The synthesis and isolation of a novel bimetallic species formed by reacting two equivalents of TMPLi with CuCl in the presence of Et2O are reported. X-ray crystallography reveals the Et2O-free tetranuclear aggregate (TMPCu)2(TMPLi)2>1, which formally results from the catenation of dimers of TMPLi and TMPCu. NMR spectroscopy confirms that, upon dissolution in hydrocarbon media, the crystals fail to form a conventional Gilman cuprate dimer. Instead they exhibit a spectrum which is consistent with that recently proposed for an isomer of dimeric Gilman cuprate. Moreover, while pre-isolated Gilman cuprate is inert to benzene solvent, this new isomer smoothly affects aromatic deprotonation to give mainly Ph(TMP)3Cu2Li2>3, which is formally a heterodimer of Gilman cuprate TMPCu(μ-TMP)Li >2 and PhCu(μ-TMP)Li >4. Attempts to synthesise >3 through explicit combination of pre-isolated >2 and >4 were successful; additionally, this permitted the preparation of Ph(TMP)3Cu3Li >5 and Ph(TMP)3CuLi3>7 when >4 was combined in 1 : 2 ratios with TMPCu or TMPLi, respectively. >5 was characterised as metallacyclic in the solid-state, its structural features resembling those in >3 but with reduced Li–π interactions. It also proved possible to perform Cu/Li exchange on >5 (using tBuOCu) to give a novel mixed organo(amido)copper species Ph(TMP)3Cu4>6. Remarkably, the unprecedented reactivity of >1 towards benzene is reproduced by heating a 1 : 1 mixture of TMPLi and TMPCu in the same solvent; this gives predominantly >3. On the other hand, mixtures which are rich in either Cu or Li can lead to the selective in situ formation of >5 or >7. Though crystallographic data on >7 could not be obtained, DFT calculations accurately corroborated the observed structures of >3 and >5 and could be used to support >7 having the same structure type, albeit with enhanced Li–π interactions. This was consistent with NMR spectroscopic data. However, in contrast to >3 and >5, for which 2D NMR spectroscopy indicated only conformational changes, >7 was additionally found to exhibit fluxionality in a manner consistent with a dissociative process.
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