4-(Benzene­sulfon­yloxy)-2,2,6,6-tetra­methyl­piperidin-4-yl oxide

The title compound, C₁₅H₂₂NO₄S, is a nitroxyl radical, which is stable mainly because the N atom is surrounded by tertiary C atoms, preventing formation of the nitrone. More significantly, inter­molecular C—H...O hydrogen bonding contributes to the stability of the structure with weak intra­molecular C—H...π(arene) inter­actions. The N—O distance is 1.2816 (18) Å.

Key indicators

• Single-crystal X-ray study
• T = 273 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.047
• wR factor = 0.146
• Data-to-parameter ratio = 18.7

checkCIF/PLATON results

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PLAT066_ALERT_1_C Predicted and Reported Transmissions Identical .          ?
PLAT125_ALERT_4_C No _symmetry_space_group_name_Hall Given .......          ?
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for         C9
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for        C12

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

   1 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   2 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
   1 ALERT type 4 Improvement, methodology, query or suggestion

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S1. Comment

Nitroxyl radicals are compounds containing an NO group that has one unpaired electron. The structure of this fragment can be conceived as a superposition of two resonance structures (see scheme 2). The contribution of the first or second structure to the ground state may be different, depending on the effects of conjugation and polarity of the medium. Piloty & Schwerin (1901) prepared the first organic nitroxyl. The structure and free radical of this nitroxyl was later determined (Holden et al., 1951). A widely used general procedure for the preparation of aromatic nitroxyls was developed (Wieland & Roth, 1920 or?? 1914; Wieland & Kogl, 1922). A considerable amount of research, both theoretical and experimental, has been devoted to the electronic structure of nitroxyls (Stone et al., 1965; Karimov et al., 1969). It has been suggested that nitroxyl radicals are stable when the N atom is surrounded by tertiary C atoms, as formation of nitrones would not be possible in this case (Johnson et al., 1956), the absence of α-H atoms ensuring the stability of nitroxyls. The title compound, (I) (Fig. 1), is a stable radical whose structure cannot be identified through ¹H NMR. Selected bond distances and angles describing the molecular conformation are listed in Table 1. The N1/C12/C15/C7–C9 ring exists as a chair conformation. The molecules are conneted by intermolecular hydrogen bonding (Fig. 2). In addition, methyl atom C15 is involved in weak C—H···π interactions.

S2. Experimental

The title compound was synthesized according to the literature procedure (Rozantsev & Sholle, 1971); details of the synthesis will be published elsewhere (reference?). Crystals suitable for data collection were obtained by slow evaporation from an acetone–hexane solution at 293 K.

S3. Refinement

All H atoms were initially located in a difference Fourier map. The methyl H atoms were then constrained to an ideal geometry, with C—H distances of 0.96 Å and U_iso(H) = 1.5U_eq(C). All other H atoms were placed in geometrically idealized positions, with C—H distances in the range 0.93–0.98 Å, and constrained to ride on their parent atoms with U_iso(H) = 1.2U_eq(C).

Computing details

Data collection: SMART (Bruker, 1997); cell refinement: SAINT (Bruker, 1999); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 2001); software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. View of the molecule of (I), showing the atom-labelling scheme, with displacement ellipsoids drawn at the 50% probability level. H atoms are represented by circles of arbitrary size.
	Fig. 2. Intermolecular hydrogen bonding in the crystal structure of (I). Hydrogen-bonding interactions are indicated by dashed lines.

4-(Benzenesulfonyloxy)-2,2,6,6-tetramethylpiperidin-4-yl oxide

Crystal data

C15H22NO4S	Dx = 1.248 Mg m^−3
Mr = 312.40	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pbca	Cell parameters from 3922 reflections
a = 11.4827 (9) Å	θ = 2.5–22.4°
b = 15.6864 (13) Å	µ = 0.21 mm^−1
c = 18.4671 (14) Å	T = 273 K
V = 3326.3 (5) Å^3	Block, yellow
Z = 8	0.30 × 0.30 × 0.20 mm
F(000) = 1336

Data collection

Bruker SMART CCD area-detector diffractometer	2525 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.034
Graphite monochromator	θmax = 27.0°, θmin = 2.2°
ϕ and ω scans	h = −12→14
18434 measured reflections	k = −20→19
3629 independent reflections	l = −23→19

