Manganese(III) compounds with phenol-pyrazole based-ligands: impact of the co-ligand and the carboxylate ligand on the trinuclear core [Mn-3(mu(3)-O)(phpzR)(3)(O2CR')(n)](1-n)

The reaction of H(2)phpzR (R = Me, Ph; H(2)phpzMe = 3(5)-(2-hydroxyphenyl)-5(3)-methylpyrazole and H(2)phpzPh = 3(5)-(2-hydroxyphenyl)-5(3)-phenylpyrazole) with Mn(O2CR')center dot nH(2)O (R' = Me and Ph) and ((Bu4N)-Bu-n)MnO4 in ethanol (EtOH) affords three new manganese(III) compounds, [Mn-3(mu(3)-O)(phpzMe)(3)(O2CMe)(EtOH)]center dot EtOH (1), (nBu(4)N)[Mn-3(mu(3)-O)(phpzMe)(3)(O2CPh)(2)] (2) and ((Bu4N)-Bu-n)[Mn-3(mu(3)-O)(phpzPh)(3)(O2CPh)2] (3). Their synthesis, crystal structure and magnetic properties are reported. Compounds 1-3 are mu(3)-oxido-centered trinuclear manganese(III) compounds whose edges are bridged by phpzR(2-) with average intracluster separations of 3.25 angstrom. The three Mn-O-Mn angles are distorted from the equilateral triangle with values in the range of 113 degrees to 124 degrees; 117 degrees to 125 degrees; and 117 degrees to 126 degrees for complexes 1-3, respectively. Hydrogen bonding interactions between the trinuclear units of 1 result in a one-dimensional chain structure. Compounds 2 and 3 have isolated trinuclear units, perhaps as a result of the presence of the bulky (Bu4N+)-Bu-n cation. Temperature-dependent magnetic susceptibility studies indicate the presence of both antiferromagnetic and ferromagnetic interactions in compound 1 (J(1) = -10.3 cm(-1), J(2) = +10.9 cm(-1)), while only antiferromagnetic interactions are present in compounds 2 and 3 (J(1) = -4.2 cm(-1), J(2) = -10.3 cm(-1) for 2; and J(1) = -4.8 cm(-1), J(2) = -10.2 cm(-1) for 3), with J(1) representing the similar Mn-O-Mn angles and J(2) representing the unique Mn-O-Mn angle (Mn(1)-O(1)-Mn(2)).