Z. anorg. allg. Chem. 621 (1995) 1672-1676

Zeitschrift fur anorganische und allgemeine Chemie 0 Johann Ambrosius Barth 1995

Preparation and X-Ray Structural Analysis of the Remarkably Stable Bis( trip henylmet hy1)trisulf ane-2-oxide R,S,O [ 1 ]

Markus Pridohl and Ralf Steudel"

Berlin-Charlottenburg, Institut fur Anorganische und Analytische Chemie, Technische Universitat

Jiirgen Buschmann and Peter Luger

Berlin-Dahlem, Institut fur Kristallographie, Freie Universitat

Received April 11 th, 1995.

Abstract. Triphenylmethylthiol reacts with thionylchloride in and 21 1.4(1) pm, do = 188.0(2) and 188.2(2) pm, the presence of amines to give [(C6H5)3CS],so which dso = 146.9(1) pm, asss = 83.8", asso = 112.0" and 112.2", crystallizes with one mole of CS2 in the triclinic space group P I with a = 1193.4(4), b = 1266.8(5), c = 1421.6(7)pm, a = 63.79(2)", /3 = 65.25(2)", y = 63.18(2)", p = 1 .354g~rn -~ at - 80 "C. The R,S30 molecules are of C, symmetry contain- Keywords: X-ray crystallography; dithiosulfite; vibrational ing an almost planar CSSSC backbone with dss = 212.7(1)

scsss = 160.7" and - 172.3".

spectra; sulfane oxide

Darstellung und Rontgenstrukturanalyse des bemerkenswert stabilen Bis(triphenylmethyl)trisulfan-2-oxids R,S,O [I] Inhaltsiibersicht. Triphenylmethylthiol reagiert in Gegenwart von Aminen mit Thionylchlorid zu [(C~H~),CS]ZSO, das als Solvat mit 1 Mol CS, kristallisiert: triklin, Raumgruppe P I mit a = 1193,4(4), b = 1266,8(5), c = 1421,6(7)pm, a = Abstract angegebenen geometrischen Parametern.

63,79(2)", p = 65,25(2)", y = 63,18(2)", p = 1,354 g ~ r n - ~ bei - 80 "C. Das Trisulfanoxidmolekul R2S30 ist von C,-Symme- trie und weist ein fast planares Gerust CSSSC auf mit den im

Introduction

Bis(organyl)trisulfane-2-oxides R-S-S(0)-S-R, also termed as dithiosulfites, are usually prepared from thiols and thionylchloride in the presence of a base like diethylether or pyridine [2]:

2 RSH + SOCli + RS-S(0)-SR + 2 HCl (1)

Starting from dithiols or their sodium salts cyclic trisulfane-2-oxides can be prepared [3]:

(2) R'SH The latter reaction may be modified by first preparing the titanocene derivative of the dithiol and then reacting this complex with thionylchloride (Cp = q 5-C,H,) [4]:

SH - + SOC1, + RS-S(0)-S + 2 HCl

R(SH), + Cp2TiC1 + Cp2Ti < > R + 2HC1 (3) S - -

Cp2Ti < > R + SOC12 --* Cp2TiC12 + RS-S(0)-S (4)

Attempts to prepare trisulfane oxides by oxidation of trisulfanes by peroxyacids usually result in the formation of trisulfane-I-oxides [ 5 , 61:

RS-S-SR + [O] + RS(0)-S-SR (5 )

Both chain-like and cyclic trisulfane-1-oxides have been obtained in this way. However, if the trisulfane group is part of a five-membered ring as in trithiolanes or ben- zotrithiole derivatives, the oxidation by peroxyacids results in mixtures of trisulfane-I -oxides and 2-oxides[7, 81:

M. Pridohl et al., Bis(triphenylmethyl)trisulfane-2-oxide 1673

The thermal stability of trisulfane-2-oxides very much depends on the nature of the substituents and bulky groups R are necessary to assure stability at 20°C [2]. This behavior is explained by the bimolecular decomposi- tion which results in SO, and di- as well as trisulfanes:

2(RS)zSO+SOz + RzSz + R2S3 (8)

An ionic mechanism has been postulated for reaction (8) 121.

One of the bulkiest stubstituents is the triphenylmethyl (trityl, Tr) group and it was to be expected that (TrS),SO would be a stable compound. However, in the pioneering publication on dithiosulfites by Field and Lacefield [2] it was reported that (TrS),SO contained in a crude product prepared from TrSH and SOC1, decomposed at 100°C with a half-life of 15 min, while ('BuS),SO showed a half-life of >22 h! Pure (TrS),SO has never been prepared and we suspected that some impurity was responsible for its rapid decomposition in the above crude product. Therefore, we have synthesized (TrS),SO and investigated its structure by X-ray diffraction as well as its general properties.

