The influence of intramolecular coordination on the aggregation of sodium phenolate complexes. X-ray structures of [NaOC6H4(CH2NMe2)-2]6 and [Na(OC6H2(CH2NMe2)2-2,6-Me-4)(HOC6H2NMe2)2-2,6-Me-4)]2

Abstract

The structural characterization of two new sodium phenolate complexes, containing ortho-amino substituents, enables the influence of intramolecular coordination on the aggregation of sodium phenolate complexes to be determined. Crystals of hexameric [NaOC6H4(CH2NMe2)-2]6 (1a) are monoclinic, space group P21/c, with a = 11.668(4) Å, b = 18.146(4) Å, c = 14.221(5) Å, = 110.76(3) Å, V = 2815.5(16) Å3, and Z = 2; R = 0.0736 for 2051 reflections with I > 2.0(I). Complex 1a contains a unique Na6O6 core, consisting of two face-fused cubes, with the ortho-amino substituent of each phenolate coordinating to a sodium atom. In addition, two of the phenolate ligands have an 2-arene interaction with an additional sodium atom in the core. Crystals of dimeric [(NaOC6H2(CH2NMe2)2-2,6-Me-4)(HOC6H2(CH2NMe2)2-2,6-Me-4)]2 (2b) are triclinic, space group P, with a = 10.0670(8) Å, b = 10.7121(7) Å, c = 27.131(3) Å, = 92.176(8), = 99.928(8), = 106.465(6), V = 2752.1(4) Å3, and Z = 2; R = 0.0766 for 5329 reflections with I > 2.0(I). Dimeric complex 2b contains two phenolate ligands, which bridge the two sodium atoms, each coordinating with one ortho-amino substituent to a sodium atom, while the second available ortho-amino substituent remains pendant. The coordination sphere of each sodium atom is completed by a (neutral) bidentate O,N-coordinated parent phenol molecule. The second ortho-amino substituent of this neutral phenol is involved in a hydrogen bridge with its acidic hydrogen. On the basis of these two new crystal structures and previously reported solid state structures for sodium phenolate complexes, it is shown that the introduction of first one and then two ortho-amino substituents into the phenolate ligands successively lowers the degree of association of these complexes in the solid state. In this process, the basic Na2O2 building block of the molecular structures remains intact.