The reaction of (η⁵-cyclopentadienyl)dicarbonyliron(2-thienoyl) with acetylenes; a mechanistic study using proton nuclear magnetic resonance, and application in synthesis

Abstract

IAN R. BUTLER. Can. J. Chem. 68, 1979Chem. 68, (1990. The thermal reactions of dicarbonyl-r15-cyclopentadienyl(2-thienoyl)iron with a series of substituted acetylenes to give indenones and cyclopentathiophenones have been reinvestigated. The results obtained support a reaction mechanism involving initial acetylene insertion followed by that of carbon monoxide, in contradiction to the previously reported results. 'The reaction products were identified and characterized primarily using 2D 'H nmr spectroscopy.Key words: acetylene, carbon monoxide, iron, indenone, mechanism, thienyl.IAN R. BUTLER. Can. J. Chem. 68, 1979Chem. 68, (1990 On a rketudik les rkactions thermiques du dicarbonyl-r15-cyclopentadi~nyl(2-thienoyl)fer avec une skrie d'acktylknes substitukes qui conduisent ?i des indknones et ?i des cyclopentathiophtnones. Les rtsultats obtenus sont en accord avec un mkcanisme rkactionnel impliquant une insertion initiale de l'acetylkne, suivie de celle du monoxyde de carbone; ce mCcanisme est en contradiction avec les rksultats rapportks antkrieurement. Pour identifier et pour caracttriser les produits rkactionnels, on a principalement fait appel ?i la spectroscopic rmn du 'H en 2D.Mots clPs: acttylkne, monoxyde de carbone, fer, indtnone, mkcanisme, thienyle.[Traduit par la revue] IntroductionThe insertion of acetylenes into metal-carbon bonds is a synthetically useful procedure, although the mechanistic details of such processes are not fully understood. Recently we have elucidated some of the mechanistic features of one specific type of reaction in this class, namely that of the thermal reaction of dicarbonyl-q5-cyclopentadienyliron(I)aryls, FPAr, with diarylacetylenes to give [lw-2,3-diarylinden-1-ones, using deuterium labelled samples (1). A summary of the proposed mechanistic results is shown in Scheme 1, for the reaction of Fp(pheny1-d5) with diphenylacetylene. In addition to the indenone products, ferrocene and mono and l,lf-bis(pheny1-d5) ferrocene are observed as by-products, indicating the transfer of the a bound phenyl group to the q5-cyclopentadienyl ring. By studying the reactions (photochemical and thermal) of the related Fp(1-and 2-naphthoyl) compounds with diphenylacetylene, we were able to show that the insertion of the diarylacetylene precedes that of carbon monoxide, Scheme 2 (2). Moreover, by independent synthesis of the proposed intermediate, 4 (undeuterated) in Scheme 1, we were able to show that such compounds decompose cleanly to [ l HI-2,3-diphenylinden-1-one (3).

Metallacycle Expansion by Alkyne Insertion. Chemistry of a New Family of Ruthenium Organometallics

“…In the particular case of alkyne insertiona reaction first observed in the form of metal-promoted oligomerization 1,2 the net outcome of the primary process and secondary reactions that frequently follow is the formation of new metal−carbon, carbon−carbon, and/or carbon−nonmetal bonds. This makes alkyne insertion a potentially versatile tool for organometallic and organic synthesis. − …”