Pyridazine-bridged copper(i) complexes of bis-bidentate ligands: tetranuclear [2 ? 2] grid versus dinuclear side-by-side architectures as a function of ligand substituents

Citations Over TimeTop 20% of 2007 papers

Abstract

Eight bis-bidentate Schiff-base ligands, derived from 3,6-diformylpyridazine and substituted amino-benzenes, have been prepared. A variety of electron donating/withdrawing and/or sterically demanding/undemanding substituents were employed. Two ligands and five of the six pure copper(I) complexes have been structurally characterised. The sterically unhindered ligand derived from 3,5-difluoroaniline, (m,m-F), was almost completely flat whereas the very sterically hindered ligand derived from trimethylaniline, (o,o,p-Me), was severely twisted. The only dinuclear side-by-side complex obtained, [Cu(I)(2)((o-Ph))(2)](PF(6))(2), was of the ligand derived from 2-aminobiphenyl. All five of the other complexes are believed to be [2 x 2] tetranuclear grid complexes, and this was unequivocally shown to be the case for four of these complexes, [Cu(I)(4)((p-Me))(4)](PF(6))(4), [Cu(I)(4)((o,p-Me))(4)](PF(6))(4), [Cu(I)(4)((m,m-F))(4)](PF(6))(4) and [Cu(I)(4)((m,m-Cl))(4)](PF(6))(4). In all cases the copper(I) centres are substantially distorted from tetrahedral, with the most severe distortion present in the side-by-side complex. In the absence of any special effects, tetracopper(I) [2 x 2] grid architectures are observed to be the favored outcome for 1 : 1 reactions of these bis-bidentate ligands with copper(I) ions. Only when the aromaticity of the ligand was extended by employing a phenyl substituent on the phenyl rings, (o-Ph), did a dicopper(I) side-by-side architecture result. Cyclic voltammetry in acetone revealed that the free ligands did not undergo reduction until potentials below -0.8 V, whereas between three and four reversible one electron reductions were observed, between +0.16 and -0.71 vs. AgCl/Ag, for the tetranuclear copper(I) [2 x 2] grid complexes. The redox potentials observed for these complexes are highly dependent on the nature of the ligand phenyl ring substituent(s). The side-by-side complex had one irreversible reduction process, E(pc)ca.-0.5 V.

Related Papers

• → A convenient and facile synthesis of pyridine, pyridazine, pyrimido-[4,5-c]pyridazine, pyrido[3,4-c]pyridazine, 1,6-naphthyridine and phthalazine derivatives(2006)16 cited
• → The synthesis of imidazo[4,5‐c] ‐ and v‐triazolo[4,5‐c] pyridazines(1967)24 cited
• → Studies on the Syntheses of N-Heterocyclic Compounds. XII. Syntheses of Pyrido[3, 4-d]pyridazine and Pyrido[2, 3-d]pyridazine Derivatives(1972)4 cited
• → Aspects of the Stereochemistry of Seven‐Coordination(1979)72 cited
• → The synthesis of pyrazino[2,3‐d]pyridazine and some of its derivatives(1966)20 cited