Anhydrous ammonioguanidinium(2+) and dihydrated bis[aminoguanidinium(1+)] hexafluoro­silicates: new co-products of preparing ferroelectric ammonioguanidinium(2+) hexafluoro­zirconate

Ammonioguanidinium hexafluorosilicate, CH₈N·­SiF, and bis(aminoguanidinium) hexafluorosilicate dihydrate, 2CH₇N·SiF·2H₂O, are new materials formed as by-products in course of preparing ferroelectric CH₈N₄ZrF₆ in the presence of glassware. Their structures were determined for comparison with the corresponding hexafluorozirconates. All atoms including the eight H atoms in the CH₈N cation and the seven H atoms in the CH₇N cation have been located and refined with wR(F²) = 0.0653, R = 0.0255, S = 1.146 and wR(F²) = 0.0745, R = 0.0301, S = 1.065, respectively. The N₂C—N—N backbone of the 2+ cation is close to planarity, while that of the 1+ cation does not differ significantly from planarity. The SiF octahedron is nearly ideally regular in both materials, with <Si—F> = 1.684 (unbiassed estimator of standard uncertainty = 0.016) Å in the anhydrous hexafluorosilicate and 1.6801 (unbiassed estimator of standard uncertainty = 0.0006) Å in the dihydrate. The combination of coulombic and NH...F interactions in CH₈N₄SiF₆ results in a relatively dense variant of the NaCl structure. In addition to similar forces, the dihydrate is also characterized by the role of the water molecule with its strong NH...O interactions; its packing efficiency is, however, appreciably less than that of the anhydrous hexafluorosilicate with an ∼8% increase in void space. Cleaved crystals of the dihydrate are frequently twinned across the (001) composition plane, with a twofold rotation about the b axis as the twin operation.

Computing details

For both compounds, data collection: CAD-4 EXPRESS (Enraf-Nonius, 1988); cell refinement: CAD-4 EXPRESS (Enraf-Nonius, 1988); data reduction: XCAD4 (Harms, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DRAWXTL (Finger and Kroeker, 1997), ORTEP-III (Burnett and Johnson, 1996).

Figures

(anhydrous) aminoguanidinium(2+) hexafluorosilicate

Crystal data

CH8N4·F6Si	F(000) = 880
Mr = 218.20	Dx = 2.089 Mg m^−3 Dm = 2.11 (3) Mg m^−3 Dm measured by pycnometry
Orthorhombic, Pccn	Cu Kα radiation, λ = 1.54180 Å
Hall symbol: -P 2ab 2ac	Cell parameters from 24 reflections
a = 10.4232 (1) Å	θ = 42.5–47.5°
b = 17.6675 (2) Å	µ = 3.89 mm^−1
c = 7.5363 (1) Å	T = 293 K
V = 1387.82 (3) Å^3	Blocky, colorless, clear
Z = 8	0.29 × 0.17 × 0.16 mm

Data collection

MACH3 diffractometer	1267 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.019
Graphite monochromator	θmax = 69.7°, θmin = 4.9°
ω – 2θ scan	h = −12→12
Absorption correction: analytical using ABSPSI - Alcock, N.W. and Marks, P.J. (1994). J. Appl. Cryst. 27, 200	k = −1→21
Tmin = 0.415, Tmax = 0.595	l = −1→9
3143 measured reflections	3 standard reflections every 60 min
1315 independent reflections	intensity decay: 7%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.026	All H-atom parameters refined
wR(F^2) = 0.065	Calculated w = 1/[σ^2(Fo^2) + (0.034P)^2 + 0.4906P] where P = (Fo^2 + 2Fc^2)/3
S = 1.15	(Δ/σ)max = 0.001
1315 reflections	Δρmax = 0.22 e Å^−3
142 parameters	Δρmin = −0.31 e Å^−3
0 restraints	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0076 (4)

