Ligand-Assisted Condensation Reactions

Virtually all types of metal ions have been complexed with macrocyclic ligands.2-7 Complexes of transition metal ions have been studied extensively with tetraaza macrocycles (Chapter 21.2). Porphyrin and porphyrin-related complexes are of course notoriously present in biological systems and have been receiving considerable investigative attention (Chapter 22).8 Macrocyclic ligands derived from the Schiffbase and template-assisted condensation reactions of Curtis and Busch also figure prominantly with transition metal ions.6,7 The chemistry of these ions has been more recently expanded into the realm of polyaza, polynucleating and polycyclic systems.9 Transition metal complexes with thioether and phosphorus donor macrocycles are also known.2... 

Fig. 2.47. Formation of heteronuclear metal-metal bonds by condensation reactions assisted by ligands /X2-ASR2 [Richter F, Vahrenkamp (1979) Angew. Chem. Int. Ed. Engl. 18 531]...

Detailed studies 2,93 of Cu(II)-assisted template condensations and some subsequent reactions (e.g. reduction by sodium borohydride) leading to novel macrocyclic ligands have been reported. It has been shown that treatment of complexes containing ligands bearing pendant -OR (R = H, Me) substituents with Na[BH4] in a mettianol/water mixture leads to reduction of the coordinated ligand. Scheme 10.23 ... 

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