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)] = 0.047	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.146	H-atom parameters constrained
S = 1.06	w = 1/[σ^2(Fo^2) + (0.0745P)^2 + 0.3954P] where P = (Fo^2 + 2Fc^2)/3
3629 reflections	(Δ/σ)max = 0.001
194 parameters	Δρmax = 0.29 e Å^−3
0 restraints	Δρmin = −0.28 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
C1	1.02844 (19)	0.33670 (14)	0.53261 (12)	0.0665 (6)
H1	0.9591	0.3137	0.5154	0.080*
C2	1.0313 (3)	0.41762 (17)	0.55983 (15)	0.0884 (8)
H2	0.9632	0.4496	0.5619	0.106*
C3	1.1340 (4)	0.4520 (2)	0.58415 (16)	0.1036 (10)
H3	1.1355	0.5072	0.6025	0.124*
C4	1.2338 (3)	0.4052 (2)	0.58137 (16)	0.1004 (9)
H4	1.3033	0.4291	0.5973	0.120*
C5	1.23332 (19)	0.32346 (16)	0.55544 (12)	0.0718 (6)
H5	1.3014	0.2913	0.5543	0.086*
C6	1.12949 (14)	0.28984 (13)	0.53097 (10)	0.0519 (5)
C7	1.00910 (15)	0.13201 (11)	0.61446 (10)	0.0508 (4)
H7	0.9469	0.1595	0.5866	0.061*
C8	0.97895 (19)	0.04081 (13)	0.63038 (11)	0.0642 (5)
H8A	1.0428	0.0147	0.6567	0.077*
H8B	0.9699	0.0103	0.5850	0.077*
C9	0.86755 (18)	0.03165 (13)	0.67459 (11)	0.0634 (5)
C10	0.7597 (2)	0.0459 (2)	0.62763 (15)	0.1012 (9)
H10A	0.6911	0.0415	0.6571	0.152*
H10B	0.7571	0.0036	0.5901	0.152*
H10C	0.7633	0.1016	0.6062	0.152*
C11	0.8633 (3)	−0.05716 (15)	0.70819 (16)	0.1059 (10)
H11A	0.9245	−0.0627	0.7433	0.159*
H11B	0.8734	−0.0993	0.6710	0.159*
H11C	0.7893	−0.0654	0.7314	0.159*
C12	0.92191 (18)	0.18064 (12)	0.73262 (10)	0.0567 (5)
C13	0.8329 (2)	0.24558 (15)	0.70519 (16)	0.0925 (8)
H13A	0.8096	0.2308	0.6569	0.139*
H13B	0.8672	0.3014	0.7052	0.139*
H13C	0.7659	0.2453	0.7363	0.139*
C14	0.9582 (3)	0.2023 (2)	0.81001 (13)	0.0993 (9)
H14A	0.8902	0.2070	0.8399	0.149*
H14B	0.9996	0.2555	0.8103	0.149*
H14C	1.0078	0.1581	0.8285	0.149*
C15	1.02968 (16)	0.17819 (12)	0.68435 (11)	0.0573 (5)
H15A	1.0539	0.2361	0.6739	0.069*
H15B	1.0925	0.1504	0.7103	0.069*
N1	0.86669 (13)	0.09481 (10)	0.73510 (8)	0.0534 (4)
O1	1.23793 (13)	0.16091 (11)	0.47258 (9)	0.0821 (5)
O2	1.02591 (13)	0.17030 (10)	0.45846 (7)	0.0728 (4)
O3	1.11842 (10)	0.13037 (9)	0.57267 (7)	0.0620 (4)
O4	0.78658 (14)	0.08463 (10)	0.78265 (8)	0.0761 (4)
S1	1.12719 (4)	0.18359 (3)	0.50120 (3)	0.05666 (19)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0558 (12)	0.0702 (14)	0.0735 (14)	−0.0004 (10)	−0.0035 (10)	0.0015 (11)
C2	0.100 (2)	0.0721 (16)	0.0926 (18)	0.0146 (15)	0.0101 (16)	0.0039 (13)
C3	0.155 (3)	0.0725 (18)	0.0831 (17)	−0.0202 (19)	0.0097 (19)	−0.0148 (14)
C4	0.104 (2)	0.104 (2)	0.0931 (19)	−0.0421 (18)	−0.0178 (17)	−0.0127 (17)
C5	0.0534 (12)	0.0935 (17)	0.0683 (13)	−0.0153 (11)	−0.0051 (10)	−0.0037 (11)
C6	0.0447 (10)	0.0672 (12)	0.0439 (9)	−0.0074 (8)	0.0039 (8)	0.0024 (9)
C7	0.0418 (9)	0.0558 (11)	0.0548 (10)	0.0054 (8)	0.0075 (8)	−0.0002 (8)
C8	0.0805 (14)	0.0537 (12)	0.0584 (11)	−0.0013 (10)	0.0158 (10)	−0.0102 (9)
C9	0.0783 (14)	0.0533 (11)	0.0588 (11)	−0.0104 (9)	0.0140 (10)	−0.0079 (9)
C10	0.0766 (16)	0.143 (3)	0.0841 (16)	−0.0364 (16)	−0.0015 (13)	−0.0155 (16)
C11	0.166 (3)	0.0535 (14)	0.0977 (18)	−0.0177 (15)	0.0502 (18)	−0.0045 (13)
C12	0.0598 (11)	0.0496 (11)	0.0607 (12)	0.0051 (9)	0.0084 (10)	−0.0096 (8)
C13	0.0865 (16)	0.0604 (14)	0.131 (2)	0.0291 (12)	0.0397 (16)	0.0192 (14)
C14	0.115 (2)	0.115 (2)	0.0683 (15)	−0.0123 (17)	0.0110 (15)	−0.0376 (14)
C15	0.0497 (10)	0.0573 (11)	0.0649 (12)	−0.0009 (8)	0.0024 (9)	−0.0088 (9)
N1	0.0591 (9)	0.0514 (9)	0.0496 (9)	0.0055 (7)	0.0112 (7)	0.0012 (7)
O1	0.0637 (10)	0.1015 (12)	0.0813 (11)	0.0043 (8)	0.0285 (8)	−0.0141 (9)
O2	0.0679 (10)	0.0908 (11)	0.0597 (9)	−0.0141 (7)	−0.0041 (7)	−0.0142 (7)
O3	0.0489 (7)	0.0706 (9)	0.0664 (8)	0.0109 (6)	0.0123 (6)	0.0044 (7)
O4	0.0828 (10)	0.0757 (10)	0.0698 (9)	0.0062 (8)	0.0327 (8)	0.0058 (7)
S1	0.0480 (3)	0.0716 (4)	0.0504 (3)	−0.0032 (2)	0.0097 (2)	−0.0073 (2)

