Lithium, magnesium, zinc complexes supported by tridentate pincer type pyrrolyl ligands: Synthesis, crystal structures and catalytic activities for the cyclotrimerization of isocyanates

A convenient and practical method for the cyclotrimerization of isocyanates is described. The reaction was catalyzed in the presence of catalytic amounts (1.0 mol%) of lithium, magnesium, zinc complexes incorporating substituted symmetrical tridentate pyrrolyl ligands leads to the corresponding isocyanurates in good yields. The best result was obtained when the lithium compound was employed as initiator.