Results and Discussion

Addition of thionylchloride to a solution of triphenylmethylthiol and triethylamine (molar ratio 1 : 2 : 2) results in (TrS),SO which was isolated as col- orless crystals of melting point 148 "C (yield 21 Yo). Analysis of the product by reversed-phase HPLC showed only one peak at a retention index (RS value) of 616. Ex- pectedly, the retention of (TrS),SO is weaker than that of the reference sample Tr,S, (RS = 691) because of the better solubility of (TrS),SO in the polar eluent (methanol) [9].

Neither refluxing of (TrS),SO in CS, for several hours nor storage of solid (TrS),SO at 4°C for 3 months did result in any measurable decomposition. However, on melting the compound decomposes to a mixture of polysulfanes Tr,S, and SO,.

From CS, the trisulfane-2-oxide crystallizes as solvate Tr,S,O - CS,. To prevent these crystals from loss of sol- vent molecules, the crystal structure determination by X- ray diffraction was carried out at a sample temperature of -80°C. Crystal data and experimental details of the structure determination are given in Table I . The reflec- tion intensities were Lp corrected and scaled according to the change in the check reflections. There was a con- tinuous decrease in their intensity of 11 070 over the time of the measurement. About every 18 hours the orienta- tion reflections were automatically recentered, giving a new cell and orientation matrix. Five reflections were badly measured and removed. The structure solution was done by the direct methods program SHELXS [lo]. The refinement of the atomic parameters made use of the coefficients for anomalous scattering [I I] for C, 0 and S. All hydrogen atoms were easily found in the difference

Table 1 Crystal Data and Experimental Details of the Struc- ture Determination

Empirical formula Molecular mass Temperature Radiation Wavelength Crystal system Space group Unit cell dimensions

Volume Z Density (calc.) Absorption coefficient F(0W Crystal size Data collection instrument

Orientation reflections number, range (28, ") Scan method, steps (") Scan width (") Scan rate (w, "/mi@ to reach I/a(I) 2 25 within the rate interval Standard reflections measured every 90 min

0 range for data collection Index ranges

Reflections collected Independent reflections Refinement method

Data/restraints/parameters Refinded factors in weight formula ") Goodness-of-fit on F2 h, Final R indices [I > 2a(I)]

R indices (all data) Largest diff. peak and hole

C&mS,O CSz 674.93 - 80( 1) "C MoKa, Nb filter 71.068 pm triclinic P1 a = 1193.4(4)pm b = 1266.8(5) pm c = 1421.6(7) pm CY = 63.79(2)" fi = 65.25(2)O y = 63.18(2)" 1654.9(12) . 106pm3 2 1.354 g cm-3 0.382 mm-' 704 0.60x0.50x0.30 mm SIEMENS-four-circle diffractometer with open x circle and Nz gas stream device [23]

34, 23.1 -41.7 2 0-0, 0.04 -0.02 Aw = 1.00 + 0.52 tan w 0.67 -4.00

-6 -5 -8 -7 2 3

2 7 4 2.02 - 36.03" -17 5 h I 19

O s k 1 2 0 -20 I 1 I 23 15 695 15 695 full-matrix least-squares on FZ with SHELX 93 [24] 15 695/0/526

0.0673, 0.0000 0.954 RI') = 0.0439; w R ~ ~ ) = 0.1146 8 776 reflections R1 = 0.1039; wR2 = 0.1267 0.440 and -0.574 e k3

") w = l/[aZ(Fi) + (f,P)* + f2P], with P = (max(fz,O) + 2Fz)/3 ') S = [ZW(IF, I * - I F c I 2)2/No~s - Nparamet&)]1'2 ") R = ZIIF,I - IFcII/ZIFoI ') wR2 = [Zw(IF,l2 - IF,Iz)2/Z~lFo14]"2

Fourier synthesis map. The atomic coordinates and ther- mal parameters are given in Tables 2 and 3. Important in- ternuclear distances, bond angles and torsion angles are given in Table4 [12]. In Fig. 1 the conformation of the (TrS),SO molecule (symmetry C,) as well as the orienta-

1674 Z. anorg. allg. Chem. 621 (1995)

Table 2 Selected atomic coordinates ( x 104) and equivalent isotropic displacement parameters (A2 x lo3) of (Ph3C)2S30. U(eq) is defined as one third of the trace of the orthogonalized Uij tensor

Atom X Y Z

lOO(1)

- 2 210( 1) 1 529(1) 2686(1) 1 520(1) 1519(1)

