Gas-Phase Study of Fe(1+)-Benzyne with Alkanes

Article abstract of DOI:10.1021/ja00189a003

The unimolecular chemistry of Fe(1+)-benzyne and its reactivity with small alkanes in the gas phase are studied by Fourier transform mass spectrometry (FTMS).Collision-induced dissociation of Fe(1+)-benzyne yields benzyne loss exclusively.In contrast, photodissociation of Fe(1+)-benzyne yields not only cleavage of benzyne from Fe(1+), but competitive loss of C2H2 and C2H4 as well.The Fe(1+)-benzyne is formed from chlorobenzene by loss of HCl.This dehydrochlorination of chlorobenzene also occurs in secondary reactions up to six times forming products of the typeFe(1+)-polyphenylene.Fe(1+)-benzyne reacts with alkanes larger than methane to form a wide variety of product ions by mechanisms including hydrogenation and methanation of the benzyne ligand.All of the product ions can be explained by mechanisms based on Fe(1+) insertion into either C-C or C-H bonds as the reaction-initiating step, followed by either alkyl or H migration from Fe(1+) onto the benzyne ligand or, alternatively, by the migratory insertion of benzyne into a metal-carbon or metal-hydrogen bond.Photodissociation and ion-molecule reaction studies yield a value for the metal-ligand bond energy of D⁰(Fe(1+)-benzyne) = 76 +/- 10 kcal/mol.