Preparation and Molecular Structure of cis-Diaqua[(7S, 14S)-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclo-tetradecane]nickel(II) Chloride

Abstract

A six-coordinate diaqua nickel(II) complex with the title macrocyclic ligand, [Ni(H2O)2(S,S-L)]Cl2, has been synthesized and its structure has been determined by the X-ray analysis. Coordination geometry about the Ni is of cis-NiO2N4 type with the macrocyclic ligand folded.

Structural Analysis of All the Nickel 14-Membered Tetraaza Macrocycles in the Cambridge Structural Database

“…Cis V is the only configuration found, within 25 kJ/mol of the lowest conformation, in a conformational search of bismul, cis -diaqua( C - rac- 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane)nickel(II). The next lowest configuration, trans III, is more than 40 kJ/mol higher in energy.…”

Diaqua[(1R,2S,4R,8R,9S,11R)-2,9-dimethyl-1,4,8,11-tetraazacyclotetradecane]nickel(II) dichloride dihydrate

“…The chloride counter ions interact with the water ligands through O-H···Cl hydrogen bonds. Similarly configured nickel cyclam complexes were reported by Ito et al (1981Ito et al ( , 1982. A recent crystal structure search in the CCDC database has shown that only 4% of cyclam complexes without nitrogen functionalization, utilizing halogen containing counter ions and monodentate ligands for the final two coordination sites, adopt a cis V configuration (Allen, 2002).…”

“…For metal complex formation, see: Sadler et al (2007); Voelcker et al (2008). For nickel cyclam complex crystal structures with a cis-V configuration, see: Sadler et al (2007); Ito et al (1981Ito et al ( , 1982; Allen (2002). For details of peptide racemization, see: Liardon & Ledermann (1986).…”