Back to bases: Conventional organometallic bases usually deprotonate toluene at the methyl position to generate resonance‐stabilized benzyl anions, but using a new type of bimetallic metalation, sodium‐mediated magnesiation, the thermodynamic position for deprotonation can be switched to the aromatic ring (see picture).

Benzene can be easily 1,4-dideprotonated stoichiometrically on reaction with two equivalents of a synergic mixture of tBu2Zn, NaTMP and TMEDA to give a unique 1,4-dizincated benzene product which has been characterised by X-ray crystallography and NMR spectroscopy as well as modelled theoretically by DFT computational studies; a related synergic dimagnesiation of benzene is also reported.

The reactivity of the Brønsted basic mixed-metal tris-amide compounds of empirical formula [MMg(N(i)Pr2)3] [where M = Li (1), Na (2)] towards phenylacetylene (HC[triple bond, length as m-dash]CPh) has been investigated and has led to the synthesis of a series of mixed-metal acetylido-amido-magnesiates. Thus, 1 and 2 molar equivalents of the alkyne with [MMg(N(i)Pr2)3] produce heteroanionic bis(amido)-mono(acetylido) [LiMg(N(i)Pr2)2(C[triple bond, length as m-dash]CPh)]2 (3) and mono(amido)-bis(acetylido) [(TMEDA) x Na(C[triple bond, length as m-dash]CPh)2Mg(N(i)Pr2)](2) (4) (TMEDA = N,N,N',N'-tetramethylethylenediamine) respectively. X-Ray crystallographic studies reveal that the new compounds adopt a different structural motif. Complex can be defined as an inverse crown structure, having a cationic eight-atom [(NaNMgN)2]2+ ring which hosts in its core two acetylido ligands. On the other hand, adopts a tetranuclear NaMgMgNa near-linear chain arrangement, held together by acetylido and amido bridges. The metal coordination geometries in both structures are distorted tetrahedral, and the sodium cations at the end of the mixed-metal chain carry terminal chelating TMEDA ligands. 1H and 13C NMR spectral data recorded in C6D6 solutions are also reported for and , and are consistent with the solid-state structures being retained in solution.

The new synergic base [PMDETA.K(TMP)(Et)Zn(Et)] selectively zincates 4-(dimethylamino)pyridine at the 2-position and 4-methoxypyridine at the 3-position, to afford bimetallic potassium pyridylzinc complexes each displaying a novel, but remarkably different, structure.

Introducing TMEDA to the lithium dimethyl(amido)zincates "LiZn(NR 2 )Me 2 " leads to a discrete ion-contacted zincate with TMEDA bound to lithium in the case of NR 2 ) TMP but to a noVel "inVerse zincate" with TMEDA bound to zinc in the case of NR 2 ) HMDS, where unexpectedly Me 2 Zn-(TMEDA) functions as a η 1 ,µ ligand to dimeric (LiHMDS) 2 molecules to afford a zigzag chain polymer. refinement to convergence on F 2 with all non-H atoms anisotropic gave R ) 0.0362 (F, 5965 obsd data only) and R w ) 0.0863 (F 2 , all data), GOF ) 1.028, 306 refined parameters. H atoms involved in agostic contacts were refined isotropically, but all other H atoms were placed in calculated positions and with riding modes. The maximum and minimum residual electron densities were 0.319 and -0.316 e Å -3 .