Organocopper compounds coordination numbers

Organocopper reagents are the most reliable species for conjugate additions and a number of approaches towards chiral cuprates has been developed. The approaches are classified into two categories one is the chiral heterocuprate obtained by treatment with chiral alcohols, amines, sulfonamides, and thiols. The other involves organocopper compounds coordinated by chiral external ligands such as phosphines, sulfides, and oxazolines. 

In inorganic and coordination chemistry, the Cu(II) state is the most abundant one, and is regarded as more stable than the Cu(II) state under normal conditions [32]. Although numerous examples of Cu(I) coordination complexes are known, their chemistry is rather limited and they are readily oxidized to Cu(II) species [32]. Of the common oxidation states, compounds derived from copper(III) are rare, with only 30-40 reported examples [32]. Despite the small number of isolated Cu(III) compounds, however, organocopper] 111) species have been proposed as important intermediates in copper-mediated organic reactions (Chapts. 4 and 10). 

---