Synthesis and structure of fluorosilicic acid compounds with 4-aminobenzoic acid and with 4-aminobenzenesulfonamide

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Journal of Fluorine Chemistry 125 (2004) 1951–1957

Synthesis and structure of fluorosilicic acid compounds with

4-aminobenzoic acid and with 4-aminobenzenesulfonamide

The role of H-bonding in crystal structure formation

V.O. Gelmboldta, A.A. Ennana, Ed.V. Ganinb, Yu.A. Simonovc,M.S. Fonaric,*, M.M. Botoshanskyd

aPhysico-Chemical Institute of Environment and Human Protection of the Ministry of Education and

Science of Ukraine and National Academy of Sciences of Ukraine, 65026 Odessa, UkrainebOdessa State Environmental University, Ministry of Education and Science of Ukraine, Odessa, Ukraine

cInstitute of Applied Physics, Academy of Sciences of Moldova, Academy street, 5 MD 2028 Chisinau, MoldovadDepartment of Chemistry, Technion-Israel Institute of Technology, Technion City, 32000 Haifa, Israel

Received 29 March 2004; received in revised form 19 August 2004; accepted 23 August 2004

Available online 27 September 2004

Abstract

Preparation and characterization of the ammonium hexafluorosilicate salts, 2[R]+[SiF6]2� (R = 4-(aminosulfonyl)benzenammonium) (1),

and 2[R]+[SiF6]2�.4H2O (R = 4-carboxybenzenammonium), (2), are described. These salts, prepared from the reaction of the 4-

aminobenzenesulfonamide or the 4-aminobenzoic acid with fluorosilicic acid, were characterized by IR, mass spectrometry and X-ray

diffraction. 1 and 2 crystallize in monoclinic crystal system (space group P21/c and P21/n, respectively), with Z = 2 in both cases. Compounds

exhibit an extensive system of hydrogen bonding.

# 2004 Elsevier B.V. All rights reserved.

Keywords: Hexafluorosilicate; Aromatic amines; Hydrogen bonding; Crystal structure

1. Introduction

Solutions of fluorosilicic acid (FSA) of different

concentrations are the by-products in the production of

phosphorus-containing fertilizers, phosphoric acid and

elemental phosphorus and are considered as a possible

alternative source of fluorine for chemical industry [1,2]. As

for other complex fluoro-containing acids, FSA does not

exist as the compound H2SiF6 [3], while its crystalline low

stable hydrates of the composition H2SiF6�nH2O (n = 4; 6;

9.5; m.p. 20, �12 and �54 8C respectively) have been

shown from X-ray structural data to be oxonium salts of

compositions (H5O2)2SiF6, (H5O2)2SiF6�2H2O and

(H5O2)2SiF6�4.5H2O [4]. One possible application of

hexafluorosilicate salts is the formation of ionic liquids

* Corresponding author. Tel.: +373 22 73 81 54; fax: +373 22 73 81 49.

E-mail address: [email protected] (M.S. Fonari).

0022-1139/$ – see front matter # 2004 Elsevier B.V. All rights reserved.

doi:10.1016/j.jfluchem.2004.08.003

[5] which generally associate nitrogen-containing organic

cations and inorganic anions. A search in the Cambridge

Structural Database [6] revealed 41 hits for complexes of

amines, linear and aromatic, and macrocycles with the FSA.

The family of hexafluorosilicates of aromatic bases is

restricted to six compounds, in these compounds different

numbers of fluorine atoms are involved in the system of

hydrogen bonding. Thus, in bis(N,N0-bis(3-nitrophenyl)i-

sophthalamide) tetra-n-butylammonium hexafluorosilicate

[7], each [SiF6]2� anion is connected via its equatorial

fluorine atoms within the crown-like cavity formed by two

N,N0-bis(3-nitrophenyl)isophthalamide residues. In co-

crystals with acridinium [8] and quinolinium [9] cations,

only two or five over six fluorine atoms participate in

hydrogen bond network. Hydrates of p-bromoanilinium

and p-toluidinium hexafluorosilicates [10] both formulate a

thick layer with two hydrophobic surfaces formed by the

aromatic rings arranged perpendicular to the layer surface

V.O. Gelmboldt et al. / Journal of Fluorine Chemistry 125 (2004) 1951–19571952

Table 1

Crystal data and structure refinement parameters for 1 and 2

Complex 1 2

Empirical formula C12H18F6N4O4S2Si C14H24F6N2O8Si

Formula weight 488.51 490.44

Crystal system Monoclinic Monoclinic

Space group P21/c P21/n

a (A) 9.747(5) 6.333(1)

