Buy article online - an online subscription or single-article purchase is required to access this article.
Download citation
Download citation
link to html
The structure of the title `half oxide', C28H28P2O, (I), is found to be isomorphous with the previously determined `full oxide', 1,4-bis­(di­phenyl­phosphinoyl)­butane. A significant feature is an apparent shortening of the P-O bond distance [1.379 (3) Å] in (I) compared to the `full oxide' [1.481 (2) Å], a result consistent with other known phosphine `partial' oxides.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536803006561/tk6098sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536803006561/tk6098Isup2.hkl
Contains datablock I

CCDC reference: 214592

Key indicators

  • Single-crystal X-ray study
  • T = 295 K
  • Mean [sigma](C-C) = 0.004 Å
  • R factor = 0.048
  • wR factor = 0.154
  • Data-to-parameter ratio = 19.0

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


Yellow Alert Alert Level C:
PLAT_320 Alert C Check Hybridisation of C(21) in Main Residue ?
0 Alert Level A = Potentially serious problem
0 Alert Level B = Potential problem
1 Alert Level C = Please check

Comment top

Tertiary phosphine oxides have proven utility as coordinating ligands in complex chemistry as well as being useful as aids for crystallization (Etter & Baures, 1988) through simple linear hydrogen-bonding associations between the oxide group and a proton-donating group, such as a carboxylic acid (Lynch et al., 1992, 1997; Smith et al., 1997, 1998). The parent tertiary phosphines, e.g. triphenylphosphine, are likewise useful as bulky ligands for stabilization of metal ions such as copper(I), silver(I) and gold(I), and extension of the ligand capacity via multiple pendant phosphinoyl groups has potential for formation of useful polymeric structures. It has been observed (Heinze et al., 1997) that partial oxidation of the phosphorus group in uncoordinated `dangling arms' of such multidentate ligands occurs quite easily. The first reported example of this was in the ReIII–carbonyl complex with bis(diphenylphosphino)methane (Carriedo et al., 1990), where the occupancy factor for O was 0.30. For the PdII–chloride complex with a similar diphosphine (Sevillano et al., 2000), the pendant arm was 50% oxidized. The phenomenon has also been observed in structures of uncoordinated phosphines, such as 1,1,1-tris(diphenylphosphinomethyl)propane (Chekhlov, 2000), where the three O atoms had occupancies of 11.3, 13.5 and 39.0%. In another example, the triphenylphosphine oxide–triphenylmethanol dimer (Steiner, 2000), the two molecules are related by pseudosymmetry across a crystallographic inversion centre (50% occupancy). We have also found that an isomorphous crystal series exists for the three isolated phosphine oxides (25.0, 50.0, 100.0%) of [4-(N,N-dimethylamino)phenyl]diphenylphosphine oxide (Lynch et al., 2003).

The cell dimensions of the title compound, (I), are similar to those previously reported for the dioxide (Fontes et al., 1991) [comparative (room temperature) permuted unit cell (Fontes et al., 1991): a = 8.862 (1), b = 12.517 (2), c = 5.862 (1) Å, α = 102.67 (1), β = 104.22 (1), γ = 100.29 (1)°, V = 592.4 (2) Å3]. Our determination in (I) has confirmed the presence of 50% occupancy (see below) for the oxygen sites which are statistically distributed across an inversion centre in the cell (Fig. 1). This result is consistent with the analytical and spectroscopic data that one P atom is oxidized while the other is unoxidized.

Another interesting and previously unreported phenomenon is the presence of significant P—O bond shortening for (I) [1.379 (3) Å] and for all other known `partial oxides', compared to 1.481 (2) Å in the `full oxide' (Fontes et al., 1991) and in both triphenylphosphine oxide [1.483 (2) and 1.484 (1) Å for the two monoclinic modifications (Ruban & Zabel, 1976; Spek, 1987)] and in triphenylphosphine oxide–carboxylic acid adducts [1.49 Å (mean); Smith et al., 1998]. The value in (I) is similar to distances for other `50% oxides' [1.378 (3) (Steiner, 2000), 1.39 (2) (Sevillano, 2000) and 1.357 (4) Å (Lynch et al. 2002)], and compares with 1.399 (4) (11.3%), 1.295 (14) (13.5%) and 1.368 (5) Å (39.0%) (Chekhlov, 2000), and 1.280 (4) Å (25.0%) (Lynch et al., 2003). The 31P NMR chemical shift data and PO IR vibrational frequency data for (I) are typical for `normal' arylphosphine oxide PO bonds, e.g. ν (PO) for (I) (1182 cm−1) cf. 1185 cm−1 for 1,4-bis(diphenylphosphinoyl)butane (Higgins et al., 1987). This indicates that the apparent shortening of the P—O bond in structures with partial occupancy of the O atoms is an probably an artefact of the structure refinement process. In this context, it is interesting to note that the C—P—O and C—P—C bond angles around the P atom in (I) are consistently larger (115° mean) and smaller (104° mean), respectively, than the corresponding angles in the full oxide (112.7° and mean 105.9°). This is consistent with the decrease in the P—O bond length arising from movement of the P atom site towards the O atom.

Stabilizing the conformation of the ring system is a short intramolecular contact between a ring H and the oxide O atom [C6A—H6A···O1 = 2.933 (6) Å]. As expected little intermolecular association is found in the unit cell of (I), with only one C—-H···O contact [C11–H11B···O1i = 3.473 (4) Å: symmetry code: (i) x, y, 1 + z].

Experimental top

The title compound, (I), was synthesized according to the method of Grushin (2001). A mixture of palladium acetate (5 mg), 1,4-bis(diphenylphosphino)butane (2.00 g, 4.8 mmol), 1,2-dibromoethane (1.8 g, 9.6 mmol) and dichloromethane (5 ml) was stirred for 30 min. Aqueous sodium hydroxide (20% w/w, 5 ml) was added and the mixture stirred at room temperature for 3 d. Dichloromethane (15 ml) was then added and the organic phase filtered through a silica plug which was then washed with dichloromethane–ethyl acetate (5:3 v/v, 40 ml). The combined organic solutions were evaporated to dryness. The solid residue was dissolved in boiling dichloromethane (15 ml). Ether (50 ml) was added and the solution left to stand at room temperature for 2 h, yielding colourless crystals of (I). A crystal suitable for X-ray diffraction studies was grown by slow diffusion of methanol into a solution of (I) in dichloromethane. Analysis found: C 76.2, H 6.4%; calculated for C28H28OP2: C 76.0, H 6.4%. νmax (KBr) cm−1 1182 (PO). δH (400 MHz, CDCl3, p.p.m.) 1.4 (2H, m, CH2), 1.7 (2H, m, CH2), 1.9 (2H, m, CH2), 2.15 (2H, m, CH2), 7.20–7.75 (20H, m, Ph). δP (161.9 MHz, CDCl3, p.p.m.) 15.82–15.69 (d, PPh2), 33.04–33.24 (d, OPPh2).

Refinement top

H atoms were included in the refinement at calculated positions in the riding-model approximation.

