Bis(ethyl­amino)tetra­fluoro­silicon

The title compound, SiF₄(NH₂Et)₂ or C₄H₁₄F₄N₂Si, was isolated as an inter­mediate in the attempted solvothermal synthesis of a nitride-containing microporous material. Its structure at 150 K displays inter­molecular hydrogen bonding leading to infinite sheets of mol­ecules (each of point symmetry) running parallel to the bc plane.

Key indicators

• Single-crystal X-ray study
• T = 150 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.034
• wR factor = 0.042
• Data-to-parameter ratio = 11.2

checkCIF/PLATON results

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Datablock: I


Alert level B
PLAT110_ALERT_2_B ADDSYM Detects Potential Lattice Centering or Halving .   ?

Alert level C
PLAT241_ALERT_2_C Check High      Ueq as Compared to Neighbors for         C1
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for         N1
PLAT250_ALERT_2_C Large U3/U1 Ratio for Average U(i,j) Tensor ....       2.01

   0 ALERT level A = In general: serious problem
   1 ALERT level B = Potentially serious problem
   3 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   4 ALERT type 2 Indicator that the structure model may be wrong or deficient
   0 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

The molecule is located on a centre of symmetry (Fig. 1). Intramolecular hydrogen bonds (N—H···F) link the molecules to form infinite sheets running parallel to the bc plane (Fig. 2). A third relatively short interaction (N1···F1 3.054 (2) Å) is apparently not a hydrogen bond and the largest N—H···F angle is ca 130°. The secondary C atom C1 has relatively large displacement parameters compared to its neighbours, suggesting that there may be some unresolved disorder of the ethyl group. Related adducts of silicon tetrafluoride are described in Ennan & Kats (1974).

Related literature

For related literature, see: Ennan & Kats (1974).

S2. Experimental

All manipulations were carried out in the absence of atmospheric oxygen or moisture in either an Aldrich glove bag or using standard Schlenk line techniques and house nitrogen. Starting materials were obtained from Aldrich and Et₃N was dried over 3 Å molecular sieves. 1.5996 g Si₃N₄, 1.27 ml Et₃N.3HF and 7 ml Et₃N (molar ratio 1 Si: 1 F: 12 Et₃N) were combined and stirred to homogeneity. The mixture was placed inside a 25 ml teflon-lined autoclave and heated for 12 days at 240 °C. The autoclave was then cooled by removal from the oven and the mixture washed with dry Et₃N and dried under vacuum. Products were stored in a Glovebox Technology argon-filled dry box. Powder X-ray diffraction showed Si₃N₄ and SiF₄(NHEt₂)₂ to be the major phases, with SiF₄(NH₂Et)₂ corresponding to approximately 15% of the product by reference to the observed intensities.

S3. Refinement

The NH hydrogen atoms were located in a difference Fourier map and their coordinates and isotropic displacement parameters subsequently refined. Other hydrogen atoms were positioned geometrically after each cycle of refinement. Examination of the packing of the structure shows that there are additional pseudosymmetry operators which would correspond to the (non-standard) space group A2/a, but in order to adopt this symmetry all atoms other than Si would be required to be disordered. Examination of the original intensity data clearly shows no absences indicative of the A-centring, confirming the original symmetry assignment.

Computing details

Data collection: KappaCCD Server Software (Nonius, 1997); cell refinement: DENZO; data reduction: DENZO (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: ATOMS (Dowty, 2005); software used to prepare material for publication: CRYSTALS.

Figures

	Fig. 1. Molecular structure of the title compound. Displacement ellipsoids are drawn at the 40% probability level.
	Fig. 2. Packing diagram as viewed down the b axis, showing the formation of infinite sheets via H-bonding. Displacement ellipsoids are for Si (pink), F (green), N (blue), C (white), Hydrogen atoms are shown as small white spheres. Intermolecular hydrogen bonds are indicated by dashed lines.

bis(ethylamine)tetrafluorosilicon

Crystal data

C4H14F4N2Si	F(000) = 204
Mr = 194.25	Dx = 1.536 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 4140 reflections
a = 8.4788 (4) Å	θ = 5–28°
b = 6.9602 (3) Å	µ = 0.29 mm^−1
c = 7.2206 (4) Å	T = 150 K
β = 99.655 (2)°	Plate, colourless
V = 420.08 (4) Å^3	0.24 × 0.20 × 0.05 mm
Z = 2

Data collection

Nonius KappaCCD area-detector diffractometer	670 reflections with I > 3σ(I)
Graphite monochromator	Rint = 0.042
ω scans	θmax = 27.5°, θmin = 5.7°
Absorption correction: multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997)	h = −10→10
Tmin = 0.93, Tmax = 0.99	k = −8→8
4140 measured reflections	l = −9→9
946 independent reflections

