Microwave-Assisted Synthesis of Coordination and Organometallic Compounds

Abstract

Microwave irradiation (MW) as a “non-conventional reaction condition” (Giguere, 1989) has been applied in various areas of chemistry and technology to produce or destroy diverse materials and chemical compounds, as well as to accelerate chemical processes. The advantages of its use are the following (Roussy & Pearce, 1995): 1. Rapid heating is frequently achieved, 2. Energy is accumulated within a material without surface limits, 3. Economy of energy due to the absence of a necessity to heat environment, 4. Electromagnetic heating does not produce pollution, 5. There is no a direct contact between the energy source and the material, 6. Suitability of heating and possibility to be automated. 7. Enhanced yields, substantial elimination of reaction solvents, and facilitation of purification relative to conventional synthesis techniques. 8. This method is appropriate for green chemistry and energy-saving processes. The substances or materials have different capacity to be heated by microwave irradiation, which depends on the substance nature and its temperature. Generally, chemical reactions are accelerated in microwave fields, as well as those by ultrasonic treatment, although the nature of these two techniques is completely distinct. Microwave heating (MWH) is widely used to prepare various refractory inorganic compounds and materials (double oxides, nitrides, carbides, semiconductors, glasses, ceramics, etc.) (Ahluwulia, 2007), as well as in organic processes (Oliver Kappe et al, 2009; Leadbeater, 2010): pyrolisis, esterification, and condensation reactions. Recent excellent reviews have described distinct aspects of microwave-assisted synthesis of various types of compounds and materials, in particular organic (Martinez-Palou, 2007; Oliver Kappe et al, 2009; Besson et al, 2006) and organometallic (Shangzhao Shi and Jiann-Yang Hwang, 2003) compounds, polymers, applications in analytical chemistry (Kubrakova, I.V., 2000), among others. Microwave syntheses of coordination and organometallic compounds, discussed in this chapter, are presented by relatively a small number of papers in the available literature in comparison with inorganic and organic synthesis. The use of microwaves in coordination chemistry began not long ago and, due to the highly limited number of results, these works can be considered as a careful pioneer experimentation, in order to establish the suitability of this technique for synthetic coordination chemistry. Classic ligands, whose numerous