Binuclear copper(ii) complexes, [Cu,(L') (0,CMe)l-H,O ( I ) , [Cu,(L5) (0,CMe)ImMeOH (2), [Cu,( L5) (O,CPh)]-H,O (3), [Cu,( L3) (0,CMe)I (4), [Cu,( L2) (0,CMe)l ( 5 ) , and [Cu,( L4) (OMe) (MeOH)] (6) were prepared, where the ligands H,L" are 1 : 2 Schiff bases derived from 1,3-diaminopropan-2-oI and the carbonyl compounds acetylacetone (for Ll), benzoylacetone (for L2), 3-ethoxymethylenepentane-2,4-dione (for L3), methyl acetoacetate (for L4), and salicylaldehyde (for L5). The crystal structures of (1 )-( 4) and (6) were determined b y X-ray analysis. The results revealed that all the complexes are binuclear and bridged b y alkoxide and carboxylate oxygens except for (6) in which the exogenous bridging group comprises two hydrogen-bridged methoxide ions. In all complexes co-ordination geometries are essentially planar, and the angle formed b y the two co-ordination planes falls in the range 5-1 9" for (1)-( 3) and (6), whereas the angle in (4) is 54.6" indicating a large distortion from a coplanar structure. Antiferromagnetic coupling is strong for (6) ( -2 J = 635 cm-') as expected from its large Cu-0-Cu angle (1 37.7"). However, the other complexes showed much lower antiferromagnetism though their Cu-0-Cu angles differ little from that of (6). The l o w antiferromagnetism of (1 )-( 5) was rationalised in terms of countercomplementarity of the orbitals between two bridging groups which participate in the superexchange interaction.