.1 (2)° respectively. Also, the Cu—O and Cu—N bond distances are all marginally unequal, hence suggesting distorted square-planer geometry around the Cu(II) center. In Figure 1, the Cu1—O1 and Cu1—O2 bond lengths are 1.911 (2) Å and 1.909 (2) Å while the Cu1—N1 and Cu1—N2 bond lengths were 1.958 (2) Å and 1.948 (2) Å respectively. The presence of the 4-bromophenyl group has caused a slight decrease in the Cu—N bond distances when compared to the respective analogues of copper ketimine complexes by Bryndin et al. 2008 (Cu—N = 1.960 (2) Å and 1.965 (2) Å) and Hsu et al. 2007 (Cu—N = 1.974 (1) Å and 1.974 (1) Å). Owing to the presence of the distortion, the four N—Cu—O bond angles are marginally different from the ideal value of a square planer geometry of 90° and are reported as 94.70 (8)° (N1—Cu1—O1) and 94.80 (8)° (N2—Cu1—O2). The diagonal angles, N1—Cu1—N2 and O1—Cu1—O2, are reported as 148.20 (9)° and 145.59 (8)° which also differ substantially from the ideal angle of 180° and are comparable to results reported by Bryndin et al. 2008 and Hsu et al. 2007.These differences were made apparent when comparing the results to the structures by John et al. 2007, where phenoxy-ketimine ligands were used as bidentate ligands for both Cu(II) and Ni(II), in which almost a perfect square planar geometry was obeserved. The stabilization is dominated by two intermolecular C—H···O hydrogen bonds (C115—H115···O1) 2.47 Å and C215—H215···O1 = 2.54 Å) (Table 2). π–π stacking is observed between neighbouring molecules with a centroid-to-hydrogen bond distance of 3.7236 (9) Å. Five pi-interactions (centroid-to-hydrogen) are observed with a distance varying between 3.527 (1) Å and 3.746 (1) Å. The hydrogen and pi-interactions as well as the pi–pi stacking is illustrated in Figure 2. The molecules pack in alternating layers along the c axis possibly due to the hydrogen- and π interactions.

Experimental

Copper nitrate Cu(NO₃)₂ (100 mg, 0.044 mmol) was dissolved in MeOH and refluxed with 2 equivalent of C₁₁H₁₁BrONH (237 mg, 0.94 mmol) for 2 h. The product was filtered at ambient temperature and dried in air. Black crystals were grown overnight from chloroform/ether (1:1, 10 ml) mixture. (yield: 169 mg, 0.29 mmol and 67%).