1,3-Bis­(di­methyl­amino)-1-methyl­trimethinium hexa­fluoro­phosphate

The synthesis and structure of the title compound, N-[3-(di­methyl­amino)-1-methyl-2-propenyl­idene]-N-methyl­methanaminium hexa­fluoro­phosphate, [Me₂N{C(Me)(CH)₂}NMe₂]⁺·PF₆^- or C₈H₁₇N₂⁺·PF₆^-, are reported. The cation is close to planar and adopts an all-trans-configuration.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.007 Å
• R factor = 0.056
• wR factor = 0.185
• Data-to-parameter ratio = 9.9

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

General Notes



REFLT_03
         From the CIF: _diffrn_reflns_theta_max           25.99
         From the CIF: _reflns_number_total               1540
         Count of symmetry unique reflns         1540
         Completeness (_total/calc)            100.00%
         TEST3: Check Friedels for noncentro structure
         Estimate of Friedel pairs measured         0
         Fraction of Friedel pairs measured     0.000
         Are heavy atom types Z>Si present          yes
          WARNING: Large fraction of Friedel related reflns may
                   be needed to determine absolute structure

---

S1. Comment

Salts of the title cation have been prepared and characterized (Arnold & Zemlinka, 1959; Arnold, 1973), but a search of the Cambridge Structural Database (Allen & Kennard, 1993) shows that there have apparently been no crystal structure reports. The title salt, (1), was obtained as a by-product in the course of attempts to prepare the pyrrole-substituted pentamethinecyanine derivative (2).

The X-ray structural investigation of (1) shows the presence of discrete fully delocalized cations and hexafluorophosphate anions with unexceptional dimensions. The delocalized moiety (N1/C2/C3/C4/N5) of the cation is close to planar [maximum deviation 0.016 (4) Å for C3], and it adopts an all-trans configuration as has been suggested by others on the basis of NMR studies (Filleux-Blanchard et al., 1974) and found for the related cation [Me₂N(CH)₃NMe₂]⁺ in 1,3-bis(dimethylamino)trimethinium perchlorate (Matthews et al., 1973; Sieber et al., 1974). The C atoms of all five methyl substituents also lie close to the N1/C2/C3/C4/N5 plane of the cation [maximum deviation 0.156 (14) Å for C12].

S2. Experimental

A warm solution of pyridinium salt (3) (Ferguson & McAlees, 1990) (3.47 g, 10.0 mmol) in water (20 ml) was treated with an aqueous solution (25 ml) containing Me₂NH₂^+.Cl^- (9.00 g, 110 mmol) and sodium hydroxide (3.0 g, 75 mmol). A dark purple–brown precipitate formed immediately. Ethanol (20 ml) was added and the mixture was stirred and heated at the reflux for 2.5 h, then solvent was distilled to remove most of the ethanol. The resulting dark mixture was allowed to cool overnight and was then filtered to give an olive–brown solid (1.58 g after washing and drying; mainly 2,4-dinitroaniline) which was washed with warm water (3 × 10 ml). The combined filtrate and washings were washed with chloroform (3 × 30 ml) and treated with an aqueous solution (10 ml) of NH₄^+.PF₆^- (1.63 g, 10.0 mmol), whereupon a light yellow precipitate appeared. The aqueous mixture was then extracted with CH₂Cl₂(3 × 30 ml), and the combined extracts were dried (Na₂SO₄) and evaporated to leave an orange-yellow solid (1.89 g). Crystallization of this material from methanol gave (4) (0.70 g) as well formed straw-yellow prisms (m.p. 396.5–397.0 K). Concentration of the mother liquors and prolonged standing gave a further 0.51 g. of this material [total yield 42% based on (1)]. ¹H NMR (CD₃CN, 400 MHz) δ = 2.22 (s, C—Me), 3.01, 3.16, 3.23, 3.24 (each s, N—Me), 5.10 (d, J = 12.1 Hz, C2—H) and 7.74 (d, J = 12.1 Hz, C3—H).

S3. Refinement

Molecule (1) crystallized in the orthorhombic system; space group P2₁2₁2₁ from the systematic absences. No Friedel reflections were collected and the resulting Flack (1983) parameter [0.5 (3)] is indeterminate. H atoms were treated as riding atoms with C—H distances of 0.93 and 0.96 Å. The methyl groups at C11, C12 and C21 were each modelled using six H sites, each with occupancy 1/2, mutually offset by 60°.

Computing details

Data collection: CAD-4-PC Software (Nonius, 1992); cell refinement: SET4 and CELDIM (Nonius, 1992); data reduction: HELENA in PLATON (Spek, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976) and PLATON (Spek, 2001); software used to prepare material for publication: SHELXL97 and WORDPERFECT macro PREP8 (Ferguson, 2001).

Figures

Fig. 1. A view of (1) with the atomic numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. Only one orientation is shown for the disordered methyl H atoms at C11, C12 and C21.

1,3-Bis(dimethylamino)-1-methyl-trimethinium hexafluorophosphate or N-[3-(Dimethylamino)-1-methyl-2-propenylidene]-N-methylmethanaminium hexafluorophosphate

Crystal data

C8H17N2^+·PF6^−	Dx = 1.410 Mg m^−3
Mr = 286.21	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, P212121	Cell parameters from 25 reflections
a = 7.470 (4) Å	θ = 10.0–14.5°
b = 11.110 (3) Å	µ = 0.26 mm^−1
c = 16.242 (3) Å	T = 293 K
V = 1348.0 (8) Å^3	Plate, yellow
Z = 4	0.50 × 0.50 × 0.35 mm
F(000) = 592

Data collection

Nonius CAD-4 diffractometer	Rint = 0.0
Radiation source: fine-focus sealed X-ray tube	θmax = 26.0°, θmin = 2.2°
Graphite monochromator	h = −9→0
θ/2θ scans	k = −13→0
1540 measured reflections	l = −20→0
1540 independent reflections	3 standard reflections every 120 min
1042 reflections with I > 2σ(1)	intensity decay: 1.0%

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)] = 0.056	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.185	H-atom parameters constrained
S = 1.03	w = 1/[σ^2(Fo^2) + (0.1171P)^2 + 0.3108P] where P = (Fo^2 + 2Fc^2)/3
1540 reflections	(Δ/σ)max < 0.001
156 parameters	Δρmax = 0.25 e Å^−3
0 restraints	Δρmin = −0.23 e Å^−3

Special details

Geometry. Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane)

3.7944(0.0231) x + 8.0662 (0.0177) y + 7.5288 (0.0880) z = 7.4539 (0.0138) 3.79 (2)x + 8.066 (18)y + 7.52 (9)z = 7.454 (14)

* -0.015 (2) N1 * 0.014 (3) C2 * 0.016 (4) C3 * -0.014 (3) C4 * -0.001 (3) N5 0.032 (8) C11 - 0.156 (14) C12 0.120 (14) C21 - 0.021 (9) C51 0.069 (13) C52

Rms deviation of fitted atoms = 0.0133

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
N1	1.0805 (6)	0.2672 (4)	0.1572 (3)	0.0751 (11)
N5	0.6198 (6)	0.5486 (4)	0.0899 (3)	0.0748 (11)
C2	0.9329 (7)	0.3237 (4)	0.1750 (3)	0.0652 (11)
C3	0.8570 (7)	0.4091 (4)	0.1220 (3)	0.0663 (11)
H3	0.9182	0.4281	0.0739	0.080*
C4	0.6973 (7)	0.4664 (4)	0.1371 (3)	0.0690 (12)
H4	0.6377	0.4455	0.1852	0.083*
C11	1.1677 (9)	0.1800 (5)	0.2130 (4)	0.0981 (18)
H11A	1.2747	0.1497	0.1876	0.147*	0.50
H11B	1.0873	0.1144	0.2238	0.147*	0.50
H11C	1.1979	0.2192	0.2638	0.147*	0.50
H11D	1.0986	0.1725	0.2625	0.147*	0.50
H11E	1.2859	0.2077	0.2263	0.147*	0.50
H11F	1.1754	0.1030	0.1863	0.147*	0.50
C12	1.1693 (10)	0.2820 (6)	0.0779 (4)	0.114 (2)
H12A	1.2754	0.2333	0.0765	0.171*	0.50
H12B	1.2011	0.3650	0.0704	0.171*	0.50
H12C	1.0898	0.2574	0.0346	0.171*	0.50
H12D	1.1021	0.3371	0.0445	0.171*	0.50
H12E	1.1764	0.2055	0.0506	0.171*	0.50
H12F	1.2878	0.3130	0.0864	0.171*	0.50
C21	0.8494 (8)	0.2985 (5)	0.2581 (3)	0.0862 (16)
H21A	0.9180	0.2381	0.2862	0.129*	0.50
H21B	0.7290	0.2704	0.2507	0.129*	0.50
H21C	0.8483	0.3710	0.2902	0.129*	0.50
H21D	0.7455	0.3483	0.2652	0.129*	0.50
H21E	0.9346	0.3159	0.3008	0.129*	0.50
H21F	0.8153	0.2153	0.2612	0.129*	0.50
C51	0.4534 (8)	0.6023 (6)	0.1135 (4)	0.0957 (18)
H51A	0.4207	0.5749	0.1675	0.144*
H51B	0.3621	0.5797	0.0749	0.144*
H51C	0.4658	0.6883	0.1139	0.144*
C52	0.6994 (9)	0.5909 (6)	0.0136 (4)	0.0981 (18)
H52A	0.8191	0.6184	0.0241	0.147*
H52B	0.6294	0.6561	−0.0080	0.147*
H52C	0.7024	0.5263	−0.0256	0.147*
P1	0.31494 (19)	0.48016 (14)	0.37157 (9)	0.0784 (5)
F1	0.3907 (8)	0.4626 (6)	0.4610 (3)	0.163 (2)
F2	0.2151 (8)	0.3568 (4)	0.3859 (3)	0.1371 (17)
F3	0.1537 (7)	0.5496 (4)	0.4130 (3)	0.1397 (18)
F4	0.4054 (9)	0.6049 (5)	0.3572 (4)	0.196 (3)
F5	0.4763 (9)	0.4145 (7)	0.3339 (4)	0.201 (3)
F6	0.2231 (9)	0.4921 (5)	0.2850 (3)	0.157 (2)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.076 (3)	0.060 (2)	0.089 (3)	0.001 (2)	−0.001 (2)	−0.002 (2)
N5	0.076 (2)	0.074 (2)	0.075 (2)	0.011 (2)	−0.003 (2)	−0.006 (2)
C2	0.065 (3)	0.056 (2)	0.074 (3)	−0.004 (2)	0.001 (2)	−0.009 (2)
C3	0.066 (2)	0.062 (2)	0.071 (3)	0.000 (2)	0.002 (2)	−0.004 (2)
C4	0.067 (2)	0.072 (3)	0.068 (3)	−0.007 (2)	0.001 (2)	−0.012 (2)
C11	0.103 (4)	0.083 (3)	0.109 (4)	0.022 (4)	−0.011 (4)	0.000 (3)
C12	0.113 (5)	0.105 (4)	0.124 (5)	0.033 (5)	0.045 (5)	0.016 (4)
C21	0.085 (3)	0.090 (4)	0.084 (3)	0.002 (3)	0.014 (3)	0.006 (3)
C51	0.081 (3)	0.106 (4)	0.099 (4)	0.017 (4)	0.001 (3)	−0.004 (3)
C52	0.097 (4)	0.104 (4)	0.093 (4)	0.014 (4)	0.011 (4)	0.013 (3)
P1	0.0699 (7)	0.0848 (8)	0.0807 (8)	0.0021 (8)	−0.0014 (7)	−0.0021 (7)
F1	0.147 (4)	0.218 (5)	0.123 (3)	0.037 (5)	−0.054 (3)	−0.012 (3)
F2	0.181 (4)	0.100 (2)	0.130 (3)	−0.028 (3)	−0.004 (4)	0.022 (2)
F3	0.119 (3)	0.140 (4)	0.161 (4)	0.043 (3)	0.024 (3)	0.002 (3)
F4	0.152 (5)	0.130 (4)	0.305 (8)	−0.062 (4)	0.033 (6)	−0.006 (5)
F5	0.173 (5)	0.210 (6)	0.219 (6)	0.085 (5)	0.106 (5)	0.017 (5)
F6	0.218 (5)	0.158 (4)	0.094 (2)	−0.030 (5)	−0.028 (3)	0.025 (3)

Geometric parameters (Å, º)

