Ligand Effects on the Gas-Phase Reactions of (π-L)FeI Complexes with n-Pentanenitrile

The gas‐phase ion chemistry of the previously studied system Fe(n‐pentanenitrile)+ is dramatically changed, when the metal ion bears substituents L (L = C2H4, C3H6, C4H6, i‐C4H8, 1‐C4H8, 2‐C4H8, and C6H6), and the major ion‐molecule reactions of Fe(L)+ with RCN (R = n‐C4H9) are as follows: (i) Ligand substitution Fe(L)+ + RCN → Fe(RCN)+ + L is observed for all L studied except L = C4H6, C6H6; (ii) the formation of association complexes Fe(L)(RCN)+ takes place for all ligands L, except L = C2H4; (iii) dehydrogenation of the L is confined to L = 1‐C4H8 and 2‐C4H8; (iv) carbon–carbon and carbon–nitrogen bond activation of the nitrile, typical for the behaviour of bare Fe+, are absent in the reactions of all Fe(L)+ with RCN, Dehydrogenation of the nitrile is observed only for L = 1‐C4H8 and 2‐C4H8, and the molecular hydrogen originates exclusively from the γ/δ‐position of the alkyl chain following the well‐established “remote functionalization” concept. In contrast to the reaction of bare Fe+ with n‐pentanenitrile, dehydrogenation in the Fe(L)(RCN)+ system is not preceded by a degenerate isomerization of RCN, bringing about equilibrations of the C(α)/C(γ) positions. Rate constants were derived and compared with those calculated by the ADO and CAP theories. All reactions of the ligated Fe(L)+ ions were found to occur with collision rate, again in contrast to the bare Fe+. Based on the ADO formalism, the dipole locking constant “c” of n‐pentanenitrile was redetermined to c = 0.47.