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Ligand Effects on the Gas‐Phase Reactions of (π‐L)Fe I Complexes with n ‐Pentanenitrile
Author(s) -
Stöckigt Detlef,
Sen Semiha,
Schwarz Helmut
Publication year - 1993
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19931261134
Subject(s) - chemistry , dehydrogenation , ligand (biochemistry) , isomerization , nitrile , medicinal chemistry , alkyl , metal , molecule , crystallography , stereochemistry , catalysis , organic chemistry , biochemistry , receptor
The gas‐phase ion chemistry of the previously studied system Fe( n ‐pentanenitrile) + is dramatically changed, when the metal ion bears substituents L (L = C 2 H 4 , C 3 H 6 , C 4 H 6 , i ‐C 4 H 8 , 1‐C 4 H 8 , 2‐C 4 H 8 , and C 6 H 6 ), and the major ion‐molecule reactions of Fe(L) + with RCN (R = n ‐C 4 H 9 ) are as follows: (i) Ligand substitution Fe(L) + + RCN → Fe(RCN) + + L is observed for all L studied except L = C 4 H 6 , C 6 H 6 ; (ii) the formation of association complexes Fe(L)(RCN) + takes place for all ligands L, except L = C 2 H 4 ; (iii) dehydrogenation of the L is confined to L = 1‐C 4 H 8 and 2‐C 4 H 8 ; (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‐C 4 H 8 and 2‐C 4 H 8 , 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.