Di-μ-chlorido-bis­{[2-(morpholinometh­yl)phenyl-κ2 C 1,N]palladium(II)}

Dana Copolovici; Cristian Silvestru; Francesco Isaia; Richard A Varga

doi:10.1107/S1600536808022575

. 2008 Jul 23;64(Pt 8):m1057–m1058. doi: 10.1107/S1600536808022575

Di-μ-chlorido-bis{[2-(morpholinomethyl)phenyl-κ² C ¹,N]palladium(II)}

Dana Copolovici ^a, Cristian Silvestru ^a, Francesco Isaia ^b, Richard A Varga ^a,^*

PMCID: PMC2961971 PMID: 21203041

Abstract

The title compound, [Pd₂(C₁₁H₁₄NO)₂Cl₂], has a dimeric structure with Cl atoms bridging the two Pd atoms, one half of the molecule being generated by symmetry due to the crystallographic inversion centre located in the middle of the perfectly planar Pd₂Cl₂ ring. The five-membered ring adopts an envelope conformation, while the morpholino group has a chair conformation. The geometry around the metal centres is distorted square-planar, as a result of a strong intramolecular N→Pd coordination trans to a Pd—Cl bond. In the crystal structure, the dimeric structure is strengthened by intermolecular C—H⋯Cl hydrogen bonds. C—H⋯C_phenyl interactions link the dimers into a columnar supramolecular array along the a axis; the dimers are further connected by C—H⋯Ph interactions into a three-dimensional supramolecular arrangement.

Related literature

For related literature, see: Copolovici et al. (2007 ▶, 2008 ▶); Crispini et al. (1992 ▶); Fuchita et al. (1999 ▶); Mahalakshmi et al. (2003 ▶); Mentes et al. (1997 ▶, 2004 ▶, 2005 ▶); Phadnis et al. (2002 ▶, 2003 ▶); Emsley (1994 ▶); IUPAC (1979 ▶).

Experimental

Crystal data

[Pd₂(C₁₁H₁₄NO)₂Cl₂]
M _r = 636.20
Monoclinic,
a = 8.1234 (6) Å
b = 16.4437 (13) Å
c = 8.8298 (7) Å
β = 101.9570 (10)°
V = 1153.88 (15) Å³
Z = 2
Mo Kα radiation
μ = 1.81 mm⁻¹
T = 297 (2) K
0.22 × 0.17 × 0.17 mm

Data collection

Bruker SMART APEX CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2000 ▶) T _min = 0.677, T _max = 0.733
9118 measured reflections
2354 independent reflections
2245 reflections with I > 2σ(I)
R _int = 0.026

Refinement

R[F ² > 2σ(F ²)] = 0.028
wR(F ²) = 0.059
S = 1.15
2354 reflections
137 parameters
H-atom parameters constrained
Δρ_max = 0.49 e Å⁻³
Δρ_min = −0.43 e Å⁻³

Data collection: SMART (Bruker, 2000 ▶); cell refinement: SAINT-Plus (Bruker, 2001 ▶); 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, 2006 ▶); software used to prepare material for publication: publCIF (Westrip, 2008 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808022575/hk2489sup1.cif

e-64-m1057-sup1.cif^{(17.7KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808022575/hk2489Isup2.hkl

e-64-m1057-Isup2.hkl^{(115.7KB, hkl)}

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

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

Cl1—Pd1	2.3232 (8)
Cl1—Pd1ⁱ	2.4815 (8)
N1—Pd1	2.118 (2)
C1—Pd1	1.971 (3)

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Cl1—Pd1—Cl1ⁱ	82.66 (3)
N1—Pd1—Cl1	174.34 (7)
N1—Pd1—Cl1ⁱ	102.76 (6)
C1—Pd1—Cl1	92.88 (9)
C1—Pd1—Cl1ⁱ	175.53 (9)
C1—Pd1—N1	81.69 (11)
Pd1—Cl1—Pd1ⁱ	97.34 (3)
C7—N1—Pd1	104.01 (17)
C8—N1—Pd1	117.35 (18)
C11—N1—Pd1	111.92 (17)

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Symmetry code: (i) Inline graphic .

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

Cg is the centroid of the C1–C6 ring.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C9—H9B⋯Cl1ⁱ	0.97	2.49	3.370 (3)	150
C7—H7B⋯C1ⁱⁱ	0.97	2.67	3.588 (4)	159
C11—H11A⋯Cgⁱⁱⁱ	0.97	2.93	3.829 (3)	154

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

Acknowledgments

Financial support from the Romanian Ministry of Education and Research within the programme ‘Excellency Research’ (contract No. 19/2006) is greatly appreciated. The authors also thank the National Center for X-ray Diffraction in Cluj-Napoca, Romania, for help with the solid-state structure determinations.

