Convenient, room-temperature, amine-assisted routes to metal sulfides, selenides and tellurides

Article abstract of DOI:10.1039/a702833d

The reaction of elemental powders of Ag, Pb and Hg with S, Se or Te in n-butylamine for 12-72 h produced crystalline metal chalcogenides ME (M = Pb or Hg; E = S, Se or Te) and Ag₂E in good yield (>90%). The reactions of Cu with Se or Te in n-bu

Full text of DOI:10.1039/a702833d

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Convenient, room-temperature, amine-assisted routes to metal
sulfides, selenides and tellurides†
Vincent Dusastre, Bashe Omar, Ivan P. Parkin* and Graham A. Shaw
Chemistry Department, Christopher Ingold Laboratories, University College London,
20 Gordon Street, London, UK WC1H 0AJ
The reaction of elemental powders of Ag, Pb and Hg with S, Se or Te in n-butylamine for 12–72 h produced
crystalline metal chalcogenides ME (M = Pb or Hg; E = S, Se or Te) and Ag2E in good yield (>90%). The reactions
of Cu with Se or Te in n-butylamine gave crystalline Cu2ϪxSe and Cu0.64Te0.36, whilst the reaction of Cu or Ni with
sulfur under similar conditions produced an amorphous material that on heating to 250–300 ЊC for 2 h yielded
crystalline NiS and Cu2S. Products were analysed by Fourier-transform IR, Raman spectroscopy, scanning
electron microscopy with energy dispersive analysis by X-rays, powder X-ray diffraction and X-ray photoelectron
spectroscopy. The elemental reactions were also investigated in n-hexylamine, ethane-1,2-diamine, cyclohexane
and aqueous ammonia solution.
Late transition-metal and main-group metal sulfides, selenides
and tellurides have a number of commercial applications in
pigments, semiconductors and fluorescence devices.1 They are
traditionally made by elemental combination reactions at high
temperatures for prolonged times;2 these reactions typically
produce the thermodynamic products with little control in
stoichiometry or crystallinity.
with some elemental metals in liquid ammonia at room
temperature in a pressure vessel (ca. 7 atm) produced amorph-
ous and crystalline metal sulfides, equations (1) and (2). The
M (s) ϩ S (NH3) → MS (M = Zn, Cd, Hg or Pb) (1)
2Ag (s) ϩ S (NH3) → Ag2S
(2)
Many metal chalcogenides are found in nature as minerals.1
A wide range of techniques has been developed to synthesize
metal chalcogenides with control of micro structure and par-
ticle size. These developments include Self propagating High
temperature Synthesis (SHS),3 molecular precursor reactions
(involving either the thermal decomposition of compounds
containing M᎐S or M᎐Se bonds4 or H2E as the chalcogen
source5), and the use of templating agents that utilise restrictive
environments6 (zeolites and micelles). Much of this work has
been focused on the formation of controllable nanoparticulate
chalcogenides (especially PbS, PbSe, CdS and CdSe7). These
nanoparticulates exhibit quantisation effects that have a
potential use for optical signal processors and switches.8 Such
materials have been prepared using H2E (E = S or Se) by aerosol
pyrolysis decomposition at elevated temperatures,9 arrested
precipitation of micelles10 and trapping within a polymer mat-
rix11 or glass.12 Single-source molecular precursors have also
proved to be successful using moderately high temperatures13
(250 ЊC). Other work has shown that Solid State Metathesis
(SSM) reactions can be utilised for the formation of metal
chalcogenides by treating alkali-metal sulfides with metal hal-
ides.14 Most of this work involves the use of high temperatures
either from a conventional oven or, in the case of SSM and SHS
reactions, from the inherent exothermicity of the reaction.