b (A) 9.444(4) 25.975(5)

c (A) 9.850(5) 6.891(1)

b (degree) 98.14(2) 115.81(3)

Cell volume (A3) 897.56(8) 1020.5(3)

Z 2 2

Dcalc (g/cm3) 1.808 1.596

m, (mm�1) 0.455 0.214

F(000) 500 508

u range for data collection (degree) 2.11–25.03 3.14–25.35

Limiting indices �11 � h � 11, 0 � h � 7

�11 � k � 10 0� k � 30

�10 � l� 11 �8 � l � 7

Reflections collected/unique 5539/1569 1842/1842

Reflections with I > 2s(I) 1204 1180

Refinement method Full-matrix least-squares on F2

Data/restraints/parameters 1569/4/154 1842/6/194

Goodness-of-fit on F2 1.013 1.029

Final R indices [I > 2s(I)] R1 = 0.0320, R2 = 0.0780 R1 = 0.0495, R2 = 0.1196

R indices (all data) R1 = 0.0471, R2 = 0.0826 R1 = 0.0871, wR2 = 0.1336

Extinction coefficient 0.118(6) 0.31(2)

Largest difference hole/peak (e.A�3) �0.395/0.285 �0.243/0.219

and the hexagonal H-bonded network inside the layer. The

interaction of the hydrazine of 5-amino-1-benzyl-1,2,3-

triazol-4-carbonic acid with fluorosilicic acid leads to a

corresponding trihydrate [11] with a complex system of

hydrogen bonding which combines the components into a

3D grid.

The present work is an exploration of the situation

where fluorosilicic acid and aromatic amines with a second

donor group (SO2NH2 and COOH) in the para-position

to the amine group are combined. The preparation of the

bis(4-(aminosulfonyl)benzenammonium) hexafluorosilicate

[C6H9N2O2S]2[SiF6] (1), and [C7H8NO2]2[SiF6].4H2O (2) is

described. The compounds were characterized by IR, mass

spectrometry and by X-ray diffraction.

2. Results and discussion

Compounds 1–2 crystallize in the monoclinic crystal

system (space groups P21/c and P21/n) with Z = 2. Crystal

structure and refinement data are given in Table 1. Bond

lengths and angles are given in Table 2. The asymmetric

units of 1 and 2 reveal half of the hexafluorosilicate anion in

partial position on the inversion center, one 4-(aminosul-

fonyl)benzenammonium or 4-carboxybenzenammonium

cation, and two water molecules in general positions. The

4-(aminosulfonyl)benzenammonium cation has an angular

shape which is dictated by the N(2)–S(1)–C(1) bond angle

equal to 108.2(1)8. The 4-carboxybenzenammonium cation

has the planar skeleton with practically all non-hydrogen

atoms in the plane of phenyl ring.

The Si–F bond lengths are practically equal and adopt the

values 1.683(1) and 1.684(1) A in compound 1, and range

from 1.660(2) to 1.675(2) A in 2. All fluorine atoms are

involved in strong N–H(NH3+). . .F (1, 2) and O–

H(water). . .F hydrogen bonds (2). In 1 and 2 the [SiF6]2�

anion shows very small deviations from ideal octahedral

geometry. The F(trans)–Si–F(trans) angles are 180.0(3)8 for

1 and 2, the F(cis)–Si–F(cis) angles deviate from the right

angle of 0.5(1)8 in 1 and of 1.2(1)8 in 2. Such a practically

ideal octahedral geometry for the [SiF6]2� anion is rather

unusual; usually, its complete involvement in hydrogen

bonding causes a higher distortion of [SiF6]2� octahedron.

