Introduction: Significance of molecular inorganic chemistry

Whereas inorganic substances have been known and studied since the antiques, it is only during the 19th century that inorganic chemistry was born as an independent scientific discipline. The advances during the 20th, which have been made in inorganic molecular chemistry, have had an impact in the development of the whole field of chemistry and physical sciences. Several species with novel bonding arrangements, unprecedented structures, and unusual reactivities have been prepared comprising also compounds, which at the time were regarded impossible. The current driving force in chemical research arises from demands of materials science to establish the relationship of the molecular and electronic structures with the bulk properties of the materials. Molecular level understanding is needed to develop further electrical conductors, semiconductors, insulators, coatings, ceramics, catalysts, nanotubes, polymers, and thin films, all of which play a significant role in modern technology. The need to replace fossil fuels demands the development of environmentally friendlier energy sources in which molecular inorganic chemistry plays one of the a key roles. This chapter briefly outlines some important developments in bonding and reactivity of molecular inorganic compounds comprising (a) multiple bonding in p-block compounds, (b) secondary bonding interactions, (c) small-molecule activation, (d) weakly coordinating anions, and (e) biradicals and biradicaloids. This list is not exhaustive but serves as an introduction to the 23 chapters in Volume 1 of Comprehensive Inorganic Chemistry III . These chapters describe the spectacular progress in their respective fields during the recent decades.