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Routes for the gas-phase total synthesis of dihydroxy magnesium carboxylate anions, [(RCO2)Mg(OH)2](R = CH3 and CH3(CH2)14)

Citation

Langeland, J and Khairallah, GN and Canty, AJ and O'Hair, RAJ, Routes for the gas-phase total synthesis of dihydroxy magnesium carboxylate anions, [(RCO2)Mg(OH)2]-(R = CH3 and CH3(CH2)14), International Journal of Mass Spectrometry, 436 pp. 91-100. ISSN 1387-3806 (2019) [Refereed Article]

Copyright Statement

Copyright 2018 Elsevier B.V.

DOI: doi:10.1016/j.ijms.2018.11.004

Abstract

Dihydroxy magnesium carboxylates, [(RCO2)Mg(OH)2], a previously unknown class of compounds, have recently been discovered in meteorites using electrospray ionisation (ESI) ultra high-resolution mass spectrometry (HRMS) and collision-induced dissociation (CID) experiments (A. Ruf et al., Proc. Natl. Acad. Sci. U.S.A. 114 (2017) 2819). Here we present two general strategies for the gas-phase synthesis of [(RCO2)Mg(OH)2] (where R = CH3 and CH3(CH2)14) in a linear quadrupole ion trap mass spectrometer using combinations of CID and ion-molecule reactions (IMR) with water. Both involve the same first step (Step 1), where [(RCO2)Mg(O2CCH3)2] precursor ions generated via ESI are mass selected and subjected to decarboxylation. In Route I the resultant organomagnesate [(RCO2)Mg(CH3)(O2CCH3)] is subjected to the following reactions: Step 2a involves decarboxylation via CID to give [(RCO2)Mg(CH3)2] which undergoes an IMR in Step 3a to give [(RCO2)Mg(CH3)(OH)]. For Route II [(RCO2)Mg(CH3)(O2CCH3)] undergoes an IMR to give in Step 2b, [(RCO2)Mg(OH)(O2CCH3)], which in Step 3b fragments under CID to give [(RCO2)Mg(CH3)(OH)]. Both routes converge in the final Step 4, where the organometallic ion [(RCO2)Mg(CH3)(OH)] reacts with water to give the desired dihydroxy magnesium carboxylate, [(RCO2)Mg(OH)2]. All ion molecule reactions proceed rapidly and cleanly to produce the hydroxides. In contrast, the decarboxylation reactions are in competition with other pathways including loss of the carboxylate anion and loss of a neutral ligand to give a magnesium coordinated enolate of acetate. DFT calculations were used to examine the structures and energies of species involved in the competing reactions associated with each of the steps.

Item Details

Item Type:Refereed Article
Keywords:meteorites, magnesium complexes, mass spectrometry, DFT
Research Division:Chemical Sciences
Research Group:Macromolecular and Materials Chemistry
Research Field:Synthesis of Materials
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Chemical Sciences
UTAS Author:Canty, AJ (Professor Allan Canty)
ID Code:130004
Year Published:2019
Deposited By:Chemistry
Deposited On:2019-01-04
Last Modified:2019-12-09
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