In compound 1, the hydrogen bonds are formed between the

hexafluorosilicate anion and 4-(aminosulfonyl)benzenam-

monium cations. Each of [SiF6]2� octahedra is linked to

eight 4-(aminosulfonyl)benzenammonium cations via

twelve N–H. . .F hydrogen bonds with the participation of

terminal NH3+ and NH2 groups; N. . .F distances lie from

2.778(3) to 3.334(3) A (Fig. 1, Table 3).

In 1, along the a axis, the 4-(aminosulfonyl)benzenam-

monium cation bridges two [SiF6]2� anions, that leads to the

formation of centrosymmetric heterotetramers which are

closed by six N–H. . .F hydrogen bonds. The 4-(aminosul-

fonyl)-benzenammonium cations related by the two-fold

screw axis are separated by N–H. . .O hydrogen bonds

(N(1). . .O(2) 2.894(3) A) and lead to ‘tail-to-head’ chains

running along the c direction (Fig. 2). The cations in the

V.O. Gelmboldt et al. / Journal of Fluorine Chemistry 125 (2004) 1951–1957 1953

Table 2

Selected intermolecular distances (A) and angles (degree) for 1 and 2

1

Si(1)–F(1) 1.684(1) F(1)–Si(1)–F(2) 89.8(1)

Si(1)–F(2) 1.683(1) F(1)–Si(1)–F(3) 90.5(1)

Si(1)–F(3) 1.684(1) F(2)–Si(1)–F(3) 90.5(1)

S(1)–O(1) 1.426(2) F(1)–Si(1)–F(1)#1 180.0(1)

S(1)–O(2) 1.430(2) F(2)–Si(1)–F(2)#1 180.0(1)

S(1)–N(2) 1.590(2) F(3)–Si(1)–F(3)#1 180.0(1)

S(1)–C(1) 1.778(2)

N(1)–C(4) 1.467(3)

C(1)–C(2) 1.382(3)

C(1)–C(6) 1.384(3)

C(2)–C(3) 1.387(3)

C(3)–C(4) 1.371(3)

C(4)–C(5) 1.377(3)

C(5)–C(6) 1.378(3)

2Si(1)–F(1) 1.675(2) F(1)–Si(1)–F(2) 90.45(7)

Si(1)–F(2) 1.658(2) F(1)–Si(1)–F(3) 90.71(9)

Si(1)–F(3) 1.665(2) F(2)–Si(1)–F(3) 90.5(1)

Si(1)–F(2A) 1.62(2) F(1)–Si(1)–F(1)#2 180.0(1)

Si(1)–F(3A) 1.64(1) F(2)–Si(1)–F(2)#2 180.0(2)

O(1)–C(7) 1.210(3) F(3)#2–Si(1)–F(3) 180.0(2)

O(2)–C(7) 1.325(3)

N(1)–C(4) 1.456(4)

C(1)–C(7) 1.483(4)

C(1)–C(6) 1.389(3)

C(1)–C(2) 1.393(3)

C(2)–C(3) 1.364(3)

C(3)–C(4) 1.379(3)

C(4)–C(5) 1.377(3)

C(5)–C(6) 1.373(4)

Symmetry transformations used to generate equivalent atoms: #1 �x, �y,

�z; #2 �x + 2, �y, �z.

chains are arranged in a T-shape with the dihedral angle

between the aromatic rings equal to 88.38. A similar N–

H. . .O hydrogen bond exists in 4-aminobenzenesulphona-

mide [12] and in 4-(aminosulfonyl)benzenammonium

nitrosalycilate [13].

Structure of 1 may also be described as the alternation of

rows of [SiF6]2� anions and rows of organic cations along

the a direction, interconnected by hydrogen bonds into a 3D

Fig. 1. ORTEP view of [SiF6]2� anion surrounded by eight 4-(aminosul-

fonyl)-benzenammonium cations (1). Only the asymmetric unit is num-

bered. H-atoms of C groups are omitted for clarity.

network (Fig. 3). Each cation bridges four neighboring

[SiF6]2� anions and two organic cations.

