The synthesis, properties, and crystal structure of n-Bu4N, and the exchange of acetate, chloride, and iodide in n-Bu4N

Article abstract of DOI:10.1016/0022-328X(91)80168-J

Reaction of ⁿBu4N, 1, with silver acetate under CO gave the diacetate salt ⁿBu4N, 2.The complex has been characterised spectroscopically <ν(CO_term) 1986, 2066; ν(CO2-monodentate) 1615 cm^-1> and by a single-crystal X-ray determination.The anion is planar with monodentate acetates, Rh-O 2.074(6) and 2.053(7) Angstroem.Comlex 2 reacted immediately with Mel to give MeOAc and ^-, 3, which then oxidatively added more Mel normally.It also reacted with HCl to give HOAc and ^-.Evidence was obtained for the formation of a labile mixed anion ^- on reaction of with ⁿBu4N⁺OAc^-.It is unlikely that the promotional effect of acetate in methyl acetate carbonylation is due to the participation of acetato-rhodium complexes.Since the lithium acetate reacts readily with iodomethane to give lithium iodide, the observed promotion probably arises from the formation of LiI.MeI reacted with ⁿBu4N, again via preliminary formation of ⁿBu4N, which then added MeI normally.IR spectra showed that the equilibrium, 1 +2I^- <*> 3 + 2Cl^-, favoured the chloride 1 in CH2Cl2, and the iodide 3 in methanol.