Refinement

Refinement on F	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.034	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.042	Method, part 1, Chebychev polynomial, (Watkin, 1994, Prince, 1982) [weight] = 1.0/[A0*T0(x) + A1*T1(x) ··· + An-1]*Tn-1(x)] where Ai are the Chebychev coefficients listed below and x = F /Fmax Method = Robust Weighting (Prince, 1982) W = [weight] * [1-(deltaF/6*sigmaF)^2]^2 Ai are: 1.21 0.411 0.931
S = 1.07	(Δ/σ)max = 0.001
670 reflections	Δρmax = 0.24 e Å^−3
60 parameters	Δρmin = −0.31 e Å^−3
0 restraints

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

	x	y	z	Uiso*/Ueq
Si1	0.5000	0.5000	0.5000	0.0222
F1	0.54851 (14)	0.26642 (17)	0.51774 (15)	0.0295
F2	0.65474 (14)	0.55391 (18)	0.66675 (15)	0.0293
N1	0.6294 (2)	0.5299 (3)	0.3080 (2)	0.0254
C1	0.7992 (3)	0.4765 (6)	0.3436 (4)	0.0634
C2	0.8842 (3)	0.5125 (4)	0.1797 (4)	0.0452
H1	0.595 (4)	0.463 (4)	0.219 (5)	0.042 (8)*
H2	0.622 (3)	0.638 (5)	0.266 (4)	0.038 (7)*
H11	0.8538	0.5527	0.4533	0.0774*
H12	0.8073	0.3365	0.3748	0.0774*
H21	0.9988	0.4730	0.2139	0.0559*
H22	0.8783	0.6524	0.1475	0.0559*
H23	0.8319	0.4361	0.0690	0.0559*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Si1	0.0300 (4)	0.0208 (4)	0.0167 (3)	0.0004 (3)	0.0061 (2)	−0.0001 (3)
F1	0.0445 (7)	0.0213 (6)	0.0249 (5)	0.0039 (5)	0.0124 (4)	0.0028 (4)
F2	0.0316 (6)	0.0361 (7)	0.0200 (6)	−0.0021 (5)	0.0035 (4)	−0.0027 (5)
N1	0.0337 (9)	0.0229 (10)	0.0206 (8)	0.0002 (7)	0.0073 (6)	0.0010 (7)
C1	0.0404 (13)	0.117 (3)	0.0363 (13)	0.0222 (16)	0.0156 (10)	0.0181 (16)
C2	0.0438 (12)	0.0520 (15)	0.0439 (14)	−0.0004 (12)	0.0199 (10)	−0.0006 (11)

Geometric parameters (Å, º)

Si1—F1	1.6766 (12)	N1—H2	0.81 (3)
Si1—F1^i	1.6766 (12)	C1—C2	1.506 (3)
Si1—F2	1.6679 (11)	C1—H11	1.000
Si1—F2^i	1.6679 (11)	C1—H12	1.000
Si1—N1	1.9183 (17)	C2—H21	1.000
Si1—N1^i	1.9183 (17)	C2—H22	1.000
N1—C1	1.467 (3)	C2—H23	1.000
N1—H1	0.81 (3)
F1—Si1—F1^i	180	C1—N1—H1	102 (2)
F1—Si1—F2	90.56 (6)	Si1—N1—H2	111 (2)
F1^i—Si1—F2	89.44 (6)	C1—N1—H2	108 (2)
F1—Si1—F2^i	89.44 (6)	H1—N1—H2	104 (3)
F1^i—Si1—F2^i	90.56 (6)	N1—C1—C2	113.9 (2)
F2—Si1—F2^i	180	N1—C1—H11	108.357
F1—Si1—N1	89.86 (6)	C2—C1—H11	108.357
F1^i—Si1—N1	90.14 (6)	N1—C1—H12	108.357
F2—Si1—N1	91.23 (6)	C2—C1—H12	108.357
F2^i—Si1—N1	88.77 (6)	H11—C1—H12	109.467
F1—Si1—N1^i	90.14 (6)	C1—C2—H21	109.467
F1^i—Si1—N1^i	89.86 (6)	C1—C2—H22	109.467
F2—Si1—N1^i	88.77 (6)	H21—C2—H22	109.476
F2^i—Si1—N1^i	91.23 (6)	C1—C2—H23	109.467
N1—Si1—N1^i	180	H21—C2—H23	109.476
Si1—N1—C1	120.61 (15)	H22—C2—H23	109.476
Si1—N1—H1	110 (2)

Symmetry code: (i) −x+1, −y+1, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···F1^ii	0.81 (3)	2.15 (3)	2.938 (2)	165 (3)
N1—H2···F2^iii	0.81 (3)	2.29 (3)	3.091 (2)	168 (3)

Symmetry codes: (ii) x, −y+1/2, z−1/2; (iii) x, −y+3/2, z−1/2.