(S)-(+)-2-[2-(Biphenyl-2-yl)-1-methyl­ethyl]-4,5-dihydro-1H-imidazolium hydrogen oxalate

The (+)-enantiomer of 2-[2-(biphenyl-2-yl)-1-methylethyl]-4,5-dihydro-1H-imidazole is known to produce inter­esting hypotensive effects via inhibition of I₁-imidazoline receptors. The crystal structure of its hydrogen oxalate salt, C₁₈H₂₁N₂⁺·C₂HO₄^-, has now been determined at 170 K, allowing the assignment of the absolute configuration of the parent mol­ecule. The solid-state structure is stabilized by a network of hydrogen bonds between the ions.

Key indicators

• Single-crystal X-ray study
• T = 173 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.035
• wR factor = 0.083
• Data-to-parameter ratio = 9.1

checkCIF/PLATON results

No syntax errors found



Alert level A
PLAT027_ALERT_3_A _diffrn_reflns_theta_full (too) Low ............      60.54 Deg.

Author Response: 'see _publ_section_exptl_refinement'

Alert level B
THETM01_ALERT_3_B  The value of sine(theta_max)/wavelength is less than 0.575
            Calculated sin(theta_max)/wavelength =    0.5647
PLAT023_ALERT_3_B Resolution (too) Low [sin(th)/Lambda < 0.6].....      60.54 Deg.

Alert level C
PLAT063_ALERT_3_C Crystal Probably too Large for Beam Size .......       0.70 mm
PLAT250_ALERT_2_C Large U3/U1 Ratio for Average U(i,j) Tensor ....       2.48
PLAT350_ALERT_3_C Short   C-H Bond (0.96A)   C18    -   H182   ...       0.84 Ang.
PLAT355_ALERT_3_C Long    O-H Bond (0.82A)   O1     -   H1O    ...       1.01 Ang.
PLAT369_ALERT_2_C Long   C(sp2)-C(sp2) Bond  C19    -   C20    ...       1.53 Ang.
PLAT790_ALERT_4_C Centre of Gravity not Within Unit Cell: Resd.  #          1
              C18 H21 N2

Alert level G
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           60.54
           From the CIF: _reflns_number_total               2761
           Count of symmetry unique reflns         1497
           Completeness (_total/calc)            184.44%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured      1264
           Fraction of Friedel pairs measured     0.844
           Are heavy atom types Z>Si present         no

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

   0 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
   6 ALERT type 3 Indicator that the structure quality may be low
   2 ALERT type 4 Improvement, methodology, query or suggestion

---

Computing details

Data collection: CrysAlis CCD (Oxford Diffraction, 2001); cell refinement: CrysAlis CCD; data reduction: CrysAlis RED (Oxford Diffraction, 2001); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: Please provide missing details.

(S)-(+)-2-(2-biphenyl-2-yl-1-methylethyl)-4,5-dihydro-1H-imidazolium hydrogen oxalate

Crystal data

C18H21N2^+·C2HO4^−	F(000) = 376
Mr = 354.40	Dx = 1.262 Mg m^−3
Monoclinic, P21	Cu Kα radiation, λ = 1.54180 Å
Hall symbol: P 2yb	Cell parameters from 4415 reflections
a = 9.4761 (6) Å	θ = 6.0–40.0°
b = 10.0886 (6) Å	µ = 0.72 mm^−1
c = 10.5018 (6) Å	T = 173 K
β = 111.697 (6)°	Elongated plate, colourless
V = 932.85 (10) Å^3	0.70 × 0.35 × 0.10 mm
Z = 2

Data collection

Oxford Excalibur PX Ultra CCD area-detector diffractometer	2761 independent reflections
Radiation source: fine-focus sealed tube	2497 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.051
ω scans	θmax = 60.5°, θmin = 5.0°
Absorption correction: multi-scan (SADABS; Sheldrick, 1986)	h = −10→10
Tmin = 0.698, Tmax = 0.930	k = −11→11
10735 measured reflections	l = −11→11

Refinement

Refinement on F^2	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	Only H-atom coordinates refined
R[F^2 > 2σ(F^2)] = 0.035	w = 1/[σ^2(Fo^2) + (0.0587P)^2] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.083	(Δ/σ)max < 0.001
S = 0.99	Δρmax = 0.14 e Å^−3
2761 reflections	Δρmin = −0.16 e Å^−3
302 parameters	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
1 restraint	Extinction coefficient: 0.0163 (18)
Primary atom site location: structure-invariant direct methods	Absolute structure: Flack & Bernardinelli (1999), with 1282 Friedel pairs
Secondary atom site location: difference Fourier map	Absolute structure parameter: −0.1 (2)

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	0.4289 (2)	0.32165 (19)	−0.31022 (19)	0.0296 (5)
C2	0.2940 (2)	0.27528 (19)	−0.41125 (18)	0.0294 (4)
C3	0.2787 (2)	0.2848 (2)	−0.5486 (2)	0.0367 (5)
H3	0.185 (3)	0.248 (2)	−0.616 (2)	0.044*
C4	0.3870 (2)	0.3428 (3)	−0.5875 (2)	0.0439 (6)
H4	0.380 (3)	0.346 (3)	−0.681 (3)	0.053*
C5	0.5166 (3)	0.3929 (3)	−0.4880 (2)	0.0483 (6)
H5	0.589 (3)	0.433 (3)	−0.515 (3)	0.058*
C6	0.5377 (2)	0.3812 (2)	−0.3507 (2)	0.0408 (5)
H6	0.634 (3)	0.414 (3)	−0.281 (3)	0.049*
C7	0.1634 (2)	0.2239 (2)	−0.37895 (18)	0.0307 (5)
C8	0.0917 (2)	0.3030 (3)	−0.3129 (2)	0.0395 (5)
H8	0.126 (3)	0.392 (3)	−0.284 (2)	0.047*
C9	−0.0372 (2)	0.2600 (3)	−0.2929 (2)	0.0506 (6)
H9	−0.084 (3)	0.310 (3)	−0.243 (3)	0.061*
C10	−0.0963 (3)	0.1364 (3)	−0.3379 (3)	0.0565 (7)
H10	−0.185 (3)	0.111 (3)	−0.328 (3)	0.068*
C11	−0.0251 (3)	0.0553 (3)	−0.4011 (3)	0.0514 (6)
H11	−0.061 (3)	−0.038 (3)	−0.432 (3)	0.062*
C12	0.1032 (2)	0.0988 (2)	−0.4228 (2)	0.0403 (5)
H12	0.156 (3)	0.043 (3)	−0.467 (3)	0.048*
C13	0.4664 (2)	0.3028 (2)	−0.15730 (19)	0.0290 (4)
H131	0.376 (2)	0.286 (2)	−0.137 (2)	0.035*
H132	0.514 (2)	0.387 (2)	−0.110 (2)	0.035*
C14	0.5777 (2)	0.1869 (2)	−0.1021 (2)	0.0341 (5)
H14	0.661 (3)	0.199 (2)	−0.131 (2)	0.041*
C15	0.5033 (3)	0.0521 (2)	−0.1523 (3)	0.0505 (6)
H151	0.587 (3)	−0.019 (3)	−0.113 (3)	0.076*
H152	0.468 (3)	0.053 (3)	−0.256 (3)	0.076*
H153	0.410 (4)	0.040 (3)	−0.120 (3)	0.076*
C16	0.64205 (19)	0.19010 (19)	0.05072 (18)	0.0281 (4)
N1	0.56109 (19)	0.1842 (2)	0.12779 (17)	0.0384 (5)
H1N	0.460 (3)	0.189 (2)	0.099 (2)	0.046*
C17	0.6587 (2)	0.1922 (3)	0.2730 (2)	0.0399 (5)
H171	0.625 (3)	0.262 (3)	0.317 (2)	0.048*
H172	0.655 (3)	0.114 (3)	0.318 (3)	0.048*
C18	0.8142 (2)	0.2119 (3)	0.2674 (2)	0.0417 (5)
H181	0.882 (3)	0.146 (3)	0.323 (3)	0.050*
H182	0.850 (3)	0.287 (3)	0.294 (3)	0.050*
N2	0.78654 (17)	0.19901 (19)	0.12295 (17)	0.0355 (4)
H2N	0.849 (3)	0.213 (2)	0.088 (2)	0.043*
O1	−0.01478 (16)	0.02614 (14)	−0.00863 (18)	0.0404 (4)
H1O	−0.028 (3)	−0.070 (3)	−0.039 (3)	0.061*
O2	0.22838 (17)	0.00075 (16)	0.0180 (2)	0.0591 (5)
O3	0.03193 (14)	0.27761 (14)	0.06033 (15)	0.0392 (4)
O4	0.26684 (13)	0.26723 (14)	0.06190 (15)	0.0389 (4)
C19	0.1235 (2)	0.0687 (2)	0.0178 (2)	0.0316 (5)
C20	0.14339 (19)	0.2176 (2)	0.04961 (18)	0.0286 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0290 (10)	0.0337 (10)	0.0261 (11)	0.0026 (8)	0.0103 (8)	0.0004 (8)
C2	0.0263 (9)	0.0321 (10)	0.0268 (10)	0.0057 (9)	0.0064 (7)	0.0019 (9)
C3	0.0301 (10)	0.0494 (13)	0.0272 (11)	0.0058 (10)	0.0064 (9)	−0.0016 (10)
C4	0.0391 (13)	0.0666 (15)	0.0274 (12)	0.0063 (11)	0.0141 (10)	0.0029 (11)
C5	0.0402 (12)	0.0722 (16)	0.0394 (14)	−0.0065 (12)	0.0228 (11)	0.0061 (12)
C6	0.0331 (11)	0.0555 (14)	0.0320 (12)	−0.0051 (10)	0.0100 (10)	−0.0014 (11)
C7	0.0242 (9)	0.0391 (11)	0.0212 (10)	0.0029 (9)	−0.0006 (8)	0.0072 (9)
C8	0.0293 (11)	0.0509 (14)	0.0352 (13)	0.0025 (10)	0.0083 (9)	0.0022 (10)
C9	0.0314 (11)	0.0805 (19)	0.0403 (13)	0.0019 (13)	0.0137 (10)	0.0028 (13)
C10	0.0288 (12)	0.095 (2)	0.0392 (15)	−0.0160 (14)	0.0054 (11)	0.0146 (14)
C11	0.0392 (13)	0.0611 (16)	0.0400 (13)	−0.0177 (12)	−0.0014 (11)	0.0085 (12)
C12	0.0336 (11)	0.0458 (13)	0.0309 (12)	−0.0024 (10)	−0.0006 (9)	0.0027 (10)
C13	0.0260 (10)	0.0362 (12)	0.0235 (10)	0.0005 (9)	0.0077 (8)	−0.0008 (9)
C14	0.0250 (10)	0.0530 (13)	0.0233 (11)	0.0079 (9)	0.0078 (8)	−0.0010 (10)
C15	0.0659 (16)	0.0413 (13)	0.0309 (13)	0.0145 (13)	0.0023 (12)	−0.0069 (11)
C16	0.0190 (9)	0.0356 (11)	0.0279 (11)	0.0023 (8)	0.0064 (8)	−0.0007 (9)
N1	0.0184 (8)	0.0696 (13)	0.0250 (9)	0.0026 (8)	0.0053 (7)	−0.0006 (9)
C17	0.0352 (11)	0.0564 (15)	0.0250 (11)	0.0002 (11)	0.0074 (9)	−0.0017 (11)
C18	0.0281 (11)	0.0543 (14)	0.0332 (12)	−0.0040 (11)	0.0001 (9)	−0.0009 (12)
N2	0.0185 (8)	0.0572 (11)	0.0303 (9)	−0.0009 (8)	0.0085 (7)	0.0053 (8)
O1	0.0280 (7)	0.0320 (8)	0.0638 (10)	−0.0018 (6)	0.0199 (7)	−0.0029 (7)
O2	0.0283 (8)	0.0439 (10)	0.0982 (14)	0.0084 (7)	0.0155 (9)	−0.0096 (9)
O3	0.0277 (7)	0.0327 (8)	0.0632 (10)	0.0012 (6)	0.0240 (6)	−0.0011 (7)
O4	0.0231 (7)	0.0443 (9)	0.0498 (9)	−0.0038 (6)	0.0141 (6)	−0.0054 (7)
C19	0.0219 (10)	0.0369 (11)	0.0329 (11)	0.0042 (9)	0.0065 (8)	0.0059 (9)
C20	0.0192 (9)	0.0361 (11)	0.0299 (10)	0.0011 (8)	0.0085 (8)	0.0011 (8)

Geometric parameters (Å, º)

C1—C6	1.389 (3)	C13—H132	1.00 (2)
C1—C2	1.406 (3)	C14—C16	1.492 (3)
C1—C13	1.523 (3)	C14—C15	1.532 (3)
C2—C3	1.399 (3)	C14—H14	0.95 (2)
C2—C7	1.492 (3)	C15—H151	1.04 (3)
C3—C4	1.368 (3)	C15—H152	1.02 (3)
C3—H3	0.98 (2)	C15—H153	1.07 (3)
C4—C5	1.381 (3)	C16—N2	1.300 (2)
C4—H4	0.96 (3)	C16—N1	1.306 (2)
C5—C6	1.385 (3)	N1—C17	1.464 (3)
C5—H5	0.93 (3)	N1—H1N	0.89 (2)
C6—H6	0.99 (3)	C17—C18	1.510 (3)
C7—C8	1.389 (3)	C17—H171	0.95 (3)
C7—C12	1.392 (3)	C17—H172	0.93 (3)
C8—C9	1.383 (3)	C18—N2	1.447 (3)
C8—H8	0.97 (3)	C18—H181	0.96 (3)
C9—C10	1.377 (4)	C18—H182	0.83 (3)
C9—H9	0.94 (3)	N2—H2N	0.81 (3)
C10—C11	1.377 (4)	O1—C19	1.307 (2)
C10—H10	0.92 (3)	O1—H1O	1.01 (3)
C11—C12	1.389 (3)	O2—C19	1.207 (2)
C11—H11	1.01 (3)	O3—C20	1.258 (2)
C12—H12	0.97 (3)	O4—C20	1.235 (2)
C13—C14	1.537 (3)	C19—C20	1.536 (3)
C13—H131	0.97 (2)
C6—C1—C2	118.93 (18)	H131—C13—H132	107.9 (18)
C6—C1—C13	117.82 (18)	C16—C14—C15	110.01 (18)
C2—C1—C13	123.15 (17)	C16—C14—C13	109.87 (15)
C3—C2—C1	118.31 (17)	C15—C14—C13	112.42 (17)
C3—C2—C7	118.67 (16)	C16—C14—H14	106.5 (13)
C1—C2—C7	122.92 (16)	C15—C14—H14	109.3 (14)
C4—C3—C2	122.26 (19)	C13—C14—H14	108.6 (14)
C4—C3—H3	121.3 (14)	C14—C15—H151	107.0 (16)
C2—C3—H3	116.5 (14)	C14—C15—H152	106.5 (19)
C3—C4—C5	119.1 (2)	H151—C15—H152	110 (2)
C3—C4—H4	122.7 (15)	C14—C15—H153	108.7 (18)
C5—C4—H4	118.1 (14)	H151—C15—H153	113 (2)
C4—C5—C6	120.1 (2)	H152—C15—H153	111 (2)
C4—C5—H5	119.0 (17)	N2—C16—N1	112.01 (17)
C6—C5—H5	120.9 (17)	N2—C16—C14	123.57 (17)
C5—C6—C1	121.2 (2)	N1—C16—C14	124.42 (17)
C5—C6—H6	118.9 (14)	C16—N1—C17	110.69 (16)
C1—C6—H6	119.9 (14)	C16—N1—H1N	126.3 (15)
C8—C7—C12	118.0 (2)	C17—N1—H1N	122.2 (15)
C8—C7—C2	120.96 (18)	N1—C17—C18	102.50 (17)
C12—C7—C2	120.8 (2)	N1—C17—H171	110.3 (14)
C9—C8—C7	121.2 (2)	C18—C17—H171	115.0 (15)
C9—C8—H8	117.0 (14)	N1—C17—H172	110.7 (16)
C7—C8—H8	121.7 (14)	C18—C17—H172	110.7 (15)
C10—C9—C8	120.2 (3)	H171—C17—H172	108 (2)
