Iridium complexes kinetic stability

Rhodium and iridium are unreactive metals. They react with O2 or the halogens only at high temperatures (see below) and neither is attacked by aqua regia. The metals dissolve in fused alkalis. For Rh and Ir, the range of oxidation states (Table 20.3) and the stabilities of the highest ones are less than for Ru and Os. The most important states are Rh(III) and Ir(III), i.e. which is invariably low-spin, giving diamagnetic and kinetically inert complexes (see Section 26.2). 

Interest in iridium hydrocarbyl complexes has been fueled by the higher thermodynamic stability of both Ir-C and Ir-H bonds in comparison to related compounds of rhodium. Therefore, iridium alkyl and aryl complexes have been frequently and successfully used as kinetically inert models for a variety of rhodium-catalyzed reactions allowing to collect intriguing mechanistic information on important industrial processes and organometallic reactions of academic interest. 

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