Synthesis and crystal structures of (p-bromobenzyl)triphenylphosphonium bromides, [(p-Br-C6H4-CH2)P(C6H5)(3)](+) Br-; [(p-Br-C6H4-CH2)P(C6H5)(3)](+) Br-2(-) and [(p-Br-C6H4-CH2)P(C6H5)(3)](+) Br-3(-)

[(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 as Br- anions and [(p-Br-C6H4-CH2)P(C6H5)(3)](+) cations, with weak interactions between the chlorine atoms of the CH2Cl2 molecules and the bromine 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 methylenechloride solution. The yellow-red crystals of 2 are orthorhombic, space 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 linear 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-CH2)P(C6H5)(3)](+) cations and linear, slightly asymmetrical Br-3(-) anions. In all cases the cation has a slightly irregular tetrahedral geometry around the P atom.