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.

Automated summary

Various CAAC precursors were synthesized and added to compounds of Pd and Pt, resulting in different complexes. The experimental results indicate that reaction temperature and reagent selection have a significant impact on the final product.