Crystal structure of diammonium bis(oxalato)palladium(II) dihydrate, (NH4)2[Pd(C2O4)2] · 2H2O

Abstract

C 4 H 12 N 2 O 10 Pd, monoclinic, P12 1 /c1(no. 14), a =6.7795(7) Å, b =14.377(2) Å, c =6.1774(7) Å, b =111.052(1)°, V =561.9 Å 3 , Z =2,Rgt(F) =0.018, wRref (F 2 ) =0.048, T =298 K. Source of materialTo asolution of palladium(II) chloride (0.89 g, 5.0 mmol) in dilute hydrochloric acid (2 M, 6mL), ammonium oxalate (1.86 g, 15.0 mmol) in 10 mL of distilled water was added. The resulting solution was stirred for 1hat60°C, and then the pH was adjusted to 5.5 by adding dilute sodium hydroxide solution. After cooling to room temperature, ayellow prodct precipitated from the solution. The product was filtrated, washed with ice-cold water, and dried under vaccuum at 70°C. The crystals suitable for crystallographic studies were obtained by slow evaporation from the aqueous solution of the product at room temperature. Experimental detailsAll Hatoms were found in difference Fourier maps and refined independently. DiscussionThe crystal structure of the title complex comprises discrete ammonium cations, [Pd(C 2 O 4 )] 2-anions and water molecules (figure, top). The Pd atom occupying the inversion centre is coordinated in as lightly distorted square manner by the four oxygen atoms of two oxalate ligands. The average Pd-Od istance is 2.000(2) Å,w hile the angles O1-Pd-O2 and the O1-Pd-O2A are 83.64(6)°and 96.36(6)°,r espectively. All of these agree well with the data of related palladium complexes [1,2]. The C1-O1 and C2-O2 bond length are 1.289(3) and 1.291(3) Å,r espectively, while the C1-O3 and C2-O4 bond length are 1.222(3) and 1.217(3) Å,respectively, which indicate a monodentate coordination mode for the carboxylates [3,4]. The crystal packing of the title complex is stablilized by extensive hydrogen bonds formed between ammonium cations, water molecules and Oatoms of the oxalates with d(O···O) of 2.951(3) Å and 2.888(3) Å,a nd d(N···O) of 2.910(3), 2.983(3), 2.935(3), 2.865(3) and 2.871(3) Å (figure, bottom). The mean planes defined by the four coordinated Oatoms are parallel to each other along [001] with adistance of 3.356 Å between the nearest neighbors, and the distance Pd···Pd is 6.177 Å.