Triazamacrocyclic complexes with 8- and 9-membered chelate rings. Preparation, structures and agostic interactions in complexes of 1,5,9-triazacyclotetradecane and 1,5,9-triazacyclopentadecane

Abstract Cobalt(II), copper(II) and nickel(II) complexes of the ligands 1,5,9-triazacyclotetradecane (tatd) and 1,5,9-triazacyclopentadecane (tapd), which have 8- and 9-membered chelate rings, respectively, have been prepared and characterised. Crystal structures of [Ni(tatd)(NCS) 2 ]·H 2 O and [Co(tatd)(NCS) 2 ] have been determined. The nickel(II) complex has a distorted square pyramidal geometry and the cobalt(II) complex has a distorted trigonal bipyramidal geometry. Agostic interactions between a hydrogen on the central carbon of the 8-membered chelate ring and the metal ion are observed in both complexes.