Qualitatively Different Reactivities of Hydride Reagents toward [(α-diimine)(η5-C5Me5)ClIr]+ Cations: Substitution, Electron Transfer (Reduction), or Stepwise Hydrogenation

Whereas complex cations [(α-diimine)(η 5 -C 5 Me 5 )ClIr] + with 2,2‘-bipyridine and related aromatic ligands show only the expected Cl/H exchange on reaction with borohydrides, the systems [(RN CHCH NR)(η 5 -C 5 Me 5 )ClIr] + undergo reduction to the enediamido(2−)−iridium(III) species [(RNCH CHNR)(η 5 -C 5 Me 5 )Ir], even in protic media, if R is an axially shielding 2,6-dialkylphenyl group. In protic media the complex ion with R = cyclohexyl undergoes Cl/H exchange and stepwise hydrogenation of the α-diimine ligand via [(RHNCH 2 CH NR)(η 5 -C 5 Me 5 )HIr](PF 6 ) to the structurally characterized compound [(RHNCH 2 CH 2 NHR)(η 5 -C 5 Me 5 )HIr][BH 3 (CN)].