The most straightforward way of preparing metal sulfides
would be the direct combination of the elements at room
temperature and pressure. Rauchfuss and co-workers15 have
shown that it is possible to combine zinc and sulfur by refluxing
the elements in strongly co-ordinating solvents, such as pyridine
(py), to form complexes of the form M(S6)(py)2. These com-
plexes can be thermally decomposed 15 at 500 ЊC to form the
binary chalcogenide ZnS. Similar low-energy approaches,
involving [Cu(en)2]2ϩ (en = ethane-1,2-diamine) and thiourea,
have enabled essentially amorphous CuS to be made at room
temperature.16
reactions of lead and silver produced essentially crystalline
metal sulfides, whilst the other reactions produced amorphous
sulfides that could be crystallised by heating at 300 ЊC for 2 h.
These reactions were facilitated by the use of liquid ammonia,
which dissolved the sulfur giving coloured reactive solutions.
Sulfur also dissolves in amine solutions to form a variety of
different colours (red, orange, green) that change with time and
cannot be accounted for on the basis of simple dissolution of
the S8 ring.18 This led us to investigate whether these sulfur–
amine solutions could also react with elemental metals.
In this paper we report the convenient preparation of
amorphous and crystalline metal chalcogenides from one-step
elemental reactions in n-butylamine.
Results and Discussion
The reactions of Ag, Pb, Cu and Hg with S, Se or Te in
n-butylamine at room temperature for 24 h produces crystal-
line metal chalcogenides Ag2E, PbE, HgE (E = S, Se or Te) and
Cu2ϪxSe, Cu0.64Te0.36, equations (3)–(5), in virtually quantitative
2Ag ϩ E (amine) → Ag2E (E = S, Se or Te) (3)
M ϩ E (amine) → ME (M = Pb or Hg;
E = S, Se or Te) (4)
(2 Ϫ x)Cu ϩ Se (amine) → Cu2ϪxSe
2Cu ϩ Te (amine) → Cu0.64Te0.36
(5)
(6)
yield (Table 1). The metal chalcogenides were characterised by
Fourier-transform IR and Raman spectroscopy which showed
broad absorption bands in the region from 600 to 200 cmϪ1
,
depending on the sample. The vibrational spectra invariably
matched those of authentic samples. No IR stretches corre-
sponding to N᎐H vibrations were observed. Further, micro-
analysis showed negligible amounts of C, H and N (less than
In a previous paper 17 we reported that the reaction of sulfur
† Non-SI units employed: atm = 101 325 Pa, eV ≈ 1.60 × 10Ϫ19 J.
J. Chem. Soc., Dalton Trans., 1997, Pages 3505–3508
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Table 1 Summary of experimental data, including reaction times, material colour, the identity of the phases comprising the reaction product before
and after thermolysis at 523–573 K (as determined by X-ray powder diffraction studies) and, where possible, a comparison of the lattice parameters
of these phases with those obtained from the literature. Phases in square brackets were traces (typically less than 3%)
Lattice parameters (±0.02 Å) (lit. values
Thermolysed XRD
pattern
(250–300 ЊC, 2)
in parentheses)
Ratio of
elements
Colour of
material
Reaction
time/h
Unthermolysed
XRD pattern
a
b
c
Ag:S 2:1
Ag:Se 2:1
Ag:Te 2:1
Hg:S 1:1
Hg:Se 1:1
Hg:Te 1:1
Pb :S 1:1
Pb :Se 1:1
Pb :Te 1:1
Cu :S 1:1
Cu :Se 1:1
Cu :Te 1:1
Black
Black
Black
Black
Black
Black
Black
Black
Black
Black
Black
Black
48
48
48
24
24
24
48
48
48
24
12
72
Ag2S (acanthite)
Ag2Se (naumannite)
Ag2Te (hessite), [Ag]
HgS (metacinnabar)
HgSe (tiemannite)
HgTe (coloradoite)
PbS (galena), [Pb]
PbSe (clausthalite)
PbTe (altaite)
Ag2S (acanthite)
Ag2Se (naumannite)
Ag2Te (hessite)
HgS (metacinnabar)
HgSe (tiemannite)
HgTe (coloradoite)
PbS (galena)
PbSe (clausthalite)
PbTe (altaite)
Cu2S (chalcocite) ϩ S
Cu2ϪxSe (berzelianite)
4.48 (4.46)
4.33 (4.33)
8.07 (8.09)
5.85 (5.85)
6.07 (6.07)
6.45 (6.45)
5.93 (5.93)
6.12 (6.12)
6.45 (6.46)
—
5.74 (5.77)
5.10 (—)
—
—
—
4.48 (4.46)
7.06 (7.06)
4.47 (4.47)
5.85 (5.85)
6.07 (6.07)
6.45 (6.45)
5.93 (5.93)
6.12 (6.12)
6.45 (6.46)
—
5.74 (5.77)
5.10 (—)
—
—
—
4.48 (4.46)
7.76 (7.76)
8.94 (8.96)
5.85 (5.85)
6.07 (6.07)
6.47 (6.45)
5.93 (5.93)
6.12 (6.12)
6.45 (6.46)
—
5.74 (5.77)
4.17 (—)
—
—
—
Amorphous
Cu2ϪxSe (berzelianite)
Cu0.64Te0.36
[Cu4Te3]
Cu2ϪxTe (rickardite)
Cu2ϪxTe (weissite)
Amorphous
Amorphous
Amorphous
NiS (millerite)
Amorphous ϩ Ni
Amorphous ϩ Ni
Amorphous, Sb
Amorphous
Fe:S 1:1
Fe:Se 1:1
Fe:Te 1:1
Ni:S 1:1
Ni:Se 1:1
Ni:Te 1:1
Sb :S 2:5
As:S 2:5
Black
Black
Black
Black
Black
Black
Red
60
60
60
36
36
36
60
24
Amorphous ϩ Fe
Amorphous ϩ Fe, Se
Amorphous ϩ Fe, Te
Amorphous ϩ Ni
Amorphous ϩ Ni
Amorphous ϩ Ni
Amorphous, Sb
—
—
—
—
—
—
3.43 (3.42)
—
—
3.43 (3.42)
—
—
3.43 (3.42)
—
—
Yellow
Amorphous
—
—
—
0.3%), thus indicating that amine is not bound up in the prod-
uct. Scanning electron microscopy (SEM) revealed small irregu-
larly shaped aggregates (typically of size 3–8 µm), whilst energy
dispersive analysis by X-rays (EDAX) commonly showed only
the metal and chalcogenide to be present and in the expected
elemental ratios across many surface spots (of width 1 µm). In
some samples (Table 1) small regions of unreacted metal were
observed (<5%). The X-ray photoelectron spectra of the solid
from the reaction of silver and tellurium in n-butylamine
showed the elements with a stoichiometry of Ag2Te1.03(5). The
5
binding energy values of 367.6 eV for Ag 3d and 571.8 eV for
2
¯
5
Te 3d are consistent with the formation of silver telluride
2
¯
(Ag2Te).19
The X-ray powder diffraction (XRD) patterns of the prod-
ucts produced from the reaction of Ag, Pb and Hg with chalco-
gens in n-butylamine are summarised in Table 1. These showed
the formation of crystalline metal chalcogenide powders that
indexed well and gave cell parameters identical to those in
the literature.20 Crystallite sizes determined by the Scherrer
equation 21 were of the order of 300–700 Å. In all of these
reactions a single-phase metal chalcogenide product was
obtained with the exception of the reactions of Ag with Te and
Pb with S where a small trace of unchanged Pb and Ag (ca. 2%)
was detected. On thermolysis of these powders the trace of
metal disappears from the XRD pattern, presumably because
of either reaction with a small amount of X-ray amorphous
chalcogen or by incorporation within the metal chalcogenide
phase.
Treatment of copper with sulfur in n-butylamine produced a
black X-ray amorphous material that on thermolysis produced
crystalline Cu2S (as assessed by powder X-ray diffraction).
Reaction of selenium and tellurium with copper in n-butyl-
amine also produced black crystalline solids, Cu2ϪxSe (berzelian-
ite) (Fig. 1) and predominantly copper telluride Cu0.64Te0.36
(with a trace of Cu4Te3). It should be noted that the elemental
ratio of the starting materials for the copper reactions was 1:1
and that the preferred products were effectively 2:1. The excess
of chalcogenide in the reaction was removed by washing with
CS2. Combination of the elements in the 2:1 ratio also pro-
duces ‘Cu2E’ but without the need of CS2 washing.
