Reactivity Studies of Oxo–Mo(IV) Complexes Containing Potential Hydrogen-Bond Acceptor/Donor Phenolate Ligands

Reactivity studies of oxo–Mo­(IV) complexes, TpiPrMoO­{2-OC6H4C­(O)­R-κ2O,O′} (R = Me, Et, OMe, OEt, OPh,
NHPh), containing chelated hydrogen-bond donor/acceptor phenolate
ligands are reported. Hydrolysis/oxidation of TpiPrMoO­(2-OC6H4CO2Ph-κ2O,O′) in the presence of methanol
yields tetranuclear [TpiPrMoO­(μ-O)2MoO]2(μ-OMe)2 (1), while condensation
of TpiPrMoO­{2-OC6H4C­(O)­Me-κ2O,O′} and methylamine
gives the chelated iminophenolate complex, TpiPrMoO­{2-OC6H4C­(Me)­NMe-κ2O,N} (2), rather than the aqua complex, TpiPrMoO­{2-OC6H4C­(Me)­NMe-κO}­(OH2). The oxo–Mo­(IV) complexes
are readily oxidized by dioxygen or hydrogen peroxide to the corresponding cis-dioxo–Mo­(VI) complexes, TpiPrMoO2{2-OC6H4C­(O)­R}; in addition,
suitable one-electron oxidants, e.g., [FeCp2]­BF4 and [N­(C6H4Br)3]­[SbCl6], oxidize the complexes to their EPR-active (giso ≈ 1.942) molybdenyl counterparts (3, 4). Molybdenyl complexes
such as TpiPrMoOCl­{2-OC6H4C­(O)­R} (5) and TpiPrMoOCl2 also form when the complexes react with chlorinated solvents. The
ester derivatives (R = OMe, OEt, OPh) react with propylene sulfide
to form cis-oxosulfido–Mo­(VI) complexes, TpiPrMoOS­{2-OC6H4C­(O)­R}, that crystallize as dimeric μ-disulfido–Mo­(V) species,
[TpiPrMoO­{2-OC6H4C­(O)­R}]2(μ-S2) (6−8). The crystal structures
of [TpiPrMoO­(μ-O)2MoO]2(μ-OMe)2, TpiPrMoO­{2-OC6H4C­(Me)­NMe}, TpiPrMoOCl­{2-OC6H4C­(O)­NHPh}·{2-HOC6H4C­(O)­NHPh}, and [TpiPrMoO­{2-OC6H4C­(O)­R}]2(μ-S2) (R = OMe, OEt) are reported.