Di­fluoro­(mesityl)­phosphine

The title compound, C₉H₁₁F₂P, displays mirror symmetry, with all ring C and the P atom lying in the mirror plane. The methyl H atoms are disordered across the mirror plane. Key dimensions around the P atom are P-F 1.5814 (10), P-C 1.8116 (17) Å and F-P-F 95.95 (8)°.

Key indicators

• Single-crystal X-ray study
• T = 178 K
• Mean [sigma](C-C) = 0.002 Å
• Disorder in main residue
• R factor = 0.030
• wR factor = 0.087
• Data-to-parameter ratio = 14.6

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level B:



CRYSS_02  Alert B The value of _exptl_crystal_size_min is > 0.6
 Minimum crystal size given =   0.700


 0 Alert Level A = Potentially serious problem

 1 Alert Level B = Potential problem

 0 Alert Level C = Please check

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S1. Comment

We are interested in organic derivatives of phosphorus trifluoride. We have published the syntheses of several compounds of the type RPF₂ (Heuer & Schmutzler, 1988, 1989; Wesemann et al., 1992, and references therein), but the X-ray structure determinations have, with one exception (Heuer et al., 1989), been limited to metal complexes. We present here the structure of uncomplexed difluoro(mesityl)phosphine, (I).

The molecule is shown in Fig. 1; it possesses crystallographic mirror symmetry, with all atoms except fluorine and methyl H atoms (which are disordered, see Experimental) lying in the mirror planes. A closely similar arrangement was observed for the hydrogen analogue mesitylphosphine (Bartlett et al., 1987), which also crystallizes in Pnma, but the structures do not seem to be isotypic.

The molecular dimensions of (I) may be regarded as normal. For discussion purposes, non-corrected bond lengths are used, but libration-corrected values are presented in the Experimental section. The P—F bond length is 1.5814 (10) Å, with F—P—F 95.95 (8)°, cf. 1.572, 1.581 (2) Å and 96.3 (1)° in the anthracene-9-PF₂ dimer (Heuer et al., 1989). The P—C bond length of 1.8116 (17) Å may be compared with the value of 1.807 (5) Å observed for mesitylphosphine (Bartlett et al., 1987), but is rather shorter than the average of 1.833 Å observed for the series PPh₂(Mes), PPh(Mes)₂ and P(Mes)₃ (Blount et al., 1994), and much shorter than the 1.859 (2) Å in the anthracene dimer, for which steric crowding may be responsible for bond lengthening.

The orientation of the PF₂ group with respect to the ring is given by the torsion angle F—P—C1—C2 of 49.15 (4)°.

One of the methyl H atoms is involved in a short contact to the centroid (Cg) of a ring in the neighbouring layer: C9—H9A···Cg with normalized H···Cg 2.64 Å and C—H···Cg 150°. This could be considered as a C—H···π interaction.

S2. Experimental

The title compound was prepared from the reaction of the corresponding chloride with sodium fluoride in acetonitrile. It was isolated as an oil that crystallized in the form of colourless prisms (m.p. 408–410 K), extremely sensitive to laboratory air (Heuer, 1989). For this reason, the crystal used for structure determination was rather larger than usual.

S3. Refinement

The aromatic atoms H3 and H5 were refined freely. The methyl H atoms, which are disordered across the mirror plane, could nonetheless be identified in difference syntheses; the methyl groups were then idealized and refined as rigid groups allowed to rotate but not tip. The structure could also be refined with ordered methyl groups in the corresponding non-centrosymmetric space group Pna2₁, but with a series of restraints to improve refinement stability. The R values were not improved. It is unlikely that X-ray methods alone can distinguish between the two possibilities; we prefer the disordered centrosymmetric model because it is unaffected by the matrix near-singularities inherent in the Pna2₁ refinement. The latter is presented in the deposited material. A rigid-body libration correction (Schomaker & Trueblood, 1968) gave the following corrected bond lengths (Å): P—F 1.588, P—C1 1.819, C1—C2 1.419, C2—C3 1.397, C3—C4 1.392, C4—C5 1.391, C1—C6 1.414, C5—C6 1.398, C2—C7 1.520, C4—C8 1.518, C6—C9 1.519.

