Synthesis of Alkyl and Aryl Derivatives of closo-B12H122- by the Palladium-Catalyzed Coupling of closo-B12H11I2- with Grignard Reagents

Abstract

The reaction of [N(n-C4H9)4]2[closo-B12H11I], [N(n-Bu)4]2[2], with Grignard reagents, RMgX, in the presence of catalytic amounts of trans-Pd(PPh3)2Cl2 and CuI in either tetrahydrofuran or 1,4-dioxane solution produced the corresponding alkylated or arylated polyhedral borane anions, closo-B12H11R2-, in good yield. By this method, we have synthesized [N(n-C4H9)4]2[closo-B12H11CH3], [N(n-Bu)4]2[3]; [N(n-C4H9)4]2[closo-B12H11C6H5], [N(n-Bu)4]2[4]; and Cs2[closo-B12H11(n-C18H37)], Cs2[5]. The structures of Cs2[3] and PPN2[4] have been determined by X-ray diffraction studies. Crystallographic data are as follows: for Cs2[3], orthorhombic, space group Pmcn, a = 954.6(6) pm, b = 1077.0(7) pm, c = 1396.8(9) pm, Z = 4, R = 0.055; for PPN2[4], which cocrystallized with two molecules of DMSO and one molecule of toluene, triclinic, space group P1̄, a = 1138.4(10) pm, b = 1920.1(17) pm, c = 2143.2(18) pm, α = 93.26(2)°, β = 104.44(2)°, γ = 105.86(2)°, Z = 2, R = 0.076.