Synthesis of Coordination Compounds

Abstract

Historically, interest in supercritical fluids (SCFs) has been cyclical or, perhaps more accurately, sinusoidal. Currently, research into SCFs is undergoing a substantial resurgence, largely driven by possible applications in so-called "green" chemistry, where supercritical C02 (scCO2) offers considerable scope as an environmentally more acceptable replacement for conventional organic solvents. However, the emphasis here is rather different because the synthesis of new organometallic or coordination compounds in SCFs does not have such obviously. green applications as homogeneous catalysis (see chapter 4.7). Nevertheless, these compounds occupy an important place in SCF chemistry because they represent a large number of the new compounds which have been prepared in SCF solution.The use of coordination compounds in SCFs is rather larger than one might initially expect [I]. The major applications can be divided into two broad categories: (1) the transport of metals, which includes selective extraction, deposition of metal and oxide films and impregnation of metals as a route to composite materials; and (2) synthesis and reactions, which covers a wide range of topics from the synthesis of oxides and other solid state materials to the reactions of organometallic compounds. This chapter focuses on the synthesis of organometallic compounds because this is the area where the majority of the new experimental techniques have been developed. The chapter complements chapter 3.1 and 3.2 which cover, respectively, vibrational and NMR spectroscopy, because IR spectroscopy, and to a lesser extent NMR, have been key tools in the exploration of this chemistry.The chapter is divided into four parts: Strategy, which explains the rationale for carrying out these reactions in SCF solution; Chemistry, which outlines what the reactions are; Equipment, which describes some of the key components and introduces a modular approach to high pressure experiments; and Synthesis, which gives details of how to make particular compounds, including the use of flow reactors and semiflow reactors. It concludes with a brief summary and outlook.