Mechanochemical and solution synthesis, and crystal structures and IR and solid-state (CPMAS) NMR spectroscopy of some bis(triphenylphosphine)silver(i) mono- and di-hydrogencitrate systems?

Dalton Transactions Pub Date: 2012-03-09 DOI: 10.1039/C2DT12452A

Abstract

The complex [(Ph3P)2Ag(H2cit)]·EtOH (1; H2cit? = dihydrogencitrate = C6H7O7?) contains [(Ph3P)2Ag(H2cit)] molecules in which the silver atom is coordinated to two PPh3 molecules and the two oxygen atoms of one of the ‘terminal’/1-carboxylate groups of the dihydrogencitrate group. The molecules form centrosymmetric hydrogen-bonded dimers in the solid. In [{(Ph3P)2Ag}2(Hcit)], (2), unsymmetrical deprotonation of the citrate grouping is found, from the 1- and 3- (i.e. terminal and central) carboxylates: [(Ph3P)2Ag(O2CCH2C(OH) (CH2COOH)CO2)Ag(PPh3)2]. The above complexes, as well as [(Ph3P)3Ag(H2cit)] (3) were prepared via conventional solution methods, involving the reaction of trisilver(I) citrate, citric acid and triphenylphosphine, and by a mechanochemical method involving the reaction of silver(I) oxide, citric acid and triphenylphosphine. IR studies of 1–3 show the presence of coordinated carboxylate and free carboxylic acid groups in the mono- and di-hydrogencitrate ligands, and the formation of 2 from 1 shows that dihydrogencitrate deprotonation can occur upon dissolution of 1 in protic solvents. High-field (9.40 T) 31P CPMAS NMR spectra were recorded and analysed, yielding heteronuclear 1J(107/109Ag,31P) and homonuclear 2J(31P,31P) spin–spin coupling constants.

Graphical abstract: Mechanochemical and solution synthesis, and crystal structures and IR and solid-state (CPMAS) NMR spectroscopy of some bis(triphenylphosphine)silver(i) mono- and di-hydrogencitrate systems
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