Structures of [Pd(NH₃)₂ X ₂] and its chemical transformation in the solid state

Abstract

Crystal structures of [Pd(NH3)2X2] complexes, where X = Br or I, diamminediiodo-/-dibromopalladium(II), have been studied by X-ray powder diffraction. The series consists of five complexes: cis-[Pd(NH3)2Br2] (I) [a = 13.3202 (7), b = 12.7223 (6), c = 7.05854 (3) A, Z = 8, space group Pbca], trans-[Pd(NH3)2Br2] (II) [a = 6.7854 (3), b = 7.1057 (3), c = 6.6241 (2) A, alpha = 103.221 (3), beta = 102.514 (2), gamma = 100.386 (3) degrees, Z = 2, space group P1], beta-trans-[Pd(NH3)2Br2] (III) [a = 8.4315 (3), b = 8.4206 (3), c = 8.0916 (2) A, Z = 4, space group Pbca], cis-[Pd(NH3)2I2] (IV) [a = 13.9060 (8), b = 13.5035 (8), c = 7.5050 (4) A, Z = 8, space group Pbca], and beta-trans-[Pd(NH3)2I2] (V) [a = 8.8347 (5), b = 8.8410 (5), c = 8.6081 (2) A, Z = 4, space group Pbca]. Patterson synthesis and Rietveld refinement have been used for structural determination. Molecular structures with column- or parquet-type packing of flat complexes are characteristic of these substances. Corresponding cis- and beta-trans compounds are isostructural. The thermal transformations cis-->trans-->beta-trans (cis-->beta-trans in the case of iodine) are considered. Cl derivatives are also discussed. The transformations proceed irreversibly and are accompanied by decreasing specific volume. Owing to these features, they can be classified as chemical reactions. High-temperature X-ray powder diffraction was used to study the transformations in air. The set of data is consistent with a solid state transformation from cis to trans. According to this model, the columns of molecules remain intact during the process, and the transformation proceeds via the breaking of Pd...X and Pd...N intermolecular bonds. The powder diffraction data have been deposited in ICDD-JCPDS (45-0596, 46-0876, 46-0879, 47-1690, 48-1185).

Organometallic chemistry in the melt phase

“…All peaks originating from [PtCl(NCN-OH)] were absent. Exposure of a sample of the adduct to air completely reversed the process of this selective inclusion of SO 2 into these arylplatinum structures which involved successive making and breaking of Pt-SO 2 -Cl interactions (Table 4 - 39). Because the process of SO 2 gas absorption/desorption is fully reversible over many 'on/off' cycles without any material deterioration, and is accompanied by a distinct color change the authors have proposed its application as a 'molecular switch' for SO 2 sensing.…”

“…The authors concluded that the cis ! trans transformation was not just a transition between the phases but occurred through the breaking of Pd-N or Pd-X bonds to finally yield the thermodynamic products (Table 3 -32) [39].…”

“…The four coordinate compounds cis-[Pd(NH 3 ) 2 X 2 ] have been prepared by a mechanochemical route from [Pd(NH 3 ) 2 C 2 O 4 ] and HX (X = Br, I) ( Table 1 -2) [39]. Mechanochemistry has also been used to activate complexes.…”

Osteogenic effect of low‐temperature‐heated porcine bone particles in a rat calvarial defect model

“…Even if the chemical composition of two materials is the same, the crystal structure may be markedly different. In XRD, a wide peak means low crystallinity, and a narrow peak means high crystallinity . In this study, P400 and P1200 showed the hydroxyapatite peaks and P400 showed a wider peak, indicating a lower crystallinity than P1200.…”

Organometallic Chemistry: Structural Isomerization Reactions in Confined Environments

“…In this specific case the reaction proceeds from the cis to the trans isomer in a process that entails the ''breaking of PdϪX and PdϪN bonds''. [29] Numerous sixcoordinate Cr and Co compounds have also been studied. [30] It appears that the presence of water assists the cis/trans isomerization reaction of Co complexes, with dehydration playing a key role.…”