SYNTHESIS OF PT(AMINE)(DMF)CL-2 AND [PT(AMINE)X(2)](N) (X=CL, I) AND CRYSTAL-STRUCTURE OF (MU-CHLORO)TRIS[CHLORO(DIMETHYLAMINE)PLATINUM(II)]

Chloro-bridged oligomers of the type [Pt(amine)Cl-2](n), have been syn thesized and characterized by IR and H-1- and Pt-195-NMR spectrometry. These compounds are believed to consist of mostly dimers in the solid state. Heating the oligomers in dichloromethane solution favors the f ormation of trimers. The crystal structure of the dimethylamine chloro -bridged trimer was determined by X-ray diffraction. The crystals belo ng to the trigonal (hexagonal cell) R (3) over bar space group, with a = 15.463(6) Angstrom, c = 13.984(5) Angstrom, and Z = 6. The results have shown that the compound is a cyclic six-membered chloro-bridged t rimer with a 3-fold axis in the center of the ring. The terminal Pt-Cl bond is 2.274(3) Angstrom, significantly shorter than the bridging bo nds which are 2.332(3) and 2.319(3) Angstrom. The Pt3Cl3 ring assumes a ''crown'' conformation with C-3 symmetry. The internal angles are Cl -Pt-Cl' = 90.5(1)degrees and Pt-Cl-Pt' = 93.9(2)degrees. The oligomers are rapidly cleaved in DMF to form first cis-Pt(amine)(DMF)Cl-2, whic h isomerize to the trans isomers. On standing in acetone or dichlorome thane solution, the DMF complexes are partly rearranged to the chloro- bridged oligomers. A few iodo-bridged oligomers were characterized by Pt-195 NMR. The resonances of these species were observed around -4000 ppm. Contrary to the chloro-bridged compounds, the iodo complexes are not cleaved by DMF.