2,2,4,4,6,6-Hexabenzylcyclotristannatellurane, (Bn2SnTe)3. Synthesis and Structural Characterization of an Organometallic Single-Source Precursor to Phase-Pure, Polycrystalline SnTe

Article abstract of DOI:10.1021/om990506u

The title compound, (Bn₂SnTe)₃, Bn = CH₂CeH₅, was prepared in high yield by treating Bn₂SnCl₂ with (NH₄)₂Te. Details of the synthesis and characterization (¹

Full text of DOI:10.1021/om990506u

4534
Organometallics 1999, 18, 4534-4537
2,2,4,4,6,6-Hexa ben zylcyclotr ista n n a tellu r a n e,
(Bn 2Sn Te)3. Syn th esis a n d Str u ctu r a l Ch a r a cter iza tion of
a n Or ga n om eta llic Sin gle-Sou r ce P r ecu r sor to
P h a se-P u r e, P olycr ysta llin e Sn Te
Philip Boudjouk,* Michael P. Remington, J r., Dean G. Grier,
Wayne Triebold, and Bryan R. J arabek
Center for Main Group Chemistry, Department of Chemistry, North Dakota State University,
Fargo, North Dakota 58105
Received J uly 1, 1999
The title compound, (Bn2SnTe)3, Bn ) CH2C6H5, was prepared in high yield by treating
Bn2SnCl2 with (NH4)2Te. Details of the synthesis and characterization (1H, 13C, 119Sn, and
125Te NMR; IR, single-crystal XRD, and elemental analyses) are presented. (Bn2SnTe)3 serves
as an efficient single-source precursor to phase-pure cubic SnTe under mild conditions
In tr od u ction
14-16 material in high yields and high purity by
homolytic bond cleavage of the C-Sn bond.10a This route
has the advantages of utilizing mild decomposition
temperatures, producing an inert and easily removed
organic byproduct, 1,2-diphenylethane, and controlling
the stoichiometry of the end members as well as the
corresponding solid solutions, SnSxSe1-x. Easy access to
solid solutions allows tailoring of the band gap.11
Furthering our investigation of molecular precursors
to 14-16 materials, we report here the synthesis, char-
acterization, and decomposition of the novel six-mem-
bered ring containing alternating Sn and Te atoms,
(Bn2SnTe)3. This compound serves as an organometallic
single-source precursor to cubic SnTe under mild ther-
mal conditions (g200 °C). Homolytic bond cleavage of
the Sn-C bond and the formation of 1,2-diphenylethane
is the dominant mechanism.
Tin telluride and other tin chalcogenides are widely
used as semiconductors.1 For example, SnTe, with a
direct Eg of 0.18 eV,2 has found application in infrared
detection, radiation receiving, and thermoelectric de-
vices.3 Interest in the structure and bonding of 14-16
materials has also driven research in this area.4 Syn-
thetic routes to these materials include heating mix-
tures of the elements at high temperatures for extended
time periods,5 reaction of the elements in liquid am-
monia,6 precipitation from aqueous solutions,7 organo-
metallic chemical vapor deposition (OMCVD),8 solid-
state metathesis,9 and, more recently, pyrolysis of
organometallic single-source precursors.10
We have demonstrated that ring systems of the type
(Bn2SnE)3, (Bn ) CH2C6H5, E ) S or Se) provide the
(1) Berger, L. I. Semiconductor Materials; CRC Press: New York,
1997.
Resu lts a n d Discu ssion
(2) (a) Fouad, S. S.; Morsy, A. Y.; Soliman, H. S.; Ganainy, G. A. J .
Mater. Sci. Lett. 1994, 13, 82. (b) Rogers, L. M. Br. J . Appl. Phys. 1968,
1, 845. (c) Esaki, L.; Stiles, P. J . Phys. Rev. Lett. 1966, 16, 1108.
(3) (a) George, J .; Palson, T. I. Thin Solid Films 1985, 127, 233,
and references therein. (b) Santhanam, S.; Chaudhuri, A. K. Phys.
Status Solidi A 1984, 83, k77. (c) Reynolds, R. A. J . Electrochem. Soc.
1967, 114, 526. (d) Brebrick, R. F.; Strauss, A. J . Phys. Rev. 1963, 131,
104.