Compound 2 has the most extensive hydrogen bond

network which involves [SiF6]2� anions, 4-carboxybenze-

nammonium cations and water molecules. In a similar way

to 1, the [SiF6]2� anion serves as a powerful connector. It is

linked to four 4-carboxybenzenammonium cations and four

water molecules via six N–H. . .F and four O–H. . .Fhydrogen bonds (Fig. 4).

The fluorine atoms in the equatorial plane of [SiF6]2�

anion are disordered over two positions, F2, F3 and F2A,

F3A; both sets of fluorine atoms are involved in the

hydrogen-bonding system (Table 3). Each ammonium group

bridges two anions related by the inversion center via three

N–H. . .F interactions which range from 2.834(3) to

2.948(3) A. Only one water molecule, O(1w) is connected

with ammonium group (2.835(3 A)).

The 4-carboxybenzenammonium cations and water

molecules are assembled into positive layers via three O–

H. . .O and one N–H. . .O hydrogen bonds. The water

molecules are bonded into dimer with O(1w). . .O(2w)

separation equal to 2.839(3) A. The organic cations are

connected by their carboxyl tails with the water dimers,

giving rise to chains. The neighboring chains, related by the

inversion center, are H-bonded via one hydrogen of

ammonium group and O(2w) lone pair in the wave-like

layer propagated in the ac plane. The cations are stacked in

parallel and arranged so, that the planar carboxylic group of

one cation is displayed above the phenyl ring of its closest

neighbor, the distances between the closest aromatic rings

range from 3.449 to 3.514 A. Along b axis, the alternation

Fig. 2. View of the rows of [SiF6]2� anions alternating with chains of 4-

(aminosulfonyl)benzenammonium cations in 1.

V.O. Gelmboldt et al. / Journal of Fluorine Chemistry 125 (2004) 1951–19571954

Table 3

Geometry of hydrogen bonds for 1 and 2

D–H. . .A d(D–H) A d(H. . .A) A d(D. . .A) A ff(DHA) (degree) Symmetry transformation for acceptor

