Bis­[2-(di­phenyl­phosphinoyl)­benzene] di­sulfide

The title compound, [2-Ph₂P(O)C₆H₄S]₂ or C₃₆H₂₈O₂P₂S₂, obtained by electrochemical oxidation of 2-(di­phenyl­phosphino)­benzene­thiol, has twofold crystallographic symmetry. Principal dimensions include S-S 2.0212 (15) Å, S-C 1.786 (3) Å and C-S-S-C 81.34 (14)°.

S1. Comment

Metal phosphinothiolate complexes can be easily prepared by an electrochemical procedure starting from a sacrificial metal anode in a cell containing the ligand in an appropriate solvent. In this way, the synthesis of Co, Ni (Perez-Lourido et al., 1998) and In (Perez-Lourido, Romero et al., 1999) compounds with 2-(diphenylphosphino)benzenethiol and similar ligands have been reported. In attempts to prepare gallium complexes by electrochemical oxidation of a gallium anode in an acetonitrile solution of 2-(diphenylphosphino)benzenethiol, white crystals of [2-Ph₂P(O)C₆H₄S]₂, (I), suitable for X-ray diffraction studies were isolated and its crystal structure determined. The compound is the result of the electrochemical oxidation of [2-Ph₂P—C₆H₄SH] to gave the disulfide in a process such as:

cathode: 2[2-Ph₂P—C₆H₄SH] + 2 e^- → H₂(g) + 2[2-Ph₂P—C₆H₄S]^-

anode: 2[2-Ph₂P—C₆H₄S]^- → [2-Ph₂PC₆H₄S]₂ + 2 e^-.

The structure of the compound shows that oxidation has ocurred at the P atom, and the source of oxygen is surely oxygen dissolved in acetonitrile. Such a facile oxidation of phosphine to phosphine oxides has been observed already in similar complexes (Block, Kang et al., 1989). The molecular structure is similar to related organic disulfide compounds such as bis(4,6-dimethylpyrimidyl) 2,2'-disulfide (Castro et al., 1995) and bis[6-(tert-butyldimethylsilyl)-2-pyridyl] disulfide (Tallon et al., 1995). The molecule shows a twofold axis through the S—S bond and it has an equatorial conformation with a torsion angle C2—S1—S1ⁱ—C2ⁱ of 81.34 (14)° [symmetry code: (i) -x, y, 3/2 - z]; this angle is within the 90±10° range found in most aromatic disulfides. In addition, the torsion angle C1—C2—S1—S1ⁱ is -172.9 (2)°. This value corresponds with an equatorial conformation in the Shefter classification (Shefter, 1970). The S1—S1ⁱ bond distance of 2.0212 (15) Å is close to the average value of 2.0 Å suggested for organic disulfides and almost equal to those found in bis[6-(tertbutyldimethylsilyl)-2-pyridyl] disulfide [2.032 (3) Å; Tallon et al., 1995] or in bis(4,6-dimethylpyrimidyl) 2,2'-disulfide, [2.017 (1) Å; Castro et al., 1995]. In addition, the C2—S1 bond length, [1.786 (3) Å] is similar to those found in other disulfides with an equatorial conformation (Highasi et al., 1978) and consistent with a C—S single bond. The P1—O1 bond distance [1.478 (2) Å] is almost equal to the distance observed in [2Ph₂P(O)6-(Me₃Si)—C₆H₃SH], [1.493 (3) Å; Perez-Lourido, Garcia-Vazquez et al., 1999] and in agreement with the value proposed for a P═O bond (Allen et al., 1987). The phenyl rings are practically flat with unremarkable bond distances and angles. Bond angles around the P atoms are in the range of 104.33 (12)–113.01 (12)° expected for a tetrahedral environment around a P atom.

S2. Experimental

The synthesis of 2-(diphenylphosphino)benzenethiol was carried out using slight modifications of the standard literature procedure involving lithiation of benzenethiol (Block, Ofori-Okai & Zubieta, 1989) using Schlenk techniques and dry solvents. The electrochemical procedure used was similar to described (Habbeb et al., 1978). A solution containing 0.20 g of the ligand in 50 ml of acetonitrile and a few mg of tetramethylammonium perchlorate as electrolytic support was electrolyzed in a cell with a gallium anode and a platinum cathode over a period of 2 h using 20 mA of intensity. No metal was found to be dissolved from the anode. The resultant solution was filtered off and then air concentrated. White crystals of [2-Ph₂P(O)C₆H₄S]₂, suitable for X-ray diffraction studies were isolated.

Computing details

Data collection: Nonius CAD-4 Software; cell refinement: Nonius CAD-4 Software; data reduction: Nonius CAD-4 Software; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997).

