SYNTHESIS, MOLECULAR-STRUCTURE, AND VIBRATIONAL-SPECTRA OF MER-TRIS(CARBONYL)IRIDIUM(III)FLUOROSULFATE, MER-IR(CO)(3)(SO3F)(3)

Addition of carbon monoxide (0.5-2 atm) to iridium(III) fluorosulfate, Ir(SO3F)(3), dissolved in HSO3F over 4 days and at 60 degrees C, resu lts in the quantitative formation of tris(carbonyl)iridium(III) fluoro sulfate Ir(CO)(3)(SO3F)(3) Slow evaporation of the solvent produces si ngle crystals of mer-Ir(CO)(3)(SO3F)(3). Crystal structure data for me r-Ir(CO)(3)(SO3F)(3): monoclinic, space group P2(1)/c, Z = 4, a = 8.47 6(1) Angstrom, b = 12.868(2) Angstrom, c = 12.588 (1) Angstrom, beta = 108.24(1)degrees, V = 1304.0 Angstrom(3), T = 200 K, R(F) = 0.022 for 2090 data (I-0 greater than or equal to 2.5 sigma(I-0)) and 200 varia bles. Vibrational spectra of the crystalline solid are consistent with a mer-isomer with CO stretching modes at 2249 (A(1)), 2208 (B-1), and 2198 (A(1)) cm(-1) in the IR spectrum. In solution of HSO3F, addition al CO stretching bands attributed to the fac-isomer are found in the F T-Raman and IR spectra at 2233 (A(1)) and 2157 cm(-1) (E). Additional evidence for a mixture of fac- and mer-isomers comes from F-19 NMR spe ctra. The vibrational spectra suggest strongly reduced iridium to CO p i-back-bonding. The crystal structure reveals significant intra- and i ntermolecular contacts between the electropositive C atom of the CO gr oups and O or F atoms of the fluorosulfate groups. Hence mer-tris(carb onyl)iridium(III) fluorosulfate becomes the first thermally stable, st ructurally characterized, and predominantly sigma-bonded carbonyl deri vative of a metal in the +3 oxidation state.