Structural characterization of silver dialkylphosphite salts using solid-state 109Ag and 31P NMR spectroscopy, IR spectroscopy and DFT calculations

High-resolution solid-state Ag-109 and P-31 NMR spectroscopy was used to investigate a series of silver dialkylphosphite salts, Ag(O)P(OR)(2) (R = CH3, C2H5, C4H9 and C8H17), and determine whether they adopt keto, enol or dimer structures in the solid state. The silver chemical shift, CS, tensors and vertical bar J(Ag-109, P-31)vertical bar values for these salts were determined using Ag-109 (Xi = 4.652%) NMR spectroscopy. The magnitudes of J(Ag-109, P-31) 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 P-31 NMR spectra exhibit splittings due to indirect spin-spin coupling to Ag-107 (I = 1/2, NA = 51.8%) and Ag-109 (I = 1/2, NA = 48.2%). The (1)J(Ag-109, P-31) values measured by both Ag-109 and P-31 NMR spectroscopy agree within experimental error. Analysis of P-31 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(Ag-109, P-31) values for a dimer model calculated using the density functional theory (DFT) method are in agreement with the experimental observations. Copyright (C) 2010 John Wiley & Sons, Ltd.