The Impact of Ligand Oxidation State and Fold Angle on the Charge Transfer Processes of Mo^IVO‐Dithione Complexes

Abstract

We report a series of mononuclear monooxo Mo(IV) complexes possessing either one or two fully oxidized dithiolene ligands; [MoOCl(R2Dt0)2][X], (1 and 2), and MoO(p‐SC6H4Y)2(R2Dt0), (3 and 4), (R=Me, iPr; X=PF6, SbF6, BF4; Y=H, Cl, F, CF3, Me, tBu, OMe). Either four or two quasi‐reversible ligand‐based redox couples are detected depending upon the number of fully oxidized dithiolene ligands present. The molecular structure of 3 and 4 exhibit a large (47° to 70°) fold angle along the S⋅⋅⋅S vector of the dithione ligand. The UV‐Vis spectra of 3 and 4 exhibit a low energy charge transfer band at ∼540 nm that are red‐shifted ∼200 nm compared to the spectra of 1 and 2. Density Functional Theory (DFT) calculations show that the low energy charge transfer band of 3 and 4 is heavily influenced by ligand fold angle. Reducing the fold angle decreases the charge transfer energy, and the transition becomes more ligand‐based.

Interligand communication in a metal mediated LL′CT system – a case study

“…Crystallographic data for a similar Mo IV –Dt 0 system shows the Dt 0 fold angle to be sensitive to the electron donating and withdrawing properties of Dt 0 substituents. 38 Gas phase optimizations were performed on 2 , 5 , 7 , and 8 to understand the intrinsic propensity of the Dt 0 fold angle in relationship to dithiolene substituents. The Dt 0 fold angle of 6 will be used as the reference since it is the only compound with a molecular structure.…”

Inspired by Nature—Functional Analogues of Molybdenum and Tungsten-Dependent Oxidoreductases

“…The molybdenum center can, for instance, be substituted by rhenium, due to the diagonal relationship between these two metals leading to an additional class of efficient OAT reagents [25][26][27][28][29]. Commonly, the examination of OAT reactivity includes natural and non-natural oxygen acceptors (organic phosphines, sulfite, selenite, arsenite) and oxygen donors (N-oxides, S-oxides), which still represent well-established, state-of-the-art approaches towards modelling either individual half reactions or entire OAT-only catalytic cycles when they are combined [21][22][23]27,[30][31][32][33][34]. This means that a reduced substrate and an oxidized substrate are mixed with the functional model complex, which is taking the oxygen atom from one substrate and delivering it to the other without passing through any PCET.…”