Is the Fe+‐Induced C — H/C — C Bond Activation of α,ω‐Alkanedinitriles Affected by Bifunctional Interactions?

Abstract

AbstractThe metastable‐ion mass spectra of Fe+ complexes of alkanedinitriles NC(CH2)nCN (n = 1 – 10) exhibit six types of reactions: (1) Loss of the intact ligand to regenerate bare Fe+ as the exclusive (n = 1) or major reaction (n = 2) for the lower homologues; (2) generation of nitriles H(CH2)mCN with m = 0 – 6; (3) formation of unsaturated nitriles CH2 = CH(CH2)mCN with m = 0 – 4; (4) production of C2H4; (5) dehydrogenation, and (6) expulsion of the radicals C2H5 and CH2CN+. The branching ratios of these competing processes are governed by the chain length (CH2)n separating the two CN groups. Mechanistic insight is provided by the study of isotopomers. A comparison of the present data with the previously described behaviour of RCN/Fe+ complexes (R = alkyl) leaves no doubt that for the α,ω‐alkanedinitriles it is the Fe+‐mediated interaction of the two functional groups which controls the gas‐phase chemistry of these organometallic systems. For example, results are presented demonstrating inter alia that losses of H2 and C2H4 proceed by completely different pathways when dinitriles serve as precursors, and either reaction is affected by neighbouring group participation. In distinct contrast, for RCN/Fe+ complexes (R = alkyl) the existing data point to common intermediates.