The system IrX(CO)(P(C6H5)3)2 in benzene solution adds molecular oxygen reversibly when X is Cl and irreversibly when X is I. The crystal and molecular structure of IrIO2(CO)(P(C6H5)3)2 · CH2C12 has been determined from three-dimensional Xray data collected by counter methods. The structure has been refined by least-squares techniques to a final R factor on F of 5.9% for 1255 reflections above background. The material crystallizes in space group C2h5-P2t/n of the monoclinic system, with four molecules in a cell of dimensions a = 10.69, b = 22.86, c = 15.00 A, β = 93.05°. The observed density is 1.80 g/cm3, the same as that calculated for the above cell. The crystal structure consists of the packing of the discrete monomeric units IrIO2(CO)(P(C6H5)3)2 and CH2Cl2. The molecular structure of IrIO2(CO)(P(C5H5)3)2 closely resembles that reported earlier for IrClO2(CO)(P(C6H5)3)2; the iridium atom, the two oxygen atoms, the carbonyl group, and the iodine atom are situated in the equatorial plane of a trigonal bipyramid, with phosphorus atoms above and below this plane. The two oxygen atoms are equidistant from the iridium atom, with an average Ir-0 distance of 2.06 A. The 0-0 distance is 1.509 ± 0.026 A in this irreversibly oxygenated iodo compound, whereas it is 1.30 ± 0.03 A in the reversibly oxygenated cliloro compound. This very significant change in the 0-0 bond length is consistent with the Π-bonding scheme that Griffith applied to the bonding of molecular oxygen to the heme group in oxyhemoglobin.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry