1,3-Bis(2,4,6-tri­methyl­phen­yl)-3H-imidazol-1-ium tetra­oxidorhenate(VII)

The title compound, (C₂₁H₂₅N₂)[ReO₄], was formed as the unexpected product in an attempted synthesis of a rhenium(I)–N-heterocyclic carbene (NHC) complex. The compound has crystallographic mirror symmetry with both the cation and the tetrahedral anion located across a mirror plane. The cation and anion are linked by a C—H⋯O hydrogen bond.

Related literature

For related structures of some halide salts, see: Arduengo et al. (1995); Cole et al. (2002); Cole & Junk (2004); Lorber & Vendier (2009).

Experimental

Crystal data

• (C₂₁H₂₅N₂)[ReO₄]

• M_r = 555.63

• Monoclinic, P 2₁ /m

• a = 8.2989 (12) Å

• b = 16.373 (2) Å

• c = 8.3168 (12) Å

• β = 111.948 (2)°

• V = 1048.2 (3) ų

• Z = 2

• Mo Kα radiation

• μ = 5.83 mm⁻¹

• T = 293 K

• 0.39 × 0.10 × 0.09 mm

Data collection

• Bruker (Siemens) P4 diffractometer with a Bruker SMART 1000 CCD detector

• Absorption correction: multi-scan (SADABS; Bruker, 2001) T_min = 0.489, T_max = 0.592

• 5688 measured reflections

• 2056 independent reflections

• 1895 reflections with I > 2σ(I)

• R_int = 0.029

Refinement

• R[F² > 2σ(F²)] = 0.033

• wR(F²) = 0.083

• S = 1.13

• 2056 reflections

• 136 parameters

• H-atom parameters constrained

• Δρ_max = 1.32 e Å⁻³

• Δρ_min = −0.86 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C1—H1⋯O2^i	0.93	2.21	3.12 (1)	167 (1)
Symmetry code: (i) x-1, y, z.

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and POV-RAY (Cason, 2004); software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009).

Supporting information

S1. Comment

1,3-Bis(2,4,6-trimethylphenyl)-3H-imidazolium tetraoxorhenate(VII) (IMesH[ReO₄], 1) was formed as the unexpected product in an attempted synthesis of a rhenium(I)-N-heterocyclic carbene (NHC) complex. The reaction pathway is unexplained. The main feature in the formation of this complex is the oxidation of the rhenium metal from the +1 to the +7 state resulting in a [ReO₄]^- anion. This anion replaces the Cl^- anion in the IMesHCl salt since it is larger and the co-crystallization of more similar sized ions is favoured..

The compound has crystallographic mirror symmetry with the Re1, O1, O2 and the imidazolium C1 and H1 atoms all lying in a mirror plane. The geometry of the imidazolium cation is similar to those observed for previously reported structures of 1,3-Bis(2,4,6-trimethylphenyl)-3H-imidazolium salts, for example halide (Cl^-, Br^-) salts (Arduengo et al., 1995; Cole et al., 2002; Cole & Junk, 2004; Lorber &Vendier, 2009). The imidazolium C1—H1 is hydrogen bonded to O2 of the [ReO₄]^- anion (at x - 1, y, z) with H1···O2 = 2.21 (1) Å and C1—H1···O2 = 167 (1)°. Similar hydrogen bonds were observed between the cation and the anion in the halide salts (Cole & Junk, 2004). The Re—O2 bond is somewhat longer (1.714 (5) Å) than the other (nominally double) Re—O bonds (mean 1.690 (6) Å) and may indicate some localization of the anion negative charge on O2.

Related literature

For related structures of some halide salts see: Arduengo et al. (1995); Cole et al. (2002); Cole & Junk (2004); Lorber & Vendier (2009).

