Stability of iodoalkyl di-iridium(II) complexes. Bridge-formation by iodomethyl: µ-methylene ring-closure at a bimetal centre

Abstract

Reaction of [Ir(CO)₂(µ-pz)]₂(2)(pzH = pyrazole) with CH₂I₂ affords a mixture (70 : 20 : 10 ratio) of [Ir₂(CO)₄(µ-pz)₂I(CH₂I)](3a), [Ir₂(CO)₄(µ-pz)₂(µ-CH₂)I₂](3b) and [Ir(CO)₂(µ-pz)I]₂(4), which on heating in benzene is converted into a mixture (70 : 30) of compounds (3b) and (4) from which pure (3b) may be recovered; by contrast treatment of the precursor (2) with 1,2-C₂H₄I₂ yields only complex (4) while with 1,3-C₃H₆I₂ the stable iodopropyl complex [Ir₂(CO)₄(µ-pz)₂I(CH₂CH₂CH₂I)](5) is obtained.