Palladium(II), Platinum(II), and Iridium(I) Complexes of 2-Phosphino-1-dimethylaminoferrocenes: A Survey of Structure and Catalysis

A series of PdCl2, PtCl2, and Ir(COD)BArF complexes bearing a rare class of racemic bidentate 2-phosphino-1-dimethylaminoferrocene ligands were prepared and characterized by NMR spectroscopy and X-ray crystallography. The new complexes displayed a structural trend relating a decrease in heteroatom-metal bond length with an increase in ligand bite angle on going from Ir to Pd and Pt. The PdCl2 and PtCl2 complexes were almost isostructural and featured MCl2 moieties in the plane of the substituted Cp ring of the ligand. In contrast, the Ir(COD)+ complex was distinguished by a bend of the Ir(COD) moiety toward the unsubstituted (Cp′) ring. The latter gave rise to a steric interaction that placed the Cp rings in almost eclipsed conformations. Ligand 8a (2-diphenylphosphino-1-dimethylaminoferrocene) was able to promote Pd-catalyzed Suzuki−Miyaura and Buchwald−Hartwig coupling of aryl chlorides in addition to Ir-catalyzed hydrogenation of electron-deficient and unactivated alkenes. A preliminary intramolecular hydroamination of a terminal alkene using 8a in conjunction with Ir(I) afforded the cyclized product in 64% yield.