Structural characterization of silver dialkylphosphite salts using solid-state 109Ag and 31P NMR spectroscopy, IR spectroscopy and DFT calculations.
High-resolution solid-state (109)Ag and (31)P NMR spectroscopy was used to investigate a series of silver dialkylphosphite salts, Ag(O)P(OR)(2) (R = CH(3), C(2)H(5), C(4)H(9) and C(8)H(17)), and determine whether they adopt keto, enol or dimer structures in the solid state. The silver chemical shift, CS, tensors and |J((109)Ag, (31)P)| values for these salts were determined using (109)Ag (Xi = 4.652%) NMR spectroscopy. The magnitudes of J((109)Ag, (31)P) range from 1250 +/- 10 to 1318 +/- 10 Hz and are the largest reported so far. These values indicate that phosphorus is directly bonded to silver for all these salts and thus exclude the enol structure. All (31)P NMR spectra exhibit splittings due to indirect spin-spin coupling to (107)Ag (I = 1/2, NA = 51.8%) and (109)Ag (I = 1/2, NA = 48.2%). The (1)J((109)Ag, (31)P) values measured by both (109)Ag and (31)P NMR spectroscopy agree within experimental error. Analysis of (31)P NMR spectra of stationary samples for these salts allowed the determination of the phosphorus CS tensors. The absence of characteristic P=O stretching absorption bands near 1250 cm(-1) in the IR spectra for these salts exclude the simple keto tautomer. Thus, the combination of solid-state NMR and IR results indicate that these silver dialkylphosphite salts probably have a dimer structure. Values of silver and phosphorus CS tensors as well as (1)J((109)Ag, (31)P) values for a dimer model calculated using the density functional theory (DFT) method are in agreement with the experimental observations.
Chen
Fu
F
Department of Chemistry, Gunning/Lemieux Chemistry Centre, University of Alberta, Edmonton, Alberta, Canada T6G 2G2.
Wasylishen
Roderick E
RE