Computing details

Data collection: P3 (Nicolet, 1987); cell refinement: P3; data reduction: XDISK (Nicolet, 1987); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP (Siemens, 1994); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. The molecule of the title compound in the crystal. Displacement ellipsoids are shown at the 30% probability level. H-atom radii are arbitrary.

Mesityldifluorophosphine

Crystal data

C9H11F2P	Dx = 1.347 Mg m^−3
Mr = 188.15	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Pnma	Cell parameters from 50 reflections
a = 13.261 (5) Å	θ = 8–11.5°
b = 7.185 (2) Å	µ = 0.27 mm^−1
c = 9.735 (3) Å	T = 178 K
V = 927.6 (5) Å^3	Block, colourless
Z = 4	0.7 × 0.7 × 0.7 mm
F(000) = 392

Data collection

Nicolet R3 diffractometer	Rint = 0.015
Radiation source: fine-focus sealed tube	θmax = 27.5°, θmin = 3.1°
Graphite monochromator	h = 0→17
ω scans	k = 0→9
2236 measured reflections	l = −12→12
1154 independent reflections	3 standard reflections every 147 reflections
1014 reflections with I > 2σ(I)	intensity decay: 1.5%

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)] = 0.030	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.087	H atoms treated by a mixture of independent and constrained refinement
S = 1.09	w = 1/[σ^2(Fo^2) + (0.0397P)^2 + 0.2323P] where P = (Fo^2 + 2Fc^2)/3
1154 reflections	(Δ/σ)max = 0.001
79 parameters	Δρmax = 0.21 e Å^−3
0 restraints	Δρmin = −0.34 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.

Final refinement of the alternative model in Pna2(1):

TITL MESFO in Pna21 CELL 0.71073 13.261 9.735 7.185 90.00 90.00 90.00 ZERR 4.00 0.005 0.003 0.002 0.00 0.00 0.00 L A T T −1 SYMM −x,-y,0.5 + z SYMM 0.5 + x,0.5 − y,z SYMM 0.5 − x,0.5 + y,0.5 + z SFAC C H F P UNIT 36 44 8 4 TEMP −95 SIZE 0.7 0.7 0.7 L·S. 4 FMAP 2 PLAN 10 DELU SIMU SADI C7 H7A C7 H7B C7 H7C C8 H8A C8 H8B C8 H8C C9 H9A C9 H9B C9 H9C SADI H7A H7B H7A H7C H7B H7C H8A H8B H8A H8C H8B H8C H9A H9B H9A H9C H9B H9C WGHT 0.047300 0.202000 FVAR 2.32532 P 4 0.423192 0.744056 0.520125 11.00000 0.06015 0.02825 = 0.05304 − 0.00086 0.00024 0.00593 F1 3 0.349251 0.785341 0.683751 11.00000 0.09525 0.03992 = 0.05375 − 0.00739 0.01003 0.02203 F2 3 0.347575 0.779485 0.356626 11.00000 0.09522 0.05638 = 0.04619 0.01154 0.00099 0.03171 flat c1 > c6 same c1 c6 < c2 C1 1 0.412749 0.558693 0.521719 11.00000 0.03680 0.02923 = 0.02905 0.00214 0.00366 0.00289 C2 1 0.504768 0.486457 0.519958 11.00000 0.03191 0.03253 = 0.02798 − 0.00180 0.00149 − 0.00040 C3 1 0.502870 0.343557 0.519671 11.00000 0.03574 0.03256 = 0.03439 0.00359 0.00461 0.00608 AFIX 43 H3 2 0.564896 0.294732 0.519124 11.00000 − 1.20000 AFIX 0 C4 1 0.413397 0.270347 0.520157 11.00000 0.04622 0.03081 = 0.03533 − 0.00062 0.00087 − 0.00256 C5 1 0.323307 0.342865 0.521671 11.00000 0.03544 0.04239 = 0.03943 0.00058 0.00236 − 0.00813 AFIX 43 H5 2 0.261537 0.293449 0.523036 11.00000 − 1.20000 AFIX 0 C6 1 0.320696 0.485580 0.521251 11.00000 0.03199 0.04281 = 0.03397 − 0.00144 − 0.00119 0.00475 C7 1 0.606354 0.556836 0.522338 11.00000 0.03518 0.04656 = 0.04453 0.00333 0.00650 − 0.00637 H7A 2 0.658118 0.487797 0.563976 11.00000 0.04088 H7B 2 0.611256 0.635593 0.612886 11.00000 0.04457 H7C 2 0.626626 0.589962 0.396627 11.00000 0.06572 C8 1 0.415147 0.115216 0.520921 11.00000 0.07173 0.03077 = 0.06755 0.00571 0.00545 − 0.00478 H8A 2 0.423830 0.080404 0.391482 11.00000 0.07896 H8B 2 0.349790 0.080626 0.571594 11.00000 0.06340 H8C 2 0.471017 0.076989 0.599913 11.00000 0.05253 C9 1 0.218608 0.554852 0.522924 11.00000 0.03409 0.06773 = 0.06689 0.00526 − 0.00348 0.01188 H9A 2 0.167635 0.488153 0.568060 11.00000 0.05191 H9B 2 0.200722 0.583079 0.392721 11.00000 0.07149 H9C 2 0.217295 0.638548 0.602643 11.00000 0.04823 HKLF 4 1 1 0 0 0 0 1 0 − 1 0

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

	x	y	z	Uiso*/Ueq	Occ. (<1)
P	0.42319 (4)	0.2500	0.74409 (4)	0.04714 (18)
F	0.34854 (7)	0.08650 (12)	0.78264 (9)	0.0646 (3)
C1	0.41273 (11)	0.2500	0.55854 (15)	0.0318 (3)
C2	0.32066 (12)	0.2500	0.48570 (18)	0.0363 (4)
C3	0.32331 (12)	0.2500	0.34280 (19)	0.0392 (4)
H3	0.2582 (17)	0.2500	0.296 (2)	0.060 (6)*
C4	0.41334 (13)	0.2500	0.27039 (17)	0.0376 (4)
C5	0.50289 (12)	0.2500	0.34348 (16)	0.0341 (3)
H5	0.5663 (15)	0.2500	0.298 (2)	0.047 (5)*
C6	0.50481 (12)	0.2500	0.48651 (16)	0.0308 (3)
C7	0.21840 (14)	0.2500	0.5549 (2)	0.0562 (5)
H7A	0.2206	0.3300	0.6363	0.067*	0.50
H7C	0.2009	0.1228	0.5823	0.067*	0.50
H7B	0.1675	0.2972	0.4907	0.067*	0.50
C8	0.41505 (17)	0.2500	0.1151 (2)	0.0564 (5)
H8A	0.3511	0.2996	0.0802	0.068*	0.50
H8B	0.4243	0.1225	0.0817	0.068*	0.50
H8C	0.4708	0.3280	0.0826	0.068*	0.50
C9	0.60655 (13)	0.2500	0.55665 (19)	0.0421 (4)
H9A	0.6224	0.3761	0.5884	0.051*	0.50
H9B	0.6583	0.2088	0.4916	0.051*	0.50
H9C	0.6049	0.1651	0.6354	0.051*	0.50

