Regioselective Formation of β‐Alkyl‐α‐phenyliridabenzenes via Unsymmetrical 3‐Vinylcyclopropenes: Probing Steric and Electronic Influences by Varying the Alkyl Ring Substituent

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Abstract
The synthesis of unsymmetrical (Z)‐1‐alkyl‐3‐(2‐iodovinyl)‐2‐phenyl‐1‐cyclopropenes (R=Me (8 a), Et (8 b), iPr (8 c), and tBu (8 d)) and their reactions with Vaska's complex [Ir(CO)Cl(PPh3)2] and its trimethylphosphine analogue [Ir(CO)Cl(PMe3)2] were investigated. Iridabenzvalene (13/20), iridabenzene (14/21), and/or η5‐cyclopentadienyliridium complexes (15/22) were obtained in modest yields and were fully characterized by spectroscopic means. X‐ray structural data was secured for iridabenzvalene 13 d and iridabenzenes 14 a,b,d. Whereas iridabenzenes 14 a–c were stable at 75 °C for 48 h, 14 d, which possesses a bulky tBu group, rearranged cleanly to cyclopentadienyliridium 15 d at 50 °C over 15 h and displayed first‐order kinetics. The influence of the alkyl substituent on the mechanisms of iridacycle generation, isomerization, and iridabenzene regioselectivity is discussed.