supplementary crystallographic information

Comment

There are scarce data reported upon the reactivity of triorganoantimony(III) compounds toward palladium(II) chloride or corresponding complexes. The compounds of the type [PdCl₂(SbR₃)₂], R = ⁱPr (Phadnis et al., 2002), ortho-tolyl (Mentes & Fawcett, 2005), were obtained by reaction of [PdCl₂(COD)], COD = cycloocta-1,5-diene, with the corresponding stibines. The reaction of [PdCl₂(PhCN)₂] with SbR₃ (R = 2-thienyl) resulted in a black insoluble powder (possible Pd metal) due to a decomposition process (Mahalakshmi et al., 2003), whilst the reaction of [PdCl₂(PhCN)₂] with tri(allyl)stibine and tris(2-methylallyl)stibine afforded the transmetalation products [Pd₂(µ-Cl)₂R₂], R = allyl, 2-methylallyl, and the fate of the stibine residue is unknown (Phadnis et al., 2003). Reaction of SbPh₃with [PdCl₂(COD)] or PdCl₂afforded trans-[PdCl(σ-Ph)(SbPh₃)₂] due to the easy cleveage of Sb—C bond in SbPh₃, whilst reaction of Na₂PdCl₄with SbPh₃gave cis-[PdCl₂(SbPh₃)₂] contaminated with small amount of chloro σ-phenyl complex (Mentes et al., 1997). Related to our interest on the synthesis and chemical properties of organoantimony(III) compounds, we performed the reaction between Sb[C₆H₄CH₂{N(CH₂CH₂)₂O}-2]₃ and [PdCl₂(MeCN)₂] in acetonitrile/chloroform mixture, at room temperature.

The title compound has a dimeric structure, with two palladacycles bridged through the chlorine atoms, resulting in a perfectly planar Pd₂Cl₂ core. One half of the molecule is generated by symmetry owing the crystallographic inversion centre located in the middle of the Pd₂Cl₂ ring. The cycle is distorted from the ideal square as reflected by the diferences in the Pd—Cl bond lengths and the Cl1—Pd1—Cl1ⁱ and Pd1—Cl1—Pd1ⁱ bond angles (Table 1) [symmetry code: (i) = 1 - x, 1 - y, -z].

The N atom from the pendant arm coordinates the metal centre resulting in a square planar (C,N)PdCl₂ core, in which the distortion is mainly due to the PdC₃N ring constraint. The two equivalent organic ligands from the dimer are in a trans arrangement with respect to the Pd···Pd axis (Fig. 1). The Pd1—C1 [1.971 (2) Å] bond is smaller than the sum of the corresponding covalent radii, its magnitude being similar to those found for related compounds for which partialy Pd—C multiple bond was assumed (Crispini et al., 1992, Fuchita et al., 1999, Mentes et al., 2004).

An almost ideal chair conformation was observed for the morpholinyl groups with torsion angles [C8—N1—C11—C10 = -52.6 (3)° and C10—O1—C9—C8 = 58.4 (3)°] similar with those found in 4-benzylmorpholin-4-ium chloride (Copolovici et al., 2007) and in tris[2-(morpholin-4-ylmethyl)phenyl -κ²C¹,N]αntimony(III) (Copolovici et al., 2008).

As a result of the intramolecular coordination of the N1 atom from the organic ligand to Pd1 atom, a nonplanar five-membered ring is formed, with nitrogen atom lying out of the Pd1/C1/C2/C7 best plane [0.666 (2) Å]. The dihedral angle between the Pd1/N1/C7 and Pd1/C1/C2/C7 planes is 39.2 (1)°. This induces planar chirality (with the aromatic ring and the nitrogen atom as chiral plane and pilot atom, respectively, IUPAC, 1979). In the crystal of the title compound, the dimer contains both R_N and S_Nⁱ isomers.

In the crystal structure, the dimer is strengthened by hydrogen-bond type interactions (Table 2) involving the Cl from one molecular unit and the methylenic proton of the morpholinyl group from the other molecular unit from the same dimer [the sum of van der Waals radii of the corresponding atoms Σr_vdW(Cl,H) = 3.00 Å; Emsley, 1994] (Fig. 2).

Intermolecular C—H···C_phenyl interactions (Table 2) between a methylene hydrogen from the pendant arm and a carbon atom from the aromatic ring of another dimer connect the molecular units in a columnar arrangement along the a axis. Furthermore, these arrays are interlinked by intermolecular C—H···Ph interactions (Table 2) in a three-dimensional supramolecular arrangement in the crystal structure (Fig.3).

Experimental

For the preparation of the title compound, PdCl₂ (0.1 g, 0.56 mmol) in acetonitrile (40 ml) was refluxed for 3 h, and then allowed to cool to room temperature. A solution of Sb[C₆H₄CH₂{N(CH₂CH₂)₂O}-2]₃ (0.369 g, 0.56 mmol) in CHCl₃ (35 ml) was added and the mixture was stirred at room temperature for 30 h, under an N₂ atmosphere. The reaction mixture was filtered off and the solvents were removed under vacuum. The yellow oil obtained was triturated with hexane (2 x 20 ml) and then washed with petroleum ether (2 x 10 ml) to give a yellow solid. Yellow crystals suitable for X-ray diffraction studies were obtained by slow diffusion of hexane into a solution of CH₂Cl₂ of the title compound (1:1 v/v ratio) (yield: 0.217 g, 47%). Anal. Found: C, 41.38; H, 4.63; N, 4.73. Calc. for C₂₂H₂₈Cl₂N₂O₂Pd₂ (636.22): C, 41.53; H, 4.44; N, 4.40%. FT—IR (KBr, cm^-1): C—H stretch aromatic: 3038, 3035, 2958, 2891; 2857, 1436, 1114, 1069, 868, 745.