Ionization of gold (γ-methoxy)vinyl complexes generates reactive gold vinyl carbene complexes† †Electronic supplementary information (ESI) available: Experimental procedures, characterization data, and scans of NMR spectra. CCDC 1897597. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c9sc01574d

• Published in: Chemical science (Cambridge) Vol. 10; no. 24; pp. 6149 - 6156
• Main Authors: Kim, Nana, Widenhoefer, Ross A.
• Format: Journal Article
• Language: English
• Published: Royal Society of Chemistry 10-05-2019
• Subjects: Chemistry
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/c9sc01574d

Highly reactive cationic gold vinyl carbene/allylic cation complexes are generated in solution
via
γ-ionization of gold vinyl complexes.
Cationic gold vinyl carbene/allylic cation complexes of the form (
E
)-[(L)AuC(H)C(H)CAr
2
]
+
OTf
–
{L = IPr, Ar = Ph [(
E
)-
5a
], L = IPr, Ar = 4-C
6
H
4
OMe [(
E
)-
5b
], L = P(
t
-Bu)
2
o
-biphenyl, Ar = 4-C
6
H
4
OMe [(
E
)-
5c
]} were generated in solution
via
Lewis acid-mediated ionization of the corresponding gold (γ-methoxy)vinyl complexes (
E
)-(L)AuC(H)C(H)C(OMe)Ar
2
at or below –95 °C. Complexes (
E
)-
5b
and (
E
)-
5c
were fully characterized in solution employing multinuclear NMR spectroscopy, which established the predominant contribution of the aurated allylic cation resonance structure and the significant distribution of positive charge into the γ-anisyl rings. Complex (
E
)-
5b
reacted rapidly at –95 °C with neutral two-electron, hydride, and oxygen atom donors exclusively at the C1 position of the vinyl carbene moiety and with
p
-methoxystyrene to form the corresponding vinylcyclopropane. In the absence of nucleophile (
E
)-
5a
decomposed predominantly
via
intermolecular carbene dimerization whereas formation of 1-aryl-5-methoxy indene upon ionization of (
Z
)-(IPr)AuC(H)C(H)C(OMe)(4-C
6
H
4
OMe)
2
[(
Z
)-
6b
] implicated an intramolecular Friedel–Crafts or electrocyclic Nazarov pathway for the decomposition of the unobserved vinyl carbene complex (
Z
)-[(IPr)AuC(H)C(H)C(4-C
6
H
4
OMe)
2
]
+
OTf
–
[(
Z
)-
5b
].