S2. Experimental

N,N'-Dimesitylimidazolium chloride (IMesHCl, 2 mmol, 0.66 g) was deprotonated with KO^tBu in tetrahydrofuran (thf) solution. This mixture was added to a thf solution of [Re₂(CO)₁₀] (1.06 mmol, 0.68 g) and stirred. Thin layer chromatography (TLC) was used to monitor the reaction and, due to the initial lack of product formation, the reaction mixture was heated in an oilbath at 70°C for an hour. The thf solvent was removed leaving a brown residue. The product was extracted with hexane and the hexane was then removed under reduced pressure. The residue was purified by column chromatography. A dark yellow fraction was eluted with dichloromethane (dcm). Crystallization from a 1:1 dcm:hexane solution gave light brown crystals of IMesH[ReO₄] (1). 1H NMR (δ, p.p.m.), C₆D₆: 1.91 (br,12H), 2.19 (br, 6H), 6.70 (br, 4H), 7.14 (s, 2H); 13 C NMR (δ, p.p.m.), C₆D₆: 17.8, 20.9, 121.8, 126.9, 128.9, 129.6, 141.2

S3. Refinement

All hydrogen atoms were added in calculated positions. Each was allowed to ride on the atom to which it is bonded with an isotropic adp set to 1.2 x (1.5 x for methyl H atoms) the equivalent isotropic adp of that atom.

Computing details

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL and SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and POV-RAY (Cason, 2004); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures

Fig. 1. The molecular structure of 1 showing the atomic numbering scheme. Displacement elipsoids are shown at the 50% probability level and H atoms are shown as small spheres of arbitary radii.

1,3-Bis(2,4,6-trimethylphenyl)-3H-imidazol-1-ium tetraoxidorhenate(VII)

Crystal data

(C21H25N2)[ReO4]	F(000) = 544
Mr = 555.63	Dx = 1.760 Mg m^−3
Monoclinic, P21/m	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yb	Cell parameters from 4658 reflections
a = 8.2989 (12) Å	θ = 2.6–26.5°
b = 16.373 (2) Å	µ = 5.83 mm^−1
c = 8.3168 (12) Å	T = 293 K
β = 111.948 (2)°	Needle, light brown
V = 1048.2 (3) Å^3	0.39 × 0.10 × 0.09 mm
Z = 2

Data collection

Bruker (Siemens) P4 diffractometer	2056 independent reflections
Radiation source: fine-focus sealed tube	1895 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.029
Detector resolution: 8.3 pixels mm^-1	θmax = 26.5°, θmin = 2.5°
φ and ω scans	h = −10→9
Absorption correction: multi-scan (SADABS; Bruker, 2001)	k = −19→20
Tmin = 0.489, Tmax = 0.592	l = −3→10
5688 measured reflections

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)] = 0.033	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.083	H-atom parameters constrained
S = 1.13	w = 1/[σ^2(Fo^2) + (0.0381P)^2 + 1.6122P] where P = (Fo^2 + 2Fc^2)/3
2056 reflections	(Δ/σ)max < 0.001
136 parameters	Δρmax = 1.32 e Å^−3
0 restraints	Δρmin = −0.86 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.

All hydrogen atoms were added in calculated positions. Each was allowed to ride on the atom to which it is bonded with an isotropic adp set to 1.2 x (1.5 x for methyl H atoms) the equivalent isotropic adp of that atom.

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

	x	y	z	Uiso*/Ueq
N1	0.3511 (4)	0.3161 (2)	0.0558 (4)	0.0350 (7)
C1	0.2687 (8)	0.2500	0.0779 (7)	0.0332 (11)
H1	0.1694	0.2500	0.1046	0.040*
C2	0.4899 (6)	0.2909 (3)	0.0166 (6)	0.0441 (10)
H2	0.5694	0.3245	−0.0058	0.053*
C3	0.3080 (5)	0.3994 (2)	0.0842 (5)	0.0340 (8)
C4	0.2575 (6)	0.4545 (2)	−0.0539 (5)	0.0392 (9)
C5	0.2133 (6)	0.5328 (3)	−0.0207 (6)	0.0425 (9)
H5	0.1779	0.5705	−0.1109	0.051*
C6	0.2198 (6)	0.5569 (2)	0.1404 (6)	0.0402 (9)
C7	0.2735 (6)	0.5004 (2)	0.2743 (6)	0.0408 (9)
H7	0.2783	0.5160	0.3835	0.049*
C8	0.3202 (6)	0.4215 (2)	0.2506 (5)	0.0370 (9)
C9	0.3843 (7)	0.3635 (3)	0.4026 (6)	0.0476 (11)
H9A	0.4806	0.3326	0.3976	0.071*
H9B	0.2923	0.3270	0.3982	0.071*
H9C	0.4209	0.3941	0.5088	0.071*
C10	0.2518 (9)	0.4325 (3)	−0.2318 (6)	0.0603 (14)
H10A	0.1737	0.4687	−0.3159	0.091*
H10B	0.2119	0.3772	−0.2584	0.091*
H10C	0.3660	0.4375	−0.2345	0.091*
C11	0.1718 (8)	0.6422 (3)	0.1711 (8)	0.0561 (13)
H11A	0.0786	0.6404	0.2131	0.084*
H11B	0.1352	0.6724	0.0644	0.084*
H11C	0.2707	0.6686	0.2555	0.084*
Re1	0.91490 (4)	0.2500	0.40489 (3)	0.05388 (13)
O1	1.0911 (8)	0.2500	0.5917 (7)	0.0756 (18)
O2	0.9768 (8)	0.2500	0.2300 (8)	0.0769 (17)
O3	0.7942 (8)	0.3344 (5)	0.3947 (7)	0.127 (2)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0437 (19)	0.0286 (16)	0.0382 (17)	−0.0031 (14)	0.0216 (15)	−0.0005 (13)
C1	0.038 (3)	0.026 (3)	0.041 (3)	0.000	0.021 (2)	0.000
C2	0.050 (2)	0.039 (2)	0.056 (3)	−0.009 (2)	0.034 (2)	−0.002 (2)
C3	0.043 (2)	0.0231 (17)	0.042 (2)	−0.0053 (16)	0.0221 (18)	−0.0030 (15)
C4	0.047 (2)	0.032 (2)	0.041 (2)	−0.0073 (18)	0.0204 (19)	−0.0007 (17)
C5	0.051 (3)	0.031 (2)	0.045 (2)	−0.0054 (18)	0.017 (2)	0.0048 (17)
C6	0.043 (2)	0.029 (2)	0.051 (2)	−0.0043 (17)	0.0203 (19)	−0.0030 (17)
C7	0.051 (3)	0.035 (2)	0.042 (2)	−0.0067 (18)	0.024 (2)	−0.0105 (17)
C8	0.042 (2)	0.033 (2)	0.040 (2)	−0.0068 (17)	0.0191 (18)	−0.0027 (16)
C9	0.062 (3)	0.044 (2)	0.039 (2)	−0.003 (2)	0.021 (2)	0.0002 (18)
C10	0.096 (4)	0.049 (3)	0.043 (2)	−0.006 (3)	0.035 (3)	−0.002 (2)
C11	0.071 (3)	0.035 (2)	0.068 (3)	0.003 (2)	0.032 (3)	−0.005 (2)
Re1	0.04629 (19)	0.0774 (2)	0.04186 (17)	0.000	0.02096 (13)	0.000
O1	0.077 (4)	0.060 (3)	0.072 (4)	0.000	0.008 (3)	0.000
O2	0.077 (4)	0.107 (5)	0.060 (3)	0.000	0.041 (3)	0.000
O3	0.116 (5)	0.179 (6)	0.081 (3)	0.073 (5)	0.032 (3)	0.004 (4)

Geometric parameters (Å, º)