- 1393(1) -2 180(1)

- 3 621( 1) - 3 689( 1) -4898(1) -3276(1)

2144(1) 861(2)

-448(1)

3247(1) 2 526( 1) 3241(1) 3 190( 1) 2 437( 1) 2451(1) 3 197(1) 1124(1) 2578(1) 2473(1) 3514(1) 1 329( I) 2 041 ( 1) 1885(2) 1755(1)

6 001 ( 1) 6385(1) 5 602( 1) 7 737(1) 5041(1) 5253(1) 3 853(1) 5341(1) 8 592(1) 9732(1) 8319(1) 8457(1) 8 129( I) 8 974(2) 9 810(1)

Table 3 Selected anisotropic displacement parameters (A2 x lo3) of (Ph3C)&0. The anisotropic displacement factor exponent takes the form: -2nZ[h2a*2U11 + . - . + 2hka*b*U12]

Ul l u22 u33 U23 U13 u12

- 17(1) - 13(1) - 16(1) - 15(1) -11(1) - lO(1) - lO(1) - lO(1) -7(1) - lO(1) - ll(1) -9(1)

- 12(1) - 14(1)

- 14(1)

-9(1) -8(1) - 12(1)

-4(1) - 7(1) -6(1) -5(1) - lO(1) - lO(1) - lO(1)

- lO(1) -2(1)

-21(1)

- 14(1)

-15(1)

tion of the solvate molecule are shown. The molecular parameters of the triphenylmethyl groups are normal and may be compared to those of Tr,S, and Tr,S, [13]. However, the structure of the central unit C-S-S(0)-S-C shows a number of remarkable features. The CSSSC chain is almost planar with the torsional angles r(C2O-S3-S2--Sl) = - 172.3" and t(CI-Sl-S2-S3) = 160.7". The oxygen atom is above this plane with t(C20-S3-S2-0) = 76.2" and t(C1-S1-S2-0) = -88.0". This conformation of the C,S,O group is not surprizing. First, the parent com- pound H,S,O (trisulfane-2-oxide), according to high- level ab-initio MO calculations [14], adopts a conforma- tion of C, symmetry with t(HSSS) = 167.1" and 159.3",

Table 4 Important internuclear distances, bond angles and torsional angles of (TrS@O CS2; for numbering of atoms see Fig. 1. Standard deviations are given in brackets

Internuclear c1-s1 s1-s2 s2-0 S2-S3 C20-S3 c39-s4 c39-s5

distances (pm) 152.8(2) 188.0(1) Cl-Cl4 153.2(2) 212.66(8) Cl-C8

146.9(1) Cl-C2 154.2(2) 152.5(2) 152.9(2) 188.2(1) C20-C27 153.6(2) 153.3(3) C20-C21

154.4(3)

21 1.4( 1) C20-C32

Bond angles (") C1-Sl-S2 S3-S2-0 Sl-S2-0 Sl-S2-S3 c2o-s3-s2 C14-Cl-C8 c14-c1 -c2 C8-C1 -C2

104.66(5) 11 1.99(6) 112.19(5) 83.83(3)

104.1 l(5) 112.4(1) 113.2(1) 109.0(1)

c14-c1-s1 C8-C 1 -S 1 c2-c1-s1 c21-c2o-c33 c21-c2o-c27 c27-c2o-c33 c33-c2o-s3 c 2 1 -c20-s3 c27-c2o-s3

109.37(9) 110.94(9) 101.44(8) 113.5(1) 109.0(1) 112.6(1) 108.69(9) 100.55(8) 111.93(9)

Torsional angles (") c1-s1 -s2-0 - 88.02(7) C8-Cl-Sl-S2 91.74(9) c1-s1-s2-s3 160.71(4) C2-Cl-Sl-S2 - 152.59(7) c20-s3-s2-0 76.20(7) C33-C2O-S3-S2 32.26(9) C2O-S3-S2-Sl - 172.33(4) C27-C2O-S3-S2 - 92.70(9) C14-C20-Sl-S2 - 32.79(9) C21-C2O-S3-S2 151.70(7)

respectively, and t(HSS0) = 54.5" and -89.7". Second, the other two chain-like organic trisulfane-2-oxides R,S,O which have been structurally characterized (R = 4-chlorophenyl [I51 and R = phenyl [16]) show very similar geometries as (TrS),SO. Although the trisulfane molecule H,S, [I71 adopts either a helical con- formation (C, symmetry) or, less stable, a structure with both hydrogens on the same side of the S, plane (C, symmetry), the addition of an oxygen atom to the central sulfur atom changes the structure of the XSSSX backbone dramatically towards an almost planar ar- rangement. Simultaneously, the SS bond distances in- crease from the single bond value of 205 pm [I81 to 212.7 and 211.4 pm in (TrS),SO, 212.5 pm in (ClC,H,S),SO [I51 and 212.4/214.1 pm in (PhS),SO [16]. The SO bond lengths in these organic trisulfane-2-oxides are in the range 144.9- 147.6 pm.

