Reactivity studies of oxo-Mo(IV) complexes, Tp(iPr)MoO{2-OC6H4C(O)R-kappa O-2,O'} (R = Me, Et, OMe, OEt, OPh, NHPh), containing chelated hydrogen-bond donor/acceptor phenolate ligands are reported. Hydrolysis/oxidation of Tp(iPr)MoO(2-OC6H4CO2Ph-kappa O-2,O'} in the presence of methanol yields tetranuclear [Tp(iPr)MoO(mu-O)(2)MoO](2)(mu-OMe)(2) (1), while condensation of Tp(iPr)MoO{2-OC6H4C(O)Me-kappa O-2,O'} and methylamine gives the chelated iminophenolate complex, Tp(iPr)MoO{2-OC6H4C(Me)NMe-kappa O-2,N} (2), rather than the aqua complex, Tp(iPr)MoO{2-OC6H4C(Me)NMe-kappa O} (OH2). The oxo-Mo(IV) complexes are readily oxidized by dioxygen or hydrogen peroxide to the corresponding cis-dioxo-Mo(VI) complexes, Tp(iPr)MoO(2){2-OC6H4C(0)R}; in addition, suitable one-electron oxidants, e.g., [FeCp2]BF4 and [N(C6H4Br)(3)][SbCl6], oxidize the complexes to their EPR:active (g(iso) approximate to 1.942) molybdenyl counterparts (3, 4). Molybdenyl complexes such as Tp(iPr)MoOCl{2-OC6H4C(O)R} (5) and Tp(iPr)MoOCl(2) 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, Tp(iPr)MoOS{2-OC6H4C(O)R}, that crystallize as dimeric mu-disulfido-Mo(V) species, [Tp(iPr)MoO{2-OC6H4C(O)R}](2)(mu-S-2) (6-8). The crystal structures of [Tp(iPr)MoO(mu-O)(2)MoO]2(mu-OMe)(2), Tp(iPr)MoO{2-OC6H4C(Me)NMe}, Tp(iPr)MoOCl{2-OC6H4C(O)NHPh}center dot{2-HOC6H4C(O)NHPh}, and [Tp(iPr)MoO{2-OC6H4C(O)R}](2)(mu-S-2) (R = OMe, OEt) are reported.