Cyclometalated Platinum β-Diketiminate Complexes

A series of cyclometalated platinum complexes with ancillary β-diketiminate (NacNac) ligands, prepared by a general synthetic route are described. Two different cyclometalating (C^N) ligands―2-phenylpyridine (ppy) and 2-(2,4-difluorophenyl)pyridine (F2ppy)―are used in concert with two different fluorinated NacNac ligands (NacNacF6 and NacNacF18) ‒ to furnish a suite of complexes. The complexes were prepared by metathesis reactions of chloro-bridged dimers [Pt(C^N)(μ-Cl)]2 with lithium salts of the ancillary (LX) ligand. Two structure types can be accessed, depending on the reaction temperature. At lower temperature (ca. 80 °C) bimetallic structures with a bridging NacNac and bridging chloride were prepared, and when the temperature was increased (ca. 100 °C) monometallic Pt(C^N)2(NacNac) complexes formed. The complexes were characterized by X-ray crystallography, and were subjected to in-depth optical and electrochemical interrogation. Fluorination of these ligands by introducing CF3 substituents onto the ligand backbone and/or the N-aryl substituents lead to pronounced changes in the redox properties. All the complexes show a reversible redox couple that was sensitive to the degree of fluorination on the ancillary ligand. Introduction of CF3 groups at the 3- and 5- positions of the N-aryl substituents shifted the potential positive by ca. 50 – 110 mV, but the same substitution minimally perturbed the UV-Vis absorption spectra of the complexes.