Abstract:
The reactivity of (dadi)Ti complexes is partly determined by whether the Redox Non-Innocent di-amide-di-imide (dadi) is in a dianionic or tetraanionic configuration. Structural studies and molecular orbital calculations dovetail with oxidative additions that incur redox changes at the ligand while the metal remains formally Ti(IV). In studies of iron chemistry towards the preparation of Fe(IV) alkylidenes, synthetic and reactivity studies suggest that while the formal oxidation state of iron changes, its actual charge state is Fe(II). Formally Fe(IV)=CRR’ and Fe(IV)=NAd complexes have been prepared, but none are metathesis active, perhaps because the iron lacks the covalency for this transformation. It is suggested that Formal Oxidation States color our judgement, and an alternative is presented in which the transitition metals are assigned a charge state reference to Fe(2+).