Polyhalide anions in crystals. Part 1. Triiodides of the Me₄N⁺, Me₄P⁺, quinuclidinium, 1-azoniapropellane, and 1,4-diazoniabicyclo[2.2.2]octane (DabcoH₂²⁺) cations, and 1,10-phenanthrolinium(1+) tribromide

Abstract

Crystal-structure determinations are reported for Me 4 NI 3 (4MI3, Pnnm, a = 10.107(2), b = 14.141(2), c = 8.252(5) Å, Z = 2), quinuclidinium I 3 (QI3, Pnnm, a = 10.290(2), b = 14.011(2), c = 8.813(2) Å,Z = 2), Me 4 PI 3 (4MPI3,P4 2 /m, a = 15.098(4), c = 13.770(4) Å, Z = 10), 1-azoniapropellane I 3 (API3, P2 1 /c, a = 15.131(7), b = 28.453(6), c = 22.848(8) Å, β = 108.53(3)°, Z = 24), 1,4-diazoniabicyclo[2.2.2]octane (I 3 ) 2 (Da2I3, P2 1 /m, a = 9.671(6), b = 8.127(2), c = 11.144(3) Å, β = 96.60(3)°, Z = 2), and 1,10-phenanthrolinium(1+) Br 3 (phenBr3, [Formula: see text] a = 8.370(2), b = 10.410(4), c = 8.171(2) Å, α = 107.52(2)°, β = 97.35(1)°, γ = 94.84(2)°, Z = 2). The nearly isostructural 4MI3 and QI3 are of a distorted anti-NiAs type. The 4MPI3 and API3 structures can be regarded as consisting of distorted CsCl-type coordination cuboids; both are unexpectedly complex, 4MPI3 (not isostructural with 4MI3) containing cations of two and anions of three types, API3 containing cations of six and anions of seven types. API3 thus represents an extreme case of a frustrated CsCl structure. The ion packing in Da2I3 is related to that in CaF 2 . The distortion of one of the two nonequivalent I 3 − anions in Da2I3 is one of the largest, if not the largest on record (I—I = 2.793(2) and 3.167(2) Å, I-I-I = 172.47(4)°), and attributable to the involvement of the anion in a strong N—H … I bond, H … I = 2.78 Å. The bifurcated H-bond in which the protonated cation nitrogen in phenBr 3 is engaged has an intra-cation, N—H(N)… N, branch and an inter-ion branch, N—H(N)… Br. Key words: crystal structure, hydrogen bond, polyhalide anions, tribromides, triiodides.