Thio-, seleno- and telluro-ether complexes of aluminium(iii) halides: Synthesis, structures and properties

Article abstract of DOI:10.1039/c3dt52991f

The reaction of AlCl₃ with Me₂E (E = S, Se or Te) or ⁿBu₂E (E = Se or Te) in CH₂Cl₂ under rigorously anhydrous conditions gave the pseudo-tetrahedral complexes [AlCl₃(R₂E)]. The [AlX₃(Me₂E)] (X = Br or I, E = S; X = Br, E = Te) were made from toluene solution since attempted syntheses in CH₂Cl₂ resulted in substantial chloride incorporation. The synthesis of [(AlCl₃)₂{o-C ₆H₄(CH₂SEt)₂}], in which the ligand bridges two tetrahedral aluminium centres, and of the six-coordinate trans-[AlX₂{MeE(CH₂)₂EMe}₂][AlX ₄] (X = Cl or Br, E = S, and X = Cl, E = Se) and cis-[AlI ₂{MeS(CH₂)₂SMe}₂][AlI₄] are reported. The tripodal thioether forms [AlCl₃{MeC(CH ₂SMe)₃}], which is a chain polymer with κ²-coordinated ligand and a tbp arrangement at Al(iii). Chalcogenoether macrocycle complexes [AlCl₃([9]aneS₃)], [AlCl₂([14]aneS₄)][AlCl₄] and [AlCl ₂([16]aneSe₄)] [AlCl₄] are also described. All complexes were characterised by microanalysis, IR and multinuclear NMR ( ¹H, ²⁷Al, ⁷⁷Se or ¹²⁵Te) spectroscopy as appropriate. In CH₂Cl₂ solution [AlCl ₃(Me₂S)] with added Me₂S forms [AlCl ₃(Me₂S)₂], and the [AlX₂{MeS(CH ₂)₂SMe}₂][AlX₄] exist as mixtures of cis and trans isomers which undergo rapid exchange at ambient temperatures. X-Ray crystal structures are reported for [AlCl₃(Me₂Se], [AlX₃(Me₂Te)] (X = Cl or Br), trans-[AlCl ₂{MeE(CH₂)₂EMe}₂][AlCl₄] (E = S or Se), cis-[AlI₂{MeS(CH₂)₂SMe} ₂][AlI₄], [AlCl₃{MeC(CH₂SMe) ₃}], and for the sulfonium salt [Me₂SH][AlCl₄]. The aluminium halide chalcogenoether chemistry is compared with the corresponding gallium and indium systems, and the relative Lewis acidities of the metals discussed. Attempts to use [AlCl₃(ⁿBu ₂E)] (E = Se or Te) as LPCVD reagents to form aluminium chalcogenide films were unsuccessful.

Full text of DOI:10.1039/c3dt52991f

Dalton
Transactions
View Article Online
View Journal | View Issue
PAPER
Thio-, seleno- and telluro-ether complexes of
aluminium(III) halides: synthesis, structures and
properties†
Cite this: Dalton Trans., 2014, 43,
3637
Kathryn George,a Marek Jura,b William Levason,*a Mark E. Lighta and Gillian Reida
The reaction of AlCl3 with Me2E (E = S, Se or Te) or nBu2E (E = Se or Te) in CH2Cl2 under rigorously anhy-
drous conditions gave the pseudo-tetrahedral complexes [AlCl3(R2E)]. The [AlX3(Me2E)] (X = Br or I, E = S;
X = Br, E = Te) were made from toluene solution since attempted syntheses in CH2Cl2 resulted in sub-
stantial chloride incorporation. The synthesis of [(AlCl3)2{o-C6H4(CH2SEt)2}], in which the ligand bridges
two tetrahedral aluminium centres, and of the six-coordinate trans-[AlX2{MeE(CH2)2EMe}2][AlX4] (X = Cl
or Br, E = S, and X = Cl, E = Se) and cis-[AlI2{MeS(CH2)2SMe}2][AlI4] are reported. The tripodal thioether
forms [AlCl3{MeC(CH2SMe)3}], which is a chain polymer with κ2-coordinated ligand and a tbp arrange-
ment at Al(III). Chalcogenoether macrocycle complexes [AlCl3([9]aneS3)], [AlCl2([14]aneS4)][AlCl4] and
[AlCl2([16]aneSe4)] [AlCl4] are also described. All complexes were characterised by microanalysis, IR and
multinuclear NMR (1H, 27Al, 77Se or 125Te) spectroscopy as appropriate. In CH2Cl2 solution [AlCl3(Me2S)]
with added Me2S forms [AlCl3(Me2S)2], and the [AlX2{MeS(CH2)2SMe}2][AlX4] exist as mixtures of cis and
trans isomers which undergo rapid exchange at ambient temperatures. X-Ray crystal structures are
reported for [AlCl3(Me2Se], [AlX3(Me2Te)] (X = Cl or Br), trans-[AlCl2{MeE(CH2)2EMe}2][AlCl4] (E = S or Se),
cis-[AlI2{MeS(CH2)2SMe}2][AlI4], [AlCl3{MeC(CH2SMe)3}], and for the sulfonium salt [Me2SH][AlCl4]. The
aluminium halide chalcogenoether chemistry is compared with the corresponding gallium and indium
systems, and the relative Lewis acidities of the metals discussed. Attempts to use [AlCl3(nBu2E)] (E = Se or
Te) as LPCVD reagents to form aluminium chalcogenide films were unsuccessful.
Received 23rd October 2013,
Accepted 6th January 2014
DOI: 10.1039/c3dt52991f
www.rsc.org/dalton
that reported phase diagrams, IR and H NMR spectra,4–6 and
1
Introduction
several studies of solution enthalpies.7 The only crystallogra-
Aluminium chloride is widely used both in the laboratory and phically characterised example of a neutral thioether co-
industry as a Friedel–Crafts catalyst for alkylation and acylation ordinated to AlX3 is the recently reported8 [AlCl3(thianthrene)],
reactions, and also catalyses condensation, isomerisation and although there are a few AlMe3 complexes with thiamacro-
polymerisation reactions.1 The reactions depend upon the cycles.9 There are no reports of studies with telluroethers, and
strong Lewis acidity which produces incipient carbocations in the single complex of a selenium ligand is [AlCl3(selenoxan)],
combination with [AlCl4]− anions. Aluminium bromide and characterised only by microanalysis.10
iodide promote similar chemistry and have some niche appli-
Recent studies of gallium(III) halides GaX3 (X = Cl, Br or I)
cations.1 The strong Lewis acidity of these three halides has with chalcogenoethers have established that most contain
resulted in the characterisation of very many adducts, mostly pseudo-tetrahedral gallium centres [GaX3L] (L = Me2S, Me2Se,
with N- or O-centres in solvents or donor ligands.2 In contrast, Me2Te, etc.) or dinuclear [X3Ga(μ-L–L)GaX3] (L–L
= RS-
AlF3 is an inert polymer which forms few complexes.3 Surpris- (CH2)2SR, MeSe(CH2)2SeMe, MeTe(CH2)3TeMe etc.).11–14
ingly little is known about AlX3 adducts of chalcogenoethers, Higher coordination numbers are rare in the gallium systems,
which are limited to early studies of adducts with Me2S or Et2S but found with the thia-macrocycle [14]aneS4,‡ which binds
exodentate via two sulfur centres, affording the chain polymer
[GaCl3([14]aneS4)] with a trigonal bipyramidal geometry.15 The
larger rings [16]aneS4 and [16]aneSe4 form octahedral cations
aSchool of Chemistry, University of Southampton, Highfield, Southampton SO17 1BJ,
UK. E-mail: wxl@soton.ac.uk
bISIS, STFC, Harwell Innovation Campus, Didcot, Oxfordshire OX11 0QX, UK
†Electronic supplementary information (ESI) available: Structural data on
[o-C6H4CH2Se(Me)CH2][AlCl4], [AlCl2([14]aneS4)][AlCl4] and [tBuTe(CH2)3Te(tBu)-
Te(CH2)3TetBu][AlCl4]. CCDC 966342–966353. For ESI and crystallographic data
in CIF or other electronic format see DOI: 10.1039/c3dt52991f
‡[14]aneS4 = 1,4,8,11-tetrathiacyclotetradecane, [16]aneSe4 = 1,5,9,13-tetraselana-
cyclohexadecane, [16]aneS4 = 1,5,9,13-tetrathiacyclohexadecane, [9]aneS3 = 1,4,7-
trithiacyclononane.
