Preparation, Crystal Structures, and Properties of the Acetate-Bridged Platinum(III) Compounds [{(H2O)Pt(μ-CH3CO2)2}2]A2 (A− = C1O4−, CF3SO3−)1

Abstract

Reaction of K2[Pt(NO2)4] with CH3CO2H/H2O/HA, where HA = HC1O4, CF3SO3H, or HNO3, gave [{(H2O)Pt(μ-CH3CO2)2}2]A2. With nitrite highly enriched in 15N, the reactions which led to these final products were followed by 195Pt NMR, and intermediate platinum(III) complexes were identified. Crystal structures were determined by X-ray diffraction for the Perchlorate and trifluoromethanesulfonate salts: for [{(H2O)Pt(μ-CH3CO2)2}2](ClO4)2, monoclinic crystal system, space group P21/c, a = 8.113(4) Å, b = 8.279(2) Å, c = 14.892(7) Å,ß= 101.16(2)°, V = 981.4(7) Å3, Z = 2, Pt-Pt = 2.3906(13) Å; for [{(H2O)Pt(μ-CH3CO2)2}2](CF3SO3)2·4H2O, monoclinic crystal system, space group P21/c, a = 8.162(2) Å, b = 8.982(1) Å, c = 19.404(6) Å,ß = 95.51(1)°, V = 1416.0(5) Å3, Z = 2, Pt-Pt = 2.3929(6) Å. In water, there was rapid conversion to a complex with three acetate bridges. In acetic acid or dmf, there was replacement of the axial water ligands by acetate or dmf, respectively, but the tetra-acetate-bridged structure remained intact for several hours. Some axially-substituted derivatives were obtained in solution by addition of ligands to a dmf solution of the trifluoromethanesulfonate salt and were characterized by 195Pt NMR. Solids [{XPt(μ-CH3CO2)2}2] were isolated with X = CI, Br. The crystal structures of [{(H2O)Pt(μ-CH3CO2)2}2]A2 showed Pt-Pt-O(acetate) angles slightly less than 90°. This, together with very low shielding of the carboxylate carbon nuclei in the tetra-acetate-bridged complexes, was interpreted as indicating strain in these structures. UV spectra of the compounds were similar to those of sulfate- and hydrogen phosphate-bridged platinum(III) complexes with the same axial ligands. Show more