Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536802015052/om6103sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S1600536802015052/om6103IIIsup2.hkl |
CCDC reference: 197485
N-Cyclohexyl-C-(2-propyl)nitrone(O—B)triphenylboroxin, (I): triphenylboroxin (2.50 g, 8 mmol) and N-cyclohexyl-C-(2-propyl)nitrone (1.35 g, 8 mmol) [N-(2-methylpropylidene)cyclohexanamine N-oxide; prepared according to the literature (Coates & Cummings, 1986)] were dissolved in 50 ml of ethanol and refluxed for 30 min. The solvent was distilled off in vacuo and the remaining oil mixed with a small amount of toluene. A crystalline substance was obtained after addition of petroleum ether and cooling. Yield: 3.66 g (95%) of colorless crystals; m.p. 413–415 K (from toluene/petroleum ether). IR (KBr): 1660 (C═N), 1600 cm-l (phenyl-C═C). 1H NMR (90 MHz, DMSO-d6/TMS), δ (p.p.m.): 1.00 [d, J = 7 Hz, (CH3)2C], 1.06–1.90 [m, (CH2)5], 3.02 (m, J = 7 Hz, N═C—CH), 3.77 (m, N—CH), 6.97 (d, J = 7 Hz, N═CH), 7.15–7.43 (m, 9 aromatic H), 7.68–7.96 (m, 6 aromatic H). Analysis calculated for C28H34B3NO4: C 69.92, H 7.12, B 6.74, N 2.91%; found: C 69.92, H 7.13, B 6.95, N 3.04%.
N-Cyclohexylhydroxylamine(O—B)triphenylboroxin N-cyclohexyl-C-(2- propyl)nitrone, (III) [2-(cyclohexylammonio-oxy)-2,4,6-triphenyl-1,3,5-trioxa-4,6-dibora-2- boratacyclohexane N-(2-methylpropylidene)cyclohexanamine N-oxide]: method A: (I) (1.44 g, 3 mmol) and N-cyclohexylhydroxylamine (0.35 g, 3 mmol) were suspended in 30 ml of ethanol and refluxed for 30 min. The solution was evaporated to half of the volume and mixed with 200 ml of petroleum ether. Upon cooling, 1.69 g (90%) of colorless crystals were obtained; m.p. 379–380 K (from ethanol/petroleum ether). IR (KBr): 2710, 2560 (N—H), 1600 cm-l (C═N/C═C). 1H NMR (90 MHz, DMSO-d6-TMS), δ (p.p.m.): 1.00 [d, J = 7 Hz, (CH3)2], 1.11–2.24 [m, 2 (CH2)5], 2.89 (m, J = 7 Hz, N═C—CH), 3.17–3.83 (m and m, 2 N—CH), 6.73 (d, J = 7 Hz, N═CH), 7.03–7.49 (m, 9 aromatic H), 7.68–7.81 (m, 6 aromatic H), 7.91 (s, exchangeable, NH), 9.50 (s, very broad, exchangeable, NH). Analysis calculated for C34H47B3N2O5: C 68.50, H 7.95, B 5.44, N 4.70%; found: C 68.22, H 7.97, B 5.34, N 4.80%.
Method B: phenylboronic acid (1.83 g, 15 mmol) and N-cyclohexylhydroxylamine (1.15 g, 10 mmol) were dissolved in 40 ml of ethanol and mixed with 2-methylpropionaldehyde (isobutyraldehyde) (0.36 g, 5 mmol). After 1 h of refluxing, the solution is evaporated to a small volume. Addition of petroleum ether and cooling yields 2.69 g (90%) of colorless crystals, identical with the product from method A.
Single crystals suitable for X-ray analysis were obtained by slow crystallization from a solvent mixture of ethanol, petroleum ether, and a small amount of benzene.
Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1989); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: TEXSAN (Molecular Structure Corporation, 1989); program(s) used to solve structure: MITHRIL (Gilmore, 1984); program(s) used to refine structure: TEXSAN; software used to prepare material for publication: TEXSAN.
Fig. 1. Views of the hydroxylamineboroxin complex and the nitrone components of the structure (ellipsoids at the 33% probability level). |
C24H28B3NO4·C10H19NO·0.5C6H6 | F(000) = 1364 |
Mr = 635.24 | Dx = 1.145 Mg m−3 |
Monoclinic, P21/n | Cu Kα radiation, λ = 1.54178 Å |
a = 13.660 (1) Å | Cell parameters from 25 reflections |
b = 19.504 (3) Å | θ = 46.5–73.8° |
c = 14.433 (2) Å | µ = 0.58 mm−1 |
β = 106.626 (8)° | T = 294 K |
V = 3684.6 (8) Å3 | Prism, colorless |
Z = 4 | 0.35 × 0.30 × 0.25 mm |
Rigaku AFC-6S diffractometer | 3098 reflections with I > 3σ(I) |
Radiation source: X-ray tube | Rint = 0.038 |
Graphite monochromator | θmax = 77.5°, θmin = 1.7° |
ω–2θ scans | h = 0→17 |
Absorption correction: ψ scan AFC6 (Molecular Structure Corporation, 1989) | k = 0→24 |
Tmin = 0.84, Tmax = 0.87 | l = −18→17 |
7579 measured reflections | 3 standard reflections every 250 reflections |
