Manganese(iii) compounds with phenol–pyrazole based-ligands: impact of the co-ligand and the carboxylate ligand on the trinuclear core [Mn3(μ3-O)(phpzR)3(O2CR′)n]1−n

Abstract

The reaction of H2phpzR (R = Me, Ph; H2phpzMe = 3(5)-(2-hydroxyphenyl)-5(3)-methylpyrazole and H2phpzPh = 3(5)-(2-hydroxyphenyl)-5(3)-phenylpyrazole) with Mn(O2CR').nH2O (R' = Me and Ph) and (nBu4N)MnO4 in ethanol (EtOH) affords three new manganese(III) compounds, [Mn3(mu3-O)(phpzMe)3(O2CMe)(EtOH)].EtOH (1), (nBu4N)[Mn3(mu3-O)(phpzMe)3(O2CPh)2] (2) and (nBu4N)[Mn3(mu3-O)(phpzPh)3(O2CPh)2] (3). Their synthesis, crystal structure and magnetic properties are reported. Compounds 1-3 are mu3-oxido-centered trinuclear manganese(III) compounds whose edges are bridged by phpzR2- with average intracluster separations of 3.25 A. 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 nBu4N+ cation. Temperature-dependent magnetic susceptibility studies indicate the presence of both antiferromagnetic and ferromagnetic interactions in compound 1 (J1 = -10.3 cm(-1), J2 = +10.9 cm(-1)), while only antiferromagnetic interactions are present in compounds 2 and 3 (J1 = -4.2 cm(-1), J2 = -10.3 cm(-1) for 2; and J1 = -4.8 cm(-1), J2 = -10.2 cm(-1) for 3), with J1 representing the similar Mn-O-Mn angles and J2 representing the unique Mn-O-Mn angle (Mn(1)-O(1)-Mn(2)).