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Substituent effects in the decarboxylation reactions of coordinated arylcarboxylates in dinuclear copper complexes, [(napy)Cu2(O2CC6H4X)]+

Citation

Jin, Q and Li, J and Ariafard, A and Canty, AJ and O'Hair, RAJ, Substituent effects in the decarboxylation reactions of coordinated arylcarboxylates in dinuclear copper complexes, [(napy)Cu2(O2CC6H4X)]+, European Journal of Mass Spectrometry, 23, (6) pp. 351-358. ISSN 1469-0667 (2017) [Refereed Article]

Copyright Statement

Copyright 2017 the Authors

DOI: doi:10.1177/1469066717729067

Abstract

A combination of gas-phase ion trap mass spectrometry experiments and density functional theory (DFT) calculations have been used to examine the role of substituents on the decarboxylation of 25 different coordinated aromatic carboxylates in binuclear complexes, [(napy)Cu2(O2CC6H4X)]+, where napy is the ligand 1,8-naphthyridine (molecular formula, C8H6N2) and X = H and the ortho (o), meta (m) and para (p) isomers of F, Br, CN, NO2, CF3, OAc, Me and MeO. Two competing unimolecular reaction pathways were found: decarboxylation to give the organometallic cation [(napy)Cu2(C6H4X)]+ or loss of the neutral copper benzoate to yield [(napy)Cu]+. The substituents on the aryl group influence the branching ratios of these product channels, but decarboxylation is always the dominant pathway. Density functional theory calculations reveal that decarboxylation proceeds via two transition states. The first enables a change in the coordination mode of the coordinated benzoate in [(napy)Cu2(O2CC6H4X)]+ from the thermodynamically favoured O,O-bridged form to the O-bound form, which is the reactive conformation for the second transition state which involves extrusion of CO2 with concomitant formation of the CO2 coordinated organometallic cation, [(napy)Cu2(C6H4X)(CO2)]+, which then loses CO2 in the final step to yield [(napy)Cu2(C6H4X)]+. In all cases the barrier is highest for the second transition state. The o-substituted benzoates show a lower activation energy than the m-substituted ones, while the p-substituted ones have the highest energy, which is consistent with the experimentally determined normalised collision energy required to induce fragmentation of [(napy)Cu2(O2CC6H4X)]+.

Item Details

Item Type:Refereed Article
Keywords:copper benzoates, decarboxylation, organocopper, gas-phase, mass spectrometry, density functional theory calculations
Research Division:Chemical Sciences
Research Group:Other Chemical Sciences
Research Field:Organometallic Chemistry
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Chemical Sciences
Author:Canty, AJ (Professor Allan Canty)
ID Code:123428
Year Published:2017
Web of Science® Times Cited:1
Deposited By:Chemistry
Deposited On:2018-01-08
Last Modified:2018-03-27
Downloads:0

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