Geometric parameters (Å, º)

C1—C2	1.366 (3)	C10—H10A	0.9600
C1—C6	1.374 (3)	C10—H10B	0.9600
C1—H1	0.9300	C10—H10C	0.9600
C2—C3	1.372 (4)	C11—H11A	0.9600
C2—H2	0.9300	C11—H11B	0.9600
C3—C4	1.361 (4)	C11—H11C	0.9600
C3—H3	0.9300	C12—N1	1.489 (3)
C4—C5	1.369 (4)	C12—C15	1.526 (3)
C4—H4	0.9300	C12—C14	1.527 (3)
C5—C6	1.380 (3)	C12—C13	1.530 (3)
C5—H5	0.9300	C13—H13A	0.9600
C6—S1	1.755 (2)	C13—H13B	0.9600
C7—O3	1.474 (2)	C13—H13C	0.9600
C7—C15	1.499 (3)	C14—H14A	0.9600
C7—C8	1.501 (3)	C14—H14B	0.9600
C7—H7	0.9800	C14—H14C	0.9600
C8—C9	1.524 (3)	C15—H15A	0.9700
C8—H8A	0.9700	C15—H15B	0.9700
C8—H8B	0.9700	N1—O4	1.2816 (18)
C9—N1	1.493 (2)	O1—S1	1.4224 (15)
C9—C11	1.526 (3)	O2—S1	1.4208 (15)
C9—C10	1.528 (3)	O3—S1	1.5649 (15)
C2—C1—C6	119.0 (2)	H10B—C10—H10C	109.5
C2—C1—H1	120.5	C9—C11—H11A	109.5
C6—C1—H1	120.5	C9—C11—H11B	109.5
C1—C2—C3	120.4 (3)	H11A—C11—H11B	109.5
C1—C2—H2	119.8	C9—C11—H11C	109.5
C3—C2—H2	119.8	H11A—C11—H11C	109.5
C4—C3—C2	120.0 (3)	H11B—C11—H11C	109.5
C4—C3—H3	120.0	N1—C12—C15	109.92 (14)
C2—C3—H3	120.0	N1—C12—C14	106.79 (18)
C3—C4—C5	121.0 (3)	C15—C12—C14	109.32 (18)
C3—C4—H4	119.5	N1—C12—C13	109.13 (18)
C5—C4—H4	119.5	C15—C12—C13	111.43 (17)
C4—C5—C6	118.4 (2)	C14—C12—C13	110.1 (2)
C4—C5—H5	120.8	C12—C13—H13A	109.5
C6—C5—H5	120.8	C12—C13—H13B	109.5
C1—C6—C5	121.2 (2)	H13A—C13—H13B	109.5
C1—C6—S1	120.15 (15)	C12—C13—H13C	109.5
C5—C6—S1	118.59 (16)	H13A—C13—H13C	109.5
O3—C7—C15	108.97 (14)	H13B—C13—H13C	109.5
O3—C7—C8	106.40 (14)	C12—C14—H14A	109.5
C15—C7—C8	109.17 (16)	C12—C14—H14B	109.5
O3—C7—H7	110.7	H14A—C14—H14B	109.5
C15—C7—H7	110.7	C12—C14—H14C	109.5
C8—C7—H7	110.7	H14A—C14—H14C	109.5
C7—C8—C9	112.86 (16)	H14B—C14—H14C	109.5
C7—C8—H8A	109.0	C7—C15—C12	112.79 (15)
C9—C8—H8A	109.0	C7—C15—H15A	109.0
C7—C8—H8B	109.0	C12—C15—H15A	109.0
C9—C8—H8B	109.0	C7—C15—H15B	109.0
H8A—C8—H8B	107.8	C12—C15—H15B	109.0
N1—C9—C8	110.11 (15)	H15A—C15—H15B	107.8
N1—C9—C11	107.53 (17)	O4—N1—C12	116.06 (15)
C8—C9—C11	109.32 (18)	O4—N1—C9	115.77 (15)
N1—C9—C10	108.80 (18)	C12—N1—C9	125.03 (14)
C8—C9—C10	111.23 (18)	C7—O3—S1	119.15 (11)
C11—C9—C10	109.8 (2)	O2—S1—O1	119.25 (10)
C9—C10—H10A	109.5	O2—S1—O3	109.72 (8)
C9—C10—H10B	109.5	O1—S1—O3	103.74 (9)
H10A—C10—H10B	109.5	O2—S1—C6	109.01 (9)
C9—C10—H10C	109.5	O1—S1—C6	109.91 (9)
H10A—C10—H10C	109.5	O3—S1—C6	104.09 (8)
C6—C1—C2—C3	1.0 (4)	C15—C12—N1—C9	−31.7 (2)
C1—C2—C3—C4	−0.2 (4)	C14—C12—N1—C9	−150.2 (2)
C2—C3—C4—C5	−0.9 (5)	C13—C12—N1—C9	90.8 (2)
C3—C4—C5—C6	1.1 (4)	C8—C9—N1—O4	−169.51 (16)
C2—C1—C6—C5	−0.8 (3)	C11—C9—N1—O4	−50.5 (2)
C2—C1—C6—S1	176.32 (17)	C10—C9—N1—O4	68.4 (2)
C4—C5—C6—C1	−0.2 (3)	C8—C9—N1—C12	31.4 (3)
C4—C5—C6—S1	−177.38 (19)	C11—C9—N1—C12	150.4 (2)
O3—C7—C8—C9	179.29 (16)	C10—C9—N1—C12	−90.8 (2)
C15—C7—C8—C9	61.8 (2)	C15—C7—O3—S1	−111.29 (15)
C7—C8—C9—N1	−44.5 (2)	C8—C7—O3—S1	131.12 (14)
C7—C8—C9—C11	−162.4 (2)	C7—O3—S1—O2	−46.29 (15)
C7—C8—C9—C10	76.2 (2)	C7—O3—S1—O1	−174.75 (13)
O3—C7—C15—C12	−178.12 (14)	C7—O3—S1—C6	70.24 (14)
C8—C7—C15—C12	−62.3 (2)	C1—C6—S1—O2	20.85 (19)
N1—C12—C15—C7	45.3 (2)	C5—C6—S1—O2	−161.97 (15)
C14—C12—C15—C7	162.21 (19)	C1—C6—S1—O1	153.26 (16)
C13—C12—C15—C7	−75.8 (2)	C5—C6—S1—O1	−29.6 (2)
C15—C12—N1—O4	169.22 (15)	C1—C6—S1—O3	−96.18 (17)
C14—C12—N1—O4	50.7 (2)	C5—C6—S1—O3	81.01 (17)
C13—C12—N1—O4	−68.3 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1···O1^i	0.93	2.58	3.337 (3)	139
C15—H15B···O4^ii	0.97	2.46	3.351 (2)	153
C1—H1···O2	0.93	2.60	2.948 (3)	103
C7—H7···O2	0.98	2.54	2.949 (2)	105

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