Bis[2-(diphenylphosphinyl)benzene] disulfide

Crystal data

C36H28O2P2S2	F(000) = 1288
Mr = 618.64	Dx = 1.399 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 13.249 (3) Å	Cell parameters from 25 reflections
b = 10.801 (2) Å	θ = 12.5–16.1°
c = 21.193 (5) Å	µ = 0.32 mm^−1
β = 104.50 (2)°	T = 203 K
V = 2936.3 (11) Å^3	Plate, light brown
Z = 4	0.25 × 0.25 × 0.20 mm

Data collection

Nonius CAD-4 MACH-3 diffractometer	Rint = 0.024
Radiation source: fine-focus sealed tube	θmax = 25.0°, θmin = 2.0°
Graphite monochromator	h = 0→15
ω–2θ scans	k = 0→12
2697 measured reflections	l = −25→24
2575 independent reflections	6 standard reflections every 150 reflections
1848 reflections with I > 2σ(I)	intensity decay: none

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)] = 0.042	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.091	H atoms treated by a mixture of independent and constrained refinement
S = 1.03	w = 1/[σ^2(Fo^2) + (0.0376P)^2 + 1.9871P] where P = (Fo^2 + 2Fc^2)/3
2575 reflections	(Δ/σ)max < 0.001
246 parameters	Δρmax = 0.29 e Å^−3
0 restraints	Δρmin = −0.24 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.

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

	x	y	z	Uiso*/Ueq
P1	0.20423 (5)	0.09582 (7)	0.62966 (3)	0.02145 (19)
S1	0.05358 (6)	0.16905 (7)	0.72343 (4)	0.0308 (2)
O1	0.18759 (14)	0.22402 (17)	0.60483 (9)	0.0272 (5)
C1	0.0824 (2)	0.0170 (3)	0.62503 (13)	0.0217 (6)
C2	0.0158 (2)	0.0485 (3)	0.66455 (13)	0.0233 (6)
C3	−0.0805 (2)	−0.0092 (3)	0.65439 (14)	0.0281 (7)
C4	−0.1118 (2)	−0.0952 (3)	0.60562 (15)	0.0311 (7)
C5	−0.0485 (2)	−0.1240 (3)	0.56540 (15)	0.0306 (7)
C6	0.0481 (2)	−0.0697 (3)	0.57568 (14)	0.0264 (7)
C7	0.2751 (2)	0.0048 (3)	0.58403 (13)	0.0226 (6)
C8	0.3053 (3)	−0.1173 (3)	0.59921 (16)	0.0386 (8)
C9	0.3626 (3)	−0.1794 (4)	0.56282 (18)	0.0473 (9)
C10	0.3890 (3)	−0.1210 (4)	0.51195 (18)	0.0453 (9)
C11	0.3601 (2)	−0.0010 (3)	0.49675 (16)	0.0376 (8)
C12	0.3035 (2)	0.0618 (3)	0.53276 (14)	0.0271 (7)
C13	0.2822 (2)	0.0876 (3)	0.71241 (13)	0.0224 (6)
C14	0.2890 (2)	−0.0178 (3)	0.75031 (15)	0.0295 (7)
C15	0.3567 (3)	−0.0215 (3)	0.81182 (15)	0.0337 (8)
C16	0.4173 (2)	0.0798 (3)	0.83487 (16)	0.0369 (8)
C17	0.4101 (2)	0.1852 (3)	0.79789 (16)	0.0371 (8)
C18	0.3428 (2)	0.1892 (3)	0.73651 (14)	0.0272 (7)
H3	−0.125 (2)	0.013 (3)	0.6827 (14)	0.038 (9)*
H4	−0.174 (2)	−0.133 (2)	0.5992 (12)	0.016 (7)*
H5	−0.070 (2)	−0.179 (3)	0.5351 (15)	0.039 (9)*
H6	0.091 (2)	−0.089 (3)	0.5485 (14)	0.030 (8)*
H8	0.286 (2)	−0.155 (3)	0.6338 (15)	0.040 (9)*
H9	0.381 (2)	−0.265 (3)	0.5737 (15)	0.043 (9)*
H10	0.427 (2)	−0.170 (3)	0.4886 (15)	0.043 (9)*
H11	0.379 (2)	0.040 (3)	0.4617 (14)	0.032 (8)*
H12	0.286 (2)	0.152 (3)	0.5236 (13)	0.025 (8)*
H14	0.248 (2)	−0.087 (3)	0.7335 (13)	0.030 (8)*
H15	0.362 (2)	−0.092 (3)	0.8342 (15)	0.038 (9)*
H16	0.467 (2)	0.074 (3)	0.8766 (15)	0.039 (9)*
H17	0.450 (2)	0.255 (3)	0.8130 (13)	0.030 (8)*
H18	0.336 (2)	0.263 (3)	0.7095 (14)	0.035 (8)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
P1	0.0202 (4)	0.0219 (4)	0.0230 (4)	−0.0029 (3)	0.0068 (3)	−0.0001 (3)
S1	0.0304 (4)	0.0303 (4)	0.0372 (5)	−0.0072 (3)	0.0185 (3)	−0.0066 (3)
O1	0.0265 (10)	0.0226 (11)	0.0333 (11)	−0.0033 (9)	0.0090 (9)	0.0013 (9)
C1	0.0184 (13)	0.0235 (15)	0.0213 (15)	−0.0012 (12)	0.0012 (11)	0.0072 (12)
C2	0.0233 (15)	0.0218 (15)	0.0242 (15)	−0.0003 (12)	0.0047 (12)	0.0045 (12)
C3	0.0216 (15)	0.0334 (18)	0.0301 (17)	−0.0017 (14)	0.0080 (13)	0.0075 (14)
C4	0.0198 (15)	0.0375 (18)	0.0316 (17)	−0.0105 (15)	−0.0019 (13)	0.0092 (15)
C5	0.0335 (17)	0.0272 (17)	0.0262 (17)	−0.0077 (14)	−0.0016 (14)	0.0018 (14)
C6	0.0259 (15)	0.0315 (18)	0.0217 (15)	−0.0016 (13)	0.0056 (13)	0.0015 (13)
C7	0.0202 (14)	0.0251 (16)	0.0219 (15)	−0.0018 (12)	0.0040 (12)	−0.0029 (12)
C8	0.052 (2)	0.034 (2)	0.0339 (19)	0.0085 (16)	0.0180 (16)	0.0042 (15)
C9	0.057 (2)	0.035 (2)	0.051 (2)	0.0164 (18)	0.0161 (19)	0.0020 (18)
C10	0.044 (2)	0.052 (2)	0.045 (2)	0.0121 (18)	0.0204 (17)	−0.0075 (18)
C11	0.0386 (19)	0.048 (2)	0.0312 (18)	−0.0029 (16)	0.0183 (15)	−0.0009 (16)
C12	0.0242 (15)	0.0311 (18)	0.0256 (16)	−0.0025 (13)	0.0054 (12)	−0.0014 (13)
C13	0.0210 (14)	0.0245 (15)	0.0237 (14)	−0.0028 (13)	0.0092 (11)	−0.0045 (13)
C14	0.0325 (17)	0.0247 (16)	0.0322 (18)	−0.0038 (14)	0.0097 (14)	0.0002 (14)
C15	0.0426 (19)	0.0316 (19)	0.0276 (18)	0.0067 (16)	0.0103 (15)	0.0069 (15)
C16	0.0302 (17)	0.053 (2)	0.0250 (17)	0.0034 (17)	0.0024 (14)	−0.0025 (17)
C17	0.0333 (18)	0.044 (2)	0.0329 (19)	−0.0147 (17)	0.0067 (15)	−0.0090 (16)
C18	0.0308 (16)	0.0267 (17)	0.0250 (16)	−0.0051 (13)	0.0088 (13)	−0.0028 (13)

