Intramolecular and intermolecular C-H activation at a cationic PtII center

Syntheses and C-H bond activation reactions of the novel electrophilic Pt-II complexes [(tmeda)Pt(CH3)(OEt2)][BArf], [(tmeda)Pt(CH3)(THF)][BArf], and [(tmeda)Pt(CH3)(NC5F5)][BArf] are described {[BArf](-) = [(3,5-C6H3(CF3)(2))(4)B](-)} (tmeda is N,N,N',N'-tetramethylethylenediamine). [(tmeda)Pt(CH3)(OEt2)][BArf] and [(tmeda)Pt(CH3)(THF)][BArf] are unstable at room temperature, yielding methane and the Fischer carbene Pt-II hydrides, [(tmeda)Pt(=C(CH3) (OCH2CH3))(H)] [BArf] and [(tmeda)Pt(=CCH2CH2CH2O)(H)][BArf]. The methane liberated from [(tmeda)Pt(CH3)(OEt2-d(10))][BArf] consists of an isotopomeric mixture, (CH4, CH3D, CH2D2, and CHD3), indicating a multiple H/D exchange reaction following the C-D activation and prior to methane loss. [(tmeda)Pt(CH3) (THF-d(8))][BAr] liberates CH4 and CH3D. Methane-C-13, cyclohexane, toluene, and benzene react with [(tmeda)Pt(CH3)(NC5F5)][BArf] to yield methane and new organoplatinum complexes. Deuterated alkanes and arenes react with [(tmeda)Pt(CH3) (NC5F5)][BArf] to give a mixture of methane isotopomers. The relevance of these results to the oxidation of alkanes by aqueous platinum complexes is discussed. (C) 1998 Elsevier Science S.A.