Synthesis and X-ray structural characterization of the triphenylphosphine derivative of the closo-dodecaborate anion, closo-[B12H11P(C6H5)3][N(n-C4H9)4]

The reaction of a molar excess of closo-[B12H11I][N(n-C4H9)4]2 (1) with tetrakis(triphenylphosphine)palladium (0), Pd(0)L4, yields to the formation of the title monoanionic compound, closo-[1-B12H11P(C6H5)3][N(n-C4H9)4] (2). The structure of 2 was determined by X-ray diffraction analysis performed on a single crystal. The mechanism of formation of 2 is also discussed. We suggested a two-step mechanism for the formation of 2 consisting in a oxidative addition of the palladium complex followed by a reductive elimination involving P(C6H5)3 and assisted by Na2CO3. To our knowledge, this is the first example of monosubstitution of B12 with formation of boron–phosphorus bond.