[4-(Dimethyl­amino)­phen­yl]diphenyl­phosphine selenide

Wade L Davis; Alfred Muller

doi:10.1107/S1600536812042602

. 2012 Oct 20;68(Pt 11):o3153–o3154. doi: 10.1107/S1600536812042602

[4-(Dimethylamino)phenyl]diphenylphosphine selenide

Wade L Davis ^a, Alfred Muller ^a,^*

PMCID: PMC3515250 PMID: 23284470

Abstract

In the title compound, C₂₀H₂₀NPSe, the P atom lies in a distorted tetrahedral environment. The Tolman cone angle is 157° indicating steric crowding at this atom. In the crystal, weak C—H⋯Se interactions create linked dimeric units and C—H⋯π interactions are also observed.

Related literature

For investigations into the steric and electronic properties of phosphorus containing ligands, see: Roodt et al. (2003 ▶); Otto & Roodt (2004 ▶); Muller et al. (2008 ▶); Cowley & Damasco (1971 ▶); Allen & Taylor (1982 ▶); Allen et al. (1985 ▶). For the free phosphine related to the title compound, see: Dreissig & Plieth (1972 ▶). For the oxide analogue of the title compound, see: Lynch et al. (2003 ▶). For the related phosphine selenide, see: Phasha et al. (2012 ▶). For cone angles, see: Tolman (1977 ▶); Otto (2001 ▶). For details on the conformational fit of molecules using Mercury, see: Macrae et al. (2006 ▶); Weng et al. (2008a ▶,b ▶). For a description of the Cambridge Structural Database, see: Allen (2002 ▶). For background on Bent’s rule, see: Bent (1961 ▶).

Experimental

Crystal data

C₂₀H₂₀NPSe
M _r = 384.3
Monoclinic,
a = 12.1757 (13) Å
b = 10.6173 (11) Å
c = 17.5211 (14) Å
β = 128.098 (5)°
V = 1782.5 (3) Å³
Z = 4
Mo Kα radiation
μ = 2.20 mm⁻¹
T = 100 K
0.22 × 0.11 × 0.09 mm

Data collection

Bruker APEX DUO 4K CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2008 ▶) T _min = 0.643, T _max = 0.827
31924 measured reflections
4553 independent reflections
3798 reflections with I > 2σ(I)
R _int = 0.050

Refinement

R[F ² > 2σ(F ²)] = 0.036
wR(F ²) = 0.097
S = 1.06
4553 reflections
210 parameters
H-atom parameters constrained
Δρ_max = 0.53 e Å⁻³
Δρ_min = −0.72 e Å⁻³

Data collection: APEX2 (Bruker, 2011 ▶); cell refinement: SAINT (Bruker, 2008 ▶); data reduction: SAINT and XPREP (Bruker, 2008 ▶); program(s) used to solve structure: SIR97 (Altomare et al., 1999 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: DIAMOND (Brandenburg & Putz, 2005 ▶); software used to prepare material for publication: publCIF (Westrip, 2010 ▶) & WinGX (Farrugia, 1999 ▶).

Supplementary Material

Click here for additional data file.^{(25.9KB, cif)}

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536812042602/yk2075sup1.cif

e-68-o3153-sup1.cif^{(25.9KB, cif)}

Click here for additional data file.^{(218.6KB, hkl)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812042602/yk2075Isup2.hkl

e-68-o3153-Isup2.hkl^{(218.6KB, hkl)}

Click here for additional data file.^{(6.3KB, cml)}

Supplementary material file. DOI: 10.1107/S1600536812042602/yk2075Isup3.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

Cg1 and Cg2 refer to the centroids of the C7–C12 and C13–C18 rings, respectively.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C20—H20A⋯Se1ⁱ	0.98	3.25	3.833 (3)	120
C20—H20C⋯Se1ⁱⁱ	0.98	3.07	3.707 (3)	124
C4—H4⋯Cg1ⁱⁱⁱ	0.95	2.66	3.476 (4)	145
C15—H15⋯Cg1^iv	0.95	2.90	3.699 (3)	142
C19—H19B⋯Cg2^v	0.98	2.79	3.627 (3)	144

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) ; (v) .

