Rationalizing oligomerization in dimethylindium(iii) chalcogenolates (Me2InER′) (E = O, S, Se): A structural and computational study

Article abstract of DOI:10.1039/b927128g

The effect on oligomerization of increased steric bulk in dimethylindium(iii) chalcogenolates (Me₂InER′) (E = O, S, Se) has been examined. The facile reaction of Me₃In with a series of phenols, thiophenols and selenophenols afforded the compounds [Me ₂InO(C₆H₅)]₂ (1), [Me ₂InO(2,6-Me₂C₆H₃)]₂ (2), Me₂InO(2,4,6-tBu₃C₆H₃) (3), [Me ₂InS(C₆H₅)]_∞ (4), [Me ₂InS(2,4,6-tBu₃C₆H₃)] _∞ (6), [Me₂InSe(C₆H₅)] ₂ (7), [Me₂InSe(2,4,6-Me₃C₆H ₃)]_∞ (8) and [Me₂InSe(2,4,6-tBu ₃C₆H₃)]_∞ (9). All compounds have been characterized by elemental analysis, melting point, FT-IR, FT-Raman, solution NMR, and X-ray crystallography. The structures of 1-2 are dimeric via short intermolecular In-O interactions, yielding a symmetric In ₂O₂ unit and a distorted tetrahedral C₂O ₂ bonding environment for indium. Increasing steric bulk in 3 results in the isolation of a monomeric species, exhibiting a distorted trigonal planar C₂O bonding environment for indium. In contrast to 1, the thiolate analogue 4 exhibits a polymeric structure viaμ₂-SPh groups and a distorted tetrahedral C₂S₂ bonding environment for indium. Increasing steric bulk resulted in the formation of a chain of weakly coordinated monomers via intermolecular In...S interactions in [Me ₂InS(2,4,6-tBu₃C₆H₂)] _∞ (6). Although 7 shows a dimeric species similar to 1, the 2,4,6-trimethyl substituted selenolate analogue 8 exhibits a polymeric structure, while the -Se-2,4,6-tBu₃C₆H₃ analogue (9) showing a similar structure to 6. Comparison to previously reported structures of diorganoindium chalcogenolates demonstrates the importance of the methyl substituents on indium in facilitating the isolation of higher (non-dimeric) oligomers. Theoretical calculations demonstrate the significance of altering the R and R′ groups and E on the degree of oligomerization in [R₂InER′]_n species.

