Crystal Structures and an Initio Calculations of New Dicationic Telluranes (λ4-Tellane), 2+ (X = S, Se): Positively Charged Hypervalent Bonding Systems

Article abstract of DOI:10.1021/ja972930x

The reactions of 2,6-bis<(phenylthio- or phenylseleno)methyl>phenyl phenyl telluride or the corresponding Te-oxide, with NOBF4 or trifluoromethanesulfonic anhydride afforded the new telluranes, <10-Te-4(C2X2)>²⁺*2Y^- (λ⁴-te

Full text of DOI:10.1021/ja972930x

1230
J. Am. Chem. Soc. 1998, 120, 1230-1236
Crystal Structures and ab Initio Calculations of New Dicationic
Telluranes (λ4-Tellane), [10-Te-4(C2X2)]2+ (X ) S, Se): Positively
Charged Hypervalent Bonding Systems
Akio Bent Bergholdt,†,‡ Katsutoshi Kobayashi,‡ Ernst Horn,‡ Ohgi Takahashi,‡
Soichi Sato,‡ Naomichi Furukawa,*,‡ Masataka Yokoyama,§ and Kentaro Yamaguchi§
Contribution from the Tsukuba AdVanced Research Alliance Center, Department of Chemistry,
UniVersity of Tsukuba, Tsukuba, Ibaraki 305, Japan, and Department of Chemistry,
Chemical Analysis Center, Faculty of Science, Chiba UniVersity, Chiba 263, Japan
ReceiVed August 19, 1997
Abstract: The reactions of 2,6-bis[(phenylthio- or phenylseleno)methyl]phenyl phenyl telluride or the
corresponding Te-oxide, with NOBF4 or trifluoromethanesulfonic anhydride afforded the new telluranes, [10-
Te-4(C2X2)]2+‚2Y- (λ4-tellane) (X ) S or Se, Y ) BF4 or CF3SO3). These compounds were characterized
by elemental and spectroscopic (FABMS, 1H, 13C, and 125Te NMR) analyses. X-ray structure determinations
revealed that the hypervalent tellurium atoms are at the center of a distorted trigonal bipyramid, with two
apical sulfonio or selenonio ligands connected via transannular bonds. The Te-S distances are in the range
2.652-2.706 Å, the Te-Se distances in the range 2.759-2.807 Å, and the X-Te-X bond angles in the range
160.41-163.92 °. Ab initio calculations indicate that the positive charges in the dications are exclusively on
the three chalcogen atoms that form three-center, four-electron bonds.
Introduction
Recently, considerable interest has focused on the study of
organic compounds with hypervalent chalcogens, and as a result
a number of neutral chalcogenuranes were reported.1,2 However,
to date only a few examples of positively charged hypervalent
chalcogenuranes are known.3 The majority of these compounds
involve a three-center transannular interaction in a cyclic or
acyclic framework as exemplified by types A and B as shown
in Figure 1. However, no dicationic σ-telluranes were synthe-
sized and isolated. We report the preparation of a new type of
dicationic σ-telluranes (λ4-tellane), [10-Te-4(C2X2)]2+‚2Y-
(X ) S or Se, Y ) BF4 or CF3SO3) (4a, 4b, and 6) from the
new flexible acyclic tris-chalcogenide, 2,6-bis[(phenylthio)-
methyl]phenyl phenyl telluride (2a) and 2,6-bis[(phenylseleno)-
methyl]phenyl phenyl telluride (5), and the corresponding
Figure 1.
telluroxide (3) via transannular bond formation. Single-crystal
X-ray structure determinations revealed that two apical sulfonio-
or selenonio ligands bond to the central tellurium atom. Also
included in this article are the results of ab initio calculations
for the tellurane dications 4b and 6, which reveal the charge
distribution and electronic structure of the molecules.
† Current address: Novo Nordisk A/S, Novo Nordisk Park, 2760
Maaloev, Denmark.
Experimental Section
‡ University of Tsukuba.
General Procedure. All NMR spectra were obtained with a JEOL
LMN-EX-270 or a Bruker ARX-400 spectrometer. Each chemical shift
was determined by two-dimensional shift correlation (1H-1H- and 13C-
1H-COSY) spectra. Mass spectra were taken with a Shimazu QP-
2000 and a JEOL JMX SX102 mass spectrometer and IR spectra with
a JASCO FT/IR-300F spectrometer. For cyclic voltammetry measure-
ments, a Cypress Systems Inc. CS-1090 computer-controlled elec-
troanalytical system was used. The X-ray crystallographic analyses
were performed on an Enraf-Nonius CAD4 diffractometer, a Rigaku
AFC7S diffractometer, and a Rigaku RAXIS II imaging plate area
detector. All solvents and reagents were dried and purified according
to standard methods. Elemental analyses were carried out by the
Chemical Analytical Center at the University of Tsukuba. All melting
points are uncorrected.
§ Chiba University.
(1) Hayes, R. A.; Martin, J. C. Sulfurane Chemistry. In Organic Sulfur
Chemistry: Theoretical and Experimental AdVances; Bernardi, F., Csizma-
dia, I. G., Mangini, A., Eds.; Elsevier: Amsterdam, 1985; pp 408-483
(see also references therein).
(2) (a) Bergman, J.; Engman, L.; Siden, J. Tetra- and higher-valent
(hypervalent) derivatives of selenium and tellurium. In The chemistry of
organic selenium and tellurium compounds; Patai, S., Rappoport, Z., Eds.;
John Wiley and Sons: Inc.: New York, 1986; Vol. 1, pp 517-558 (see
also references therein). (b) Irgolic, K. J. Tetraorganyl Tellurium Com-
pounds, R4Te. In The Organic Chemistry of Tellurium; Gordon and Breach,
Inc.: New York, 1974; pp 234-241 (see also references therein).