1N(1)–H(1A). . .F(1) 0.91(2) 2.06(2) 2.907(3) 153(3) x, y, z

N(1)–H(1B). . .F(2) 0.92(2) 2.42(3) 2.851(3) 109(2) x, y, z

N(1)–H(1B). . .O(2) 0.92(2) 2.07(2) 2.894(3) 149(3) �x + 1, y + 1/2, �z + 1/2

N(1)–H(1C). . .F(2) 0.93(2) 1.86(2) 2.778(2) 170(2) x, �y + 1/2, z + 1/2

N(2)–H(2A). . .F(3) 0.93(2) 1.99(2) 2.894(3) 162(3) x + 1, y, z

N(2)–H(2B). . .F(1) 0.93(2) 2.04(2) 2.903(3) 154(2) �x + 1, y + 1/2, �z + 1/2

N(2)-H(2B). . .F(3) 0.93(2) 2.55(2) 3.334(3) 142(2) x + 1, �y + 1/2, z + 1/2

2O(2)–H(1O). . .O(2W) 0.87(2) 1.77(2) 2.628(3) 171(3) x, y, z

N(1)–H(1A). . .F(2) 0.83(2) 2.09(3) 2.889(3) 160(4) �x + 2, �y, �z

N(1)–H(1A). . .F(3A) 0.83(2) 2.01(3) 2.80(2) 157(4) x, y, z

N(1)–H(1A). . .F(1) 0.83(2) 2.51(4) 2.948(3) 114(3) x, y, z

N(1)–H(1B). . .F(1) 0.83(2) 2.04(3) 2.834(3) 155(4) �x + 1, �y, �z

N(1)–H(1B). . .F(2A)#2 0.85(2) 2.34(4) 2.807(15) 115(3) �x + 1, �y, �z

N(1)–H(1C). . .O(1W) 0.84(2) 2.04(2) 2.835(3) 157(4) x, y, z

O(1W)–H(1W1). . .F(3) 0.83(3) 2.31(3) 3.139(3) 174(4) x � 1, y, z � 1

O(1W)–H(1W1). . .F(3A) 0.83(3) 1.96(3) 2.741(13) 156(4) x � 1, y, z � 1

O(1W)–H(1W1). . .F(2) 0.83(3) 2.60(3) 3.180(3) 127(4) �x + 1, �y, � z � 1

O(1W)–H(2W1). . .O(1) 0.84(3) 1.95(3) 2.789(3) 178(3) x � 1/2, �y + 1/2, z � 1/2

O(2W)–H(1W2). . .F(3) 0.84(3) 2.07(3) 2.905(3) 172(4) �x + 3/2, y + 1/2, �z + 1/2

O(2W)–H(1W2). . .F(2A) 0.84(3) 2.02(3) 2.744(15) 144(3) �x + 3/2, y + 1/2, �z + 1/2

O(2W)–H(2W2). . .O(1W) 0.84(3) 2.01(3) 2.839(3) 173(4) x � 1/2, �y + 1/2, z + 1/2

Fig. 3. Crystal packing for 1.

close to that encountered in 1 of the rows of [SiF6]2� anions

and 4-carboxybenzeneammonium cations is observed (Fig.

5). The positive and negative rows run along the c direction.

The [SiF6]2� anions bind the positive layers via a lot of N–

H. . .F and O–H. . .F hydrogen bonds with the formation of

3D grid (Fig. 6).

The significant IR frequencies for 1 and 2 in comparison

with the corresponding free bases are summarized in Table

4. In the IR spectrum of 1, the n(NH2) and n(NH3+)

frequencies represent the wide bands with several maxima in

the range 3350–2600 cm�1. Intense bands at 1320 and

1175 cm�1, which can be attributed to nas(SO2) and ns(SO2),

are slightly shifted in comparison with the free base. The

diffused character of the maxima of the bands n(NH3+) and

n(OH) in the range 3500–2600 cm�1 in the spectrum of 2 is

probably correlated to the participation of the corresponding

Fig. 4. ORTEP view of [SiF6]2� anion surrounded by four 4-carboxyben-

zeneammonium cations and four water molecules in 2. Only the asymmetric

unit is numbered. H-atoms of C-groups are omitted for clarity.

V.O. Gelmboldt et al. / Journal of Fluorine Chemistry 125 (2004) 1951–1957 1955

Fig. 5. The alternation of rows of [SiF6]2� anions and positive layers in 2.

functional groups in the system of intermolecular hydrogen

bonding. Deformation vibrations, d(NH3+) and d(H2O),

present under complicated large intense bands with the

maximum at 1625 cm�1. The intense bands at 740 and

745 cm�1 and the band at 720 cm�1 more intense in 1 are

connected with the n(SiF) vibrations of the [SiF6]2� anions.

The d(SiF2) vibrations are registered in the form of doublet

and triplet bands at 470, 460, 430 cm�1 and 480, 440 cm�1

respectively. It must be noted that the multiple character of

the vibrations of [SiF6]2� anions in 1 and 2 is correlated with

the deviation very small in 1 of the hexafluorosilicate anion

geometry from the ideal octahedral one, the distortion being

more pronounced in 2.

In conclusion, some general remarks could be made. The

linear and aromatic amines, alkylamines [9,14], propargi-

lamine [15], nitrogen-containing heterocycles of piperidine

Fig. 6. Section of the crystal packing in 2 parallel to the ac plane.

or quinoline types [9], the derivatives of guanine [16,17],

hydrazides, thiosemicarbazides, protonated by the FSA,

form co-crystals exclusively with highly symmetric

hexafluorosilicate anion, [SiF6]2�. The most interesting

products with diversified structures were formed in the

reactions of FSA with crown ethers and their partially

substituted aza analogs. The authors managed to stabilize

the [SiF6]2� anion and all products of its hydrolytic

transformations, trans-SiF4�2H2O, [SiF5�H2O]�, [SiF5]�, in

these complexes [18,19]. According to X-ray diffraction

data, the neutral components of structure [(18-crown-6)

