Kristallstrukturen,Schwingungsspektren und Normalkoordinatenanalysen der stereoisomeren Trifluorotrichloroplatinate(IV), fac-[(C5H5N)2CH2][PtF3Cl3] · 0,5(CH3)2CO und mer-[(C5H5N)2CH2][PtF3Cl3]

Crystal Structures, Vibrational Spectra, and Normal Coordinate Analyses of the Stereoisomeric Trifluorotrichloroplatinates(IV), fac-[(C₅H₅N)₂CH₂][PtF₃Cl₃] · 0.5(CH₃)₂CO and mer-[(C₅H₅N)₂CH₂][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)₂CH₂]²⁺. The X-ray structure determination on single crystals of fac-[(C₅H₅N)₂CH₂][PtF₃Cl₃] · 0,5(CH₃)₂CO ( 1 ) (triclinic, space group P1 with a = 8.468(3), b = 8.847(2), c = 12.1260(10) Å, α = 79.986(12), β = 79.009(12), γ = 69.20(3)°, Z = 2) and mer-[(C₅H₅N)₂CH₂][PtF₃Cl₃] ( 2 ) (monoclinic, space group P2₁/n with a = 9.620(2), b = 14.031(4), c = 10.435(3) Å, β = 97.54(2)°, Z = 4) reveals the perfect ordering of the anion sublattice. Due to the stronger trans influence of Cl compared to F in asymmetric axes $ {rm F}^. $? Pt? Cl′ the Pt? $ {rm 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 Pt$ {rm F}^. $ 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? $ {rm 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%.