2,2,6,6-Tetra­methyl-4-oxopiperidinium tri­fluoro­acetate

Both ions of the title compound, C₉H₁₈NO⁺·CF₃CO₂^-, are located on a crystallographic mirror plane. The piperidone ring adopts an almost ideal chair conformation. The different ions form hydrogen-bonded chains, extending parallel to the crystallographic a axis.

Key indicators

• Single-crystal X-ray study
• T = 173 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.049
• wR factor = 0.141
• Data-to-parameter ratio = 12.1

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level C:



REFLT_03
         From the CIF: _diffrn_reflns_theta_max           25.16
         From the CIF: _reflns_number_total               1215
         TEST2: Reflns within _diffrn_reflns_theta_max
         Count of symmetry unique reflns         1281
         Completeness (_total/calc)             94.85%
          Alert C: < 95% complete


 0 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 1 Alert Level C = Please check

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S1. Comment

Piperdine derivates have found widespread use as bulky bases in organic chemistry. We report here the reaction of 2,2,6,6-tetramethyl-4-piperidone with trifluoroacetic acid and the X-ray crystal structure analysis of 2,2,6,6-tetramethyl-4-oxopiperidium trifluoroacetate, (I). The synthesis of (I) was achieved by transforming 2,2,6,6-tetramethyl-4-piperidone, as indicated in the Scheme below.

Both ions of (I) are located on a crystallographic mirror plane. Only the methyl groups and the sp³ C atoms of the piperidone ring and one of the F atoms are located on a general position. Bond lengths and angles are in the usual ranges. The piperidone ring adopts an almost ideal chair conformation, with Q = 0.525 (2) Å, θ = 176.2 (3)°, ϕ = 360 (3)° (Cremer & Pople, 1975). Anions and cations form infinite hydrogen-bonded chains along the crystallographic a axis.

S2. Experimental

The title compound was produced of 2 mmol 2,2,6,6-tetramethyl-4-piperidone in 5 ml CHCl₃ in the presence of 3 mmol trifluoroacetic acid at ambient temperature. Colourless crystals of (I) were grown by storing this solution at room temperature for 2 d. ¹H NMR (CDCl₃, internal TMS): δ 1.26 (s, 4 × CH₃), 2.34 (s, 2 × CH₂), 5.67 (s, br, NH₂). ¹³C{¹H} NMR (CDCl₃, internal TMS): δ 30.8 (s, CH₃), 52.7 (s, 2 CH₂), 56.8 (s, 2 × NCMe), 116.5 (q, CF₃, ¹J_FC = 292.8 Hz), 161.7 (q, CO₂, ²J_FC = 35.1 Hz).

S3. Refinement

H atoms bonded to C atoms were refined with fixed individual displacement parameters [U_iso(H) = 1.2U_eq(C) or 1.5 U_eq(C_methyl)] using a riding model, with C—H = 0.99 Å or methyl C—H = 0.98 Å. H atoms bonded to N atoms were refined isotropically.

Computing details

Data collection: X-AREA (Stoe & Cie, 2001); cell refinement: X-AREA; data reduction: X-AREA; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP in SHELXTL-Plus (Sheldrick, 1991).

Figures

	Fig. 1. Perspective view of the title compound with the atom numbering; displacement ellipsoids are at the 50% probability level. Symmetry operator for generating equivalent atoms: (i) x, −y + 3/2, z.
	Fig. 2. Packing of the title compound. View perpendicular to the ac plane. Only the H atoms bonded to N are shown. Atom codes: C shaded black circles, H small open green circles, F dotted green circles, N blue shaded circles, O cross-hatched red circles.

