Kimura Yoshitaka, Lugo-Fuentes Leonardo I, Saito Souta, Jimenez-Halla J Oscar C, Barroso-Flores Joaquín, Yamamoto Yohsuke, Nakamoto Masaaki, Shang Rong
Department of Chemistry, Graduate School of Advanced Science and Engineering, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, 739-8526, Japan.
Department of Chemistry, Division of Natural and Exact Sciences, University of Guanajuato, Campus Gto, Noria Alta s/n 36050, Guanajuato, Mexico.
Dalton Trans. 2022 May 24;51(20):7899-7906. doi: 10.1039/d2dt01083f.
Stabilization of low oxidation gold anions as aurate or auride by organic ligands has long been a synthetic challenge, owing to the proneness of low-valent gold centres to cluster. Despite being the most electronegative metal, isolable gold(I) aurate complexes have only been obtained from a few σ-withdrawing organo- and organo-main group ligands. Stabilization of highly-reduced gold complexes by π-modulating redox active ligands has only been achieved by cyclic (amino)(alkyl)carbene (CAAC), which is limited to 1e-reduction to form neutral gold(0) complexes. This work reports a simple modular synthesis of a boron, nitrogen-containing heterocyclic carbene (BNC) at a gold(I) center through metal-assisted coupling between azadiboriridine and isocyanides. The anionic electrophilic BNC ligand in the gold(I) complex [(BNC)AuPMe] (3a and 3b) allows a 2e-reduction to form the first η-carbene aurate complex [(BNC)AuPMe]Li(DME) (5a, DME = dimethoxyethane). Single crystal crystallographic analysis and computational studies of these complexes revealed a highly π-withdrawing character of the neutral 4π B,N-heterocyclic carbene (BNC) moiety and a 6π weakly aromatic character with π-donating properties to the gold(I) fragment in its reduced form, showcasing the first cyclic carbene ligand that allows electronic tunability between π-withdrawing (Fischer-type)- and π-donating (Schrock-type) properties.
