Diamagnetic copper

In contrast to the + 2 state, copper(I) compounds are less frequently coloured and are diamagnetic, as expected since the 3d level is full. However, the copper(I) ion, unlike copper(II), is unstable in aqueous solution where it disproportionates into copper(II) and copper(O) (i.e. copper metal). 

The copper(I) ion, electronic stmcture [Ar]3t/ , is diamagnetic and colorless. Certain compounds such as cuprous oxide [1317-39-1] or cuprous sulfide [22205-45 ] are iatensely colored, however, because of metal-to-ligand charge-transfer bands. Copper(I) is isoelectronic with ziac(II) and has similar stereochemistry. The preferred configuration is tetrahedral. Liaear and trigonal planar stmctures are not uncommon, ia part because the stereochemistry about the metal is determined by steric as well as electronic requirements of the ligands (see Coordination compounds). 

Copper corrole is a diamagnetic copper(III) complex which at higher temperatures exists in the triplet state and is then best formulated as a copper(II) corrole-n-radical. 

The colorless, diamagnetic copper(I) complex Cu(acac)(CNPh)2 is formed from copper(I) acetylacetonate and phenyl isocyanide (103). The copper(I) complex (CuCl)2(CNCjH,)2pip was isolated (124) it decomposes to C5H, oNCH=NCgH 11. Primarily on this basis, copper(I) complexes are presumed to be intermediates in various -addition reactions to isocyanides (Section III,D). 

The neutral 3 dx metallocenes are thus known for x = 3 — 8, but the d9 copper complex has thus far resisted preparation, and the d2 titanocene has been found (54) to be both diamagnetic and dimeric, and is therefore excluded from consideration here. A number of cationic species, corresponding formally to Ti(Cp)2+, and V(Cp)2+, systems are however well known, but it seems very probable that these do not possess pseudo-axial symmetry (see (41) for further discussion), and very recently it has been demonstrated (55) that stable V(Cp)2+ complexes cannot be isolated without the coordination of an additional ligand to the metal. The parent systems are therefore limited to V(Cp)2, Cr(Cp)2, Mn(Cp)2, Fe(Cp)2, Co(Cp)2, and Ni(Cp)2 and the cationic species to Cr(Cp)2+, Fe(Cp)2+, Co(Cp)2+, and Ni (Cp)2+> and the d-d spectra of these systems are now considered individually. 

The dinuclear complex [Cu2 (Ls)2] has also been synthesized and isolated (217). In tetrahydrofuran (THF) solution, this species is oxidized by air yielding the diamagnetic, dinuclear deep green (phenoxyl)copper(II) complex [Cu2(Ls )2]X2 (X = C1,C104) as microcrystalline solid and H202. Although both compounds have... 

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