Me2CuLi*LiCN in diethyl ether prefers a homodimeric core structure [Me2CuLi]2 and not a heterodimeric one [Me2CuLi*LiCN]:: 1H, 6Li HOE and 1H, 1H NOE studies by NMR

H-Li distances and H-1-H-1 dipolar interactions in Me2CuLi*LiCN and Me2CuLi in diethyl ether (Et2O), obtained by NMR spectroscopy, were used to gain structural information about the contact ion pair of the salt-containing organocuprate Me2CuLi*LiCN in this solvent. The H-Li distances of Me2CuLi*LiCN and Me2CuLi in Et2O, resulting from the initial buildup rates in conjunction with the motional correlation times, are almost identical, indicating a similar homodimeric core structure [Me2CuLi](2) for both samples. However, the H-Li distances obtained for Me2CuLi*LiCN do not rigorously exclude a heterodimeric. structure [Me2CuLi*LiCN] as proposed by ab initio calculations. Therefore, H-1-H-1 dipolar interactions were investigated by SYM-BREAK-NOE/ROE-HSQC experiments, which allow for the observation of NOEs between equivalent protons. Since these experiments showed similar H-1-H-1 dipolar interactions Of Me2CuLi*LiCN and Me2CuLi, we propose that for Me2CuLi*LiCN a homodimeric core structure [Me2CuLi](2), indeed is predominant in Et2O.