Displacement of norbornadiene (NBD) from Pt(CF 3) 2(NBD) by weak donor ligands L, and reactions of cis-Pt(CF 3) 2L 2 with water and acids

Abstract

The NBD ligand in Pt(CF 3) 2(NBD) has been replaced under mild conditions by a number of neutral S-, N-, and O-donor ligands to form cis-Pt(CF 3) 2L 2 complexes (L 2 = N, N, N′, N′-tetramethylethylenediamine (tmen), bipyridine (bipy), ethylenediamine (en); L = pyridine (py), NH 3, dimethylsulfoxide (DMSO), CH 3CN, C 6H 5CN, N, N-dimethylformamide (DMF)). Reaction with DMSO produces predominantly the isomer cis-Pt(CF 3) 2(DMSO- S)(DMSO- O), with cis-Pt(CF 3) 2(DMSO- S) 2 a minor component, as a result of steric constraints. Water or methanol attacks the CF 3 groups, producing fluoride ion. The fluorine atoms of cis-Pt(CF 3) 2L 2 (L 2 = bipy, tmen; L = py) are susceptible to electrophilic attack by H +. Reaction with aqueous HCl or HClO 4 converts one CF 3 group into a coordinated CO group. With HCl, simultaneous protonation and displacement of the N-donor ligands occurred, yielding cis-Pt(CF 3)(CO)Cl 2 −. With HClO 4, the complexes cis-Pt(CF 3)(CO)L 2 + are initially generated, with subsequent displacement of the tmen and py (but not bipy) ligands to form cis-Pt(CF 3)(CO)(OH 2) 2 +. The remaining CF 3 group is not attacked by H +. Reaction of Pt(CF 3) 2(NBD) with halide ions in acetone initially produced the binuclear complexes [(CF 3) 2Pt(μ-X) 2Pt(CF 3) 2] 2− (X = I, Cl) containing bridging halide. With larger amounts of halide ion the expected cis-Pt(CF 3) 2X 2 2− complexes were not obtained, and instead cis-Pt(CF 3)(CO)X 2 − and fluoride ion were formed. When the complexes [(CF 3) 2Pt(μ-X) 2Pt(CF 3) 2] 2− were kept in the presence of NBD, cis-Pt(CF 3)(CO)X 2 − and Pt(CF 3) 2(NBD) were formed. When X = I, these two complexes then reacted together to yield cis-Pt(CF 3) 2I(CO) − and Pt(CF 3)I(NBD).