CRYSTAL-STRUCTURES, VIBRATIONAL-SPECTRA, AND NORMAL-COORDINATE ANALYSES OF THE STEREOISOMERIC TRIFLUOROTRICHLOROPLATINATES(IV),FAC-[(C5H5N)(2)CH2][PTF3CL3]CENTER-DOT-0.5(CH3)(2)CO AND MER-[(C5H5N)(2)CH2][PTF3CL3]

The geometric isomers fac- und mer-[PtF3Cl3](2-) have been isolated by ion exchange chromatography on diethylaminoethyl cellulose. The doubly charged complex anions form stable AB-type salts with the dication dipyridiniomethane, [(C5H5N)(2)CH2](2+). The X-ray structure determination on single crystals of fac-[(C5H5N)(2)CH2][PtF3Cl3] . 0,5(CH3)(2)CO (1) (triclinic, space group P1 $($) over bar$$ with a = 8.468(3), b = 8.847(2), c = 12.1260(10) Angstrom, alpha = 79.986(12), beta = 79.009(12), gamma = 69.20(3)degrees, Z = 2) and mer-[(C5H5N)(2)CH2][PtF3Cl3] (2) (monoclinic, space group P2(t)/n with a = 9.620(2), b = 14.031(4), c = 10.435(3) Angstrom, beta = 97.54(2)degrees, Z = 4) reveals the perfect ordering of the anion sublattice. Due to the stronger trans influence of Cl compared to F in asymmetric axes F-.-Pt-Cl' the Pt-F-. distance is lengthened by 1.8%, the Pt-Cl' distance is shortened by 1.2% in comparison with symmetrically coordinated axes. Correspondingly, the vibrational spectra exhibit shifts of the PtF. streching vibrations by 8% to lower, and of the PtCl' streching vibrations by 12% to higher frequencies. Normal coordinate analyses performed on the basis of the X-ray data result in valence force constants for weakened Pt-F-. bonds to be 14% lower, for the strengthened Pt-Cl' bonds to be 20% higher than in symmetric axes, respectively. Generally the trans influence in fluorochloroplatinates(IV) on the bond lengths is very low with 1-2%, it results in considerable shifts of the stretching vibrations by 8-12% and reveals the strongest effect on the valence force constants with 14-20%.