Copper(II)-assisted hydrolysis of 2,4,6-tris(2-pyrimidyl)-1,3,5-triazine (tpymt): syntheses, crystal structures and magnetic properties of [Cu(bpcam)(H 2O) 2]ClO 4 · 3H 2O, [Cu(bpcam)(H 2O) 2][Cu(bpcam)(H 2O)(SO 4)] · 2H 2O and [Cu 2(bpcam) 2(H 2O) 2(SO 4)] · H 2O [bpcam = bis(2-pyrimidylcarbonyl)amidate

Abstract

The reaction of the 2,4,6-tris(2-pyrimidyl)-1,3,5-triazine (tpymt) ligand with copper(II) perchlorate or sulfate in aqueous solution affords complexes [Cu(bpcam)(H 2O) 2]ClO 4 · 3H 2O ( 1), [Cu(bpcam)(H 2O) 2][Cu(bpcam)(H 2O)(SO 4)] · 2H 2O ( 2) and [Cu 2(bpcam) 2(H 2O) 2(SO 4)] · H 2O ( 3) [bpcam = bis(2-pyrimidylcarbonyl)amidate], whose structures have been determined by single-crystal X-ray diffraction studies. Copper(II) promotes the hydrolysis of tpymt in mild conditions yielding the bpcam group which is present in the structures of 1– 3 as a tridentate ligand. The structure of 1 consists of mononuclear [Cu(bpcam)(H 2O) 2] + cations, uncoordinated perchlorate anions and water of crystallization. The structure of 2 is made up of [Cu(bpcam)(H 2O) 2] + cations, [Cu(bpcam)(H 2O)(SO 4)] − anions and lattice water whereas that of 3 contains the neutral dinuclear complex [Cu 2(bpcam) 2(H 2O) 2(SO 4)] and lattice water. While the sulfate group act as a terminal monodentate ligand in 2, it adopts a bis-monodentate bridging mode in 3. The copper atom coordination sphere in 1– 3 is distorted square pyramidal, with three bpcam nitrogen atoms ( 1– 3) and a water molecule ( 1 and 2) or a sulfate oxygen ( 2 and 3) building the basal plane and another water molecule ( 1– 3) in the apical position. The values of the shortest intermolecular copper–copper separation in 1 and 2 are 5.705 and 6.604 Å, respectively, whereas that through bridging sulfato in 3 is 5.494 Å. Variable-temperature magnetic susceptibility measurements show a Curie law behaviour for 2 whereas a weak intramolecular antiferromagnetic interaction [ J = −7.0 cm −1, the Hamiltonian being defined as H ^ = - J S ^ 1 · S ^ 2 ] occurs in 3. The potential use for metal assembling of the stable mononuclear [Cu(bpcam)] + unit is discussed in the light of the results obtained with the related [Cu(bpca)] + complex [bpca = bis(2-pyridylcarbonyl)amidate].