Fig. 1 The XRD pattern (top) obtained for the reaction product of
copper with selenium (Cu2ϪxSe). The data base standard for Cu2ϪxSe
(berzelianite) is shown below
at room temperature did produce a slight colour change to the
solid. However, both X-ray powder diffraction studies and
EDAX analysis of the material showed the presence of the
unchanged elements. Only in the case of Ni with sulfur, heating
the material at 250–300 ЊC for 2 h showed the formation of a
crystalline chalcogenide (NiS, millerite), although the thermo-
lysed product of the iron reaction showed no unreacted ele-
ments. Arsenic reacted with sulfur in n-butylamine to afford a
yellow solid that was amorphous to X-rays even after heating
at 823 K for 2 h. The EDAX analysis showed the correct ratios
of arsenic to sulfur, i.e. the major product from the reaction
(>90%) was arsenic sulfide (As2S3). Similar analysis showed
that the reaction between antimony and sulfur produced a red
solid on the surface of unreacted antimony, whose elemental
composition suggests the formation of Sb2S3. In both the reac-
tions of As and Sb the initial starting material ratios were 2:5
and not 2:3, indicating a preference for the lower-oxidation-
state sulfides of these elements; the excess of unreacted sulfur
was removed from the product by trituration with CS2. No reac-
tion was observed between Sn or Cd with sulfur in n-butyl-
amine even after refluxing the solutions both conventionally
(12 h) and by microwave irradiation (2 h).
The reaction of Fe, Sb or Ni with S, Se or Te in n-butylamine
Reactions were also investigated between Ag, Pb and Hg with
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J. Chem. Soc., Dalton Trans., 1997, Pages 3505–3508

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the chalcogens at room temperature in a variety of solvents.
Although these proceeded in n-hexylamine, the reactions were
significantly slower (requiring about 1 week to go to comple-
tion). The same crystalline phases were observed as for the n-
butylamine reactions. The use of cyclohexane or ethane-1,2-
diamine as a solvent did not promote formation of a crystalline
metal sulfide, even after 14 d. Use of aqueous ammonia as
solvent for the reaction of Pb and S did facilitate the formation
of crystalline PbS within 48 h. However, the product was also
contaminated with significant quantities of metal oxide and
unchanged metal (ca. 75% in total, as determined by EDAX).
There was no observed reaction between sulfur and Hg (or Ag)
in aqueous ammonia after 48 h.
Sulfur reacts with aliphatic primary and secondary amines to
form coloured solutions that have been attributed to the step-
wise nucleophilic attack of the S8 rings by the amine, resulting
in first the formation of N,NЈ-polythiobisamines (with the in
situ release of H2S), and then the progressive attack of the ali-
phatic amine by hydrogen sulfide to yield amine polysulfides.18
These new sulfur–amine species coexist and are uniquely
coloured, but contain long straight chains of sulfur that are
inherently less stable than the original S8 rings. Hodgson et al.18
suggested that these species would therefore undergo sub-
sequent homolytic scission to form sulfur-based radicals, there-
by achieving a degree of resonance stability. It is possible that
these radicals are involved in the reaction with the elemental
metals. Selenium and tellurium are insoluble in n-butylamine
yet, as stated above, also react with elemental Ag, Cu, Pb and
Hg. Consequently, the amine solvent may play a role in activ-
ating the metal or chalcogenide surface, effectively allowing
good contact between the elements. In any case, the reactions
of selenium and tellurium appear to be solid-state reactions,
although the presence of a solvated species of extremely low
concentration cannot be ruled out. The time taken for complete
reaction (Table 1) suggests that the rate of elemental solid-state
diffusion is excellent (especially since a crystalline material is
produced). It might be expected that the rates of reaction of
sulfur with Ag or Hg would be faster than for selenium and
tellurium, since the sulfur fully dissolves in the amine. However,
competitive reactions between either of these elements and
sulfur/selenium in n-butylamine resulted in the preferential
formation of Ag2Se (>95%) and HgSe (>95% as determined by
EDAX/XRD). It was found difficult to form solid solutions of
the form MSxSey.
