Tetrylenes based on tri- and tetradentate ONO-, NNO-, NNN-, and ONNO-type ligands: synthesis, structure, and reactivity

The review discusses the results of the authors' research aimed at the synthesis of stable tetrylenes (germylenes and stannylenes) and the determination of the structure of these compounds, including their oligomeric degree. Substituted dialkanolamines, dialkylenetriamines, aminobisphenols, pyridine and phenanthroline-containing dialcohols, and some other derivatives were used as the ligands for the synthesis. The reactivity of monomeric and dimeric tetrylenes in the reactions proceeding with both the change and the retention of the oxidation state of the metal atom (2+) is discussed in detail, as well as the influence of the oligomeric degree on the reactivity. The use of tetrylenes in synthetically useful reactions as ligands for catalytically active transition metal complexes, as well as initiators for ring-opening polymerization of cyclic esters, is analyzed.