Rational Synthesis of an Unsymmetric Pt Complex Unit Having Two Kinds of Pyrazolate Ligands: Elucidating Steric and Electronic Effects of Pyrazolate Ligands in Pt-Ag Sandwich Complexes

Herein we report the rational synthesis of an unsymmetric Pt complex containing two different pyrazole ligands and a selective formation of Z-shaped Pt2Ag2 complex using the unsymmetric Pt complex unit, whose structures were undoubtedly revealed by X-ray crystallographic analysis in the solid state and NMR analysis in the solution state. The selective formation of the unsymmetric Pt and Pt2Ag2 complexes enable us to reveal that the steric effect from the pyrazole ligands determine the orientation of the Pt complex units but hardly influence on the photophysical properties of the complexes. The TD-DFT calculations of the Pt and Pt2Ag2 complexes supported the small electronic contributions of pyrazole moieties. This synthetic route will build up a new strategy to obtain new types of precious metal sandwich complexes.

Automated summary

In this study, a rational synthesis of an unsymmetric Pt complex with two different pyrazole ligands was successfully carried out. The unsymmetric Pt complex was used to selectively form a Z-shaped Pt2Ag2 complex, whose structures were confirmed by X-ray crystallographic and NMR analysis. It was found that the steric effect of the pyrazole ligands determined the orientation of the Pt complex units, but had little influence on the photophysical properties of the complexes. TD-DFT calculations supported the small electronic contributions of the pyrazole moieties in the Pt and Pt2Ag2 complexes. This synthetic route offers a new strategy for obtaining new types of precious metal sandwich complexes.