Merging two evolving areas in synthesis, namely cooperative bimetallics and N-heterocyclic carbenes (NHCs), this study reports the isolation of the first intermediates of alkali-metal-mediated zincation (AMMZn) of a free NHC and a Zn–NHC complex using sodium zincate [(TMEDA)NaZn(TMP)(tBu)₂] (1) as a metallating reagent. The structural authentication of (THF)₃Na[:C{[N(2,6-iPr₂C₆H₃)]₂CHCZn(tBu₂)}] (2) and [Na(THF)₆]⁺[tBu₂Zn:C{[N(2,6-iPr₂C₆H₃)]₂CHCZn(tBu₂)}]⁻ (4), resulting from the reactions of 1 with unsaturated free NHC IPr (IPr = 1,3-bis(2,6-di-isopropylphenylimidazole-2-ylidene) and NHC complex ZntBu₂IPr (3) respectively demonstrates that in both cases, this mixed-metal approach can easily facilitate the selective C4 zincation of the unsaturated backbone of the NHC ligand. Furthermore, the generation of anionic NHC fragments enables dual coordination through their normal (C2) and abnormal (C4) positions to the bimetallic system, stabilising the kinetic AMMZn intermediates which normally go undetected and provides new mechanistic insights in to how these mixed-metal reagents operate. In stark contrast to this bimetallic approach when NHC-complex 3 is reacted with a more conventional single-metal base such as tBuLi, the deprotonation of the coordinated carbene is inhibited, favouring instead, co-complexation to give NHC-stabilised [IPr·LiZntBu₃] (5). Showing the potential of 2 to act as a transfer agent of its anionic NHC unit to transition metal complexes, this intermediate reacts with two molar equivalents of [ClAu(PPh₃)] to afford the novel digold species [ClAu:C{[N(2,6-iPr₂C₆H₃)]₂CHCAu(PPh₃)}] (6) resulting from an unprecedented double transmetallation reaction which involves the simultaneous exchange of both cationic (Na⁺) and neutral (ZntBu₂) entities on the NHC framework.

Meta – meta metalation: Remarkably, toluene can be directly dimanganated or dimagnesiated at the 3,5‐positions using bimetallic bases with active Me₃SiCH₂ ligands (see scheme, blue). In contrast, n‐butyl ligands lead to 2,5‐metalation (red). tmp=2,2,6,6‐tetramethylpiperidide.

Organometallic bismuth(v) and antimony(v) α-hydroxy carboxylato complexes, [MPh₃(O₂CR(OH))₂] and [MPh₃(O₂CR(O))], have been synthesised, characterised and their activity towards Leishmania promastigotes and amastigotes, and human fibroblast cells, assessed and compared.

Extending the recently introduced concept of “alkali‐metal‐mediated manganation” to functionalised arenes, the heteroleptic sodium manganate reagent [(tmeda)Na(tmp)(R)Mn(tmp)] (1; TMEDA=N,N,N′,N′‐tetramethylethylenediamine, TMP=2,2,6,6‐tetramethylpiperidide, R=CH₂SiMe₃) has been treated with anisole or N,N‐diisopropylbenzamide in a 1:1 stoichiometry in hexane. These reactions afforded the crystalline products [(tmeda)Na(tmp)(o‐C₆H₄OMe)Mn(tmp)] (2) and [(tmeda)Na(tmp){o‐{C(O)N(iPr)₂C₆H₄}Mn(CH₂SiMe₃)] (3), respectively, as determined from X‐ray crystallographic studies. On the basis of these products, it can be surmised that reagent 1 has acted, at least partially and ultimately, as an alkyl base in the first reaction liberating the silane Me₄Si, but as an amido base in the second reaction liberating the amine TMPH. Both of these paramagnetic products 2 and 3 have contacted ion‐pair structures, the key features of which are six‐atom, five‐element (NaNMnCCO) and seven‐atom, five‐element (NaNMnCCCO) rings, respectively. Manganates 2 and 3 were successfully cross‐coupled with iodobenzene under [PdCl₂(dppf)] (dppf=1,1′‐bis(diphenylphosphino)ferrocene) catalysis to generate unsymmetrical biaryl compounds in yields of 98.0 and 66.2 %, respectively. Emphasizing the importance of alkali‐metal mediation in these manganation reactions, the bisalkyl Mn reagent on its own fails to metalate the said benzamide, but instead produces the monomeric, donor–acceptor complex [Mn(R)₂{(iPr)₂NC(Ph)(O)}₂] (5), which has also been crystallographically characterised. During one attempt to repeat the synthesis of 2, the butoxide‐contaminated complex [{(tmeda)Na(R)(OBu)(o‐C₆H₄OMe)Mn}₂] (6) was obtained. In contrast to 2 and 3, due to reduced steric constraints, this complex adopts a dimeric arrangement in the crystal, the centrepiece of which is a twelve atom (NaOCCMnC)₂ ring.

A series of organometallic bismuth(v) dicarboxylates, [BiPh₃(O₂CR′)₂], were synthesised and evaluated for their anti-leishmanial activity. The complexes are effective against parasite promastigotes (0.6–2.5 μM), but prone to slow reductive decomposition.