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 3637–3648 | 3637

View Article Online
Paper
Dalton Transactions
trans-[GaCl2(macrocycle)][GaCl4].15 The larger indium centre into the products, and the heavier halides are best made from
forms 4-, 5- or 6-coordinate complexes of types [InX3(R2E)] (E = anhydrous toluene solution. Similar observations were made
S, Se or Te), [InX3(R2S)2], [In2X6{RE(CH2)2ER2}2], trans- by Burford et al.19 in AlX3/R3PO/CH2Cl2 systems. However, the
[InX2{RE(CH2)2ER2}2][InX4],11–16
and trans-[InCl2{[16]aneSe4}][InCl4].15,16
cis-[InCl2{[14]aneS4}][InCl4] pre-isolated pure [AlX3L] (X = Br or I) react only slowly with
CH2Cl2 (or CD2Cl2), which remains the NMR solvent of choice,
We have recently reported that [GaCl3(nBu2E)] (E = Se or Te) as non-coordinating and useable down to 180 K. The reactivity
or [GaCl3{μ-nBuE(CH2)nEnBu)GaCl3] are effective single source of AlCl3 in CH2Cl2 has been ascribed to the formation of the
precursors for low pressure chemical vapour deposition intermediate carbenium ion [CH2Cl][AlCl4],8,20 and in previous
(LPCVD) of Ga2E3 thin films, and that preferential deposition studies of GaCl3 complexes of thioethers we observed the for-
occurs onto TiN in photolithographically patterned SiO2/TiN mation of [o-C6H4(SMeCH2Cl)2][GaCl4]2 when [(GaCl3)2{μ-o-
substrates.17 Here we report systematic studies of the reactions C6H4(SMe)2}] is allowed to stand in CH2Cl2 solution for several
of AlX3 (X = Cl, Br or I) with a range of thio-, seleno- and days.13 Cleavage of C–Se or C–Te bonds is also observed, e.g.
telluro-ethers, detailed spectroscopic and structural data, and the formation of the selenonium cation in [o-C6H4(CH2)2SeMe]-
comparisons with their gallium and indium analogues. We [GaCl4] from o-C6H4(CH2SeMe)2.12 In the aluminium systems
also explored whether selected complexes would function as many of the complexes degrade on standing in solution at
CVD reagents for deposition of aluminium chalcogenide films. ambient temperatures (below), hence rapid isolation of the
complexes from solution is advisable. Decomposition in solu-
tion is much slower at low temperatures, permitting growth of
X-ray quality crystals overnight at −18 °C.
Results and discussion
Aluminium trihalides (AlX3 (X = Cl, Br or I), are strong hard
[AlX3(R2E)] complexes
Lewis acids with a very high affinity for water.2 Successful syn-
thesis of their complexes with soft donor ligands such as thio-, The reaction of AlCl3 in CH2Cl2 or AlX3 (X = Br or I) in toluene
seleno- or telluro-ethers requires anhydrous AlX3, rigorously with Me2S affords [AlX3(Me2S)] in high yield. The chloro-
anhydrous solvents and ligands and exclusion of water at all complex is an oil at room temperature, the others crystalline
stages of the manipulations. Trace water displaces the neutral solids. The complexes can also be made by condensing excess
ligands and also generates [AlX4]− which are readily identified Me2S onto the appropriate AlX3 at −196 °C, allowing the
in the solids by their characteristic IR spectra ([AlCl4]− t2 = 498, mixture to thaw, when the halide dissolves to give a clear solu-
[AlBr4]− 394, [AlI4]− 336 cm−1 18 and in solution by 27Al NMR tion, and then removing excess Me2S in vacuo. The phase
)
spectroscopy (Table 1), where they have sharp characteristic diagram of the AlCl3/Me2S system4 shows both [AlCl3(Me2S)]
resonances. The moisture sensitivity of the halides and the and [AlCl3(Me2S)2], but on removing the volatiles in vacuo from
complexes is much greater than observed in the corresponding a mixture of AlCl3 and 3Me2S, only the 1 : 1 complex was
gallium(III) systems.12,13 The higher reactivity of the aluminium isolated.
halides also affects the choice of solvent for the synthesis.
The IR spectrum of [AlCl3(Me2S)] shows features at 541 and
Whilst complexes of AlCl3 are readily made in anhydrous 410 cm−1 assigned to the E and A1 modes of the pyramidal
CH2Cl2, use of this solvent for the AlBr3 or AlI3 reactions AlCl3 unit; both bands are quite broad and the E mode shows
results in incorporation of substantial amounts of chloride some evidence of further splitting. Similar observations were
Table 1 27Al NMR dataa
Compoundb
δ (27Al), 298 K
δ (27Al), 190 K
Comments
[AlCl4]−
103.5
80.6
−23.0
103.6
81.4
W1/2 ∼ 5 Hz
[AlBr4]−
W1/2 ∼ 15 Hz
[AlI4]−
[AlCl3(Me2S)]
[AlBr3(Me2S)]
[AIl3(Me2S)]
[AlCl3(Me2Se)]
[AlBr3(Me2Se)]
[AlCl3(Me2Te)]
W1/2 ∼ 25 Hz
111.6 W1/2 ∼ 310 Hz
81.2 W1/2 ∼ 250 Hz
48.7 W1/2 ∼ 360 Hz
110.5 W1/2 ∼ 300 Hz
99.7 W1/2 ∼ 170 Hz
105.9 W1/2 ∼ 310 Hz
92.6 W1/2 ∼ 320 Hz
109.9 W1/2 ∼ 490 Hz
92.6 W1/2 ∼ 555 Hz
105.5, 37.4
111.2
81.6
—
110.1
—
103.4
—
—
73.8 with excess Me2S (298 K)
No change with added Me2S
No change with added Me2S
No change with added Me2Se
[AlBr3(Me2Te)]
Resonance lost on cooling
[AlCl3(nBu2Se)]
[AlCl3(nBu2Te)]
—
[AlCl2{MeS(CH2)2SMe}2][AlCl4]
[AlBr2{MeS(CH2)2SMe}2][AlBr4]
[AlI2{MeS(CH2)2SMe}2][AlI4]
[AlCl2{MeSe(CH2)2SeMe}2][AlCl4]
[(AlCl3)2{C6H4(CH2SEt)2}]
80.6
−23.0
105.4
81.1
−23.0
—
Only anion resonance seen
Only anion resonance seen
111.3 W1/2 ∼ 900 Hz
—
a Chemical shifts relative to [Al(H2O)6]3+ in H2O at pH = 1. b In CH2Cl2–CD2Cl2 solution at temperature specified.
3638 | Dalton Trans., 2014, 43, 3637–3648
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
made in the spectra of many of the aluminium complexes in and telluroether complexes develop new resonances on stand-
this work, and are probably due to solid state effects, such as ing, some of which may be due to Me2E2, Me3E+ or Me2EX2
lower site symmetry or cation–anion interactions. The 1H NMR from their chemical shifts, but given the sensitivity of 77Se and
spectrum of [AlCl3(Me2S)] in CD2Cl2 (295 K) shows a singlet at 125Te chemical shifts to concentration, solvent etc.21,24 their
δ = 2.53 which does not change significantly on cooling the identification was not pursued. They do, however, provide evi-
solution to 190 K. Addition of aliquots of Me2S to the solution dence of the fragility in solution of the AlX3 complexes with
produces progressive shifts in the single resonance to low fre- the heavier chalcogenoethers.
quency, and on cooling to 185 K, two broad resonances are
In view of the scarcity of aluminium complexes of the
resolved at δ = 2.24 and 2.20, suggesting ligand exchange is heavier chalcogenoethers, structures of three examples, [AlCl3-
slowing, but that the low temperature limit has not been (Me2Se)], [AlCl3(Me2Te)] and [AlBr3(Me2Te)] were determined.
reached. The latter shift is similar to that of free Me2S (δ = The structures (Fig. 1–3) are isomorphous (orthorhombic,
2.15), whilst the former is assigned to a new aluminium Pbcm) and show the expected pseudo-tetrahedral geometry. The
complex. The 27Al NMR spectra are more informative (Table 1). bond lengths are mostly unexceptional, although the Al–Te dis-
At ambient temperatures a broad singlet at δ = 111.6 is present tances in [AlX3(Me2Te)] (X = Cl or Br) are the same within
in the spectrum of [AlCl3(Me2S)], which is little changed on experimental error.
cooling the solution to 190 K. However, addition of 1 mol.
Storing a solution of [AlCl3(Me2S)] in CH2Cl2 in the refriger-
equivalent of Me2S to the solution generates a new resonance ator, produced a few small crystals which were identified as
at δ = 73.5 (W1/2 = 650 Hz), and this resonance is unchanged the sulfonium salt [Me2SH][AlCl4] (Fig. 4), by the X-ray struc-
upon addition of more Me2S and shows only a small low fre- ture solution, and probably formed by adventitious hydrolysis.
quency drift on cooling the solution to 190 K. The new 27Al Solid sulfonium salts are rare, but we have previously obtained
chemical shift is in the range expected for five-coordinate Al examples from serendipitous hydrolysis of some niobium(V)
species.21 The combination of the 1H and 27Al NMR results fluoride–thioether complexes,25 the formation being promoted
show that in the presence of excess Me2S in CH2Cl2 solution by “anhydrous” conditions and a large weakly coordinating
the 2 : 1 complex [AlCl3(Me2S)2] forms; further addition of
Me2S does not produce any evidence for a 3 : 1 complex. As
noted above, work-up of the solution results in decomposition
to reform [AlCl3(Me2S)]. Five-coordination is established in the
solid state with aluminium–phosphine complexes, e.g.
[AlI3(PEt3)2], which has
phosphines.22
a
tbp geometry with axial
The complexes [AlX3(Me2S)] (X = Br or I) are generally
similar to the chloride complex, and exhibit progressively
lower frequency shifts in the 27Al NMR spectra as the halogen
becomes heavier (Table 1). However, although the 1H NMR
spectra show fast exchange with added Me2S in CH2Cl2 solu-
tion, no new resonances were evident in the 27Al NMR spectra
in the presence of a large excess of Me2S, indicating that in
these cases 2 : 1 complexes do not form.
