Recent advances in pyrazolato-bridged homo- and heterometallic polynuclear platinum and palladium complexes

Multinuclear transition metal complexes and organometallic complexes having pyrazoles and pyrazolate bridging ligands have been the focus of considerable attention owing to their versatility of structures and interesting properties. Recent advances in pyrazolato-bridged homo- and heterometallic polynuclear platinum and palladium complexes revealed that the choice of substituent groups on the pyrazoles and pyrazolates is very important for controlling the stereostructures of polynuclear complexes and selective formation of heteropolynuclear complexes, because they are closely related to the basicity and coordinating ability of pyrazoles. This review focuses recent advances in synthetic, structural, thermodynamic, electronic and photophysical properties of Pt- and Pd-based heteropolynuclear complexes. Since these properties are worth comparing with those of homometallic polynuclear complexes, this review also includes pyrazolato-bridged dinuclear and polynuclear Pt and Pd complexes and discusses these properties.