An Oxoiron(IV) Complex Supported by an N‐Alkylated Cyclam Ligand System Containing a Pendant Alcohol Moiety

Abstract

The effect of a pendant neutral alcohol moiety in the N‐alkylated cyclam (1,4,8,11‐tetraazacyclotetradecane) ligand backbone is examined for the non‐heme mononuclear oxoiron(IV) unit in [FeIV(Osyn)(TMC‐HOR)(NCCH3)]2+ (1‐syn) (TMC‐HOR=2‐(4,8,11‐trimethyl‐1,4,8,11‐tetraazacyclotetradecan1‐yl)ethan‐1‐ol). Unlike in the related [FeIV(Oanti)(TMC‐SR)]+ (3‐anti) (TMC‐SR=1‐mercaptoethyl‐4,8,11‐trimethyl‐1,4,8,11‐tetraazacyclotetradecane) complex, bearing an axial mono‐anionic thiolate ligand trans to the oxo unit, the alcohol moiety in 1‐syn stays protonated and does not axially coordinate to iron. The protonation of the alcohol moiety is a prerequisite for the stabilization of the oxoiron(IV) core; it presumably serves as a hydrogen bonding donor to the oxoiron(IV) unit, which is positioned syn to the three methyl groups. Comparative reactivity studies reveal 1‐syn to be a stronger hydrogen atom abstraction but weaker oxygen atom transfer agent relative to the [FeIV(Osyn)(TMC)(NCCH3)]2+ (2‐syn) complex, bearing the N‐tetramethylated cyclam (TMC) ligand.