Uncatalyzed hydroamination of electrophilic organometallic alkynes: fundamental, theoretical, and applied aspects.
Simple reactions of the most used functional groups allowing two molecular fragments to link under mild, sustainable conditions are among the crucial tools of molecular chemistry with multiple applications in materials science, nanomedicine, and organic synthesis as already exemplified by peptide synthesis and "click" chemistry. We are concerned with redox organometallic compounds that can potentially be used as biosensors and redox catalysts and report an uncatalyzed reaction between primary and secondary amines with organometallic electrophilic alkynes that is free of side products and fully "green". A strategy is first proposed to synthesize alkynyl organometallic precursors upon addition of electrophilic aromatic ligands of cationic complexes followed by endo hydride abstraction. Electrophilic alkynylated cyclopentadienyl or arene ligands of Fe, Ru, and Co complexes subsequently react with amines to yield trans-enamines that are conjugated with the organometallic group. The difference in reactivities of the various complexes is rationalized from the two-step reaction mechanism that was elucidated through DFT calculations. Applications are illustrated by the facile reaction of ethynylcobalticenium hexafluorophosphate with aminated silica nanoparticles. Spectroscopic, nonlinear-optical and electrochemical data, as well as DFT and TDDFT calculations, indicate a strong push-pull conjugation in these cobalticenium- and Fe- and Ru-arene-enamine complexes due to planarity or near-planarity between the organometallic and trans-enamine groups involving fulvalene iminium and cyclohexadienylidene iminium mesomeric forms.
ISM, UMR CNRS 5255, Univ. Bordeaux, 351 Cours de la Libération, 33405 Talence Cedex (France).
Yanlan
Y
Wang
Camille
C
Latouche
Amalia
A
Rapakousiou
Colin
C
Lopez
Isabelle
I
Ledoux-Rak
Jaime
J
Ruiz
Jean-Yves
JY
Saillard
Didier
D
Astruc
D000480:Alkynes / Q000737:chemistry*; D000586:Amination; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*
D000480:Alkynes; D009942:Organometallic Compounds
Co; alkynes; enamines; green chemistry; push-pull