Redetermination of (6R,7S,9S,11S)-(-)-sparteinium monoperchlorate

The structure of the title compound, C₁₅H₂₇N₂⁺·ClO₄^-, consists of a monoprotonated sparteinium cation and a perchlorate anion. The two tertiary N atoms of the cation, one perchlorate O atom and a H atom form a bifurcated hydrogen bond, the four hydrogen-bonding atoms being nearly in the same plane.

S1. Comment

The crystal structure of sparteinium monoperchlorate, (I), has been determined previously (Borovyak et al., 1973). However, the refinement of the structure was not complete and the structural data collected was very limited; the H-atom and ClO₄^- positions were not determined. We redetermined the crystal structure of (I) for two reasons: (i) there is a need for the complete and well refined crystal structure of (-)-sparteine in order to understand the structural features of many previously reported metal–sparteine complexes (Kim et al., 2001; Kuroda & Mason, 1979; Lee et al., 1998, 2000, 2002; Lopez et al., 1998; Motevalli et al., 1993), and (ii) compound (I) has attracted research attention and has been intensively utilized in medicinal chemistry (Cady et al., 1977) and asymmetric synthesis (Beak et al., 1996; Kretchmer, 1972; Mason & Peacock, 1973).

The neutral dialkaloid sparteine structure is composed of four rings, two of which (A and B) form a double-chair system of trans-quinolizidine, which is relatively resistant to conformation–configuration change upon protonation. However, the second system of rings (C and D) is much more susceptible to inversion on an N-donor atom (N16) and inversion may occur in a trans-boat-chair or cis-double-chair conformation. The outer rings (A and D) are directed upward (cis) or downward (trans) with respect to the methylene bridge, i.e. the H atoms on C6 and C11 are in trans–trans or cis–cis positions, respectively. The conformation and configuration of the spartenium cation in (I) was found to be the same as reportedpreviously (Borovyak et al., 1973).

Based on ¹³C NMR and IR studies, Boczon & Koziol (1997) suggested that sparteine and its isomers and derivatives can undergo conformational–configurational rearrangements in solution. It is well known that, in the case of the monoprotonated base, viz. C₁₅H₂₇N₂⁺, in solution, a tautomeric equilibrium takes place, with the contributions of cations N1—H1···N16 and N1···H1—N16 being 1:1.25 (Boczon & Koziol, 1997). However, in the solid state, the H atom bonds to atom N1 and the compound crystallizes exclusively in the N1—H1···N16 tautomeric form (Fig. 1 and Table 1). The H atom also interacts with perchlorate atom O2 to form a rare three-centered hydrogen bond (bifurcated hydrogen bonding), as shown in Fig. 2. The four hydrogen-bonding atoms (N1, N16, H1 and O2) are nearly in the same plane, as the sum of three angles N1—H1···N16, N1—H1···O2 and N16···H1···O2 is approximately 358°. Atom H1 on protonated atom N1 is axial relative to rings A and B, as is usually observed (Boczon & Koziol, 1997). The N1···N16 distance is 2.755 (5) Å, which is considerably less than the sum of the van der Waals radii of 3.16 Å and confirms the participation of the two N atoms in a bifurcated intramolecular hydrogen bond (Table 2).

The (-)-sparteine conformation in metal(II)–(-)-sparteine complexes is almost identical to the conformations in free and monoprotonated (-)-sparteine. In the complexes, there is a relationship between N—M—N bite angle and M—N distance, i.e. if the N—M—N bite angle is smaller then the M—N bond is longer (Lee et al., 2002). In fact, the N—M—N bite angle in the metal(II)–(-)-sparteine complexes affects the N···N distance of the coordinated (-)-sparteine ligand. The N1···N16 distance of (I) is shorter than those observed in the metal complexes due to the intramolecular N—H···N hydrogen bond and the cation size.

S2. Experimental

The precursor complex, [Cu(C₁₅H₂₆N₂)(ClO₄)₂] was prepared by mixing a solution of copper(II) perchlorate in ethanol–triethylorthoformate (3:1 v/v) with a stoichiometric amount of (-)-l-sparteine, (6R,7S,9S,11S)-C₁₅H₂₆N₂. The resulting dark-blue solution was added to a stoichiometric amount of potassium fluoride. CuF₂ salts were immediately precipitated and were removed from the solution by filtration. Single crystals of (I) were obtained by slow evaporation from the solution at room temperature. Analysis calculated for C₁₅H₂₇ClN₂O₄: C 53.81, H 8.13, N 8.37%; found: C 53.63, H 8.00, N 8.34%.

S3. Refinement

The positional parameters of the H atoms were calculated geometrically (C—H = 0.96–0.98 Å) and constrained to ride on their parent atoms, with U_iso(H) = 1.2U_eq(CH and CH₂). The H atom on N1 was located in a difference map and refined isotropically.

Computing details

Data collection: CAD-4 EXPRESS (Enraf-Nonius, 1994); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

Fig. 1. ORTEP-3 diagram (Farrugia, 1997) of (I), showing the atom-numbering scheme and 30% probability ellipsoids. Fig. 2. A view (Farrugia, 1997) of hydrogen bonding (dashed lines) in (I), showing selected atom labels and 30% probability ellipsoids [symmetry code: (i) 1/2 + x, 1/2 - y, 1 - z].

(6R,7S,9S,11S)-Sparteinium monoperchlorate

Crystal data

C15H27N2^+·ClO4^−	F(000) = 720
Mr = 334.84	Dx = 1.348 Mg m^−3
Orthorhombic, P212121	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 25 reflections
a = 8.029 (2) Å	θ = 11.3–14.1°
b = 13.4196 (16) Å	µ = 0.25 mm^−1
c = 15.3094 (16) Å	T = 293 K
V = 1649.6 (5) Å^3	Block, yellow
Z = 4	0.33 × 0.3 × 0.3 mm

Data collection

Enraf-Nonius CAD-4 diffractometer	1559 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.012
Graphite monochromator	θmax = 27.5°, θmin = 2.0°
non–profiled ω/2θ scans	h = −1→10
Absorption correction: ψ scan (North et al., 1968)	k = 0→17
Tmin = 0.887, Tmax = 0.926	l = 0→19
2438 measured reflections	3 standard reflections every 300 min
2402 independent reflections	intensity decay: 1%

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)] = 0.052	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.128	w = 1/[σ^2(Fo^2) + (0.0533P)^2 + 0.3075P] where P = (Fo^2 + 2Fc^2)/3
S = 1.02	(Δ/σ)max < 0.001
2402 reflections	Δρmax = 0.25 e Å^−3
203 parameters	Δρmin = −0.24 e Å^−3
0 restraints	Absolute structure: Flack (1983), 232 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.00 (13)

