Synthesis of Alkyl and Aryl Derivatives of <i>closo</i>-B₁₂H₁₂^2- by the Palladium-Catalyzed Coupling of <i>closo</i>-B₁₂H₁₁I^2- with Grignard Reagents

Abstract

The reaction of [N( n -C 4 H 9 ) 4 ] 2 [ closo -B 12 H 11 I], [N( n -Bu) 4 ] 2 [ 2 ], with Grignard reagents, RMgX, in the presence of catalytic amounts of trans -Pd(PPh 3 ) 2 Cl 2 and CuI in either tetrahydrofuran or 1,4-dioxane solution produced the corresponding alkylated or arylated polyhedral borane anions, closo -B 12 H 11 R 2 -, in good yield. By this method, we have synthesized [N( n -C 4 H 9 ) 4 ] 2 [ closo -B 12 H 11 CH 3 ], [N( n -Bu) 4 ] 2 [ 3 ]; [N( n -C 4 H 9 ) 4 ] 2 [ closo -B 12 H 11 C 6 H 5 ], [N( n -Bu) 4 ] 2 [ 4 ]; and Cs 2 [ closo -B 12 H 11 ( n -C 18 H 37 )], Cs 2 [ 5 ]. The structures of Cs 2 [ 3 ] and PPN 2 [ 4 ] have been determined by X-ray diffraction studies. Crystallographic data are as follows: for Cs 2 [ 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 PPN 2 [ 4 ], which cocrystallized with two molecules of DMSO and one molecule of toluene, triclinic, space group P 1̄, 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.