Bis(hfac)-copper(II) complexes bridged by pyrimidines showing magnetic interactions

Crystals of bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)bis-pyrimidinecop per(II) (1), bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)bis(4-methylpyri midine)copper(II) (2), bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)bis(qu inazoline)- copper(II) (3) showed ferromagnetic interactions at extremely l ow temperature. Crystal structure analyses revealed that these complexes we re catena-bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)[mu -pyrimidine-N-1 :N-3]copper(II), [Cu(hfac)(2)-(pm)(2)](n), catena-bis(1,1,1,5,5,5-hexafluo ropentane-2,4-dionato)[mu -4-methylpyrimidine-N-1:N-3]copper(II), [Cu(hfac) (2)(4-Me-pm)](n), and catena-bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato) [mu -pyrimidine-N-1 :N-3]copper(II), [Cu(hfac)(2)-(qz)](n), for (1), (2) an d (3), respectively. In (1) and (2) the pyrimidines bridge the Cu atoms wit h an axial-equatorial mode to form one-dimensional spiral chains. Complex ( 3) also forms a one-dimensional chain structure. The coordination mode of ( 3) is axial-axial at room temperature, while axial-equatorial at 120 K. On the other hand, the structure of the other modification of the 4-methylpyri midine complex (4), showing paramagnetic properties, was revealed to be a t rinuclei complex bridged by two 4-methylpyrimidines, tris[bis(1,1,1,5,5,5-h exafluoropentane-2,4-dionato)copper(II)][bis-mu -4-methyl-pyrimidine-N-1:N- 3]. The chain structures with an axial-equatorial coordination mode of the bridging organic moieties should play an important role in the appearance o f the ferromagnetic interactions.