Interaction of hydrated protons with octyl-phenyl-N,N-diisobutylcarbamoylmethyl phosphine oxide (CMPO): NMR and theoretical study

✍ Scribed by Jaroslav Kříž; Jiří Dybal; Emanuel Makrlík; Petr Vaňura

• Publisher: John Wiley and Sons
• Year: 2011
• Tongue: English
• Weight: 302 KB
• Volume: 49
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.2774

✦ Synopsis

Abstract

Interaction of octyl‐phenyl‐N,N‐diisobutylcarbamoylmethylphosphine oxide (CMPO, the ‘classical’ rare metal extraction agent) with fully ionized hydrated protons (HP) was studied in acetonitrile‐d~3~ using ^1^H, ^13^C, ^31^P NMR, PFG NMR and magnetic relaxation. The experimental results were confronted with high‐precision ab initio DFT calculations. Relative chemical shifts of NMR signals of CMPO (0.01 mol/L) under the presence of HP in the molar ratio β = 0–2.0 mol/mol show binding between CMPO and HP. Self‐diffusion measurements using ^1^H PFG NMR demonstrate that larger complexes with higher content of CMPO are generally formed at β < 0.75. Analyzing the collective dependence of ^13^C and ^31^P NMR chemical shifts on β by the use of program LETAGROP, we obtained very good fitting for the assumed coexistence of two complexes (CMPO)~2~·HP (C~2~) and CMPO.HP (C~1~). The logarithms of the respective stabilization constants log K~i~ were found to be 7.518 (C~2~) and 4.581 (C~1~). The system dynamics was studied by measuring the transverse ^1^H NMR relaxation using CPMG sequence with varying delays t~p~ between the π pulses in the mixtures with β = 0.4–0.8. The following exchange correlation times were obtained: τ~10~ = 2.35 × 10^−5^, τ~20~ = 0.82 × 10^−4^, τ~21~ = 0.45 × 10^−3^s. The DFT calculations support the conclusion that the complexes C~1~ and C~2~ are the main species in the mixtures of CMPO with HP. They also agree with the NMR and FTIR observation that the main site to which H~3~O^+^ is bound is the PO group, whereas the amide group does not form a strong bond with the ion when excess water molecules are present. Copyright © 2011 John Wiley & Sons, Ltd.