Structure and Bonding in Organometallic Anions of Heavy Group 14 and 15 Elements

Alkali metal organometallic complexes (containing C–metal bonds) and the frequently structrually related alkali metal amides and alkoxides have been investigated extensively both in the solid state and in solution in the past two decades. However, until recently, the related complexes containing the heavier metallic and semi‐metallic p block elements and the alkali and alkaline earth metals had rarely been studied in their own right. Recent solid‐state structural studies have illustrated the immense structural diversity and bonding modes to be found within these species. One of the principal focuses of recent studies has been complexes containing organometallic anions of p block metals (e.g., triorganostannates, containing R3Sn−) in which metal–metal bonds occur between the heavy p block metal and the alkali or alkaline earth metal and the investigation of the nature of this bonding. The development of new synthetic routes has also allowed the preparation of a variety of anionic ligands with p block metal centers which promise new opportunities in coordination chemistry. In addition, the synthesis of a family of homologous anionic π complexes has given a fresh direction in the chemistry of p block metal metallocene complexes. Only four unique designators, or combinations of them, are needed to describe and classify the hydrogen‐bond patterns in organic crystals: rings (as in the rhombohedral form of acetamide shown here), chains, discrete motifs, and intramolecular motifs. The procedures for developing these descriptions are presented, as well as their use in recognizing and defining hydrogen‐bond pattern functionalities that cross the traditional boundaries of chemical functionality, with the purpose of describing molecular recognition and other nonbonding interactions.