Lithium dimethylcuprate exists as a
dimer in
diethyl ether forming an 8-membered ring. Similarly, lithium diphenylcuprate crystallizes as a dimeric etherate, [{Li(OEt2)}(CuPh2)]2.[5]
For the higher order cyanocuprate Li2CuCN(CH3)2, the cyanide ligand is coordinated to Li and π-bound to Cu.[7]
Mixed cuprates
More useful generally than the Gilman reagents are the so-called mixed cuprates with the formula [RCuX]− and [R2CuX]2−. Such compounds are often prepared by the addition of the organolithium reagent to copper(I) halides and cyanide. These mixed cuprates are more stable and more readily purified.[8] One problem addressed by mixed cuprates is the economical use of the alkyl group. Thus, in some applications, the mixed cuprate has the formula Li 2[Cu(2-thienyl)(CN)R] is prepared by combining thienyllithium and cuprous cyanide followed by the organic group to be transferred. In this higher order mixed cuprate, both the cyanide and thienyl groups do not transfer, only the R group does.[9]
^H. Hope; M. M. Olmstead; P. P. Power; J. Sandell; X. Xu (1985). "Isolation and x-ray crystal structures of the mononuclear cuprates [CuMe2−, [CuPh2−, and [Cu(Br)CH(SiMe3)2−". Journal of the American Chemical Society. 107 (14): 4337–4338.
doi:
10.1021/ja00300a047.
^Bruce H. Lipshutz; Brian James (1994). "New 1H and 13C NMR Spectral Data on "Higher Order" Cyanocuprates. If the Cyano Ligand Is Not On Copper, Then Where Is It?". J. Org. Chem.: 7585–7587.
doi:
10.1021/jo00104a009.{{
cite journal}}: CS1 maint: multiple names: authors list (
link)
^Steven H. Bertz, Edward H. Fairchild, Karl Dieter, "Copper(I) Cyanide" in Encyclopedia of Reagents for Organic Synthesis 2005, John Wiley & Sons.
doi:
10.1002/047084289X.rc224.pub2
^Bruce H. Lipshutz, Robert Moretti, Robert Crow "Mixed Higher-order Cyanocuprate-induced Epoxide Openings: 1-Benzyloxy-4-penten-2-ol" Org. Synth. 1990, volume 69, pp. 80.
doi:
10.15227/orgsyn.069.0080