(3) (a) Fujihara, H.; Chiu, J.-J.; Furukawa, N. J. Chem. Soc., Chem.
Commun. 1986, 1359. (b) Fujihara, H.; Chiu, J.-J.; Furukawa, N. J. Am.
Chem. Soc. 1988, 110, 1280. (c) Fujihara, H.; Mima, H.; Erata, T.;
Furukawa, N. J. Am. Chem. Soc. 1992, 114, 3117. (d) Fujihara, H.; Higuchi,
Y.; Mima, H.; Furukawa, N. Chem. Lett. 1994, 619. (e) Fujihara, H.;
Nakahodo, T.; Furukawa, N. J. Chem. Soc., Chem. Commun. 1996, 311-
312. (f) Fujihara, H.; Mima, H.; Furukawa, N. J. Am. Chem. Soc. 1995,
117, 10153-10154.
2,6-Bis[(phenylthio)methyl]-1-bromobenzene (1a). NaOH (0.39
g, 9.63 mmol) was added to a solution of thiophenol (1.06 g, 9.63
mmol) in ethanol (50 mL). The solution was added dropwise to a
S0002-7863(97)02930-2 CCC: $15.00 © 1998 American Chemical Society
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Telluranes (λ4-Tellane), [10-Te-4(C2X2)]2+ (X ) S, Se)
J. Am. Chem. Soc., Vol. 120, No. 6, 1998 1231
solution of 2,6-bis(bromomethyl)-1-bromobenzene4 (1.50 g, 4.38 mmol)
in CH2Cl2 (10 mL) at 0 °C. The solution was stirred overnight. After
the removal of solvents, the residue was extracted with CH2Cl2, and
the organic layer was dried over anhydrous MgSO4. After the removal
of solvent under vacuum at room temperature, the crude product was
subjected to column chromatography (silica gel; eluent, n-hexane-
CHCl3, 4:1) to give a colorless oil of 2,6-bis[(phenylthio)methyl]-1-
bromobenzene 1a (1.54 g) in 88% yield. 1H NMR (270 MHz, CDCl3,
room temperature) δ 4.25 (s, 4H, CH2), 7.06-7.33 (m, 13H, ArH).
13C NMR (68 MHz, CDCl3, room temperature) δ 40.5, 126.7, 126.7,
126.9, 128.9, 129.6, 130.7, 135.7, 137.8; MS (m/z) 402 (M+). Anal.
Calcd for C20H17BrS2: C, 59.85; H, 4.27. Found: C, 59.93; H, 4.32.
130.1, 130.5, 132.0, 135.5, 137.9, 138.8, 143.3; 125Te NMR (85 MHz,
CDCl3) δ 1203.1 (relative to Me2Te); FABMS (m/z) 545 (M+ + 3),
542 (M+); IR (KBr) 731 cm-1 (Te-O). Anal. Calcd for C26H22OS2-
Te: C, 57.60; H, 4.09. Found: C, 57.60; H, 4.20.
2,6-Bis[(phenylthio)methyl]phenyl Phenyl Telluranyl Bis(tet-
rafluoroborate) (4a). An anhydrous CH2Cl2 (10 mL) solution of
NOBF4 (49 mg, 0.42 mmol) was added dropwise to an anhydrous CH2-
Cl2 (20 mL) solution of telluride 2a (100 mg, 0.19 mmol) at -78 °C
under an argon atmosphere. The resulting solution turned yellow. When
the addition was completed, the NO gas was removed under vacuum.
After stirring overnight, the solvents were evaporated, and a yellow
-
solid, tellurane dication 2BF4 salt 4a (122 mg) in 92% yield was
obtained. Crystals for X-ray crystallographic analysis were grown from
a CD3CN solution. Mp 157-196 °C (dec); 1H NMR (270 MHz, CD3-
CN) δ 4.45, 5.15 (ABq, 1H, J ) 17.1 Hz, CH2), 4.95, 5.21 (ABq, 1H,
J ) 17.3 Hz, CH2), 6.83-7.18 (m, 9H, ArH), 7.47 (m, 6H, ArH), 7.99-
8.14 (m, 3H, ArH); 13C NMR (67.8 MHz, CD3CN) δ 39.6, 40.3, 121.9,
124.3, 125.0, 128.7, 130.2, 131.0, 131.6, 132.1, 132.5, 132.9, 133.1,
134.9, 135.3, 136.3, 147.6, 148.0; 125Te NMR (85.2 MHz, CD3CN) δ
1327.3 (relative to Me2Te); 19F NMR (254 MHz, CD3CN) δ -150.7
(relative to CFCl3); FABMS (m/z) 526 (M+ - 2BF4-). Anal. Calcd
for C26H22B2F8S2Te: C, 44.62; H, 3.17. Found: C, 44.08; H, 3.38.
2,6-Bis[(phenylthio)methyl]phenyl Phenyl Telluranyl Bis(tri-
fluoromethanesulfonate) (4b). (CF3SO3)2O (30 µL, 0.179 mmol) was
added to a heterogeneous mixture of the telluroxide (3) (88 mg, 0.16
mmol) in dry CH3CN (10 mL) at room temperature under an argon
atmosphere. The mixture immediately turned clear yellow. After
stirring for 1 h the solvent was evaporated at room temperature, and
the red-brown oily residue that remained was crystallized from Et2O/
CH3CN (1:1) to give yellow crystals, tellurane dication 2CF3SO3- salt
4b (43 mg) in 32% yield. Crystals for X-ray crystallographic analysis
were grown from a CD3CN solution. Mp 200-205 °C (dec); 1H NMR
(270 MHz, CD3CN) δ 4.45, 5.13 (ABq, 1H, J ) 17.7 Hz, CH2), 5.09,
5.24 (ABq, 1H, J ) 17.0 Hz, CH2), 6.87-7.50 (m, 15 H, ArH), 7.95-
8.17 (m, 3H, ArH); 13C NMR (67.8 MHz, CD3CN) δ 39.7, 40.7, 122.3,
122.6, 124.6, 125.3, 128.8, 130.5, 131.0, 131.6, 132.0, 132.1, 132.5,
132.8, 133.0, 135.0, 135.2, 136.2, 147.7, 148.2; 125Te NMR (85.2 MHz,
CD3CN) δ 1330.7 (relative to Me2Te); 19F NMR (254.0 MHz, CD3-
CN) δ -80.4 (relative to CFCl3); FABMS (m/z) 526 (M+ - 2TfO-).
Anal. Calcd for C28H22F6O6S4Te: C, 40.80; H, 2.69. Found: C, 40.46;
H, 2.71.
2,6-Bis[(phenylseleno)methyl]phenyl Phenyl Telluride (5). To a
dry CH3CN (100 mL) solution of 2,6-bis[(methoxy)methyl]phenyl
phenyl telluride (2b) (430 mg, 1.15 mmol) were added KI (1.5 g, 11.5
mmol) and AlCl3 (2.0 g, 11.5 mmol) at room temperature under an
argon atmosphere. The solution was stirred for 10 h, and then a mixture
of NaBH4 (65 mg, 1.72 mmol) and diphenyl diselenide (430 mg, 1.37
mmol) in CH3CN (20 mL) was added using a transfer needle. The
solution was stirred overnight, and then the solvent was evaporated at
room temperature. Saturated Na2S2O3 aqueous (100 mL) was added
to the residue, and the organic products extracted with ether, the organic
layer was separated and dried over anhydrous MgSO4, and the solvent
was removed. The crude product was purified by column chromatog-
raphy (silica gel; eluent, n-hexane-CH2Cl2, 4:1) to give a pale yellow
oil, telluride 5 (60 mg) in 8% yield. 1H NMR (400 MHz, CDCl3, room
temperature) δ 4.38 (s, 4H), 7.02-7.41 (m, 18H, Ar-H); 13C NMR
(100 MHz, CDCl3, room temperature) δ 40.0, 117.2, 123.0, 127.0,
127.4, 127.7, 128.9, 129.5, 130.2, 134.0, 134.8, 146.1; 125Te NMR (85
MHz, CDCl3, room temperature) δ 428.0 (JTe-Se ) 100 Hz) (relative
to Me2Te); 77Se NMR (51 MHz, CDCl3, room temperature) δ 387.3
(JTe-Se ) 100 Hz) (relative to Me2Se); MS (m/z); 620 (M+). Anal.
Calcd for C26H22Se2Te: C, 50.37; H, 3.58; Found: C, 50.18; H, 3.49.
2,6-Bis[(phenylseleno)methyl]phenyl Phenyl Telluranyl Bis(tet-
rafluoroborate) (6). An anhydrous CH3CN (10 mL) solution of
NOBF4 (30 mg, 0.26 mmol) was added dropwise to a solution of
telluride 5 (67 mg, 0.11 mmol) in anhydrous CH2Cl2 (20 mL) at -78
°C under an argon atmosphere. The resulting solution turned yellow.
When the addition was completed, the NO gas was removed under
vacuum. After stirring overnight, the solvents were evaporated at room
temperature, and recrystallization from CH2Cl2, CH3CN, and ether gave
yellow crystals of tellurane dication 2BF4- salt 6 (44 mg) in 51% yield.
2,6-Bis[(phenylthio)methyl]phenyl Phenyl Telluride (2a). n-BuLi
(4.8 mL, 7.6 mmol, 1.59 M in n-hexane) was added to a dry ether (40
mL) solution of 2,6-bis[(phenylthio)methyl]-1-bromobenzene (1a) (3.0
g, 6.9 mmol) at -78 °C under an argon atmosphere. As the reaction
proceeded the solution turned yellow. The solution was stirred for 30
min and then added to a solution of diphenyl ditelluride (1.4 g, 3.5
mmol) in dry Et2O (32 mL) using a transfer needle at -78 °C. The
resulting orange mixture was allowed to warm to room temperature
overnight. After the removal of solvents, the residue was extracted
with CH2Cl2, and the organic layer was dried over anhydrous MgSO4.
After the removal of solvent under vacuum at room temperature, the
crude product was subjected to column chromatography (silica gel;
eluent, n-hexane-CHCl3, 4:1) to give a mixture of two compounds.
These were separated by preparative liquid chromatography to afford
a white solid, telluride 2a (1.96 g) in 54% yield and the substrate (300
mg) in 10% recovery. Recrystallization of the telluride 2a from
1
n-hexane gave white crystals. Mp 55-56 °C; H NMR (270 MHz,
CDCl3, room temperature) δ 4.39 (s, 4H, CH2), 7.11-7.41 (m, 18H,
ArH). 13C NMR (68 MHz, CDCl3, room temperature) δ 45.7, 117.2,
123.8, 126.3, 127.0, 128.0, 128.6, 129.3, 129.4, 130.0, 135.2, 135.7,
144.1; 125Te NMR (85 MHz, CDCl3, room temperature) δ 445.7
(relative to Me2Te); MS (m/z) 528 (M+). Anal. Calcd for C26H22S2-
Te: C, 59.35; H, 4.21. Found: C, 59.28; H, 4.13.
