User-friendly aerobic reductive alkylation of iridium(iii) porphyrin chloride with potassium hydroxide: scope and mechanism

Abstract

Alkylation of iridium 5,10,15,20-tetrakistolylporphyrinato carbonyl chloride, Ir(ttp)Cl(CO) (1), with 1°, 2° alkyl halides was achieved to give (ttp)Ir-alkyls in good yields under air and water compatible conditions by utilizing KOH as the cheap reducing agent. The reaction rate followed the order: RCl < RBr < RI (R = alkyl), and suggests an S_N2 pathway by [Ir^I(ttp)]⁻. Ir(ttp)-adamantyl was obtained under N₂ when 1-bromoadamantane was utilized, which could only undergo bromine atom transfer pathway. Mechanistic investigations reveal a substrate dependent pathway of S_N2 or halogen atom transfer.