First Evidence for Ozonido‐TMC Complexes of Iron and Cobalt

Abstract

ABSTRACT We present compelling evidence for the first Fe‐ and Co‐ozonido complexes: [(D 12 ‐TMC)Fe III (O 3 )(OTf)](B Ar F), [(D 12 ‐TMC)Fe III (O 3 )(I)](B Ar F), and {[(D 12 ‐TMC)Co III (F)] 2 (O 3 )}(B Ar F) 2 from the reactions of complexes [(D 12 ‐TMC)Fe II ( X )]B Ar F and [(D 12 ‐TMC)Co II ( X )]B Ar F ( X   =  OTf, F, I) with ozone in 2‐Me‐THF/THF solutions using ultraviolet–visible spectroscopic and cryospray mass spectrometric techniques at cryogenic temperatures as low as −155°C (118 K). Further reactivity studies suggest the subsequent formation of Fe‐ and Co‐oxido complexes [(D 12 ‐TMC)Fe IV (O)(OTf)]B Ar F, [(D 12 ‐TMC)Co IV (O)(OTf)]B Ar F, and [(D 12 ‐TMC)Co IV (O)(F)]B Ar F. Density functional theory computations with the ω B97X‐3c three‐component method and the ω B97X‐D4 hybrid functional corroborate our spectroscopic results. Further key results of our studies entail the synthesis of several hitherto unreported Fe and Co complexes, including complexes with strongly (F) and moderately stabilizing (OTf) anions without extraneous coordinated solvent molecules. The D 12 ‐TMC ligand proves to be effective for preventing methyl group hydroxylation as observed, for example, in the case of [(TMCO)Co III (H 2 O)](OTf) 2 . With ozonide [N(CH 3 ) 4 ]O 3 , we instead obtained crystals of [(D 12 ‐TMC‐propyl‐O)Co III (OTf)]B Ar F from [(D 12 ‐TMC)Co II (OTf)]B Ar F. The generation of these transient Fe‐ and Co‐complexes demonstrates that temperatures below values attainable by typical stopped‐flow setups in conjunction with “ligand hardening” provide a promising strategy for studies of reactive complexes.