7215 independent reflections | intensity decay: 2.2% |
Refinement on F | 0 constraints |
Least-squares matrix: full | H-atom parameters constrained |
R[F2 > 2σ(F2)] = 0.047 | Weighting scheme based on measured s.u.'s w = 1/[σ2(Fo) + 0.0004Fo2] |
wR(F2) = 0.057 | (Δ/σ)max = 0.001 |
S = 1.89 | Δρmax = 0.22 e Å−3 |
7215 reflections | Δρmin = −0.14 e Å−3 |
425 parameters | Extinction correction: MSC (1989), equ(3) Acta Cryst.(1968) A24, 213 |
0 restraints | Extinction coefficient: 1.69E-6 (3) |
C24H28B3NO4·C10H19NO·0.5C6H6 | V = 3684.6 (8) Å3 |
Mr = 635.24 | Z = 4 |
Monoclinic, P21/n | Cu Kα radiation |
a = 13.660 (1) Å | µ = 0.58 mm−1 |
b = 19.504 (3) Å | T = 294 K |
c = 14.433 (2) Å | 0.35 × 0.30 × 0.25 mm |
β = 106.626 (8)° |
Rigaku AFC-6S diffractometer | 3098 reflections with I > 3σ(I) |
Absorption correction: ψ scan AFC6 (Molecular Structure Corporation, 1989) | Rint = 0.038 |
Tmin = 0.84, Tmax = 0.87 | 3 standard reflections every 250 reflections |
7579 measured reflections | intensity decay: 2.2% |
7215 independent reflections |
R[F2 > 2σ(F2)] = 0.047 | 0 restraints |
wR(F2) = 0.057 | H-atom parameters constrained |
S = 1.89 | Δρmax = 0.22 e Å−3 |
7215 reflections | Δρmin = −0.14 e Å−3 |
425 parameters |
Experimental. The scan width was (1.10 + 0.20tanθ)° with an ω scan speed of 32° per minute (up to 10 scans to achieve I/σ(I) > 40). Stationary background counts were recorded at each end of the scan, and the scan time:background time ratio was 2:1. Three standard reflections decreased gradually in intensity by 2.2%; a linear decay correction was applied to the data. |
x | y | z | Uiso*/Ueq | ||
O1 | 0.5734 (1) | 0.14938 (9) | 0.6865 (1) | 0.0584 (11) | |
O2 | 0.6121 (2) | 0.2567 (1) | 0.6286 (1) | 0.0619 (11) | |
O3 | 0.6264 (1) | 0.1559 (1) | 0.5411 (1) | 0.0608 (13) | |
O4 | 0.5511 (1) | 0.05186 (9) | 0.5795 (1) | 0.0579 (10) | |
O5 | 0.4106 (2) | 0.2064 (1) | 0.4821 (2) | 0.075 (1) | |
N1 | 0.4491 (2) | 0.0704 (1) | 0.5290 (2) | 0.054 (1) | |
N2 | 0.3544 (2) | 0.2485 (1) | 0.4183 (2) | 0.065 (1) | |
C1 | 0.3753 (2) | 0.0605 (1) | 0.5866 (2) | 0.061 (1) | |
C2 | 0.2689 (3) | 0.0698 (2) | 0.5196 (2) | 0.075 (2) | |
C3 | 0.1907 (3) | 0.0592 (3) | 0.5743 (3) | 0.106 (2) | |
C4 | 0.2030 (4) | −0.0098 (3) | 0.6244 (4) | 0.120 (4) | |
C5 | 0.3095 (4) | −0.0196 (2) | 0.6877 (3) | 0.111 (4) | |
C6 | 0.3881 (3) | −0.0094 (2) | 0.6335 (3) | 0.086 (2) | |
C7 | 0.7280 (3) | 0.0789 (1) | 0.6770 (2) | 0.066 (1) | |
C8 | 0.8140 (3) | 0.0885 (2) | 0.6462 (3) | 0.095 (2) | |
C9 | 0.9081 (4) | 0.0606 (3) | 0.6951 (5) | 0.136 (4) | |
C10 | 0.9174 (5) | 0.0231 (3) | 0.7756 (6) | 0.151 (4) | |
C11 | 0.8366 (5) | 0.0122 (2) | 0.8081 (4) | 0.139 (4) | |
C12 | 0.7409 (3) | 0.0404 (2) | 0.7595 (3) | 0.099 (2) | |
C13 | 0.5354 (2) | 0.2568 (2) | 0.7678 (2) | 0.061 (1) | |
C14 | 0.5469 (3) | 0.3273 (2) | 0.7816 (2) | 0.073 (2) | |
C15 | 0.5142 (3) | 0.3613 (2) | 0.8500 (3) | 0.095 (2) | |
C16 | 0.4679 (3) | 0.3264 (3) | 0.9074 (3) | 0.105 (2) | |
C17 | 0.4545 (3) | 0.2567 (3) | 0.8971 (3) | 0.106 (2) | |
C18 | 0.4881 (3) | 0.2230 (2) | 0.8269 (3) | 0.084 (2) | |
C19 | 0.6494 (2) | 0.2709 (2) | 0.4690 (2) | 0.068 (2) | |
C20 | 0.6768 (3) | 0.2436 (2) | 0.3924 (3) | 0.099 (2) | |
C21 | 0.6977 (4) | 0.2857 (4) | 0.3215 (3) | 0.129 (4) | |
C22 | 0.6906 (4) | 0.3549 (4) | 0.3297 (4) | 0.143 (5) | |
C23 | 0.6661 (4) | 0.3829 (3) | 0.4047 (4) | 0.123 (4) | |
C24 | 0.6442 (3) | 0.3416 (2) | 0.4737 (3) | 0.092 (2) | |
C25 | 0.3001 (3) | 0.3015 (2) | 0.4577 (2) | 0.070 (2) | |
C26 | 0.2426 (3) | 0.2706 (2) | 0.5202 (3) | 0.105 (2) | |
C27 | 0.1875 (4) | 0.3241 (3) | 0.5607 (4) | 0.141 (4) | |
C28 | 0.2612 (6) | 0.3775 (4) | 0.6155 (4) | 0.187 (6) | |
C29 | 0.3238 (4) | 0.4075 (3) | 0.5553 (5) | 0.155 (5) | |
C30 | 0.3771 (3) | 0.3541 (2) | 0.5133 (3) | 0.109 (2) | |
C31 | 0.3497 (3) | 0.2467 (2) | 0.3268 (3) | 0.077 (2) | |
C32 | 0.4041 (3) | 0.1965 (2) | 0.2844 (3) | 0.096 (2) | |
