Dichlorido(3,5-dimethyl-1H-pyrazole)[(3,5-dimethyl-1H-pyrazol-1-yl)(o-tol­yl)methanone]palladium(II)

Simphiwe M Nelana; Gert J Kruger; James Darkwa

doi:10.1107/S1600536807066627

. 2007 Dec 18;64(Pt 1):m206–m207. doi: 10.1107/S1600536807066627

Dichlorido(3,5-dimethyl-1H-pyrazole)[(3,5-dimethyl-1H-pyrazol-1-yl)(o-tolyl)methanone]palladium(II)

Simphiwe M Nelana ^a, Gert J Kruger ^a,^*, James Darkwa ^a

PMCID: PMC2915136 PMID: 21200554

Abstract

In the title compound, [PdCl₂(C₅H₈N₂)(C₁₂H₁₂N₂O)], the Pd atom adopts a slightly distorted trans-PdCl₂N₂ square-planar arrangement. The different Pd—N bond lengths can be related to the the electron-withdrawing effect of the o-toluoyl group on the substituted pyrazole ligand. The complex crystallizes as centrosymmetric hydrogen-bonded dimers through N—H⋯Cl linkages.

Related literature

For related literature, see: Mukherjee (2000 ▶); Komeda et al. (2000 ▶); Li et al. (2002 ▶); Guzei et al. (2003 ▶); Guzei et al. (2005 ▶); Ojwach et al. (2005 ▶); Spencer et al. (2006 ▶); Allen (2002 ▶).

Experimental

Crystal data

[PdCl₂(C₅H₈N₂)(C₁₂H₁₂N₂O)]
M _r = 487.70
Orthorhombic,
a = 15.908 (3) Å
b = 15.479 (3) Å
c = 16.602 (3) Å
V = 4088.0 (12) Å³
Z = 8
Mo Kα radiation
μ = 1.18 mm⁻¹
T = 293 (2) K
0.32 × 0.28 × 0.15 mm

Data collection

Bruker SMART CCD diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2004 ▶) T _min = 0.703, T _max = 0.843
43509 measured reflections
4023 independent reflections
2686 reflections with I > 2σ(I)
R _int = 0.056

Refinement

R[F ² > 2σ(F ²)] = 0.040
wR(F ²) = 0.114
S = 1.08
4023 reflections
240 parameters
H-atom parameters constrained
Δρ_max = 1.09 e Å⁻³
Δρ_min = −0.49 e Å⁻³

Data collection: SMART-NT (Bruker, 1998 ▶); cell refinement: SAINT-Plus (Bruker, 1999 ▶); data reduction: SAINT-Plus; 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 ▶) and Mercury (Macrae et al., 2006 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶), PLATON (Spek, 2003 ▶) and publCIF (Westrip, 2008 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536807066627/hb2672sup1.cif

e-64-0m206-sup1.cif^{(21.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536807066627/hb2672Isup2.hkl

e-64-0m206-Isup2.hkl^{(193.3KB, hkl)}

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

Table 1. Selected geometric parameters (Å, °).

Pd1—N11	1.989 (4)
Pd1—N21	2.042 (4)
Pd1—Cl1	2.2981 (15)
Pd1—Cl2	2.3001 (15)

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N11—Pd1—N21	174.88 (15)
N11—Pd1—Cl1	88.39 (13)
N21—Pd1—Cl1	90.02 (12)
N11—Pd1—Cl2	89.98 (13)
N21—Pd1—Cl2	91.84 (12)
Cl1—Pd1—Cl2	176.71 (5)

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

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N12—H12A⋯Cl2ⁱ	0.86	2.35	3.194 (4)	169

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Symmetry code: (i) Inline graphic .

Acknowledgments

The authors thank the National Research Foundation (NRF South Africa) and the National Research Foundation – Department of Science and Technology, (South Africa) Centre of Excellence in Catalysis (c*change) for financial support, and the University of the Witwatersrand for the use of the diffractometers in the Jan Boeyens Structural Chemistry Laboratory.

supplementary crystallographic information

Comment

Pyrazole and pyrazolyl ligands have been used to form N-donor metal complexes with interesting catalytic applications (Mukherjee, 2000) and as mimics for imidazole coordination in metalloenzymes (Komeda et al., 2000). Catalytic behaviour of such N-donor metal complexes, in particular, depends on the nature of substituents on the pyrazolyl ligands. The introduction of dicarbonylbenzene linkers (Guzei et al., 2003) to bis(pyrazole)palladium complexes (Li et al., 2002), for instance, improves the activity of these complexes as ethylene polymerization catalysts. The presence of carbonyl functional groups in palladium complexes, however, reduces their stability as catalysts. We initially attributed the reduced stability to the effect of two carbonyl groups on the N-donor ability of the pyrazolyl ligands. In an attempt to improve the stability of the palladium catalysts, monocarbonylbenzene units were attached to pyrazolyl units to prepare the bis(pyrazolylcarbonylbenzene)palladium dichloride. Surprisingly, with (3,5-dimethyl-pyrazol-1-yl)-o-toluoyl-methanone as a ligand during complexation with PdCl₂, we isolated the title compound, (I), a mixed ligand palladium complex, containing (3,5-dimethyl-pyrazol-1-yl)-o-toluoyl-methanone and 3,5-dimethylpyrazole as ligands. The formation of compound I appears to occur via partial hydrolysis of one of the (3,5-dimethyl-pyrazol-1-yl)-o-toluoyl-methanone ligands, presumably by traces of water in the reaction mixture.

Compound (I) displays square planar geometry around the palladium atom, with the two different pyrazolyl ligands ((3,5-dimethyl-pyrazol-1-yl)-o-toluoyl-methanone and 3,5-dimethylpyrazole) bonding trans to the metal centre via N atoms (Fig. 1). The slight distortion of the square planar configuration around the palladium atom can be seen in the differences in bond angles involving palladium (Table 1) and the deviations from the least-squares plane through the central five atoms [Pd1 = -0.0116 (12) Å, Cl1 = -0.0684 (12) Å, Cl2 = -0.0665 (12) Å, N11 = 0.0754 (17) Å, N21 = 0.0711 (16) Å], with the biggest deviations being observed for the nitrogen atoms. The pyrazolyl rings of the coordinating ligands are roughly perpendicular to this central plane, with interplanar angles of 86.66 (12)° and 68.13 (14)° respectively. The Pd—Cl bond distances in (I) are similar to Pd—Cl distances in related complexes (e.g. Spencer et al., 2006) and consistent with the average of 2.33 (4)Å calculated for 2151 Pd—Cl distances in 1306 complexes reported to the Cambridge Structural Database (CSD, Version 5.26, updated May 2005; Allen 2002). One interesting feature of (I) is the significant difference of 0.053 Å in the Pd—N bond distances for the two ligands, illustrating the electron-withdrawing effect of the o-toluoyl-methanone substituent on the pyrazolyl ligand.

Intermolecular hydrogen bonding is responsible for the formation of centrosymmetric dimers through N—H···Cl linkages [Figure 2, Table 2]. In contrast to previous observations (Li et al., 2002), the hydrogen bonding in (I) has no effect on the bond order: we observed two virtually identical Pd—Cl bond lengths, although only Cl1 was involved in a N—H···Cl hydrogen bond.

Experimental

To a solution of [PdCl₂(NCMe)₂] (0.10 g, 0.47 mmol) in dichloromethane (30 ml), was added (3,5-dimethyl-pyrazol-1-yl)-o-toluoyl-methanone (0.06 g, 0.23 mmol). The formation of an orange-yellow solution was observed and the reaction mixture was stirred at room temperature for 24 h. The solution was then concentrated to 15 ml and an equal amount of hexane was added and kept at -4 °C for 3 days to yield yellow crystals suitable for X-ray analysis. Yield = 0.08 g, 59%. IR (Nujol): ν (C=O) = 1699. ¹H NMR (CDC_l3): δ 9.50 (s, 1H, N—H), 7.54 (m, 4H, o-toluoyl), 6.13 (s, 1H, 4-pz, o-toluoyl), 5.74 (s, 1H, 4-pz), 2.94 (s, 3H, o-toluoyl), 2.56 (s, 3H, 5-CH₃, o-toluoyl), 2.35 (s, 3H, 3-CH3, o-toluoyl), 2.31 (s, 3H, 5-CH₃,), 2.21 (s, 3H, 3-CH₃). ¹³C{¹H} NMR: δ 169.4, 157.4, 137.6, 133.3, 131.5, 128.4, 118.6, 106.5, 33.1, 32.4, 30.1.