Synthesis and Characterization of New Mono‐, Di‐, and Trinuclear Copper(II) Triethanolamine‐Carboxylate Complexes

Abstract

Abstract A series of triethanolamine copper(II) carboxylate complexes have been synthesized and characterized both structurally and spectroscopically. The structures of the compounds and the nuclearity of the resulting coordination complexes are influenced both by the stoichiometry of the reagents and the steric and electronic influences of the anionic ligands present in the copper coordination spheres. The complexes can be prepared in high yields and purity as highly crystalline solids. Herein we report the spectroscopic and structural data for [NaCu(CF 3 COO) 3 (TEAH 3 )] ( 1 ), [Cu(C 6 H 5 COO)(TEAH 2 )] 2 ·2H 2 O ( 2 ), [Cu 3 (CH 3 COO) 4 (TEAH 2 ) 2 ] ( 3 ), [Cu 3 (HCOO) 4 (TEAH 2 ) 2 ] ( 4 ) and [Cu 3 (CF 3 OO) 2 (TEAH 2 ) 2 (CH 3 OH) 2 ][CF 3 CO 2 ] 2 ( 5 ) (TEAH 3 = triethanolamine (N(CH 2 CH 2 OH) 3 ); [TEAH 2 ] ‐ = mono‐deprotonated ion; [TEAH] 2‐ = doubly deprotonated ion). Two approaches to these compounds were employed: direct reaction of copper(II) carboxylates with TEAH 3 and reaction of the tetrameric compound [{Cu(TEAH)} 4 ] ( 6 ) with copper(II) carboxylates. Compound 1 is polymeric in the solid state, being a double salt of sodium trifluoroacetate and (triethanolamine)copper(II) trifluoroacetate, while 2 exists as a simple dimer. Compounds 3 , 4 and 5 are trinuclear complexes with Cu 3 chains connected by bridging carboxylate and triethanolamine ligands. 3 was characterized as three crystal modifications: an unsolvated form and as a methanol solvate 3 ·2MeOH that was found to exist in both monoclinic and orthorhombic forms. 4 was also found to exist as a methanol solvate, 4 ·1.70 MeOH. 5 shows coordination isomerism compared to compounds 3 and 4 in that two of the carboxylate ligands in the metal coordination spheres on the end copper atoms have been replaced by solvent methanol. The magnetic behavior of the di‐ and trinuclear species has been probed and reveals that at low temperatures the metal centers exhibit strong ferromagnetic coupling, which, on warming, switches to simple paramagnetic behavior.