Reactivity of TCNE and TCNQ derivatives of quinonoid zwitterions with Cu(i)

Abstract

The reactions of TCNE- and TCNQ-functionalized (TCNE: tetracyanoethylene and TCNQ: 7,7′,8,8′-tetracyanoquinodimethane) zwitterionic benzoquinonemonoimines with a Cu(I)-BIAN complex (BIAN = bis(o,o′-bisisopropylphenyl)acenaphthenequinonediimine) have been investigated and found to follow a diversity of interesting patterns. The complexes [Cu(BIAN)(NCMe)(L2)]BF₄ (2) and [Cu(BIAN)(L2)₂]BF₄ (4) were obtained by reacting [Cu(BIAN)(NCMe)₂]BF₄ (1) with one and two equivalents of L2, respectively. Following similar procedures, the complexes [Cu(BIAN)(NCMe)(L3)]BF₄ (6) and [Cu(BIAN)(L3)₂]BF₄ (7) were obtained by reaction of 1 with L3. The reaction of 2 with 0.5 equiv. of 4,4′-bipyridine afforded [{Cu(BIAN)(L2)}₂(μ-4,4′-bipyridine)](BF₄)₂ (3). The complexes were characterized by multinuclear NMR, IR and UV-Vis spectroscopic techniques, mass spectrometry, cyclic voltammetry and elemental analysis. The molecular structures of complexes 3·4CH₂Cl₂ and 4·CH₂Cl₂ were determined by single crystal X-ray diffraction. An unexpected coordination polymer [Cu(L2⁻)₂]_∞ (5) was also structurally characterized, which contains Cu(II) centres chelated by two N,O-bound ligands resulting from the monodeprotonation of L2.