The Exchange of Cyclometalated Ligands.

Alexander D Ryabov

doi:10.3390/molecules26010210

Abstract

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.

Highlights

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The transformations in the carborane series offered an example of the ligand exchange involving a P-donor B-cyclopalladated complex and a P-donor incoming ligand, the B−H bond of which is metalated (Scheme 8)
The transformations in the carborane series offered an example of the ligand exchange involving a P-donor B-cyclopalladated complex and a P-donor incoming ligand, the B–H bond of which is metalated (Scheme 8)

Summary

11. Summary and Conclusions

Acetato-bridged dimeric palladacycles are more soluble in mixed organic solvents and the products did not always crash out from reaction solutions. Their use is advantageous in the case of incoming ligands, which are less stable in acidic media and may undergo solvolysis. The transformations in the carborane series offered an example of the ligand exchange involving a P-donor B-cyclopalladated complex and a P-donor incoming ligand, the B−H bond of which is metalated (Scheme 8). The ligand exchange involving a P-donor B-cyclopalladated complex and a P-donor incoming ligand

Asymmetric Version of the Ligand Exchange

Processes Mechanistically Relevant to Palladium Ligand Exchange