Intramolecular S···S and S···O close contacts in 1,8-bis(phenylsulfanyl)naphthalene derivatives of different sulfur valence state: An X-ray study

Article abstract of DOI:10.1016/S0022-2860(01)00821-3

Four peri-substituted naphthalene derivatives, 1,8-bis(phenylsulfanyl)naphthalene (1), 1,8-bis[(2-methoxycarbonylphenyl)sulfanyl]naphthalene (2), bis[(2-methoxycarbonyl-phenyl)-sulfinyl]naphthalene (3) and bis[(2-methoxycarbonylphenyl)sulfonyl]naphthalene (4) with different valence states of sulfur were prepared and their molecular structures determined by X-ray diffraction. Data were collected on CAD-4 diffractometers with monochromated MoKα and CuKα radiations. Naphthalene ring torsions, aromatic ring orientations, S···S and S···O close contacts were analyzed and the controlling factors established. In both halves of the molecules, the naphthyl and phenyl rings assume axial-equatorial positions in bis-sulfides 1 and 2, and twist-axial positions in bis-sulfoxide 3 and bis-sulfone 4. The S···S distance was found to be 3.01, 3.18; 3.01 and 3.53 A?, for 1, 2, 3 and 4, respectively. The equatorial S-phenyl rings in 2 and the steric crowd in 4 are unfavorable factors for S···S contacts. As expected, S(II)···O and S(IV)···O close contacts are formed in the equatorial and axial S-phenyl rings of 2 and 3, respectively, with 2.72, 2.73 and 2.77, 2.83 A? distances. Steric repulsion in bis-sulfone 4 is moderated by two C(ar)-S(VI)···O(sulfonyl) type close contacts (2.89 and 3.02 A?), which join the two halves of the molecule.

Full text of DOI:10.1016/S0022-2860(01)00821-3

Journal of Molecular Structure 606 (2002) 61±76
www.elsevier.com/locate/molstruc
Intramolecular S´´´S and S´´´O close contacts in
1,8-bis(phenylsulfanyl)naphthalene derivatives of different
sulfur valence state: an X-ray study
a,b
Peter Nagy , Denes Szabo , Istvan Kapovits , Arpad Kucsman , Gyula Argay ,
a
a
b
Âa,
Â
Alajos Kalman
Â
Â
*
Â
Â
b
Â
Â
a
È È
Â
Department of Organic Chemistry, Eotvos Lorand University, PO Box 32, H-1518 Budapest 112, Hungary
bInstitute of Chemistry, Chemical Research Center, Hungarian Academy of Sciences, PO Box 17, H-1525 Budapest 114, Hungary
Received 24 April 2001; revised 16 July 2001; accepted 16 July 2001
Abstract
Four peri-substituted naphthalene derivatives, 1,8-bis(phenylsulfanyl)naphthalene (1), 1,8-bis[(2-methoxycarbonylphe-
nyl)sulfanyl]naphthalene (2), bis[(2-methoxycarbonyl-phenyl)-sul®nyl]naphthalene (3) and bis[(2-methoxycarbonylphe-
nyl)sulfonyl]naphthalene (4) with different valence states of sulfur were prepared and their molecular structures
determined by X-ray diffraction. Data were collected on CAD-4 diffractometers with monochromated MoKa and CuKa
radiations. Naphthalene ring torsions, aromatic ring orientations, S´´´S and S´´´O close contacts were analyzed and the
controlling factors established. In both halves of the molecules, the naphthyl and phenyl rings assume axial±equatorial
positions in bis-sul®des 1 and 2, and twist-axial positions in bis-sulfoxide 3 and bis-sulfone 4. The S´´´S distance was found
Ê
to be 3.01, 3.18; 3.01 and 3.53 A, for 1, 2, 3 and 4, respectively. The equatorial S-phenyl rings in 2 and the steric crowd in 4
are unfavorable factors for S´´´S contacts. As expected, S(II)´´´O and S(IV)´´´O close contacts are formed in the equatorial
Ê
and axial S-phenyl rings of 2 and 3, respectively, with 2.72, 2.73 and 2.77, 2.83 A distances. Steric repulsion in bis-sulfone 4
Ê
is moderated by two C(ar)±S(VI)´´´O(sulfonyl) type close contacts (2.89 and 3.02 A), which join the two halves of the
molecule. q 2002 Elsevier Science B.V. All rights reserved.
Keywords: Crystal structures; S´´´S and S´´´O nonbonded interaction; Conformation
1. Introduction
N) were determined by X-ray diffraction. Among
them a great number of structures with sulfur±oxygen
close contacts can be found in which the S´´´O
distances are longer than the usual S±O hypervalent
Ê
bonds (1.66±2.05 A) but shorter than the sum of the
Ê
van der Waals radii (3.25 A) [2]. Following our ®rst
experimental work published in 1977±1980 [3,4], we
later systematically studied how S´´´O close contacts
control the actual conformation of sul®des and disul-
®des [5], sulfoxides [6±8], sul®limines [6±8,10]
Since the pioneering work of Bezzi et al. [1], nearly
thousand structures exhibiting intramolecular X±
S´´´Y close contact appreciably shorter than the sum
of the van der Waals radii of S and Y (Y ˆ O; S, Se,
* Corresponding author. Tel.: 136-1209-0555; fax: 136-1372-
2620.
Â
E-mail address: szabod@szerves.chem.elte.hu (D. Szabo).
0022-2860/02/$ - see front matter q 2002 Elsevier Science B.V. All rights reserved.
PII: S0022-2860(01)00821-3

62
P. Nagy et al. / Journal of Molecular Structure 606 (2002) 61±76
calculations and later on by the ab initio SCF±MO
method [20]. Systematic calculations showed that
the attractive S´´´O interaction can be regarded as a
weak hypervalent bond like that in unsymmetrical
spiro-l4-sulfanes, and its extent may be well corre-
lated with the shortening of the S´´´O distance. From
experimental facts and calculations, we concluded
that the S´´´O interaction is rather strong in
compounds characterized by a general formula
shown in Scheme 1 where (i) X is an electronegative
or polarizable atom (e.g. O and S are more effective
than C) and the X±S´´´O sequence is nearly linear
(lone-pair delocalization to the sXp ±S antibonding
orbital); (ii) in the conjugated sequence A ˆ Csp2;
B, Y ˆ Csp2 or Nsp2, Z ˆ OꢀR†; N(R2), C(R3), H or
lone pair, and the ®ve-membered conjugated ring
closed by S´´´O contact is planar (quasi-aromatic
Scheme 1. General formula for compounds exhibiting effective
intramolecular S´´´O nonbonded interaction (see text).
sulfenyl compounds, sul®nates and sulfonates [9],
alkoxy- [11] and acylamino(diaryl) sulfonium salts
[12,13] and spiro-l4-sulfanes [11,12,14]. We also
experienced that reactivity in some cases is signi®cantly
affected by intramolecular S´´´O nonbonded interac-
tion [15±18]. The quantum chemical interpretation of
the nature of the S´´´O interaction was attempted ®rst
by semiempirical (e.g. extended HuÈckel in Ref. [19]
Scheme 2. Synthesis of compounds 1±4. Reagents and conditions: (i) Cu2O, pyridine; (ii) diazomethane, CH2Cl2±ether or dioxane±ether,
(iii)TsNClNa, KHCO3 aq, 1008C, 1 h; (iv) H2O2±AcOH, 1008C, 30 min.