(4) (a) Lin, J .-C.; Ngai, T. L.; Chang, Y. A. Metall. Trans. A 1986,
17A, 1241. (b) Rabe, K. M.; J oannopoulos, J . D. Phys. Rev. B 1985, 32,
2302. (c) Miller, A. J .; Saunders, G. A.; Yogurtc¸u, Y. K. J . Phys. C:
Solid State Phys. 1981, 14, 1569. (d) Littlewood, P. B. J . Phys. C: Solid
State Phys. 1980, 13, 4855.
P r ecu r sor Syn th esis. Cyclic tin chalcogenides can
be prepared by the reaction of a dialkyldihalostannane,
R2SnX2, with alkali metal chalcogenolates, MEH,12 or
by treating elemental chalcogens with dialkylstan-
nanes.13 Recently we reported that these compounds are
accessible in good to excellent yields from R2SnX2 and
freshly prepared anhydrous alkali metal chalcogenides,
M2E10a,c (eq 1).
(5) (a) Greenwood, N. N., Earnshaw, A., Eds.; Chemistry of the
Elements; Permagon: New York, 1990. (b) Blitz, W.; Mecklenburg, W.
Z. Anorg. Allg. Chem. 1909, 64, 226. (c) Abrikosov, N. K.; Bankina, V.
F.; Poretskaya, L. V.; Shelimova, L. E. Semiconducting II-VI, IV-VI,
and V-VI Compounds; Plenum: New York, 1969. (d) Yellin, N.; Ben-
Dor, L. Mater. Res. Bull. 1983, 18, 823.
(6) Henshaw, G.; Parkin, I. P.; Shaw, G. A. J . Chem. Soc., Dalton
Trans. 1997, 231.
(7) Gorer, S.; Albu-Yaron, A.; Hodes, G. Chem. Mater. 1995, 7, 1243.
(8) Manasevit, H. M.; Simpson, W. I. J . Electrochem. Soc. 1975, 122,
444.
Na2E f 1/3(R2SnE)3
R ) Ph, Bn; E ) S, Se
R2SnX2 +
+ 2 NaX (1)
Attempts to produce the tellurium analogue, with R
) Bn, in our laboratory by eq 1 failed. Typically,
tellurium powder was the major product. However,
when we use ammonium telluride, prepared as in eq
(9) Parkin, I. P.; Rowley, A. T. Polyhedron 1993, 12, 2961.
(10) (a) Boudjouk, P.; Seidler, D. J .; Grier, D.; McCarthy, G. J . Chem.
Mater. 1996, 8, 1189. (b) Boudjouk, P.; Seidler, D. J .; Bahr, S. R.;
McCarthy, G. J . Chem. Mater. 1994, 6, 2108. (c) Boudjouk, P.; Bahr,
S. R.; McCarthy, G. J . Chem. Mater. 1992, 4, 383. (d) Seligson, A. L.;
Arnold, J . J . Am. Chem. Soc. 1993, 115, 8214. (e) Cowley, A. H.; J ones,
R. A. Angew. Chem., Int. Ed. Engl. 1989, 28, 1208.
(11) Pierson, H. O. Handbook of Chemical Vapor Deposition (CVD):
Principles, Technology and Applications; Noyes Publications: Park
Ridge, NJ , 1992.
(12) Blecher, A.; Dra¨ger, M. Angew. Chem., Int. Ed. Engl. 1979, 18,
677.
(13) Blecher, A.; Mathiasch, B. Z. Naturforsch. B 1978, 33, 246.
10.1021/om990506u CCC: $18.00 © 1999 American Chemical Society
Publication on Web 09/30/1999

2,2,4,4,6,6-Hexabenzylcyclotristannatellurane
Organometallics, Vol. 18, No. 22, 1999 4535
Ta ble 1. Cr ysta llogr a p h ic Da ta for (Bn 2Sn Te)3
empirical formula
fw
C42H42Sn3Te3
1285.63
temperature
wavelength
crystal system
space group
unit cell dimens
298(2) K
0.71073 Å
triclinic
P1h
a ) 11.2391(6) Å, R ) 89.9940(10)°
b ) 17.2765(8) Å, â ) 89.9750(10)°
c ) 23.6362(12) Å, γ ) 75.4250(10)°
4441.8(4) Å3
volume
Z
4
density (calcd)
abs coeff
1.922 Mg/m3
3.631 mm-1
F(000)
2400
crystal size
θ range for data collection
index ranges
0.35 × 0.45 × 0.65 mm3
0.86-19.00°
-10 e h e 14, -21 e k e 23,
-29 e l e 30
Figu r e 1. Molecular structure and atom-numbering scheme
for the asymmetric unit of (Bn2SnTe)3. The phenyl groups
of the benzyl moieties have been removed for clarity.
