The stereochemistry and reactivity of [Ir(E2R)(dppe)2]2+ (dppe = Ph2P(CH2)2PPh2; E = S, Se; R = H, CH3) have been examined. In solution, [Ir(E2CH3)(dppe)2]2+ exists as a mixture of two diastereomers in the ratio of 20:1 (E = S) and 6:1 (E = Se). Protonation of [Ir(E2)(dppe)2]+ with strong acids gave [Ir(E2H)(dppe)2]2+ complexes, which are spectroscopically and stereochemically similar to the η2-E2CH3 derivatives. In contrast to [Ir(S2)(dppe)2]+, the [Ir(S2CH3)(dppe)2]2+ (1) complex can act as both a potent sulfur atom and CH3S+ transfer reagent. The nature of the S-transfer reaction depends on the substrate (X) used and the stability of the corresponding S-X and [X-SCH3]+ products. 1 reacts rapidly with PPh3 (2 equiv) to give [Ir(dppe)2]+, Ph3PS, and [Ph3PSCH3]+. With CH3NC (2 equiv) and 1, sulfur atom transfer occurs, and cis-[Ir(SCH3)(CH3NC)(dppe)2]2+ and CH3NCS are produced. Reaction of CN- with 1 gave cis-[Ir(SCH3)(SCN)(dppe)2]+. Oxidative addition of CH3SH and CH3SCl to [Ir(dppe)2]+ gave [Ir(SCH3)H(dppe)2]+ and [Ir(SCH3)Cl(dppe)2]+, respectively. 1H NMR species confirmed the utility of the high-field ortho phenyl, the S2CH3, and the SCH3 resonances in structure elucidation. Also described is the applicability of gel-permeation chromatography and field-desorption mass spectrometry for the purification and characterization of these ionic, high molecular weight complexes.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry