[(4-Bromo­phen­yl)(2-pyridyl­methyl­idene)amine-κ2 N,N′]bis­(1,1,1,5,5,5-hexa­fluoro­pentane-2,4-dionato-κ2 O,O′)cobalt(II)

Phimphaka Harding; David J Harding; Nitisastr Soponrat; Harry Adams

doi:10.1107/S1600536810032757

. 2010 Aug 21;66(Pt 9):m1138–m1139. doi: 10.1107/S1600536810032757

[(4-Bromophenyl)(2-pyridylmethylidene)amine-κ² N,N′]bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato-κ² O,O′)cobalt(II)

Phimphaka Harding ^a,^*, David J Harding ^a, Nitisastr Soponrat ^b, Harry Adams ^c

PMCID: PMC3008124 PMID: 21588537

Abstract

In the title complex, [Co(C₅HF₆O₂)₂(C₁₂H₉BrN₂)], the Co^II atom exhibits a pseudo-octahedral coordination geometry, comprising two N-donor atoms from a bidentate chelate (4-bromophenyl)(2-pyridylmethylidene)amine (ppa^Br) ligand [Co—N = 2.098 (2) and 2.209 (2) Å] and four O-donor atoms from two bidentate chelate 1,1,1,5,5,5-hexafluoropentane-2,4-dionate (hfac) ligands [Co—O range = 2.0452 (19)–2.0796 (19) Å]. The packing of the structure involves weak π–π interactions between the pyridyl and benzene rings of neighbouring ppa^Br ligands [centroid–centroid distance = 3.928 (2) Å] and interactions between the Br atom on the ppa^Br ligand and the hfac ligand [Br⋯C = 3.531 (2) Å].

Related literature

For a review of halogen bonding, see: Corradi et al. (2000 ▶); Walsh et al. (2001 ▶); Liantonio et al. (2003 ▶). For an introduction to crystal engineering, see: Braga et al. (2002 ▶). For related structures, see: Harding, Harding, Sophonrat & Adams (2010 ▶); Harding, Harding, Tinpun et al. (2010 ▶); Aäkeroy et al. (2004 ▶, 2007 ▶). For a description of the Cambridge Structural database, see: Allen et al. (2002 ▶).

Experimental

Crystal data

[Co(C₅HF₆O₂)₂(C₁₂H₉BrN₂)]
M _r = 734.17
Triclinic,
a = 8.3568 (2) Å
b = 10.9420 (2) Å
c = 14.8151 (3) Å
α = 74.042 (1)°
β = 86.510 (1)°
γ = 77.080 (1)°
V = 1269.51 (5) Å³
Z = 2
Mo Kα radiation
μ = 2.37 mm⁻¹
T = 150 K
0.60 × 0.30 × 0.03 mm

Data collection

Bruker SMART CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 1997 ▶) T _min = 0.330, T _max = 0.932
21525 measured reflections
5176 independent reflections
4508 reflections with I > 2σ(I)
R _int = 0.021

Refinement

R[F ² > 2σ(F ²)] = 0.035
wR(F ²) = 0.090
S = 1.08
5176 reflections
379 parameters
H-atom parameters constrained
Δρ_max = 1.23 e Å⁻³
Δρ_min = −0.91 e Å⁻³

Data collection: SMART (Bruker, 1997 ▶); cell refinement: SAINT (Bruker, 1997 ▶); data reduction: SAINT; 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: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810032757/zs2056sup1.cif

e-66-m1138-sup1.cif^{(25.2KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810032757/zs2056Isup2.hkl

e-66-m1138-Isup2.hkl^{(253.4KB, hkl)}

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

Acknowledgments

We thank the Thailand Research Fund (grant No.: RSA5080007) for funding this research.

supplementary crystallographic information

Comment

The construction of supramolecular networks with designed architectures still remains the goal of crystal engineering and represents a significant challenge (Braga et al., 2002). Although complementary hydrogen-bonding ligands have been successfully used (Aäkeroy et al., 2004) in the construction of a number of networks, halogen-bonding (Walsh et al., 2001; Liantonio et al., 2003) and halogen···halogen interactions remain less well represented despite the fact that these interactions can be as strong as hydrogen-bonding interactions (Corradi et al., 2000). In this paper we report the synthesis and structure of [Co(hfac)₂(ppa^Br)] [hfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dionato; ppa^Br = (4-bromo-phenyl)pyridin-2-ylmethyleneamine].

