STRUCTURE OF THE MIXED-VALENCE PLATINUM COMPLEXES PTII(EN)(SCN)2 PTIV(EN)(SCN)2I2 AND CIS- PTII(NH3)2(SCN)2 PTIV(NH3)2(SCN)2I2 STUDIED BY THE METHOD OF RADIAL-DISTRIBUTION FUNCTIONS OF ATOMS

Abstract Using the method of radial distribution functions of atoms obtained by Fourier transform of powder X-ray patterns it has been shown directly that the structures of the mixed-valence complexes cis - [Pt II (NH 3 ) 2 (SCN) 2 ][Pt IV (NH 3 ) 2 (SCN) 2 I 2 ] ( I ) and [Pt II (en)(SCN) 2 ][Pt IV (en)(SCN) 2 I 2 ] ( II ) (en = ethylenediamine) contain the linear chains …IPt IV I…Pt II …IPt IV -I…Pt II …I, wherein square-planar complexes of Pt II alternate with octahedral complexes of Pt IV . Such a structure for I had earlier been proposed only on the basis of indirect spectroscopical data. The distances Pt IV I and Pt II …I have been determined. The first one is 2.70 A in both the complexes and the second is 3.50 A in I and 3.23 A in II . The distances Pt II …I are considerably longer than corresponding distances in the similar mixed-valence complex of known structure [Pt II (en) 2 ][Pt IV (en) 2 I 2 ](ClO 4 ) 4 ( IV ) (about 3.10 A). The elongation of the Pt II …I contact corresponds to the smaller bridge role of I atoms in the thiocianate complexes, to the smaller electron delocalization over the chain of Pt and I atoms and, hence, to a more pronounced division of the system into true complexes of Pt II and Pt IV than in IV .