Gold(III) Alkyne Complexes: Bonding and Reaction Pathways

Abstract

The synthesis and characterization of hitherto hypothetical AuIII π‐alkyne complexes is reported. Bonding and stability depend strongly on the trans effect and steric factors. Bonding characteristics shed light on the reasons for the very different stabilities between the classical alkyne complexes of PtII and their drastically more reactive AuIII congeners. Lack of back‐bonding facilitates alkyne slippage, which is energetically less costly for gold than for platinum and explains the propensity of gold to facilitate C−C bond formation. Cycloaddition followed by aryl migration and reductive deprotonation is presented as a new reaction sequence in gold chemistry.

Do Gold(III) Complexes Form Hydrogen Bonds? An Exploration of AuIII Dicarboranyl Chemistry

“…Eventually the isocyanide complex 5 does react with silver trifluoroacetate in dichloromethane (2 days), to give the corresponding OAc F complex 6 (Scheme 2). However,w hereas in other cases of gold(III)-OAc F complexes the removal of trifluoroacetate with B(C 6 F 5 ) 3 provedt ob eamild and quantitative way to generate vacant coordination sites en route to synthesizingg old(III) alkenea nd alkyne complexes, [23,45,46] this procedure failed in (14); C(1)-Au-C(31) 94.17 (8),C (1)-Au-C(21) 175.48 (8), C(31)-Au-C(21) 88.58 (7), C(1)-Au-O(51) 89.35 (7),C(31)-Au-O(51) 176.36 (6), C(21)-Au-O(51) 87.85 (7). this case;f or example, monitoring mixtures of 6 and B(C 6 F 5 ) 3 and 1,2-bis(adamantyl)acetylene in CD 2 Cl 2 by 1 Ha nd 19 FNMR spectroscopy providedn oe videncef or OAc F displacement or alkyne binding.…”

Thermally Stable Gold(III) Alkene and Alkyne Complexes: Synthesis, Structures, and Assessment of the trans‐Influence on Gold–Ligand Bond Enthalpies

“…[6] This compound is the only example of a structurally characterised πalkene complex of gold(III), until now. Following our recent isolation of the first examples of gold(III) alkyne complexes, [7] including the crystallographic characterisation of an alkynyl complex of type C (Figure 1) which uses a bis-cyclometallated biphenyl-based C^C ligand framework to provide stability (C^C = 4,4′-di-t-butylbiphenyl-2,2′diyl), we decided to explore the potential of this dianionic C^C chelate ligand scaffold for the synthesis of π-alkene complexes and related reactive species. Biphenylyl ligands are attractive since they are resistant to reductive elimination, and indeed they were introduced into gold chemistry by Usón for this very reason several decades ago.…”

Gold-catalyzed heterocyclic syntheses through α-imino gold carbene complexes as intermediates

“…Although the reactions are initiated by alkyne coordination, only a few alkyne adducts of gold(III) have been characterized, because of their lability. Then, alkyne slippage occurs facilitating C-C triple bond polarization, 12 concomitantly to the regioselective attack of the nucleophile and formation of the gold carbene complex. Remarkably, the only example of a gold(III) carbene complex which has been isolated and characterized from a reaction of a gold(III) salt with an alkyne corresponds to a non-nitrogen-containing six-membered mesoionic species, reported by Bertrand et al…”