2,6-Bis(methoxymethyl)phenyl Phenyl Telluride (2b). n-BuLi
(0.86 mL, 1.38 mmol, 1.60 M in n-hexane) was added to a dry ether
(20 mL) solution of 2,6-bis(methoxymethyl)phenyl bromide (1b)5 (337
mg, 1.38 mmol) at -78 °C under an argon atmosphere. The solution
was stirred for 30 min and then added to a solution of diphenyl
ditelluride (662 mg, 1.62 mmol) in dry Et2O (20 mL) using a transfer
needle under the same conditions. The resulting orange mixture was
allowed to warm to room temperature overnight. The solvents were
evaporated, and the residue was extracted with CH2Cl2. The organic
layer was dried over anhydrous MgSO4, and removal of the solvent at
room-temperature gave the crude product, which was subjected to
column chromatography (silica gel; eluent, n-hexane-CHCl3, 4:1) to
give a yellow oil, telluride 2b (429 mg) in 84% yield. 1H NMR (270
MHz, CDCl3, room temperature) δ 3.32 (s, 6H, CH3O), 4.54 (s, 4H),
7.12-7.43 (m, 8H, Ar-H). 13C NMR (68 MHz, CDCl3, room
temperature) δ 58.0, 116.6, 119.6, 127.1, 127.3, 129.3, 129.4, 135.7,
144.0; 125Te NMR (85 MHz, CDCl3, room temperature) δ 446.4
(relative to Me2Te); MS (m/z) 372 (M+). Anal. Calcd for C16H18O2-
Te: C, 51.95; H, 4.90. Found: C, 51.94; H, 4.90.
2,6-Bis[(phenylthio)methyl]phenyl Phenyl Telluroxide (3). The
telluride 2a (200 mg, 0.38 mmol) was dissolved in dry MeOH (2.5
mL)-CH2Cl2 (2.5 mL), and the solution was cooled to 0 °C. To this
t-BuOCl (47 µL, 0.42 mmol) was added, and the resulting solution
was stirred for 5 min at 0 °C. The reaction mixture was diluted with
dry CH2Cl2 (5 mL) and then hydrolyzed with a saturated aqueous
solution of sodium bicarbonate under vigorous stirring. After 5 min
the organic phase was separated, dried over anhydrous MgSO4, and
concentrated by evaporator to give a white solid, which was recrystal-
lized from n-hexane-CHCl3 to give telluroxide 3 (170 mg) in 83%
1
yield. Mp 155 °C; H NMR (270 MHz, CDCl3, room temperature) δ
4.19, 4.25 (ABq, 2H, J ) 16.2 Hz, CH2), 4.44, 4.50 (ABq, 2H, J )
16.2 Hz, CH2), 7.09-7.33 (m, 16H, ArH), 7.84-7.87 (m, 2H, ArH);
13C NMR (68 MHz, CDCl3) δ 37.2, 126.3, 128.8, 129.1, 129.3, 129.9,
(4) Vo¨gtle, F. Chem. Ber. 1969, 102, 1784-1788.
(5) Hellwinkel, D.; Krapp, W. Chem. Ber. 1978, 111, 13-41.

1232 J. Am. Chem. Soc., Vol. 120, No. 6, 1998
Bergholdt et al.
Table 1. X-ray Crystallographic Data for Diffraction Studies of 4a, 4b, and 6
compd
formula
fw
4a
4b
6
C28H25B2F8NS2Te
740.84
C32H28F6N2O6S4Te
906.41
C28H25B2F8NSe2Te
834.64
cryst syst
space group
a, Å
b, Å
c, Å
triclinic
triclinic
triclinic
P1h (no. 2)
10.011(4)
19.156(8)
8.675(4)
93.68(4)
111.23(3)
77.31(4)
1512(1)
2
P1h (no. 2)
8.629(1)
9.938(1)
19.207(2)
77.79(1)
86.53(1)
86.53(1)
1495.4(3)
2
P1h (no. 2)
12.569(1)
16.114(1)
9.887(1)
99.66(1)
104.13(1)
69.63(1)
1813.0(3)
2
1.66
R, deg
â, deg
γ, deg
V, Å3
Z
D
calcd, g cm-3
1.645
1.83
F(000)
temp, °C
radiation (λ, Å)
cryst dimens, mm
µ, cm-1
scan type
scan rate
scan width, deg
maxi 2θ, deg
tot no. of rflns
no. of unique rflns
no. of params refined
rflns included
732.0
23 ( 1
Mo KR (0.710 73)
0.15 × 0.40 × 0.95
12.05
704.0
804.0
23 ( 1
Cu KR (1.54178)
0.20 × 0.20 × 0.25
111.49
-60 ( 1
Mo KR (0.710 73)
0.15 × 0.30 × 1.00
11.27
200 × 200 mm plate
46 oscill. images
(6 min/exposure)
53.1
5281
5281
461
5052
ω-2θ
ω-2θ
2-20 deg/min
0.60 + 0.49 tanθ
55.9
16 deg/min
0.60 + 0.49 tanθ
135.2
7676
7202
469
5016
5661
5320
352
3799
(I > 5σ(I ))
(I > 5σ(I ))
(I > 3σ(I ))
agreement factorsa
R
Rw
0.038
0.041
0.043
0.048
0.071
0.076
a R ) ΣIIFoI - IFcII/ΣIFoI; Rw ) [Σw(IFoI - IFcI2]/ΣwFo2]1/2
.
Mp 201-204 °C (dec); 1H NMR (270 MHz, CD3CN, -40 °C) δ 4.37,
5.23 (ABq, J ) 17 Hz, 2H), 5.01, 5.25 (ABq, J ) 16 Hz, 2H), 6.7-
8.12 (m,18H, Ar-H); 13C NMR (68 MHz, CD3CN, room temperature)
δ 38.1, 38.4, 119.8, 125.1, 129.1, 129.6, 130.3, 131.3, 131.8, 132.1,
132.2, 132.4, 133.0, 133.9, 134.5, 134.7, 135.8, 147.7, 148.3; 125Te
NMR (85 MHz, CD3CN, -40 °C) δ 1174.9 (JTe-Se ) 443, 491 Hz)
(relative to Me2Te); 77Se NMR (51 MHz, CD3CN, -40 °C) δ 393.6
graphite monochromated Mo KR radiation. Unit cell parameters were
determined from a least-squares treatment of the SET4 setting angles
of 25 reflections in the range 9.00 < 2θ < 18.00 °. The intensities of
7202 reflections were corrected for Lp effects, absorption (DIFABS:10
correction range 0.68-1.00), and crystal decay (5.8%). The structure
was solved by direct methods11 and expanded using difference Fourier
syntheses. In the final cycle of full-matrix least-squares all non-
hydrogen atoms were refined anisotropically. The hydrogen atoms were
added to the respective carbon atoms at calculated positions, and
subsequently their coordinates were refined but their isotropic B's were
fixed. The remaining maximum and minimum electron density features
in the final difference Fourier map are equal to 0.75 and -0.81 e/Å3,
respectively.
