| Abstract |
Three new tetranuclear copper(II) complexes [Cu(HL1)](4)center dot 4EtOH (1 center dot 4EtOH), [Cu(HL2)](4) (2) and [Cu(H2L3)](4)(NO3)(4)center dot 2H(2)O (3 center dot 2H(2)O) have been synthesized using three different hydrazone Schiff base ligands derived from the condensation of the aromatic acid hydrazides 2-hydroxybenzo-, 2-aminobenzoor benzo-hydrazide, with 2,3-dihydroxybenzaldehyde. Complexes 1 and 3 have been characterized by single crystal X-ray diffraction analysis. The coordinating behaviour of the ligand depends on the nature of the ortho substituent present in the hydrazide moiety. The ligands bearing a strong electron donating group (by resonance) in the ortho position undergo complexation via enolization and deprotonation, whereas the absence of such an effect leads to complexation via the keto form, and two different types of tetranuclear Cu(II) clusters, viz. open-cubane and cubane, are obtained. Variable temperature magnetic susceptibility measurements of complexes 1 and 3 have been carried out to examine the nature of magnetic interaction between the Cu(II) centres. All the three complexes (1-3) act as good catalyst precursors towards mild hydrocarboxylation of linear and cyclic alkanes into carboxylic acids in water-acetonitrile medium. |
