Structures and isomerization in diamminedichloropalladium(II)

Abstract

Three forms (cis-, trans-, /3-trans-) of [Pd(NH3)2CI2] were obtained as pure single-phase powder materials. Ab initio structure determinations using X-ray powder diffraction were carried out. The cis-Pd(NH3)2C12 [a = 6.3121(2), b = 6.4984 (2), c= 3.3886(1)A, ot = 96.604(4), /3=97.290(4), y= 104.691(2y ~, Z= 1, space group P1] and trans-Pd(NH3)2C12 [a = 6.5398 (3), b=6.8571 (4), c=6.3573 (3) A, t~ = 103.311 (5), 15 --102.454 (3), y = 100.609 (4) °, Z = 2, space group P1] phases have a typical layer-column structure, while /3-trans-Pd(NH3)2Cl 2 [a --8.1540 (2), b = 8.1482(2), c = 7.7945 (1)A, Z = 4, space group Pbca] is described as a parquet-like layer structure. Both trans phases demonstrate the order-disorder phenomenon. The possible ways of phase transitions are discussed. It is noted that the cis phase can transform into trans in the solid state without destroying the crystal body. Further transformation to /3-trans follows through a break up of the crystal body. The result was a fine yellow powder. Chemical analysis: Pd 50.50 (50.40), C1 33.41 (33.49)%. The trans compound could also be prepared by thermal transformation of cis-[Pd(NH3)2C12)] at --~523 K, but in this case the product is contaminated by other isomers. fl-trans-[Pd(NH3)2C12) ] was obtained by thermal transformation of trans-[Pd(NH3)2C12)]. The latter compound was heated in water at 363-368 K for 4h. The orange coloured product was washed and dried. Chemical analysis: Pd 50.45 (50.40), C1 33.40 (33.49)%. The trans isomer is insoluble in water.

A correction for anisotropic line broadening due to structural defects in powder diffraction structure analysis

“…The crystals of the -trans phase are orthorhombic (pseudotetragonal) and consist of the same planar complexes as in the trans phase but with a different arrangement. The presence of layer defects in -trans-[Pd(NH 3 ) 2 Cl 2 ] has already been discussed by Kirik et al (1996). A similar phenomenon is also revealed in the bromide and iodide compounds (Kirik et al, 1998).…”

“…The problem of selective peak broadening in trans-[Pd(NH 3 ) 2 Cl 2 ] has already been discussed by Kirik et al (1996). The structural investigations of trans-[Pd(NH 3 ) 2 Br 2 ] revealed the same phenomenon (Kirik et al, 1998).…”

“…To diminish the problem of broadening, the most broadened peaks were initially given the FWHM (full width at half-maximum) values estimated from the experimental pro®le, as performed by Kirik et al (1996). This allowed a satisfactory full-pro®le ®tting and the calculation of the difference E map.…”

Conformational insights and vibrational study of a promising anticancer agent: the role of the ligand in Pd(ii)–amine complexes

“…The theoretical estimate of the chelate's structural parameters is of the utmost importance for the prediction of reliable SARs for the complex. When comparing the experimental bond lengths for different compounds of the same type, it is interesting to verify that within Pd 2 -Spm, the Pd-N bonds (203.2 pm average value, Table 2) are shorter relative to the parent mononuclear compound cDDPd (206.0 pm), 35 while the Pd-Cl ones are longer (231.5 pm vs. 227.5 pm). 35 Natural bond orbital (NBO) calculations through the calculated Wiberg bond indices -an indicator that reflects the strength of the bond -also predict this trend, which is interestingly correlated with the biological activity of the complexes involved (Fig.…”

Conformational and vibrational study of cis-diamminedichloropalladium(ii)

“…The compound was filtered, washed with ethanol and let to dry. Powder X-ray was performed and compared to the data reported by Kirik et al, 14 confirming the presence of the cis isomer.…”