Computing details top

Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1999); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: TEXSAN for Windows (Molecular Structure Corporation, 1999).; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON for Windows (Spek, 1999); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. The molecular configuration and atom-labelling scheme for (I). Ellipsoids are at the 30% probability level.
1-(Diphenylphosphino)-4-(diphenylphosphinoyl)butane top
Crystal data top
C28H28OP2Z = 1
Mr = 442.44F(000) = 234
Triclinic, P1Dx = 1.228 Mg m3
Hall symbol: -P 1Melting point = 463–464 K
a = 8.927 (2) ÅMo Kα radiation, λ = 0.71069 Å
b = 12.514 (3) ÅCell parameters from 25 reflections
c = 5.802 (2) Åθ = 12.6–17.2°
α = 102.98 (2)°µ = 0.20 mm1
β = 102.23 (3)°T = 295 K
γ = 100.71 (2)°Prismatic, colourless
V = 598.5 (3) Å30.50 × 0.20 × 0.15 mm
Data collection top
Rigaku AFC-7R
diffractometer
Rint = 0.026
Radiation source: Rigaku rotating anodeθmax = 27.5°, θmin = 2.6°
Graphite monochromatorh = 1111
ω–2θ scansk = 1615
3238 measured reflectionsl = 37
2752 independent reflections3 standard reflections every 150 reflections
2133 reflections with I > 2σ(I) intensity decay: 0.5%
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.048Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.154H-atom parameters constrained
S = 0.86 w = 1/[σ2(Fo2) + (0.1P)2 + 0.507P]
where P = (Fo2 + 2Fc2)/3
2752 reflections(Δ/σ)max < 0.001
145 parametersΔρmax = 0.28 e Å3
0 restraintsΔρmin = 0.28 e Å3
Crystal data top
C28H28OP2γ = 100.71 (2)°
Mr = 442.44V = 598.5 (3) Å3
Triclinic, P1Z = 1
a = 8.927 (2) ÅMo Kα radiation
b = 12.514 (3) ŵ = 0.20 mm1
c = 5.802 (2) ÅT = 295 K
α = 102.98 (2)°0.50 × 0.20 × 0.15 mm
β = 102.23 (3)°
Data collection top
Rigaku AFC-7R
diffractometer
Rint = 0.026
3238 measured reflections3 standard reflections every 150 reflections
2752 independent reflections intensity decay: 0.5%
2133 reflections with I > 2σ(I)
Refinement top
R[F2 > 2σ(F2)] = 0.0480 restraints
wR(F2) = 0.154H-atom parameters constrained
S = 0.86Δρmax = 0.28 e Å3
2752 reflectionsΔρmin = 0.28 e Å3
145 parameters
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
P10.65422 (6)0.83393 (5)0.03061 (11)0.0430 (2)
O10.6811 (5)0.8512 (3)0.2806 (6)0.0645 (9)0.50
C1A0.6990 (2)0.70021 (18)0.1015 (4)0.0462 (5)
C1B0.4514 (2)0.81581 (17)0.1441 (4)0.0416 (5)
C2A0.6673 (4)0.6513 (2)0.3496 (6)0.0734 (8)
C2B0.3325 (3)0.7541 (2)0.0705 (5)0.0579 (6)
C3A0.7037 (5)0.5488 (3)0.4348 (7)0.0904 (11)
C3B0.1752 (3)0.7383 (2)0.1886 (7)0.0725 (9)
C4A0.7705 (5)0.4955 (3)0.2796 (9)0.0884 (11)
C4B0.1349 (3)0.7840 (3)0.3795 (6)0.0742 (9)
C5A0.8059 (5)0.5434 (3)0.0369 (9)0.0923 (12)
C5B0.2503 (3)0.8458 (3)0.4539 (5)0.0712 (8)
C6A0.7702 (4)0.6462 (3)0.0565 (6)0.0698 (8)
C6B0.4085 (3)0.8611 (2)0.3378 (5)0.0570 (6)
C110.7732 (2)0.93418 (16)0.0831 (4)0.0400 (4)
C210.9487 (2)0.95868 (17)0.0481 (4)0.0417 (5)
H2A0.62100.68810.46170.088*
H2B0.35970.72310.06310.068*
H3A0.67980.51550.60590.108*
H3B0.09510.69490.14060.087*
H4A0.79340.42530.33820.106*
H4B0.02660.77430.45970.087*
H5A0.85560.50770.07700.111*
H5B0.22160.87700.58650.084*
H6A0.79500.67900.22860.083*
H6B0.48740.90320.39120.067*
H11A0.74000.99210.05840.044*
H11B0.75700.89370.27920.044*
H21A0.97550.88180.00230.044*
H21B0.96341.01030.22400.044*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
P10.0383 (3)0.0411 (3)0.0502 (3)0.0063 (2)0.0115 (2)0.0167 (2)
O10.077 (2)0.065 (2)0.0479 (19)0.0127 (18)0.0167 (17)0.0124 (17)
