Dissolve 5.6 g triphenylphosphine in about 30 mL acetonitrile with gentle warming on a steam bath. Suspend 0.5 g copper (I) oxide in 10 mL acetonitrile in a wide test tube and add concentrated sulfuric acid drop wise with constant swirling until the red color has discharged and most of the solid has dissolved. You should need no more than about 0.5 cm3 for this. Add the copper solution to the triphenylphosphine solution and filter the mixture by gravity. Evaporate the filtrate to about 20 mL on a steam bath in the fume hood and allow cooling to room temperature. Precipitate the product by adding diethyl ether slowly with constant stirring, about 50 mL should suffice. Filter the product, dry at the pump and record the weight obtained. Record the infrared spectrum of the compound as before. Carry out fragment analysis using the S-O bonds as the basis set to deduce the number of S-O stretches expected in the infrared and Raman spectra of sulfate ion in the three coordination modes illustrated above. Required:
Compare these predictions with the infrared spectra of the complexes and hence deduce the coordination mode of the sulfate ion.