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Aminocarbyne ligands in organometallic chemistry

“…Protonation of isocyanides in di-and tri-metallic compounds is usually carried out with strong, poorly coordinating, Brønsted acids such as CF3SO3H, HPF6, HBF4, HClO4, HI, HCl or [HOEt2][BAr F ], in mixed aqueous-organic or in strictly anhydrous organic solvents [93,103,112,113,172,173,200,201,202,203,204]. Compound [{Fe2Cp2(CO)3}2(μ-1,2-diisocyanobenzene)] is another stark example of different behavior towards protonation and alkylation.…”

“…Analogous reactions were performed with [Os3(CO)10(CNR)(NCMe)] and propiolic acid [211], 1hydroxybenzotriazole [212], 1-hydroxypyridine-2-thione [213] and hydrogen chloride in aprotic solvents (Scheme 39b) [200]. In the products 93, the deprotonated reagent is found as a ligand bridging two osmium atoms which are no longer connected by a metal-metal bond.…”

“…Thus, a weaker acid, such as HCl in dichloromethane, initially affords the hydride product which then equilibrates with the aminocarbyne isomer. In a less polar solvent (cyclohexane), the product ratio shifts towards the aminocarbyne [200]. Concerning the nature of the isocyanide substituent, electron-withdrawing groups (Ph > Bn > Pr) favor the formation of the aminocarbyne.…”