An indium(I) tetramer bound by anionic N-heterocyclic olefins: ambiphilic reactivity, transmetallation and a rare indium-imide.

An organometallic tetrahedron-shaped indium(I) tetramer [(MeIPrCH)In]4 (MeIPrCH = [(MeCNDipp)2CCH]-; Dipp = 2,6-iPr2C6H3) supported by anionic N-heterocyclic olefin (aNHO) ligands is reported. The monomeric unit of this species exhibits both Lewis acidic and basic character at indium, while the steric profile of the aNHO ligand enables isolation of a rare monomeric imide, RInNR'.

Zinc-Mediated Transmetalation as a Route to Anionic N-Heterocyclic Olefin Complexes in the p-Block.

Anionic N-heterocyclic olefins (aNHOs) are suited well for the stabilization of low-coordinate inorganic complexes, due to their steric tunability and strong σ- and π-electron donating abilities. In this study, the new two-coordinate zinc complex (MeIPrCH)2Zn (MeIPrCH = [(MeCNDipp)2C═CH]-, Dipp = 2,6-diisopropylphenyl) is shown to participate in a broad range of metathesis reactions with main group element-based halides and hydrides. In the case of the group 14 halides, Cl2E·dioxane (E = Ge and Sn), transmetalation occurs to form dinuclear propellane-shaped cations, [(MeIPrCHE)2(µ-Cl)]+, while the aNHO-capped phosphine ligand MeIPrCH-PPh2 is obtained when (MeIPrCH)2Zn is combined with ClPPh2. Lastly, ZnH2 elimination drives transmetalation between (MeIPrCH)2Zn and hydroboranes and hydroalumanes, leading to Lewis acidic aNHO-supported -boryl and -alane products.

N-Heterocyclic Olefin-Ligated Palladium(II) Complexes as Pre-Catalysts for Buchwald-Hartwig Aminations.

New N-heterocyclic olefins (NHOs) are described with functionalization on the ligand heterocyclic backbone and terminal alkylidene positions. Various PdII -NHO complexes have been formed and their use as pre-catalysts in Buchwald-Hartwig aminations was explored. The most active system for catalytic C-N bond formation between hindered arylamine and arylhalide substrates was accessed by combining a backbone methylated NHO with [Pd(cinnamyl)Cl]2 in the presence of NaOtBu as a base. In these active systems evidence suggests that catalysis is mediated by colloidal palladium metal, highlighting a different coordination ability of NHOs in comparison with commonly used N-heterocyclic carbene co-ligands.

Organocatalytic hydroborylation promoted by N-heterocyclic olefins.

New complexes containing N-heterocyclic vinylene-stabilized [B2H5]+ fragments were prepared, and surprisingly it was found that the precursor N-heterocyclic olefins (NHOs) could promote the mild (room temperature) catalytic hydroborylation of ketones and aldehydes. This finding represents an important addition to the burgeoning field of non-metal mediated catalysis.