C33 | 0.4274 (3) | 0.2264 (3) | 0.1937 (3) | 0.130 (4) | |
C34 | 0.3415 (3) | 0.1320 (2) | 0.2594 (3) | 0.115 (2) | |
C35 | 1.0162 (6) | 0.4747 (5) | 0.4188 (4) | 0.142 (5) | |
C36 | 0.9448 (5) | 0.4472 (3) | 0.4547 (6) | 0.139 (5) | |
C37 | 0.9279 (4) | 0.4712 (4) | 0.5359 (6) | 0.128 (4) | |
B1 | 0.6203 (3) | 0.1126 (2) | 0.6218 (3) | 0.058 (2) | |
B2 | 0.5745 (3) | 0.2183 (2) | 0.6908 (3) | 0.057 (2) | |
B3 | 0.6272 (3) | 0.2248 (2) | 0.5481 (3) | 0.060 (2) | |
H1 | 0.4483 | 0.1189 | 0.5108 | 0.065* | |
H2 | 0.4269 | 0.0423 | 0.4704 | 0.065* | |
H3 | 0.3878 | 0.0956 | 0.6372 | 0.072* | |
H4 | 0.2620 | 0.1162 | 0.4926 | 0.090* | |
H5 | 0.2572 | 0.0363 | 0.4669 | 0.090* | |
H6 | 0.1989 | 0.0954 | 0.6230 | 0.128* | |
H7 | 0.1222 | 0.0620 | 0.5287 | 0.128* | |
H8 | 0.1556 | −0.0126 | 0.6640 | 0.144* | |
H9 | 0.1870 | −0.0461 | 0.5754 | 0.144* | |
H10 | 0.3225 | 0.0136 | 0.7408 | 0.133* | |
H11 | 0.3161 | −0.0662 | 0.7141 | 0.133* | |
H12 | 0.3792 | −0.0448 | 0.5835 | 0.104* | |
H13 | 0.4568 | −0.0131 | 0.6788 | 0.104* | |
H14 | 0.8083 | 0.1158 | 0.5880 | 0.114* | |
H15 | 0.9675 | 0.0682 | 0.6712 | 0.163* | |
H16 | 0.9839 | 0.0037 | 0.8104 | 0.180* | |
H17 | 0.8439 | −0.0156 | 0.8662 | 0.167* | |
H18 | 0.6825 | 0.0326 | 0.7849 | 0.119* | |
H19 | 0.5798 | 0.3535 | 0.7408 | 0.089* | |
H20 | 0.5241 | 0.4110 | 0.8576 | 0.114* | |
H21 | 0.4441 | 0.3510 | 0.9561 | 0.126* | |
H22 | 0.4217 | 0.2312 | 0.9385 | 0.128* | |
H23 | 0.4777 | 0.1734 | 0.8193 | 0.101* | |
H24 | 0.6819 | 0.1937 | 0.3870 | 0.118* | |
H25 | 0.7170 | 0.2657 | 0.2670 | 0.155* | |
H26 | 0.7036 | 0.3847 | 0.2798 | 0.171* | |
H27 | 0.6637 | 0.4329 | 0.4106 | 0.147* | |
H28 | 0.6244 | 0.3629 | 0.5272 | 0.111* | |
H29 | 0.2515 | 0.3247 | 0.4035 | 0.084* | |
H30 | 0.1926 | 0.2381 | 0.4819 | 0.125* | |
H31 | 0.2905 | 0.2464 | 0.5738 | 0.125* | |
H32 | 0.1360 | 0.3462 | 0.5076 | 0.168* | |
H33 | 0.1539 | 0.3021 | 0.6046 | 0.168* | |
H34 | 0.2225 | 0.4144 | 0.6350 | 0.225* | |
H35 | 0.3072 | 0.3563 | 0.6733 | 0.225* | |
H36 | 0.2785 | 0.4338 | 0.5022 | 0.186* | |
H37 | 0.3752 | 0.4382 | 0.5960 | 0.186* | |
H38 | 0.4285 | 0.3311 | 0.5656 | 0.132* | |
H39 | 0.4107 | 0.3759 | 0.4694 | 0.132* | |
H40 | 0.3074 | 0.2810 | 0.2839 | 0.094* | |
H41 | 0.4689 | 0.1853 | 0.3324 | 0.115* | |
H42 | 0.4694 | 0.2677 | 0.2115 | 0.157* | |
H43 | 0.4644 | 0.1923 | 0.1669 | 0.157* | |
H44 | 0.3632 | 0.2381 | 0.1452 | 0.157* | |
H45 | 0.2761 | 0.1426 | 0.2119 | 0.138* | |
H46 | 0.3787 | 0.0983 | 0.2320 | 0.138* | |
H47 | 0.3291 | 0.1132 | 0.3179 | 0.138* | |
H48 | 1.0278 | 0.4559 | 0.3599 | 0.171* | |
H49 | 0.9040 | 0.4085 | 0.4209 | 0.166* | |
H50 | 0.8762 | 0.4502 | 0.5619 | 0.155* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.072 (1) | 0.042 (1) | 0.063 (1) | 0.002 (1) | 0.021 (1) | −0.003 (1) |
O2 | 0.072 (1) | 0.046 (1) | 0.065 (1) | −0.005 (1) | 0.016 (1) | −0.006 (1) |
O3 | 0.065 (1) | 0.050 (1) | 0.065 (1) | 0.003 (1) | 0.017 (1) | −0.002 (1) |
O4 | 0.053 (1) | 0.044 (1) | 0.070 (1) | 0.005 (1) | 0.007 (1) | −0.004 (1) |
O5 | 0.083 (2) | 0.048 (1) | 0.080 (1) | 0.016 (1) | 0.004 (1) | 0.012 (1) |
N1 | 0.056 (2) | 0.043 (1) | 0.062 (2) | 0.004 (1) | 0.010 (1) | −0.003 (1) |
N2 | 0.060 (2) | 0.047 (1) | 0.075 (2) | 0.003 (1) | 0.004 (1) | −0.002 (1) |
C1 | 0.066 (2) | 0.055 (2) | 0.063 (2) | −0.000 (2) | 0.024 (2) | −0.006 (2) |
C2 | 0.061 (2) | 0.077 (2) | 0.086 (2) | −0.002 (2) | 0.018 (2) | 0.004 (2) |
C3 | 0.069 (3) | 0.148 (4) | 0.107 (3) | −0.007 (3) | 0.032 (2) | −0.003 (3) |
C4 | 0.120 (4) | 0.146 (4) | 0.113 (4) | −0.051 (3) | 0.064 (3) | −0.009 (3) |
C5 | 0.132 (4) | 0.111 (3) | 0.108 (3) | −0.006 (3) | 0.062 (3) | 0.019 (3) |
C6 | 0.102 (3) | 0.076 (2) | 0.089 (3) | 0.006 (2) | 0.040 (2) | 0.019 (2) |
C7 | 0.070 (2) | 0.040 (2) | 0.075 (2) | 0.001 (2) | 0.003 (2) | −0.015 (2) |
C8 | 0.065 (3) | 0.098 (3) | 0.114 (3) | 0.010 (2) | 0.012 (2) | −0.014 (2) |
C9 | 0.063 (3) | 0.128 (4) | 0.197 (6) | 0.020 (3) | 0.004 (4) | −0.026 (4) |