2,2,6,6-tetramethyl-4-piperidonium trifluoroacetate

Crystal data

C9H18NO^+·C2F3O2^−	F(000) = 284
Mr = 269.26	Dx = 1.332 Mg m^−3
Monoclinic, P21/m	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yb	Cell parameters from 3675 reflections
a = 6.6117 (14) Å	θ = 3.7–25.1°
b = 9.1388 (15) Å	µ = 0.12 mm^−1
c = 11.3024 (19) Å	T = 173 K
β = 100.450 (17)°	Block, colourless
V = 671.6 (2) Å^3	0.29 × 0.18 × 0.11 mm
Z = 2

Data collection

Stoe IPDS-II two-circle diffractometer	1215 independent reflections
Radiation source: fine-focus sealed tube	906 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.041
ω scans	θmax = 25.2°, θmin = 3.9°
Absorption correction: multi-scan (MULABS; Spek, 1990; Blessing, 1995)	h = −7→7
Tmin = 0.966, Tmax = 0.984	k = −10→10
3390 measured reflections	l = −12→13

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)] = 0.049	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.141	H atoms treated by a mixture of independent and constrained refinement
S = 1.05	w = 1/[σ^2(Fo^2) + (0.0836P)^2 + 0.1272P] where P = (Fo^2 + 2Fc^2)/3
1215 reflections	(Δ/σ)max < 0.001
100 parameters	Δρmax = 0.55 e Å^−3
0 restraints	Δρmin = −0.43 e Å^−3

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
N1	0.1327 (4)	0.7500	0.2166 (2)	0.0230 (6)
H1A	0.247 (6)	0.7500	0.185 (3)	0.031 (9)*
H1B	0.028 (6)	0.7500	0.152 (4)	0.035 (9)*
C2	0.1211 (3)	0.6051 (2)	0.2819 (2)	0.0271 (5)
C21	0.3163 (3)	0.5754 (3)	0.3743 (2)	0.0383 (6)
H21A	0.3323	0.6512	0.4366	0.057*
H21B	0.4358	0.5767	0.3341	0.057*
H21C	0.3057	0.4793	0.4112	0.057*
C22	0.0948 (4)	0.4877 (3)	0.1846 (3)	0.0393 (6)
H22A	0.2170	0.4855	0.1469	0.059*
H22B	−0.0266	0.5100	0.1236	0.059*
H22C	0.0770	0.3922	0.2207	0.059*
C3	−0.0696 (3)	0.6116 (2)	0.3424 (2)	0.0300 (5)
H3A	−0.1951	0.6051	0.2798	0.036*
H3B	−0.0683	0.5262	0.3964	0.036*
C4	−0.0778 (5)	0.7500	0.4142 (3)	0.0319 (7)
O4	−0.0941 (5)	0.7500	0.5186 (3)	0.0531 (8)
C11	0.5875 (4)	0.7500	0.0563 (3)	0.0282 (7)
O11	0.5203 (3)	0.7500	0.1524 (2)	0.0363 (6)
O12	0.7679 (3)	0.7500	0.0396 (2)	0.0384 (6)
C12	0.4247 (5)	0.7500	−0.0594 (3)	0.0423 (9)
F11	0.2320 (3)	0.7500	−0.0403 (2)	0.0487 (6)
F12	0.4369 (3)	0.8677 (4)	−0.1246 (3)	0.1345 (14)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0179 (12)	0.0293 (13)	0.0217 (15)	0.000	0.0032 (11)	0.000
C2	0.0235 (10)	0.0275 (11)	0.0302 (13)	0.0006 (7)	0.0051 (8)	0.0021 (8)
C21	0.0276 (12)	0.0411 (12)	0.0433 (16)	0.0051 (9)	−0.0009 (10)	0.0103 (11)
C22	0.0393 (13)	0.0321 (12)	0.0474 (16)	0.0012 (9)	0.0099 (10)	−0.0054 (10)
C3	0.0261 (10)	0.0329 (11)	0.0317 (14)	−0.0017 (8)	0.0066 (9)	0.0037 (9)
C4	0.0254 (15)	0.0397 (17)	0.032 (2)	0.000	0.0095 (13)	0.000
O4	0.0736 (19)	0.0555 (16)	0.0353 (18)	0.000	0.0241 (14)	0.000
C11	0.0212 (14)	0.0313 (15)	0.0318 (19)	0.000	0.0035 (12)	0.000
O11	0.0216 (10)	0.0553 (14)	0.0315 (14)	0.000	0.0036 (9)	0.000
O12	0.0198 (11)	0.0597 (15)	0.0353 (15)	0.000	0.0042 (9)	0.000
C12	0.0226 (16)	0.066 (2)	0.037 (2)	0.000	0.0017 (14)	0.000
F11	0.0217 (10)	0.0727 (14)	0.0481 (14)	0.000	−0.0029 (8)	0.000
F12	0.0538 (12)	0.225 (3)	0.108 (2)	−0.0508 (15)	−0.0288 (12)	0.120 (2)

