Preparation of Complexes Bearing N‐Alkylated, Anionic or Protic CAACs Through Oxidative Addition of 2‐Halogenoindole Derivatives

Abstract

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