Crystal structures of the fluorochloroplatinates(IV) cis-[(C5H5N)(2)CH2][PtF4Cl2], trans-[(C5H5N)(2)CH2][PtF4Cl2]center dot H2O, and [(C5H5N)(2)CH2][PtF5Cl]

The complex ions cis-[PtF4Cl2](2-), trans-[PtF4Cl2](2-) and [PtF5Cl](2-) have been synthesized by stereoselective ligand exchange reactions utilizing the trans effect and are separated by ion exchange chromatography on diethylaminoethyl cellulose. These anions form stable AB-type salts with the doubly charged cation dipyridiniomethane, [(C5H5N)(2)CH2](2+). X-ray structure determinations on single crystals of cis-[(C5H5N)(2)CH2][PtF4Cl2] (1) (monoclinic, space group P2(1)/n with a = 10.379(10), b = 9.635(2), c = 13.738(2) Angstrom, beta = 99.142(10)degrees, Z = 4), trans-[(C5H5N)(2)CH2][PtF4Cl2] . H2O (2) (triclinic, space group <P(1)over bar> with a = 7.757(4), b = 10.059(7), c = 10.408(6) Angstrom, alpha = 82.49(5), beta = 68.92(4), gamma = 75.46(4)degrees, Z = 2) and [(C5H5N)(2)CH2][PtF5Cl] (3) (orthorhombic, space group Pnma with a = 10.394(3), b = 13.320(2), c = 9.2694(10) Angstrom, Z = 4), reveal the perfect ordering of the anion sublattice. The stronger trans influence of Cl compared with F is observed in asymmetric axes F-.-Pt-Cl'. The bond lengths Pt-F-. are 0.026 Angstrom (1.4%) longer and the Pt-Cl' distances are 0.078 Angstrom (3,3%) shorter in comparison with those of symmetrically coordinated axes. The weakening of the Pt-F-. bond and the strengthening of the Pt-Cl' bond is better recognizable from shifts of the stretching vibrations by 8% to lower and by 13% to higher frequencies, respectively. Correspondingly, the valence force constants are found to be 15% lower and 22% higher. The trans influence is observed most distinctly in the F-19-nmr spectra exhibiting the coupling constant (1)J((FPt)-Pt-.) to be 29% smaller than (1)J(FPt).