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Updated: Dec 20, 2025

Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
Stereoelectronic Profiling of Acyclic Diamino Carbenes (ADCs)
Chandan Singh1, Anuj Kumar1, Han Vinh Huynh1
1Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543.
Abstract:
A library of 14 heterobis(carbene) complexes of the general formula [Au(Pr2-bimy)(ADC)]BF4 (7-20) containing the N-heterocyclic carbene reporter Pr2-bimy and various protic acyclic diaminocarbenes (ADCs) have been prepared to estimate their stereoelectronic properties by 13C NMR spectroscopy and percentage buried volume (%Vbur) determinations. Their preparation was achieved by nucleophilic attack of five secondary amines on six mixed NHC/isocyanide complexes of the type [Au(Pr2-bimy)(CN-R)]BF4 (1-6). Analyses of the Pr2-bimy carbene signals reveal that protic ADCs are stronger donors than classical and expanded-ring NHCs. On the other hand, they are weaker donating compared to NHCs with reduced-heteroatom stabilization. Moreover, stereoelectronic fine-tuning of these ligands is possible by a diverse range of substituents originating from the employed isocyanides and amines.
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