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Si	0.45067 (3)	0.36631 (2)	0.61337 (5)	0.01893 (15)
F1	0.53956 (8)	0.42962 (5)	0.72439 (12)	0.0304 (2)
F2	0.39434 (9)	0.43412 (5)	0.48043 (12)	0.0324 (2)
F3	0.32849 (8)	0.38265 (6)	0.75852 (12)	0.0357 (2)
F4	0.50423 (9)	0.29678 (5)	0.75149 (12)	0.0357 (2)
F5	0.35997 (8)	0.30235 (5)	0.50833 (11)	0.0311 (2)
F6	0.57320 (9)	0.34800 (6)	0.47477 (12)	0.0376 (3)
C	0.61530 (13)	0.40105 (8)	0.10974 (18)	0.0236 (3)
N1	0.66326 (14)	0.33835 (8)	0.0451 (2)	0.0353 (3)
H1A	0.744 (3)	0.3375 (13)	0.028 (3)	0.051 (6)*
H1B	0.617 (3)	0.3107 (16)	−0.008 (4)	0.074 (8)*
N2	0.68857 (15)	0.45801 (9)	0.1506 (3)	0.0457 (4)
H2A	0.773 (3)	0.4530 (13)	0.133 (3)	0.055 (6)*
H2B	0.657 (2)	0.4968 (15)	0.181 (3)	0.055 (7)*
N3	0.48640 (12)	0.40978 (7)	0.13244 (17)	0.0236 (3)
H3	0.4682 (18)	0.4359 (11)	0.206 (3)	0.030 (5)*
N4	0.40871 (12)	0.34376 (7)	0.12861 (19)	0.0258 (3)
H4A	0.396 (2)	0.3328 (12)	0.025 (3)	0.042 (6)*
H4B	0.332 (2)	0.3565 (13)	0.173 (3)	0.052 (6)*
H4C	0.441 (2)	0.3017 (14)	0.186 (3)	0.057 (6)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Si	0.0159 (2)	0.0211 (2)	0.0198 (2)	−0.00130 (13)	0.00007 (12)	0.00067 (12)
F1	0.0303 (4)	0.0288 (4)	0.0322 (5)	−0.0101 (3)	−0.0057 (3)	−0.0001 (3)
F2	0.0338 (5)	0.0288 (4)	0.0347 (5)	0.0043 (4)	−0.0062 (4)	0.0060 (3)
F3	0.0246 (4)	0.0508 (5)	0.0318 (5)	−0.0060 (4)	0.0101 (4)	−0.0084 (4)
F4	0.0447 (5)	0.0269 (5)	0.0356 (5)	−0.0031 (4)	−0.0162 (4)	0.0071 (4)
F5	0.0303 (5)	0.0287 (4)	0.0342 (5)	−0.0045 (3)	−0.0092 (4)	−0.0046 (3)
F6	0.0219 (4)	0.0586 (6)	0.0323 (5)	0.0075 (4)	0.0049 (4)	−0.0032 (4)
C	0.0201 (6)	0.0266 (7)	0.0241 (7)	0.0000 (5)	−0.0012 (5)	0.0001 (5)
N1	0.0189 (6)	0.0376 (7)	0.0494 (9)	0.0000 (5)	0.0018 (6)	−0.0158 (6)
N2	0.0260 (8)	0.0304 (7)	0.0808 (12)	−0.0038 (6)	−0.0019 (7)	−0.0134 (7)
N3	0.0209 (6)	0.0229 (6)	0.0270 (6)	0.0013 (5)	0.0008 (5)	−0.0054 (5)
N4	0.0192 (6)	0.0287 (6)	0.0296 (7)	−0.0026 (5)	0.0006 (5)	0.0026 (5)

Geometric parameters (Å, º)

Si—F2	1.6684 (9)	N1—H1A	0.85 (3)
Si—F5	1.6727 (8)	N1—H1B	0.80 (3)
Si—F1	1.6761 (8)	N2—H2A	0.89 (3)
Si—F6	1.6813 (9)	N2—H2B	0.80 (3)
Si—F3	1.7034 (9)	N3—N4	1.4203 (17)
Si—F4	1.7043 (9)	N3—H3	0.74 (2)
C—N2	1.300 (2)	N4—H4A	0.82 (2)
C—N1	1.309 (2)	N4—H4B	0.90 (3)
C—N3	1.3632 (19)	N4—H4C	0.92 (3)
F2—Si—F5	90.11 (5)	N1—C—N3	121.25 (13)
F2—Si—F1	90.87 (5)	C—N1—H1A	116.7 (15)
F5—Si—F1	178.29 (5)	C—N1—H1B	118 (2)
F2—Si—F6	91.86 (5)	H1A—N1—H1B	121 (3)
F5—Si—F6	90.30 (5)	C—N2—H2A	117.8 (15)
F1—Si—F6	91.07 (5)	C—N2—H2B	119.2 (18)
F2—Si—F3	90.05 (5)	H2A—N2—H2B	123 (2)
F5—Si—F3	89.76 (5)	C—N3—N4	117.80 (12)
F1—Si—F3	88.84 (5)	C—N3—H3	114.5 (15)
F6—Si—F3	178.09 (5)	N4—N3—H3	112.2 (15)
F2—Si—F4	178.48 (5)	N3—N4—H4A	107.8 (15)
F5—Si—F4	89.26 (4)	N3—N4—H4B	107.3 (14)
F1—Si—F4	89.72 (5)	H4A—N4—H4B	106 (2)
F6—Si—F4	89.53 (5)	N3—N4—H4C	116.4 (15)
F3—Si—F4	88.56 (5)	H4A—N4—H4C	109 (2)
N2—C—N1	121.24 (14)	H4B—N4—H4C	111 (2)
N2—C—N3	117.48 (14)