C10 | 0.092 (4) | 0.095 (4) | 0.205 (7) | 0.025 (4) | −0.052 (5) | −0.033 (4) |
C11 | 0.135 (5) | 0.084 (3) | 0.147 (5) | 0.018 (4) | −0.043 (4) | 0.020 (3) |
C12 | 0.095 (3) | 0.073 (2) | 0.105 (3) | 0.008 (2) | −0.008 (3) | 0.017 (2) |
C13 | 0.056 (2) | 0.055 (2) | 0.064 (2) | 0.002 (2) | 0.007 (2) | −0.005 (2) |
C14 | 0.086 (3) | 0.059 (2) | 0.073 (2) | 0.010 (2) | 0.016 (2) | −0.009 (2) |
C15 | 0.114 (3) | 0.073 (3) | 0.094 (3) | 0.013 (2) | 0.024 (3) | −0.021 (2) |
C16 | 0.109 (3) | 0.107 (4) | 0.103 (3) | 0.020 (3) | 0.039 (3) | −0.031 (3) |
C17 | 0.108 (3) | 0.121 (4) | 0.104 (3) | −0.003 (3) | 0.055 (3) | −0.016 (3) |
C18 | 0.094 (3) | 0.072 (2) | 0.090 (3) | −0.007 (2) | 0.032 (2) | −0.013 (2) |
C19 | 0.054 (2) | 0.068 (2) | 0.068 (2) | −0.008 (2) | 0.008 (2) | 0.005 (2) |
C20 | 0.093 (3) | 0.113 (3) | 0.091 (3) | −0.020 (2) | 0.028 (3) | 0.001 (3) |
C21 | 0.119 (4) | 0.186 (6) | 0.090 (4) | −0.040 (4) | 0.044 (3) | 0.005 (4) |
C22 | 0.127 (5) | 0.179 (7) | 0.111 (4) | −0.047 (5) | 0.015 (4) | 0.057 (5) |
C23 | 0.125 (4) | 0.104 (4) | 0.127 (4) | −0.018 (3) | 0.016 (3) | 0.043 (4) |
C24 | 0.094 (3) | 0.073 (2) | 0.106 (3) | −0.007 (2) | 0.020 (2) | 0.026 (2) |
C25 | 0.070 (2) | 0.061 (2) | 0.073 (2) | 0.016 (2) | 0.008 (2) | 0.004 (2) |
C26 | 0.098 (3) | 0.109 (3) | 0.111 (3) | 0.033 (3) | 0.036 (3) | 0.014 (3) |
C27 | 0.140 (5) | 0.179 (5) | 0.111 (4) | 0.050 (4) | 0.050 (3) | −0.001 (4) |
C28 | 0.178 (7) | 0.242 (8) | 0.118 (5) | 0.113 (6) | 0.000 (4) | −0.075 (5) |
C29 | 0.123 (5) | 0.116 (4) | 0.195 (6) | 0.032 (3) | −0.006 (4) | −0.087 (4) |
C30 | 0.097 (3) | 0.070 (2) | 0.135 (4) | 0.012 (2) | −0.009 (3) | −0.029 (2) |
C31 | 0.073 (2) | 0.081 (2) | 0.067 (2) | 0.015 (2) | 0.001 (2) | −0.003 (2) |
C32 | 0.076 (3) | 0.107 (3) | 0.094 (3) | 0.018 (2) | 0.008 (2) | −0.016 (3) |
C33 | 0.103 (3) | 0.201 (5) | 0.099 (3) | 0.006 (3) | 0.045 (3) | 0.007 (3) |
C34 | 0.112 (3) | 0.084 (3) | 0.135 (4) | 0.009 (3) | 0.010 (3) | −0.022 (3) |
C35 | 0.123 (5) | 0.176 (6) | 0.126 (5) | 0.002 (4) | 0.034 (4) | −0.014 (5) |
C36 | 0.113 (5) | 0.131 (5) | 0.171 (7) | −0.004 (4) | 0.040 (4) | −0.023 (4) |
C37 | 0.117 (5) | 0.129 (5) | 0.145 (5) | 0.005 (4) | 0.048 (4) | 0.027 (4) |
B1 | 0.064 (2) | 0.043 (2) | 0.063 (2) | −0.001 (2) | 0.011 (2) | −0.005 (2) |
B2 | 0.054 (2) | 0.052 (2) | 0.057 (2) | 0.001 (2) | 0.005 (2) | −0.004 (2) |
B3 | 0.048 (2) | 0.059 (2) | 0.067 (2) | −0.003 (2) | 0.007 (2) | 0.000 (2) |
O1—B1 | 1.463 (5) | C16—H21 | 0.98 |
O1—B2 | 1.345 (4) | C17—C18 | 1.391 (7) |
O2—B2 | 1.376 (5) | C17—H22 | 0.98 |
O2—B3 | 1.384 (5) | C18—H23 | 0.98 |
O3—B1 | 1.460 (5) | C19—C20 | 1.372 (6) |
O3—B3 | 1.347 (4) | C19—C24 | 1.383 (5) |
O4—N1 | 1.422 (3) | C19—B3 | 1.550 (6) |
O4—B1 | 1.530 (4) | C20—C21 | 1.404 (8) |
O5—N2 | 1.306 (3) | C20—H24 | 0.98 |
N1—C1 | 1.491 (4) | C21—C22 | 1.36 (1) |
N1—H1 | 0.98 | C21—H25 | 0.98 |
N1—H2 | 0.98 | C22—C23 | 1.338 (9) |
N2—C25 | 1.478 (5) | C22—H26 | 0.98 |
N2—C31 | 1.304 (5) | C23—C24 | 1.379 (8) |
C1—C2 | 1.509 (4) | C23—H27 | 0.98 |
C1—C6 | 1.510 (4) | C24—H28 | 0.98 |
C1—H3 | 0.98 | C25—C26 | 1.483 (6) |
C2—C3 | 1.513 (6) | C25—C30 | 1.523 (5) |
C2—H4 | 0.98 | C25—H29 | 0.98 |
C2—H5 | 0.98 | C26—C27 | 1.500 (7) |
C3—C4 | 1.514 (8) | C26—H30 | 0.98 |
C3—H6 | 0.98 | C26—H31 | 0.98 |
C3—H7 | 0.98 | C27—C28 | 1.506 (9) |
C4—C5 | 1.492 (7) | C27—H32 | 0.98 |
C4—H8 | 0.98 | C27—H33 | 0.98 |
C4—H9 | 0.98 | C28—C29 | 1.50 (1) |
C5—C6 | 1.512 (7) | C28—H34 | 0.98 |
C5—H10 | 0.98 | C28—H35 | 0.98 |
C5—H11 | 0.98 | C29—C30 | 1.495 (8) |
C6—H12 | 0.98 | C29—H36 | 0.98 |
C6—H13 | 0.98 | C29—H37 | 0.98 |
C7—C8 | 1.383 (6) | C30—H38 | 0.98 |
C7—C12 | 1.376 (5) | C30—H39 | 0.98 |
C7—B1 | 1.600 (5) | C31—C32 | 1.465 (6) |
C8—C9 | 1.388 (6) | C31—H40 | 0.98 |
C8—H14 | 0.98 | C32—C33 | 1.547 (7) |
C9—C10 | 1.35 (1) | C32—C34 | 1.506 (5) |
C9—H15 | 0.98 | C32—H41 | 0.98 |
C10—C11 | 1.33 (1) | C33—H42 | 0.98 |
C10—H16 | 0.98 | C33—H43 | 0.98 |
C11—C12 | 1.407 (7) | C33—H44 | 0.98 |
