Bis(hydrogen l-glutamato)palladium(II)

Antje Seifert; Christoph Wagner; Kurt Merzweiler

doi:10.1107/S1600536811035860

. 2011 Sep 14;67(Pt 10):m1362. doi: 10.1107/S1600536811035860

Bis(hydrogen l-glutamato)palladium(II)

Antje Seifert ^a, Christoph Wagner ^a, Kurt Merzweiler ^a,^*

PMCID: PMC3201544 PMID: 22065700

Abstract

In the title compound, [Pd(C₅H₈NO₄)₂], the Pd(II) atom is coordinated by two O atoms and two N atoms of two N,O-chelating hydrogen l-glutatmate ligands in a square–planar geometry with the N and O atoms in a mutually trans arrangement. The complex units are embedded in a network of N—H⋯O and O—H⋯O hydrogen-bonding interactions that stabilize the three-dimensional crystal structure. The strongest hydrogen bonds are formed between the γ-COOH untis of adjacent glutamate ligands, leading to dimers of the type R ₂ ²(8) with O⋯O separations of 2.640 (6) Å.

Related literature

For the synthesis of the title compound, see: Spacu & Scherzer (1962 ▶). For the structures of related palladium complexes with amino acid ligands, see: Vagg (1979 ▶); Jarzab et al. (1973 ▶); Sabat et al. (1979 ▶); Pletnev et al. (1992 ▶); Hao et al. (2007 ▶); Gao et al. (2008 ▶).

Experimental

Crystal data

[Pd(C₅H₈NO₄)₂]
M _r = 398.66
Triclinic,
a = 4.8858 (3) Å
b = 5.1605 (4) Å
c = 13.3651 (9) Å
α = 93.725 (6)°
β = 99.734 (6)°
γ = 104.245 (6)°
V = 319.90 (4) Å³
Z = 1
Mo Kα radiation
μ = 1.49 mm⁻¹
T = 200 K
0.17 × 0.06 × 0.04 mm

Data collection

Stoe IPDS 2T diffractometer
Absorption correction: integration (X-RED; Stoe & Cie, 2009 ▶) T _min = 0.806, T _max = 0.973
4724 measured reflections
2406 independent reflections
2389 reflections with I > 2σ(I)
R _int = 0.044

Refinement

R[F ² > 2σ(F ²)] = 0.029
wR(F ²) = 0.066
S = 1.04
2406 reflections
208 parameters
9 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.37 e Å⁻³
Δρ_min = −0.74 e Å⁻³
Absolute structure: Flack (1983 ▶), 1146 Friedel pairs
Flack parameter: −0.02 (4)

Data collection: X-AREA (Stoe & Cie, 2009 ▶); cell refinement: X-AREA; data reduction: X-RED (Stoe & Cie, 2009 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: DIAMOND (Brandenburg, 2009 ▶); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, publication_text. DOI: 10.1107/S1600536811035860/wm2526sup1.cif

e-67-m1362-sup1.cif^{(18.1KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811035860/wm2526Isup2.hkl

e-67-m1362-Isup2.hkl^{(118.2KB, hkl)}

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

Table 1. Selected bond lengths (Å).

Pd—N1	2.072 (9)
Pd—N2	2.005 (11)
Pd—O1	1.976 (8)
Pd—O5	2.024 (7)

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

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N2—H9⋯O6ⁱ	0.85 (2)	2.15 (4)	2.979 (15)	162 (8)
N2—H10⋯O5ⁱⁱ	0.85 (2)	2.43 (8)	3.121 (13)	138 (10)
O7—H16⋯O4ⁱⁱⁱ	0.85 (2)	1.80 (2)	2.639 (6)	169 (7)
O3—H8⋯O8^iv	0.86 (2)	1.79 (3)	2.640 (6)	167 (7)
N1—H1⋯O2^v	0.85 (2)	2.15 (3)	2.996 (15)	170 (9)
N1—H2⋯O1^vi	0.85 (2)	2.30 (8)	2.998 (13)	139 (10)
N1—H2⋯O5^vii	0.85 (2)	2.42 (7)	3.117 (13)	140 (10)

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) ; (v) ; (vi) ; (vii) .

supplementary crystallographic information

Comment

The title compound, [Pd(C₅H₈NO₄)₂] (I), consists of a palladium(II) atom which is coordinated by two N and two O atoms of two chelating hydrogen glutamate ligands. The metal atom adopts a distorted square–planar coordination with the two N atoms and the two O atoms in mutual trans arrangements. The maximum deviation from the least squares plane through the atoms Pd, N1, N2, O1 and O5 is 0.026 Å for N2. The distances Pd—O (1.976 (8), 2.024 (7) Å) and Pd—N (2.005 (11), 2.072 (9) Å) are in agreement with the values observed for other Pd(II) amino acid derivatives, like cis-bis(L-tyrosinato)-palladium(II) hemihydrate (Jarzab et al., 1973), bis(L-tyrosinato)-palladium(II) (Sabat et al., 1979), bis(L-valinato)-palladium(II) monohydrate (Pletnev et al., 1992); Hao et al., 2007), cis-bis(L-aspartato-N,O)-palladium(II) (Gao et al., 2008) or bis(L-serinato)-palladium(II) (Vagg, 1979). For both the hydrogen glutatmate ligands, the five membered PdNC₂O chelate rings adopt envelope conformations with a nearly coplanar arrangement of the Pd, O, C and N atoms at the flap positions.

The main conformational difference between both chelate rings arises from the orientation of the carboxyethyl groups. In the case of C2 the carboxyethyl group is in an axial position and for C7 an equatorially arrangend carboxyethyl group is observed (Fig. 1).

The packing of the complex units is supported by different types of hydrogen bonding interactions. The strongest hydrogen bridges are formed between the γ-carboxyl groups of neighbouring molecules. Consequently, R₂²(8) motifs are observed and the complex units are arranged in chains. Additionally, there are N—H···O hydrogen bridges of the type C₁¹(4) and C₁¹(5) which are formed between amino groups and oxygen atoms of adjacent α-carboxylate groups (Fig. 2)

Experimental

The title compound was prepared from K₂PdCl₄ and sodium hydrogen glutamate according to a procedure described by Spacu & Scherzer (1962). For the growth of single crystals, the reaction mixture was stored at 278 K for several weeks.