The compounds [K(18-crown-6)]3[Ir(Se4)3] (1), [K(2.2.2-cryptand)]3[Ir(Se4)3]·C 6H5CH3 (2), and [K(18-crown-6)(DMF)2][Ir(NCCH3)2(Se 4)2] (3) (DMF = dimethylformamide) have been prepared from the reaction of [Ir(NCCH3)2(COE)2][BF4] (COE = cyclooctene) with polyselenide anions in acetonitrile/DMF. Analogous reactions utilizing [Rh(NCCH3)2(COE)2][BF4] as a Rh source produce homologues of the Ir complexes; these have been characterized by 77Se NMR spectroscopy. [NH4]3[Ir(S6)3·H 2O·0.5CH3CH2OH (4) has been synthesized from the reaction of IrCl3·nH2O with aqueous (NH4)2Sm. In the structure of [K(18-crown-6)]3[Ir(Se4)3] (1) the Ir(III) center is chelated by three Se42- ligands to form a distorted octahedral anion. The structure contains a disordered racemate of the Δλλλ and Δδδδ conformers. The K+ cations are pulled out of the planes of the crowns and interact with Se atoms of the [Ir(Se4)3]3- anion. [K(2.2.2-cryptand)]3[Ir(Se4)3]·C 6H5CH3 (2) possesses no short K⋯Se interactions; here the [Ir(Se4)3]3- anion crystallizes as the Δλλδ/Δδδλ racemate. In the crystal structure of [K(18-crown-6)(DMF)2][Ir(NCCH3)2(Se 4)2] (3), the K+ cation is coordinated by an 18-crown-6 ligand and two DMF molecules and the anion comprises an octahedral Ir(III) center bound by two chelating Se42- chains and two trans acetonitrile groups. The [Ir(Se4)3]3- and [Rh(Se4)3]3- anions undergo conformational transformations as a function of temperature, as observed by 77Se NMR spectroscopy. The thermodynamics of these transformations are: [Ir(Se4)3]3-, ΔH = 2.5(5) kcal mol-1, ΔS = 11.5(2.2) eu; [Rh(Se4)3]3-, ΔH = 5.2(7) kcal mol-1, ΔS = 24.7(3.0) eu.
|Original language||English (US)|
|Number of pages||6|
|State||Published - 1996|
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry