Qu­anti­tative insights into noncovalent inter­actions involving halogen and tetrel bonds in 2,4,6-tri­methyl­pyrylium tetra­fluoro­borate

The crystal and molecular structure of an organic salt, in which a 2,4,6-tri­methyl­pyrylium cation forms a salt with a tetrafluoroborate anion, namely, 2,4,6-tri­methyl­pyrylium tetra­fluoro­borate, C₈H₁₁O⁺·BF₄⁻, has been experimentally realized. The com­pound crystallizes in the ortho­rhom­bic centrosymmetric space group Pnma. The crystal packing is stabilized via a subtle inter­play of [F₃—B—F]⁻...O⁺—C fluorine/oxygen-centred halogen/chalcogen bonds and C^δ+...F^δ− tetrel-bonded contacts. Although the O centre has a formal charge of +1, the estimation of the partial negative charges on O is in accordance with electronegativity considerations. Hirshfeld surface analysis, which also includes an analysis of the three-dimensional deformation density, along with molecular electrostatic potential (MESP) calculations, provides qu­anti­tative insights into the nature of the inter­molecular inter­actions. The topological analysis of the electron-density distribution has been performed using AIMAll and TOPOND, and unequivocally establishes the bonding character associated with the different noncovalent inter­actions. In addition, NBO analysis and polarizability calculations using PolaBer render deeper physical insights into the electronic characteristics of these noncovalent inter­actions.

Computing details

Data collection: APEX3 (Bruker, 2016); cell refinement: SAINT (Bruker, 2015); data reduction: SAINT (Bruker, 2015); program(s) used to solve structure: SHELXT2014 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018 (Sheldrick, 2015b); molecular graphics: OLEX2 (Dolomanov et al., 2009) and Mercury (Macrae et al., 2020); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009), PARST (Nardelli, 1995) and PLATON (Spek, 2020).

2,4,6-Trimethylpyrylium tetrafluoroborate

Crystal data

C8H11O^+·BF4^−	Dx = 1.491 Mg m^−3
Mr = 209.98	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pnma	Cell parameters from 4437 reflections
a = 9.7906 (5) Å	θ = 2.9–29.8°
b = 9.6859 (5) Å	µ = 0.15 mm^−1
c = 9.8673 (5) Å	T = 100 K
V = 935.72 (8) Å^3	Plate, clear light colourless
Z = 4	0.19 × 0.13 × 0.07 mm
F(000) = 432

Data collection

Bruker D8 Venture diffractometer	1236 reflections with I > 2σ(I)
φ and ω scans	Rint = 0.022
Absorption correction: multi-scan (SADABS; Bruker, 2014)	θmax = 29.9°, θmin = 2.9°
Tmin = 0.696, Tmax = 0.746	h = −10→13
9024 measured reflections	k = −13→13
1424 independent reflections	l = −13→9

Refinement

Refinement on F^2	Primary atom site location: dual
Least-squares matrix: full	Hydrogen site location: mixed
R[F^2 > 2σ(F^2)] = 0.035	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.090	w = 1/[σ^2(Fo^2) + (0.0398P)^2 + 0.3609P] where P = (Fo^2 + 2Fc^2)/3
S = 1.05	(Δ/σ)max < 0.001
1424 reflections	Δρmax = 0.39 e Å^−3
93 parameters	Δρmin = −0.25 e Å^−3
0 restraints

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. Single-crystal data were collected on a Bruker D8 VENTURE diffractometer equipped with a CMOS/PHOTON III detector instrument using monochromated Mo Kα radiation (λ = 0.71073 Å). Data reduction was performed with the Bruker APEXIII software suite (APEX3; Bruker, 2016). The crystal structure was solved by intrinsic phasing using the SHELXT program (Sheldrick, 2015a). All structures were refined by the full-matrix least-squares method using SHELXL2018 (Sheldrick, 2015b) present in the OLEX2 interface (Dolomanov et al., 2009). The crystal packing view was generated using Mercury (Version 3.9; Macrae et al., 2020; www.ccdc.cam.ac.uk/mercury). Geometrical calculations were carried out using PARST (Nardelli, 1995) and PLATON (Spek, 2020).