Another remarkable feature of (TrS),SO are the two rather long CS bonds of 188.0 and 188.2 pm, almost as long as in Tr,S, (191.2/195.2) [I91 and in Tr,s, (190.3/191.2) [13]. It therefore can be expected that (TrS),SO on heating will dissociate at one of the CS bonds to form the radicals Tr' and TrS,O' which will then further react to give SO, and Tr,S,. The bimolecular reaction (8) is less likely in the case of R = Tr since the bulky trityl groups presumably prevent a close approach of the two S,O groups which is necessary to form SO,. In fact, in crystalline (TrS),SO * CS, there are

M. Pridohl et al., Bis(triphenylmethyl)trisulfane-2-oxide 1675

Fig. 1 Structure of the bis(triphenylmethyl)trisulfane-2-oxide and carbondisulfide molecules in solid (TrS),SO * CS, at - 80 "C and numbering of atoms (SCHAKAL plot) [22]

Shorter S * - * S contacts exist between (TrS),SO and CS, molecules (shortest: 366.5 pm between S3 and S5) .

The bulky trityl groups may also be responsible for the extremely small SSS bond angle of 83.83", which is con- siderably smaller than in H,S,O (88.1") [14], (ClC,H,S),SO (91.3') [I51 and (PhS),SO (88.3") [16] and which may even be the smallest SSS angle ever observed in a chain-like compound. Most likely a better packing is reached in this way between the two trityl substituents of the trisulfane oxide. The incorporation of a solvate molecule (CS,) is probably another conse- quence of the tendency to obtain a better space filling.

Experimental [20]

Bis(triphenylmethyl)trisulfane-2-oxide was prepared by addi- tion of 0.431 g SOCl, (3.62mmol), dissolved in 20ml of dry CS2 to a solution of 2.00g TrSH (7.24mmol) and 0.73g triethylamine (7.2 mmol) in 20 ml CS, at 0 "C. After stirring for 30 min the precipitated Et3NHCl is sucked off and washed with CS,, and the orange filtrate is reduced to ca. 20% of its original volume in a vacuum and cooled to - 50 "C. After 12 h the crystals of (TrS),SO. CS, are isolated and dried in a vacuum at 23 'C; yield 901 mg (21 Vo). C38H30S30 (598.85): C 75.04 (calc. 76.22), H 4.86 (5.05), S 15.99 (16.06). IR spec- trum (KBr disc; range < 1 500 em-'): 1 491 s, 1 443 s, 1 321 vw, 1186w, 1163vw, 1117m, 1086vw, 1035w, lOOSvw, 887vw,

This work was supported by the Deutsche Forschungsge- meinschaft and the Verband der Chemischen Industrie.

References

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1676 Z. anorg. allg. Chem. 621 (1995)

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[I21 Further details of the crystal structure are available on re- quest from the Fachinformationszentrum Karlsruhe, Gesellschaft fur wissenschaftlich-technische Information mbh, D-76344 Eggenstein-Leopoldshafen, on quoting the depository number CSD-401555

[I31 M. Kustos, J. Pickardt, .l Albertsen, R. Steudel, Z. Naturforsch. 48b (1993) 928

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[19] M. Ostrowski, J . Jeske, €? G. Jones, W-U.: duMont, Chem. Ber. 126 (1993) 1355

[20] For further details see M. Pridohl, Doctoral Dissertation, Techn. Univ. Berlin 1994

[21] M. Pridohl, R. Steudel, E Baumgart, Polyhedron 12 (1993) 2577

[22] E. Keller, SCHAKAL88, Graphics program for molecular and crystallographic models, Albert-Ludwigs-Universitat, Freiburg, Germany 1988

[23] H. Dietrich, H. Dierks, MeDtechnik (Braunschweig) 78 (1970) 184

[24] SHELX-93, G. M. Sheldrick, (1994). In preparation for J. Appl. Crystallogr.

Address of authors:

Prof. Dr. R. Steudel, Dr. M. Pridohl Institut fur Anorganische und Analytische Chemie Technische Universitat Berlin, Sekr. C 2 D-10623 Berlin-Charlottenburg

Prof. Dr. P. Luger, Dr. J. Buschmann Institut fur Kristallographie Freie Universitat Berlin Takustr. 6 D-14195 Berlin-Dahlem