Trinuclear Nickel(II) and Cobalt(II) Complexes Constructed from Mannich–Schiff‐Base Ligands: Synthesis, Crystal Structures, and Magnetic Properties

Abstract

Trinuclear Co II and Ni II complexes have been assembled using an octadentate Mannich–Schiff‐base proligand H 2 L 2 which is obtained by reacting the Mannich base HL 1 with propylenediamine (2:1 molar ratio). HL 1 is obtained from 5‐bromo‐salicylaldehyde and N , N , N′ ‐trimethyl‐ethylenediamine. The reaction of H 2 L 2 with nickel(II) and cobalt(II) as nitrate salts affords the trinuclear complexes [Ni 3 (L 2 )(NO 3 ) 4 ] · CH 3 CN ( 1 ) and [Co 3 (L 2 )(NO 3 ) 4 ] · CH 3 CN ( 2 ) in which the metal ions are bridged by one phenoxido and a nitrato‐oxygen atoms. Within each complex, two of the four nitrato groups act as chelating ligands against the terminal metal ions. The central metal ions in 1 and 2 are hosted into the salen‐like cavity of the organic ligand. The nitrato bridges can be replaced by end‐on azido or end‐on N ‐thiocyanato groups leading to the compounds [Ni 3 (L 2 )(N 3 ) 2 (NO 3 ) 2 ] ( 3 ), [Co 3 (L 2 )(N 3 ) 2 (NO 3 ) 2 ] ( 4 ), and [Co 3 (L 2 )(NCS) 2 (NO 3 ) 2 ] · 2CH 3 CN ( 5 ). The magnetic properties of the five compounds have been investigated, revealing the occurrence on intramolecular antiferro‐ ( 1 and 2 ) and ferromagnetic interactions ( 3 , 4 and 5 ). The nature and size of these interactions are discussed and compared to previously reported results on related systems.