Reactions of Pyridyl‐Functionalized, Chelating λ3‐Phosphinines in the Coordination Environment of RhIII and IrIII

Abstract

Rh(III) and Ir(III) complexes based on the λ(3)-P,N hybrid ligand 2-(2'-pyridyl)-4,6-diphenylphosphinine (1) react selectively at the P=C double bond to chiral coordination compounds of the type [(1H⋅OH)Cp*MCl]Cl (2,3), which can be deprotonated with triethylamine to eliminate HCl. By using different bases, the pKa value of the P-OH group could be estimated. Whereas [(1H⋅O)Cp*IrCl] (4) is formed quantitatively upon treatment with NEt3, the corresponding rhodium compound [(1H⋅O)Cp*RhCl] (5) undergoes tautomerization upon formation of the λ(5)σ(4)-phosphinine rhodium(III) complex [(1⋅OH)Cp*RhCl] (6) as confirmed by single-crystal X-ray diffraction. Blocking the acidic P-OH functionality in 3 by introducing a P-OCH3 substituent leads directly to the λ(5)σ(4)-phosphinine iridium(III) complex (8) upon elimination of HCl. These new transformations in the coordination environment of Rh(III) and Ir(III) provide an easy and general access to new transition-metal complexes containing λ(5)σ(4)-phosphinine ligands.