Preparation Of Complexes Bearing N-Alkylated, Anionic Or Protic Caacs Through Oxidative Addition Of 2-Halogenoindole Derivatives

CAAC precursors 2-chloro-3,3-dimethylindole 1 and 2-chloro-1-ethyl-3,3-dimethylindolium tetrafluoroborate 2BF(4) have been prepared and oxidatively added to [M(PPh3)(4)] (M=Pd, Pt). Salt 2BF(4) reacts with [Pd(PPh3)(4)] in toluene at 25 degrees C over 4 days to yield complex cis-[3]BF4 featuring an N-ethyl substituted CAAC, two cis-arranged phosphines and a chloro ligand. Compound trans-[3]BF4 was obtained from the same reaction at 80 degrees C over 1 day. Salt 2BF(4) reacts with [Pt(PPh3)(4)] to give cis-[4]BF4. The neutral indole derivative 1 adds oxidatively to [Pt(PPh3)(4)] to give trans-[5] featuring a CAAC ligand with an unsubstituted ring-nitrogen atom. This nitrogen atom has been protonated with py.HBF4 to give trans-[6]BF4 bearing a protic CAAC ligand. The Pd-II complex trans-[7]BF4 bearing a protic CAAC ligand was obtained in a one-pot reaction from 1 and [Pd(PPh3)(4)] in the presence of py.HBF4.