Fig. 1 The structure of [AlCl3(Me2Se)] showing the numbering scheme.
Ellipsoids are drawn at the 50% probability level and H atoms are
omitted for clarity. Symmetry operation: a = x, y, 3/2 − z. Selected bond
lengths (Å) and angles (°) Se1–Al1 = 2.486(2), Cl1–Al1 = 2.121(2), Cl2–
Al1 = 2.1130(14), Cl2–Al1–Cl2a = 115.30(9), Cl2–Al1–Cl1 = 111.32(5),
Cl2–Al1–Se1 = 106.47(5), Cl1–Al1–Se1 = 105.20(6).
The [AlX3(Me2E)] (X = Cl, Br, E = Se or Te) were obtained in
1
high yields and their H NMR and IR spectroscopic properties
are similar to those of the thioether analogues. The 27Al NMR
spectra (Table 1) show only small low frequency shifts along
the series E = S > Se > Te, and no new complexes are formed by
adding excess Me2E to CH2Cl2 solutions of the appropriate
[AlX3(Me2E)]. [AlCl3(Me2Se)] shows a 77Se NMR chemical shift
of δ = −11.3, which corresponds to a small low frequency
coordination shift (Δ = −11.3); this can be compared with
small high frequency coordination shifts observed in
[GaX3(Me2Se)].12 Although high frequency coordination shifts
are seen in most transition metal selenoether (and telluro-
ether) complexes, in p-block complexes both high and low fre-
quency shifts are seen in different systems, and the causes are
not understood.23 We were unable to observe a 77Se NMR res-
onance from [AlBr3(Me2Se)] or 125Te resonances from
[AlX3(Me2Te)] over the temperature range 295–190 K, presum-
Fig. 2 The structure of [AlCl3(Me2Te)] showing the atom numbering
scheme. Ellipsoids are drawn at the 50% probability level and H atoms
are omitted for clarity. Symmetry operation: a = x, y, 1/2 − z. Selected
bond lengths (Å) and angles (°): Al1–Cl2
2.1295(10), Al1–Te1 = 2.6871(9), Cl2–Al1–Cl2a = 115.20(4), Cl2–Al1–
ably due to fast exchange. The solutions of the selenoether Cl1 = 111.14(3), Cl2–Al1–Te1 = 106.25(2), Cl1–Al1–Te1 = 106.21(3).
= 2.1207(6), Al1–Cl1 =
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 3637–3648 | 3639

View Article Online
Paper
Dalton Transactions
Fig. 3 The structure of [AlBr3(Me2Te)] showing the atom numbering
scheme. Ellipsoids are drawn at the 50% probability level and H atoms
are omitted for clarity. Symmetry operation: a = x, y, 3/2 − z. Selected
bond lengths (Å) and angles (°): Al1–Br1 = 2.286(3), Al1–Br2 = 2.287(2),
Al1–Te1 = 2.692(4), Br1–Al1–Br2 = 111.19(9), Br2–Al1–Br2a = 114.01(15),
Br1–Al1–Te1 = 106.34(12), Br2–Al1–Te1 = 106.80(9).
Fig. 5 The structure of [(AlCl3)2{o-C6H4(CH2SEt)2}] showing the atom
labelling scheme. The crystals had the properties of a modulated struc-
ture and the solution shown was derived from a smaller subcell. For this
reason bond lengths and angles are less reliable than usual and not pre-
sented here.
adducts described above, it was expected that flexible
dithioethers or diselenoethers (L–L) would produce complexes
of the type [X3Al(μ-L–L)AlX3]. In fact this was only true for the
bulky o-xylyl-backboned dithioether, o-C6H4(CH2SEt)2, which
gave yellow crystals of [(AlCl3)2{μ-o-C6H4(CH2SEt)2}]. The crys-
tals were of modest quality and had the characteristics of a
modulated structure (see Experimental), and thus comparison
of the detailed bond lengths and angles is not warranted.
However, they are isomorphous with the gallium(III) ana-
logue,13 and serve as an example of this structure type (Fig. 5).
The spectroscopic data are consistent with four-coordinate
aluminium in solution. The corresponding diselenoether
o-C6H4(CH2SeMe)2 was completely converted to the seleno-
Fig. 4 The structure of [Me2SH][AlCl4] showing the S2 centred cation
and the H-bond (dashed bond) to an adjacent Cl atom. Ellipsoids are
drawn at the 50% probability level and H atoms on C are not shown. The
other crystallographically independent cation is similar. Selected bond
lengths (Å): Al1–Cl3
= 2.1110(11), Al1–Cl4 = 2.1349(11), Al1–Cl2 =
2.1361(10), Al1–Cl1 = 2.1412(10), S2–H6 = 1.26(3), H6⋯Cl4 = 2.51(3).
anion. The S–H proton was identified in the difference map of nium cation [o-C6H4(CH2)2SeMe][AlCl4] upon reaction with
residual electron density. A bulk sample of [Me2SH][AlCl4] was AlCl3 in CH2Cl2 (see ESI†). The same selenonium cation is
obtained by saturating a dry CH2Cl2 solution of [AlCl3(Me2S)] formed upon reaction of this ligand with GaCl3 or InCl3.12,15
with HCl gas.
Unexpectedly, reaction of AlX3 with MeE(CH2)2EMe (E = S
The n-butyl derivatives [AlCl3(nBu2E)] (E = Se, Te) were also or Se) failed to give [X3Al{μ-MeE(CH2)2EMe}AlX3], and the pro-
synthesised as potential single source precursors for LPCVD as ducts had an AlX3 : MeE(CH2)2EMe ratio of 1 : 1 irrespective of
discussed below. Their characterisation data matched well the ratio of reactants used. Crystals of three examples were
with that of the equivalent methyl substituted complexes. The grown and showed the presence of pseudo-octahedral cations
telluroether complexes are not stable when stored at room and tetrahedral anions, [AlX2{MeE(CH2)2EMe}2][AlX4] (X = Cl,
temperature over a period of days to weeks, even in an N2 filled E = S or Se; X = I, E = S). The structures of [AlCl2{MeE-
glove box. They gradually become darker and a quantity of (CH2)2EMe}2][AlCl4] (Fig. 6 and 7) reveal centrosymmetric
black solid (elemental Te) forms. Samples can be stored at cations (trans isomer) with identical d(Al–Cl), which are as
−18 °C for a few weeks with minimal decomposition. A sample expected longer than in the four-coordinate complexes. The
of [AlCl3(nBu2Te)] that had been stored in the glove box for d(Al–S) and d(Al–Se) differ by ∼0.14 Å, which approximates to
several weeks and had visibly decomposed was analysed by the difference in covalent radii of the chalcogens.26 The bond
ESI+ mass spectrometry, which showed the presence of angles around the aluminium show only small deviations
[nBu3Te]+, and this ion was also present in the 125Te NMR spec- from 90°.
trum (δ = 491).13
Although both of the structures contain the chalcogeno-
ether in the DL conformation, the two crystals are not isomor-
phous and in the selenoether complex there are short contacts
Se2⋯Se2′ (3.436 Å) and Se3⋯Se3″ (3.542 Å). These link Al2-
centred cations into chains through Se2 (along the a direction)
Complexes with bidentate ligands
By analogy with the corresponding GaX3 adducts,12 and con-
sidering the preference for four-coordination in [AlX3(R2E)]
3640 | Dalton Trans., 2014, 43, 3637–3648
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
[AlCl4] shows a second resonance (δ 27Al = 37.4) which is
assigned to the six-coordinate cation. For the other complexes
it is likely that the increasing electric field gradients promote
fast quadrupolar relaxation, resulting in the loss of the cation
resonance.
At room temperature a CD2Cl2 solution of [AlCl2{MeS-
(CH2)2SMe}2][AlCl4] shows singlet CH3 (δ = 2.26) and CH2 (δ =
3.08) resonances. On cooling to 223 K the spectrum shows
three CH3 resonances (δ = 2.26, 2.50, 2.66) and overlapping
CH2 resonances (δ = 3.08–3.31), which we tentatively assign to
a mixture of cis and trans isomers of [AlCl2{MeS(CH2)2SMe}2]+,
the changes reversing on warming the solution. The bromo-
and iodo-complexes behave similarly. Notably, none of the
complexes show resonances due to free dithioether, which
would seem to rule out significant amounts of [AlCl2{MeS-
(CH2)2SMe}]+, being present. At 185 K further splitting of the
resonances is evident, which is probably due to slowing of the
pyramidal inversion at S, leading to separate resonances for
the individual invertomers. The solutions decompose slowly
on standing.
Fig. 6 The structure of a cation in trans-[AlCl2{MeS(CH2)2SMe}2][AlCl4]
showing the numbering scheme for the centrosymmetric Al2 centred
cation. Ellipsoids are drawn at the 50% probability level and H atoms are
not shown for clarity. The other cation is similar. Symmetry operation:
a = 2 − x, −y, 1 − z. Selected bond lengths (Å) and angles (°): Al2–Cl5 =
2.2131(10), Al2–S1 = 2.4595(11), Al2–S2 = 2.4809(10), S1–Al2–S2 =
87.92(4), S1–Al2–S2a = 92.08(4), Cl5–Al–S1a = 94.49(2), Cl5–Al2–S1 =
85.51(2), Cl5–Al2–S2a = 86.50(3), Cl5–Al2–S2 = 93.50(3).
