An Entry to Mixed NHC-Fischer Carbene Complexes and Zwitterionic Group 6 Metal Alkenyls

作者：Sierra Miguel A^*; Merinero Alba D; Giner Elena A; Gomez Gallego Mar^*; Ramirez de Arellano Carmen

来源：Chemistry - A European Journal, 2016, 22(38): 13521-13531.

DOI：10.1002/chem.201601735

• bisylidenes
• carbenes
• N-heterocyclic carbenes
• radical cations
• zwitterions

The addition of NHCs to alpha,beta-unsaturated Cr-0 and W-0 (Fischer) carbene complexes is strongly dependent on the electrophilicity of the carbene carbon. Electrophilic alkoxy-carbene complexes quantitatively react with NHCs to yield stable zwitterionic (racemic) Cr-0- and W-0-alkenyls with total regio- and E-stereoselectivity. Less electrophilic amino-carbenes react with NHCs to promote the displacement of a CO ligand and yield "mixed" NHC/Fischer biscarbenes in a process that is unprecedented in group 6 metal-carbene chemistry. In fact, the compounds prepared, are some of the scarce examples of Fischer bisylidenes reported in the literature. The electrochemistry of the zwitterionic Cr-0- and W-0-alkenylcomplexes made, show that these compounds have a strong reductor character, which is demonstrated in their reactions towards [Ph3C][PF6]. The oxidation processes lead to new types of cationic Fischer mono-and biscarbene complexes having a charged NHC fragment in their structures, in a new example of the use of electron-transfer reactions as a method to prepare novel group 6 (Fischer) carbene complexes.

• 出版日期2016-9