CATALYTIC INTERMEDIATES IN CARBONYLATION REACTIONS .3. ISOLATION, SPECTROSCOPY, ELECTROCHEMICAL CHARACTERISTICS AND CRYSTAL-STRUCTURE OF ISOQUINOLINIUM DICARBONYL TETRAIODO IRIDIUM(III)

The iodocarbonyl anion of iridium(III), [Ir(CO)(2)I-4](-), was Isolate d and characterized as the isoquinolinium salt during carbonylation of ethanol and higher alcohols using IrCl3 . 3H(2)O as a catalyst precur sor with HI as a promoter. X-ray analysis shows the presence of discre te cationic [C11H12N](+) and cis anionic species [Ir(CO)(2)I-4](-), wi th a distorted octahedral environment around iridium and average Ir-I and Ir-C distances of 2.702(2) and 1.86(4) Angstrom, respectively. Spe ctral and electrochemical studies on the intermediates isolated during carbonylation of other higher alcohols revealed a strong influence of the counter cation on the electron-transfer processes in these haloca rbonyl complex of Ir-III.