Metal exchange in lithiocuprates: implications for our understanding of structure and reactivity

Abstract

A new class of lithium cyanatocuprates are elucidated whose structures reveal a preference by copper for lower order structure formation.

A new route for the efficient metalation of unfunctionalized aromatics

“…3, top) reveals a subsidiary peak at δ 0.90 ppm, identified as 2 , and two dominant resonances, at δ 1.41 and –2.93 ppm (in a 1 : 1 integral ratio). The former of these two signals falls within the chemical shift range expected for a Li + center bridging two amido ligands (as observed previously in amidocuprates) 36. On the other hand, the resonance δ –2.93 ppm indicates some degree of Li···π interaction 39–41.…”

“…7 Li NMR spectroscopy revealed a dominant singlet, at δ 1.64 ppm, alongside a very minor resonance, at δ 0.95 ppm. The former of these is consistent with the single Li-environment in 1 whereas the minor resonance has previously been interpreted as belonging to a Cu-rich species such as (TMP) 4 Cu 3 Li 36. 13 C NMR spectroscopy revealed a spectrum consistent with the three different TMP environments in 1 , most clearly evidenced by the TMP-2,6 carbon resonances, at δ 56.9, 54.2 and 52.0 ppm.…”

“…1b). 30 In recent work, we have proposed the existence of this isomer from solution-state data 36. Evidence that this species corresponds to 1 as isolated in this work was gathered from 1 H NMR spectroscopy.…”

“…By extension, these data caused us to propose the existence of an isomeric variant on the dimer of a previously reported30 Gilman cuprate (Fig. 1b) in which metal ions of the same type, instead of being located opposite to one another in the 8-membered metallacyclic core, reside adjacent to one another 36. Herein we report on the isolation of this species and its characterisation in the solid state.…”

“… 29 This observation, combined with a debate over bonding of the salt anion, 33 has meant that while Li-salt incorporating cuprates have been studied in some detail, 34 Li-salt free cuprates have been subject to less exploration. 35 , 36 To the best of our knowledge, only two examples of unsolvated bis(amido) Gilman cuprates, (amido) 2 CuLi, have been characterised in the solid state. 30 , 37 In contrast to its Lipshutz-type analogues (TMP) 2 Cu(X)Li 2 (X = CN, halide, SCN, OCN; Fig.…”