N1—C1	1.330 (5)	C7—H7	0.9300
N1—C2	1.372 (5)	C8—C9	1.510 (6)
N1—C3	1.452 (5)	C9—H9A	0.9600
C1—N1^i	1.330 (5)	C9—H9B	0.9600
C1—H1	0.9300	C9—H9C	0.9600
C2—C2^i	1.341 (9)	C10—H10A	0.9600
C2—H2	0.9300	C10—H10B	0.9600
C3—C4	1.395 (6)	C10—H10C	0.9600
C3—C8	1.397 (6)	C11—H11A	0.9600
C4—C5	1.390 (6)	C11—H11B	0.9600
C4—C10	1.506 (6)	C11—H11C	0.9600
C5—C6	1.379 (6)	Re1—O1	1.689 (5)
C5—H5	0.9300	Re1—O3	1.691 (6)
C6—C7	1.388 (6)	Re1—O3^i	1.691 (6)
C6—C11	1.500 (6)	Re1—O2	1.714 (5)
C7—C8	1.385 (6)
C1—N1—C2	108.0 (4)	C3—C8—C9	122.7 (4)
C1—N1—C3	124.8 (3)	C8—C9—H9A	109.5
C2—N1—C3	126.9 (3)	C8—C9—H9B	109.5
N1—C1—N1^i	109.0 (5)	H9A—C9—H9B	109.5
N1—C1—H1	125.5	C8—C9—H9C	109.5
N1^i—C1—H1	125.5	H9A—C9—H9C	109.5
C2^i—C2—N1	107.5 (2)	H9B—C9—H9C	109.5
C2^i—C2—H2	126.3	C4—C10—H10A	109.5
N1—C2—H2	126.3	C4—C10—H10B	109.5
C4—C3—C8	122.4 (4)	H10A—C10—H10B	109.5
C4—C3—N1	119.3 (3)	C4—C10—H10C	109.5
C8—C3—N1	118.2 (3)	H10A—C10—H10C	109.5
C5—C4—C3	117.0 (4)	H10B—C10—H10C	109.5
C5—C4—C10	120.1 (4)	C6—C11—H11A	109.5
C3—C4—C10	122.9 (4)	C6—C11—H11B	109.5
C6—C5—C4	122.7 (4)	H11A—C11—H11B	109.5
C6—C5—H5	118.7	C6—C11—H11C	109.5
C4—C5—H5	118.7	H11A—C11—H11C	109.5
C5—C6—C7	118.2 (4)	H11B—C11—H11C	109.5
C5—C6—C11	121.1 (4)	O1—Re1—O3	109.8 (2)
C7—C6—C11	120.7 (4)	O1—Re1—O3^i	109.8 (2)
C8—C7—C6	122.1 (4)	O3—Re1—O3^i	109.7 (6)
C8—C7—H7	118.9	O1—Re1—O2	110.5 (3)
C6—C7—H7	118.9	O3—Re1—O2	108.5 (2)
C7—C8—C3	117.5 (4)	O3^i—Re1—O2	108.5 (2)
C7—C8—C9	119.8 (4)
C2—N1—C1—N1^i	0.6 (6)	C3—C4—C5—C6	0.7 (7)
C3—N1—C1—N1^i	−174.5 (3)	C10—C4—C5—C6	−178.5 (5)
C1—N1—C2—C2^i	−0.3 (4)	C4—C5—C6—C7	0.3 (7)
C3—N1—C2—C2^i	174.6 (3)	C4—C5—C6—C11	179.7 (4)
C1—N1—C3—C4	−119.1 (5)	C5—C6—C7—C8	0.0 (7)
C2—N1—C3—C4	66.8 (6)	C11—C6—C7—C8	−179.4 (4)
C1—N1—C3—C8	61.3 (6)	C6—C7—C8—C3	−1.4 (6)
C2—N1—C3—C8	−112.7 (5)	C6—C7—C8—C9	177.6 (4)
C8—C3—C4—C5	−2.1 (6)	C4—C3—C8—C7	2.4 (6)
N1—C3—C4—C5	178.3 (4)	N1—C3—C8—C7	−178.0 (4)
C8—C3—C4—C10	177.1 (5)	C4—C3—C8—C9	−176.5 (4)
N1—C3—C4—C10	−2.4 (6)	N1—C3—C8—C9	3.0 (6)

Symmetry code: (i) x, −y+1/2, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1···O2^ii	0.93	2.21	3.12 (1)	167 (1)

Symmetry code: (ii) x−1, y, z.