Fischer carbene complexes of cobalt(I): Synthesis and structure

https://doi.org/10.1016/j.molstruc.2021.132093Get rights and content
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Highlights

  • Cobalt Fischer carbene complexes containing different (hetero)aryl and heteroatom substituents were synthesized.

  • NMR spectroscopic and SC-XRD studies indicated carbene stabilization from the remote amine moiety of the dimethylaniline carbene ligands.

  • Increased contribution of the thienyl-S atom to carbene stabilization was observed for the ethoxycarbene complex.

Abstract

Three different aryl substrates thiophene (ThH), ferrocene (FcH) and p-bromodimethylaniline (p-DMABr) were lithiated and reacted with [Co(CO)4SnPh3], according to the Fischer carbene protocol. The products [CoSnPh3(CO)3{C(OEt)R}] (R =Th, 1, p-DMA, 2 and R = Fc, 3) were analysed to unravel the role of the aryl carbene substituent in stabilizing intermediates and final products. The ethoxy carbene complexes were aminolysed by in situ generated HNMe2 to afford [CoSnPh3(CO)3{C(NMe2)R}] (R =Th, 4, p-DMA, 5) and with N,N-dimethylethylenediamine [CoSnPh3(CO)3{C(NHCH2CH2NMe2)R}] (R = p-DMA, 6) in high yields. The trigonal Co(CO)3 in the equatorial plane is very stable and efforts to displace a carbonyl in 6 was unsuccessful, both by heating and irradiation. The role of the aryl carbene substituents in stabilizing the electrophilic carbene carbon was investigated and studied by NMR spectroscopy in solution and single crystal X-ray structure determinations.

Keywords

Fischer carbene
Cobalt carbonyl
Carbene complex substituents
Aminocarbene
Alkoxycarbene

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