Low-temperature crystallization and structure determination of N-(trifluoromethyl)formamide, N-(2,2,2-trifluoroethyl)formamide and 2,2,2-trifluoroethyl isocyanide

Crystals of N-(trifluoromethyl)formamide, C₂H₂F₃NO, (I), N-(2,2,2-trifluoroethyl)formamide, C₃H₄F₃NO, (II), and 2,2,2-trifluoroethyl isocyanide, C₃H₂F₃N, (III), were grown in situ on an X-ray diffractometer and analysed by single-crystal X-ray diffraction methods at low temperatures. Crystal data: (I) orthorhombic, P2₁2₁2₁, a = 4.547 (2) Å, b = 5.947 (3) Å, c = 14.731 (9) Å, V = 398.3 (4) ų, Z = 4, M_r = 113.05, T = 143 K, D_x = 1.885 Mg m⁻³; (II) monoclinic, P2₁/n, a = 4.807 (1) Å, b = 16.707 (3) Å, c = 6.708 (1) Å, β = 109.90 (1)°, V = 506.6 (2) ų, Z = 4, M_r = 127.07, T = 141 K, D_x = 1.666 Mg m⁻³; (III) orthorhombic, P2₁2₁2₁, a = 5.668 (2) Å, b = 9.266 (3) Å, c = 8.626 (2) Å, V = 453.0 (2) ų, Z = 4, M_r = 109.06, T = 163 K, D_x = 1.599 Mg m⁻³. The results showed that in the crystal both formamides (I) and (II) are exclusively present in the form of the Z isomer, although measurements of solutions of (I) have shown that the E isomer prevails [Lentz et al. (1987). Angew. Chem. 99, 951–953]. In addition ab initio calculations for (I) predicted the E isomer to be the more stable one. In compound (III) the isocyanide group is staggered with respect to the trifluoroethyl group. In the crystal packing of (I) and (II) intermolecular N—HO hydrogen bonds generate infinite chains. In (I), these chains are linked to form sheets by C—HO contacts. In the crystal structure of (III) each isocyanide dipole is surrounded by four electronegative F atoms with intermolecular CF contacts between 3.4 and 3.5 Å.

Computing details

For all compounds, data collection: Siemens software; cell refinement: Siemens software; data reduction: in-house program; program(s) used to solve structure: SHELXS86 (Sheldrick, 1990). Program(s) used to refine structure: SHELXL97 (Sheldrick, 1997) for (I); SHELXL93 (Sheldrick, 1993) for (II), (III).

Figures

(I) N-trifluoromethyl formamide

Crystal data

C2H2F3NO	Z = 4
Mr = 113.05	F(000) = 224
Orthorhombic, P212121	Dx = 1.885 Mg m^−3
a = 4.547 (2) Å	Mo Kα radiation, λ = 0.71068 Å
b = 5.947 (3) Å	µ = 0.23 mm^−1
c = 14.731 (9) Å	T = 143 K
V = 398.3 (4) Å^3	Cylinder with diameter 0.5 mm

Data collection

Siemens four circle diffractometer, N2 gas stream cooled	779 reflections with I > 2σ(I)
Radiation source: fine-focus x-ray tube	Rint = 0.050
None monochromator	θmax = 30.0°, θmin = 2.8°
ω/2θ scans	h = 0→6
Absorption correction: no	k = −8→8
	l = −20→20
2446 measured reflections	4 standard reflections every 90 min
1170 independent reflections	intensity decay: 4%

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)] = 0.070	Calculated w = 1/[σ^2(Fo^2) + (0.0749P)^2 + 0.5432P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.226	(Δ/σ)max = 0.086
S = 1.11	Δρmax = 0.40 e Å^−3
1170 reflections	Δρmin = −0.39 e Å^−3
70 parameters	Absolute structure: Flack H D (1983), Acta Cryst. A39, 876-881
2 restraints	Absolute structure parameter: −2.88 (2.96)
Primary atom site location: structure-invariant direct methods