has been devoted to the preparation of nanoparticulate
materials.6–12 These can be roughly divided into two main areas:
synthesis from the gas phase,9 invariably by the use of molecu-
lar precursors, and synthesis from solution either via autoclave
or refluxing solvents.12 Both of these methods employ the use of
toxic H2E as the chalcogenide source. These syntheses do pro-
duce chalcogenides of high quality, often with very precise
and controlled particle sizes, and distributions that are usually
stabilised in some polymer matrix,11 micelle10 or framework
structure. The elemental reactions studied here are arguably
more straightforward than many of these new methods, in that
they do not require elevated temperatures, special reaction
vessels, precursor synthesis or the use of H2E. Amine-promoted
elemental reactions do as yet have little control over the
materials crystallinity, the products from the reactions being
either amorphous (Cu2S) or very crystalline (PbSe) with seem-
ingly nothing in between. Significant differences in the reactiv-
ity are observed between the chalcogens and metallic elements
in ammonia and n-butylamine solutions. This is as yet
unexplained, as too is the reason why the reactions occur more
slowly in n-hexylamine and not at all in cyclohexane. It is
known that some chalcophilic elements will react on contact
with chalcogens in the absence of a solvent at room temper-
ature. In our hands the products from the reaction of mercury
with sulfur (cinnabar and metacinnabar) were not crystalline,
and the reaction stops after an initial period leaving only partly
coated reacting particles. In order to test the rate of solid-state
reaction, discs of silver metal and elemental sulfur were pressed
together. The silver disc was seen gradually to darken with the
formation of crystalline acanthite (Ag2S). The reaction pro-
gressed from the elemental boundary into the silver disc to a
depth of 0.5–1 mm after a month. It is probable that in a stirred
n-butylamine solution the formed metal chalcogenides are
cleaned from the surface of the reacting elements, effectively
regenerating clean surfaces for subsequent reaction. Perhaps
liquid ammonia at room temperature (7 atm) is more aggressive
at removing partly formed metal chalcogenide from the surface
of a metal than is n-butylamine, and thus it can promote ele-
mental reactions between a wider range of elements.
Conclusion
The reactions between some elemental metals (Ag, Cu, Hg and
Pb) and the chalcogens in n-butylamine for 12–60 h produce
single-phase crystalline metal chalcogenides in good yield. The
reactions are easy to perform, do not require any precursor
synthesis or the use of H2E (E = S, Se or Te) and afford perhaps
the simplest means of preparing a selected range of main-group
and late transition-metal chalcogenides. The reactions with Se
and Te seem to proceed via a solid-state reaction, possibly with
the n-butylamine solvent helping to remove partly reacted
material and encouraging fresh surfaces for the reaction.
Previously17 we reported the reactivity between elemental
metals and chalcogenides in liquid ammonia. Similar results are
obtained here, with comparable phases being observed but for
two notable exceptions. First, when conducted in ammonia the
reaction of sulfur with mercury gave an amorphous powder
identified as a mixture of cinnabar and metacinnabar (after
heating to 250 ЊC for 2 h). Yet a single crystalline phase of HgS
(metacinnabar) was produced in n-butylamine. Secondly, reac-
tions of copper with Se and Te in n-butylamine produced pre-
dominantly single-phase materials, whilst in liquid ammonia a
mixture of phases was observed that included significant
amounts of CuTe and CuSe. Elemental reactions in liquid
ammonia have a greater scope in that Zn, Cd and Sn all react
to form amorphous chalcogenides (with crystalline materials
being obtained on heating these powders at 250–300 ЊC for 2 h).
