Ionic Aggregates of Lithium Organocuprates

Abstract

We have used a combination of electrospray ionization mass spectrometry and electrical conductivity measurements to analyze solutions of the Gilman cuprates LiCuR2·LiX, with R=Ph, Bu and X=Cl, Br, I, in tetrahydrofuran and have compared our findings with previous results on cyanocuprates LiCuR2·LiCN. Among the various polynuclear organocuprate ions observed, Li2Cu3Ph6(-), LiCu4Ph6(-), and Cu5Ph6(-) are of particular interest because aggregates of the same composition are known from X-ray crystal structures. Control experiments have indicated that the polynuclear organocuprate anions detected in solution are indeed identical to those formed in the solid state. As abundant ions of the type Li2Cu3R6(-) are found in solutions of Gilman cuprates and cyanocuprates alike, their possible involvement in organocuprate reactions should be considered. For comparison, we have also included solutions of LiCu(R)I, LiCuX2·LiX, LiCuX2, and CuCN·2LiX in the present study.

Aplysiasecosterol A: A 9,11‐Secosteroid with an Unprecedented Tricyclic γ‐Diketone Structure from the Sea Hare Aplysia kurodai

“…Similar anionic cuprate clusters including [Cu 4 (μ‐SCH 2 Ph) 6 ] 2− and [Cu 5 Ph 6 ] − have been reported as intermediaries in closely related copper‐catalysed CS bond forming reactions and also in studies relating to Gilman cuprate reagents 77. 78…”

Unravelling the hidden link of lithium halides and application in the synthesis of organocuprates

“…The lithium salts may have an effect on the formation of organocuprates, which has been awaked by several groups21343536373839. Although knowing this phenomenon for a long time, determination of the exact structure, the role for Li X and application in organocuprates have still been not well researched.…”

“…and Koszinowski and colleagues34 have pointed out the Li X could have a positive effect on the solubility of Cu X ( X =I, Br, Cl, CN) independently. The electrospray ionization–mass spectrometry was used to study the structure of formed ate complex2134. However, determination of the exact structure, the role for Li X and application in organocuprates have still been not well-studied up to date.…”

“…Lipshutz et al 21. and Koszinowski and colleagues34 have pointed out the Li X could have a positive effect on the solubility of Cu X ( X =I, Br, Cl, CN) independently. The electrospray ionization–mass spectrometry was used to study the structure of formed ate complex2134.…”

Intermediates Formed in the Reactions of Organocuprates with α,β‐Unsaturated Nitriles

“…The relative abundances of the adducts Li n −1 Cu n Bu 2 n (FN) n − closely resembled those of the free butylcuprate complexes Li n −1 Cu n Bu 2 n − (high relative ESI signal intensities for the mono‐ and trinuclear complexes in THF, low signal intensity for the dinuclear ones) . This finding suggests that the structures of the organocuprate aggregates are not strongly perturbed by the coordination of fumaronitrile, but that they preserve the chain‐like and trigonal‐prismatic geometries previously deduced for free LiCu 2 R 4 − and Li 2 Cu 3 R 6 − anions, respectively (Figure ) …”