Novel Dinucleating Ligand Systems Containing Two Adjacent Coordination Compartments of the Potential Triamidoamine-Type - Nickel(II) and Cobalt(II) Coordination Chemistry

Abstract

The preparation of novel dinucleating pyrazolate ligands H 5 L 3 - H 5 L 8 carrying chelating side arms with appending secondary amine functions is reported. Following different synthetic routes, either CH 2 CF 3 , C 6 H 2 F 3 , or C 6 F 5 moieties can be introduced as substituents at the terminal nitrogen atoms. These systems are reminiscent of two coupled coordination compartments of the potential triamidoamine-type. Crystallographic analyses of a series of bimetallic complexes of the CH 2 CF 3 -substituted ligand H 5 L 4 with NiCl 2 and CoCI 2 reveal manifold coordination modes in the solid state, resulting from the facile detachment of a single or several N-donor sites from the metal centers. Coordination number sets {4/6} (in H 5 L 4 Co 2 Cl 4 ) and {5/6} (in H 4 L 4 Ni 2 Cl 3 , H 4 L 4 Co 2 Cl 3 and H 5 L 4 Ni 2 Cl 4 ) are thus observed. In the non-deprotonated H 5 L-type systems the remaining protons are found to be scavenged by a pyrazolate-N (in H 5 L 4 Ni 2 Cl 4 ) or an amine function of a ligand side arm (in H 5 L 4 Co 2 Cl 4 ).