In n-butylamine no reaction was observed for these elements,
even at reflux, except in the case of Zn and S where the form-
ation of 5–10% amorphous ZnS was observed on the surface of
the zinc after 1 week. In the cases where a reaction did occur in
n-butylamine at room temperature the phases of the metal
chalcogenides observed were invariably the same as the most
common mineral forms of these species. The materials formed
with copper and silver were formally MI d10, with HgII d10, and
with PbII d10s2. This is in line with the known preferred oxid-
ation states of these elements in metal chalcogenides.1
Experimental
All reagents were of 99.9% purity or better from Aldrich Chem-
ical Co. and used without further purification. Manipulations
and weighings were carried out in air. Reactions were carried
out in 40 cm3 sample tubes. X-Ray powder diffraction patterns
were determined on a Siemens D5000 transmission powder
diffractometer using germanium-monochromated Cu-Kα1
radiation (λ = 1.504 Å); SEM/EDAX was performed on a
JEOL JSM820 microscope equipped with a Kevex Quantum
detector Delta 4 and a Hitachi S-570 scanning electron micro-
scope. Electron probe analysis were conducted on a JEOL
EMA using polished samples and compared to metal and sulfur
standards. X-Ray photoelectron spectra were recorded with a
VG ESCALAB 220i XL instrument using focused (300 µm
spot) monochromatic Al-Kα radiation at a pass energy of 20
eV. Scans were acquired with steps of 50 meV. A flood gun was
Much current research on metal chalcogenide synthesis
J. Chem. Soc., Dalton Trans., 1997, Pages 3505–3508
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used to control charging and the binding energies were refer-
enced to an adventitious C 1s peak at 284.8 eV. Infrared spectra
were recorded on Nicolet 205 spectrometer using KBr pressed
discs, Raman spectra on a Dilor XY spectrometer [the 514.53
nm line of an argon laser (50 mW) was the excitation source; slit
width 300 µm]. Magnetic moment measurements were made on
a Johnson Matthey balance. Powder X-ray diffraction patterns
were indexed using TREOR or METRIC-LS programmes, and
referenced against an external data base.19
Attempts at encouraging reaction between S and Sn or Cd by
refluxing (12 h) the n-butylamine by conventional means, as
well as microwave irradiation (2 h), failed to produce an identi-
fiable sulfide product. Reactions between S with Ag or Pb in
n-hexylamine did proceed to form the metal chalcogenide but
over 7 d.
References
1 N. N. Greenwood and E. A. Earnshaw, Chemistry of the Elements,
Pergamon, Oxford, 1990, p. 1403; M. Farnsworth and C. Kline, Zinc
Chemicals, Their Properties and Applications, International Lead
and Zinc Research Organisation, New York, 1968; G. Q. Yeo,
H. S. Shen, E. D. Honig, R. Kershaw, K. Dwight and A. Wold, Solid
State Ionics, 1987, 24, 249; G. Nickless, Inorganic Chemistry of
Sulphur, Elsevier, London, 1968, p. 670.
Reactions of Hg, Ag and Pb with sulfur, selenium and tellurium
in n-butylamine
The same general reaction scale and procedure was adopted for
all the reactions exemplified here for PbS.
Powdered lead metal (0.612 g, 3.06 mmol) and sulfur (0.098
g, 3.06 mmol) were added to n-butylamine (20 cm3) at room
temperature. The vessel was stoppered and the mixture mag-
netically stirred for 48 h. The sulfur dissolved in the n-butyl-
amine to give a red solution which reacted with the powdered
lead to produce a black solid. The lead was not observed to
dissolve into the amine solution but did become used up during
the course of the reaction. The black solid was collected by
decanting off the amine, and washed with acetone (20 cm3) and
CS2 (2 × 20 cm3). Yield of PbS 0.659 g, 2.74 mmol (90%).
All the chalcogenides of Hg, Ag and Pb were analysed by
X-ray powder diffraction (Table 1), Fourier-transform IR and
Raman spectroscopy, SEM/EDAX and magnetic moment
measurements. The metal sulfides typically showed a strong
absorption band at 450–300 cmϪ1 in the IR and Raman spectra
corresponding to an M᎐S stretch. The chalcogenide powders of
Hg and Pb were diamagnetic. Microanalysis: for Ag2Se, C, 0.29;
H, 0.15; N, 0.08; for PbTe, C, 0.27; H, 0.10; N, 0.02%.