C11—H17 | 0.98 | C34—H45 | 0.98 |
C12—H18 | 0.98 | C34—H46 | 0.98 |
C13—C14 | 1.392 (5) | C34—H47 | 0.98 |
C13—C18 | 1.377 (6) | C35—C36 | 1.34 (1) |
C13—B2 | 1.557 (6) | C35—C37i | 1.36 (1) |
C14—C15 | 1.366 (6) | C35—H48 | 0.98 |
C14—H19 | 0.98 | C36—C37 | 1.34 (1) |
C15—C16 | 1.360 (7) | C36—H49 | 0.98 |
C15—H20 | 0.98 | C37—H50 | 0.98 |
C16—C17 | 1.374 (8) | ||
O1···O5 | 3.336 (3) | O5···B2 | 3.206 (4) |
O2···O5 | 3.111 (3) | O5···C1 | 3.320 (3) |
O3···O5 | 2.991 (3) | O5···C2 | 3.426 (5) |
O4···N1ii | 2.852 (3) | O5···B1 | 3.509 (4) |
O4···O4ii | 3.078 (3) | O5···C19 | 3.551 (4) |
O4···C6ii | 3.505 (5) | N1···N1ii | 3.293 (5) |
O4···C1ii | 3.597 (3) | C12···C34ii | 3.532 (5) |
O5···N1 | 2.751 (3) | C17···C21iii | 3.463 (7) |
O5···B3 | 2.860 (5) | ||
B1—O1—B2 | 121.2 (3) | C20—C21—C22 | 118.8 (5) |
B2—O2—B3 | 118.4 (3) | C20—C21—H25 | 120.7 |
B1—O3—B3 | 121.2 (3) | C22—C21—H25 | 120.5 |
N1—O4—B1 | 114.2 (2) | C21—C22—C23 | 121.1 (6) |
O4—N1—C1 | 113.6 (2) | C21—C22—H26 | 119.5 |
O4—N1—H1 | 108.5 | C23—C22—H26 | 119.5 |
O4—N1—H2 | 108.4 | C22—C23—C24 | 120.2 (6) |
C1—N1—H1 | 108.5 | C22—C23—H27 | 119.9 |
C1—N1—H2 | 108.5 | C24—C23—H27 | 119.9 |
H1—N1—H2 | 109.3 | C19—C24—C23 | 121.5 (4) |
O5—N2—C25 | 115.3 (3) | C19—C24—H28 | 119.4 |
O5—N2—C31 | 123.1 (3) | C23—C24—H28 | 119.1 |
C25—N2—C31 | 121.6 (3) | N2—C25—C26 | 111.2 (3) |
N1—C1—C2 | 107.9 (2) | N2—C25—C30 | 109.1 (3) |
N1—C1—C6 | 110.9 (3) | N2—C25—H29 | 108.4 |
N1—C1—H3 | 108.9 | C26—C25—C30 | 111.1 (3) |
C2—C1—C6 | 111.3 (3) | C26—C25—H29 | 108.5 |
C2—C1—H3 | 108.9 | C30—C25—H29 | 108.5 |
C6—C1—H3 | 108.9 | C25—C26—C27 | 111.5 (4) |
C1—C2—C3 | 110.1 (3) | C25—C26—H30 | 109.0 |
C1—C2—H4 | 109.4 | C25—C26—H31 | 109.0 |
C1—C2—H5 | 109.3 | C27—C26—H30 | 108.9 |
C3—C2—H4 | 109.4 | C27—C26—H31 | 108.9 |
C3—C2—H5 | 109.3 | H30—C26—H31 | 109.5 |
H4—C2—H5 | 109.4 | C26—C27—C28 | 110.6 (5) |
C2—C3—C4 | 111.8 (4) | C26—C27—H32 | 109.2 |
C2—C3—H6 | 108.8 | C26—C27—H33 | 109.1 |
C2—C3—H7 | 108.9 | C28—C27—H32 | 109.2 |
C4—C3—H6 | 108.9 | C28—C27—H33 | 109.2 |
C4—C3—H7 | 108.9 | H32—C27—H33 | 109.5 |
H6—C3—H7 | 109.5 | C27—C28—C29 | 111.8 (5) |
C3—C4—C5 | 111.2 (4) | C27—C28—H34 | 108.9 |
C3—C4—H8 | 109.1 | C27—C28—H35 | 108.9 |
C3—C4—H9 | 109.0 | C29—C28—H34 | 108.9 |
C5—C4—H8 | 109.1 | C29—C28—H35 | 108.9 |
C5—C4—H9 | 109.0 | H34—C28—H35 | 109.4 |
H8—C4—H9 | 109.4 | C28—C29—C30 | 112.8 (5) |
C4—C5—C6 | 112.3 (4) | C28—C29—H36 | 108.6 |
C4—C5—H10 | 108.7 | C28—C29—H37 | 108.7 |
C4—C5—H11 | 108.8 | C30—C29—H36 | 108.6 |
C6—C5—H10 | 108.7 | C30—C29—H37 | 108.7 |
C6—C5—H11 | 108.9 | H36—C29—H37 | 109.4 |
H10—C5—H11 | 109.4 | C25—C30—C29 | 109.9 (4) |
C1—C6—C5 | 110.0 (3) | C25—C30—H38 | 109.4 |
C1—C6—H12 | 109.4 | C25—C30—H39 | 109.4 |
C1—C6—H13 | 109.3 | C29—C30—H38 | 109.3 |
C5—C6—H12 | 109.3 | C29—C30—H39 | 109.4 |
C5—C6—H13 | 109.3 | H38—C30—H39 | 109.4 |
H12—C6—H13 | 109.4 | N2—C31—C32 | 123.9 (3) |
C8—C7—C12 | 116.2 (3) | N2—C31—H40 | 118.1 |
C8—C7—B1 | 121.9 (3) | C32—C31—H40 | 118.1 |
C12—C7—B1 | 121.8 (4) | C31—C32—C33 | 110.7 (4) |
C7—C8—C9 | 122.1 (4) | C31—C32—C34 | 109.7 (4) |
C7—C8—H14 | 118.9 | C31—C32—H41 | 108.5 |
C9—C8—H14 | 119.0 | C33—C32—C34 | 110.6 (4) |
C8—C9—C10 | 119.7 (6) | C33—C32—H41 | 108.6 |
C8—C9—H15 | 120.1 | C34—C32—H41 | 108.6 |
C10—C9—H15 | 120.2 | C32—C33—H42 | 109.6 |
C9—C10—C11 | 120.4 (6) | C32—C33—H43 | 109.4 |
C9—C10—H16 | 119.8 | C32—C33—H44 | 109.5 |
C11—C10—H16 | 119.8 | H42—C33—H43 | 109.4 |
C10—C11—C12 | 120.4 (5) | H42—C33—H44 | 109.5 |
C10—C11—H17 | 119.8 | H43—C33—H44 | 109.5 |
C12—C11—H17 | 119.7 | C32—C34—H45 | 109.4 |
C7—C12—C11 | 121.0 (5) | C32—C34—H46 | 109.4 |
C7—C12—H18 | 119.5 | C32—C34—H47 | 109.4 |
C11—C12—H18 | 119.5 | H45—C34—H46 | 109.5 |
C14—C13—C18 | 116.0 (3) | H45—C34—H47 | 109.5 |
C14—C13—B2 | 122.1 (3) | H46—C34—H47 | 109.5 |
C18—C13—B2 | 121.9 (4) | C36—C35—C37i | 119.8 (7) |
C13—C14—C15 | 122.4 (4) | C36—C35—H48 | 120.1 |
C13—C14—H19 | 118.8 | C37i—C35—H48 | 120.1 |
