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Investigating Bidentate and Tridentate Carbamoylmethylphosphine Oxide Ligand Interactions with Rare-Earth Elements Using Electrospray Ionization Quadrupole Ion Trap Mass Spectrometry

Authors :
Matthew C. Crowe
Jennifer S. Brodbelt
László Párkányi
Keith H. Pannell
Louis D. Schulte
Ramesh N. Kapoor
Francisco Cervantes-Lee
Source :
Inorganic Chemistry. 44:6415-6424
Publication Year :
2005
Publisher :
American Chemical Society (ACS), 2005.

Abstract

Electrospray ionization (ESI) quadrupole ion trap mass spectrometry (QIT-MS) and collisionally activated dissociation (CAD) were used to evaluate the rare-earth binding properties of two hydrophobic carbamoylmethylphosphine oxide (CMPO) ligands, the normal bidentate variety, (t-BuC6H4)2P(O)CH2C(O)N(i-Bu)2 (A), a new potentially tridentate extractant, (t-BuC6H4)2P(O)CH[CH2C(O)N(i-Bu)2]C(O)N(i-Bu)2 (B), and tributyl phosphate. The mass spectral results obtained from analysis of 1% HNO3/methanol solution containing the ligands and dissolved lanthanide salts reveal that the favorable stoichiometries of the ligand/metal/nitrate complexes are 2:1:2 for the bidentate ligand A, 1:1:2 for the tridentate ligand B, and 3:1:2 for the monodentate tributyl phosphate. These observed stoichiometries correlate with the number of available binding sites on each ligand as well as with potential steric effects. Energy-variable collisionally activated dissociation experiments showed that for the 2:1:2 complexes involving ligand A or B, as the ionic radius of the bound metal decreased, the removal of nitric acid required less energy and resulted in less extensive spontaneous solvent coordination. This experimental trend suggests that, as the ionic radius of the lanthanide ion decreases, a pair of the carbamoylmethylphosphine ligands is able to more completely solvate the bound metal ion thereby weakening the nitrate-metal interaction.

Details

ISSN :
1520510X and 00201669
Volume :
44
Database :
OpenAIRE
Journal :
Inorganic Chemistry
Accession number :
edsair.doi.dedup.....64251426e5b4075dbf82185cf8958787