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

	x	y	z	Uiso*/Ueq
F1	0.36037 (9)	0.250000	0.45429 (10)	0.0311 (2)
F2	0.15210 (10)	0.250000	0.35656 (9)	0.0276 (2)
F3	0.18515 (8)	0.36760 (7)	0.55250 (7)	0.03065 (19)
O1	0.48551 (10)	0.250000	0.72254 (9)	0.0156 (2)
C1	0.81897 (17)	0.250000	0.44989 (17)	0.0261 (3)
C2	0.70202 (14)	0.250000	0.54682 (13)	0.0176 (3)
C3	0.64482 (10)	0.37372 (10)	0.59278 (10)	0.0178 (2)
H3	0.681194	0.459536	0.563280	0.022 (3)
C4	0.53671 (10)	0.37110 (9)	0.68004 (9)	0.0160 (2)
C5	0.46353 (11)	0.49183 (10)	0.73635 (11)	0.0207 (2)
H5A	0.367463	0.488407	0.708666	0.031*
H5B	0.505327	0.576926	0.702199	0.031*
H5C	0.469335	0.490109	0.835489	0.033 (4)
B1	0.22013 (15)	0.250000	0.47869 (16)	0.0159 (3)
H1A	0.786 (2)	0.250000	0.360 (3)	0.050 (7)*
H1B	0.872 (2)	0.1699 (19)	0.4604 (19)	0.062 (5)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
F1	0.0154 (4)	0.0477 (6)	0.0303 (5)	0.000	0.0016 (4)	0.000
F2	0.0282 (5)	0.0301 (5)	0.0244 (5)	0.000	−0.0090 (4)	0.000
F3	0.0407 (4)	0.0194 (3)	0.0318 (4)	−0.0039 (3)	0.0122 (3)	−0.0096 (3)
O1	0.0165 (5)	0.0145 (4)	0.0158 (5)	0.000	0.0002 (4)	0.000
C1	0.0201 (7)	0.0351 (8)	0.0230 (8)	0.000	0.0056 (6)	0.000
C2	0.0146 (6)	0.0246 (7)	0.0137 (6)	0.000	−0.0019 (5)	0.000
C3	0.0184 (5)	0.0186 (4)	0.0165 (4)	−0.0035 (4)	−0.0018 (4)	0.0014 (4)
H3	0.022 (8)	0.024 (8)	0.020 (7)	0.003 (6)	0.001 (6)	−0.002 (7)
C4	0.0187 (5)	0.0146 (4)	0.0148 (4)	−0.0013 (3)	−0.0038 (3)	0.0004 (3)
C5	0.0243 (5)	0.0159 (4)	0.0218 (5)	0.0021 (4)	−0.0005 (4)	−0.0017 (4)
H5C	0.060 (11)	0.018 (8)	0.023 (8)	0.011 (8)	−0.010 (8)	−0.005 (7)
B1	0.0157 (7)	0.0151 (6)	0.0169 (7)	0.000	0.0014 (5)	0.000

Geometric parameters (Å, º)

F1—B1	1.3940 (17)	C2—C3^i	1.3983 (12)
F2—B1	1.3769 (18)	C2—C3	1.3983 (12)
F3—B1	1.3947 (11)	C3—H3	0.9500
O1—C4^i	1.3428 (10)	C3—C4	1.3646 (14)
O1—C4	1.3428 (10)	C4—C5	1.4797 (14)
C1—C2	1.492 (2)	C5—H5A	0.9800
C1—H1A	0.94 (2)	C5—H5B	0.9800
C1—H1B	0.938 (19)	C5—H5C	0.9800
C1—H1B^i	0.938 (19)
C4—O1—C4^i	121.74 (11)	O1—C4—C5	113.09 (8)
C2—C1—H1A	110.0 (15)	C3—C4—C5	126.71 (9)
C2—C1—H1B^i	110.6 (12)	C4—C5—H5A	109.5
C2—C1—H1B	110.6 (12)	C4—C5—H5B	109.5
H1A—C1—H1B^i	106.9 (14)	C4—C5—H5C	109.5
H1A—C1—H1B	106.9 (14)	H5A—C5—H5B	109.5
H1B—C1—H1B^i	112 (2)	H5A—C5—H5C	109.5
C3^i—C2—C1	121.02 (6)	H5B—C5—H5C	109.5
C3—C2—C1	121.02 (6)	F1—B1—F3	109.39 (8)
C3^i—C2—C3	117.96 (13)	F1—B1—F3^i	109.39 (8)
C2—C3—H3	120.0	F2—B1—F1	108.99 (12)
C4—C3—C2	119.96 (10)	F2—B1—F3^i	109.77 (8)
C4—C3—H3	120.0	F2—B1—F3	109.77 (8)
O1—C4—C3	120.19 (9)	F3^i—B1—F3	109.51 (12)
C1—C2—C3—C4	179.13 (12)	C3^i—C2—C3—C4	0.15 (19)
C2—C3—C4—O1	0.37 (15)	C4^i—O1—C4—C3	−0.91 (17)
C2—C3—C4—C5	−179.06 (10)	C4^i—O1—C4—C5	178.59 (7)

Symmetry code: (i) x, −y+1/2, z.