The Anionic Pathway in the Nickel-Catalysed Cross-Coupling of Aryl Ethers

The Ni-catalysed cross-coupling of aryl ethers is a powerful method to forge new C-C and C-heteroatom bonds. However, the inert C(sp(2))-O bond means that a canonical mechanism that relies on the oxidative addition of the aryl ether to a Ni-0 centre is thermodynamically and kinetically unfavourable, which suggests that alternative mechanisms may be involved. Here, we provide spectroscopic and structural insights into the anionic pathway, which relies on the formation of electron-rich hetero-bimetallic nickelates by adding organometallic nucleophiles to a Ni-0 centre. Assessing the rich co-complexation chemistry between Ni(COD)(2) and PhLi has led to the structures and solution-state chemistry of a diverse family of catalytically competent lithium nickelates being unveiled. In addition, we demonstrate dramatic solvent and donor effects, which suggest that the cooperative activation of the aryl ether substrate by Ni-0-ate complexes plays a key role in the catalytic cycle.