Copper complexes of the functionalised tripodal ligandtris(2-pyridyl)methylamine and its derivatives

Abstract

The coordination chemistry of the new tripodal ligand tris(2-pyridyl)methylamine (tpm) with copper(I), copper(II) and zinc(II) has been investigated. The synthesis of tpm can readily be modified to access a variety of related tripodal ligands such as 2-(methylsulfanyl)-1,1-di(2-pyridyl)ethylamine (mde); in addition, the primary amine function can be derivatised to extend further the range of complexes obtained. tpm itself is a versatile ligand, showing three distinct coordination modes: bidentate (py, NH₂), tridentate (2py, NH₂) and tridentate (3py). Complexes of stoichiometries Cu(tpm)_n (n = 1–3) have been obtained. The (2py, NH₂) coordination mode is illustrated by the crystal structure of [Cu(tpm)₂][BF₄]₂·Me₂CO, whilst (3py) coordination is found in the crystal structures of [Cu(SO₄)(tpm)(H₂O)]·3H₂O, [{Cu(tpm)}₂Br₃]Br·3MeOH and also the zinc complex [Zn(tpm)(H₂O)₃]₂[Zn(H₂O)₆][SO₄]₃·3H₂O. Amide derivatives of tpm give complexes of stoichiometry CuL₂, and the crystal structures of [Cu(tpma)₂][BF₄]₂ [tpma = tris(2-pyridyl)methylacetamide] and [Cu(tpms)₂]·8H₂O {tpmsH = 4-oxo-4-[tris(2-pyridyl)methylamino]butanoic acid} have been determined. The crystal structure of the sulfate-bridged dimeric complex [{Cu(SO₄)(mde)}₂]·3H₂O shows the mde ligand to be tridentate, with (2py, NH₂) coordination.