(ii) Compound 4b. Data were collected at -60 ( 1 °C for a yellow
platelike crystal using a Rigaku RAXIS II imaging plate area detector
with graphite monochromated Mo-KR radiation. The unit cell
parameters were determined from a least-squares treatment of 30
reflections in the range 9.00 < 2θ < 18.00 °. The intensities of 5281
reflections were corrected for Lp effects and secondary extinction
(coefficient ) 1.84225e-06). The structure was solved by the heavy-
atom Patterson method12 and expanded using difference Fourier
syntheses. In the final cycle of full-matrix least-squares all non-
hydrogen atoms were refined anisotropically. The hydrogen atoms were
added to the respective carbon atoms at calculated positions but not
refined. The remaining maximum and minimum electron density
features in the final difference Fourier map are equal to 0.53 and -1.69
e/Å3, respectively.
(JSe-Te ) 443 Hz, JSe-Se ) 71 Hz), 462.3 (JSe-Te ) 491 Hz, JSe-Se
)
71 Hz) (relative to Me2Se); 19F NMR (254 MHz, CD3CN, room
temperature) δ -159 (BF4-) (relative to CFCl3); MS (m/z); 620 (M+
- 2BF4-); HRMS: calcd for C26H22Se2Te (M+ - 2BF4-) 352.0922,
found 352.0920.
Crystal Structure Determination of the Dicationic Telluranes 4a,
4b and 6. All crystals analyzed were mounted on top of a glass fiber,
and their respective X-ray data were collected using either a four-circle
diffractometer or an imaging plate area detector. The crystallographic
details are given in Table 1. Non-hydrogen atoms were modeled
anisotropically using neutral atom scattering factors. The hydrogen
atoms were added to the respective carbon atoms assuming either a
tetrahedral or planar geometry with the C-H distances equal to 0.97
or 1.08 Å. All structures were refined on F by full-matrix least-squares
techniques. The neutral atom scattering factors used in the refinements
were taken from Cromer and Waber6 and corrected for anomalous
dispersion7 using the f ′ and f ′′ values determined by Creagh and
McAuley.8 The teXsan9 crystallographic software package was used
for the refinement and geometrical calculations and molecular graphics.
All calculations were done on a Indy work station.
(iii) Compound 6. Data were collected at 13 ( 1 °C for a colorless
prismatic crystal using a Rigaku AFC7S four-circle diffractometer with
graphite monochromated Cu-KR radiation. Unit cell parameters were
determined from a least-squares treatment of the SET4 setting angles
(i) Compound 4a. Data were collected at 23 ( 1 °C for a yellow
platelike crystal using an Enraf-Nonius CAD4 diffractometer with
(6) Cromer, D. T., Waber, J. T. International Tables for X-Ray
Crystallography; The Kynoch Press: Birmingham, England, 1974; Vol. IV,
Table 2.2B.
(7) Ibers, J. A., Hamilton, W. C. Acta Crystallogr. 1964, 17, 781.
(8) Creagh, D. C., McAuley, W. J. International Tables for X-Ray
Crystallography; Kluwer Academic Publishers: Boston, 1992; Vol. C, p
219.
(10) DIFABS: Walker, N.; Stuart, D. Acta Crystallogr. 1983, A39, 158-
166. An empirical absorption correction program.
(11) Flank, D. H. Acta Crystallogr. 1983, A39, 876.
(12) PATTY: Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman,
W. P.; Garcia-Granda, S.; Gould, R. O.; Smits, J. M. M.; Smykalla, C. The
DIRDIF program system, Technical Report of the Crystallography Labora-
tory, University of Nijmegen: The Netherlands, 1992.
(9) teXsan: Crystal Structure Analysis Package; Molecular Structure
Corporation: 1985 and 1992.

Telluranes (λ4-Tellane), [10-Te-4(C2X2)]2+ (X ) S, Se)
J. Am. Chem. Soc., Vol. 120, No. 6, 1998 1233
Scheme 1a
a (i) PhSNa/EtOH/0 °C; (ii) n-BuLi/Et2O/-78 °C, PhTeTePh; (iii) t-BuOCl/MeOH-CH2Cl2/0 °C; (iv) KI/AlCl3/CH3CN/room temperature, PhSeNa.
Scheme 2
of 20 reflections in the range 33.2 < 2θ < 36.4°. The intensities of
5320 reflections were corrected for Lp effects and absorption (DIFABS:10
correction range 0.42-1.00). The structure was solved by direct
methods,11 expanded using difference Fourier syntheses, and refined
on F by full-matrix least-squares techniques. In the final cycle of full-
matrix least-squares all non-hydrogen atoms were refined anisotropi-
cally. The hydrogen atoms were added to the respective carbon atoms
at calculated positions but not refined. The remaining maximum and
minimum electron density features in the final difference Fourier map
are equal to 1.74 and -1.44 e/Å,3 respectively.
Electrochemical Study. Peak potentials of the first oxidation peak
were determined at a glassy carbon electrode with 2 mM samples in
dry CH3CN-0.1 M NaClO4 vs Ag/AgCl in 3 M KCl, 100 mV/s scan
rate.
Ab Initio Calculations. Ab initio single-point calculations of the
dications were carried out on a HP735/125 workstation using Spartan
version 3.1.13 The X-ray molecular structures of 4b and 6 were used.
