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An Entry to Mixed NHC–Fischer Carbene Complexes and Zwitterionic Group 6 Metal Alkenyls
Author(s) -
Sierra Miguel A.,
Merinero Alba D.,
Giner Elena A.,
GómezGallego Mar,
Ramírez de Arellano Carmen
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201601735
Subject(s) - carbene , electrophile , chemistry , cationic polymerization , transition metal carbene complex , alkoxy group , medicinal chemistry , yield (engineering) , ligand (biochemistry) , metal , stereoselectivity , electrophilic addition , main group element , reactivity (psychology) , polymer chemistry , organic chemistry , alkyl , transition metal , catalysis , materials science , medicine , biochemistry , receptor , alternative medicine , pathology , metallurgy
The addition of NHCs to α,β‐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 aminocarbenes 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 [Ph 3 C][PF 6 ]. 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.