Structural Comparison of Copper(I) and Copper(II) Complexes with Tris(2-pyridylmethyl)amine Ligand

Copper(I) complexes with the tris(2-pyridylmethyl)amine (TPMA) ligand were synthesized and characterized to examine the effect of counteranions (Br−, ClO4−, and BPh4−), as well as auxiliary ligands (CH3CN, 4,4′-dipyridyl, and PPh3) on the molecular structures in both solid state and solution. Partial dissociation of one of the pyridyl arms in TPMA was not observed when small auxiliary ligands such as CH3CN or Br− were coordinated to copper(I), but was found to occur with larger ones such as PPh3 or 4,4′-dipyridyl. All complexes were found to adopt a distorted tetrahedral geometry, with the exception of [CuI(TPMA)][BPh4], which was found to be trigonal pyramidal because of stabilization via a long cuprophilic interaction with a bond length of 2.8323(12) Å. Copper(II) complexes with the general formula [CuII(TPMA)X][Y] (X = Cl−, Br− and Y = ClO4−, BPh4−) were also synthesized to examine the effect of different counterions on the geometry of [CuII(TPMA)X]+ cation, and were found to be isostructural with previously reported [CuII(TPMA)X][X] (X = Cl− or Br−) complexes.