The trans-[AlCl2{MeSe(CH2)2SeMe}2][AlCl4] exhibits a singlet
77Se NMR resonance at room temperature (δ = 95.5) which is a
low frequency coordination shift (Δ = −25.5) and singlet CH3
1
(δ = 2.36) and CH2 (δ = 3.21) resonances in the H NMR spec-
trum. Cooling the solution to 190 K produces little change in
the 1H NMR spectrum, although the 77Se resonance is lost
below ∼240 K. In the selenoether complex only the trans
isomer appears to be present in significant amounts. On
standing, new resonances grow in due to decomposition.
Attempts to record spectra in CD3CN solution resulted in dis-
placement of the thio- or seleno-ethers by the nitrile.
t
Reaction of AlCl3 with the ditelluroether BuTe(CH2)3TetBu
produced a mixture of species resulting from ligand fragmen-
tation. The H NMR spectrum of the product showed multiple
Fig. 7 The structure of a cation in trans-[AlCl2{MeSe(CH2)2SeMe}2]-
[AlCl4] showing the numbering scheme for the centrosymmetric Al2
centred cation. Ellipsoids are drawn at the 50% probability level and
H atoms are omitted for clarity. The other crystallographically indepen-
dent cation is similar. Symmetry operation: a = 1 − x, 1 − y, 1 − z.
Selected bond lengths (Å) and angles (°): Al2–Cl5 = 2.211(2), Al2–Se1 =
2.5950(13), Al2–Se2 = 2.6232(13), Se1–Al2–Se2 = 88.11(4), Se1–Al2–
Se2a = 91.89(4), Cl5–Al2–Se1a = 94.50(6), Cl5–Al2–Se1 = 85.50(6),
Cl5–Al2–Se2a = 86.51(6), Cl5–Al2–Se2 = 93.49(6).
1
resonances for the t-butyl groups and the CH2 units. Multiple
signals were also observed in the 125Te NMR spectrum, whilst
the 27Al NMR spectrum indicated the presence of [AlCl4]−. Very
air sensitive, yellow crystals were isolated of one of the
decomposition products, which proved to be [tBuTe(CH2)3Te-
(tBu)Te(CH2)3TetBu][AlCl4], derived from fragmentation of the
ditelluroether (see ESI†).
Polydentates and macrocycles
and similarly, the Al3-centred cations are linked into chains
through Se3 (again along the a direction) (Fig. 8).
The reaction of the tripodal trithioether MeC(CH2SMe)3 with
AlCl3 in a 1 : 1 molar ratio in anhydrous CH2Cl2 gave colourless
crystals whose structure (Fig. 10) showed a chain polymer with
the ligand binding as a bridging bidentate with one uncoordi-
nated –CH2SMe arm. The structure forms a chain in the a
direction The geometry at aluminium is a distorted trigonal
bipyramid with equatorial chlorines and there are two slightly
different aluminium environments in the unit cell.
The structure of the [AlI2{MeS(CH2)2SMe}2][AlI4] (Fig. 9)
also contains a pseudo-octahedral cation, but this has a cis-geo-
metry and with the dithioethers in the meso form. In cis-
[AlI2{MeS(CH2)2SMe}2]+ the Al–StransI are longer by ∼0.1 Å than
Al–StransS, but the Al–StransS distances are not significantly
different to those in trans-[AlCl2(MeSCH2CH2SMe)2][AlCl4].
The Nujol mull IR spectra for these salts all confirm the
presence of [AlX4]−, but the Al–X stretches of the cations could
not be identified with certainty. The solution speciation is less
clear, and all the complexes are extremely moisture sensitive
in solution. All four complexes show 27Al resonances assign-
able to the [AlX4]− (Table 1), but only [AlCl2{MeS(CH2)2SMe}2]-
In solution the 1H NMR spectrum shows single, sharp
–CH2, –SMe and –CMe resonances consistent with fast
exchange. Attempts to isolate complexes with higher AlCl3 :
tripod stoichiometries were unsuccessful. The [AlCl3{MeC-
(CH2SMe)3}] stoichiometry contrasts with the gallium complex
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 3637–3648 | 3641

View Article Online
Paper
Dalton Transactions
Fig. 8 View along the a axis of the packing diagrams of [AlCl2{MeS(CH2)2SMe}2][AlCl4] (left) and [AlCl2{MeSe(CH2)2SeMe}2][AlCl4] (right) showing the
different molecular packing.
macrocycle and a cis AlCl2 unit which serve to confirm the con-
stitution (see ESI†). Although not isomorphous, the structure
is similar to that of cis-[InCl2([14]aneS4}][InCl4].15 In contrast,
gallium chloride forms an exodentate chain polymer
[GaCl3([14]aneS4)] with trigonal bipyramidal coordination.13
The larger ring [16]aneSe4 forms trans-[MCl2([16]aneSe4)]-
[MCl4] (M = Ga or In)13 and the aluminium complex probably
has an analogous structure. The 16-membered ring macrocycle
complexes were insoluble in CH2Cl2 and the macrocycle was
displaced by stronger donor solvents.
LPCVD investigation
Fig. 9 The structure of the cation in cis-[AlI2{MeS(CH2)2SMe}2][AlI4]
Following previous success in using neutral chalcogenoether
showing the atom labelling scheme. Ellipsoids are drawn at the 50%
adducts of GaCl3 to deposit thin films of crystalline Ga2Se3
probability level and H atoms are omitted for clarity. Selected bond
lengths (Å) and angles (°): Al1–S1 = 2.431(4), Al1–S4 = 2.448(4), Al1–S3 =
and Ga2Te3,17 several coordination complexes of AlCl3 were
2.533(5), Al1–S2 = 2.546(5), Al1–I1 = 2.612(4), Al1–I2 = 2.635(4), I1 Al1–
I2 = 97.30(13), S1–Al1–S3 = 84.84(15), S4–Al1–S3 = 83.28(14), S1–Al1–
S2 = 83.46(15), S4–Al1–S2 = 79.24(14), S3–Al1–S2 = 76.13(15), S1–Al1–
had previously been shown to be more effective than ligands
I1 = 99.17(14), S4–Al1–I1 = 89.96(14), S2–Al1–I1 = 93.69(14), S1–Al1–I2
= 94.43(13), S4–Al1–I2 = 101.02(15), S3–Al1–I2 = 92.95(14).
synthesised as potential single source precursors to Al2E3
films. Ligands with nBu substituents were selected as these
with Me substituents, probably because they have the
β-hydride elimination route available.17 [AlCl3(nBu2E)] (E =
Se, Te) were synthesised as yellow oils as described above.
LPCVD using both complexes was attempted at temperatures
between 723 and 873 K, using the CVD equipment described
previously.13 In all cases the precursor evaporated cleanly,
having changed colour to dark brown during the evaporation.
There was no deposition on the substrates and some elemental
selenium or tellurium was deposited on the tube at the exit of
the furnace. We conclude that these reagents are unsuitable
for LPCVD under these conditions.
which was [(GaCl3)3{MeC(CH2SMe)3}], assumed to contain
tetrahedral gallium coordination.12
The reaction of the small ring thia-macrocycle [9]aneS3 with
an equimolar amount of AlCl3 in toluene gave a white powder,
[AlCl3([9]aneS3)]. The complex is insoluble in CH2Cl2 and the
macrocycle is displaced by coordinating solvents like MeCN,
precluding solution measurements. Both gallium and indium
form similarly intractable 1 : 1 complexes with this ligand,11
and it seems likely that all three contain fac-octahedral struc-
tures. The larger macrocycles [14]aneS4 and [16]aneSe4 reacted
with two molar equivalents of AlCl3 in anhydrous CH2Cl2 to
form insoluble white complexes. The analytical data supported
a formulation [AlCl2(macrocycle)][AlCl4] (macrocycle = [14]-
aneS4 and [16]aneSe4) and the far IR spectra confirmed the
presence of [AlCl4]− anions. Poor quality crystals of [AlCl2([14]-
aneS4)][AlCl4] were obtained from the filtrate from the reaction
solution and the structure shows the cation with endodentate
Comparisons of Lewis acid behaviour of Al, Ga and In towards
chalcogenoethers
There has been much recent interest in exploring Group 13
Lewis acid–Lewis base adducts both by modelling and experi-
ment. The modelling work has mostly focussed on boron and
aluminium complexes with O- or N-donor ligands, with trends
sometimes extrapolated to gallium. The conclusions of these
studies, although sometimes disputed in detail, were that
3642 | Dalton Trans., 2014, 43, 3637–3648
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
Fig. 10 The structure of the asymmetric unit in [AlCl3{MeC(CH2SMe)3}] showing the atom labelling scheme. Ellipsoids are drawn at the 50% prob-
ability level and H atoms are omitted for clarity. Selected bond lengths (Å) and angles (°): Al1–Cl1 = 2.151(3), Al1–Cl2 = 2.152(3), Al1–Cl3 = 2.154(3),
Al1–S5 = 2.473(3), Al1–S2 = 2.489(3), Al2–Cl5 = 2.158(3), Al2–Cl6 = 2.160(3), Al2–Cl4 = 2.169(3), Al2–S3 = 2.469(3), Al2–S6 = 2.488(3), Cl1–Al1–Cl2
= 117.05(12), Cl1–Al1–Cl3 = 118.80(13), Cl2–Al1–Cl3 = 124.15(13), Cl1–Al1–S5 = 94.98(11), Cl2–Al1–S5 = 88.33(11), Cl3–Al1–S5 = 86.31(10), Cl1–
Al1–S2 = 95.32(11), Cl2–Al1–S2 = 89.27(11), Cl3–Al1–S2 = 86.49(10), S5–Al1–S2 = 169.38(11), Cl5–Al2–Cl6 = 117.44(13), Cl5–Al2–Cl4 = 119.86(12),
Cl6–Al2–Cl4 = 122.70(12), Cl5–Al2–S3 = 94.48(10), Cl6–Al2–S3 = 89.38(11), Cl4–Al2–S3 = 86.84(11), Cl5–Al2–S6 = 90.27(10), Cl6–Al2–S6 =
92.63(10), Cl4–Al2–S6 = 86.71(11), S3–Al2–S6 = 173.30(12).