C15—C14—H19 | 118.8 | C35—C36—C37 | 121.6 (6) |
C14—C15—C16 | 120.2 (4) | C35—C36—H49 | 119.2 |
C14—C15—H20 | 119.8 | C37—C36—H49 | 119.2 |
C16—C15—H20 | 120.0 | C35i—C37—C36 | 118.6 (7) |
C15—C16—C17 | 120.0 (5) | C35i—C37—H50 | 120.6 |
C15—C16—H21 | 120.0 | C36—C37—H50 | 120.8 |
C17—C16—H21 | 120.0 | O1—B1—O3 | 111.2 (3) |
C16—C17—C18 | 119.0 (4) | O1—B1—O4 | 107.5 (3) |
C16—C17—H22 | 120.4 | O1—B1—C7 | 113.1 (3) |
C18—C17—H22 | 120.6 | O3—B1—O4 | 107.4 (3) |
C13—C18—C17 | 122.4 (4) | O3—B1—C7 | 112.4 (3) |
C13—C18—H23 | 118.8 | O4—B1—C7 | 104.8 (2) |
C17—C18—H23 | 118.7 | O1—B2—O2 | 121.0 (4) |
C20—C19—C24 | 117.1 (4) | O1—B2—C13 | 120.9 (4) |
C20—C19—B3 | 121.6 (4) | O2—B2—C13 | 118.1 (3) |
C24—C19—B3 | 121.2 (3) | O2—B3—O3 | 120.7 (3) |
C19—C20—C21 | 121.3 (4) | O2—B3—C19 | 117.7 (3) |
C19—C20—H24 | 119.4 | O3—B3—C19 | 121.5 (4) |
C21—C20—H24 | 119.3 | ||
O1—B1—O3—B3 | 24.1 (4) | C3—C2—C1—C6 | 57.3 (4) |
O1—B1—O4—N1 | 57.7 (3) | C3—C4—C5—C6 | −54.4 (5) |
O1—B1—C7—C8 | −129.7 (3) | C7—C8—C9—C10 | −0.3 (8) |
O1—B1—C7—C12 | 48.3 (4) | C7—C12—C11—C10 | 0.9 (7) |
O1—B2—O2—B3 | 14.4 (4) | C7—B1—O1—B2 | 103.8 (3) |
O1—B2—C13—C14 | 172.1 (3) | C7—B1—O3—B3 | −103.8 (3) |
O1—B2—C13—C18 | −7.3 (4) | C8—C7—C12—C11 | −0.7 (5) |
O2—B2—O1—B1 | 5.6 (4) | C8—C9—C10—C11 | 0.5 (9) |
O2—B2—C13—C14 | −6.6 (4) | C9—C8—C7—C12 | 0.4 (6) |
O2—B2—C13—C18 | 173.9 (3) | C9—C8—C7—B1 | 178.6 (4) |
O2—B3—O3—B1 | −6.4 (4) | C9—C10—C11—C12 | −0.8 (9) |
O2—B3—C19—C20 | 172.4 (3) | C11—C12—C7—B1 | −178.8 (3) |
O2—B3—C19—C24 | −6.4 (4) | C13—C14—C15—C16 | −0.4 (5) |
O3—B1—O1—B2 | −23.7 (4) | C13—C18—C17—C16 | 0.7 (5) |
O3—B1—O4—N1 | −62.1 (3) | C13—B2—O1—B1 | −173.1 (3) |
O3—B1—C7—C8 | −2.9 (4) | C13—B2—O2—B3 | −166.9 (3) |
O3—B1—C7—C12 | 175.1 (3) | C14—C13—C18—C17 | −0.7 (5) |
O3—B3—O2—B2 | −14.0 (5) | C14—C15—C16—C17 | 0.4 (5) |
O3—B3—C19—C20 | −5.1 (5) | C15—C14—C13—C18 | 0.5 (5) |
O3—B3—C19—C24 | 176.1 (3) | C15—C14—C13—B2 | −179.0 (3) |
O4—N1—C1—C2 | −170.1 (2) | C15—C16—C17—C18 | −0.6 (5) |
O4—N1—C1—C6 | −48.0 (3) | C17—C18—C13—B2 | 178.8 (3) |
O4—B1—O1—B2 | −141.0 (2) | C19—C20—C21—C22 | 0.1 (6) |
O4—B1—O3—B3 | 141.4 (3) | C19—C24—C23—C22 | 1.7 (7) |
O4—B1—C7—C8 | 113.4 (3) | C19—B3—O2—B2 | 168.5 (3) |
O4—B1—C7—C12 | −68.5 (4) | C19—B3—O3—B1 | 171.0 (3) |
O5—N2—C25—C26 | −50.9 (3) | C20—C19—C24—C23 | −0.3 (5) |
O5—N2—C25—C30 | 71.9 (4) | C20—C21—C22—C23 | 1.3 (7) |
O5—N2—C31—C32 | 1.8 (5) | C21—C20—C19—C24 | −0.6 (5) |
N1—O4—B1—C7 | 178.2 (3) | C21—C20—C19—B3 | −179.4 (3) |
N1—C1—C2—C3 | 179.2 (3) | C21—C22—C23—C24 | −2.2 (7) |
N1—C1—C6—C5 | −177.4 (3) | C23—C24—C19—B3 | 178.5 (4) |
N2—C25—C26—C27 | 179.8 (3) | C25—N2—C31—C32 | 178.3 (3) |
N2—C25—C30—C29 | −179.0 (4) | C25—C26—C27—C28 | −56.5 (5) |
N2—C31—C32—C33 | −152.2 (4) | C25—C30—C29—C28 | 53.9 (5) |
N2—C31—C32—C34 | 85.4 (4) | C26—C25—N2—C31 | 132.3 (3) |
C1—N1—O4—B1 | −100.5 (3) | C26—C25—C30—C29 | −56.1 (5) |
C1—C2—C3—C4 | −55.3 (4) | C26—C27—C28—C29 | 53.5 (7) |
C1—C6—C5—C4 | 55.9 (4) | C27—C26—C25—C30 | 58.2 (4) |
C2—C1—C6—C5 | −57.3 (4) | C27—C28—C29—C30 | −53.5 (7) |
C2—C3—C4—C5 | 54.1 (5) | C30—C25—N2—C31 | −104.9 (3) |
Symmetry codes: (i) −x+2, −y+1, −z+1; (ii) −x+1, −y, −z+1; (iii) x−1/2, −y+1/2, z+1/2. |
Experimental details
Crystal data | |
Chemical formula | C24H28B3NO4·C10H19NO·0.5C6H6 |
Mr | 635.24 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 294 |
a, b, c (Å) | 13.660 (1), 19.504 (3), 14.433 (2) |
β (°) | 106.626 (8) |
V (Å3) | 3684.6 (8) |
Z | 4 |
Radiation type | Cu Kα |
µ (mm−1) | 0.58 |
Crystal size (mm) | 0.35 × 0.30 × 0.25 |
Data collection | |
Diffractometer | Rigaku AFC-6S diffractometer |
Absorption correction | ψ scan AFC6 (Molecular Structure Corporation, 1989) |
Tmin, Tmax | 0.84, 0.87 |
No. of measured, independent and observed [I > 3σ(I)] reflections | 7579, 7215, 3098 |
Rint | 0.038 |
(sin θ/λ)max (Å−1) | 0.633 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.047, 0.057, 1.89 |
No. of reflections | 7215 |