(hydrous) diaminoguanidinium hexafluorosilicate dihydrate

Crystal data

2(CH7N4)·F6Si·2(H2O)	Z = 1
Mr = 328.33	F(000) = 170
Triclinic, P1	Dx = 1.666 Mg m^−3 Dm = 1.67 (1) Mg m^−3 Dm measured by pycnometry
a = 6.5124 (1) Å	Cu Kα radiation, λ = 1.54180 Å
b = 6.6952 (2) Å	Cell parameters from 25 reflections
c = 8.0215 (3) Å	θ = 42.5–47.5°
α = 70.723 (2)°	µ = 2.49 mm^−1
β = 82.745 (2)°	T = 293 K
γ = 89.243 (3)°	Prismatic, colorless, clear
V = 327.35 (2) Å^3	0.35 × 0.31 × 0.17 mm

Data collection

MACH3 diffractometer	1224 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.027
Graphite monochromator	θmax = 69.8°, θmin = 5.9°
ω – 2θ scans	h = −7→7
Absorption correction: analytical ?	k = −8→8
Tmin = 0.45, Tmax = 0.61	l = −9→9
2404 measured reflections	3 standard reflections every 60 min
1239 independent reflections	intensity decay: 5%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.030	All H-atom parameters refined
wR(F^2) = 0.075	Calculated w = 1/[σ^2(Fo^2) + (0.0295P)^2 + 0.1278P] where P = (Fo^2 + 2Fc^2)/3
S = 1.07	(Δ/σ)max = 0.001
1239 reflections	Δρmax = 0.28 e Å^−3
125 parameters	Δρmin = −0.22 e Å^−3
0 restraints	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.043 (4)

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes)

are estimated using the full covariance matrix. The cell e.s.d.'s are taken

into account individually in the estimation of e.s.d.'s in distances, angles

and torsion angles; correlations between e.s.d.'s in cell parameters are only

used when they are defined by crystal symmetry. An approximate (isotropic)

treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and

goodness of fit S are based on F², conventional R-factors R are based

on F, with F set to zero for negative F². The threshold expression of

F² > σ(F²) is used only for calculating R-factors(gt) etc. and is

not relevant to the choice of reflections for refinement. R-factors based

on F² are statistically about twice as large as those based on F, and R-

factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Si	0.0000	0.0000	0.0000	0.0310 (2)
F1	0.04859 (14)	−0.01478 (16)	0.20441 (12)	0.0478 (3)
F2	0.12778 (16)	0.23518 (15)	−0.08741 (14)	0.0543 (3)
F3	−0.22230 (14)	0.12017 (16)	0.03280 (13)	0.0531 (3)
C	0.4773 (2)	0.2381 (2)	0.5241 (2)	0.0344 (3)
N1	0.5514 (2)	0.1627 (2)	0.67681 (19)	0.0442 (3)
H1A	0.465 (3)	0.116 (3)	0.777 (3)	0.046 (5)*
H1B	0.671 (3)	0.151 (3)	0.679 (2)	0.037 (5)*
N2	0.2754 (2)	0.2442 (3)	0.5163 (2)	0.0461 (4)
H2A	0.182 (3)	0.193 (3)	0.610 (3)	0.054 (5)*
H2B	0.235 (3)	0.294 (3)	0.417 (3)	0.045 (5)*
N3	0.6031 (2)	0.3118 (2)	0.37175 (19)	0.0408 (3)
H3	0.552 (3)	0.357 (3)	0.277 (3)	0.044 (5)*
N4	0.8184 (2)	0.3098 (2)	0.3732 (2)	0.0430 (3)
H4A	0.867 (3)	0.443 (4)	0.314 (3)	0.058 (6)*
H4B	0.862 (3)	0.227 (4)	0.317 (3)	0.059 (6)*
O	0.7298 (2)	0.5611 (3)	0.86215 (19)	0.0541 (4)
H1W	0.749 (4)	0.442 (5)	0.912 (4)	0.077 (8)*
H2W	0.769 (4)	0.622 (4)	0.919 (4)	0.081 (9)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Si	0.0282 (3)	0.0355 (3)	0.0253 (3)	0.0007 (2)	0.00041 (19)	−0.0063 (2)
F1	0.0444 (5)	0.0667 (6)	0.0305 (5)	−0.0002 (4)	−0.0050 (4)	−0.0136 (4)
F2	0.0635 (7)	0.0458 (6)	0.0461 (6)	−0.0167 (5)	0.0049 (5)	−0.0090 (4)
F3	0.0410 (5)	0.0629 (6)	0.0488 (6)	0.0166 (4)	0.0012 (4)	−0.0129 (5)
C	0.0333 (7)	0.0319 (7)	0.0361 (8)	0.0001 (5)	0.0005 (6)	−0.0105 (6)
N1	0.0344 (8)	0.0562 (8)	0.0351 (8)	0.0029 (6)	−0.0005 (6)	−0.0075 (6)
N2	0.0320 (7)	0.0609 (9)	0.0390 (8)	−0.0019 (6)	−0.0001 (6)	−0.0094 (7)
N3	0.0331 (7)	0.0508 (8)	0.0334 (7)	−0.0020 (5)	−0.0004 (5)	−0.0083 (6)
N4	0.0313 (7)	0.0450 (8)	0.0484 (8)	−0.0014 (6)	0.0042 (6)	−0.0130 (7)
O	0.0634 (8)	0.0494 (8)	0.0497 (8)	0.0016 (6)	−0.0169 (6)	−0.0131 (6)

Geometric parameters (Å, º)

Si—F1	1.6797 (9)	N1—H1B	0.781 (19)
Si—F1^i	1.6797 (9)	N2—H2A	0.88 (2)
Si—F2	1.6798 (9)	N2—H2B	0.83 (2)
Si—F2^i	1.6798 (9)	N3—N4	1.4037 (19)
Si—F3^i	1.6808 (9)	N3—H3	0.83 (2)
Si—F3	1.6808 (9)	N4—H4A	0.90 (2)
C—N1	1.313 (2)	N4—H4B	0.85 (2)
C—N2	1.324 (2)	O—H1W	0.78 (3)
C—N3	1.329 (2)	O—H2W	0.77 (3)
N1—H1A	0.89 (2)
F1—Si—F1^i	180.0	N1—C—N3	120.98 (14)
F1—Si—F2	90.35 (5)	N2—C—N3	117.75 (15)
F1^i—Si—F2	89.65 (5)	C—N1—H1A	119.6 (12)
F1—Si—F2^i	89.65 (5)	C—N1—H1B	120.4 (13)
F1^i—Si—F2^i	90.35 (5)	H1A—N1—H1B	119.8 (19)
F2—Si—F2^i	180.0	C—N2—H2A	123.3 (14)
F1—Si—F3^i	90.74 (5)	C—N2—H2B	118.3 (14)
F1^i—Si—F3^i	89.26 (5)	H2A—N2—H2B	118.3 (19)
F2—Si—F3^i	89.24 (5)	C—N3—N4	119.85 (14)
F2^i—Si—F3^i	90.76 (5)	C—N3—H3	119.0 (13)
F1—Si—F3	89.26 (5)	N4—N3—H3	121.1 (13)
F1^i—Si—F3	90.74 (5)	N3—N4—H4A	106.8 (13)
F2—Si—F3	90.76 (5)	N3—N4—H4B	105.1 (15)
F2^i—Si—F3	89.24 (5)	H4A—N4—H4B	111 (2)
F3^i—Si—F3	180.0	H1W—O—H2W	105 (3)
N1—C—N2	121.27 (15)

Symmetry code: (i) −x, −y, −z.