Special details

Experimental. Nb filtered

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
O1	1.0942 (7)	0.5366 (6)	0.4321 (3)	0.029 (1)
C1	0.8260 (9)	0.5368 (8)	0.4309 (3)	0.025 (1)
H1	0.70 (2)	0.66 (1)	0.46 (1)	0.030*
N2	0.6592 (8)	0.3786 (6)	0.3883 (3)	0.026 (1)
H2	0.45 (2)	0.38 (1)	0.39 (1)	0.031*
C3	0.7820 (9)	0.1974 (7)	0.3408 (3)	0.026 (1)
F1	0.9606 (7)	0.0725 (4)	0.3916 (2)	0.034 (1)
F2	0.9435 (9)	0.2611 (5)	0.2699 (2)	0.040 (1)
F3	0.5689 (7)	0.0657 (6)	0.3109 (3)	0.060 (1)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0183 (14)	0.0292 (14)	0.0395 (16)	0.0008 (12)	−0.0028 (13)	−0.0073 (13)
C1	0.0213 (18)	0.0233 (18)	0.0311 (19)	0.0034 (15)	−0.0004 (18)	−0.0024 (16)
N2	0.0141 (13)	0.0290 (16)	0.0350 (19)	0.0019 (13)	−0.0002 (15)	−0.0073 (15)
C3	0.0179 (18)	0.0278 (19)	0.033 (2)	0.0026 (15)	0.0001 (16)	−0.0059 (16)
F1	0.0400 (15)	0.0279 (12)	0.0351 (13)	0.0117 (12)	−0.0002 (13)	0.0033 (10)
F2	0.055 (2)	0.0333 (13)	0.0308 (13)	0.0089 (14)	0.0168 (14)	0.0006 (11)
F3	0.0249 (14)	0.054 (2)	0.099 (3)	−0.0030 (15)	−0.0078 (19)	−0.047 (2)

Geometric parameters (Å, º)

O1—C1	1.219 (5)	N2—H2	0.96 (7)
C1—N2	1.366 (6)	C3—F3	1.320 (5)
C1—H1	1.01 (6)	C3—F1	1.332 (5)
N2—C3	1.402 (5)	C3—F2	1.330 (5)
O1—C1—N2	124.0 (5)	F3—C3—F1	107.7 (4)
O1—C1—H1	124 (4)	F3—C3—F2	108.2 (4)
N2—C1—H1	112 (4)	F1—C3—F2	105.3 (4)
C1—N2—C3	122.6 (4)	F3—C3—N2	109.2 (4)
C1—N2—H2	125 (3)	F1—C3—N2	113.0 (4)
C3—N2—H2	112 (3)	F2—C3—N2	113.2 (4)
O1—C1—N2—C3	0.3 (8)	C1—N2—C3—F1	56.6 (6)
C1—N2—C3—F3	176.5 (5)	C1—N2—C3—F2	−62.9 (6)

(II)

Crystal data

C3H4F3NO	Z = 4
Mr = 127.07	F(000) = 256
Monoclinic, P21/n	Dx = 1.666 Mg m^−3
a = 4.807 (1) Å	Mo Kα radiation, λ = 0.71068 Å
b = 16.707 (3) Å	µ = 0.19 mm^−1
c = 6.708 (1) Å	T = 141 K
β = 109.90 (1)°	Cylinder with diameter 0.5 mm
V = 506.6 (2) Å^3

Data collection

Siemens four circle diffractometer, N2 gas stream cooled	1018 reflections with I > 2σ(I)
Radiation source: fine-focus x-ray tube	Rint = 0.031
None monochromator	θmax = 30.1°, θmin = 2.4°
ω/2θ scans	h = −6→4
Absorption correction: no	k = −23→19
	l = −9→9
2983 measured reflections	3 standard reflections every 90 min
1484 independent reflections	intensity decay: 4%

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.051	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.140	Calculated w = 1/[σ^2(Fo^2) + (0.0587P)^2 + 0.2157P] where P = (Fo^2 + 2Fc^2)/3
S = 1.09	(Δ/σ)max = 0.043
1484 reflections	Δρmax = 0.30 e Å^−3
89 parameters	Δρmin = −0.29 e Å^−3
0 restraints