reflns collected
12060
indep reflns
abs corr
6950 [R(int) ) 0.1616]
none
refinement method
no. of data/restraints/params
goodness-of-fit on F2
final R indices [I>2σ(I)]
R indices (all data)
largest diff peak and hole
full-matrix least-squares on F2
6918/0/865
1.075
R1 ) 0.0716, wR2 ) 0.1814
R1 ) 0.0762, wR2 ) 0.1936
1.465 and -1.706 e Å-3
Ta ble 2. Selected Bon d Len gth s [Å] a n d An gles
[d eg] for (Bn 2Sn Te)3
molecule 1
molecule 2
Sn(1)-Te(1)
2.729(2)
2.738(2)
2.7368(15)
2.741(2)
2.720(2)
2.7322(15)
2.17(2)
2.17(2)
2.18(2)
2.18(2)
2.15(2)
Sn(4)-Te(6)
2.730(2)
2.738(2)
2.7359(15)
2.742(2)
2.721(2)
2.736(2)
2.17(2)
2.16(2)
2.18(2)
2.21(2)
2.15(2)
2,14 as the source of Te2-, the reaction proceeds ef-
ficiently.
Sn(1)-Te(3)
Sn(2)-Te(2)
Sn(2)-Te(1)
Sn(3)-Te(3)
Sn(3)-Te(2)
Sn(1)-C(1)
Sn(1)-C(8)
Sn(2)-C(15)
Sn(2)-C(22)
Sn(3)-C(29)
Sn(3)-C(36)
Sn(4)-Te(4)
Sn(6)-Te(5)
Sn(6)-Te(6)
Sn(5)-Te(4)
Sn(5)-Te(5)
Sn(4)-C(43)
Sn(4)-C(50)
Sn(5)-C(57)
Sn(5)-C(64)
Sn(6)-C(71)
Sn(6)-C(78)
3Te + 6NH4OH + 2Al f 3(NH4)2Te + 2Al(OH)3 (2)
The reaction of a deoxygenated aqueous solution of
ammonium telluride with an ether solution of diben-
zyltin dichloride produces 2,2,4,4,6,6-hexabenzylcyclo-
tristannatellurane, (Bn2SnTe)3, in very good yields (ca.
80%). A gray precipitate composed of SnTe, Te, and NH4-
Cl, as shown by X-ray powder diffraction (XRPD), is also
produced.
Molecu la r Str u ctu r e. Recrystallization of (Bn2-
SnTe)3 from Et2O provides yellow crystals that are
suitable for single-crystal X-ray diffraction (SCXRD).
(Bn2SnTe)3 crystallizes in the triclinic space group P1h
with two independent molecules in the asymmetric
unit.15 Table 1 summarizes the crystal data and struc-
ture refinement. The molecular structure and atom-
numbering scheme of (Bn2SnTe)3 are shown in Figure
1, selected bond distances and angles in Table 2, and
atomic parameters in Table 3.
The (SnTe)3 ring is in a distorted boat conformation.
