Oxygen Atom Transfer, Sulfur Atom Transfer, and Correlated Electron−Nucleophile Transfer Reactions of Oxo- and Thiomolybdenum(IV) Complexes: Synthesis of Oxothiomolybdenum(VI) and (Hydroxo)oxomolybdenum(V) Species

Abstract

Reaction of MoIVO(S2PR2)2 with K{HB(Pripz)3} [HB(Pripz)3- = hydrotris(isopropylpyrazol-1-yl)borate] in refluxing toluene affords green L*MoIVO(S2PR2-S,S‘) complexes [L* = HB(3-Pripz)2(5-Pripz)- = hydrobis(3-isopropylpyrazol-1-yl)(5-isopropylpyrazol-1-yl)borate; R = Pri, Ph], which are converted upon reaction with boron sulfide in dichloromethane to the yellow thio analogues L*MoIVS(S2PR2-S,S‘). Crystals of L*MoIVO(S2PPri2) are monoclinic, space group P21/n, with a = 10.024(2) Å, b = 20.999(9) Å, c = 15.368(5) Å, β = 100.57(2)°, V = 3180(2) Å3, and Z = 4. Crystals of L*MoIVS(S2PPh2) are monoclinic, space group P21, with a = 10.801(8) Å, b = 13.100(5) Å, c = 12.023(9) Å, β = 99.56(10)°, V = 1678(2) Å3, and Z = 2. The mononuclear, distorted-octahedral complexes are isostructural and are composed of a terminal chalcogenide ligand [MoO = 1.671(3) Å, MoS = 2.126(3) Å], a bidentate dithiophosphinate-S,S‘ ligand, and a facial, tridentate L* ligand. In both cases the 5-isopropylpyrazole group is bound trans to the MoE group (E = O, S). Oxygen atom transfer to L*MoIVS(S2PR2) and sulfur atom transfer to L*MoIVO(S2PR2) produce the oxo−thio−Mo(VI) complexes L*MoVIOS(S2PR2-S). NOESY experiments confirm that the 5-isopropylpyrazole group is trans to the MoO group in these chiral complexes. Ferrocenium oxidation of L*MoIVE(S2PR2) yields the corresponding oxo− and thio−Mo(V) complexes [L*MoVE(S2PR2-S,S‘)]+, respectively; the [L*MoVO(S2PR2-S,S‘)]+ complexes react with water to produce (hydroxo)oxo−Mo(V) species, L*MoVO(OH)(S2PR2-S), while the thio analogues are decomposed by water. The complex L‘MoVOCl2 [L‘ = HB(3-Pripz)3- = hydrotris(3-isopropylpyrazol-1-yl)borate] was prepared by reacting L‘MoVIO2Cl with PPh3 in dichloromethane; this complex does not react with sulfiding agents to produce the analogous thio complex.