Enhanced thermal stability in organodiborane(4) compounds: Synthesis and structural characterization of MeO(Mes)BB(Mes)OMe, Mes2BB(Mes)OMe, Mes2BB(Mes)Ph, and Mes2BB(Mes)CH2SiMe3 (Mes = 2,4,6-Me3C6H2)

Article abstract of DOI:10.1021/om00043a019

A series of organo-substituted diborane(4) compounds have been prepared and characterized by X-ray crystallography and NMR spectroscopy. The compounds MeO(Mes)BB(Mes)OMe (1), Mes₂BB(Mes)OMe (2), Mes₂BB(Mes)Ph (3), and Mes₂BB(Mes)CH₂SiMe₃ (4) were synthesized by the reaction of the stable precursor species B₂(OMe)₄ with the appropriate organolithium reagent. All the compounds are thermally stable, air- and moisture-sensitive, colorless crystalline solids. Moreover, the species 3 and 4 exhibit significantly enhanced thermal stability in comparison to previously reported tetraalkyldiborane(4) derivatives. The X-ray structures of 3 and 4 represent the first structural reports for tetraorganodiborane(4) species. Crystal data with Mo Kα (λ = 0.71069 A?) radiation at 130 K are as follows: 1, MeO(Mes)BB(Mes)OMe, a = 8.324 (2) A?, b = 14.744 (3) A?, c = 15.395 (5) A?, Z = 4, orthorhombic, space group Pc2₁b, R = 0.059 for 1488 (I > 2σ(I)) data; 2, Mes₂BB(Mes)OMe·0.5C₅H₁₂, a = 8.666 (10) A?, b = 12.500 (13) A?, c = 13.858 (16) A?, α = 109.90 (8)°, β = 100.51 (8)°, γ = 99.68 (8)°, Z = 2, triclinic, space group P1, R = 0.090 for 1554 (I > 2σ(I)) data; 3, Mes₂BB(Mes)Ph, a = 8.911 (3) A?, b = 12.142 (3) A?, c = 13.961 (3) A?, α = 104.04 (2)°, β = 93.88 (3)°, γ = 107.86 (2)°, Z = 2, triclinic, space group P1, R = 0.075 for 1834 (I > 2σ(I)) data; 4, Mes₂BB(Mes)CH₂SiMe₃, a = 12.221 (8) A?, b = 15.880 (7) A?, c = 16.152 (6) A?, α = 112.26 (3)°, β = 93.96 (4)°, γ = 89.97 (4)°, Z = 4 (two independent molecules), triclinic, space group P1, R = 0.087 for 2445 (I > 2σ(I)) data.