ACTIVATION OF AROMATIC CARBON FLUORINE BONDS BY ORGANOPLATINUM COMPLEXES

The ligand Me2NCH2CH2N = CHC6F5 (1a) reacts with [Pt2Me4(mu-SMe2)2] (2) in acetone solution to give sequentially [PtMe2(Me2NCH2CH2N = CHC6F5)] (3a), [PtFMe2(Me2NCH2CH2N = CHC6F5)] (4), and [PtFMe2{Me2NCH2CH2NHCH(CH2COMe)C6F4}] (5). Complex 5, which is formed by reaction of 4 with acetone, was characterized by an X-ray structure determination and shown to contain hydrogen-bonded NH...FPt dimers in the solid state. The ligand PhN = CHC6F5 (6) reacts with 2 to give [PtFMe2(PhN = CHC6F4)(SMe2)] which may exist in two isomeric forms 7a and 7b. The reactions to form 4 and 7 give the first examples of oxidative addition of C-F bonds to platinum(II). The ligand Me2NCH2CH2N = CH (2,6-C6H3F2) reacts with 2 to give [PtMe2{Me2NCH2CH2N = CH(2,6-C6H3F2)}] (3b), but this failed to give oxidative addition of a C-F bond. The ligands Me2NCH2CH2N = CHAr, Ar = 2,6-, 2,5-, or 2,3-C6H3F2, react with 2 to give [PtMe2(Me2NCH2CH2N = CHAr)], and then CH4 and [PtMe(Me2NCH2CH2N = CHC6H2F2)]. These reactions involve activation of a C-H bond rather than a C-F bond of the aryl group. The results show that activation of a C-F bond of a pentafluorophenyl group is facilitated by incorporation into a monodentate or bidentate nitrogen-donor ligand so that intramolecular oxidative addition can occur, but that C-H bond activation is always easier than C-F bond activation in C6H(x)F5-x groups and that more than two fluorine substituents on the phenyl group are necessary for C-F bond activation to occur.