Lewis acidity falls AlCl3 > AlBr3 > AlI3, and AlCl3 > AlBr3
>
Lewis acidity of Al(III). We note that the dft calculations
GaCl3 > GaBr3 (ref. 27–31 and references therein). One should predict31 an Al–Se bond length (for the gas phase molecule) of
note in passing that the order with halogen is reversed for 2.53 Å compared to the X-ray crystallographic result (for the
boron. The modelling work is based upon gas phase molecules solid) of 2.486(2) Å.
and does not take into account solid state effects (lattice ener-
Our data also show the ready formation of six-coordinate
gies, intermolecular interactions and packing effects), or the cations with aluminium, [AlX2(L–L)2]+, contrasting with the
effects of lattice solvent, which may complicate the interpret- reluctance of gallium to exceed four-coordination, except in
ation of experimental data, and in some cases lead to appar- macrocyclic compounds, cannot be due to steric effects, but
ently anomalous results.30 The various contributions listed must be a further consequence of the stronger Lewis acidity of
above, means that interpreting changes in metal–ligand bond aluminium. These differences must originate in the donor/
lengths simply in terms of Lewis acidity must be done with acceptor orbital energy match (or mis-match) rather than in
care, and one might expect the occasional anomaly, but as a charge/radius effects. The larger indium centre has a less clear
result of recent studies, there are sufficient data available to preference, easily accommodating four-, five- or six-coordi-
attempt some comparisons for Al/Ga/In–Group 16 donor com- nation depending upon the ligand and reaction conditions.
plexes. Table 2 shows some illustrative data.
The data show firstly, that if one compares complexes of
the same element with the same coordination number, the
M–X distances seem unaffected by the specific chalcogen
Conclusions
donor type present, which is consistent with the metal– Chalcogenoether complexes of aluminium(III) halides with
halogen being the dominant interaction. A similar comparison four-, six- and (rarely) five-coordinate metal centres have been
of the M–E bond lengths shows that these increase (sometimes prepared, and their structures and properties compared with
only marginally) with halide, Cl < Br < I, consistent with the those of the heavier analogues GaX3 and InX3. The aluminium
trends deduced for lighter donor atoms. The M–X, and M–E complexes are extremely moisture sensitive, and complexes
bond lengths in comparable complexes of Al and Ga are also with selenium or tellurium ligands are prone to slow E–C
nearly identical, consistent with their almost identical covalent bond cleavage in solution. Nonetheless, the formation and
radii, resulting from the “3d block contraction”, i.e. the structural characterisation of telluroether complexes of the
increased nuclear charge resulting from the 3d metals only hard AlX3 acceptors is notable. In contrast to the gallium com-
partially screened by the d electron shell.26 As expected, In–X plexes, it does not appear that the aluminium systems are suit-
and In–E bonds are typically ∼0.2 Å longer. A very recent dft able for LPCVD applications. The detailed study of Al(III)
study31 suggested that whilst Ga and In halide complexes of complexes with soft, modest donor chalcogenoethers has con-
Me2Se had a high degree of covalency in the M–Se bonds, firmed the trends in Lewis acidity observed with hard O or N
those of aluminium had a markedly higher electrostatic com- donor ligands and are broadly in line with expectations based
ponent to the bonding. Our experimental data reported in the upon the dft calculations. The work further demonstrates that
present paper, show no evidence for a significant change in a significant range of chalcogenoether complexes with hard
the bonding type present along the series of group 16 donor p-block Lewis acids are obtainable despite the hard/soft- accep-
complexes, the differences noted being due to the higher tor/donor mismatch.
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 3637–3648 | 3643

View Article Online
Paper
Dalton Transactions
Table 2 Structural data on Group 16 ligand adducts of Al, Ga and In halides
Compound
M–X/Å
M–E/Å
Coordination number of M
Reference
[AlCl3(Me2Se)]
[AlCl3(Me2Te)]
[AlBr3(Me2Te)]
2.121(2), 2.113(1)
2.1207(6), 2.1295(10)
2.286(3), 2.287(2)
2.2131(10)
2.612(4), 2.635(4)
2.211(2)
2.4997(7)–2.5316(7)
2.1478(14)–2.1650(15)
2.1606(8), 2.1700(10)
2.5209(2)–2.5277(2)
2.149(2)–2.166(2)
2.158(3)–2.181(3)
2.276(3)–2.296(3)
2.3058(11), 2.3220(12)
2.4901(12), 2.4981(7)
2.4243(1), 2.4457(1)a
2.4237(18), 2.393(18)
2.5775(5), 2.5918(5)
2.6076(15), 2.6113(15)
2.475(2)
2.486(2)
2.6871(9)
2.692(4)
2.4595(11), 2.4809(10)
2.431(4)–2.546(5)
2.5950(13), 2.6232(13)
2.4048(12)
2.3573(15)
2.4637(7)
4
4
4
6
6
6
4
4
4
4
4
4
6
6
4
6
6
6
6
6
This work
This work
This work
This work
This work
This work
12
12
12
14
12
17
13
13
15
14
15
15
15
13
trans-[AlCl2{MeS(CH2)2SMe}2]+
cis-[AlI2{MeS(CH2)2SMe}2]+
trans-[AlCl2{MeSe(CH2)2SeMe}2]+
[(GaI3)2{MeS(CH2)2SMe}2]
[(GaCl3)2{o-C6H4(CH2SMe)2}]
[GaCl3(Me2Se)]
[GaI3(Me2Se)]
2.479(2)
2.468(1)
[(GaCl3)2{nBuSe(CH2)2SenBu}]
[(GaCl3)2{tBuTe(CH2)3TetBu}]
trans-[GaCl2([16]aneS4]+
trans-[GaCl2([16]aneSe4]+
[InBr3(Me2Se)]
2.6378(14), 2.6356(13)
2.482(4)–2.518(4)
2.5906(7)–2.6106(8)
2.6455(11)
2.7722(6), 2.7802(6)
2.645(2)–2.696(2)
2.6518(10)–2.6901(11)
2.7370(16)–2.7762(15)
2.7189(10), 2.7394(11)
[(InCl3)2(Me2Se)4]
trans-[InCl2({iPrS(CH2)2SiPr}2]+
trans-[InBr2({iPrS(CH2)2SiPr}2]+
trans-[InBr2{MeSe(CH2)2SeMe}2]+
trans-[InCl2([16]aneSe4]+
a Terminal M–X.
[AlI3(Me2S)]: AlI3 (0.20 g, 0.5 mmol) was dissolved in
toluene (10 mL) to give a pale yellow solution and Me2S
Experimental
Infrared spectra were recorded as Nujol mulls between CsI (0.03 g, 0.5 mmol) was added dropwise. After stirring for
plates using a Perkin-Elmer Spectrum 100 spectrometer over 15 minutes, all solvent was removed in vacuo to give a pale
the range 4000–200 cm−1
.
1H NMR spectra were recorded yellow solid. Yield 0.17 g, 75%. Anal. Calcd for C2H6AlI3S: C,
1
using a Bruker AV300 spectrometer. 77Se{1H}, 125Te{1H} and 5.1; H, 1.3. Found: C, 5.0; H, 1.3%. H NMR (CD2Cl2, 295 K):
27Al NMR spectra were recorded using a Bruker DPX400 2.44 (s). 27Al NMR (CD2Cl2, 295 K): 48.7. IR (cm−1, Nujol): 336
spectrometer and are referenced to external neat SeMe2, TeMe2 (br) Al–I.
and aqueous [Al(H2O)6]3+ at pH = 1, respectively. Microanalyses
[Me2SH][AlCl4]: Me2S (0.09 g, 1.5 mmol) was added drop-
were undertaken by Medac Ltd or London Metropolitan Uni- wise to a suspension of AlCl3 (0.20 g, 1.5 mmol) in anhydrous
versity. Solvents were dried prior to use: toluene by distillation CH2Cl2 (25 mL) with stirring to give a colourless solution. HCl
from sodium benzophenone ketyl, CH2Cl2 from CaH2, and all was slowly bubbled through the solution for ∼30 seconds.
preparations were undertaken using standard Schlenk tech- After stirring for 30 minutes, some white precipitate formed.
niques under a N2 atmosphere. Anhydrous aluminium(III) The white solid was collected by filtration and dried in vacuo.
halides (Aldrich or Strem) were used as received. SMe2 and The volume of the pale yellow filtrate was reduced to ∼10 mL.