No. of parameters | 425 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.22, −0.14 |
Computer programs: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1989), MSC/AFC Diffractometer Control Software, TEXSAN (Molecular Structure Corporation, 1989), MITHRIL (Gilmore, 1984), TEXSAN.
O1—B1 | 1.463 (5) | C13—C18 | 1.377 (6) |
O1—B2 | 1.345 (4) | C13—B2 | 1.557 (6) |
O2—B2 | 1.376 (5) | C14—C15 | 1.366 (6) |
O2—B3 | 1.384 (5) | C15—C16 | 1.360 (7) |
O3—B1 | 1.460 (5) | C16—C17 | 1.374 (8) |
O3—B3 | 1.347 (4) | C17—C18 | 1.391 (7) |
O4—N1 | 1.422 (3) | C19—C20 | 1.372 (6) |
O4—B1 | 1.530 (4) | C19—C24 | 1.383 (5) |
O5—N2 | 1.306 (3) | C19—B3 | 1.550 (6) |
N1—C1 | 1.491 (4) | C20—C21 | 1.404 (8) |
N2—C25 | 1.478 (5) | C21—C22 | 1.36 (1) |
N2—C31 | 1.304 (5) | C22—C23 | 1.338 (9) |
C1—C2 | 1.509 (4) | C23—C24 | 1.379 (8) |
C1—C6 | 1.510 (4) | C25—C26 | 1.483 (6) |
C2—C3 | 1.513 (6) | C25—C30 | 1.523 (5) |
C3—C4 | 1.514 (8) | C26—C27 | 1.500 (7) |
C4—C5 | 1.492 (7) | C27—C28 | 1.506 (9) |
C5—C6 | 1.512 (7) | C28—C29 | 1.50 (1) |
C7—C8 | 1.383 (6) | C29—C30 | 1.495 (8) |
C7—C12 | 1.376 (5) | C31—C32 | 1.465 (6) |
C7—B1 | 1.600 (5) | C32—C33 | 1.547 (7) |
C8—C9 | 1.388 (6) | C32—C34 | 1.506 (5) |
C9—C10 | 1.35 (1) | C35—C36 | 1.34 (1) |
C10—C11 | 1.33 (1) | C35—C37i | 1.36 (1) |
C11—C12 | 1.407 (7) | C36—C37 | 1.34 (1) |
C13—C14 | 1.392 (5) | ||
B1—O1—B2 | 121.2 (3) | C24—C19—B3 | 121.2 (3) |
B2—O2—B3 | 118.4 (3) | C19—C20—C21 | 121.3 (4) |
B1—O3—B3 | 121.2 (3) | C20—C21—C22 | 118.8 (5) |
N1—O4—B1 | 114.2 (2) | C21—C22—C23 | 121.1 (6) |
O4—N1—C1 | 113.6 (2) | C22—C23—C24 | 120.2 (6) |
O5—N2—C25 | 115.3 (3) | C19—C24—C23 | 121.5 (4) |
O5—N2—C31 | 123.1 (3) | N2—C25—C26 | 111.2 (3) |
C25—N2—C31 | 121.6 (3) | N2—C25—C30 | 109.1 (3) |
N1—C1—C2 | 107.9 (2) | C26—C25—C30 | 111.1 (3) |
N1—C1—C6 | 110.9 (3) | C25—C26—C27 | 111.5 (4) |
C2—C1—C6 | 111.3 (3) | C26—C27—C28 | 110.6 (5) |
C1—C2—C3 | 110.1 (3) | C27—C28—C29 | 111.8 (5) |
C2—C3—C4 | 111.8 (4) | C28—C29—C30 | 112.8 (5) |
C3—C4—C5 | 111.2 (4) | C25—C30—C29 | 109.9 (4) |
C4—C5—C6 | 112.3 (4) | N2—C31—C32 | 123.9 (3) |
C1—C6—C5 | 110.0 (3) | C31—C32—C33 | 110.7 (4) |
C8—C7—C12 | 116.2 (3) | C31—C32—C34 | 109.7 (4) |
C8—C7—B1 | 121.9 (3) | C33—C32—C34 | 110.6 (4) |
C12—C7—B1 | 121.8 (4) | C36—C35—C37i | 119.8 (7) |
C7—C8—C9 | 122.1 (4) | C35—C36—C37 | 121.6 (6) |
C8—C9—C10 | 119.7 (6) | C35i—C37—C36 | 118.6 (7) |
C9—C10—C11 | 120.4 (6) | O1—B1—O3 | 111.2 (3) |
C10—C11—C12 | 120.4 (5) | O1—B1—O4 | 107.5 (3) |
C7—C12—C11 | 121.0 (5) | O1—B1—C7 | 113.1 (3) |
C14—C13—C18 | 116.0 (3) | O3—B1—O4 | 107.4 (3) |
C14—C13—B2 | 122.1 (3) | O3—B1—C7 | 112.4 (3) |
C18—C13—B2 | 121.9 (4) | O4—B1—C7 | 104.8 (2) |
C13—C14—C15 | 122.4 (4) | O1—B2—O2 | 121.0 (4) |
C14—C15—C16 | 120.2 (4) | O1—B2—C13 | 120.9 (4) |
C15—C16—C17 | 120.0 (5) | O2—B2—C13 | 118.1 (3) |
C16—C17—C18 | 119.0 (4) | O2—B3—O3 | 120.7 (3) |
C13—C18—C17 | 122.4 (4) | O2—B3—C19 | 117.7 (3) |
C20—C19—C24 | 117.1 (4) | O3—B3—C19 | 121.5 (4) |
C20—C19—B3 | 121.6 (4) |
Symmetry code: (i) −x+2, −y+1, −z+1. |
Triphenylboroxin and N-cyclohexyl-C-(2-propyl)nitrone form the 1:1 B–O–N adduct (I). B,N-Betainic complexes of this type, which are readily obtained as crystalline compounds from boroxins and nitrones [a series of various nitrone–triphenylboroxin 1:1 complexes has been synthesized (Lubkowitz, 1992)], correspond with other nitrone adducts of arylboronates (Paetzold et al., 1976; Kliegel, Preu et al., 1985) and diarylborinates (Kliegel, Lauterbach et al., 1987; Kliegel, Metge et al., 1997, 1998a,b; Kliegel et al., 2000, 2001). Addition of an equimolar amount of N-cyclohexylhydroxylamine to (I) was expected to give the complex (II), a double addition product of the nitrone as well as the hydroxylamine, the latter presumably in its N-oxide form, as recently was established for the B–O–N complex from triphenylboroxin and N,N-diethylhydoxylamine (Kliegel et al., 2002). An N—B coordination between the hydroxylamine