(trans-SiF4�2H2O)�2H2O] are linked by a system of O–

H. . .Ocrown hydrogen bonds, the outersphere water

molecule acts as a bridge between trans-SiF4�2H2O and

18-crown-6 (L1). When the cis–syn–cis isomer of dicyclo-

hexano-18-crown-6 (L2), whose macrocyclic plane is

unequivalently screened sterically, reacts with FSA, it gives

the ionic complex [(L2�H3O)(SiF5)], where the outer-sphere

[SiF5]� anion is bonded to the macrocyclic cation

(L2�H3O)+ only by electrostatic interactions [20]. Mono-

aza-18-crown-6 (L3) and 1,10-diaza-18-crown-6 (L4) are

protonated in acid medium, and in the ionic complexes

[(L3H.H2O)(SiF5�H2O)�H2O] and [(L4H2)(SiF5�H2O)2] they

stabilize monoaquapentafluorosilicate anion, [SiF5�H2O]�,

while 1,7-diaza-15-crown-5 (L5) and hexafluorosilicate

anion give the complex [(L5H2)(SiF6)]. In all of these

complexes the components are held together by a

complicated system of hydrogen bonds. The 14- and 12-

membered tetraazamacrocycles, (cyclam, cyclen and pyo-

fan) [21], similarly to arylamines, give the crystalline

complexes exclusively with hexafluorosilicate anion due to

the formation of numerous N–H. . .F and N–H. . .Owater

hydrogen bonds.

4-aminobenzoic acid and 4-aminobenzenesulfonamide as

all previously studied arylamines give the highly stable

hexafluorosilacates sustained by the very diverse system of

hydrogen bonds.

3. Experimental

IR spectra were recorded on a Specord 75 IR spectro-

photometer (range 4000–400 cm�1, samples as a suspen-

sions in Nujol mulls between KRS-5 windows). Fluorine

content was determined with a fluoride ion selective

electrode. Mass spectra were obtained on a MX-1321

instrument (the ionizing energy was 70 eV, samples were

directly introduced into the ion source).

3.1. Synthesis of (4-ammoniumbenzenesulfonamide)

hexafluorosilicate (1)

A solution of 1.72 g (0.01 mol) of 4-aminobenzenesul-

fonamide in a mixture of 25 mL of methanol and of 20 mL

of water was added to 9 mL of 45% FSA and evaporated at

room temperature. Colourless transparent crystals, of a

V.O. Gelmboldt et al. / Journal of Fluorine Chemistry 125 (2004) 1951–19571956

Table 4

IR spectral data for 1 and 2 and free organic ligands

H2NC6H4SO2NH2 1 Assignment H2NC6H4COOH 2 Assignment

3470 m 3520 m

3430 m 3460 m

3340 s 3350 s 3385 s 3380 sbr

3300 s

3200 s 3230 s n(NH) n(NH) n(OH)

3120 s 3150 sbr

3080 sbr

2735 m

2620 m 2630 mbr

1720 sh

1700 sh 1690 sh nas(COO)

1615 s 1626 sh d(NH2), 1625 s d(NH2)

1600 sh d(NH3+) 1585 s 1590 sh d(NH3

+)

1585 s 1570 sh

1565 sh n(CC)

1550 sh 1550 sh 1560 sh 1550 sh n(CC)

1500 s 1500 sh 1500 sh 1500 sh

1335 sh 1320 vs nas(SO2) 1330 w ns(COO)

1300 sh 1300 sh

1280 vs 1270 m 1270 vs

1180 m 1175 s ns(SO2) 1190 sh

1130 vs 1125 s 1130 m 1135 m

1090 m

1025 w r(NH2) 1040 sh

990 sh 990 w 980 sh 985 sh

960 v 960 sh 926 v r(NH3+)

930 m r(NH3+) r(CNH)

880 m r(CNH) 880 sh 880 sh

840 sh 855 sh 840 sh 840 sh

830 m 835 m

740 sh n(SiF) 745 s n(SiF)

