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Crystal chemistry of tetraradial species. Part 2. Crystal structures of Et 4 NI, Ph 4 PBr•H 2 O, and Ph 4 PBr•2H 2 O

1988; NRC Research Press; Volume: 66; Issue: 12 Linguagem: Inglês

10.1139/v88-474

1480-3291

Beverly R. Vincent, Osvald Knop, Anthony Linden, T. Stanley Cameron, Katherine N. Robertson,

Crystallography and molecular interactions

The crystal structure of Et 4 NI [Formula: see text], a = 8.860(2) Å, c = 6.933(1) Å, Z = 2) has been redetermined and those of Ph 4 PBr•H 2 O ([Formula: see text], a = 10.005(3) Å, b = 10.659(2) Å, c = 10.697(4) Å, α = 102.61(2)°, β = 83.39(3)°, γ = 108.09(3)°, Z = 2) and Ph 4 PBr•2H 2 O (Pnma, a = 16.255(4) Å, b = 10.810(4) Å, c = 12.667(9) Å, Z = 4) have been determined for the first time. In the Et 4 NI structure Et 4 N + cations in an extended S 4 conformation and I − anions are arranged in a zincblende-type packing. The two hydrate structures are ionic and very similar. The anion in the monohydrate is a centrosymmetric cyclic dimer [Br 2 (OH 2 ) 2 ] 2− ; in the dihydrate the anion, which is an almost planar infinite [Br − (OH 2 ) 4/2 ] x chain 11b, appears to be of a novel type. If the H 2 O molecules are not considered, the ion packing in both hydrates may be regarded as of the anti-NiAs type. The ion packing in R 4 EX structures and the conformation of the Et 4 N + ion in crystals are discussed in some detail.