2 R. Coustal, J. Chim. Phys., 1958, 38, 277.
3 H. C. Yi and J. J. Moore, J. Mater. Sci., 1990, 25, 1159.
4 D. M. Wilhemy and E. Matijevic, J. Chem. Soc., Faraday Trans. 1,
1984, 563.
5 N. L. Pickett, D. F. Forster and D. J. Cole Hamilton, J. Mater.
Chem., 1996, 6, 507.
6 Y. Wang and N. Herron, J. Phys. Chem., 1987, 91, 257.
7 M. Stoev and A. Katerski, Chem. Mater., 1996, 6, 377.
8 L. Buis, Appl. Phys. A, 1991, 53, 465.
9 O. V. Salata, P. J. Dobson, P. J. Hull and J. L. Hutchens, Adv. Mater.,
1994, 6, 772; X. K. Zhao, L. D. McCormick and J. H. Fender,
Adv. Mater., 1992, 4, 93.
10 A. R. Korton, R. Hull, R. L. Opita, M. G. Bawerdi, M. L.
Steigerwold, P. J. Carroll and L. E. Brus, J. Am. Chem. Soc., 1990,
112, 1327.
11 V. Sankaran, C. C. Cummings, R. R. Schrock, R. E. Cohen and
R. J. Silby, J. Am. Chem. Soc., 1990, 112, 6858; Y. Tias, C. Wu,
N. Kotov and J. H. Fendler, Adv. Mater., 1994, 6, 959.
12 J. C. Luong, Superlattice Microstruct., 1988, 4, 385.
13 T. Trindade and P. O’Brien, Adv. Mater., 1996, 8, 161.
14 I. P. Parkin, Chem. Soc. Rev., 1996, 25, 199.
15 S. Dev, E. Ramli, T. B. Rauchfuss and S. R. Wilson, Inorg. Chem.,
1991, 30, 2514; P. P. Paul, T. B. Rauchfuss and S. R. Wilson, J. Am.
Chem. Soc., 1993, 115, 3316; E. Ramli, T. B. Rauchfuss and
C. L. Stern, J. Am. Chem. Soc., 1990, 112, 4043.
16 H. Grijavala, M. Inoue, S. Boggavarapu and P. Calvert, J. Mater.
Chem., 1996, 6, 1157.
17 G. Henshaw, I. P. Parkin and G. A. Shaw, J. Chem. Soc., Dalton
Trans., 1997, 231; Chem. Commun., 1996, 1095.
18 W. G. Hodgson, S. A. Buckler and G. M. Peters, J. Am. Chem. Soc.,
1962, 84, 2085.
19 C. D. Wagner, in Practical Surface Analysis, eds. D. Briggs and
M. Peah, 2nd edn., Wiley, Chichester, 1990, vol. 1.
20 PDF-2 database on CD-ROM, International Centre for Diffraction
Data, Swarthmore, PA, 1990.
21 H. P. Klug and L. E. Alexander, X-Ray Diffraction Procedure for
Polycrystalline and Amorphous Materials, 2nd edn., Wiley, New
York, 1974.
Reaction of Cu, Sb, As, Fe, Ni, Cu and Zn with S, Se and Te in
n-butylamine
The same general reaction scale and procedure was adopted as
outlined above for PbS and summarised in Table 1. Reaction of
Cu with S produced an amorphous black material, whilst with
Se and tellurium crystalline Cu2ϪxSe and Cu0.64Te0.36 were
produced. The reactions of As and Sb with S in n-butylamine
produced yellow and red solids respectively which were col-
lected by decanting off the solvent, triturating with CS2 (40
cm3) and filtering. The materials were both X-ray amorphous
before and after thermolysis (523–823 K, 2 h). Reaction of
iron and nickel with S, Se and Te in n-butylamine produced
black powders that were X-ray amorphous before and after
thermolysis, with the exception of Ni with S which after therm-
olysis showed crystalline NiS (millerite). Reaction of Zn with S
in n-butylamine did produce a small amount of white solid
after 7 d, which was identified by EDAX as ZnS. This reaction
only went, at best, to a 10% yield.
Received 25th April 1997; Paper 7/02833D
3508
J. Chem. Soc., Dalton Trans., 1997, Pages 3505–3508