Substituent Effects on the Bond-Dissociation Energies of Cationic Arene−Transition-Metal Complexes

Abstract

The bond‐dissociation energies (BDEs) of more than twenty arene−M+ complexes (M = Cr, Fe, Co) have been studied by mass spectrometry, using the kinetic method. With minor exceptions, the same relative order of BDEs is found for the three metals and the series of substituted arenes: electron‐donating substituents, like alkyl or amino groups, increase the arene−metal BDE whereas electron‐withdrawing substituents, e.g. halogens, lower the BDE compared to the unsubstituted benzene complexes. Interestingly, inverse linear correlations of the arene−M+ BDEs and the arenes′ ionization energies (IEs) exist for particular classes of substituents. The present results may serve as a guide to predict BDEs of similar organometallic complexes based on the IEs of substituted arenes and vice versa.

Cation−π Complexes of Silver Studied with Photodissociation and Velocity-Map Imaging

“…This is expected on the basis of previous work on transitionmetal cation−arene complexes. 37 In a systematic study of many cation−arene complexes using the kinetic method, Schwarz and co-workers noted that electron-donating groups such as −CH 3 increased the cation−π bond energies. 37 This was attributed to increased π electron density in the ring system, which facilitates the cation−π interaction.…”

“…37 In a systematic study of many cation−arene complexes using the kinetic method, Schwarz and co-workers noted that electron-donating groups such as −CH 3 increased the cation−π bond energies. 37 This was attributed to increased π electron density in the ring system, which facilitates the cation−π interaction. However, the metals in that study were bound to the arenes in the sixfold symmetric site, whereas the silver ion here binds above the ring edge.…”

“…Metal ion–aromatic complexes are ubiquitous in organometallic chemistry, providing classic examples of cation−π interactions. − These complexes have also been well-studied in mass spectrometry, and their interactions have been investigated extensively with theory. − Because the ionization energies of most metal atoms are lower than those of ligands such as benzene, the charge in such metal–ligand ions resides on the metal in the ground electronic state. This has been demonstrated in several laboratories with collision-induced-dissociation (CID) experiments, which produce the metal cation as the only dissociation product. ,,, With proper analysis, the thresholds for CID processes provide the bond energies for these complexes.…”

Bond dissociation energies in organometallic systems: substituent effects

“…These data are taken from literature. [3][4][5][6][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] We used the BDE values determined by the following methods: calorimetry (C), titration calorimetry (TC), gas-phase ion thermochemistry (GT), kinetic studies in the gas phase (KG), and quantum-chemical calculations (QCC). We used notations C, TC, GT, KG, and QCC in Tables 1-6.…”

Isomeric discrimination and quantification of thyroid hormones, T3 and rT3, by the single ratio kinetic method using electrospray ionization mass spectrometry

“…The thermochemical properties that the method can access include proton affinity [15][16][17], gas-phase basicity [17][18][19][20], ionization energy [21], and metal ion affinity [22][23][24] to name a few. It has also been found useful in the differentiation and determination of enantiomers [25][26][27][28][29] and isomers [29 -34] under sterically-controlled conditions.…”