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	0.1462 (4)	0.5025 (3)	0.43971 (19)	0.0366 (7)
H1	0.242 (5)	0.505 (4)	0.418 (3)	0.044 (11)*
N16	0.3437 (4)	0.5980 (2)	0.3186 (2)	0.0373 (8)
C2	0.1250 (7)	0.4216 (3)	0.5064 (3)	0.0494 (12)
H2A	0.0163	0.4275	0.5335	0.059*
H2B	0.2087	0.4289	0.5516	0.059*
C3	0.1414 (7)	0.3196 (3)	0.4646 (3)	0.0575 (13)
H3A	0.2542	0.3109	0.4432	0.069*
H3B	0.1205	0.2686	0.5081	0.069*
C4	0.0204 (7)	0.3072 (3)	0.3898 (3)	0.0592 (14)
H4A	−0.0928	0.3090	0.4117	0.071*
H4B	0.0381	0.2432	0.3618	0.071*
C5	0.0457 (7)	0.3906 (3)	0.3235 (3)	0.0494 (12)
H5A	−0.0340	0.3830	0.2763	0.059*
H5B	0.1566	0.3856	0.2989	0.059*
C6	0.0237 (5)	0.4927 (3)	0.3652 (2)	0.0376 (8)
H6	−0.0886	0.4953	0.3902	0.045*
C7	0.0398 (6)	0.5793 (3)	0.3018 (3)	0.0434 (11)
H7	−0.0477	0.5730	0.2575	0.052*
C8	0.0140 (6)	0.6777 (3)	0.3508 (3)	0.0465 (11)
H8A	0.0173	0.7332	0.3102	0.056*
H8B	−0.0933	0.6778	0.3799	0.056*
C9	0.1532 (6)	0.6871 (3)	0.4173 (3)	0.0426 (10)
H9	0.1391	0.7504	0.4484	0.051*
C10	0.1362 (6)	0.6029 (3)	0.4833 (2)	0.0430 (11)
H10A	0.2242	0.6083	0.5265	0.052*
H10B	0.0303	0.6089	0.5134	0.052*
C11	0.3235 (5)	0.6882 (3)	0.3726 (3)	0.0401 (9)
H11	0.4070	0.6840	0.4192	0.048*
C12	0.3593 (6)	0.7841 (3)	0.3225 (3)	0.0495 (11)
H12A	0.3517	0.8405	0.3619	0.059*
H12B	0.2765	0.7928	0.2770	0.059*
C13	0.5329 (6)	0.7811 (3)	0.2815 (3)	0.0603 (14)
H13A	0.5495	0.8401	0.2459	0.072*
H13B	0.6165	0.7810	0.3272	0.072*
C14	0.5527 (7)	0.6893 (3)	0.2256 (3)	0.0564 (12)
H14A	0.6665	0.6851	0.2047	0.068*
H14B	0.4798	0.6940	0.1753	0.068*
C15	0.5104 (6)	0.5957 (3)	0.2776 (3)	0.0492 (12)
H15A	0.5166	0.5385	0.2389	0.059*
H15B	0.5936	0.5867	0.3229	0.059*
C17	0.2077 (5)	0.5847 (3)	0.2555 (3)	0.0440 (11)
H17A	0.2257	0.5239	0.2225	0.053*
H17B	0.2073	0.6400	0.2147	0.053*
Cl	0.10569 (12)	0.00084 (9)	0.46176 (7)	0.0495 (3)
O1	0.2009 (5)	−0.0724 (3)	0.5068 (2)	0.0729 (11)
O2	0.0187 (6)	0.0599 (3)	0.5240 (3)	0.0980 (14)
O3	−0.0101 (5)	−0.0503 (3)	0.4058 (2)	0.0923 (14)
O4	0.2127 (6)	0.0604 (3)	0.4112 (3)	0.1147 (16)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0334 (17)	0.0433 (17)	0.0332 (16)	0.000 (2)	0.0004 (14)	−0.0010 (18)
N16	0.0352 (18)	0.0418 (19)	0.0349 (16)	0.0020 (16)	0.0025 (16)	−0.0050 (15)
C2	0.049 (3)	0.059 (3)	0.040 (2)	−0.008 (3)	0.001 (2)	0.012 (2)
C3	0.061 (3)	0.046 (2)	0.066 (3)	−0.002 (3)	0.007 (3)	0.009 (3)
C4	0.065 (4)	0.047 (2)	0.066 (3)	−0.008 (3)	0.003 (3)	−0.003 (2)
C5	0.051 (3)	0.052 (2)	0.045 (2)	−0.007 (3)	−0.005 (2)	−0.009 (2)
C6	0.0322 (19)	0.045 (2)	0.0353 (18)	−0.002 (2)	−0.0041 (17)	0.000 (2)
C7	0.041 (2)	0.049 (2)	0.041 (2)	−0.002 (2)	−0.011 (2)	0.000 (2)
C8	0.037 (3)	0.048 (2)	0.054 (3)	0.007 (2)	0.001 (2)	0.006 (2)
C9	0.045 (3)	0.0334 (19)	0.050 (2)	0.003 (2)	0.006 (2)	−0.009 (2)
C10	0.042 (3)	0.051 (3)	0.036 (2)	−0.002 (2)	0.001 (2)	−0.0129 (19)
C11	0.037 (2)	0.043 (2)	0.041 (2)	0.001 (2)	−0.001 (2)	−0.010 (2)
C12	0.045 (3)	0.045 (2)	0.058 (3)	−0.003 (2)	0.007 (2)	−0.006 (2)
C13	0.052 (3)	0.054 (3)	0.075 (3)	−0.011 (3)	0.015 (3)	0.001 (2)
C14	0.054 (3)	0.057 (3)	0.058 (3)	−0.005 (3)	0.017 (3)	0.002 (2)
C15	0.043 (3)	0.052 (3)	0.053 (3)	0.006 (2)	0.007 (2)	−0.007 (2)
C17	0.055 (3)	0.043 (2)	0.033 (2)	−0.003 (2)	0.000 (2)	−0.0010 (19)
Cl	0.0376 (5)	0.0537 (5)	0.0572 (6)	0.0023 (7)	0.0040 (5)	0.0115 (6)
O1	0.074 (3)	0.067 (2)	0.078 (2)	0.017 (2)	−0.024 (2)	0.0033 (18)
O2	0.094 (3)	0.080 (2)	0.120 (3)	0.022 (3)	0.027 (3)	−0.015 (2)
O3	0.060 (3)	0.140 (4)	0.077 (2)	−0.012 (3)	−0.021 (2)	0.002 (2)
O4	0.094 (4)	0.120 (3)	0.130 (3)	−0.033 (3)	0.032 (3)	0.052 (3)

Geometric parameters (Å, º)

N1—C2	1.500 (5)	C8—H8B	0.9700
N1—C6	1.512 (5)	C9—C10	1.522 (5)
N1—C10	1.506 (5)	C9—C11	1.529 (6)
N1—H1	0.84 (4)	C9—H9	0.9800
N16—C11	1.475 (5)	C10—H10A	0.9700
N16—C15	1.479 (5)	C10—H10B	0.9700
N16—C17	1.469 (5)	C11—C12	1.526 (6)
C2—C3	1.516 (6)	C11—H11	0.9800
C2—H2A	0.9700	C12—C13	1.529 (6)
C2—H2B	0.9700	C12—H12A	0.9700
C3—C4	1.511 (7)	C12—H12B	0.9700
C3—H3A	0.9700	C13—C14	1.509 (6)
C3—H3B	0.9700	C13—H13A	0.9700
C4—C5	1.523 (6)	C13—H13B	0.9700
C4—H4A	0.9700	C14—C15	1.525 (5)
C4—H4B	0.9700	C14—H14A	0.9700
C5—C6	1.522 (5)	C14—H14B	0.9700
C5—H5A	0.9700	C15—H15A	0.9700
C5—H5B	0.9700	C15—H15B	0.9700
C6—C7	1.519 (5)	C17—H17A	0.9700
C6—H6	0.9800	C17—H17B	0.9700
C7—C17	1.525 (6)	Cl—O1	1.423 (3)
C7—C8	1.533 (5)	Cl—O2	1.423 (4)
C7—H7	0.9800	Cl—O3	1.439 (4)
C8—C9	1.518 (6)	Cl—O4	1.406 (4)
C8—H8A	0.9700
C2—N1—C6	112.2 (3)	C10—C9—C11	112.6 (4)
C2—N1—C10	109.9 (3)	C8—C9—H9	108.2
C6—N1—C10	112.2 (3)	C10—C9—H9	108.2
C2—N1—H1	114 (3)	C11—C9—H9	108.2
C6—N1—H1	107 (3)	N1—C10—C9	111.4 (3)
C10—N1—H1	101 (4)	N1—C10—H10A	109.3
C11—N16—C15	110.8 (3)	C9—C10—H10A	109.3
C11—N16—C17	112.7 (3)	N1—C10—H10B	109.3
C15—N16—C17	113.0 (3)	C9—C10—H10B	109.3
N1—C2—C3	110.9 (3)	H10A—C10—H10B	108.0
N1—C2—H2A	109.5	N16—C11—C12	112.9 (3)
C3—C2—H2A	109.5	N16—C11—C9	109.9 (3)
N1—C2—H2B	109.5	C12—C11—C9	113.7 (4)
C3—C2—H2B	109.5	N16—C11—H11	106.6
H2A—C2—H2B	108.1	C12—C11—H11	106.6
C4—C3—C2	111.3 (4)	C9—C11—H11	106.6
C4—C3—H3A	109.4	C11—C12—C13	110.9 (4)
C2—C3—H3A	109.4	C11—C12—H12A	109.5
C4—C3—H3B	109.4	C13—C12—H12A	109.5
C2—C3—H3B	109.4	C11—C12—H12B	109.5
H3A—C3—H3B	108.0	C13—C12—H12B	109.5
C3—C4—C5	109.8 (4)	H12A—C12—H12B	108.1
C3—C4—H4A	109.7	C14—C13—C12	110.5 (4)
C5—C4—H4A	109.7	C14—C13—H13A	109.6
C3—C4—H4B	109.7	C12—C13—H13A	109.6
C5—C4—H4B	109.7	C14—C13—H13B	109.6
H4A—C4—H4B	108.2	C12—C13—H13B	109.6
C4—C5—C6	111.5 (3)	H13A—C13—H13B	108.1
C4—C5—H5A	109.3	C13—C14—C15	110.7 (3)
C6—C5—H5A	109.3	C13—C14—H14A	109.5
C4—C5—H5B	109.3	C15—C14—H14A	109.5
C6—C5—H5B	109.3	C13—C14—H14B	109.5
H5A—C5—H5B	108.0	C15—C14—H14B	109.5
N1—C6—C7	111.1 (3)	H14A—C14—H14B	108.1
N1—C6—C5	108.6 (3)	N16—C15—C14	113.9 (4)
C7—C6—C5	114.3 (3)	N16—C15—H15A	108.8
N1—C6—H6	107.5	C14—C15—H15A	108.8
C7—C6—H6	107.5	N16—C15—H15B	108.8
C5—C6—H6	107.5	C14—C15—H15B	108.8
C6—C7—C17	114.1 (3)	H15A—C15—H15B	107.7
C6—C7—C8	109.6 (3)	N16—C17—C7	110.9 (3)
C17—C7—C8	107.8 (4)	N16—C17—H17A	109.5
C6—C7—H7	108.4	C7—C17—H17A	109.5
C17—C7—H7	108.4	N16—C17—H17B	109.5
C8—C7—H7	108.4	C7—C17—H17B	109.5
C7—C8—C9	107.5 (4)	H17A—C17—H17B	108.0
C9—C8—H8A	110.2	O1—Cl—O2	108.9 (2)
C7—C8—H8A	110.2	O1—Cl—O3	107.8 (2)
C9—C8—H8B	110.2	O1—Cl—O4	109.3 (3)
C7—C8—H8B	110.2	O2—Cl—O3	110.3 (3)
H8A—C8—H8B	108.5	O2—Cl—O4	110.6 (3)
C8—C9—C10	108.6 (4)	O3—Cl—O4	109.8 (3)
C8—C9—C11	111.0 (3)
C10—N1—C2—C3	−177.7 (4)	C8—C9—C10—N1	59.4 (5)
C6—N1—C2—C3	56.7 (5)	C11—C9—C10—N1	−63.9 (5)
N1—C2—C3—C4	−55.5 (5)	C17—N16—C11—C12	−73.6 (4)
C2—C3—C4—C5	55.8 (5)	C15—N16—C11—C12	54.1 (4)
C3—C4—C5—C6	−57.8 (5)	C17—N16—C11—C9	54.6 (4)
C2—N1—C6—C7	176.2 (3)	C15—N16—C11—C9	−177.7 (3)
C10—N1—C6—C7	51.9 (4)	C8—C9—C11—N16	−56.4 (4)
C2—N1—C6—C5	−57.3 (4)	C10—C9—C11—N16	65.6 (4)
C10—N1—C6—C5	178.5 (3)	C8—C9—C11—C12	71.3 (4)
C4—C5—C6—N1	57.8 (5)	C10—C9—C11—C12	−166.7 (3)
C4—C5—C6—C7	−177.5 (4)	N16—C11—C12—C13	−55.3 (5)
N1—C6—C7—C17	63.8 (4)	C9—C11—C12—C13	178.6 (4)
C5—C6—C7—C17	−59.5 (5)	C11—C12—C13—C14	54.4 (5)
N1—C6—C7—C8	−57.1 (4)	C12—C13—C14—C15	−53.6 (6)
C5—C6—C7—C8	179.5 (4)	C17—N16—C15—C14	73.7 (4)
C6—C7—C8—C9	63.3 (4)	C11—N16—C15—C14	−53.9 (4)
C17—C7—C8—C9	−61.4 (4)	C13—C14—C15—N16	54.5 (5)
C7—C8—C9—C10	−63.8 (4)	C11—N16—C17—C7	−58.0 (4)
C7—C8—C9—C11	60.5 (4)	C15—N16—C17—C7	175.4 (3)
C2—N1—C10—C9	−178.7 (4)	C6—C7—C17—N16	−61.2 (4)
C6—N1—C10—C9	−53.2 (5)	C8—C7—C17—N16	60.7 (4)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O2^i	0.84 (4)	2.54 (4)	3.155 (6)	130 (4)
N1—H1···N16	0.84 (4)	2.13 (5)	2.755 (5)	131 (4)

Symmetry code: (i) x+1/2, −y+1/2, −z+1.