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Phosphine sulfides and their gold(I) complexes with general formula R3P=S—Au—X (X = Cl−, Br− or CN−) were prepared and characterized by elemental analyses, i.r. and 31P-n.m.r. spectroscopy. A decrease in the i.r. frequency of the P=S bond in the ligands upon complexation, is indicative of 'S' coordination to gold (I). The 31P-n.m.r. spectra revealed that electronegativity of the substituents and angles between them were the two most important factors influencing the 31P-n.m.r. chemical shifts. The phosphorus resonance was observed to be more downfield in alkyl substituted phosphine sulfides as compared to the aryl substituted phosphine sulfides. Ligand scrambling in the Cy3P=S—Au—CN complex in solution, to form [(Cy3P=S)2Au]+ and [Au(CN)2]−, was investigated by 13C and 15N-n.m.r. spectroscopy. Equilibrium constants (K eq) for scrambling of the Cy3P=S—Au—CN complex and for its analogue, Cy3P=Se—Au—CN were measured by integrating the 13C-n.m.r. at 297 K and were found to be 0.147 and 1.81 respectively. |
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