Bidentate iminophosphorane-NHC ligand derived from the imidazo[1,5- a ]pyridin-3-ylidene scaffold
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-bromoimidaz...
Published in: | Organometallics |
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Main Authors: | , , , , , , |
Other Authors: | , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
HAL CCSD
2018
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Subjects: | |
Online Access: | https://hal.science/hal-02128330 https://doi.org/10.1021/acs.organomet.8b00733 |
Summary: | 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. |
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