Synthesis and characterization of early and late transition metallocalix[5]arene complexes

Abstract

Calixarenes are macrocyclic oligomers of phenols bridged with methylenes. They have been extensively studied because of their unique structure, complexing abilities, conformational flexibility, and reactivity. Their chemistry has been applied as an oxo platform for catalyst model studies. The coordination chemistry of the simple calix[4]arenes is now relatively well developed. By contrast, metal compounds containing the larger ring systems, for example calix[5]arene, are still quite rare. Our interest in calix[5]arene chemistry is related to our longer-term research objectives. We are interested in modeling a bifunctional oxo surface, in which two metals can react in a cooperative manner. This requires a conformation that will allow two metals, or a metal and non-metal, to interact on the calixarene surface" (Chapter1). We synthesized a series of deprotonated calixarenes "calix[n]anions" (including mono- to dianionic species) by the reaction of parent calix[5]arene with alkali metal bases (Chapter 2). In this context, we were able to synthesize and characterize a variety of Ti(IV) (Chapter 3), Mo(VI) (Chapter 4) and Pd(II) (Chapter 5) metallocalix[5]arene complexes using calixanions as starting materials in which the transition metal binds directly to the oxygen surface of the calix[5]arene. Finally, the reactivity of the palladium calix[5]arene complexes was tested and successfully utilized in the synthesis and characterization of the first examples of Pd(II)/Ti(IV) and Pd(II)/Mo(VI) heterobimetallic complexes (Chapter 6)"--Abstract.