Special details

Experimental. Nb filtered

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 on F² for ALL reflections except for 0 with very negative F²=

or flagged by the user for potential systematic errors. Weighted R-factors=

wR and all goodnesses of fit S are based on F², conventional R-factors R=

are based on F, with F set to zero for negative F². The observed= criterion of F² > σ(F²) is used only for calculating _R_factor_obs 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
O1	1.0908 (3)	0.2117 (1)	0.3539 (2)	0.027 (1)
C1	0.9939 (4)	0.2445 (1)	0.4805 (3)	0.021 (1)
H1	1.016 (6)	0.298 (2)	0.509 (4)	0.027 (6)*
N2	0.8317 (3)	0.2082 (1)	0.5793 (2)	0.022 (1)
H2	0.766 (5)	0.235 (1)	0.666 (4)	0.013 (5)*
C3	0.7452 (4)	0.1256 (1)	0.5396 (3)	0.023 (1)
H31	0.780 (7)	0.108 (2)	0.411 (5)	0.034 (7)*
H32	0.550 (7)	0.121 (2)	0.524 (5)	0.041 (8)*
C4	0.9133 (4)	0.0737 (1)	0.7229 (3)	0.026 (1)
F1	1.2041 (3)	0.0744 (1)	0.7593 (2)	0.040 (1)
F2	0.8787 (4)	0.0967 (1)	0.9037 (2)	0.041 (1)
F3	0.8245 (4)	−0.0020 (1)	0.6893 (3)	0.042 (1)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0278 (6)	0.0326 (7)	0.0256 (6)	0.0004 (5)	0.0153 (5)	0.0029 (5)
C1	0.0194 (7)	0.0233 (8)	0.0202 (7)	0.0009 (6)	0.0053 (5)	0.0032 (6)
N2	0.0247 (7)	0.0225 (7)	0.0214 (6)	0.0007 (6)	0.0120 (5)	−0.0006 (5)
C3	0.0216 (8)	0.0245 (8)	0.0241 (7)	−0.0016 (6)	0.0086 (6)	0.0011 (6)
C4	0.0263 (8)	0.0245 (9)	0.0285 (8)	−0.0001 (7)	0.0107 (6)	0.0015 (7)
F1	0.0251 (6)	0.0457 (8)	0.0466 (7)	0.0078 (5)	0.0088 (5)	0.0054 (6)
F2	0.0547 (8)	0.0449 (8)	0.0266 (6)	0.0094 (6)	0.0193 (5)	0.0080 (5)
F3	0.0517 (8)	0.0250 (6)	0.0480 (8)	−0.0037 (6)	0.0130 (6)	0.0068 (5)

Geometric parameters (Å, º)

O1—C1	1.228 (2)	C3—H31	0.98 (3)
C1—N2	1.329 (2)	C3—H32	0.91 (3)
C1—H1	0.90 (3)	C4—F3	1.329 (2)
N2—C3	1.440 (2)	C4—F1	1.334 (2)
N2—H2	0.86 (2)	C4—F2	1.335 (2)
C3—C4	1.498 (3)
O1—C1—N2	124.5 (2)	C4—C3—H31	109 (2)
O1—C1—H1	123 (2)	C4—C3—H32	107 (2)
N2—C1—H1	113 (2)	H31—C3—H32	110 (3)
C1—N2—C3	121.7 (2)	F3—C4—F1	107.2 (2)
C1—N2—H2	120 (2)	F3—C4—F2	107.2 (2)
C3—N2—H2	118 (2)	F1—C4—F2	106.1 (2)
N2—C3—C4	111 (2)	F3—C4—C3	111.0 (2)
N2—C3—H31	110 (2)	F1—C4—C3	112.6 (2)
N2—C3—H32	109 (2)	F2—C4—C3	112.3 (2)
O1—C1—N2—C3	−2.2 (3)	N2—C3—C4—F1	−62.3 (2)
C1—N2—C3—C4	107.5 (2)	N2—C3—C4—F2	57.4 (2)
N2—C3—C4—F3	177.5 (2)

(III) 2,2,2-trifluoroethyl isocyanide

Crystal data

C3H2F3N	Z = 4
Mr = 109.06	F(000) = 216
Orthorhombic, P212121	Dx = 1.599 Mg m^−3
a = 5.668 (2) Å	Mo Kα radiation, λ = 0.71068 Å
b = 9.266 (3) Å	µ = 0.19 mm^−1
c = 8.626 (2) Å	T = 163 K
V = 453.0 (2) Å^3	Cylinder with diameter 0.5 mm

