Coordinative flexibility in an acyclic bis(sulfonamide) ligand.

The new acyclic and potentially heptadentate dinucleating ligand, 2,6-bis(N,N-bis-(2-pyridylmethyl)-sulfonamido)-4-methylphenolato (bpsmp(-)) contains two tertiary sulfonamide groups. The sulfonamide donors permit a greater degree of control over the accessibility of mono versus dinuclear complexes compared to their closely related amine-containing counterparts, on account of their relatively weaker donor properties. A series of air-stable dinuclear complexes of Co(II), Mn(II) and Cu(II) containing two auxiliary acetate ligands have been prepared. The absence of acetate in reaction mixtures containing Co(II) and Mn(II) led to mononuclear complexes, with water ligands completing the coordination spheres of the metal ions, even in the presence of large excess of the metal ions. Thus, bridging acetate ligands appear to stabilise the dinuclear structures for the relatively labile Co(II) and Mn(II) ions. A mononuclear complex of V(IV)=O was isolated even in the presence of acetate, possibly because the oxyl groups on each V(IV) prevent formation of a bis-acetato-bridged complex. Reaction of one equivalent of CuCl(2) with bpsmpH led to isolation of two different mononuclear complexes, dependent on the identity of the solvent. The phenol group is coordinated in only one of these complexes. A dinuclear Cu(II) complex was isolated when two equivalents of the metal salt were used in the reaction.