The reaction of [Co(hfac)₂(H₂O)₂] with ppa^Br in CH₂Cl₂ yields [Co(hfac)₂(ppa^Br)] (I) (Fig. 1) which crystallizes from CH₂Cl₂/hexane. In (I) the cobalt metal centre is six-coordinate with a distorted octahedral geometry, the hfac ligands adopting a cis arrangement enforced by the chelating ppa^Br ligand. The CF₃ groups of the hfac ligand in some cases exhibit large thermal ellipsoids due to thermal motion of these groups. The Co—N and Co—O bond lengths are comparable with related cobalt hfac and diimine complexes reported in the CSD (Allen, 2002) (mean Co—O distance = 2.01 Å, Co—N distance = 2.11 Å). The β-diketonate ligands exhibit a bent coordination mode in which the angles between the planes defined by the Co and oxygen atoms and the carbon and oxygen atoms of the β-diketonate ligand are 18.9° and 24.7°. In contrast, in trans-[M(hfac)₂(py-CH=CH—C₆F₄Br)₂] (M = Co, Cu) the β-diketonate ligands exhibit a planar coordination mode (Aäkeroy et al., 2007). In addition, the phenyl ring is twisted with respect to the pyridylimine unit by 17.6° and is similar to the angle observed in [Ni(dbm)₂(ppa^X)] [X = Me, 22.9°; Cl, 24.0° (Harding, Harding, Tinpun et al., 2010)].

The packing in the structure of (I) involves a weak π–π interaction between the pyridyl and phenyl rings of neighbouring ppa^Br ligands as shown in Fig. 2 (Cg1···Cg2 = 3.928 (2) Å where Cg1 and Cg2 are the centroids of the rings C1—C6 and C8—C12—N2). A further weak interaction occurs between the Br atom on the ppa^Br ligand and the β-diketonate ligand creating discrete dimers within the structure [Br···C20, 3.531 (2) Å, see Fig. 3]. These dimers are then connected via the π–π interaction mentioned above resulting in one-dimensional chains. A similar interaction is also observed in the structure of trans-[M(hfac)₂(py-CH=CH—C₆F₄Br)₂] (Aäkeroy et al., 2007). Interestingly, the corresponding Ni analogue, [Ni(hfac)₂(ppa^Br)] has a completely different set of interactions with Br···CH interactions clearly evident (Harding, Harding, Sophonrat & Adams, 2010), once again highlighting the difficulties involved in attempting to use specific interactions in the design of supramolecular networks.

Experimental

To an orange red solution of [Co(hfac)₂(H₂O)₂] (0.127 g, 0.25 mmol) in CH₂Cl₂ (5 cm³) was added a solution of ppa^Br (0.065 g, 0.25 mmol) in CH₂Cl₂ (3 cm³). The deep orange solution was stirred for 1 h and then concentrated in vacuo. n-Hexane (15 cm³) was added to precipitate an orange solid which was washed with n-hexane (2 x 5 cm³) and dried in vacuo: yield 0.142 g (77%). IR in KBr disc ν_C=O 1647 cm^-1. UV-Vis (in CH₂Cl₂, log ε mol.dm^-3cm^-1) 243 (4.24), 309 (4.42). C₂₂H₁₁O₄N₂F₁₂BrCo; calc. C 36.0, H 1.5, N 3.8%; found C 36.5, H 1.5, N 3.8%.