The magnetic susceptibilities between 80 and 370 K are reported for the complexes [Cu(pd)(OR)](R = Me, Et, Prn, or PhCH2: pd = pentane-2,4-dionato), [Cu(sal)(OCH2Ph)](sal = salicylaldehydato), [Cu(hacp)(OR)] hacp = 2′-hydroxyacetophenone; R = Prn or Bun), and [Cu(hnc)(OR)](Hhnc = 1-hydroxynaphthalene-2-carbaldehyde; R = Prn or Bun, or PhCH2), (I)–(X) respectively. The data are interpretedd on the assumption that these complxes contain dimeric molecules with bridging alkoxo-groups; the exchange parameters (estimated by curve-fitting with g and J varied) are all negative, the value of |J| being 378, 211, 133, 312, 266, 179, 214, 131, 145, and 174 cm–1 for (I)–(X) respectively, where 2|J| is the singlet–triplet separation. Some evidence is found that |J| increases with increasing base strength of the chelating anions, but there is no obvious correlation with analogous properties of the alkoxo-groups. The preparation and properties of [Cu(O2CMe)(OMe)] are also reported; its magnetic susceptibility and mass spectrum provide some support for a tetranuclear structure.