C10—C9—H9	117.1 (17)	N2—C18—C17	103.18 (16)
C8—C9—H9	122.6 (17)	N2—C18—H181	113.2 (15)
C9—C10—C11	119.6 (2)	C17—C18—H181	109.2 (14)
C9—C10—H10	119.3 (18)	N2—C18—H182	109.1 (18)
C11—C10—H10	121.1 (18)	C17—C18—H182	113.0 (18)
C10—C11—C12	120.4 (3)	H181—C18—H182	109 (2)
C10—C11—H11	122.9 (15)	C16—N2—C18	111.19 (16)
C12—C11—H11	116.7 (15)	C16—N2—H2N	122.1 (17)
C11—C12—C7	120.6 (2)	C18—N2—H2N	125.1 (17)
C11—C12—H12	122.1 (15)	C19—O1—H1O	112.2 (15)
C7—C12—H12	117.3 (15)	O2—C19—O1	125.1 (2)
C1—C13—C14	110.63 (15)	O2—C19—C20	121.35 (17)
C1—C13—H131	112.0 (12)	O1—C19—C20	113.59 (16)
C14—C13—H131	108.8 (13)	O4—C20—O3	126.15 (18)
C1—C13—H132	107.8 (12)	O4—C20—C19	117.07 (16)
C14—C13—H132	109.6 (12)	O3—C20—C19	116.78 (16)
C6—C1—C2—C3	3.4 (3)	C8—C7—C12—C11	0.2 (3)
C13—C1—C2—C3	−172.96 (18)	C2—C7—C12—C11	−175.32 (18)
C6—C1—C2—C7	−172.90 (19)	C6—C1—C13—C14	−75.8 (2)
C13—C1—C2—C7	10.7 (3)	C2—C1—C13—C14	100.6 (2)
C1—C2—C3—C4	−3.1 (3)	C1—C13—C14—C16	166.34 (16)
C7—C2—C3—C4	173.4 (2)	C1—C13—C14—C15	−70.8 (2)
C2—C3—C4—C5	0.6 (4)	C15—C14—C16—N2	114.5 (2)
C3—C4—C5—C6	1.6 (4)	C13—C14—C16—N2	−121.3 (2)
C4—C5—C6—C1	−1.1 (4)	C15—C14—C16—N1	−65.5 (3)
C2—C1—C6—C5	−1.4 (3)	C13—C14—C16—N1	58.8 (3)
C13—C1—C6—C5	175.2 (2)	N2—C16—N1—C17	1.2 (3)
C3—C2—C7—C8	−117.3 (2)	C14—C16—N1—C17	−178.92 (19)
C1—C2—C7—C8	59.0 (3)	C16—N1—C17—C18	3.1 (3)
C3—C2—C7—C12	58.0 (2)	N1—C17—C18—N2	−5.6 (3)
C1—C2—C7—C12	−125.7 (2)	N1—C16—N2—C18	−5.2 (3)
C12—C7—C8—C9	−0.9 (3)	C14—C16—N2—C18	174.8 (2)
C2—C7—C8—C9	174.54 (18)	C17—C18—N2—C16	6.8 (3)
C7—C8—C9—C10	0.4 (3)	O2—C19—C20—O4	7.0 (3)
C8—C9—C10—C11	0.9 (4)	O1—C19—C20—O4	−172.90 (18)
C9—C10—C11—C12	−1.7 (4)	O2—C19—C20—O3	−173.18 (19)
C10—C11—C12—C7	1.1 (3)	O1—C19—C20—O3	6.9 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1O···O3^i	1.01 (3)	1.55 (3)	2.558 (2)	171 (3)
N1—H1N···O4	0.89 (2)	1.90 (3)	2.744 (2)	158 (2)
N2—H2N···O3^ii	0.81 (3)	1.98 (3)	2.757 (2)	162 (2)

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