Synthesis, structures and alkane oxygenation reactivity of bioinspired fluoroalkyl iron phthalocyanines

Abstract

We report the synthesis, structural characterization and reactivity of perfluoroalkyl (R[Formula: see text]) substituted perfluoro phthalocyanines, [F[Formula: see text]PcFe(II)L2], L = axial H2O, methanol or pyridine, and [F[Formula: see text]PcFe(III)L], L = methoxy and cyanide anions. X-ray structures of the Fe(II) complexes reveal that axial H2O and methanol are nested in the hydrophobic R[Formula: see text] pocket of the macrocycle. The aqua complexes exhibit columnar stacking with a central linear chain of H-bonded H2O-Fe-H2O groups that form a hydrophilic, linear “core“embedded in surrounding R[Formula: see text] groups. The electron-deficient fluoroalkyl fluoro ([Formula: see text]-C3F[Formula: see text]F8PcFe(II)L2 complexes are all low-spin, diamagnetic, unlike the F[Formula: see text]PcFe complex, L = H2O, which is paramagnetic. The P450-related PcFe(II) complexes, which exhibit no macrocyclic C-H bonds, catalyze cyclohexane (C[Formula: see text] oxygenations using both t-butyl hydroperoxide (TBHP) and air, without noticeable catalyst decomposition, to produce C6-alcohol and C6-ketone in [Formula: see text]1:1 ratio (KA-oil). Relatively high TOFs, 180 and 85/hr, are observed for TBHP and O2-based oxygenations, respectively. No catalyst decomposition is observed for at least 8 hours, even up to 100[Formula: see text]C, when O2 is the oxidant, in the absence of a co-reductant. Fluoroalkylated phthalocyanine iron catalysts lacking C-H bonds could be suitable for other aerobic oxidations and oxygenations.