Geometric parameters (Å, º)

P1—O1	1.478 (2)	C7—C12	1.381 (4)
P1—C7	1.800 (3)	C7—C8	1.392 (4)
P1—C13	1.801 (3)	C8—C9	1.383 (5)
P1—C1	1.806 (3)	C9—C10	1.368 (5)
S1—C2	1.786 (3)	C10—C11	1.367 (5)
S1—S1^i	2.0212 (15)	C11—C12	1.375 (4)
C1—C6	1.392 (4)	C13—C18	1.380 (4)
C1—C2	1.402 (4)	C13—C14	1.383 (4)
C2—C3	1.387 (4)	C14—C15	1.386 (4)
C3—C4	1.374 (4)	C15—C16	1.373 (5)
C4—C5	1.374 (4)	C16—C17	1.372 (5)
C5—C6	1.375 (4)	C17—C18	1.381 (4)
O1—P1—C7	111.84 (12)	C12—C7—C8	119.0 (3)
O1—P1—C13	113.01 (12)	C12—C7—P1	117.4 (2)
C7—P1—C13	104.33 (12)	C8—C7—P1	123.5 (2)
O1—P1—C1	111.76 (12)	C9—C8—C7	119.8 (3)
C7—P1—C1	107.00 (13)	C10—C9—C8	120.0 (3)
C13—P1—C1	108.46 (12)	C11—C10—C9	120.8 (3)
C2—S1—S1^i	106.02 (9)	C10—C11—C12	119.8 (3)
C6—C1—C2	118.5 (2)	C11—C12—C7	120.7 (3)
C6—C1—P1	118.5 (2)	C18—C13—C14	119.5 (3)
C2—C1—P1	122.7 (2)	C18—C13—P1	117.4 (2)
C3—C2—C1	119.3 (3)	C14—C13—P1	123.0 (2)
C3—C2—S1	121.5 (2)	C13—C14—C15	120.2 (3)
C1—C2—S1	119.1 (2)	C16—C15—C14	119.7 (3)
C4—C3—C2	120.9 (3)	C17—C16—C15	120.4 (3)
C5—C4—C3	120.2 (3)	C16—C17—C18	120.0 (3)
C4—C5—C6	119.6 (3)	C13—C18—C17	120.2 (3)
C5—C6—C1	121.4 (3)

Symmetry code: (i) −x, y, −z+3/2.