SYNTHESIS AND CRYSTAL-STRUCTURES OF (P-BR OMOBENZYL)TRIPHENYLPHOSPHONIUM BROMIDES, (C6H5)(3)](-),[(P-BR-C6H4-CH2)P(C6H5)(3)](+)BR2(-) AND [(P-BR-C6H4-CH2)P(C6H5)(3)](+)BR3(-)()BR()

[(p-Br-C6H4-CH2)P(C6H5)(3)]Br-+(-).(CH2Cl2)(2.5) (1) has been prepared by the reaction of tri phenylphosphine with p-bromobenzylbromide and its structure determined (triclinic, space group <P(1)over bar>, Z = 2 , a = 1198.03(12), b = 1245.80(11), c 1258.42(12)pm, alpha = 100.170(8 ), beta = 103.543(9), gamma = 118.158(7)degrees. The compound exists a s Br- anions and [(p-Br-C6H4-CH2)P(C6H5)(3)](+) cations, with weak int eractions between the chlorine atoms of the CH2Cl2 molecules and the b romine bonded in the cation. [(p-Br-C6H4-CH2)P(C6H5)(3)]Br-2 (2) and [ (p-Br-C6H4-CH2 )P(C6H5)(3)]Br-3 .(CH2Cl2)(1.5) (3) have been obtained by reactions of the corresponding amounts of bromine with 1 in methyle nechloride solution. The yellow-red crystals of 2 are orthorhombic, sp ace group Peen, Z = 8, a = 2060.8(3), b = 1223.6(4), c = 1860.8(3) pm. Compound 2 exists as [(p-Br-C6H4-CH2)P(C6H5)(3)](+), cations and line ar Br-4(2-) units with a bromide-bromine distance of 297.3 (4) pm. The red crystals of (3) are triclinic, space group <P(1)over bar>, Z = 2, a = 1171.16(7), b = 1260.97(8), c = 1270.35(7)pm, alpha = 65.510(5), beta = 75.811(5), gamma = 62.320(5)degrees, and contain [(p-Br-C6H4-CH 2)P(C6H5)(3)](+) cations and linear, slightly asymmetrical Br-3(-) ani ons. In all cases the cation has a slightly irregular tetrahedral geom etry around the P atom.