Geometric parameters (Å, º)

N1—C2^i	1.525 (2)	C22—H22C	0.9800
N1—C2	1.525 (2)	C3—C4	1.509 (3)
N1—H1A	0.89 (4)	C3—H3A	0.9900
N1—H1B	0.91 (4)	C3—H3B	0.9900
C2—C22	1.523 (3)	C4—O4	1.204 (4)
C2—C21	1.530 (3)	C4—C3^i	1.509 (3)
C2—C3	1.541 (3)	C11—O12	1.240 (4)
C21—H21A	0.9800	C11—O11	1.246 (4)
C21—H21B	0.9800	C11—C12	1.536 (5)
C21—H21C	0.9800	C12—F12^i	1.314 (3)
C22—H22A	0.9800	C12—F12	1.314 (3)
C22—H22B	0.9800	C12—F11	1.330 (4)
C2^i—N1—C2	120.6 (2)	C2—C22—H22C	109.5
C2^i—N1—H1A	108.4 (10)	H22A—C22—H22C	109.5
C2—N1—H1A	108.4 (10)	H22B—C22—H22C	109.5
C2^i—N1—H1B	106.7 (10)	C4—C3—C2	112.52 (18)
C2—N1—H1B	106.7 (10)	C4—C3—H3A	109.1
H1A—N1—H1B	105 (3)	C2—C3—H3A	109.1
C22—C2—N1	105.75 (19)	C4—C3—H3B	109.1
C22—C2—C21	109.84 (18)	C2—C3—H3B	109.1
N1—C2—C21	111.98 (18)	H3A—C3—H3B	107.8
C22—C2—C3	110.61 (17)	O4—C4—C3^i	123.03 (14)
N1—C2—C3	107.39 (16)	O4—C4—C3	123.03 (14)
C21—C2—C3	111.13 (19)	C3^i—C4—C3	113.9 (3)
C2—C21—H21A	109.5	O12—C11—O11	129.6 (3)
C2—C21—H21B	109.5	O12—C11—C12	114.6 (3)
H21A—C21—H21B	109.5	O11—C11—C12	115.9 (3)
C2—C21—H21C	109.5	F12^i—C12—F12	109.8 (4)
H21A—C21—H21C	109.5	F12^i—C12—F11	104.4 (2)
H21B—C21—H21C	109.5	F12—C12—F11	104.4 (2)
C2—C22—H22A	109.5	F12^i—C12—C11	111.8 (2)
C2—C22—H22B	109.5	F12—C12—C11	111.8 (2)
H22A—C22—H22B	109.5	F11—C12—C11	114.0 (3)
C2^i—N1—C2—C22	169.11 (18)	C2—C3—C4—C3^i	55.8 (3)
C2^i—N1—C2—C21	−71.3 (3)	O12—C11—C12—F12^i	61.8 (3)
C2^i—N1—C2—C3	51.0 (3)	O11—C11—C12—F12^i	−118.2 (3)
C22—C2—C3—C4	−164.4 (2)	O12—C11—C12—F12	−61.8 (3)
N1—C2—C3—C4	−49.5 (3)	O11—C11—C12—F12	118.2 (3)
C21—C2—C3—C4	73.3 (3)	O12—C11—C12—F11	180.0
C2—C3—C4—O4	−125.7 (3)	O11—C11—C12—F11	0.0

Symmetry code: (i) x, −y+3/2, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···O11	0.89 (4)	1.91 (4)	2.787 (3)	168 (3)
N1—H1B···O12^ii	0.91 (4)	1.94 (4)	2.840 (3)	168 (3)

Symmetry code: (ii) x−1, y, z.