SeMe2 (Aldrich) were stored over molecular sieves. Other thio- Colourless crystals suitable for single crystal X-ray diffraction
seleno- and telluroethers were made by literature methods32–36 were obtained after storage of the filtrate at −18 °C for
and stored under dinitrogen over molecular sieves.
24 hours. Yield 82%. Anal. Calcd for C2H7AlCl4S: C, 10.4; H,
[AlCl3(Me2S)]: Me2S (0.09 g, 1.5 mmol) was added dropwise 3.0. Found: C, 10.5; H, 2.9%. IR (cm−1, Nujol): 2482 (br, w) SH,
to a suspension of AlCl3 (0.20 g, 1.5 mmol) in anhydrous 488 (br), 467 (br), 395 (s) [AlCl4]−; the strong S–H⋯Cl–Al inter-
CH2Cl2 (15 mL) with stirring to give a colourless solution. After actions causes extensive splitting of the t2 Al–Cl stretching
30 minutes, all solvent was removed in vacuo to give a colour- mode in the anion.
less oil. Yield 0.26 g, 89%. Anal. Calcd for C2H6AlCl3S: C, 12.3;
[AlCl3(Me2Se)]: Me2Se (0.16 g, 1.5 mmol) was added drop-
H, 3.1. Found: C, 12.4; H, 3.1%. 1H NMR (CDCl3, 295 K): wise to a suspension of AlCl3 (0.2 g, 1.5 mmol) in anhydrous
2.53 (s). 27Al NMR (CD2Cl2, 295 K): 111.6. IR (cm−1): 541 (s), CH2Cl2 (15 mL) with stirring to give a colourless solution. After
410 (m). Raman (cm−1): 404 (m) Al–Cl.
30 minutes, the volume of solvent was reduced in vacuo to
[AlBr3(Me2S)]: AlBr3 (0.10 g, 0.37 mmol) was dissolved in ∼5 mL. Storage at −18 °C for 24 hours produced colourless
toluene (10 mL) to give a pale yellow solution and Me2S crystals. Yield 0.30 g, 82%. Anal. Calcd for C2H6AlCl3Se: C, 9.9;
(0.023 g, 0.37 mmol) was added dropwise when the solution H, 2.5. Found: C, 10.0; H, 2.6%. 1H NMR (CDCl3, 295 K):
became colourless. After stirring for 15 minutes, all solvent 2.92 (s); (283 K): 2.83 (s). 27Al NMR (CDCl3, 295 K): 110.5. 77Se
was removed in vacuo to give a white solid. Yield 0.10 g, 79%. NMR (CDCl3, 273 K): −11.3; (183 K): −14.0. IR (cm−1, Nujol):
Anal. Calcd for C2H6AlBr3S: C, 7.3; H, 1.8. Found: C, 6.4; H, 531 (s), 399 (m). Raman (cm−1): 521 (w), 399 (s) Al–Cl.
2.0%. 1H NMR (CD2Cl2, 295 K): 2.51 (s). 27Al NMR (CD2Cl2,
[AlBr3(Me2Se)]: AlBr3 (0.10 g, 0.37 mmol) was dissolved in
toluene (10 mL) to give a pale yellow solution and Me2Se
295 K): 81.2; (185 K): 81.6. IR (cm−1, Nujol): 392 (br) Al–Br.
3644 | Dalton Trans., 2014, 43, 3637–3648
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
(0.04 g, 0.37 mmol) was added dropwise when the solution AlBr3 (0.20 g, 0.75 mmol) in toluene (15 mL) with stirring to
became colourless. After stirring for 15 minutes, all solvent give a colourless solution and a white precipitate. After
was removed in vacuo to give a white solid. Yield 0.11 g, 80%. 30 minutes the reaction mixture was filtered and the white
Anal. Calcd for C2H6AlBr3Se: C, 6.4; H, 1.6. Found: C, 6.1; H, solid dried in vacuo. Yield 0.21 g, 72%. Anal. Calcd for
1.9%. 1H NMR (CD2Cl2, 295 K): 2.47 (s). 27Al NMR (CD2Cl2, C8H20Al2Br6S4: C, 12.3; H, 2.6. Found: C, 11.7; H, 2.9%. 1H
295 K): 99.7. IR (cm−1, Nujol): 446 (s), 397 (s) Al–Br.
[AlCl3(nBu2Se)]: A solution of nBu2Se (0.29 g, 1.5 mmol) in (CD2Cl2, 295 K): 80.6. IR (cm−1, Nujol): 405 (s, br), 355 (s, br).
anhydrous CH2Cl2 (7 mL) was added dropwise to a suspension [AlI2{MeS(CH2)2SMe}2][AlI4]: MeS(CH2)2SMe (0.06 g,
NMR (CD2Cl2, 295 K): 3.10 (s, [4H]), 2.26 (s, [6H]). 27Al NMR
of AlCl3 (0.20 g, 1.5 mmol) in anhydrous CH2Cl2 (8 mL) with 0.5 mmol) was added dropwise to a pale yellow solution of AlI3
stirring to give a colourless solution. After 30 minutes, all (0.20 g, 0.5 mmol) in toluene (15 mL) with stirring to give an
solvent was removed in vacuo to yield a pale yellow oil. Yield orange solution and some pale yellow precipitate.
0.36 g, 73%. Anal. Calcd for C8H18AlCl3Se: C, 29.4; H, 5.6. After 30 minutes the reaction mixture was filtered and the
Found: C, 29.7; H, 5.8%. 1H NMR (CD2Cl2, 295 K): 3.03 (t, pale yellow solid dried in vacuo. Crystals suitable for
[4H]), 1.82 (m, [4H]), 1.46 (m, [4H]), 0.97 (t, [6H]). 27Al NMR single crystal X-ray diffraction were obtained after storage of
(CD2Cl2, 295 K): 109.9. 77Se NMR (CDCl3, 295 K): 102.9. the filtrate at −18 °C for 48 hours. Yield 0.19 g, 74%.
IR (cm−1): 539 (s), 399 (m) Al–Cl.
Anal. Calcd for C8H20Al2I6S4: C, 9.1; H, 1.9. Found: C, 8.9; H,
[AlCl3(Me2Te)]: Me2Te (0.12 g, 0.75 mmol) was added drop- 3.3%. 1H NMR (CD2Cl2, 295 K): 2.77 (s, [4H]), 2.17 (s, [6H]).
wise to a suspension of AlCl3 (0.10 g, 0.75 mmol) in anhydrous 27Al NMR (CD2Cl2, 295 K): −23.0. IR (cm−1, Nujol): 338 (s),
CH2Cl2 (10 mL) with stirring to give a colourless solution. After 304 (m).
30 minutes, the volume of solvent was reduced in vacuo to
[AlCl2{MeSe(CH2)2SeMe}2][AlCl4]: MeSe(CH2)2SeMe (0.16 g,
∼5 mL. Storage at −18 °C for 24 hours produced yellow crys- 0.75 mmol) was added dropwise to a suspension of AlCl3
tals. Yield: 0.135 g, 62%. Anal. Calcd for C2H6AlCl3Te: C, 8.3; (0.10 g, 0.75 mmol) in anhydrous CH2Cl2 (10 mL) with stirring
H, 2.1. Found: C, 8.6; H, 2.1%. 1H NMR (CD2Cl2, 295 K): to give a yellow solution. After 30 minutes the volume of
2.19 (s). 27Al NMR (CD2Cl2, 295 K): 105.9. IR (cm−1, Nujol): 491 solvent was reduced in vacuo to ∼5 mL. Storage of the solution
(s), 395 (m) Al–Cl.
at −18 °C for 24 hours produced colourless crystals. Yield
[AlBr3(Me2Te)]: AlBr3 (0.10 g, 0.37 mmol) was dissolved in 0.18 g, 69%. Anal. Calcd for C8H20Al2Cl6Se4: C, 13.8; H, 2.9.
toluene (10 mL) to give a pale yellow solution. Me2Te (0.06 g, Found: C, 12.8; H, 2.7%. 1H NMR (CDCl3, 295 K): 3.21 (s,
0.37 mmol) was added dropwise to give a paler yellow solution. [4H]), 2.36 (s, [6H]). 27Al NMR (CDCl3, 295 K): 105.4. 77Se NMR
After stirring for 15 minutes, all solvent was removed in vacuo (CDCl3, 295 K): 95.4. IR (cm−1, Nujol): 488 (s), 442 (m).
