The Magnesium Dication and Water Synergistically Promote the Protonolysis of Two of the B-C Bonds in the Tetraphenylborate Anion

Asma M O Aldajani; Howard Z Ma; Yang Yang; Allan J Canty; Richard A J O'Hair

doi:10.1021/jasms.4c00017

The Magnesium Dication and Water Synergistically Promote the Protonolysis of Two of the B-C Bonds in the Tetraphenylborate Anion

J Am Soc Mass Spectrom. 2024 Mar 6;35(3):636-641. doi: 10.1021/jasms.4c00017. Epub 2024 Feb 26.

Authors

Asma M O Aldajani^{1

2

3}, Howard Z Ma^{2

3}, Yang Yang^{2

3}, Allan J Canty⁴, Richard A J O'Hair^{2

3}

Affiliations

¹ Department of Chemistry, College of Science, University of Bisha, P.O. Box 551, Bisha 61922, Saudi Arabia.
² School of Chemistry, The University of Melbourne, Parkville, Victoria 3010, Australia.
³ Bio21 Institute of Molecular Science and Biotechnology, The University of Melbourne, Parkville, Victoria 3010, Australia.
⁴ School of Physical Sciences - Chemistry, University of Tasmania, Private Bag 75, Hobart, Tasmania 7001, Australia.

PMID: 38408905
DOI: 10.1021/jasms.4c00017

Abstract

Analytes are sampled from both solution phase and gas-phase environments during the ESI process, and thus, the mass spectrum that is measured can reflect both solution and gas-phase conditions. In the gas-phase regime, ion-molecule reactions can influence the types of ions that are observed. Herein, the synergistic effects of a Lewis acid (Mg²⁺) and background water are shown to lead to protonolysis of two of the B-C bonds of the tetraphenylborate ion in the gas phase, giving rise to different ions at different reaction times in ESI-MS/MS experiments in a linear ion trap mass spectrometer. At short reaction times (1 ms), the expected adduct [Mg(BPh₄)]⁺ is observed. At 10 ms, [(HO)Mg(BPh₃)]⁺ and [(HO)₂Mg(BPh₂)]⁺ are observed. At 100 ms, the water adducts [(HO)₂Mg(BPh₂)(H₂O)]⁺ and [(HO)₂Mg(BPh₂)(H₂O)₂]⁺ appear, and these become the dominant ions at longer reaction times. DFT calculations provide a plausible explanation as to why only [(HO)Mg(BPh₃)]⁺ and [(HO)₂Mg(BPh₂)]⁺ but not [(HO)₃Mg(BPh)]⁺ are observed.