C1A0.0387 (10)0.0375 (10)0.0627 (14)0.0059 (8)0.0129 (9)0.0178 (10)
C1B0.0364 (10)0.0387 (10)0.0489 (11)0.0091 (8)0.0155 (8)0.0065 (9)
C2A0.098 (2)0.0522 (15)0.0722 (18)0.0282 (15)0.0218 (16)0.0150 (13)
C2B0.0476 (13)0.0491 (13)0.0816 (18)0.0100 (10)0.0287 (12)0.0177 (12)
C3A0.125 (3)0.0554 (17)0.097 (3)0.0284 (18)0.049 (2)0.0091 (17)
C3B0.0426 (13)0.0546 (15)0.114 (3)0.0030 (11)0.0322 (15)0.0065 (16)
C4A0.102 (3)0.0486 (16)0.138 (3)0.0318 (16)0.064 (2)0.0294 (19)
C4B0.0378 (12)0.0668 (17)0.093 (2)0.0117 (12)0.0041 (13)0.0143 (16)
C5A0.097 (3)0.075 (2)0.137 (3)0.050 (2)0.042 (2)0.057 (2)
C5B0.0582 (16)0.087 (2)0.0616 (16)0.0295 (15)0.0012 (13)0.0102 (15)
C6A0.0722 (18)0.0657 (17)0.0789 (19)0.0264 (14)0.0154 (15)0.0313 (15)
C6B0.0448 (12)0.0708 (16)0.0574 (14)0.0155 (11)0.0128 (10)0.0213 (12)
C110.0353 (10)0.0344 (10)0.0513 (12)0.0081 (8)0.0125 (8)0.0132 (8)
C210.0346 (10)0.0363 (10)0.0537 (12)0.0076 (8)0.0115 (9)0.0127 (9)
Geometric parameters (Å, º) top
P1—O11.379 (3)C11—C211.529 (3)
P1—C1A1.830 (2)C21—C21i1.531 (3)
P1—C1B1.823 (2)C2A—H2A0.9473
P1—C111.820 (2)C2B—H2B0.9490
C1A—C2A1.376 (4)C3A—H3A0.9466
C1A—C6A1.376 (4)C3B—H3B0.9444
C1B—C2B1.393 (3)C4A—H4A0.9440
C1B—C6B1.384 (3)C4B—H4B0.9520
C2A—C3A1.390 (5)C5A—H5A0.9567
C2B—C3B1.382 (4)C5B—H5B0.9479
C3A—C4A1.342 (6)C6A—H6A0.9503
C3B—C4B1.369 (5)C6B—H6B0.9474
C4A—C5A1.343 (7)C11—H11A0.8276
C4B—C5B1.374 (5)C11—H11B1.1028
C5A—C6A1.401 (6)C21—H21A1.0252
C5B—C6B1.387 (4)C21—H21B1.0448
O1—P1—C1A108.97 (19)C3B—C2B—H2B119.58
O1—P1—C1B117.0 (2)C2A—C3A—H3A119.29
O1—P1—C11118.56 (19)C4A—C3A—H3A119.30
C1A—P1—C1B102.84 (10)C2B—C3B—H3B120.41
C1A—P1—C11102.76 (10)C4B—C3B—H3B119.64
C1B—P1—C11104.76 (10)C3A—C4A—H4A121.13
P1—C1A—C2A123.81 (19)C5A—C4A—H4A119.61
P1—C1A—C6A118.1 (2)C3B—C4B—H4B120.19
C2A—C1A—C6A118.1 (2)C5B—C4B—H4B119.52
P1—C1B—C2B116.70 (18)C4A—C5A—H5A120.68
P1—C1B—C6B124.72 (18)C6A—C5A—H5A118.20
C2B—C1B—C6B118.6 (2)C4B—C5B—H5B119.84
C1A—C2A—C3A120.1 (3)C6B—C5B—H5B120.03
C1B—C2B—C3B120.7 (2)C1A—C6A—H6A119.70
C2A—C3A—C4A121.4 (4)C5A—C6A—H6A120.39
C2B—C3B—C4B119.9 (3)C1B—C6B—H6B119.99
C3A—C4A—C5A119.3 (4)C5B—C6B—H6B119.62
C3B—C4B—C5B120.3 (3)P1—C11—H11A106.17
C4A—C5A—C6A121.1 (4)P1—C11—H11B106.70
C4B—C5B—C6B120.1 (3)C21—C11—H11A111.35
C1A—C6A—C5A119.9 (3)C21—C11—H11B108.18
C1B—C6B—C5B120.4 (3)H11A—C11—H11B113.32
P1—C11—C21111.04 (15)C11—C21—H21A103.89
C11—C21—C21i111.89 (18)C11—C21—H21B106.15
C1A—C2A—H2A119.55H21A—C21—H21B127.48
C3A—C2A—H2A120.30C21i—C21—H21A108.14
C1B—C2B—H2B119.71C21i—C21—H21B99.18
O1—P1—C1A—C2A172.1 (3)C6A—C1A—C2A—C3A1.5 (5)
O1—P1—C1A—C6A8.7 (3)C2A—C1A—C6A—C5A1.0 (5)
C1B—P1—C1A—C2A47.3 (2)P1—C1B—C2B—C3B178.5 (2)
C1B—P1—C1A—C6A133.5 (2)C6B—C1B—C2B—C3B0.1 (4)
C11—P1—C1A—C2A61.3 (2)C2B—C1B—C6B—C5B0.5 (4)
C11—P1—C1A—C6A117.9 (2)P1—C1B—C6B—C5B177.7 (2)
O1—P1—C1B—C2B38.2 (3)C1A—C2A—C3A—C4A0.3 (6)
O1—P1—C1B—C6B140.1 (3)C1B—C2B—C3B—C4B0.3 (5)
C1A—P1—C1B—C2B81.2 (2)C2A—C3A—C4A—C5A1.4 (7)
C1A—P1—C1B—C6B100.6 (2)C2B—C3B—C4B—C5B0.2 (5)
C11—P1—C1B—C2B171.73 (18)C3A—C4A—C5A—C6A1.8 (7)
C11—P1—C1B—C6B6.5 (2)C3B—C4B—C5B—C6B0.8 (5)
O1—P1—C11—C2147.2 (3)C4A—C5A—C6A—C1A0.6 (6)
C1A—P1—C11—C2173.00 (16)C4B—C5B—C6B—C1B1.0 (5)
C1B—P1—C11—C21179.82 (17)P1—C11—C21—C21i178.99 (15)
P1—C1A—C6A—C5A179.7 (3)C11—C21—C21i—C11i180.0 (4)
P1—C1A—C2A—C3A179.3 (3)
Symmetry code: (i) x+2, y+2, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C6A—H6A···O10.952.532.933 (6)105
C11—H11B···O1ii1.102.413.473 (4)163
Symmetry code: (ii) x, y, z1.