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
P	0.0602 (3)	0.0532 (3)	0.0281 (2)	0.000	0.00585 (19)	0.000
F	0.0953 (7)	0.0497 (5)	0.0486 (5)	−0.0044 (5)	0.0269 (4)	0.0092 (4)
C1	0.0372 (8)	0.0288 (7)	0.0295 (7)	0.000	0.0029 (6)	0.000
C2	0.0319 (8)	0.0335 (8)	0.0434 (9)	0.000	0.0048 (6)	0.000
C3	0.0354 (8)	0.0392 (9)	0.0430 (9)	0.000	−0.0082 (7)	0.000
C4	0.0467 (9)	0.0350 (8)	0.0309 (8)	0.000	−0.0025 (6)	0.000
C5	0.0352 (8)	0.0340 (8)	0.0331 (8)	0.000	0.0060 (6)	0.000
C6	0.0318 (7)	0.0274 (7)	0.0331 (7)	0.000	−0.0002 (5)	0.000
C7	0.0348 (9)	0.0662 (13)	0.0678 (13)	0.000	0.0117 (9)	0.000
C8	0.0713 (13)	0.0667 (13)	0.0311 (9)	0.000	−0.0056 (8)	0.000
C9	0.0360 (8)	0.0442 (9)	0.0461 (9)	0.000	−0.0057 (7)	0.000

Geometric parameters (Å, º)

P—F	1.5814 (10)	C5—H5	0.95 (2)
P—F^i	1.5814 (10)	C6—C9	1.512 (2)
P—C1	1.8116 (17)	C7—H7A	0.9800
C1—C6	1.408 (2)	C7—H7C	0.9800
C1—C2	1.412 (2)	C7—H7B	0.9800
C2—C3	1.392 (3)	C8—H8A	0.9800
C2—C7	1.514 (2)	C8—H8B	0.9800
C3—C4	1.386 (2)	C8—H8C	0.9800
C3—H3	0.98 (2)	C9—H9A	0.9800
C4—C5	1.384 (2)	C9—H9B	0.9800
C4—C8	1.512 (2)	C9—H9C	0.9800
C5—C6	1.393 (2)
F—P—F^i	95.95 (8)	C1—C6—C9	123.29 (14)
F—P—C1	100.88 (5)	C2—C7—H7A	109.5
F^i—P—C1	100.88 (5)	C2—C7—H7C	109.5
C6—C1—C2	119.98 (14)	H7A—C7—H7C	109.5
C6—C1—P	115.48 (12)	C2—C7—H7B	109.5
C2—C1—P	124.54 (12)	H7A—C7—H7B	109.5
C3—C2—C1	118.70 (14)	H7C—C7—H7B	109.5
C3—C2—C7	117.86 (16)	C4—C8—H8A	109.5
C1—C2—C7	123.44 (16)	C4—C8—H8B	109.5
C4—C3—C2	122.01 (15)	H8A—C8—H8B	109.5
C4—C3—H3	121.6 (14)	C4—C8—H8C	109.5
C2—C3—H3	116.4 (14)	H8A—C8—H8C	109.5
C5—C4—C3	118.51 (15)	H8B—C8—H8C	109.5
C5—C4—C8	120.06 (16)	C6—C9—H9A	109.5
C3—C4—C8	121.43 (16)	C6—C9—H9B	109.5
C4—C5—C6	121.97 (15)	H9A—C9—H9B	109.5
C4—C5—H5	121.3 (13)	C6—C9—H9C	109.5
C6—C5—H5	116.7 (13)	H9A—C9—H9C	109.5
C5—C6—C1	118.82 (14)	H9B—C9—H9C	109.5
C5—C6—C9	117.89 (14)
F—P—C1—C6	−130.85 (4)	C2—C3—C4—C5	0.0
F^i—P—C1—C6	130.85 (4)	C2—C3—C4—C8	180.0
F—P—C1—C2	49.15 (4)	C3—C4—C5—C6	0.0
F^i—P—C1—C2	−49.15 (4)	C8—C4—C5—C6	180.0
C6—C1—C2—C3	0.0	C4—C5—C6—C1	0.0
P—C1—C2—C3	180.0	C4—C5—C6—C9	180.0
C6—C1—C2—C7	180.0	C2—C1—C6—C5	0.0
P—C1—C2—C7	0.0	P—C1—C6—C5	180.0
C1—C2—C3—C4	0.0	C2—C1—C6—C9	180.0
C7—C2—C3—C4	180.0	P—C1—C6—C9	0.0

Symmetry code: (i) x, −y+1/2, z.