Syntheses and structures of a family of heterometallic pentanuclear [MnIII3LnNa] (Ln = Dy, Tb, Gd and Nd) complexes: H-bonding reduces the nuclearity from nine to five

The reaction of a multisite coordination ligand (LH3) with LnCl(3)-6H(2)O, followed by the addition of Mn(OAc)(2)-4H(2)O, sodium azide and pivalic acid in the presence of triethylamine in a 2:1:1:4:4:6 (LH3 : LnCl(3): Mn(OAc)(2) : NaN3 : pivalic acid : Et3N) stoichiometric ratio afforded a series of heterometallic pentanuclear neutral complexes containing a [Mn(3)(III)LnNa] core {Ln = Dy (1), Tb (2), Gd (3) and Nd (4)}. The oxidation states of the Mn-III ions were confirmed by BVS calculation. All the complexes were characterized by X-ray crystallography. The pentametallic aggregates form a trigonal-bipyramidal geometry in which the three Mn-III ions are in the equatorial plane whereas the sodium and lanthanide ions are in the apical positions. Three different types of Mn-III ions are present in the complexes and all are in a distorted octahedral geometry. An all-oxygen environment is found to be present around the lanthanides as well as the sodium ions. The lanthanide ion is eight-coordinated and in distorted dodecahedral geometry, while the sodium ion is six-coordinate in a distorted trigonal prismatic geometry in 1-4. The pentanuclear core [Mn(3)(III)LnNa(2)] is a subset of one-half of the nonanuclear ensemble, [Mn(6)(III)LnNa(2)](+), reported in literature. We propose that the reduction in the nuclearity of the heterometallic metal ensemble occurs as a result of the influence of hydrogen bonding interactions present in the system.