The crystal structures of cis- and trans-dichlorodiammineplatinum(II)

Complete three-dimensional X-ray crystal structure analyses have been carried out on both compounds by identical experimental and computational methods. Observations were collected at 120°± 5°K and the intensities corrected for absorption. Hydrogen atoms were not located. After anisotropic refinement by least-squares, R is 0·091 for the cis-isomer and 0·077 for the trans-isomer. The bond lengths, corrected for rotational oscillation are Pt–Cl = 2·33 ± 0·01 A and Pt–N = 2·01 ± 0·04 A in the cis-compound, and Pt–Cl = 2·32 ± 0·01 A and Pt–N = 2·05 ± 0·04 A in the trans-compound. The only angle significantly different from 90° is Cl–Pt–Cl = 91·9°± 0·4° in the cis-compound.The crystals of cis-dichlorodiammineplatinum are triclinic with two molecules in a unit cell having a= 6·75, b= 6·55, c= 6·23 A, α= 92·2°, β= 84·6°, and γ= 110·7°, and space group P. The molecules lie approximately parallel to (100) at x/a∼¼ and ∼¾, with platinum–platinum separations alternately 3·372 and 3·409 A perpendicular to the molecular planes. At low temperature the structure of the trans-isomer is essentially the same as that at room temperature reported by Porai-Koshits.