SYNTHESIS OF POLYNUCLEAR COPPER(II) COMPLEXES BY CONTROLLING THE CONFORMATION (CIS OR TRANS) OF N,N'-BIS(3-AMINOPROPYL)OXAMIDATE AND THE COORDINATION MODE OF 2,2'-BIPYRIMIDINE

The synthesis, molecular structure and magnetic properties of three ne w polynuclear copper(II) complexes, [Cu(cis-oxpn) Cu(bpm)](ClO4)(2). C H3OH (1), [Cu-2(trans-oxpn) (bpm)(2)](ClO4)(2). 2H(2)O (2) and [Cu-2(t rans-oxpn) (mu-bpm)] (ClO4)(2). 2.5H(2)O (3) are reported. The compoun ds were prepared by controlling the conformation (cis or trans) of oxp n (N,N'-bis( 3-aminopropyl) oxamidate) and the coordination mode (bi- or bisbidentate) of bpm (2,2'-bipyrimidine). Complex 1 is a dinuclear complex in which the copper(II) ions are bridged by a cis-oxamidate gr oup and where bpm acts as a bidentate terminal ligand. 2 is a trans-ox amidate-bridged dinuclear copper(II) complex with two bidentate termin al bpm molecules. In 3, a bisbidentate bpm molecule connects the dinuc lear Cu-2(trans-oxpn) units to generate an alternating oxamidate-bpm p olynuclear copper(II) chain complex. Magnetic susceptibility measureme nts reveal the occurrence of strong antiferromagnetic exchange couplin gs for the three compounds with J values of - 386.0 and - 328.9 cm(-1) for 1 and 2, respectively, and J= - 340.0 cm(-1), with an alternation parameter alpha = 0.24, for 3. Magnetic parameters are discussed on t he basis of the structural results and compared with those of related complexes. (C) 1998 Elsevier Science S.A. All rights reserved.