The geometry of the (SnTe)3 ring is in excellent agree-
ment with that of the methyl analogue, (Me2SnTe)3,
with average Te-Sn-Te and Sn-Te-Sn bond angles
of 113.41° and 95.82° vs 112.6° and 96°, respectively.12
The tin atoms form a tetrahedron with an average
C-Sn-C angle of 109.6° (ranging from 112.9° to 106.5°),
distinctly more acute than the methyl analogue (av
113°).12 The Sn-Te and Sn-C bond distances are
similar to those reported for other Sn(IV)-Te ring
structures.12,16
2.15(2)
2.15(2)
Te(1)-Sn(1)-Te(3) 111.24(5) Te(6)-Sn(4)-Te(4) 111.32(5)
Te(2)-Sn(2)-Te(1) 115.71(5) Te(5)-Sn(6)-Te(6) 115.68(5)
Te(3)-Sn(3)-Te(2) 113.28(5) Te(4)-Sn(5)-Te(5) 113.20(5)
C(8)-Sn(1)-C(1)
112.9(10) C(43)-Sn(4)-C(50) 111.1(8)
C(15)-Sn(2)-C(22) 109.5(6)
C(29)-Sn(3)-C(36) 106.5(7)
C(78)-Sn(6)-C(71) 109.6(8)
C(57)-Sn(5)-C(64) 108.0(7)
C(43)-Sn(4)-Te(6) 109.1(5)
C(43)-Sn(4)-Te(4) 112.3(5)
C(50)-Sn(4)-Te(6) 106.6(5)
C(50)-Sn(4)-Te(4) 106.2(6)
C(71)-Sn(6)-Te(6) 107.0(5)
C(71)-Sn(6)-Te(5) 118.1(5)
C(78)-Sn(6)-Te(6) 105.5(4)
C(1)-Sn(1)-Te(1)
C(1)-Sn(1)-Te(3)
C(8)-Sn(1)-Te(1)
C(8)-Sn(1)-Te(3)
C(15)-Sn(2)-Te(1) 107.1(5)
C(15)-Sn(2)-Te(2) 117.4(5)
C(22)-Sn(2)-Te(1) 105.4(5)
C(22)-Sn(2)-Te(2) 100.9(4)
C(29)-Sn(3)-Te(2) 111.5(5)
C(29)-Sn(3)-Te(3) 104.7(6)
C(36)-Sn(3)-Te(2) 104.4(5)
C(36)-Sn(3)-Te(3) 116.3(4)
110.1(5)
112.0(5)
106.0(7)
104.3(7)
C(78)-Sn(6)-Te(5)
99.9(5)
C(57)-Sn(5)-Te(5) 104.1(4)
C(57)-Sn(5)-Te(4) 116.5(5)
C(64)-Sn(5)-Te(5) 110.9(5)
C(64)-Sn(5)-Te(4) 104.1(5)
Sn(1)-Te(1)-Sn(2)
Sn(3)-Te(2)-Sn(2)
Sn(3)-Te(3)-Sn(1)
93.71(4) Sn(4)-Te(6)-Sn(6)
99.10(4) Sn(5)-Te(5)-Sn(6)
94.66(5) Sn(5)-Te(4)-Sn(4)
93.66(4)
99.13(5)
94.65(5)
chains lying parallel to the b-axis. These chains super-
impose along the a-axis. The shortest intermolecular
nonbonding distances occur between the methylene
proton of one benzyl group on each of Sn(2) and Sn(6)
with the lone pair of electrons on neighboring tellurium
atoms Te(4) and Te(3), respectively. These distances are
3.160 Å for H22a-Te4 and 3.192 Å for H78a-Te3
(Figure 1).
An interesting feature of the solid-state structure of
(Bn2SnTe)3 is the packing of the molecules into infinite
(14) Nitsche, R. Angew. Chem. 1957, 69, 333.
(15) While the metric parameters suggest a monoclinic unit cell, the
triclinic structure given here was the only setting that provided a
satisfactory solution. The germanium analogue, (Bn2GeTe)3 (our
unpublished results), however, which displays similar molecular
geometry and intermolecular interactions, crystallizes in the monoclinic
P21/c space group.
Syn th esis a n d Ch a r a cter iza tion of Sn Te. Pyroly-
sis of (Bn2SnTe)3 in a conventional flow pyrolysis unit
at 200 or 275 °C, for 10 h, or at 400 °C for 5 h produced
SnTe in high yield (eq 3). These low temperatures are
comparable to those used in the preparation of SnTe
from homoleptic Sn(II) tellurolates (ca. 250 °C).10d
(16) Puff, H.; Breuer, B.; Schuh, W.; Sievers, R.; Zimmer, R. J .
Organomet. Chem. 1987, 332, 279.

4536 Organometallics, Vol. 18, No. 22, 1999
Boudjouk et al.
