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Ligand-controlled oxidation state ambivalence in copper–quinone complexes. Replacement of N-donor by S-donor ligands favours the copper( I )–semiquinone over the copper( II )–catecholate form

1994; Royal Society of Chemistry; Volume: 90; Issue: 19 Linguagem: Inglês

10.1039/ft9949002905

1364-5455

Jochen Rall, Wolfgang Kaim,

Organometallic Complex Synthesis and Catalysis

Paramagnetic complexes between chelating o-quinone derivatives Qn–(Q = 3,5-di-tert-butyl-o-benzoquinone) and coordinatively unsaturated copper compounds (L)Cu have been obtained and studied by EPR spectroscopy. With nitrogen donor co-ligands, L, e.g. saturated polyamines or a bis(imidazole) chelate ligand, the CuII(Q2–) form was observed. In contrast, tetrahydrothiophene and bi-, tri- or tetra-dentate chelating thioethers favour the CuI(Q.–) form as ground state as evident from small 63,65Cu coupling (<1.5 mT), from semiquinone hyperfine splitting and from g factors (<2.010) which are relatively close to the free-electron value. However, the thioether co-ligands generally effect higher metal-coupling constants and g factors in (L)CuI(Q.–) systems than triorganophosphine, triorganoarsine, carbonyl, π-coordinated alkyne or alkene ligands.