Bidentate iminophosphorane-NHC ligand derived from the imidazo[1,5- a ]pyridin-3-ylidene scaffold

• Published in: Organometallics
• Main Authors: Azouzi, Karim, Guyard-Duhayon, Carine, Benaissa, Idir, Lugan, Noël, Canac, Yves, Bastin, Stéphanie, César, Vincent
• Other Authors: Laboratoire de chimie de coordination (LCC), Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie - CNRS Chimie (INC-CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS), ANR-16-CE07-0006,GOLDWAR,Catalyse asymétrique en présence de complexes d'or(I) et d'or(III) – Un nouvel arsenal pour la construction d'architectures moléculaires chirales(2016)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: Carbene compounds; Anions; Metals; Ligands; Carbon; [CHIM.COOR]Chemical Sciences/Coordination chemistry; IPY
• Online Access: https://hal.science/hal-02128330; https://doi.org/10.1021/acs.organomet.8b00733

International audience The synthesis of the bifunctional iminophosphorane-NHC (1) based on the imidazo[1,5-a]pyridin-3-ylidene (IPy) platform is reported. Its imidazo[1,5-a]pyridinium salt precursor [1·H](X) was readily obtained by an efficient three-component coupling reaction between 5-bromoimidazo[1,5-a]pyridinium bromide, sodium azide, and triphenylphosphine according to a SNAr/Staudinger reaction sequence. The stable free carbene 1 was generated by deprotonation of [1·H](X) with potassium bis(trimethylsilyl)amide, and its coordination ability toward various transition-metals was evaluated, either upon direct metalation of the free carbene or by transmetalation from a silver(I) NHC complex. While the ligand 1 is singly bounded through the carbene carbon atom in the latter complex, it behaves as a chelating bidentate ligand in all other complexes that were prepared, including the cationic and neutral palladium(II) complexes [Pd(allyl)(κ2C,N-1)](OTf) ([5](OTf)) and [PdCl2(κ2C,N-1)] (7), and the cationic rhodium(I) complexes [Rh(cod)(κ2C,N-1)](OTf) ([8](OTf)) and [Rh(CO)2(κ2C,N-1)](OTf) ([9](OTf)), generating stable 5-membered metallacycles. IR νCO measurements carried out on the complex [Rh(CO)2(κ2C,N-1)](OTf) ([9](OTf)) show evidence of the strong donating character of the iminophosphorane-NHC ligand 1.