Educational and Historical Aspects of Direct Synthesis of Metal Complexes

Abstract

The direct synthesis of metal complexes has been a very active field of study since its first use in 1849 by Edward Frankland to obtain ethylzinc iodide from the reaction of metallic zinc and ethyl iodide. Today this is a firmly established laboratory preparative method as well as a commercial production procedure. The wide appeal is quite understandable, as direct synthesis offers many advantages such as simplicity, greater yields (potentially), preparation of compounds not easily obtained by other methods, and low cost, as common metals are produced in large scale by some of the oldest and best developed chemical reactions known to man. Several different kinds of coordination compounds can be obtained by direct synthesis, starting from zerovalent metals and the appropriate ligands in solution. Direct synthesis of metal complexes can be achieved from the use of “free” (gas phase) metal atoms, from the oxidative dissolution of zerovalent metals, from mechanochemical or tribosynthesis or from the electrochemical oxidation of metallic anodes in solution. The educational importance of exploring the use of each one of those different methodologies for the preparation of metal compounds starting from zerovalent metals in undergraduate laboratories will be discussed in this chapter, along with the historical aspects related to its development since the end of the 19th century, the advances obtained during the 20th century, and its “rebirth” in the age of nanomaterials. Recent developments in the preparation of metal complexes and organometallic compounds from zerovalent metals using novel techniques such as ultrasonic pulses or microwave heating will also be discussed, as these techniques are being explored as competitive routes for the preparation of several inorganic compounds.