Platinum-Mediated C-H Bond Activation of Arene Solvents and Subsequent C-C Bond Formation

The reactions of cis-[PtCl2(SOMe2)(2)] and imines 2,6-Cl2C6H3CH=NCH2(4-XC6H4) (1a, X = H; 1b, X = Cl), 2,6-Cl2C6H3CH=NCH2(2,6-F2C6H3) (1f), and 2,6-Cl2C6H3CH=N(4-ClC6H4) (1g) carried out in toluene at 90 degrees C in the presence of sodium acetate dissolved in methanol produced compounds [PtCl{(MeC6H3)(2-ClC6H3)CHNR)}SOMe2] (R = CH2C6H5 (4a), CH2(4-ClC6H4) (4b), CH2(2,6-F2C6H3) (4f), and 4-ClC6H4 (4g)), containing seven-membered platinacycles via "formal insertion" of a toluene molecule in the metallacycle. These compounds are formed in a process involving several steps, the most relevant being intermolecular C-H activation of a solvent toluene molecule and formation of a carbon-carbon bond. The reaction of cis-[PtCl2(SOMe2)(2)] and imine 2,6-Cl2C6H3CH=NCH2(4-CIC6H4) (1b) under analogous conditions was also carried out using other arene solvents such as benzene and ortho-, meta-, and para-xylene and produced in all cases seven-membered platinacycles. DFT calculations indicate that the stability of the metallacycles increases in the order p-xylyl < m-xylyl < o-xylyl < tolyl < phenyl and have helped to suggest a possible reaction path.