Binuclear ‘oxidative isomerization’ as a model for surface reactions. Intramolecular character and kinetic profile of iodomethyldi-iridium(II): µ-methylenedi-iridium(III) conversion that follows di-iodomethane addition to [Ir(CO)(PPh3)(µ-pz)]2(Hpz = pyrazole)

Abstract

Isomerization of the di-iridium(II) complex [Ir₂(CO)₂(PPh₃)₂(µ-pz)₂(CH₂I)(I)](2, Hpz = pyrazole) to the di-iridium(III) methylene complex [Ir₂(CO)₂(PPh₃)₂(µ-pz)₂(µ-CH₂)(I)₂](7) which occurs on reflux in benzene solution has been found to be intramolecular by mass spectrometric analysis of isotope distribution (¹³C and ²H) in isotopomers of (7) formed from (2) containing ¹³CO or C²H₂I groups or both, and the (2)–(7) conversion shows first-order behaviour which is conspicuously retarded by added PPh₃; an X-ray crystal structure determination for compound (7) confirms that the two Ir centres lie outside bonding range at 3.432(1)Å with tetrahedral µ-CH₂.