P. Nagy et al. / Journal of Molecular Structure 606 (2002) 61±76
63
system); (iii) in analogous compounds, the S´´´O
were investigated earlier by Glass et al. [21±23].
interaction is weakened (i.e. the S´´´O distance
increased) by increasing the oxidation number (2, 4
or 6) of the sulfur atom.
The importance of S´´´O interaction in controlling
both the actual conformation and the reactivity of
organosulfur compounds prompted us to investigate
the naphthalene derivatives having S-aryl substituents
in 1,8-positions. However, in this case a repulsive
S´´´S interaction should also exist, from which stereo-
chemistry becomes more complicated. As it has been
shown by Glass et al. [21±23], the S´´´S nonbonded
distances in peri-substituted naphthalene derivatives
Ê
lie in the region of 2.93±3.63 A, and therefore, they
are shorter than the sum of the van der Waals radii
Ê
(3.70 A), but longer than the S±S covalent bond
Ê
Ê
(2.01 A) and the S´´´S distance (2.50±2.86 A) found
earlier in the case of attracting interaction [24,25].
Owing to the steric strain, the peri bond angles are
increased and the sulfur atoms in 1,8-positions
displace to the opposite sides of the least-squares
plane of the naphthalene ring. The measure of the
deviations was found to depend on the valence state
of the sulfur atom.
1.2. Synthesis (Scheme 2)
Bis-sul®de 1 was prepared from 1,8-diiodonaphtha-
lene (9) [26] and benzenethiol (10) in pyridine
containing copper(I) oxide. To obtain bis-sul®de 2,
1,8-diiodonaphthalene (9) was ®rst coupled with 2-
sulfanylbenzoic acid (11) then dicarboxylic acid 12
was converted with diazomethane into the corre-
sponding dimethyl ester (bis-sul®de 2). The oxidation
of 12 with chloramine-T resulted in sulfoxide-dicar-
boxylic acid 13 which was treated with diazomethane
to yield bis-sulfoxide 3. The synthesis of bis-sulfone 4
started from 13 which was oxidized ®rst with
hydrogen peroxide to sulfone-dicarboxylic acid 14,
then the latter was methylated with diazomethane to
yield 4.
1.1. Model compounds
In this paper, we report the X-ray structure deter-
minations of four 1,8-disubstituted naphthalene
derivatives, 1,8-bis(phenylsulfanyl)naphthalene (1),
1,8-bis[(2-methoxycarbonylphenyl)sulfanyl]naphtha-
lene (2), 1,8-bis[(2-methoxycarbonylphenyl)sul®nyl]-
naphthalene (3) and 1,8-bis[(2-methoxycarbonyl-
phenyl)sulfonyl]naphthalene (4). These compounds
have sulfur atoms of different valence states in the
peri positions giving rise to different S´´´S close
contacts. Compounds 2±4 carry methoxycarbonyl
groups in the ortho positions of the S-phenyl substi-
tuents, which may take part as donor groups in an
S´´´OyCr close contact of 1,5 type. In order to eluci-
date how the structure is governed by both S´´´S and
S´´´O nonbonded interactions and the rigidity of the
molecular skeleton, the structures of compounds 1±4
are analyzed and compared with those of 1,8-
bis(methylsulfanyl)naphthalene (5), and naphtho-
(1,8-bc)-1,5-dithiocin derivatives of bis-sul®de (6),
bis-sulfoxide (7) and bis-sulfone (8) type which
2. Experimental
2.1. Materials
È
Melting points (mp) were determined on a Boetius
micro melting point apparatus. Infrared (IR) spectra
were taken on a Specord IR 75 (Zeiss, Jena) spectro-
photometer. Microanalyses were carried out in the
microanalytical laboratory of the Department of

64
P. Nagy et al. / Journal of Molecular Structure 606 (2002) 61±76
u
u
s
s
s
s
u
uv
u
uv
u
uv
v
s
D
S
S
S
S
S
r
r
a
b
g
l
m
u
s

P. Nagy et al. / Journal of Molecular Structure 606 (2002) 61±76
65
Organic Chemistry by Dr H. Medzihradszky-
Schweiger and co-workers.
2.4. 1,8-Bis[2-(methoxycarbonyl)phenylsul®nyl]-
naphthalene (3)
Solvents were puri®ed and dried by the usual
methods. Evaporations were carried out under
reduced pressure. Products obtained were dried in
vacuo over P2O5 or KOH pellets, depending on the
solvent used.
Sul®de dicarboxylic acid 12 (2 g, 4 mmol) was
dissolved in a solution of 1 M KHCO3 (15 ml) by
heating, and chloramine-T (TsNClNa´3H2O, 2.54 g,
9 mmol) was added. After heating at 1008C (1 h),
the mixture was cooled to room temperature, the
precipitate (TsNH2) was ®ltered off, the ®ltrate
extracted with EtOAc ꢀ3 £ 10 ml† and then acidi®ed
with cc HCl (pH 1). The precipitate was ®ltered off,
washed with water and dried to give 1,8-bis(2-
carboxyphenylsul®nyl)naphthalene 13. Yield: 1.77 g
(94%); mp 202±2058C; IR (KBr): 3600±2200br (O±
H), 1686s (CyO), 1003vs (SyO) cm21. Elemental
analysis Ð found: C, 61.8; H, 3.3; O, 20.5; S, 13.8.
C24H16O6S2 requires: C, 62.05; H, 3.47; O, 20.67; S,
13.80%.
Compound 3 was prepared from 13 with diazo-
methane in dioxane. Mp 257±2608C; IR (KBr):
1713vs (CyO), 1022vs (SyO) cm21. Elemental
analysis Ð found: C, 63.1; H, 4.0; O, 19.2; S, 12.9.
C26H20O6S2 requires: C, 63.40; H, 4.09; O, 19.49; S,
13.02%. X-ray data reveal that crystalline bis-sulfoxide
3 (with a symmetric constitution and with two asym-
metric sulfur atom) is present in the racemic form (Fig.
3 shows the stereoscopic view of the R, R-enantiomer).
The relative stability of the racemic bis-sulfoxide 3
may be attributed to the favorable position of the
sul®nyl-oxygens (see Fig. 3 and Table 10).
2.2. 1,8-Bis(phenylsulfanyl)naphthalene (1)
A mixture of 1,8-diiodonaphthalene (9) (7.54 g,
20 mmol), benzenethiol (10) (4.41 g, 10 mmol) and
Cu2O (2.86 g, 20 mmol) in dry pyridine (60 ml) was
re¯uxed under N2 (2 h) and, after cooling to room
temperature, was poured into a mixture of ice
(100 g) and cc HCl (100 ml). The precipitate was
®ltered off, washed with water, dried and then
extracted with ether (100 ml). After evaporation, the
crude product was crystallized from MeOH; yield:
3.7 g (55%); mp 75±768. Elemental analysis Ð
found: C, 76.5; H, 4.5; S, 18.5. C22H16S2 requires: C,
76.70; H, 4.68; S, 18.62%.
2.3. 1,8-Bis[2-(methoxycarbonyl)phenylsulfanyl]-
naphthalene (2)
The solution of 1,8-diiodonaphthalene (9) (20 g,
53 mmol), 2-sulfanylbenzoic acid (11) (16.2 g,
106 mmol), Cu2O (7.6 g, 53 mmol) in dry pyridine
was re¯uxed under N2 for 2 h. After cooling to room
temperature, the mixture was poured into the mixture
of ice (300 g) and cc HCl (300 ml). The precipitate
was ®ltered off, washed with water and boiled in an
aqueous solution of NaOH (10 g, 250 mmol in 500 ml
of water) for 2 h and ®ltered. The ®ltrate was acidi®ed
with cc HCl (pH 1), the precipitate was ®ltered off,
washed with water, dried and recrystallized from
DMF±AcOH to afford pure 1,8-bis(2-carboxyphenyl-
sulfanyl)naphthalene (12). Yield: 13.2 g (51%); mp
324±3258C; IR (KBr): 3680±2200br (O±H), 1705vs
(CyO) cm21. Elemental analysis Ð found: C, 66.5;
H, 3.6; O, 14.5; S, 14.5. C24H16O4S2 requires: C,
66.65; H, 3.73; O, 14.80; S, 14.83%.
2.5. 1,8-Bis[2-(methoxycarbonyl)phenylsulfonyl]-
naphthalene (4)
Sulfoxide dicarboxylic acid 13 (0.99 g, 2 mmol)
was dissolved in AcOH and H2O2 (30%, 7 ml) was
added to the solution. The mixture was re¯uxed for
30 min, additional H2O2 (2 ml) was added and heating
was continued for 1 h. After cooling to room tempera-
ture, the crystals precipitated were ®ltered off and
dried to yield 1,8-bis(2-carboxyphenylsulfonyl)-
naphthalene (14, 0.86 g, 89%), IR (KBr): 3650±
2200br (O±H), 1700vs (CyO), 1315s (SO2) cm21
.
Compound 2 was prepared from 12 with diazo-
methane in dichloromethane. Mp 170±1728C; IR
(KBr): 1710vs (CyO) cm21. Elemental analysis Ð
found: C, 67.9; H, 4.4; O, 13.7; S, 13.7. C26H20O4S2
requires: C, 67.80; H, 4.38; O, 13.90; S, 13.92%.
Elemental analysis Ð found: C, 58.0; H, 3.3; O,
25.5; S, 12.7. C24H16O8S2 requires: C, 58.05; H,
3.25; O, 25.78; S, 12.92%.
Compound 4 was prepared from sulfone dicarboxylic
acid 14 with diazomethane in dichloromethane. Mp