Acknowledgments

Financial assistance from the Research Fund of the University of Johannesburg is gratefully acknowledged.

supplementary crystallographic information

Comment

Over the past few decades several experimental procedures to rapidly evaluate steric and electronic properties of phoshane ligands have been developed. Highlights from these studies include the measuring of IR stretching frequencies in complexes such as [NiP(CO)₃] (Tolman, 1977), trans-[RhCl(CO)(P)₂] (Roodt et al., 2003; Otto & Roodt, 2004) and by the measuring of coupling constants between ³¹P and other NMR active nuclei such as ¹¹B, ¹⁹⁵Pt or ⁷⁷Se (Cowley & Damasco, 1971; Allen & Taylor, 1982; Allen et al., 1985). Recently our research into this area involved the use of seledized phosphane ligands, providing several useful probes such as ¹J(³¹P-⁷⁷Se) coupling, Se—P bond distance and kinetic reaction rates (Muller et al., 2008) to study the steric and electronic parameters of phosphorus containing ligands. Discussed here, as part of an ongoing study, is the structure of the title compound, which is the selenium derivative of the phosphane PPh₂(4-NMe₂—C₆H₄), where Ph = C₆H₅.

The title compound (see Fig. 1) crystallizes in the monoclinic space group, P 2₁/c (Z=4), with its molecules adopting a distorted tetrahedral arrangement about the phosphorus atom. The average C—P—C and Se—P—C angles are 105.28 (11)° and 113.40 (8)° respectively. The Se—P distance is 2.1069 (7) Å which is significantly shorter than the 2.1241 (5) Å reported for the analogous SePCy₂(4-NMe₂—C₆H₄) compound (Phasha et al., 2012). An increase of 26 Hz in the ¹J(³¹P-⁷⁷Se) NMR coupling is also observed for the title compound compared to the dicyclohexcyl analogue. This is in accordance with Bent's rule that the s-character of the phosphorus lone pair electrons will decrease with more electron-donating substituents (Bent, 1961).

To describe the steric demand of phosphane ligands a variety of models have been developed, of which the Tolman cone angle (Tolman, 1977) is still the most commonly used method. Applying this model to the geometry obtained for the title compound (and adjusting the Se—P bond distance to 2.28 Å) we calculated an effective cone angle from the geometry found in the crystal structure as 157° (Otto, 2001). This value is comparable to the cone angles calculated for the structure of the free (Lynch et al., 2003) and oxidized (Dreissig & Plieth, 1972) forms of the phosphane (calculated as 158° and 161° respectively). The orientation of the substituents for the oxidized derivative is comparable to that of the title compound, whereas the free phosphane shows substantial differences in its orientations. To illustrate this observation, the coordinates of P and ipso C-atoms of the three structures are superimposed using Mercury (see Fig. 2; Macrae et al., 2006; Weng et al., 2008a; Weng et al., 2008b). The reason for the different substituent orientations are possibly due to different interactions observed to the packing of these structures. It is also interesting to note that coordination of the phosphane to transition metals does not induce significant steric crowding, and hence a smaller cone angle, of the ligand at the coordination sphere. Data extracted for these coordination complexes from the Cambridge Structural Database shows an average cone angle of 159° (Allen, 2002; 9 observations with metals: Au, Pt, Pd, Rh and Cu).

Packing in the crystals is assisted by weak C—H···Se interactions creating linked dimeric units of the title compound. In addition C—H···π interactions are also observed (see table 1 and Fig. 3 for a graphical representation of the interactions).

Experimental

[4-(Dimethylamino)phenyl]diphenylphosphane and KSeCN were purchased from Sigma-Aldrich and used without purification. Eqimolar amounts of KSeCN (5.8 mg, 0.04 mmol) and the [4-(dimethylamino)phenyl]diphenylphosphane (12.2 mg, 0.04 mmol) were dissolved in the minimum amounts of methanol (10 ml). The KSeCN solution was added drop wise (5 min.) to the phosphane solution with stirring at room temperature. Slow evaporation of the solvent afforded the title compound as colourless crystals suitable for a single-crystal X-ray study. Analytical data: ³¹P {H} NMR (CDCl₃, 161.99 MHz): δ = 33.62 (t, ¹J(³¹P-⁷⁷Se) = 713 Hz).