N1—C2	1.301 (6)	C12—H12E	0.960
N1—C11	1.478 (7)	C12—H12F	0.960
N1—C12	1.458 (7)	C21—H21A	0.960
N5—C4	1.325 (7)	C21—H21B	0.960
N5—C51	1.431 (7)	C21—H21C	0.960
N5—C52	1.452 (7)	C21—H21D	0.960
C2—C3	1.401 (7)	C21—H21E	0.960
C2—C21	1.513 (7)	C21—H21F	0.960
C3—C4	1.374 (7)	C51—H51A	0.960
C3—H3	0.930	C51—H51B	0.960
C4—H4	0.930	C51—H51C	0.960
C11—H11A	0.960	C52—H52A	0.960
C11—H11B	0.960	C52—H52B	0.960
C11—H11C	0.960	C52—H52C	0.960
C11—H11D	0.960	P1—F5	1.536 (5)
C11—H11E	0.960	P1—F4	1.559 (5)
C11—H11F	0.960	P1—F6	1.570 (5)
C12—H12A	0.960	P1—F1	1.571 (4)
C12—H12B	0.960	P1—F2	1.578 (5)
C12—H12C	0.960	P1—F3	1.581 (5)
C12—H12D	0.960
C2—N1—C12	121.8 (5)	C2—C21—H21A	109.5
C2—N1—C11	123.6 (5)	C2—C21—H21B	109.5
C12—N1—C11	114.5 (5)	H21A—C21—H21B	109.5
C4—N5—C51	120.8 (5)	C2—C21—H21C	109.5
C4—N5—C52	122.5 (5)	H21A—C21—H21C	109.5
C51—N5—C52	116.7 (5)	H21B—C21—H21C	109.5
N1—C2—C3	122.2 (5)	C2—C21—H21D	109.5
N1—C2—C21	117.3 (5)	C2—C21—H21E	109.5
C3—C2—C21	120.4 (4)	H21D—C21—H21E	109.5
C4—C3—C2	123.8 (5)	C2—C21—H21F	109.5
C4—C3—H3	118.1	H21D—C21—H21F	109.5
C2—C3—H3	118.1	H21E—C21—H21F	109.5
N5—C4—C3	126.6 (5)	N5—C51—H51A	109.5
N5—C4—H4	116.7	N5—C51—H51B	109.5
C3—C4—H4	116.7	H51A—C51—H51B	109.5
N1—C11—H11A	109.5	N5—C51—H51C	109.5
N1—C11—H11B	109.5	H51A—C51—H51C	109.5
H11A—C11—H11B	109.5	H51B—C51—H51C	109.5
N1—C11—H11C	109.5	N5—C52—H52A	109.5
H11A—C11—H11C	109.5	N5—C52—H52B	109.5
H11B—C11—H11C	109.5	H52A—C52—H52B	109.5
N1—C11—H11D	109.5	N5—C52—H52C	109.5
N1—C11—H11E	109.5	H52A—C52—H52C	109.5
H11D—C11—H11E	109.5	H52B—C52—H52C	109.5
N1—C11—H11F	109.5	F5—P1—F4	91.3 (4)
H11D—C11—H11F	109.5	F5—P1—F6	91.5 (4)
H11E—C11—H11F	109.5	F4—P1—F6	88.9 (3)
N1—C12—H12A	109.5	F5—P1—F1	91.5 (4)
N1—C12—H12B	109.5	F4—P1—F1	95.3 (4)
H12A—C12—H12B	109.5	F6—P1—F1	174.8 (3)
N1—C12—H12C	109.5	F5—P1—F2	91.0 (3)
H12A—C12—H12C	109.5	F4—P1—F2	177.5 (3)
H12B—C12—H12C	109.5	F6—P1—F2	90.0 (3)
N1—C12—H12D	109.5	F1—P1—F2	85.7 (3)
N1—C12—H12E	109.5	F5—P1—F3	177.8 (4)
H12D—C12—H12E	109.5	F4—P1—F3	87.7 (3)
N1—C12—H12F	109.5	F6—P1—F3	90.4 (3)
H12D—C12—H12F	109.5	F1—P1—F3	86.7 (3)
H12E—C12—H12F	109.5	F2—P1—F3	90.1 (3)
C12—N1—C2—C3	−5.0 (7)	C21—C2—C3—C4	−6.3 (7)
C11—N1—C2—C3	177.6 (5)	C51—N5—C4—C3	−179.3 (5)
C12—N1—C2—C21	178.1 (5)	C52—N5—C4—C3	−0.9 (8)
C11—N1—C2—C21	0.8 (7)	C2—C3—C4—N5	179.3 (5)
N1—C2—C3—C4	177.0 (4)