IODOBENZENE AS LEWIS-ACID - SYNTHESIS AND CRYSTAL-STRUCTURES OF PPH(4)[CL-I-C6H5] AND PPH(4)[BR-I-C6H5]

The donor-acceptor complexes [X-I-C6H5](-) with X(-) = Cl- and Br- hav e been prepared as tetraphenylphosphonium salts from iodobenzene and P Ph(4)X in acetonitrile solutions. They form colourless single crystals , which were characterized by crystal structure determinations. PPh(4) [Cl-I-C6H5]: Space group P2(1)/c, Z = 4. Lattice dimensions at -70 deg rees C: a = 1301.1(5), b = 1457.0(5), c = 1478.8(5) pm, beta = 114.17( 3)degrees.PPh(4)[Br-I-C6H5]: Space group P2(1)/n, Z = 4. Lattice dimen sions at 20 degrees C: a = 1353.9(1), b = 1480.1(2), c = 1375.5(1) pm, beta = 106.13(2)degrees. The halide ions are coordinate at the iodine atom of the iodobenzene molecule in a linear arrangement [X-I-C6H5](- ) with bond lengths Cl-I of 327.9 and Br-I of 347.2 pm.