Data collection

Siemens four circle diffractometer, N2 gas stream cooled	1092 reflections with I > 2σ(I)
Radiation source: fine-focus x-ray tube	Rint = 0.022
None monochromator	θmax = 35.0°, θmin = 3.2°
ω/2θ scans	h = −4→9
Absorption correction: no	k = −14→14
	l = −11→13
1856 measured reflections	4 standard reflections every 90 min
1556 independent reflections	intensity decay: 58%

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)] = 0.033	Calculated w = 1/[σ^2(Fo^2) + (0.0452P)^2 + 0.0656P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.098	(Δ/σ)max = 0.006
S = 1.01	Δρmax = 0.22 e Å^−3
1556 reflections	Δρmin = −0.14 e Å^−3
72 parameters	Absolute structure: Flack H D (1983), Acta Cryst. A39, 876-881
0 restraints	Absolute structure parameter: −0.18 (91)
Primary atom site location: structure-invariant direct methods

Special details

Experimental. Nb filtered

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 on F² for ALL reflections except for 0 with very negative F²=

or flagged by the user for potential systematic errors. Weighted R-factors=

wR and all goodnesses of fit S are based on F², conventional R-factors R=

are based on F, with F set to zero for negative F². The observed= criterion of F² > σ(F²) is used only for calculating _R_factor_obs 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
C1	−0.0245 (3)	0.2436 (2)	−0.1439 (2)	0.054 (1)
N2	0.0359 (2)	0.1328 (1)	−0.1005 (1)	0.042 (1)
C3	0.1126 (3)	−0.0044 (2)	−0.0460 (2)	0.042 (1)
H31	0.276 (4)	0.000 (2)	−0.0088 (2)	0.051 (5)*
H32	0.103 (4)	−0.074 (2)	−0.127 (2)	0.057 (5)*
C4	−0.0476 (3)	−0.0568 (2)	0.0807 (1)	0.039 (1)
F1	−0.0465 (2)	0.0293 (1)	0.2027 (1)	0.056 (1)
F2	−0.2697 (2)	−0.0675 (1)	0.0346 (1)	0.058 (1)
F3	0.0198 (3)	−0.1866 (1)	0.1278 (1)	0.073 (1)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0529 (9)	0.0510 (8)	0.0585 (8)	−0.0088 (8)	−0.0054 (8)	0.0125 (7)
N2	0.0452 (6)	0.0430 (6)	0.0374 (5)	−0.0077 (6)	0.0001 (5)	0.0016 (5)
C3	0.0480 (9)	0.0386 (6)	0.0405 (6)	0.0056 (6)	0.0056 (6)	−0.0051 (6)
C4	0.0469 (7)	0.0349 (6)	0.0365 (6)	0.0052 (6)	−0.0027 (5)	−0.0014 (5)
F1	0.0679 (6)	0.0661 (6)	0.0348 (4)	−0.0029 (5)	0.0026 (4)	−0.0135 (4)
F2	0.0498 (5)	0.0660 (6)	0.0588 (5)	−0.0174 (5)	−0.0069 (4)	0.0055 (5)
F3	0.0943 (9)	0.0471 (5)	0.0775 (7)	0.0210 (6)	0.0154 (7)	0.0229 (5)

Geometric parameters (Å, º)

C1—N2	1.145 (2)	C3—H32	0.95 (2)
N2—C3	1.424 (2)	C4—F1	1.321 (2)
C3—C4	1.502 (2)	C4—F2	1.324 (2)
C3—H31	0.98 (2)	C4—F3	1.326 (2)
C1—N2—C3	179.5 (2)	F1—C4—C3	112.5 (1)
N2—C3—C4	110.1 (1)	F2—C4—C3	112.4 (1)
N2—C3—H31	111 (1)	F3—C4—C3	110.0 (1)
N2—C3—H32	110 (1)	F2—C4—F3	107.3 (1)
C4—C3—H31	110 (1)	F1—C4—F3	107.6 (1)
C4—C3—H32	107 (1)	F1—C4—F2	106.8 (1)
H31—C3—H32	109 (2)
C1—N2—C3—C4	111 (19)	N2—C3—C4—F2	58.5 (2)
N2—C3—C4—F1	−62.1 (2)	N2—C3—C4—F3	178.0 (1)