to give a yellow solid. Yield: 0.11 g, 68%. Anal. Calcd for
[AlCl3{MeC(CH2SMe)3}]:
MeC(CH2SMe)3
(0.16
g,
1
C2H6AlBr3Te: C, 5.7; H, 1.4. Found: C, 5.7; H, 1.8%. H NMR 0.75 mmol) was added dropwise to a suspension of AlCl3
(CD2Cl2, 295 K): 2.66 (s). 27Al NMR (CD2Cl2, 295 K): 92.6. IR (0.10 g, 0.75 mmol) in anhydrous CH2Cl2 (10 mL) with stirring
(cm−1, Nujol): 404 (m), 391 (m) Al–Br.
to give a colourless solution. After 30 minutes the volume of
n
[AlCl3(nBu2Te)]: A solution of Bu2Te (0.18 g, 0.75 mmol) in solvent was reduced in vacuo to ∼5 mL. Colourless crystals suit-
anhydrous CH2Cl2 (7 mL) was added dropwise to a suspension able for single crystal X-ray diffraction were obtained after
of AlCl3 (0.10 g, 0.75 mmol) in anhydrous CH2Cl2 (8 mL) with storage at −18 °C for 48 hours. Yield 0.18 g, 70%. Anal. Calcd
stirring to give a yellow solution. After 15 minutes, all solvent for C8H18AlCl3S3·1/2CH2Cl2: C, 26.4; H, 5.0. Found: C, 26.9; H,
was removed in vacuo to yield a yellow oil. Yield 0.22 g, 78%. 4.9%. 1H NMR (CDCl3, 295 K): 2.76 (s, [6H]), 2.25 (s, [9H]),
Anal. Calcd for C8H18AlCl3Te: C, 25.6; H, 4.8. Found: C, 26.1; 1.16 (s, [3H]). IR (cm−1, Nujol): 534 (s), 491 (s).
H, 5.1%. 1H NMR (CD2Cl2, 295 K): 2.95 (t, [4H]), 1.83 (m, [4H]),
1.43 (m, [4H]), 0.96 (t, [6H]). 27Al NMR (CD2Cl2, 295 K): 106.8. 0.75 mmol) was added dropwise to a suspension of AlCl3
IR (cm−1): 495 (s), 395 (m) Al–Cl.
(0.20 g, 1.5 mmol) in anhydrous CH2Cl2 (15 mL) with stirring
[(AlCl3)2{C6H4(CH2SEt)2}]:
o-C6H4(CH2SEt)2
(0.17
g,
[AlCl2{MeS(CH2)2SMe}2][AlCl4]: MeS(CH2)2SMe (0.18 g, to give a yellow solution. After 30 minutes the volume of
1.5 mmol) was added dropwise to a suspension of AlCl3 solvent was reduced in vacuo to ∼5 mL. Storage of the solution
(0.20 g, 1.5 mmol) in anhydrous CH2Cl2 (15 mL) with stirring at −18 °C for 24 hours produced yellow crystals. Yield 0.22 g,
to give a colourless solution. After 30 minutes the volume of 60%. Anal. Calcd for C12H18Al2Cl6S2: C, 29.2; H, 3.7. Found: C,
1
solvent was reduced in vacuo to ∼5 mL. A large quantity of 29.3; H, 3.7%. H NMR (CDCl3, 295 K): 7.47 (m, [4H]), 4.37 (s,
white solid precipitated after storage at −18 °C for 24 hours. [4H]), 3.08 (q, [4H]), 1.49 (t, [6H]). 27Al NMR (CDCl3, 295 K):
The solid was collected by filtration and dried in vacuo. Yield 111.3. IR (cm−1, Nujol): 565–500 (vbr, s), 394 (s). Raman
0.26 g, 68%. Anal. Calcd for C8H20Al2Cl6S4: C, 18.8; H, 3.9. (cm−1): 518 (m), 402 (m).
Found: C, 18.3; H, 3.8%. 1H NMR (CD2Cl2, 295 K): 3.07 (s,
[AlCl3([9]aneS3)]: A solution of [9]aneS3 (0.14 g, 0.75 mmol)
[4H]), 2.25 (s, [6H]). 27Al NMR (CDCl3, 295 K): 105.5, 37.4. in anhydrous toluene (10 mL) was added to a solution of AlCl3
IR (cm−1, Nujol): 489 (s), 463 (s), 346 (w). Raman (cm−1): (0.10 g, 0.75 mmol) in anhydrous toluene (10 mL) with stirring
490 (w), 350 (s), 295 (s).
to give a colourless solution and a large quantity of white pre-
[AlBr2{MeS(CH2)2SMe}2][AlBr4]: MeS(CH2)2SMe (0.09 g, cipitate. After 60 minutes, the precipitate was collected by fil-
0.75 mmol) was added dropwise to a pale yellow solution of tration and dried in vacuo. Yield 0.16 g, 68%. Anal. Calcd for
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 3637–3648 | 3645

View Article Online
Paper
Dalton Transactions
C6H12AlCl3S3: C, 23.0; H, 3.9. Found: C, 23.1; H, 3.9%. IR precipitate was collected by filtration and dried in vacuo. Yield
(cm−1, Nujol): 408 (s), 375 (m) Al–Cl.
0.20 g, 70%. Anal. Calcd for C12H24Al2Cl6Se4: C, 19.2; H, 3.2.
[AlCl2([14]aneS4)][AlCl4]: A solution of [14]aneS4 (0.10 g, Found: C, 19.0; H, 3.1%. IR (cm−1): 483 (s), 434 (br).
0.37 mmol) in anhydrous CH2Cl2 (10 mL) was added to a sus-
pension of AlCl3 (0.10 g, 0.75 mmol) in anhydrous CH2Cl2
X-Ray experimental
(10 mL) with stirring to give a colourless solution. After
approximately 5 minutes a large quantity of white precipitate
formed. After 60 minutes, the precipitate was collected by fil-
tration and dried in vacuo. Yield 0.14 g, 70%. Anal. Calcd for
C10H20Al2Cl6S4: C, 22.4; H, 3.8. Found: C, 22.6; H, 3.7%. IR
(cm−1, Nujol): 481 (br, s), 419 (m).
[AlCl2([16]aneSe4)][AlCl4]: was made similarly from a solution
of [16]aneSe4 (0.18 g, 0.37 mmol) in anhydrous CH2Cl2 (10 mL)
and AlCl3 (0.1 g, 0.75 mmol) in anhydrous CH2Cl2 (10 mL). The
Details of the crystallographic data collection and refinement
parameters are given in Table 3. Crystals suitable for single
crystal X-ray analysis were obtained as described above. Data
collections used a Rigaku AFC12 goniometer equipped with an
enhanced sensitivity (HG) Saturn724+ detector mounted at the
window of an FR-E+ SuperBright molybdenum (λ = 0.71073 Å)
rotating anode generator with VHF Varimax optics (100 µm
focus) with the crystal held at 100 K (N2 cryostream). Structure
solution and refinement were straightforward,37,38 except as
Table 3 Crystal data and structure refinement detailsa
[AlCl2{MeS(CH2)2-
SMe}2] [AlCl4]
[AlCl2{MeSe(CH2)2-
SeMe}2] [AlCl4]
Compound
[AlCl3(Me2Se)]
[AlCl3(Me2Te)]
[AlBr3(Me2Te)]
Formula
M
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
C2H6AlCl3Se
242.36
Orthorhombic
Pbcm (no. 57)
6.205(4)
12.603(8)
10.479(6)
90
90
90
819.6(8)
4
5.564
C2H6AlCl3Te
291.00
Orthorhombic
Pbcm (no. 57)
6.248(1)
13.114(3)
10.514(2)
90
90
90
861.4(3)
4
4.388
C2H6AlBr3Te
424.38
Orthorhombic
Pbcm (no. 57)
6.562(3)
13.400(5)
10.724(4)
90
90
90
943.0(6)
4
15.870
8126
C8H20Al2Cl6S4
511.14
C8H20Al2Cl6Se4
698.74
Monoclinic
P21/c (no. 14)
7.122(4)
17.744(8)
17.582(8)
90
93.169(8)
90
2218.5(18)
4
Triclinic
ˉ
P1 (no. 2)
6.708(5)
10.583(5)
15.383(5)
90.070(5)
102.422(5)
96.512(5)
1059.2(10)
2
β [°]
γ [°]
U [Å3]
Z
μ(Mo Kα) [mm−1
Total no. reflns
Unique reflns
Rint
]
1.276
11 612
6072
7.405
10 277
5039
4909
1315
0.103
3839
1312
0.018
1140
0.297
0.026
0.114
No. of params, restraints
38, 0
0.055
38, 0
0.018
38, 0
0.065
188, 0
0.046
188, 0
0.077
R1b [Io > 2σ(Io)]
R1 [all data]
0.065
0.137
0.148
0.022
0.034
0.035
0.068
0.163
0.168
0.059
0.072
0.077
0.091
0.196
0.207
wR2b [Io > 2σ(Io)]
wR2 [all data]
Compound
[AlI2{MeS(CH2)2SMe}2] [AlI4]
[{o-C6H4(CH2SEt)2}(AlCl3)2]
[AlCl3(MeC(CH2SMe)3)]
[Me2SH][AlCl4]
Formula
M
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
C8H20Al2I6S4
1059.84
Monoclinic
P21/c (no. 14)
14.825(3)
12.181(2)
15.150(4)
90
C12H18Al2Cl6S2
493.04
Monoclinic
C2/c (no. 15)
18.745(2)
10.810(10)
13.608(12)
90
C16H36Al2Cl6S6
687.47
Monoclinic
P21/c (no. 14)
16.131(7)
8.310(3)
24.976(11)
90
C2H7AlCl4S
231.92
Monoclinic
P21/c (no. 14)
14.3783(7)
10.9075(7)
12.3742(5)
90
β [°]
108.449(8)
90
2595.3(10)
4
7.563
24 085
125.779(1)
90
2237(3)
4
1.026
8120
107.156(8)
90
3199(2)
4
0.991
10 176
4613
90.260(3)
90
1940.64(17)
8
1.443
11 008
γ [°]
U [Å3]
Z
μ(Mo Kα) [mm−1
Total no. reflns
Unique reflns
Rint
]
5928
0.152
2199
0.041
4432
0.035
0.133
No. of params, restraints
185, 0
0.057
100, 3
0.108
279, 0
0.085
153, 0
0.045
R1b [Io > 2σ(Io)]
R1 [all data]
0.135
0.106
0.115
0.121
0.258
0.277
0.103
0.193
0.207
0.055
0.156
0.189
wR2b [Io > 2σ(Io)]
wR2 [all data]
a Common items: temperature = 100 K; wavelength (Mo-Kα) = 0.71073 Å; θ(max) = 27.5°. b R1 = ∑||Fo| − |Fc||/∑|Fo|; wR2 = [∑w(Fo − Fc2)2/
2
4 1/2
∑wFo
]
.
