“…Model complexes have been reported to reproduce the peculiar structure and spectroscopic features of blue copper proteins Kitajima et al, 1992;Holland & Tolman, 1999;, or the function of these biological electron carriers (Rorabacher, 2004). The major synthetic challenges to yield structural/spectroscopic models have been: 1) obtain Cu(II)-thiolate species, without the concomitant formation of disulfides and Cu(I) (Mandal et al, 1997), and 2) provide complexes exhibiting distorted tetrahedral coordination of Cu(II), which mostly prefers a tetragonal environment. Substituted tris(pyrazolyl)borate ligands were originally employed in order to fulfil these requirements (Kitajima & Tolman, 1995), since they are tetrahedral enforcers and furnish enough electron density to copper to disfavor oxidation of thiolate coligands (Bruce & Ostazewski, 1973;Churchill et al, 1975).…”