Synthesis and characterization of the novel copper(I) anion [Cu(PPh3)Br2]?

Solid-state 31 P n.m.r., far-i.r. spectroscopy and single-crystal X-ray diffraction techniques have been used to characterize a new type of ionic copper( I) compound: [ PPh,Me] [Cu (PPh,) Br,]. X-Ray analysis shows the PPh, ligand to be co-ordinated to the copper atom of the CuBr, unit in a trigonal planar arrangement, with Cu-P 2.21 0(3), Cu-Br 2.367(2), 2.386(2) A and Br-Cu-Br 11 4.9(1)" {monoclinic, space group Pn, a = 11.779(5), b = 9.914(5), c = 14.705(10) A, p = 94.92(5)", Z = 2, R = 0.037 for 1 570 'observed' [I > 30(/)] reflections}. The far-i.r. spectrum shows a strong band at 195 cm-l assigned to the antisymmetric Cu-Br stretching mode of the CuBr, unit, and a weaker band at 150 cm-I assigned to the symmetric Cu-Br stretching mode. This assignment is supported by an approximate normal-co-ordinate analysis, and the resulting Cu-Br force constant is compared with values obtained in similar analyses of related bromocopper( I) complexes. The cross-polarization magic angle spinning 31 P n.m.r. spectrum shows a strong signal at 21 p.p.m. (relative to 85% H,PO,) due to the cation, and a weaker quartet centred at -1 4 p.p.m. due to the co-ordinated PPh, in the anion, with line spacings due to Cu-P coupling of 1.37,1.69, and 1.92 kHz.Full Tex