Stabilized Carbenium Ions as Latent, Z‐type Ligands

Controlling the reactivity of transition metals using secondary, σ‐accepting ligands is an active area of investigation that is impacting molecular catalysis. Herein we describe the phosphine gold complexes [(o‐Ph2P(C6H4)Acr)AuCl]+ ([3]+; Acr=9‐N‐methylacridinium) and [(o‐Ph2P(C6H4)Xan)AuCl]+ ([4]+;...

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Bibliographic Details
Published in:Angewandte Chemie International Edition 2019-12, Vol.58 (50), p.18266-18270
Main Authors: Wilkins, Lewis C., Kim, Youngmin, Litle, Elishua D., Gabbaï, François P.
Format: Article
Language:English
Subjects:
Acidic oxides
Acidity
alkynes
carbocations
Catalysis
Dichlorides
Gold
Gold chloride
Heavy metals
Ligands
Metals
Oxidation
oxidative addition
Phosphine
Phosphines
Transition metals
Z-type ligands
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Summary:Controlling the reactivity of transition metals using secondary, σ‐accepting ligands is an active area of investigation that is impacting molecular catalysis. Herein we describe the phosphine gold complexes [(o‐Ph2P(C6H4)Acr)AuCl]+ ([3]+; Acr=9‐N‐methylacridinium) and [(o‐Ph2P(C6H4)Xan)AuCl]+ ([4]+; Xan=9‐xanthylium) where the electrophilic carbenium moiety is juxtaposed with the metal atom. While only weak interactions occur between the gold atom and the carbenium moiety of these complexes, the more Lewis acidic complex [4]+ readily reacts with chloride to afford a trivalent phosphine gold dichloride derivative (7) in which the metal atom is covalently bound to the former carbocationic center. This anion‐induced AuI/AuIII oxidation is accompanied by a conversion of the Lewis acidic carbocationic center in [4]+ into an X‐type ligand in 7. We conclude that the carbenium moiety of this complex acts as a latent Z‐type ligand poised to increase the Lewis acidity of the gold center, a notion supported by the carbophilic reactivity of these complexes. Like in a capacitor about to arc, the positive face of the xanthylium cation installed in a new ambiphilic ligand architecture stands set to engage the adjacent gold center in a Au→Ccarbenium interaction. This interaction shows that stabilized carbenium ions may act as latent Z‐type ligands, which, in the present case, enhance the carbophilic reactivity of the adjacent gold center.
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.201911662