and the boron compound could not be entirely excluded at this point, however. The crystalline reaction product (method A), which could also be obtained in a three component one-pot reaction from 3 mole quivalents (m.e.) of phenylboronic acid, 2 m.e. of N-cyclohexylhydroxylamine and 1 m.e. of isobutyraldehyde (method B), shows indeed the elemental analysis of (II). Some spectroscopic data, however, might call the adduct structure (II) into question. Comparing the IR spectra of (I) and of the adduct, the nitrone-C═N vibration is shifted from 1660 in (I) to about 1600 cm−1 in the adduct, and in the 1H NMR spectra, the signal of the N═CH methine H atom is displaced from δ = 6.97 in (I) to 6.73 p.p.m. in the adduct. Both the IR and the 1H NMR data of the nitrone portion of the adduct coincide roughly with those of free N-cyclohexylisobutyraldonitrone. The X-ray analysis establishes the molecular structure (III) for the adduct, representing a triphenylboroxin complex with N-cyclohexylhydroxylamine in its N-oxide form, and the N-cyclohexylisobutyraldonitrone linked by an O···H—N+ hydrogen bond to the hydoxylamine moiety [the crystals contain additionally (solvate) benzene from the solvent mixture used for obtaining single crystals].
Obviously the N-alkylhydroxylamine (N-oxide form) is the stronger nucleophile and substitutes for the azomethine N-oxide (nitrone). It seems that, in this case, a mono-coordination with the boroxin ring system is preferred over a bifold coordination as depicted in (II). This is in line with the findings about the complex formation between triphenylboroxin, N,N-diethylhydroxylamine, and N,N-dimethylformamide (Kliegel et al., 2002). Multiple coordination had been suggested previously for a nitrone adduct of triphenyboroxin (Paetzold et al., 1975).
The crystal structure of (III) contains three separate fragments: an N-cyclohexylhydroxylamine–triphenylboroxin complex, an N-cyclohexyl-C-(2-propyl)nitrone (Fig. 1), and a benzene molecule which lies on a centre of inversion. The six-membered boroxin ring has an approximate envelope conformation, the O1—B2—O2—B3—O3 ring portion forming a rather distorted plane, with B1 on the `flap' [a closer description is perhaps a boat conformation, with B1 and to a lesser extent O2 displaced from the plane of the other four atoms]. The ring dimensions are very similar to those in related boroxin ring systems containing one tetrahedral sp3 B atom (Kliegel, Motzkus et al., 1985; Kliegel et al., 2002); in particular, two of the O—B bonds are short [O1—B2 = 1.345 (4) Å and O3—B3 = 1.347 (4) Å], with a high amount of double-bond charcter by (pp)π back donation. The longest O—B distance [O4—B1 = 1.530 (4)%A] is found in the exocyclic donor–acceptor bond between the N-oxide form of N-cyclohexylhydroxylamine and the boroxin moiety, very much like in the N,N-diethylhydroxylamine adduct reported (Kliegel et al., 2002). The geometry of the nitrone molecule, which shows a Z configuration with near planarity around the C═N double bond [C31—N2 = 1.304 (5) Å] is typical for aldonitrones (Bedford et al., 1991, and references therein; Kliegel, Preu et al., 1985; Kliegel et al., 1998a,b; Olszewski & Stadnicka, 1995; Greci & Sgarabotto, 1984; Christensen et al., 1990).
The hydroxylamine–boroxin complex and the nitrone are linked by an N1—H1···O5 hydrogen bond: N···O = 2.751 (3), N—H = 0.98 (calculated H-atom site, assuming tetrahedral angles at N1), H···O = 1.80 Å and N—H···O = 163°. There is also an intra-boroxine contact which might represent a bifurcation of this hydrogen-bond system [N1—H1···O3: N···O = 2.904 (3), H···O = 2.45 Å and N—H···O = 108°]; this arrangement results in fairly short O5···B3 [2.860 (5) Å] and O5···O3 [2.991 (3) Å] distances. Finally, there is an inter-boroxin hydrogen bond [N1—H2···O4: N···O = 2.852 (3), N—H = 0.98, H···O = 2.03 Å and N—H···O = 141°].
The thermal motion is rather high, as evidenced by the ellipsoids in Fig. 1.