[2,6-Bis(5-eth­oxy-1,3-oxazol-2-yl)-4-meth­oxy­phenyl-κ3 N,C 1,N′]bromidopalladium(II)

Wen-Hui Nan; Jian-Ping Tan; Qun-Li Luo

doi:10.1107/S1600536812049197

. 2012 Dec 8;69(Pt 1):m31–m32. doi: 10.1107/S1600536812049197

[2,6-Bis(5-ethoxy-1,3-oxazol-2-yl)-4-methoxyphenyl-κ³ N,C ¹,N′]bromidopalladium(II)

Wen-Hui Nan ^a, Jian-Ping Tan ^a, Qun-Li Luo ^a,^*

PMCID: PMC3588296 PMID: 23476330

Abstract

In the title compound, [PdBr(C₁₇H₁₇N₂O₅)], the Pd^II atom is coordinated by an N,C ¹,N′-tridentate pincer ligand and a Br atom in a distorted square-planar geometry. In the crystal, molecules are connected by C—H⋯Br and C—H⋯O hydrogen bonds, and π–π interactions between the oxazole and benzene rings [centroid–centroid distance = 3.7344 (19) Å], resulting in a three-dimensional supramolecular structure.

Related literature

For background to pincer palladium complexes, see: van Koten & Gebbink (2011 ▶); Moreno et al. (2010 ▶); Selander & Szabó (2011 ▶). For palladium complexes with NCN pincer ligands, see: Hao et al. (2010 ▶); Young et al. (2011 ▶). For studies on the chemistry of bis(oxazole) pincer palladium complexes, see: Luo et al. (2007 ▶, 2011 ▶); Xu et al. (2011 ▶). For structures of related bis(azole) pincer palladium complexes, see: Ghorai et al. (2012 ▶); Luo et al. (2012 ▶).

Experimental

Crystal data

[PdBr(C₁₇H₁₇N₂O₅)]
M _r = 515.64
Triclinic,
a = 9.0209 (3) Å
b = 9.6544 (3) Å
c = 10.9200 (3) Å
α = 87.093 (2)°
β = 86.974 (1)°
γ = 85.793 (2)°
V = 946.11 (5) Å³
Z = 2
Mo Kα radiation
μ = 3.12 mm⁻¹
T = 296 K
0.43 × 0.41 × 0.37 mm

Data collection

Bruker APEX CCD diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ▶) T _min = 0.347, T _max = 0.391
15776 measured reflections
4311 independent reflections
3770 reflections with I > 2σ(I)
R _int = 0.034

Refinement

R[F ² > 2σ(F ²)] = 0.036
wR(F ²) = 0.113
S = 1.08
4311 reflections
235 parameters
6 restraints
H-atom parameters constrained
Δρ_max = 0.72 e Å⁻³
Δρ_min = −1.25 e Å⁻³

Data collection: SMART (Bruker, 2007 ▶); cell refinement: SAINT (Bruker, 2007 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: XP in SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Click here for additional data file.^{(21.4KB, cif)}

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536812049197/hy2606sup1.cif

e-69-00m31-sup1.cif^{(21.4KB, cif)}

Click here for additional data file.^{(211.2KB, hkl)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812049197/hy2606Isup2.hkl

e-69-00m31-Isup2.hkl^{(211.2KB, hkl)}

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

Table 1. Selected bond lengths (Å).

Pd1—C11	1.954 (3)
Pd1—N1	2.056 (3)
Pd1—N2	2.055 (3)
Pd1—Br1	2.4941 (4)

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

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C2—H2A⋯Br1ⁱ	0.97	2.80	3.526 (5)	132
C16—H16A⋯O2ⁱⁱ	0.96	2.44	3.391 (5)	170

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

Acknowledgments

The authors appreciate financial support from the National Natural Science Foundation of China (grant No. 20971105) and the Fundamental Research Funds for the Central Universities (grant No. XDJK2012B011).

supplementary crystallographic information

Comment

Cross-coupling reactions catalyzed by palladium complexes are among the most important tools for C—C bond construction. Considerable attention has recently been devoted to pincer-Pd complexes due to their catalytic abilities (Ghorai et al., 2012; van Koten & Gebbink, 2011; Moreno et al., 2010; Selander & Szabó, 2011). We are interested in the NCN type of pincer-Pd complexes (Luo et al., 2007, 2011, 2012; Xu et al., 2011) as a variety of nonphosphine pincer catalytic system, that contains two nitrogen atoms as donating sites in the coordination sphere (Hao et al., 2010; Young et al., 2011)

The title compound was conveniently synthesized from the reaction of Pd(dba)₂ (dba = dibenzylideneacetone) with 1-bromo-2,6-bis(5-ethoxyoxazol-2-yl)-4-methoxy benzene in dry benzene under reflux in an argon atmosphere. As a result, the title compound was isolated with 84% yield. Suitable single crystals were grown via vapor diffusion of hexane into a DMF solution of the soluble reaction product at room temperature for dozens of days.

The molecular structure is shown in Fig. 1 and selected bond lengths in Table 1. In the crystal, the molecules are linked by intermolecular C—H···Br and C—H···O hydrogen bonds (Table 2) and π–π interactions between the oxazole and benzene rings [centroid–centroid distance = 3.7344 (19) Å], resulting in a three-dimensional supramolecular structure.

Experimental

Under an argon atmosphere, a 25 ml Schlenk flask was charged with 1-bromo-2,6-bis(5-ethoxyoxazol-2-yl)-4-methoxybenzene (106 mg, 0.3 mmol), Pd(dba)₂ (173 mg, 0.3 mmol) and dry benzene (15 ml). The reaction mixture was heated and refluxed for 2 h, and then cooled to room temperature and stirred for further 2 h. The resultant mixture was directly transferred on to a diatomite column and eluted first with hexane to remove dibenzylideneacetone and then with chloroform. The collected target compound was crystallized from CHCl₃/MeOH as a slight yellow solid (yield: 84%). ¹H NMR (300 MHz, CDCl₃): δ 6.76 (s, 2H), 6.52 (s, 2H), 4.25 (q, 4H, ³J = 6.9 Hz), 3.83 (s, 3H), 1.49 (t, 6H, ³J = 7.0 Hz). ¹³C NMR (75 MHz, CDCl₃): δ159.3, 158.5, 157.6, 154.7, 129.9, 107.3, 100.3, 55.8, 14.4. LRMS (ESI): m/z(%) 951 (100) (2M⁺–Br).