Tetranuclear complexes composed of dinickel(II) macrocyclic fragments bridged by 5,5′-(1,3-phenylene)bis-1H-tetrazolato and N,N-bis(tetrazol-5-ato)amine coligands: Synthesis, structures and magnetic properties

Abstract

The dinuclear nickel(II) complex [Ni2LCl]+, where L2− represents a 24-membered macrocyclic hexamine-dithiophenolate ligand, reacts with 5,5′-(1,3-phenylene)bis-1H-tetrazole and N,N-bis(tetrazol-5-yl)amine to give the tetranuclear complexes [(Ni2L)2(N4C–X–CN4)]+, where X=1,3-C6H4 (1) and NH (2). The new complexes were both isolated as perchlorate or tetraphenylborate salts and characterized by elemental analysis, UV/Vis, IR spectroscopy, and X-ray analysis. The crystal structures of the tetraphenylborate salts show bridging bistetrazolato moieties joining two dinuclear [Ni2L]2+ fragments through their ring N2 and N3 atoms. Temperature-dependent magnetic susceptibility measurements reveal the presence of weak ferromagnetic exchange interactions between the NiII ions in the binuclear [Ni2L]2+ subunits with magnetic exchange coupling constant values of J1=16.6cm−1 for 1[BPh4]2, and J1=16.8cm−1 for 2[BPh4]2 (H=–2JS1S2). The exchange coupling constant J2 across the bistetrazolato bridge in both compounds is less than 0.1cm−1, which suggests that no significant interdimer coupling occurs across the linking tetrazolato moieties.