Ta ble 3. Selected Atom ic Coor d in a tes (× 104) a n d
Equ iva len t Isotr op ic Disp la cem en t P a r a m eter s
a
(Å2 × 103) for (Bn 2Sn Te)3
x
y
z
U(eq)
Sn(1)
Sn(2)
Sn(3)
Sn(4)
Sn(5)
Sn(6)
Te(1)
Te(2)
Te(3)
Te(4)
Te(5)
Te(6)
10441(1)
9556(1)
10478(1)
10439(1)
10480(1)
9558(1)
9851(1)
11299(1)
8962(1)
8962(1)
11302(1)
9851(1)
4588(1)
6078(1)
3611(1)
9589(1)
8609(1)
11079(1)
6203(1)
4913(1)
3877(1)
8877(1)
9914(1)
11204(1)
8033(1)
6722(1)
6491(1)
6967(1)
8509(1)
8279(1)
7866(1)
6189(1)
7406(1)
7594(1)
8810(1)
7133(1)
61(1)
49(1)
54(1)
61(1)
55(1)
50(1)
63(1)
64(1)
65(1)
64(1)
64(1)
64(1)
F igu r e 2. XRPD pattern of SnTe from pyrolysis of (Bn2-
SnTe)3 at 275 °C for 10 h.
a
U(eq) is defined as one-third of the trace of the orthogonalized
Uij tensor.
Ta ble 4. XRD Mea su r ed Un it-Cell P a r a m eter s for
Sn Te
(Bn2SnTe)3 f 3SnTe + 3Bn2
(3)
reference
a, Å
volume, Å3
Thermolysis at the lower temperatures resulted in
yields of SnTe slightly greater than predicted (av 102%),
suggesting incomplete reaction and/or retention of
organic species. Total mass recovery (nonvolatile +
volatile products) was good at 85%. Trace combustion
analysis of the ceramic product showed <1% carbon and
hydrogen, which were reduced to <0.5% after rinsing
of the ceramic product with solvent. These values are
much lower than those observed for the SnTe prepared
by homoleptic Sn(II) tellurolates (3.05% C, 0.74% H).10d
X-ray powder diffraction (XRPD) confirmed that the
ceramic product was highly crystalline, phase-pure,
cubic tin telluride with an average crystallite size >
1000 nm, as determined using the Scherrer equation
(Figure 2). This is in contrast to the SnTe films produced
by Ganainy et al. via a thermal evaporation technique,
which contain a significant amorphous component in
addition to crystalline SnTe.2a
Tin telluride crystallizes in the cubic [NaCl] (rock salt)
structure, space group Fm3m. SnTe has a narrow
homogeneity range of 0.9 atom % at 50% Te, toward the
Te-rich side.17 At compositions of Sn1-xTex with x > 0.5,
the lattice parameter decreases relative to stoichiomet-
ric SnTe.17 Unit cell parameters of the powders produced
in this study lie within the range of previously reported
values10b,18a-e and are shown in Table 4. The unit cell
obtained in this study corresponds to approximately
Sn0.495Te0.505 according to an equation produced by
Brebrick relating unit cell length to stoichiometry for a
series of tin tellurides.18e X-ray powder diffraction data
for SnTe are given in Table 5.
PDF 8-48718a
PDF 25-46518b
PDF 46-121018c
Bis and Dixon18d
Brebrick18e
6.303
250.4
253.30
6.3272
6.32751(5)
6.312(2)
6.3017-6.3272
6.3171(85)
6.30954(33)
253.337(6)
251.5
250.24-253.30
252.098(9)
251.18
Boudjouk10b
this study
bond cleavage to form benzyl radicals followed by
dimerization.10a
Thermolysis at 400 °C for 5 h also produced highly
crystalline, phase-pure, cubic tin telluride. Ceramic
yields were 98% of theoretical, with the as-produced
powders having a carbon and hydrogen content of
<0.5%. The organic residue collected was 1,2-diphen-
ylethane. Total mass recovery was 85%.
The electron micrograph of a typical sample produced
at 275 °C shows individual SnTe grains, with typical
sizes ranging from 0.3 to 0.5 µm in diameter, and
morphologies of both cubes and mixtures of cubic and
octahedral forms (Figure 3).
Con clu sion s
2,2,4,4,6,6-Hexabenzylcyclotristannatellurane was pre-
pared in high yield by treating Bn2SnCl2 with aqueous
(NH4)2Te. In the solid state, molecules of (Bn2SnTe)3
form infinite molecular chains lying parallel to the
b-axis and superimposing along the a-axis.
Thermolysis of (Bn2SnTe)3 in an inert atmosphere
under mild conditions produces polycrystalline, cubic
SnTe in high yield and high purity. The SnTe crystals
possess cubic and cubooctahedral morphologies and
have a uniform size distribution of 0.3-0.5 µm in
diameter.