The RHF method was employed with the 3-21G(*) basis set which
includes d polarization functions on sulfur, selenium, and tellurium
atoms. The atomic charges were calculated by the natural population
analysis.14
Results and Discussion
Syntheses and Characterization. The compounds 2a, 3,
and 5 were synthesized as shown in Scheme 1 and characterized
by various spectroscopies and elemental analyses. Interestingly,
the 77Se and 125Te NMR spectra of compound 5 show satellite
peaks between the selenium and tellurium atoms although there
are no Se-Te bonds. The coupling constant (JSe-Te) is 100
Hz. This spin-spin coupling may be due to an interaction
through the carbon bonds between selenium and tellurium atoms,
as opposed to a through space one.
The existence of an interaction between the three chalcogen
atoms in 2a or 5 was apparent from cyclic voltammetry studies,
because 234 or 277 mV reduction in the oxidation potentials
was observed when 2a (666 mV) or 5 (623 mV) was compared
with diphenyl telluride (Ph-Te-Ph) (900 mV). In contrast to
diphenyl telluride which showed an irreversible oxidation wave,
both 2a and 5 exhibited pseudoreversible behavior, indicating
a stabilizing effect by the introduction of the two phenylthio-
or phenylselenomethyl ligands. Compounds 2a and 5 were
readily oxidized by, for example, adding a solution of anhydrous
CH2Cl2 containing NOBF4 (2 equiv) dropwise to a solution of
anhydrous CH2Cl2/CH3CN containing 2a or 5 at -78 °C under
an argon atmosphere. After removal of the solvent, the tellurane
dication 2BF4- salts (4a) and (6) were isolated in 92% and 51%
yield, as yellow solids, respectively.
argon at 0 °C resulted in its conversion to the yellow tellurane
dication 2CF3SO3 salt, 4b. We also tried to synthesize the
telluroxide from the corresponding telluride 5 in the m-CPBA
as an oxidant to mimic the above reaction. However, we could
not obtain the pure telluroxide because the products are unstable
and readily decompose at room temperature.
-
Subsequent crystallization from an ether-CH3CN solution
gave yellow crystals of 4a, 4b, and 6, as shown in Scheme 2.
1
To determine the structures of 4a, 4b, and 6, H, 13C, and
125Te NMR spectra were measured. The 1H NMR spectrum of
each compound when measured in CD3CN at 20 °C exhibits
the benzylic methylene protons as two sets of AB quartet signals
at δ 4.95, 5.21 (J ) 17.3 Hz) and δ 4.45, 5.15 (J ) 17.1 Hz);
δ 4.45, 5.13 (J ) 17.7 Hz) and δ 5.09, 5.24 (J ) 17.0 Hz); and
δ 4.26, 5.23 (J ) 16.0 Hz) and 4.96, 5.23 (J ) 15.0 Hz) in a
1:1 ratio, respectively. These signals were assigned to the
asymmetric bicyclic form. The 125Te NMR spectra of 4a and
4b show only a single peak at 1327.3 and 1330.7 ppm,
respectively. However, the 125Te NMR spectrum of 6 shows
one peak at 1174.9 ppm at -40 °C with four satellite peaks
due to the spin-spin coupling (1JTe-Se ) 443, 491 Hz) between
the central tellurium and two asymmetric selenium atoms as
shown in Figure 2. The 77Se chemical shifts of 6 appear at
393.6 and 462.3 ppm at -40 °C with some satellite peaks.
Interestingly, each site shows four satellite peaks due to not
Treating the corresponding telluroxide 3 with trifluoromethane-
sulfonic anhydride [(CF3SO2)2O; 1 equiv] in dry CH3CN under
(13) Hehre, W. J. Spartan ver. 3.1: Wavefunction, Inc.: Irvine, CA.

1234 J. Am. Chem. Soc., Vol. 120, No. 6, 1998
Bergholdt et al.
Figure 2. 125Te NMR spectrum of 6.
Figure 3. 77Se NMR spectrum of 6.
Figure 5. A ball and stick view of 4a, 4b, and 6. For clarity, the three
phenyl rings on chalcogen atoms were omitted.
Figure 4. Isomers of 4 (X ) S) and 6 (X ) Se).
only the spin-spin coupling (1JSe-Te ) 443, 491 Hz) between
the selenium and tellurium atoms but also due to the coupling
(2JSe-Se ) 71 Hz) between selenium atoms through the tellurium
atom as shown in Figure 3. Such an example of spin-spin
coupling through a three-center four-electron bond has not been
reported and is thus an addition to the very interesting behavior
of hypervalent chemistry. These results indicate that compound
5 also exists in the asymmetric bicycle form and support the
bond formation between the tellurium and selenium atoms.
In principle, the dications 4a, 4b, and 6 could exist as one of
the following three possible stereoisomers: cis-trans, trans-
cis (dl-pairs), and/or trans-trans (meso) and/or cis-cis (meso),
as shown in Figure 4. The trans-trans isomer is expected to
be the most sterically stable configuration of the dicationic
telluranes. However, the NMR spectra of these compounds
indicate that these structures have either a cis-trans or trans-
cis configuration. Furthermore, the elemental analyses of 4a,
4b, and 6 are consistent with the molecular formula of the
corresponding dicationic tellurane, and the FAB-mass spectra
of 4a, 4b, and 6 show the molecular ion at m/e 526 (M+ - 2
counteranions) and m/e 620 (M+ - 2BF4-), respectively.
X-ray Crystallographic Analyses. Suitable crystals for
X-ray analysis were obtained by recrystallization of 4a and 4b
from dry solutions of CD3CN at 0 °C. The dication structure
of 4b is similar to that of 4a. A ball and stick view of 4a and
4b is shown in Figure 5. The X-ray crystal structure determi-
nation of 4a establishes that in the solid state this compound
exists only as one isomer and is the first example of a dicationic
σ-tellurane with two apical sulfonio ligands. Crystals of 4a and
4b contain not only two counteranions (2BF4 or 2TfO-,
-
respectively) but also one molecule of acetonitrile as a lattice
solvate. The favored stereoisomer has the trans-cis or cis-
trans conformation, which is in agreement with the NMR results.