3646 | Dalton Trans., 2014, 43, 3637–3648
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
detailed below, with H atoms bonded to C being placed in cal-
culated positions using the default C–H distance. For
[AlCl3{MeC(CH2SMe)3}] the data were collected using the
Rigaku automated routines which normally gives close to
100% of the data out to 2θ of 55°. For reasons that are not
8 R. T. Tjahjanto, M. F. Peintinger, T. Bredow and J. Beck,
Eur. J. Inorg. Chem., 2012, 3625.
9 (a) G. H. Robinson and S. A. Sangokara, J. Am. Chem. Soc.,
1988, 110, 1494; (b) G. H. Robinson and J. L. Atwood,
Organometallics, 1987, 6, 887.
clear this did not happen in this case and it proved difficult to 10 K. L. Baker and G. W. A. Fowles, J. Chem. Soc. A, 1968, 801.
obtain more suitable crystals for a re-collection. Judged by the 11 W. Levason, G. Reid and W. Zhang, Dalton Trans., 2011, 40,
high Rint value, the data are of modest quality although the
intensities seems satisfactory (80% exceed the Shelxl test, I > 12 C. Gurnani, M. Jura, W. Levason, R. Ratnani, G. Reid and
2σ(I)). The structure that emerges from the analysis appears M. Webster, Dalton Trans., 2008, 6274.
sound, with no unusual adp values or other causes for 13 K. George, M. Jura, W. Levason, M. E. Light, L. P. Ollivere
concern. For [(AlCl3)2{C6H4(CH2SEt)2}] the diffraction pattern and G. Reid, Inorg. Chem., 2012, 51, 2231.
exhibits many additional reflections in the 100 projection. 14 S. Mishra, E. Jeanneau and S. Daniele, Polyhedron, 2010,
These are likely due to a modulation. In fact, the Ga ana- 29, 500.
logue13 exhibits the same behaviour and in that case it was 15 C. Gurnani, M. Jura, W. Levason, R. Ratnani, G. Reid and
possible to index the modulated cell. As with the Ga analogue, M. Webster, Dalton Trans., 2009, 1611.
the data were indexed on a strong sub-cell making refinement 16 (a) F. Fairbrother and N. Flitcroft, J. Less-Common Met.,
8491.
of the basic structure possible; however, the ignored reflec-
tions result in unrealistic thermal parameters for many of the
1962, 4, 504; (b) C. A. Evans and M. J. Taylor, J. Chem. Soc.
A, 1969, 1343.
atoms. For both of these structures therefore, detailed com- 17 K. George, C. H. de Groot, C. Gurnani, A. L. Hector,
parisons of the geometric parameters require caution.
R. Huang, M. Jura, W. Levason and G. Reid, Chem. Mater.,
2013, 25, 1829.
18 K. Nakamoto, Infrared and Raman spectra of inorganic and
coordination compounds, 4th edn, Wiley, NY, 1986.
19 N. Burford, B. W. Royan, R. E. v. H. Spence and
T. S. Cameron, J. Chem. Soc., Dalton Trans., 1990, 1521.
20 H. Bock and U. Lechner-Knoblauch, J. Organomet. Chem.,
1985, 294, 295.
21 J. Mason, Multinuclear NMR, Plenum, NY, 1987.
22 A. Ecker and H. Schnoeckel, Z. Anorg. Allg. Chem., 1998,
624, 813.
Acknowledgements
We thank the CMSD at STFC and the EPSRC for support, and
Dr M. Webster for assistance with the X-ray data analyses. We
also thank Professor J. M. Dyke for helpful discussions.
23 W. Levason, S. D. Orchard and G. Reid, Coord. Chem. Rev.,
2002, 225, 159.
References
1 Comprehensive organic synthesis, ed. B. M. Tost, Pergamon, 24 N. P. Luthra and J. D. Odon, in The chemistry of organic sel-
Oxford, 1991, e.g. H. Heaney, vol. 2, ch. 3 and G. O. Olah,
enium and tellurium compounds, ed. S. Patai and Z. Rappo-
R. Krishnamurti and G. K. Surya, vol. 4, ch. 1.8.
port, Wiley, NY, 1986, ch. 6, vol. 1.
2 (a) The chemistry of aluminium, gallium, indium and thal- 25 M. Jura, W. Levason, G. Reid and M. Webster, Dalton
lium, ed. A. J. Downs, Blackie, London, 1993; (b) The group Trans., 2009, 7610.
13 metals aluminium, gallium, indium and thallium, ed. 26 B. Cordero, V. Gomez, A. E. Platero-Prats, M. Reeves,
S. Aldridge and A. J. Downs, Wiley, NY, 2011;
J. Eschevaria, E. Cremades, F. Barragan and S. Alvarez,
(c) G. H. Robinson, in Comprehensive Coordination Chem-
Dalton Trans., 2008, 2832.
istry II, ed. J. A. McCleverty and T. J. Meyer, Elsevier, 27 A. Y. Timoshkin, A. V. Suvorov, H. F. Bettinger and
Oxford, 2004, vol. 3, p. 347. H. F. Schaefer III, J. Am. Chem. Soc., 1999, 121, 5687.
3 S. L. Benjamin, W. Levason and G. Reid, Chem. Soc. Rev., 28 A. Ogawa and H. Fujimoto, Inorg. Chem., 2002, 41, 4888.
2013, 42, 1460. 29 F. Bessac and G. Frenking, Inorg. Chem., 2006, 45, 6956.
4 R. L. Richards and A. Thompson, J. Chem. Soc. A, 1967, 30 A. Y. Timoshkin, M. Bodensteiner, T. N. Sevastianova,
1248.
A. S. Lisovenko, E. I. Davydova, M. Scheer, C. Grassl and
A. V. Butlak, Inorg. Chem., 2012, 51, 11602.
31 T. I. Madzhikov and G. A. Chmutova, J. Phys. Chem. A, 2013,
117, 4011.
32 R. J. Batchelor, F. W. B. Einstein, I. D. Gay, J.-H. Gu,
B. D. Johnston and B. M. Pinto, J. Am. Chem. Soc., 1989,
111, 6582.
5 J. Lewis, J. R. Miller, R. L. Richards and A. Thompson,
J. Chem. Soc., 1965, 5850.
6 P. J. Ogren, L. Steenhoek, K. Greve and W. C. Hutton,
J. Inorg. Nucl. Chem., 1975, 37, 293.
7 (a) L. A. Ganyushin, E. N. Guryanova, I. P. Romm and
L. A. Lobanova, Zh. Obshch. Khim., 1979, 49, 2090;
(b) L. A. Ganyushin, E. N. Guryanova and I. P. Romm, Zh. 33 T. Kemmitt and W. Levason, Organometallics, 1989, 8, 1303.
Obshch. Khim., 1978, 48, 2478; (c) I. P. Rom and 34 W. Levason, M. Nirwan, R. Ratnani, G. Reid, N. Tsoureas
E. N. Guryanova, Zh. Obshch. Khim., 1968, 38, 1927.
and M. Webster, Dalton Trans., 2007, 439.
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 3637–3648 | 3647

View Article Online
Paper
Dalton Transactions
35 D. J. Gulliver, E. G. Hope, W. Levason, S. G. Murray, 37 G. M. Sheldrick, SHELXL-97, Program for refinement of
D. M. Potter and G. L. Marshall, J. Chem. Soc., Perkin Trans.
2, 1984, 429.
crystal structures, University of Göttingen, Germany,
1997.
36 N. Kuhn, P. Faupel and E. Zauder, J. Organomet. Chem., 38 G. M. Sheldrick, SHELXS-97, Program for solution of crystal
1986, 302, C4.
structures, University of Göttingen, Germany, 1997.
3648 | Dalton Trans., 2014, 43, 3637–3648
This journal is © The Royal Society of Chemistry 2014