Unexpected behaviour of copper(I) towards a tridentate Schiff base: synthesis, structure and properties of new Cu(I)-Cu(II) and Cu(II) complexes

The reaction of CuBr with 2,6-bis[1-(2,6-diisopropylphenylimino)ethyl]pyrid ine L afforded a new Cu(I)-Cu(II) derivative [CuBrL](2)[Cu2Br4] (1), while the reaction of [Cu(CH3CN)(4)]PF6 with L in THF yielded the new Cu(I) compo und CuL(THF)(CH3CN)PF6 (2). Derivative 2 further reacted with halogenated s olvents to yield halogeno-Cu(II) salts, [CuClL]PF6 (3) using CHCl3 and [CuB rL]Br-3 (4) using CHBr3, Compounds 1, 3 and 4 have been fully characterised by X-ray crystallography; they contain essentially similar [CuXL](+) catio ns with a square planar copper(II) co-ordination. However, the structure of compound 1 must be viewed as built of tetranuclear units since two [(CuBrL )-Br-II](+) cations are bridged by a [(Cu2Br4)-Br-I](2-) anion with a rathe r strong Cu-II. . . Br (2.689(2) Angstrom) secondary interaction. These sec ondary interactions (Cu-II cation . . . FPF5 or Br anion) are weaker in 3 a nd 4. The electrochemical properties of compounds 1-4 are discussed, too. ( C) 2001 Elsevier Science B.V. All rights reserved.