Synthesis, crystal structure, vibrational spectra, and normal coordinate analysis of cis- and trans-(n-Bu4N2)[PtF2(ox)2] and (n-Bu4N)2[PtF4(ox)]

By treatment of trans-(n-Bu4N)(2)[PtCl2(ox)(2)] and (n-Bu4N)(2)[PtCl4(ox)] with XeF2 in propylene carbonate cis- and trans-(n-Bu4N)(2)[PtF2(ox)(2)] (1, 2) and (n-Bu4N)(2)[PtF4(ox)] (3) are formed which have been isolated by ion exchange chromatography on diethylaminoethyl cellulose. The crystal structure of trans(n-Bu4N)2[PtF2(ox)(2)] (2) (tetragonal, space group P4(2)/n, a = 15.5489(9), b = 15.5489(9), c = 17.835(1) Angstrom, Z = 4) und Cs-2[PtF4(OX)] (3) (monoclinic, space group C2/m, a = 14.5261(7), b = 6.2719(4), c = 9.6966(9) Angstrom, beta = 90.216(8)degrees, Z = 4) reveal complex anions with nearly D-2h and C-2v point symmetry. The average bond lengths in the symmetrical coordinated axes are Pt-F = 1.93 (2, 3) and Pt-O 1.987 (2) and in the F-.-Pt-O'-axes Pt-F-. = 1.957 and Pt-O' = 1.977 Angstrom (3). The oxalato ligands are nearly planar with a maximum displacement of the ring atoms of 0.05 (2) und 0.01 Angstrom (3) to the calculated best planes. In the vibrational spectra the symmetric and antisymmetric PtF stretching vibrations are observed at 583 and 586 (2) and 576 and 568 cm(-1) (3). The PtF. modes appear at 565 and 562 (1) and 560 cm(-1) (3). The NO and PtO' stretching vibrations are coupled with internal modes of the oxalato ligands and appear in the range of 400-800 cm(-1). Based on the molecular parameters of the X-ray determinations (2, 3) and estimated data (1) the IR and Raman spectra are assigned by normal coordinate analysis. The valence force constants are f(d)(PtF) = 3.55 (2) and 3.38 (3), f(d)(PtF.) = 3.23 (1) and 3.20 (3), f(d)(PtO) = 2.65 (1) and 2.84 (2) and f(d)(PtO') 2.97 (1) and 3.00 mdyn/Angstrom (3). Taking into account increments of the trans influence a good agreement between observed and calculated frequencies is achieved. The NMR shifts are delta(Pt-195) = 8485 (1), 8597 (2) and 10048 ppm (3), delta(F-19) = -350 (2) and -352 (3) and delta(F-19(.)) = -323 (1) and -326 ppm (3) with the coupling constants (1)J(PtF) = 1784 (2) and 1864 (3) and (1)J(PtF.) = 1525 (1) and 1638 Hz (3).