229171-03-3Relevant academic research and scientific papers
Aminocarbene Complexes as Intermediates in the Ruthenium-Assisted Aminolysis of Phenylacetylene to Isonitriles and Toluene
Bianchini, Claudio,Masi, Dante,Romerosa, Antonio,Zanobini, Fabrizio,Peruzzini, Maurizio
, p. 2376 - 2386 (2008/10/08)
Various primary amines and NH3 have been found to react in THF with the Ru(II) vinylidene complex fac,cis-[(PNP)RuCl2{C=C(H)Ph}], affording aminocarbene derivatives of the general formula fac,cis-[(PNP)RuCl2{C(NHR)(CH2Ph)}] (PNP = CH3CH2CH2N(CH2-CH 2PPh2)2; R = CH3CH2CH2) Ph, cyclo-C6H11, (R)-(+)-CH(Me)(Ph), (R)-(-)-CH(Me)(Et), (S)-(-)-CH(Me)(1-naphthyl), H). With piperidine as the starting material, the tertiary aminocarbene /ac,cis-[(PNP)RuCl2{C(NC5H10)(CH 2Ph)}] has been obtained. The aminocarbene complexes are formed through an unforeseen mechanism in which 2 equiv of amine is involved: one serves to deprotonate the vinylidene Cβ carbon atom, while the other coordinates the metal center and then brings about an intramolecular nucleophilic attack onto the Cα carbon atom of a σ-phenylethynyl ligand. The (phenylethynyl)amine intermediates have been isolated and characterized. The aminocarbene derivative foc,cis-[(PNP)RuCl2-{C(NH(S)-(-)-CH(Me)(1-naphthyl)XCH 2Ph)}] has been authenticated by a single-crystal X-ray diffraction analysis. Upon thermolysis in wet solvents, generally THF, the secondary aminocarbene complexes generate toluene and transform quantitatively into the corresponding isonitrile derivatives fac,cis-[(PNP)RuCl2(C=NR)] (R = CH3CH2CH2) Ph, cyclo-C6H11, (R)-(+)-CH(Me)Ph, (R)-(-)-CH(Me)Et). In contrast, the primary aminocarbene fac,cis-[(PNP)-RuCl2{C(NH2)(CH2Ph)}] and the tertiary aminocarbene [(PNP)RuCl2{C(NC5H10)(CH2Ph)}] are thermally stable up to 150°C. The mechanism for the aminocarbene to isonitrile conversion has been found to involve the intermediacy of iminoacyl and (benzyl)isonitrile Ru(II) compounds, which have been intercepted and identified from independent reactions.