When care is taken to avoid prolonged exposure of
(Bn2SnTe)3 to light and air, no peaks attributable to
crystalline tin, tellurium, or the oxides of these elements
were observed in the pyrolysate. 1,2-Diphenylethane
was the only volatile product detected, suggesting that
the decomposition is dominated by homolytic Sn-C
Exp er im en ta l Section
Gen er a l Com m en ts. Flow pyrolyses were performed using
a Lindberg model 55035 programmable tube furnace, 36 cm
long and 3 cm in diameter with a 55 × 2.5 cm Vycor silica
glass tube placed inside. One end of the tube was fitted with
a one-holed septum connected to a source of dry nitrogen and
sealed with Parafilm. Nitrogen flow was monitored at the exit
of the tube by a mineral oil bubbler. The flow was set to
approximately 50 mL/min, and the tube was purged at this
rate for at least 0.5 h before introduction of the sample. The
sample to be pyrolyzed was placed in a Coors porcelain boat
(17) Sharma, R. C.; Chang, Y. A. Bull. Alloy Phase Diagrams 1986,
7, 72.
(18) (a) Natl. Bur. Stand.; PDF-2 File No. 8-487; International
Centre for Diffraction Data, Newtown Square, PA. (b) Brebrick, R. F.
PDF-2 File No. 25-0465; International Centre for Diffraction Data,
Newtown Square, PA. (c) Scheer, M.; McCarthy, G. J .; Seidler, D.;
Boudjouk, P.; PDF-2 File No. 46-1210; International Centre for
Diffraction Data, Newtown Square, PA. (d) Bis R. F.; Dixon, J . R. J .
Appl. Phys. 1969, 40, 1918. (e) Brebrick, R. F. J . Phys. Chem. Solids
1971, 32, 551.

2,2,4,4,6,6-Hexabenzylcyclotristannatellurane
Organometallics, Vol. 18, No. 22, 1999 4537
Ta ble 5. X-r a y P ow d er Diffr a ction Da ta for Sn Te.
hkl
D(obs), Å
D(calc),aÅ
D,18c
Å
2θ(obs), deg
2θ(calc),a deg
2θ,18c deg
I(obs),b %
I(calc),c %
I,18c
%
200
220
222
400
3.1547
2.2308
1.8214
1.5774
3.1548
2.2308
1.8214
1.5774
3.1630
2.2370
1.8266
1.5819
28.266
40.400
50.035
58.461
28.265
40.400
50.036
58.461
28.190
40.283
49.884
58.278
100
78
25
100
69
23
100
52
15
8
11
11
a
b
D-spacings and 2θ values calculated from the unit cell value obtained in this study using linear least-squares refinement. Intensities
given as peak heights for fixed divergence slit optics. c I(calc) calculated using Materials Data Inc. POWD software.
reflections, measured every 100 reflections, indicated a less
than 5% decrease in intensity over the course of data collection,
and hence, no correction was applied. All calculations were
performed using the Siemens software package SHELXTL-
Plus. The structure was solved by direct methods and succes-
sive interpretation of difference Fourier maps, followed by
least-squares refinement. All non-hydrogen atoms were refined
anisotropically. The hydrogen atoms were included in the
refinement in calculated positions using fixed isotropic pa-
rameters.
Syn th esis of (Bn 2Sn Te)3. Al powder (0.75 g, 28 mmol) and
Te powder (1.28 g, 10 mmol) were added to a 250 mL, two-
necked, round-bottomed flask containing a stirbar, N2 inlet, a
septum, and degassed distilled water (40 mL). Aqueous NH4-
OH (14 mL of a 5.0 M solution, 70 mmol) was added to this
mixture by syringe, forming a violet color in 10 min. The
mixture was stirred for 48 h, during which time the color
lightened. This mixture was transferred slowly (15 min) via
F igu r e 3. SEM micrograph (10 000× magnification; 15
cannula to an ether solution (110 mL) of Bn2SnCl2 (2.97 g, 8
mmol).10c The mixture turned dark brown and was stirred for
12 h at room temperature. Removal of the solids by filtration
under nitrogen produced a filtrate that formed two layers. The
organic layer was removed by cannula and the aqueous layer
extracted with ether (2 × 75 mL). The organic layers were
combined and evaporated to give (Bn2SnTe)3 (2.92 g, 85%) as
a bright yellow solid. (Bn2SnTe)3 turns gray upon prolonged
exposure to direct light or air. Recrystallization from ether
provides bright yellow crystals suitable for single-crystal X-ray
diffraction.
