Preface

Ruthenium is a precious metal, but unlike gold, silver, and platinum, it is used in only very small amounts in places that we do not usually see. Therefore, non-scientists do not know of its existence or function. Ruthenium is an element under iron in the periodic table. It is used in the hard drives of computers to increase their capacity. It is also used as a catalyst for exhaust gas purification in cars. It may also be used in the tips of some fountain pens. Despite its limited industrial use, many researchers have been investigating ruthenium.

This book introduces the research dealing with ruthenium complexes. As ruthenium is a research target in a wide range of fields, the research presented in this book does not sufficiently cover them all.

Regardless, I hope this book brings understanding of the unique properties and uses of this interesting precious metal.

> **Hitoshi Ishida** Department of Chemistry and Materials Engineering, Kansai University, Suita, Japan
