Organocopper, Silver, and Gold Compounds

Copper is another metal with a strong tendency (in its -i-l oxidation state) to participate in multicenter metal-carbon bonding, though the thermal instabil- 

The hypercarbon atom environment in this compound, with one silicon atom, two hydrogen atoms, and two copper atoms in the carbon coordination sphere, with a Cu-C-Cu bond angle of 74°, is consistent with the formation of three 2c-2e bonds to the silicon and hydrogen atoms, and a 3c-2e bond to the metal atoms. Hiis open cyclic structure, which may be contrasted with the more compact tetrahedral structures of typical tetrameric lithium alkyls, suggests that the metal atoms are sp hybridized, unable to make use of as many AOs as lithium atoms can. 

For example, the 2-dimethylaminomethyl-5-methylphenyl copper tetramer [CuC6H3(2-CH2NMe2)(5-Me)]4 contains p2-ligands of the type shown in structure 45a and a butterfly-shaped arrangement of its four metal atoms, whereas the ps-ligand environment is found in 2-dimethylaminophenyl copper compounds 45b. In both types of compounds, pairs of copper atoms are bridged by (hypercoordinate) carbon atoms of the type already noted in Al2Me4Ph2 

Compound 48 and the ferrocenyl-gold and ruthenocenyl-gold compounds 49 provide interesting examples of a hypercarbon atom that is not only part of an aromatic cyclopentadienyl ring system, in which it is bonded to two other carbon atoms, but also bonds simultaneously to the sandwiched iron atom and (by a 3c-2e bond) to the two coinage atoms. The related dication 50 has also been isolated.  

Severa] other gold complexes with Au-Au bonding contacts have been prepared and characterized The cyclic structure 51 was proposed on the basis of NMR and Au Mossbauer data Cation 52 was an early bridged aryl-gold complex to receive full X-ray structural characterization The acute Au-C-Au angle and the bond distances are characteristic features of such complexes and very close to those determined for dication 53  

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