Magneto-Structural Correlations in Phenoxo-Bridged Metal(II) Compounds. Magnetic Properties of (R4N)2[Co2Cl4(4-XC6H4O)2] (X = H, CH3; R = CH3, C2H5)

Dinuclear compounds (R4N)2[Co2Cl4(4-XC6H4O)2] (X = H, CH3; R = CH3, C2H5) were prepared, and their temperature-variable magnetic susceptibilities were determined to evaluate the exchange-coupling strength's between the cobalt(II) ions. The coupling strength of (Et4N)2[Co2Cl4(4-CH3C6H4O)2] was considered in terms of its structural parameters and the electronic effects of the methyl substituent. Such magneto-structural correlations, together with those for copper(II), nickel(II), and iron(II) systems, confirm that the exchange couplings in phenoxo-bridged metal(II) compounds are affected concurrently by the s/p character of the hybrid orbitals on the bridging oxygen atom, by the electronic effects of the substituents on the aromatic ring, by the ionic radius and acidity of the metal(II) ion, as well as by the number of unpaired electrons and d character of the hybrid orbitals on the metal(II) ion.