keV) of SnTe crystals from decomposition of (Bn2SnTe)3 at
275 °C for 10 h.
that had been oven-dried at 120 °C and cooled under a stream
of dry nitrogen in the tube furnace. Typical sample sizes were
500-800 mg. The crucible containing sample was placed in
the tube at the center of the furnace. For all samples, the oven
was programmed to ramp at a rate of 5 °C/min to 60 °C, held
at this temperature for 20 min, and ramped at a rate of 5 °C/
min to the final temperature. This temperature was main-
tained for 10 h for the reactions at 200 and 275 °C and for 5
h for the reactions at 400 °C. The products were cooled slowly
to room temperature under a constant flow of nitrogen. The
volatile products were condensed near the exit of the tube
using dry ice and were collected by washing the tube with
acetone and hexane.
Ch a r a cter iza tion . NMR spectra were obtained on a J EOL
GSX270 or GSX400 spectrometer at the following frequen-
cies: 1H (270.17 MHz), 13C (67.94 MHz), 119Sn (149.08 MHz),
125Te (126.08 MHz). Typical samples were prepared as 0.1-
0.2 M solutions in CDCl3. Chemical shifts are reported relative
to Me4Si for 1H and 13C, Me4Sn for 119Sn, and Me2Te for 125Te
and are in ppm. Infrared data were recorded as KBr pellets
on a Matheson Instruments 2020 Galaxy Series spectrometer
and are reported in cm-1. Melting points were taken on a
Thomas-Hoover capillary melting point apparatus and are
uncorrected. Combustion analyses were performed by Gal-
braith Laboratories, Knoxville, TN. Scanning electron micros-
copy was performed on plasma sputtered (Au) samples using
a J EOL J SM6300V instrument. X-ray powder diffraction
patterns were recorded from hexane slurry samples mounted
on glass slides using a Philips automated vertical diffracto-
meter with a graphite diffracted beam monochromator and
variable divergence slit and using Cu KR (λ ) 1.5418 Å)
radiation. NIST 660 lanthanum hexaboride (LaB6) was used
as an internal d-spacing standard.
1
Mp: 115-116 °C (dec). H NMR (CDCl3, 270 MHz): δ 2.91
(s, 12H, PhCH2), 6.95 (m, 12H, PhH), 7.10 (m, 6H, PhH), 7.21
(m, 12H, PhH). 13C NMR (CDCl3, 67.94 MHz): δ 27.44
(PhCH2), 124.98, 127.90, 128.77, 139.55 (Ar). 119Sn NMR
(CDCl3, 149.08 MHz): δ -148.54 [1J (119Sn-125Te) ) 1615 Hz].
125Te NMR (CDCl3, 126.08 MHz): δ -893.47 [1J (125Te-119Sn/
117Sn)] ) 1624/1554 Hz. IR (KBr, cm-1): 3075 w, 3021 w, 1597
s, 1489 vs, 1208 w, 1045 s, 754 vs, 694 vs. Anal. for C42H42
-
Sn3Te3: found (calc) C 38.94 (39.24), H 3.13 (3.29).
Ack n ow led gm en t. Financial support from the Of-
fice of Naval Research (Grant N00014-96-11271) and
the National Science Foundation (Grant OSR 9452892)
is gratefully acknowledged. M.R. is thankful for a North
Dakota EPSCoR Doctoral Dissertation Fellowship. We
also thank Kathy Iverson, Scott Payne, and Dr. Thomas
Freeman for obtaining the electron micrographs and Dr.
David A. Atwood for obtaining and solving the single-
crystal X-ray diffraction data.
Sin gle-Cr ysta l X-r a y Diffr a ction Exp er im en ta l De-
ta ils. Details of the crystal data and a summary of data
collection parameters for (Bn2SnTe)3 are given in Table 1. Data
were collected on a Siemens P4 diffractometer using graphite-
monochromatized Mo KR (0.71073 Å) radiation. The check
Su p p or tin g In for m a tion Ava ila ble: Crystallographic
tables, structure factor tables, and figures. This material is
available free of charge via the Internet at http://pubs.acs.org.
OM990506U