DIOXOMOLYBDENUM(VI) COMPLEXES OF THE HYDROTRIS(3,5-DIMETHYL-1-PYRAZOLYL)BORATE LIGAND - SYNTHESIS AND OXYGEN ATOM TRANSFER-REACTIONS

The complexes {HB(Me2pz)3}MoO2X (HB(Me2pz)3−= hydrotris(3,5-dimethyl-l-pyrazolyl)borate; X = F−Cl−, Br−, NCS−, OPh−, OMe−, SPh−) have been prepared and characterized, and the crystal structure of the X = NCS−complex has been determined. {HB(Me2pz)3}MoO2(NCS) crystallizes in the space group Pl, with a = 8.049 (1) Å, b = 8.669 (1) Å, c = 17.397 (2) Å, α = 79.98 (1)°, β = 81.30 (1)°, γ = 78.39 (1)°, and Z = 2; refinement resulted in Rw= 0.056 (3136 reflections with F°2> MF°2), 273 variable parameters). Three representative complexes (X = Cl−, SPh−, OPh−) react with Ph3P at room temperature to yield Ph3PO and a molybdenum-containing product having a composition dependent upon the solvent used. In DMF, pyridine, or acetonitrile, the Mo(IV) complexes {HB(Me2pz3)}MoOX(solvent) are formed as a result of the oxygen atom transfer reaction and subsequent solvent coordination. In dichloromethane, the ultimate products are the Mo(V) complexes {HB(Me2pz)3}MoOClX. In toluene, binuclear Mo(V) complexes {HB(Me2pz)3}2Mo2O3X2form from reaction of the transient {HB(Me2pz)3}MoOX and the starting complex. The identities of two reaction products have been confirmed by crystal structure determinations. {HB(Me2pz)3}MoO(Cl)(NCS) crystallizes in space group Pl, with a = 8.093 (1) Å, b = 8.840 (1) Å, c = 17.432 (3) Å, α = 79.30 (1)°, β = 80.66 (1)°, γ = 78.40 (1)°, and Z = 2; refinement resulted in Rw= 0.053 (2864 reflections with F°2> 3σ(F°2), 277 variable parameters). The structure is isomorphous with that of {HB(Me2pz)3}MoO2(NCS). {HB(Me2pz)3}MoO(Cl)(NC5H5) crystallizes in Pl, with a = 9.636 (1) Å,b = 14.319 (2) Å, c = 20.802 (3) Å, α = 79.90 (1)°, β = 84.47 (1)°, γ = 77.82 (1)°, and Z = 4; refinement resulted in Rw= 0.071 (6777 reflections with F°2> 3σ(F°2), 589 variable parameters). The oxidation of Ph3P to Ph3PO by Me2SO is catalyzed by {HB(Me2pz)3}MoO2X complexes with X = Cl−, SPh−, and OPh−. © 1990, American Chemical Society. All rights reserved.