66
P. Nagy et al. / Journal of Molecular Structure 606 (2002) 61±76
Fig. 1. Stereoscopic view of bis-sul®de 1 with numbering scheme for the nonhydrogen atoms.
297±3008C; IR (KBr): 1722vs (CyO), 1329vs (SO2)
cm21. Elemental analysis Ð found: C, 59.3; H, 3.7;
O, 24.2; S, 12.0. C26H20O8S2 requires: C, 59.53; H,
3.84; O, 24.40; S, 12.22%.
for 25 re¯ections. Standard re¯ections (three for
each data collection) indicated no decay of the crys-
tals. All re¯ections were corrected for Lorenz and
polarization effects. The crystallographic phase
problems were solved by a direct method using
program shelxs [27]. The atomic positions for each
structure were re®ned with anisotropic displacement
parameters in F2 mode using the program shelxl93
[28]. The hydrogen positions were generated from
assumed geometry and were re®ned isotropically in
riding mode. Since the molecules of 4 exhibit
molecular chirality in space group P212121; Flack
parameter [29] was re®ned on data collected with
CuKa radiation. Furthermore, the visible C2
symmetry of the molecules in 2 and 3 prompted us
to check the possibility of establishing space groups
2.6. Crystal structure determinations
Single crystals of X-ray quality were grown from a
hot solution of 1 in methanol, a hot solution of 2 in
DMF, while 3 and 4 were recrystallized from a 2:1
mixture of dioxane and water, and a mixture of DMF
and water, respectively. Table 1 summarizes the rele-
vant data concerning the crystal structure analyses.
Each data set was collected on a CAD-4 diffract-
ometer equipped with graphite monochromator.
Lattice parameters were re®ned by least squares ®t
Fig. 2. Stereoscopic view of bis-sul®de 2 with numbering scheme for the nonhydrogen atoms.

P. Nagy et al. / Journal of Molecular Structure 606 (2002) 61±76
67
Fig. 3. Stereoscopic view of bis-sul®de 3 with numbering scheme for the nonhydrogen atoms.
with crystallographic twofold axes. These efforts were
fruitless, however.
Crystal data (excluding structure factors) for the
structures in this paper have been deposited at the
Cambridge Crystallographic Data Centre and are
also available from the authors.
ents exhibit more or less distorted C2 molecular (not
crystallographic) symmetry, while that of 1 is free
from any molecular symmetry.
3.1. Orientation of aromatic rings
The mutual positions of the naphthalene and phenyl
rings in compounds 1±4 are presumably in a close
correlation with S´´´S and S´´´O close contacts formed
in an intramolecular manner. From a structural point
of view, compounds 1±4 may be regarded as
`Siamese twins' composed from two diaryl sul®de, -
sulfoxide or -sulfone parts which are fused through
one of their benzene rings. In these twin-molecules,
the orientation of S-naphthyl rings with regard to the
C(ar)±S(1)±C(ar) and C(ar)±S(2)±C(ar) planes can
3. Results and discussion
The stereoscopic views of compounds 1±4 are
shown in Figs. 1±4. Relevant geometric parameters
with estimated standard deviations in the last signi®-
cant digits are listed in Tables 2±5. The last digits of
the geometric data were omitted when discussed in the
text. The structures 2±4 with ortho-COOMe substitu-
Fig. 4. Stereoscopic view of bis-sulfone 4 with numbering scheme for the nonhydrogen atoms.

68
P. Nagy et al. / Journal of Molecular Structure 606 (2002) 61±76
Table 2
Relevant geometric parameters for bis-sul®de 1 with ESDs in parentheses
Ê
Interatomic distances (A)
S1´´´S2
C1±C9
C4±C10
S1±C1
3.005(1)
1.432(2)
1.412(3)
1.780(2)
1.773(2)
C9±C10
C8±C9
C5±C10
S2±C8
1.439(2)
1.436(2)
1.407(3)
1.782(2)
1.783(2)
S1±C11
S2±C17
Angles (deg)
C1±C9±C8
C9±C1±S1
C1±S1±C11
C1±S1´´´S2
C11±S1´´´S2
127.2(1)
C4±C10±C5
C9±C8±S2
C8±S2±C17
C8±S2´´´S1
C17±S2´´´S1
119.5(2)
124.0(1)
102.7(1)
82.0(1)
121.9(1)
102.5(1)
83.5(1)
105.1(1)
168.5(1)
Torsion angles (deg)
C10±C9±C1±S1
C9±C1±S1±C11
C1±S1±C11±C12
S1±C1´´´C8±S2
175.1(1)
±95.2(1)
26.1(2)
C10±C9±C8±S2
C9±C8±S2±C17
C8±S2±C17±C18
C11±S1´´´S2±C17
172.1(1)
2 160.0(1)
2 112.8(1)
2 146.2(3)
2 10.9(1)
be described by the torsion angles w1 ˆ
and
3.2. S´´´S interactions
Cꢀ9†±Cꢀ1†±Sꢀ1†±Cꢀ11†
w2 ˆ Cꢀ9†±Cꢀ8†±
Sꢀ2†±Cꢀ17†; while that of S-phenyl rings by the c1 ˆ
Cꢀ1† 2 Sꢀ1† 2 Cꢀ11† 2 Cꢀ12† and c2 ˆ Cꢀ8† 2
Sꢀ2† 2 Cꢀ17† 2 Cꢀ18† torsion angles, respectively
(Table 8). If w or c are about 908, the conformation
is axial, if they are about 1808, the conformation is
equatorial; the intermediate cases are designated as
twist (cf. Refs. [5,6]).
The four naphthalene derivatives 1±4 bear the two
sulfur atoms in the peri position, and therefore, they
are unavoidably nearer to each other (3.00, 3.18, 3.01
Ê
and 3.53 A, respectively) than the sum of their van der
Waals radii. The repulsive S´´´S interaction between
sulfur atoms should result in the stretching of C±C
bonds and C±C±C bond angles in the naphthalene
part, together with a twisting of the planar naphtha-
lene ring. Indeed, the bond lengths around C9 is
signi®cantly longer than those around C10 (average
The mutual axial±equatorial orientation of the
naphthyl and phenyl rings in both halves of bis-
sul®des 1 and 2 corresponds to the general trend
observed in case of diaryl sul®des [5]. However, the
`aircraft-like' shape of molecule 1 turns into a
`medusa-like' one in molecule 2 (cf. Figs. 1 and 2)
because in 2, both phenyl rings are equatorial, i.e.
coplanar with the C(ar)±S±C(ar) planes (and the
naphthalene ring is axial in both S1 and S2 parts of
the molecule). Similar to other diaryl sulfoxides, the
two halves of the bis-sulfoxide 3 do not assume an
ideal butter¯y (axial±axial) conformation (cf. Ref.
[6]) but a less crowded twist-axial conformation
appears in both parts of the molecule (Table 6).
Both phenyl rings here are axial, i.e. perpendicular
to the C(ar)±S±C(ar) planes. The twist-axial confor-
mations found for the two halves of bis-sulfone 4 are
nearer to a butter¯y (axial±axial) conformation than
those in bis-sulfoxide 3, i.e. the w and c torsion angles
in 4 are nearer to the ideal 908 than in 3 (Table 6).
Ê
1.43 and 1.41 A, respectively). The most affected C1±
C9±C8 bond angles open to a mean value of 1288,
whereas the analogous C4±C10±C5 bond angles
remain near to the ideal 1208. However, all these
deviations would promote the separation of the sulfur
Ê
atoms only from a distance of 2.44±2.58 A. An addi-
tional separation is provided by both the widening of
the S1±C1±C9 and S2±C8±C9 bond angles, and a
twisting of the naphthalene ring as shown by the
nonbonded torsion angles S1±C1´´´C8±S2 (Table
7). The distortion of the 1,8-disubstituted naphthalene
ring (cf. Refs. [21±23]) may also be described by the
displacement of the sulfur atoms above and below the
average plane of the naphthalene ring (DS1 and DS2
data in Table 7).
In bis-sul®des, the S(II)´´´S(II) nonbonded
distances are obviously controlled by the repulsion

P. Nagy et al. / Journal of Molecular Structure 606 (2002) 61±76
69
Table 3
Relevant geometric parameters for bis-sul®de 2 with ESDs in parentheses
Ê
Interatomic distances (A)
S1´´´S2
S1´´´O1
C1±C9
3.182(1)
2.723(2)
1.432(2)
1.424(3)
1.777(2)
1.767(2)
1.485(3)
1.189(3)
1.321(2)
3.900(2)
C9±C10
S2´´´O2
C8±C9
1.429(2)
2.727(1)
1.440(2)
1.407(3)
1.778(2)
1.766(2)
1.476(3)
1.193(2)
1.330(2)
C4±C10
S1±C1
C5±C10
S2±C8
S1±C11
C12±C23
C23±O1
C23±O3
O1´´´O2
S2±C17
C18±C24
C24±O2
C24±O4
Angles (deg)
C1±S1´´´O1
C1±C9±C8
C9±C1±S1
175.3(1)
C8±S2´´´O2
C4±C10±C5
C9±C8±S2
179.6(1)
127.5(1)
126.0(1)
102.8(1)
125.0(2)
112.7(2)
122.3(2)
80.3(1)
119.7(2)
126.0(1)
103.2(1)
125.5(2)
112.3(2)
122.2(2)
80.0(1)
C1±S1±C11
C12±C23±O1
C12±C23±O3
O1±C23±O3
C1±S1´´´S2
C11±S1´´´S2
C8±S2±C17
C18±C24±O2
C18±C24±O4
O2±C24±O4
C8±S2´´´S1
C17±S2´´´S1
78.5(1)
78.0(1)
Torsion angles (deg)
C10±C9±C1±S1
177.6(1)
79.5(2)
C10±C9±C8±S2
176.6(1)
79.2(2)
C9±C1±S1±C11
C9±C8±S2±C17
C1±S1±C11±C12
S1±C11±C12±C23
C11±C12±C23±O1
C12±C23±O1´´´S1
C23±O1´´´S1±C11
O1´´´S1±C11±C12
C11±C12±C23±O1
C11±C12±C23±O3
C12±C23±O3±C25
S1±C1´´´C8±S2
2 171.0(2)
2 1.6(3)
2 7.5(3)
8.6(3)
C8±S2±C17±C18
S2±C17±C18±C24
C17±C18±C24±O2
C18±C24±O2´´´S2
C24±O2´´´S2±C17
O2´´´S2±C17±C18
C17±C18±C24±O2
C17±C18±C24±O4
C18±C24±O4±C26
C11±S1´´´S2±C17
2 176.1(1)
2 2.1(2)
2 4.6(3)
5.9(2)
2 7.2(2)
4.2(2)
2 5.3(1)
3.6(1)
2 7.5(3)
173.2(2)
175.5(2)
2 4.8(1)
2 5.4(1)
2 4.6(3)
176.6(2)
176.9(2)
144.8(1)
O1´´´S1´´´S2´´´O2
between the p-type lone pairs of the sulfur atoms.
Repulsion is thought to be relatively high (cf. Ref.
[21]) when the axis of the sulfur p-orbitals are colli-
near and lie in the plane of the aromatic bonding
system. This is the situation if the two corresponding
torsion angles w1(C9±C1±S1±C11) and w2(C9±C8±
S2±C17) are near 908. The lone pair±lone pair
repulsion is less effective when the axis of the sulfur
p-orbitals are parallel and vertical to the plane of the
aromatic (naphthalene) ring. In this case, the w torsion
angles are approximately 1808. On the other hand, an
attractive part of the interaction may also operate if
there is a nearly linear X±S(II)´´´S(II) sequence in the
molecule, which may promote the delocalization of
the sulfur lone pair to the antibonding sp (S±X)
orbital (cf. Ref. [20]). In bis-sulfoxides and bis-
sulfones, the repulsion between nonbonded oxygen
atoms should also be taken into account. Geometric
parameters related to S(II)´´´S(II) nonbonded inter-
action are shown in Table 8.
Bis-sul®de 1 is an S,S-diphenyl analogue of the S,S-
dimethyl derivative 5 investigated earlier by Glass et
al. [21]. The methyl±phenyl change in S-substituents
does not cause any dramatic change in the molecular
geometry. Table 7 shows that the torsion and the
twisting of the naphthalene ring is similar in both
compounds. However, the S(II)´´´S(II) nonbonded
distance is somewhat longer in compound
1

70
P. Nagy et al. / Journal of Molecular Structure 606 (2002) 61±76
Table 4
Relevant geometric parameters for bis-sulfoxide 3 with ESDs in parentheses
Ê
Interatomic distances (A)
S1´´´S2
S1´´´O1
C1±C9
3.005(1)
2.769(3)
1.426(4)
1.419(5)
1.813(2)
1.815(3)
1.506(2)
1.487(4)
1.198(4)
1.327(4)
5.469(4)
C9±C10
S2´´´O2
C8±C9
1.437(3)
2.831(3)
1.434(4)
1.410(4)
1.814(3)
1.820(3)
1.483(3)
1.489(4)
1.198(4)
1.326(4)
4.553(3)
C4±C10
S1±C1
C5±C10
S2±C8
S1±C11
S1±O5
S2±C17
S2±O6
C12±C23
C23±O1
C23±O3
O1´´´O2
C18±C24
C24±O2
C24±O4
O5´´´O6
Angles (deg)
O5±S1´´´O1
C1±C9±C8
C9±C1±S1
177.9(1)
O6±S2´´´O2
C4±C10±C5
C9±C8±S2
177.0(1)
128.1(2)
122.4(2)
100.7(1)
105.4(1)
104.2(1)
123.4(3)
112.0(3)
124.6(3)
82.3(1)
119.7(3)
121.4(2)
98.7(1)
C1±S1±C11
C1±S1±O5
C11±S1±O5
C12±C23±O1
C12±C23±O3
O1±C23±O3
C1±S1´´´S2
C11±S1´´´S2
C8±S2±C17
C8±S2±O6
107.9(2)
104.4(1)
123.9(3)
112.5(3)
123.6(3)
82.9(1)
C17±S2±O6
C18±C24±O2
C18±C24±O4
O2±C24±O4
C8±S2´´´S1
C17±S2´´´S1
151.1(1)
150.6(1)
Torsion angles (deg)
C10±C9±C1±S1
C9±C1±S1±C11
C9±C1±S1±O5
2 174.5(2)
138.1(2)
2 113.8(2)
173.4(2)
2 77.6(3)
6.5(4)
C10±C9±C8±S2
C9±C8±S2±C17
C9±C8±S2±O6
2 167.0(2)
136.1(2)
2 115.6(2)
2 173.7(3)
2 62.5(3)
0.6(4)
O5±S1±C11±C12
C1±S1±C11±C12
S1±C11±C12±C23
C11±C12±C23±O1
C12±C23±O1´´´S1
C23±O1´´´S1±C11
O1´´´S1±C11±C12
C11±C12±C23±O3
C12±C23±O3±C25
S1±C1´´´C8±S2
O6±S2±C17±C18
C8±S2±C17±C18
S2±C17±C18±C24
C17±C18±C24±O2
C18±C24±O2´´´S2
C24±O2´´´S2´´´C17
O2´´´S2´´´C17±C18
C17±C18±C24±O4
C18±C24±O4±C26
C11±S1´´´S2±C17
O5±S1´´´S2±O6
2.6(5)
2 14.9(5)
14.8(3)
2 6.2(3)
7.2(2)
2 11.0(2)
4.9(2)
2 6.7(2)
2 177.3(3)
177.0(4)
2 15.8(1)
2 135.0(1)
165.5(3)
177.4(4)
2 179.5(3)
2 135.5(2)
O1´´´S1´´´S2´´´O2
Ê
Ê
(3.01 A) than in the methyl-analogue 5 (2.93 A),
which may be ascribed to a stronger lone pair±lone
pair repulsion in the former case. In bis-sul®de 1, only
one of the C9±C(ar)±S±C(ar) torsion angles is nearly
1808 (see w1 and w2 in Table 6), whereas in compound
5, both the torsion angles are 1808. The relatively
short S(II)´´´S(II) distances in bis-sul®de 5 may also
be correlated with two favorable quasi-linear C±
S(II)´´´S(II) moieties which provide an attractive
part for the S(II)´´´S(II) interaction. In bis-sul®de 1,
there is only one such sequence (see Table 8). Here, it
should be mentioned that the S(II)´´´S(II) distance
may become even shorter if the counter-atom is
Ê
changed (e.g. 2.86 A with an S±S´´´S sequence in
Ref. [25]).
In bis-sul®de 2, which is an o,o0-bis(methoxy-
carbonyl) derivative of compound 1, the bond angles
of the naphthalene ring are strongly distorted, while
the disposition of sulfur atoms above and below the
naphthalene ring is relatively small (Table 7). The
S(II)´´´S(II) nonbonded distance is remarkably longer
Ê
(3.18 A) than in the unsubstituted compound l. The

P. Nagy et al. / Journal of Molecular Structure 606 (2002) 61±76
71
Table 5
Relevant geometric parameters for bis-sulfone 4 with ESDs in parentheses
Ê
Interatomic distances (A)
S1´´´S2
S1´´´O3
S1´´´O6
C1±C9
3.531(1)
3.304(2)
3.022(2)
1.436(3)
1.413(3)
1.783(2)
1.788(2)
1.501(3)
1.333(3)
6.345(2)
2.847(2)
3.072(2)
C9±C10
S2´´´O4
S2´´´O5
C8±C9
1.433(3)
3.164(2)
2.890(2)
1.431(3)
1.414(3)
1.791(2)
1.791(2)
1.492(4)
1.334(3)
2.841(2)
4.627(3)
C4±C10
S1±C1
C5±C10
S2±C8
S1±C11
C12±C23
C23±O3
O3´´´O4
O5´´´O6
O6´´´O7
S2±C17
C18±C24
C24±O4
O5´´´O8
O7´´´O8
Angles (deg)
O7±S1´´´O3
C11±S1´´´O6
C1±C9±C8
C9±C1±S1
170.7(1)
O8±S2´´´O4
C17±S2´´´O5
C4±C10±C5
C9±C8±S2
171.7(1)
174.7(1)
129.0(2)
124.5(2)
105.3(1)
109.6(1)
109.2(1)
120.6(1)
105.6 (1)
105.5 (1)
124.4(2)
110.8(2)
124.7(2)
72.3(1)
178.6(1)
119.5(2)
125.2(2)
103.8(1)
109.4(1)
110.2(1)
120.5(1)
106.4 (1)
105.1 (1)
124.2(2)
111.1(2)
124.5(3)
71.3(1)
C1±S1±C11
C1±S1±O5
C1±S1±O7
O5±S1±O7
C11±S1±O5
C11±S1±O7
C12±C23±O1
C12±C23±O3
O1±C23±O3
C1±S1´´´S2
C11±S1´´´S2
C8±S2±C17
C8±S2±O6
C8±S2±O8
O6±S2±O8
C17±S2±O6
C17±S2±O8
C18±C24±O2
C18±C24±O4
O2±C24±O4
C8±S2´´´S1
C17±S2´´´S1
151.8(1)
157.9(1)
Torsion angles (deg)
C10±C9±C1±S1
C9±C1±S1±C11
C9±C1±S1±O5
2 156.7(2)
119.8(2)
6.7(2)
C10±C9±C8±S2
C9±C8±S2±C17
C9±C8±S2±O6
2 152.0(2)
125.2(2)
12.0(2)
C9±C1±S1±O7
2 127.4(2)
23.3(2)
C9±C8±S2±O8
2 122.6(2)
25.3(2)
O5±S1±C11±C12
O7±S1±C11±C12
C1±S1±C11±C12
S1±C11±C12±C23
C11±C12±C23±O1
C11±C12±C23±O3
O6±S2±C17±C18
O8±S2±C17±C18
C8±S2±C17±C18
S2±C17±C18±C24
C17±C18±C24±O2
C17±C18±C24±O4
151.9(2)
2 92.6(2)
12.3(3)
154.1(2)
2 90.1(2)
12.0(3)
2 123.1(3)
61.1(3)
2 132.8(3)
52.1(3)
Torsion angles (deg)
C12±C23±O3´´´S1
C23±O3´´´S1±C11
O3´´´S1±C11±C12
S1±C1±C9±C8
2 54.2(2)
54.0(2)
2 29.7(2)
24.1(3)
C18±C24±O4´´´S2
C24±O4´´´S2±C17
O4´´S2±C17±C18
C9±C8±S2±O6
2 49.9(2)
48.9(2)
C1±C9±C8±S2
27.2(3)
2 28.5(2)
12.0(2)
C9±C8±S2´´´O5
C8±S2´´´O5±S1
S2´´´O5±S1±C1
O5±S1±C1±C9
2 55.6(2)
71.9(1)
C8±S2±O6´´´S1
S2±O6´´´S1±C1
O6´´´S1±C1±C9
C18±C24±O4±C26
C11±S1´´´S2±C17
2 51.5(1)
76.5(1)
2 47.1(1)
6.7(2)
2 55.1(2)
2 176.4(2)
2 138.2(2)
C12±C23±O3±C25
S1±C1´´´C8±S2
O3´´´S1´´´S2´´´O4
O5±S1´´´S2±O6
O5±S1´´´S2±O8
2 179.7(2)
42.5(1)
2 110.3(1)
129.4(1)
7.4(1)
O7±S1´´´S2±O8
O7±S1´´´S2±O6
2 112.3(1)
9.7(1)

72
P. Nagy et al. / Journal of Molecular Structure 606 (2002) 61±76
Table 6
Geometric parameters indicating the separation of the Car±S peri bonds (the last digits with estimated standard deviations are omitted)
Compound
Torsion angle (L0)a
Conformationb
Torsion angle (L0)a
Conformationb
1
w1 (295)
c1 (26)
w1 (80)
N1: axial
P1: equatorial
N1: axial
w2 (2160)
c2 (2113)
w2 (79)
N2: equatorial
P2: axial
2
3
N2: axial
c1 (2171)
w1 (138)
c1 (278)
v1 (173)
w1 (120)
c1 (293)
v1 (23)
P1: equatorial
N1: twist
P1: axial
c2 (2176)
w2 (136)
c2 (263)
v2 (2174)
w2 (125)
c2 (290)
v2 (25)
P2: equatorial
N2: twist
P2: axial
c
c
±
±
4
N1: twist
P1: axial
N2: twist
P2: axial
d
d
±
±
v01 (152)
±
v02 (154)
±
d
d
a
w1 ˆ C9±C1±S1±C11; w2 ˆ C9±C8±S2±C17; c1 ˆ C1±S1±C11±C12; c2 ˆ C8±S2±C17±C18; v1 ˆ O5±S1±C11±C12; v2 ˆ
O6±S2±C17±C18; v01 ˆ O7±S1±C11±C12; v02 ˆ O8±S2±C17±C18:
b
N1: naphthalene ring S1 side; N2: naphthalene ring S2 side; P1: S1 phenyl ring; P2: S2-phenyl ring; axial: perpendicular to the C(ar)±S±C(ar)
plane; equatorial: coplanar with the C(ar)±S±C(ar) plane; twist: intermediate between axial and equatorial.
c
S ˆ O bond is coplanar with the phenyl ring.
d
S ˆ O bond is nearly coplanar with the phenyl ring.
observed value is near the transannular S(II)´´´S(II)
Ê
distance (3.23 A in Ref. [21]) found for the
S(II)´´´S(II) sequences as favorable structural factors
are not present in 2 (see Table 8). However, it may be
mentioned that in bis-sulfoxide 2, the geometry
appears well-suited for delocalization of the p-type
lone pair on sulfur through the phenyl ring into the
carbonyl p-system. This would decrease the electron-
density on sulfur lowering the repulsion between
collinear lone pair sulfur orbitals.
In bis-sulfoxide 3, which is the S,S0-dioxide of
compound 2, the disposition of the sulfur atoms
above and below the naphthalene ring is of a high
degree (Table 7). However, owing to favorable
naphtho±dithiocin derivative 6 of rigid structure, in
which the sul®de±sulfur atoms bound to naphthalene
ring in 1,8-positions are connected with a trimethyl-
ene bridge. The elongation of the S(II)´´´S(II) contact
may be explained in both cases by an increased lone
pair±lone pair interaction. In compound 2, the C(9)±
C(ar)±S±C(ar) torsion angles in both halves of the
molecule are near 908 (see w1 and w2 in Table 6),
meaning that the axis of the sulfur p-orbitals are
unfavorably collinear. In addition, quasi-linear C±
Table 7
Geometric parameters related to S´´´S nonbonded interactions in compounds 1±4 (the last digits with estimated standard deviations are omitted)
Ê
DS1 (A)
Ê
DS2 (A)
Compound
S1±C1±C9 (deg)
S2±C8±C9 (deg)
S1±C1´´´C8±S2 (deg)
1
124
(122)a
126
122
(121)a
126
2 11
(213)
2 5
0.19
(20,29)a
0.02
2 0.27
(0.31)a
2 0,05
(20.07)b
2 0.46
(0.20)c
2 0.91
(1.02)d
2
3
4
(127)b
(126)b
(29)
2 16
(2)c
(0.34)b
122
121
0.28
(0.08)c
0.79
(21.02)d
(124)c
125
(125)c
125
43
(255)d
(123)d
(123)d
a
Taken from Ref. [21] for 5.
Taken from Ref. [21] for 6.
b
c
d
Taken from Ref. [23] for 7.
Taken from Ref. [23] for 8.

P. Nagy et al. / Journal of Molecular Structure 606 (2002) 61±76
73
Table 8
exist, which causes the characteristic shortening of the
S´´´S nonbonded distance in compounds of the sulf-
oxide type.
Torsion angles determining the aromatic ring positions in
compounds 1±4 (the last digits with estimated standard deviations
are omitted)
In bis-sulfone 4, which is the S,S0-tetroxide of
compound 2, the torsion and the twisting of naphtha-
lene ring as well as the disposition of sulfur atoms
above and below the naphthalene ring are of
maximum degree (Table 8), which may be attributed
to a steric crowd around the sulfur atoms. At the same
time, the nonbonded S(VI)´´´S(VI) distance in bis-
C±S1´´´S2 (deg)a
Ê
S1´´´S2 (A)
Compound
1
u1 (105)
u2 (169)
u1 (79)
3.01
(2.93)b
2
3
4
3.18
(3.23)c
3.01
(3.05)d
3.53
(3.63)e
u2 (78)
u1 (151)
u1 (151)
u1 (152)
u2 (158)
Ê
sulfone 4 is extremely long (3.53 A), as compared to
those in 1±3. However, the transannular
S(VI)´´´S(VI) distance in the heterocyclic bis-sulfone
a
¼
¼
u1 ˆ C11±S1 S2; u2 ˆ C17±S2 S1:
Taken from Ref. [21] for 5.
Taken from Ref. [21] for 6.
Taken from Ref. [23] for 7.
Taken from Ref. [23] for 8.
Ê
8 is even longer (3.65 A in Ref. [23]) although the SO2
b
c
d
e
groups disrotate and the oxygen atoms are placed
rather far from each other. Thus, it may be assumed
that bis-sulfone 4, in which the SO2 groups face each
other, is somewhat stabilized by intramolecular
nonbonded interactions (see Section 3.3). Other data
in the literature also indicate that S´´´S nonbonded
contacts involving an SO2 group are rather loose. In
models derived from compound 6 [23], the transan-
structural factors, the S(IV)´´´S(IV) distance is
Ê
surprisingly short (3.01 A). The C9±C1±S1±O5,
C9±C8±S2±O6 and O5±S1´´´S2±O6 torsion angles
of 2114, 2116 and 21368, respectively, suggest only
a moderate repulsion between the sul®nyl-oxygens
(and in the same way between the sulfur lone pairs).
In addition, two quasi-linear C±S(IV)´´´S(IV)
sequences assisting the formation of the
S(IV)´´´S(IV) close contact also occur in bis-sulfoxide
3 (see Table 8).
Ê
nular S´´´S distances of 3.27 and 3.40 A were found
for a sul®de±sulfone and a sulfoxide±sulfone, respec-
tively.
3.3. S´´´O interactions
It is remarkable that the transannular S´´´S
distances are similarly short in bis-sulfoxide 7
As expected, in both halves of the bis-sul®de 2,
Ê
S(II)´´´O close contacts (2.72 and 2.73 A) are formed
Ê
(3.05 A in Ref. [23]) and in two heterocyclic
sul®de±sulfoxides both having a rigid eight- or
Ê
seven-membered ring (3.01 and 3.06 A in Refs.
[22,30], respectively). Owing to a nearly linear
(165±1748) O ˆ S´´´S sequence found in all of these
models, an attractive part for S´´´S interaction should
between the sul®de±sulfur atoms and the carbonyl-
oxygens of the ortho-methoxycarbonyl substituents
on the equatorial phenyl rings (Table 9). The confor-
mational analysis of bis(2-methoxycarbonylphenyl)
sul®de [5] showed that a much closer S´´´O contact
is formed in the equatorial S-phenyl ring than in the
Table 9
Geometric parameters related to S´´´O nonbonded interactions in compounds 2±4 (the last digits with estimated standard deviations are omitted)
C±S´´´O (deg)a
OyS´´´O (deg)b
Ê
S´´´O (A)
Ê
S´´´O (A)
Compound
2
u1 (175)
u2 (180)
2.72
2.73
3
4
h1 (178)
h2 (177)
h3 (171)
h4 (172)
2.77
2.83
3.30
3.16
u3 (175)
u4 (179)
3.02
2.89
a
¼
¼
¼
¼
u1 ˆ C1±S1 O1; u2 ˆ C8±S2 O2; u3 ˆ C11±S1 O6; u4 ˆ C17±S2 O5:
b
¼
¼
¼
¼
h1 ˆ O5±S1 O1; h2 ˆ O6±S2 O2; h3 ˆ O7±S1 O3; h1 ˆ O8±S2 O4:

74
P. Nagy et al. / Journal of Molecular Structure 606 (2002) 61±76
Table 10
Nonbonded O´´´O distances in compounds 2±4 (the last digits with estimated standard deviations are omitted)
O´´´S´´´S´´´O (deg)a
OyS´´´SyO (deg)b
Ê
O´´´O (A)
Ê
O´´´O (A)
Compound
2
3
4
j1 (25)
j1 (2135)
j2 (2110)
O1´´´O2 (3.90)
O1´´´O2 (5.47)
O3´´´O4 (6.35)
x1 (2136)
x1 (129)
x2 (7)
O5´´´O6 (4.55)
O5´´´O6 (2.85)
O5´´´O8 (2.84)
O6´´´O7 (3.07)
O7´´´O8 (4.63)
x3 (10)
x4 (2112)
a
¼
¼
¼
¼
¼
¼
j1 ˆ O1 S1 S2 O2; j2 ˆ O3 S1 S2 O4:
b
¼
¼
¼
¼
x1 ˆ O5±S1 S2±O6; x2 ˆ O5±S1 S2±O8; x3 ˆ O7±S1 S2±O6; x4 ˆ O7±S1 S2±O8:
Ê
axial one (2.72 and 3.08 A). On this basis, we may
explain why both methoxycarbonyl-substituted
phenyl rings in 2 occupy equatorial positions,
although the conformation is unfavorable for the
S´´´S interaction.
S-phenyl rings of bis-sulfoxide 3 (7, 38 and 1, 2158 in
the S1- and S2-moieties, respectively) here also indi-
cate the favorable formation of planar ®ve-membered
rings closed by S(IV)´´´O close contact. In contrast
with the case in 2, the nonbonded O´´´S´´´S´´´O
moiety in 3 is not synperiplanar but anticlinal, thus
the carbonyl-oxygens lie even farther from each other
(Table 10). The nearly axial positions of S-phenyl
rings in both halves of the molecule allow the conju-
gation with the S(IV)yO bonds (see torsion angles v
in Table 8). At the same time, the sul®nyl-oxygens
assume an anticlinal position in the O5±S1´´´S2±O6
moiety (see O5´´´O6 distance in Table 10) and as
mentioned earlier they do not in¯uence the S´´´S inter-
action.
The twist-axial conformations of the two halves of
bis-sulfone 4 with axial S-phenyl groups are near to
those of bis-sulfoxide 3. This type of conformation
promotes the conjugation between the sulfonyl and
phenyl groups, as SyO bonds are nearly coplanar
with the phenyl rings (see the torsion angles v in
Table 6; both sulfonyl-oxygens emerge only by
about 258 over the phenyl plane).
As shown in Fig. 4, there is a steric crowd in the
structure of 4, which contains eight oxygen atoms not
too far from each other. Consequently, the ortho-
methoxycarbonyl groups no more remain coplanar
with the S-phenyl ring. The torsion angles found for
the four-atom parts of the S±C(ar)±C(ar)±C(sp2)±
O(carbonyl) sequences (12, 21238 and 12, 21338 in
the S1- and S2-moieties, respectively) point to a
drastic turning out of the ortho-substituents from the
common plane. Thus, carbonyl-oxygens get too far
from sulfur(VI) atoms to form effective close
contacts. On the other hand, methoxy-oxygens come
The C(ar) counter-atoms in 2 which are joined
linearly to the S(II)´´´O moieties assist the formation
of effective S(II)´´´O close contacts. The torsional
angles for the S±C(ar)±C(ar)±C(sp2)±O(carbonyl)
sequences in the S-phenyl rings (22, 288 and 22,
258 for the S1- and S2-moieties, respectively) point
to favorable planar ®ve-membered `rings' closed by
S(II)´´´O close contacts. Although the nonbonded
O´´´S´´´S´´´O moiety is practically synperiplanar,
the carbonyl-oxygens lie far from each other (Table
10).
As it is known from the conformational analysis of
bis(2-methoxycarbonylphenyl) sulfoxide [6], a much
closer S(IV)´´´O contact is formed in the axial S-
phenyl ring than in the twisted one (2.73 and
Ê
3.04 A). In this case, a favorable linear OyS(IV)´´´O
sequence is formed in the axial aryl ring, and the
coplanarity of the SyO bond and the S-phenyl ring
allows a conjugative interaction between them. These
facts explain why the methoxycarbonyl-substituted S-
phenyl rings in the two halves of bis-sufoxide 3
assume the axial conformations (leaving the twist
positions for the naphthalene ring). The S(IV)´´´O
Ê
nonbonded distances in 3 (2.77 and 2.83 A) meet
with the expectations (Table 9). Owing to the different
positions of the S-phenyl rings, the `aircraft-like'
molecular shape of 3 differs signi®cantly from the
`medusa-like' 2.
The torsional angles for the four-atom parts of the
S±C(ar)±C(ar)±C(sp2)±O(carbonyl) sequences in the

P. Nagy et al. / Journal of Molecular Structure 606 (2002) 61±76
75
somewhat near the sulfur atoms and two weak
S(VI)´´´O(methoxy) nonbonded contacts of 3.16 and
Ê
3.30 A are formed both as a part of a linear
OyS(VI)´´´O(methoxy) sequence (Table 9).
However, it is striking to note that the sulfone
groups in 4 do not disrotate as in the heterocyclic
bis-sulfone 8. This phenomenon may be explained
by the formation of two additional S(VI)´´´O(sul-
fonyl) close contacts which join the two halves of
the molecule and are assisted by linear C(ar)±
S(VI)´´´O(sulfonyl) bridges (Table 9). Here, the
3.4. Intermolecular distances
The intermolecular distances observed for
compounds 1±4 are signi®cantly longer than the
sum of the van der Waals radii showing that there
no longer exists any intermolecular S´´´S and S´´´O
close contacts, which might control the actual mole-
cular conformations. The minimum intermolecular
Ê
S´´´S distances for 1±4: .6, .6, .6 and 5.397 A,
respectively; while the minimum intermolecular
S´´´O distances for 2±4: 4.774(1), 4.853(4) and
Ê
4.342(2) A, respectively. The aromatic rings in two
Ê
nonbonded distances are 2.89 and 3.02 A. It should
neighboring molecules are also too far from each
other to contribute to the geometries observed.
be noted that S(VI)´´´O close contacts of 1,5 type were
registered only in few cases in the literature (2.91±
Ê
3.22 A, cf. Refs. [1,6±8]). The nonbonded distances
observed earlier were not far from the sum of the van
Ê
der Waals radii (3.25 A), and thus they proved to be
Acknowledgements
signi®cantly longer than the S(II)´´´O and S(IV)´´´O
distances.
Â
The X-ray data were collected by Mr Csaba Kertesz
who deserves the thanks from the authors. The work
was supported by the Hungarian Research Foundation
OTKA T029799, OTKA 033086 and OTKA
T034985.
The S(VI)´´´O(methoxy) contacts close in both
parts of the molecule a ®ve-membered ring. Owing
to the turning out of the methoxycarbonyl groups from
the plane of the phenyl groups, these rings are far from
being favorably planar (cf. Ref. [1]). The torsion
angles for the four-atom sections in the S±C(ar)±
C(ar)±C(sp2)±O(methoxy) sequences are 12/12, 61/
52, 254/250, 54/49, 230/2298, starting from the
S1/ S2 atoms. The ®ve-membered rings with O(3)
and O(4) atoms assume a twisted envelope form char-
acterized by the puckering parameters [31] Q3 ˆ
References
[1] S. Bezzi, M. Mammi, C. Garbuglio, Nature (London) 82
(1958) 247.
Â
[2] A. Kucsman, I. Kapovits, in: F. Bernardi, I.G. Csizmadia, A.
Mangini (Eds.), Organic Sulfur Chemistry: Theoretical and
Experimental Advances, Elsevier, Amsterdam, 1985, p. 181.
     Â
[3] S. Solyom, P. Sohar, L. Toldy, A. Kalman, L. Parkanyi, Tetra-
ꢀ
ꢀ
0:786ꢀ3† A; F3 ˆ 332:2ꢀ2†8 and Q4 ˆ 0:712ꢀ3† A;
F4 ˆ 332:7ꢀ2†8; respectively.
hedron Lett. (1977) 4245.
 Â
On the contrary, the S(VI)´´´O(sulfonyl) close
contacts lead to the formation of a distorted six-
membered ring, giving the ®rst analyzed example of
an S(VI)´´´O contact of 1,6 type. The four-atom
sections of the rings with an S±C(ar)±C(ar)±C(ar)±
S0 ±O0 sequence may be characterized by the torsional
angles 24/27, 27/24, 12/7, 252/247, 77/72 and 255/
2568, starting from the S1/S2 atoms. The puckering
parameters for the stretched rings with O(5) and O(6)
 Â
[4] A. Kalman, L. Parkanyi, Acta Crystallogr. B36 (1980) 2372.
Â
[5] A. Kucsman, I. Kapovits, L. Parkanyi, Gy. Argay, A. Kalman,
Â
Â
Â
Â
J. Mol. Struct. 125 (1984) 331.
Â
[6] A. Kucsman, I. Kapovits, I. Kovesdi, L. Parkanyi, A. Kalman,
Â
Â
Â
Â
È
J. Mol. Struct. 127 (1985) 135.
Â
   Â
[7] A. Kalman, L. Parkanyi, D. Szabo, J. Mol. Struct. 317 (1994)
279.
Â
[8] D. Szabo, Sz. Szendeffy, I. Kapovits, A. Kucsman, Gy. Argay,
Â
   Â
A. Kalman, L. Parkanyi, Tetrahedron: Asymmetry 8 (1997)
2403.
Â
[9] A. Kucsman, I. Kapovits, M. Czugler, L. Parkanyi, A. Kalman,
Â
Â
Â
Â
ꢀ
atoms are Q5 ˆ 0:831ꢀ3† A; u5 ˆ 58:8ꢀ1† F5 ˆ
J. Mol. Struct. 198 (1989) 339.
 Â
[10] J. Rabai, I. Kapovits, I. Jalsovszky, Gy. Argay, A. Kalman,
ꢀ
339:5ꢀ2†8 and Q6 ˆ 0:898:3ꢀ3† A; u6 ˆ 58:5ꢀ1† F6 ˆ
Â
Â
T. Koritsanszky, J. Mol. Struct. 382 (1996) 13.
 Â
[11] D. Szabo, I. Kapovits, Gy. Argay, M. Czugler, A. Kalman,
335:8ꢀ2†8; respectively. Both parameter sets indicate a
transitional state between the half-chair and screw-
boat forms. The relative positions of oxygen atoms
and O´´´O nonbonded distances in bis-sulfone 4 are
shown in Table 10.
Â
Â
T. Koritsanszky, J. Chem. Soc. Perkin Trans. 2 (1997) 1045.
Â
[12] D. Szabo, I. Kapovits, J. Rabai, A. Kucsman, P. Huszthy, Gy.
Â
 Â
Argay, M. Czugler, M. FuÈlop, A. Kalman, T. Koritsanszky, L.
Â
Â
È
 Â
Parkanyi, J. Mol. Struct. 300 (1993) 23.

76
P. Nagy et al. / Journal of Molecular Structure 606 (2002) 61±76
Â
[13] D. Szabo, I. Kapovits, A. Kucsman, P. Nagy, Gy. Argay, A.
Â
[22] R.S. Glass, J.B. Broeker, H. Firouzabadi, J. Org. Chem. 55
(1990) 5739.
 Â
Kalman, J. Mol. Struct. 476 (1999) 157.
Â
[14] D. Szabo, M. Kuti, I. Kapovits, J. Rabai, A. Kucsman, Gy.
Â
Â
[23] R.S. Glass, J.B. Broeker, Tetrahedron 47 (1991) 5077.
[24] A. Hordvik, E. Sletten, J. Sletten, Acta Chem. Scand. 23
(1969) 1377.
   Â
Argay, M. Czugler, A. Kalman, L. Parkanyi, J. Mol. Struct.
415 (1997) 1.
[15] I. Kapovits, F. Ruff, J. Gulyas, A. Kucsman, Tetrahedron 32
Â
Â
[25] E. Sletten, M. Velsvik, Acta Chem. Scand. 27 (1973) 3881.
[26] H. Fujihara, M. Yabe, J. Chiu, N. Furukawa, Tetrahedron Lett.
32 (1991) 4345.
(1976) 1811.
Â
[16] F. Ruff, I. Kapovits, J. Rabai, A. Kucsman, Tetrahedron 35
Â
(1979) 1869.
[27] G.M. Sheldrick, shelxs86, Acta Crystallogr. B46 (1990) 467.
[28] G.M. Sheldrick, shelxl93 Program for the Re®nement of
Â
[17] F. Ruff, A. Kucsman, J. Chem. Soc. PerkinTrans. 2 (1988) 1123.
 Â
[18] P. Nagy, A. Csampai, D. Szabo, J. Varga, V. Harmat, F. Ruff,
È
Crystal Structures, University of Gottingen, 1994.
Â
A. Kucsman, J. Chem. Soc. Perkin Trans. 2 (2001) 339.
 Â
[19] C. Cohen-Addad, M.S. Lehmann, P. Becker, L. Parkanyi,
[29] H.D. Flack, Acta Crystallogr. A39 (1983) 876.
[30] M.J. Musmar, S.R. Khan, A.S. Zektzer, G.E. Martin, V.M.
Lynch, S.H. Simonsen, K. Smith, J. Heterocycl. Chem. 26
(1989) 667.
Â
Â
A. Kalman, J. Chem. Soc. Perkin Trans. 2 (1984) 191.
Â
Â
Â
[20] J.G. Angyan, R.A. Poirier, A. Kucsman, I.G. Csizmadia,
J. Am. Chem. Soc. 109 (1987) 2237.
[31] D. Cremer, J.A. Pople, J. Am. Chem. Soc. 97 (1975) 1354.
[21] R.S. Glass, S.W. Andruski, J.B. Broeker, H. Firouzabadi, L.K.
Steffen, G.S. Wilson, J. Am. Chem. Soc. 111 (1989) 4036.