OXYGEN-ATOM TRANSFER, SULFUR ATOM-TRANSFER, AND CORRELATED ELECTRON-NUCLEOPHILE TRANSFER-REACTIONS OF OXOMOLYBDENUM(IV) AND THIOMOLYBDENUM(IV) COMPLEXES - SYNTHESIS OF OXOTHIOMOLYBDENUM(VI) AND (HYDROXO)OXOMOLYBDENUM(V) SPECIES

Reaction of (MoO)-O-IV(S(2)PR(2))(2) with K{HB(Pr(i)pz)(3)} [HB(Pr(i)p z)(3)(-) = hydrotris(isopropylpyrazol-1-yl)borate] in refluxing toluen e affords green L(MoO)-O-IV(S(2)PR(2)-S,S') complexes [L* = HB(3-Pr(i )pz)(2)(5-Pr(i)pz)(-) = robis(3-isopropylpyrazol-1-yl)(5-isopropylpyra zol- 1-yl)borate; R = Pr-i, Ph], which are converted upon reaction wit h boron sulfide in dichloromethane to the yellow thio analogues L(MoS )-S-IV(S(2)PR(2-)S,S'). Crystals of L(MoO)-O-IV(S2PPr2i) are monoclin ic, space group P2(1)/n, with a = 10.024(2) Angstrom, b = 20.999(9) An gstrom, c = 15.368(5) Angstrom, beta = 100.57(2)degrees, V = 3180(2) A ngstrom(3) and Z = 4. Crystals of L(MoS)-S-IV(S(2)PPh(2)) are monocli nic, space group P2(1), with a = 10.801(8) Angstrom, b = 13.100(5) Ang strom, c = 12.023(9) Angstrom, beta = 99.56(10)degrees, V = 1678(2) An gstrom(3), and Z = 2. The mononuclear, distorted-octahedral complexes are isostructural and are composed of a terminal chalcogenide ligand [ Mo = 0 = 1.671(3) Angstrom, Mo = S = 2.126(3) Angstrom], a bidentate d ithiophosphinate-S,S' ligand, and a facial, tridentate L ligand. in b oth cases the 5-isopropylpyrazole group is bound trans to the Mo = E g roup (E = O, S). Oxygen atom transfer to L(MoS)-S-IV(S(2)PR(2)) and s ulfur atom transfer to L(MoO)-O-IV(S(2)PR(2)) produce the oxo-thio-Mo (VI) complexes LMo-VI-OS(S(2)PR(2)-S). NOESY experiments confirm that the 5-isopropylpyrazole group is trans to the Mo = E group in these c hiral complexes. Ferrocenium oxidation of LMo(IV)E(S(2)PR(2)) yields the corresponding oxo- and thio-Mo(V) complexes [LMo(V)E(S(2)PR(2)-S, S')](+), respectively; the [L(MoO)-O-V(S(2)PR(2)-S,S')](+) complexes react with water to produce (hydroxo)oxo-Mo(V) species, L(MoO)-O-V(OH )(S(2)PR(2)-S), while the thio analogues are decomposed by water. The complex L'(MoOCl2)-O-V [L' = HB(3-Pr'pz)(3)(-) = hydrotris(3-isopropyl pyrazol-1-yl)borate] was prepared by reacting L'(MoO2Cl)-O-VI with PPh (3) in dichloromethane; this complex does not react with sulfiding age nts to produce the analogous thio complex.