720 sh 720 s 720 sh 720 sh

670 s 670 m d(SO2)

640 sh 640 sh 640 s t(NH2) t(NH3+)

620 sh t(NH2), t(NH3+) d(CCH) d(CCH) d(COO)

560 sh r(H2O)

540 s 545 s 540 m 545 sh

470 m 480 m

460 s d(SiF2) d(SiF2)

430 sh 440 m

Note: w = weak, m = medium, s = strong, v = very, sh = shoulder, br = broad.

qualitative yield, soluble in water, m.p. 250–252 8C. Anal.

found, %: F 23.5, Si 5.9, N 11.7 Calcd. for

C12H18F6N4O4S2Si, F 23.33, Si 5.8, N 11.5.

Mass spectrum: [C6H8N2O2S]+ (m/z = 172, I = 100%),

[C6H6NO2S]+ (m/z = 156, I = 88%), [C6H6N]+ (m/z = 92,

I = 72%), [SiF3]+ (m/z = 85, I = 19%).

3.2. Synthesis of bis(4-ammoniumbenzoic acid)

hexafluorosilicate tetrahydrate (2)

A solution of 1.37 g (0.01 mol) of 4-aminobenzoic acid in

a mixture of 40 mL of methanol and of 60 mL of water was

added to 9 mL of 45% FSA and evaporated at room

temperature. Crystals of complex, suitable for X-ray

investigation, were obtained by recrystallization from water.

Colourless transparent crystals, of a qualitative yield,

soluble in water, m.p. 240–241 8C. Anal. found, %: F

23.2, Si 5.9, N 5.5; Calcd. for C14H24F6N2O8Si, F 23.2, Si

5.7, N 5.7.

Mass spectrum: [C7H7NO2]+ (m/z = 137, I = 97%),

[C7H6NO]+ (m/z = 120, I = 100%), [C6H6N]+ (m/z = 92,

I = 33%), [SiF3]+ (m/z = 85, I = 70%).

3.3. Structure determination

The X-ray intensity data were collected at room

temperature on a Nonius Kappa CCD diffractometer

equipped with graphite monochromated Mo-Ka radiation

using v rotation with a sample-to-detector distance of

40 mm. Unit cell parameters were obtained and refined

V.O. Gelmboldt et al. / Journal of Fluorine Chemistry 125 (2004) 1951–1957 1957

using the whole data set. Frames were integrated and

corrected for Lorentz and polarization effects using DENZO

[22]. The scaling as well as the global refinement of

crystal parameters were performed by SCALEPACK [22].

Reflections, which were partly measured on previous and

subsequent frames, were used to scale these frames on each

other. The structure solution and refinement proceeded

similarly for both structures using SHELX-97 program

package [23]. Direct methods yielded all non-hydrogen

atoms of the asymmetric unit. These atoms were treated

anisotropically (full-matrix least squares method on F2).

In 2 the fluorine atoms F2 and F3 are disordered over two

orientations in the equatorial plane. The occupancy factors

refined to 0.898(5) for the major component (F2, F3) and

0.102(5) for the minor component (F2A and F3A), only

major position was treated anisotropically. The disorder was

justified by the reasonable system of hydrogen bonding

(Table 3). Hydrogen atoms of C groups were placed in

calculated positions with their isotropic displacement

parameters riding on those of the parent atoms, while

H-atoms of ammonium group and water molecules were

found from differential Fourier maps at an intermediate

stage of the refinement and were treated isotropically using

SADI restraints.

Crystallographic data (cif files) for the structural analysis

of complexes 1 and 2 have been deposited with the

Cambridge Crystallographic Data Center, CCDC Nos.

232837 and 232838. Copies of this information may be

obtained free of charge from The Director, CCDC, 12 Union

Road, Cambridge, CB21EZ, UK (Fax: +44 1233 336 033;

E-mail: [email protected] or www: http://www.ccdc.

cam.ac.uk).

Acknowledgment

The diffraction data were collected at the Department of

Chemistry, Technion, The Haifa, through the cooperation of

Professor Menahem Kaftory whom we would like to

acknowledge.

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