Experimental details

Crystal data
Chemical formulaC28H28OP2
Mr442.44
Crystal system, space groupTriclinic, P1
Temperature (K)295
a, b, c (Å)8.927 (2), 12.514 (3), 5.802 (2)
α, β, γ (°)102.98 (2), 102.23 (3), 100.71 (2)
V3)598.5 (3)
Z1
Radiation typeMo Kα
µ (mm1)0.20
Crystal size (mm)0.50 × 0.20 × 0.15
Data collection
DiffractometerRigaku AFC-7R
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
3238, 2752, 2133
Rint0.026
(sin θ/λ)max1)0.650
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.048, 0.154, 0.86
No. of reflections2752
No. of parameters145
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.28, 0.28

Computer programs: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1999), MSC/AFC Diffractometer Control Software, TEXSAN for Windows (Molecular Structure Corporation, 1999)., SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), PLATON for Windows (Spek, 1999), SHELXL97.

 

Subscribe to Acta Crystallographica Section E: Crystallographic Communications

The full text of this article is available to subscribers to the journal.

If you have already registered and are using a computer listed in your registration details, please email support@iucr.org for assistance.

Buy online

You may purchase this article in PDF and/or HTML formats. For purchasers in the European Community who do not have a VAT number, VAT will be added at the local rate. Payments to the IUCr are handled by WorldPay, who will accept payment by credit card in several currencies. To purchase the article, please complete the form below (fields marked * are required), and then click on `Continue'.
E-mail address* 
Repeat e-mail address* 
(for error checking) 

Format*   PDF (US $40)
   HTML (US $40)
   PDF+HTML (US $50)
In order for VAT to be shown for your country javascript needs to be enabled.

VAT number 
(non-UK EC countries only) 
Country* 
 

Terms and conditions of use
Contact us

Follow Acta Cryst. E
Sign up for e-alerts
Follow Acta Cryst. on Twitter
Follow us on facebook
Sign up for RSS feeds