The respective bond lengths Te(1)-S(1) (2.706(1) and 2.652-

Telluranes (λ4-Tellane), [10-Te-4(C2X2)]2+ (X ) S, Se)
J. Am. Chem. Soc., Vol. 120, No. 6, 1998 1235
Table 2. Selected Bond Distances (Å) and Angles (deg) with
Esd’s in Parentheses for 4a, 4b, and 6a
(1) Å) and Te(1)-S(2) (2.661(1) and 2.654(1) Å) are longer
than the normal Te-S single bond (2.36 Å).15 The bond angles
S(1)-Te(1)-S(2) and C(1)-Te(1)-C(9) are equal to 160.4(4)°,
162.54(5)° and 98.5(2)°, 95.5(2)°, respectively. Thus, the Te-
(1) atoms of 4a and 4b have a distorted trigonal bipyramidal
bonding geometry with two apical Te-S bonds, two equatorial
Te-C bonds, and the lone-pair of electrons occupying the third
equatorial position. These structural features are very similar
to those observed in the normal noncharged tellurane(IV)
compounds.16
4a (X ) S)
4b (X ) S)
6 (X ) Se)
Te(1)-X(1)
Te(1)-X(2)
Te(1)-C(1)
Te(1)-C(9)
X(1)-C(7)
X(1)-C(15)
X(2)-C(8)
X(2)-C(21)
2.706(1)
2.661(1)
2.114(4)
2.096(5)
1.798(6)
1.779(5)
1.808(6)
1.785(5)
2.652(1)
2.654(1)
2.108(5)
2.118(5)
1.800(6)
1.775(6)
1.793(6)
1.782(5)
2.807(2)
2.759(2)
2.17(1)
1.92(1)
1.96(1)
1.94(1)
1.98(1)
1.92(1)
Suitable crystals for X-ray analysis were obtained by recrys-
tallization of 6 from dry solutions of CD3CN/Et2O at 0 °C. The
X-ray crystal structure determination of 6 establishes that in
the solid state it also exists only in the trans-cis or cis-trans
conformation and is the first example of a dicationic σ-tellurane
with two apical selenonio ligands as shown in Figure 5. In
addition to the two counteranions (2BF4-) this crystal also
contains one molecule of acetonitrile as a lattice solvate. The
bond lengths Te(1)-Se(1) (2.759(2) Å) and Te(1)-Se(2)
(2.807(2) Å) are longer than the normal Te-Se single bond
(2.519 Å).15 The bond angles Se(1)-Te(1)-Se(2) and C(1)-
Te(1)-C(9) are equal to 163.93(5) ° and 99.0(5) °, respectively.
The Te(1) of 6 has the same configuration as that of compounds
4a and 4b.
X(1)-Te(1)-X(2)
X(1)-Te(1)-C(1)
X(1)-Te(1)-C(9)
X(2)-Te(1)-C(1)
X(2)-Te(1)-C(9)
C(1)-Te(1)-C(9)
Te(1)-X(1)-C(7)
Te(1)-X(1)-C(15)
Te(1)-X(2)-C(8)
Te(1)-X(2)-C(21)
160.41(4)
80.1(1)
90.4(1)
80.5(1)
89.6(1)
98.5(2)
91.4(2)
105.5(2)
92.8(2)
99.1(1)
162.54(5)
81.7(1)
93.3(1)
81.1(1)
91.2(1)
95.5(2)
95.6(2)
106.7(2)
95.0(2)
92.0(2)
163.93(5)
82.4(4)
90.5(3)
81.9(4)
88.6(3)
99.0(5)
87.2(4)
102.9(4)
88.7(4)
96.3(4)
a Numbers in parentheses are estimated standard deviations in the
least significant digits.
According to crystal packing of these dication compounds,
the chalcogen atoms of 4a, 4b, and 6 are weakly coordinated
by the fluorine of BF4- or oxygen of CF3SO3- and nitrogen of
acetonitrile. The compounds 4a and 6 have two tetrafluorobo-
rate anions and one acetonitrile, and 4b has one triflate anion
and two acetonitrile molecules in each unit cell as shown in
Figure 5. The chalcogen atoms making up the three-center four-
electron bond have from one to three secondary bonds, and these
bond lengths are within van der Waals radii of each bond (F-
Te ) 3.55, F-S ) 3.20, F-Se ) 3.35, O-Te ) 3.60, O-S )
3.25, O-Se ) 3.40, N-Te ) 3.70, N-S ) 3.35, and N-Se )
3.50 Å).16 These results indicate that the three chalcogen atoms
of 4a, 4b, and 6 have highly positive charges. In summary,
the crystal structures of 4a, 4b, and 6 are very similar as shown
in Table 2.
Figure 6. The charge distribution (natural population analysis) in the
tellurane dications 4b and 6.
Table 3. Comparison of the Electronic Structures of Dications 4b
(X ) S) and 6 (X ) Se)
Theoretical Calculations. To understand the electronic
structure of the dicationic σ-telluranes, single point ab initio
calculations were carried out using the crystal structures of 4b
and 6. The calculations were carried out at the RHF/3-21G(*)
level. The atomic charges were evaluated by the natural
population analysis;14 this method is particularly more suitable
than the traditional Mulliken population analysis for hypervalent
species which have strongly polar bonds.17 The charge distribu-
tions in the two dications are shown in Figure 6, and various
electronic properties are summarized in Table 3.
quantity
atomic chargea
atom or bond
4b (X ) S)
6 (X ) Se)
Te
+1.600
+0.483
+0.495
0.501
0.501
3.02
2.43
2.43
0.034
+1.422
+0.602
+0.615
0.556
0.587
3.08
2.59
2.61
0.033
X(1)
X(2)
Te-X(1)
Te-X(2)
Te
X(1)
X(2)
Te
bond orderb
valencyb
5d occupancya
a Natural population analysis. b Mulliken values.
The atomic charges of Te(1), S(1), and S(2) in 4b were
calculated to be +1.600, +0.483, and +0.495, respectively.
Thus, the total positive charge of +2.578 is located exclusively
on the three chalcogen atoms of hypervalent bonding system.
The charge is larger than two due to the polarization of Te-C
and S-C bonds. In addition, the hypervalent apical bonds seem
to be polarized as is normally observed in hypervalent mol-
ecules, since the positive charges of S(1) and S(2) are
substantially smaller than one (the charge of the sulfur atom in
the trimethylsulfonium cation is calculated to be +0.98 by the
same method of calculation). In 6, the Te(1) atom is less
positively charged than in 4b, and the positive charges on Se-
(1) and Se(2) are larger than those of the sulfur atoms in 4b,
simply reflecting the fact that the electronegativity of selenium
is smaller than that of sulfur.
(14) Reed, A. E.; Weinstock, R. B.; Weinhold, F. J. Chem. Phys. 1985,
83, 735-746.
(15) (a) Hargittai, I.; Rozsondai, B. Structural chemistry of organic
compounds containing selenium or tellurium. In The chemistry of organic
selenium and tellurium compounds; Patai, S.; Rappoport, Z.; Eds.; John
Wiley and Sons: Inc.: New York, 1986; Vol. 1, p 78. (b) Pauling, L. The
Nature of the Chemical Bond, 3rd ed.; Cornell University Press: Ithaca,
NY, 1960; p 260.
(16) (a) Smith, I. C. S.; Lee, J.-S.; Titus, D. D.; Ziolo, R. F. Organo-
metallics 1982, 1, 350. (b) Michalak, R. S.; Wilson, S. R.; Martin, J. C. J.
Am. Chem. Soc. 1984, 106, 7529. (c) Sato, S.; Kondo, N.; Furukawa, N.
Organometallics 1994, 13, 3393-3395. (d) Sato, S.; Kondo, N.; Furukawa,
N. Organometallics 1995, 14, 5393-5398. (e) Takaguchi, Y.; Fujihara, H.;
Furukawa, N. Heteroatom Chem. 1995, 6, 481.
(17) Reed, A. E.; Weinhold, F. J. Am. Chem. Soc. 1986, 108, 3586-
3593.

1236 J. Am. Chem. Soc., Vol. 120, No. 6, 1998
Bergholdt et al.
Scheme 3
ferent from those in crystals and in solutions and that the
interactions between the dication and counterions are essentially
electrostatic.
Conclusions
In conclusion, the chemical properties and preparation of a
new type of dicationic σ-telluranes (λ4-tellane), [10-Te-4]2+
salts from the new flexible acyclic tris-chalcogenide via tran-
sannular bond formation were studied. Single crystal X-ray
structure determinations revealed that two apical sulfonio- or
selenonio ligands bond to the central tellurium atom via
transannular bond formation. Furthermore, the computational
results show that the dicationic telluranes contain a positively
charged hypervalent bond, which accordingly can be character-
ized as an electron rich three atom center bonding system (3c-
4e) with positively charged atoms. Further studies on the
characterization of hypervalent chalcogenurane dications are in
progress.
The Mulliken bond orders of Te(1)-S(1) and Te(1)-S(2) in
4b are 0.501, which is almost equal to the maximum value (0.5)
attainable by the three-center four-electron (3c-4e) bond model
using only an sp basis set.18 The Te(1)-Se(1) and Te(1)-Se(2)
bond orders of 6 are somewhat larger. The total 5d-orbital
population of tellurium is small (about 0.03) both in 4b and in
6, and the d orbitals are not primarily concerned with the Te-S
and Te-Se bonds. The Mulliken valency values, about 3, 2.4,
and 2.6 for the tellurium, sulfur, and selenium atoms, respec-
tively, are consistent with the resonance as shown in Scheme
3.
Acknowledgment. The authors wish to thank Dr. A.
Yamano et al., Rigaku Co., for their fruitful help in X-ray
crystallographic analysis. This work was supported by the
Ministry of Education, Science, Sports and Culture, Japan
[Grant-in-Aid for Scientific Research on Priority Areas: Grant
No. 05236205, Grant-in-Aid for Scientific Research (A): Grant
No.08304037, and Grant-in-Aid for Encouragement of Young
Scientists: Grant No. 08740484], and the Fund of Tsukuba
Advanced Research Alliance (TARA) project [University of
Tsukuba], the Scandinavian-Japan Sasakawa Foundation, and
Research Foundation For Materials Science.
As shown in Figure 6, the positive charges are not delocalized
onto the phenyl ring systems. This can be explained by the
following molecular orbital consideration. Delocalization of the
positive charges implies that electrons are pulled into the
hypervalent bond, and this would require that electrons are
placed in the antibonding molecular orbital which is unfavorable.
The counterion and solvent molecules were not included in
the ab initio calculations. It should be noted, however, that the
positive charges are exclusively carried by the three chalcogen
atoms without the presence of counterions; further charge locali-
zation induced by counterions is not expected. Charge transfer
interaction is also possible, but its amount is expected not to
be large judging from the interatomic distances between the
dication and counterions. Therefore, we think that the charge
distributions calculated for the isolated dications are not so dif-
Supporting Information Available: Detailed crystallo-
graphic data, positional and thermal parameters, and bond
distances and angles of 4a, 4b, and 6 (56 pages). See any
current masthead page for ordering and Internet access
instructions.
(18) Mayer, I. J. Mol. Struct. (THEOCHEM) 1989, 186, 43-52.
JA972930X