Reactions of Pyridyl-Functionalized, Chelating 3-Phosphinines in the Coordination Environment of RhIII and IrIII

RhIII and IrIII complexes based on the 3-P,N hybrid ligand 2-(2-pyridyl)-4,6-diphenylphosphinine (1) react selectively at the PC double bond to chiral coordination compounds of the type [(1HOH)Cp*MCl]Cl (2,3), which can be deprotonated with triethylamine to eliminate HCl. By using different bases, the pKa value of the POH group could be estimated. Whereas [(1HO)Cp*IrCl] (4) is formed quantitatively upon treatment with NEt3, the corresponding rhodium compound [(1HO)Cp*RhCl] (5) undergoes tautomerization upon formation of the 5 sigma 4-phosphinine rhodium(III) complex [(1OH)Cp*RhCl] (6) as confirmed by single-crystal X-ray diffraction. Blocking the acidic POH functionality in 3 by introducing a POCH3 substituent leads directly to the 5 sigma 4-phosphinine iridium(III) complex (8) upon elimination of HCl. These new transformations in the coordination environment of RhIII and IrIII provide an easy and general access to new transition-metal complexes containing 5 sigma 4-phosphinine ligands.