The Exchange of Cyclometalated Ligands

Reactions of cyclometalated compounds are numerous. This account is focused on one of such reactions, the exchange of cyclometalated ligands, a reaction between a cyclometalated compound and an incoming ligand that replaces a previously cyclometalated ligand to form a new metalacycle: + H-C*~Z ⇄ + H-C~Y. Originally discovered for PdII complexes with Y/Z = N, P, S, the exchange appeared to be a mechanistically challenging, simple, and convenient routine for the synthesis of cyclopalladated complexes. Over four decades it was expanded to cyclometalated derivatives of platinum, ruthenium, manganese, rhodium, and iridium. The exchange, which is also questionably referred to as transcyclometalation, offers attractive synthetic possibilities and assists in disclosing key mechanistic pathways associated with the C–H bond activation by transition metal complexes and C–M bond cleavage. Both synthetic and mechanistic aspects of the exchange are reviewed and discussed.

Advancements in C–PR2 (R = Alkyl or Aryl) Bond Formation Reactions Involving Palladium

This review covers recent approaches to the synthesis of tertiary phosphines through the C– PR₂ (R = alkyl or aryl) bond formation reactions using palladium. The methods include Pd-catalyzed additions of HPR2 to double and triple bonds, substitution and dynamic kinetic resolution of diaryl (pseudo) halide compounds, reactions of cyclopalladated complexes with MPR₂ (M = Li or K) or HPR₂, intramolecular phosphination, and C–P⁺ bond cleavages. Together these methods allow for the preparation of diversely functionalized achiral or enantiopure tertiary phosphines for use in organo- and transition metal catalysis among other important applications.