Amine-Poly(Hydrogen Fluoride) Solid Complexes: New Studies of Formation, Crystal Structures, and Hn−1Fn− Ion Diversity

Abstract

After earlier work in this laboratory on phase relations and crystal structures in the quasibinary system of hydrogen fluoride and pyridine, six lowmelting adducts with trimethyl-and triethylamine in lieu of pyridine have now been identified and their structures determined at À 150 8C:À 87 8C, monoclinic, P2 1 , Z 2), Me 3 N5 HF (m.p. À 93 8C (decomp), triclinic, P1 Å , Z 2) and Me 3 N´7 HF (m.p. À 88 8C, hexagonal, P6 3 , Z 2). Structure analysis was also performed on a further pyridine adduct: Py´6 HF (m.p.With the base protonated and the hydrogen fluoride content correspondingly deprived of one proton, all structures are ionic. They are described with respect to the F ± H´´´F and N ± H´´´F hydrogen bonding and the various H nÀ1 F À n complex ions present. These ions and others of the same kind observed in crystal structures are surveyed with regard to homology (size) and isomerism.

Hexafluorosilicates of bis(aminopyridinium). The relationship between H-bonding system and solubility of salts

“…Apparently, H-bonds should definitely influence on the geometry of anion (in the case of complex anion) and on physicochemical properties of complex in a whole; moreover, the effects of H-bonds have appeared to be decisive in synthetic chemistry, for example, for the stabilization of the poor stable anions of the type [H nÀ1 F n ] À (n = 3-5) [7][8][9], [SiF 5 (H 2 O)] À [10] and [GeF 5 (H 2 O)] À [11]. The high H-acceptor affinity of fluoride-anion [12], which is substantially preserved also by a covalently bound fluorine in complex fluorocontaining anions such as [SiF 6 ] 2À [13], makes ''onium'' hexafluorosilicates attractive models to clarify the features that influence on the interionic H-bonds and on the structural properties of the complexes.…”

Fluorohydrogenate Ionic Liquids, Liquid Crystals, and Plastic Crystals

“…As the number of HF molecules increases, the (FH) n F − anion gives a variety of structures. The (FH) 2 F − anion has C 2v symmetry with two HF units bound to the central F atom ( Figure 5.2 (b)) [12,[23][24][25][26][27][28]. The F⋯F distance (∼2.35 Å) is larger than that in FHF − and the position of the H atom is deviated from the middle of two F atoms to the terminal F atom.…”

“…The F⋯F distance (∼2.35 Å) is larger than that in FHF − and the position of the H atom is deviated from the middle of two F atoms to the terminal F atom. The (FH) n F − anions with n ≥ 3 have isomers; (FH) 3 F − adopts C 3v ( Figure 5.2 (c)) [12,24,26,27,[29][30][31] and C 2v ( Figure 5.2 (d)) [26,32] symmetries and (FH) 4 F − adopts T d ( Figure 5.2 (e)) [6,28,30,31] and C 1 ( Figure 5.2 (f)) [28] symmetries. Although (FH) 4 F − with C 1 symmetry is known in the crystal structure, the stable structure in gas phase is considered to belong to C s symmetry with the F⋯F⋯F⋯F dihedral angle of 90°.…”

“…Although (FH) 4 F − with C 1 symmetry is known in the crystal structure, the stable structure in gas phase is considered to belong to C s symmetry with the F⋯F⋯F⋯F dihedral angle of 90°. Two isomers of (FH) 5 [28]. Only the isomer known for (FH) 6 F − has a shape like a three-bladed pinwheel with nearly C 3h symmetry (Figure 5.2 (i)) [28].…”

“…Two isomers of (FH) 5 [28]. Only the isomer known for (FH) 6 F − has a shape like a three-bladed pinwheel with nearly C 3h symmetry (Figure 5.2 (i)) [28]. The largest (FH) n F − determined in a crystal structure is (FH) 7 F − which is best described as [(FH)(FH)] 2 F[(HF) (HF)(HF)] with C 1 symmetry [30].…”