Full text of DOI:10.1039/b927128g

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Rationalizing oligomerization in dimethylindium(III) chalcogenolates
(Me2InER¢) (E = O, S, Se): A structural and computational study†
Glen G. Briand,*a Andreas Deckenb and Nathan S. Hamiltona
Received 24th December 2009, Accepted 10th February 2010
First published as an Advance Article on the web 9th March 2010
DOI: 10.1039/b927128g
The effect on oligomerization of increased steric bulk in dimethylindium(III) chalcogenolates
(Me2InER¢) (E = O, S, Se) has been examined. The facile reaction of Me3In with a series of phenols,
thiophenols and selenophenols afforded the compounds [Me2InO(C6H5)]2 (1), [Me2InO(2,6-Me2C6H3)]2
(2), Me2InO(2,4,6-tBu3C6H3) (3), [Me2InS(C6H5)]• (4), [Me2InS(2,4,6-tBu3C6H3)]• (6),
[Me2InSe(C6H5)]2 (7), [Me2InSe(2,4,6-Me3C6H3)]• (8) and [Me2InSe(2,4,6-tBu3C6H3)]• (9). All
compounds have been characterized by elemental analysis, melting point, FT-IR, FT-Raman, solution
NMR, and X-ray crystallography. The structures of 1–2 are dimeric via short intermolecular In–O
interactions, yielding a symmetric In2O2 unit and a distorted tetrahedral C2O2 bonding environment for
indium. Increasing steric bulk in 3 results in the isolation of a monomeric species, exhibiting a distorted
trigonal planar C2O bonding environment for indium. In contrast to 1, the thiolate analogue 4 exhibits
a polymeric structure via m2-SPh groups and a distorted tetrahedral C2S2 bonding environment for
indium. Increasing steric bulk resulted in the formation of a chain of weakly coordinated monomers via
intermolecular In ◊ ◊ ◊ S interactions in [Me2InS(2,4,6-tBu3C6H2)]• (6). Although 7 shows a dimeric
species similar to 1, the 2,4,6-trimethyl substituted selenolate analogue 8 exhibits a polymeric structure,
while the –Se-2,4,6-tBu3C6H3 analogue (9) showing a similar structure to 6. Comparison to previously
reported structures of diorganoindium chalcogenolates demonstrates the importance of the methyl
substituents on indium in facilitating the isolation of higher (non-dimeric) oligomers. Theoretical
calculations demonstrate the significance of altering the R and R¢ groups and E on the degree of
oligomerization in [R2InER¢]n species.
X-ray crystallographic analyses of several examples of R2InER¢
Introduction
compounds have shown that the vast majority of these species
(as well as other group 13 analogues) are dimeric (Chart 1,
n = 2) in the solid-state via very short intermolecular M ◊ ◊ ◊ E
bonding interactions, yielding strongly bonded and symmetric
Semiconducting indium chalcogenide materials (e.g. InE and
In2E3) have been of interest for a number of years due to their
potential applications in switching devices, photovoltaics and non-
linear optics.1 Indium oxide (In2O3), in particular, is a transparent
conducting oxide with a number of applications in thin film
form, such as liquid crystal displays, gas sensors, solar cells, light
emitting diodes and other optoelectronic devices.2 In light of this,
the preparation of thin films of these materials via metal organic
chemical vapor deposition (MOCVD) involving single-source pre-
cursors has been an ongoing area of research.3 Studies into suitable
candidates for such processes have focused on a variety of indium
chalcogenolate species, including diorganoindium chalcogenolates
(R2InER¢) (E = O, S, Se, Te).4,5 It has been demonstrated that
the size and geometry of the precursor molecular core (i.e. the
degree of oligomerization) influences the composition, phase and
morphology of the films formed by MOCVD, as do its volatility
and M to E stoichiometry.
aDepartment of Chemistry and Biochemistry, Mount Allison University,
Sackville, New Brunswick, Canada E4L 1G8. E-mail: gbriand@mta.ca;
Fax: +1 506-364-2313; Tel: +1 506-364-2346
bDepartment of Chemistry, University of New Brunswick, Fredericton, New
Brunswick, Canada E3B 5A3
† CCDC reference numbers 747574–747580. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/b927128g
Chart 1 Schematic drawings of possible oligomers of [R2InER¢]n.
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In2E2 units.6–10 Interestingly, a study of diorganoindium thiolate
analogues (R2InSR¢) produced, in addition to the expected dimeric
species, the trimeric (n = 3) and tetrameric (n = 4) oligomers
[Me2InS-tBu]3 and [Me2InS(2,6-Me2C6H3)]4, respectively.7a These
compounds are the only reported examples of R2InER¢ com-
pounds containing methyl substituents on indium, suggesting
that minimizing steric bulk at indium may permit structural
flexibility in these systems. The possibility of sterically control-
ling the degree of oligomerization in these species, and thus
their physical and thermal decomposition properties, has been
previously proposed.11 However, there has been little in the way
of systematic studies on the effect of the R/R¢ substituents or
the chalcogen (E) on the degree of oligomerization. Therefore,
to probe the effect of altering the steric bulk and the nature
of the chalcogen on the formation of intermolecular bonds and
the degree of oligomerization in dimethylindium chalcogenolates,
we have prepared and structurally characterized the complexes
[Me2InO(C6H5)]2 (1), [Me2InO(2,6-Me2C6H3)]2 (2), Me2InO(2,4,6-
tBu3C6H3) (3), [Me2InS(C6H5)]• (4), [Me2InS(2,4,6-tBu3C6H3)]•
(6), [Me2InSe(C6H5)]2 (7), [Me2InSe(2,4,6-Me3C6H3)]• (8) and
[Me2InSe(2,4,6-tBu3C6H3)]• (9), which incorporate varying de-
grees of steric bulk in the substituted phenylchalcogenolate
ligands (Chart 2). Further, we have probed the thermodynamic
favorability of the various oligomers via theoretical calculations.
route has not been employed previously for the preparation of
R2InSeR¢ analogues.6a,6b,7 The reactions of Me3In with HER¢ in
pentane, hexane, toluene or diethyl ether to yield 1–4 and 6–9
occurred rapidly at room temperature with evolution of methane
gas. All reactions were stirred for 1–18 h and the products were
isolated by slow evaporation or cooling of reaction mixtures.
Although all reactions were quantitative, as determined from 1H
NMR spectra of the reaction mixtures, the reported yields (8–74%)
are of crystalline material obtained from the reaction filtrate.
X-ray structural analyses
Crystals suitable for X-ray crystallographic analysis were isolated
for 1–4 and 6–9 by the slow evaporation of reaction mixtures at
23 ◦C. Crystallographic data is given in Table 1. Selected bond
distances and angles are given in Table 2.
Me2In–OR¢ species. Despite several attempts in various sol-
vents, crystals of Me2In–OPh (1) of sufficient quality for adequate
refinement of X-ray crystallographic data could not be obtained.12
However, preliminary data was sufficient to confirm that the
compound exists as a dimer in the solid state via intermolecular
In ◊ ◊ ◊ O interactions, and exhibits a characteristic In2O2 core and
a distorted tetrahedral C2O2 bonding environment for indium.
Interestingly, the phenyl rings are coplanar with the In2O2 ring.
The structure of [Me2In–O(2,6-Me2C6H3)]2 (2) (Fig. 1) shows an
analogous dimeric structure and a near symmetric In2O2 core
Results and discussion
˚
˚
[In1–O1 = 2.184(2) A, In1–O1* = 2.203(2) A]. In this case,
however, the disubstituted phenyl rings are perpendicular to the
In2O2 core, presumably to minimize steric repulsion. Alternatively,
the X-ray crystallographic analysis of [Me2In–O(2,4,6-tBu3C6H2)]
(3) (Fig. 2) shows the compound to be a monomer in the solid
state, with a C2O distorted trigonal planar bonding environment
Syntheses
The hydrocarbon elimination reaction between R3In and the
corresponding HER¢ is desirable due to its potential general
applicability to (R2InER¢) (E = O, S, Se) systems, as well as the high
reactivity of the trimethylindium species to rapidly yield the more
stable dimethylindium chalcogenolate. Interestingly, this reaction
◦
˚
at indium (R X–In–X = ~359 ). The In–C [In1–C1 = 2.066(19) A,
Chart 2 Schematic drawings of [Me2In-ER¢]n (1–9).
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Table 1 Crystallographic data for 2–4, 6–9
2
3
4
6
7
8
9
Formula
Fw
Crystal system
C20H30O2In2
532.08
Rhombohedral
¯
R3
C20H35OIn
406.30
Monoclinic
P21/m
9.4341 (17)
9.9553 (18)
11.237 (2)
90
101.514 (2)
90
1034.1 (3)
2
424
1.305
1.144
198 (1)
0.71073
0.0562
0.2006
C8H11SIn
254.05
Orthorhombic
Pbca
12.5789 (19)
6.9213 (11)
21.401 (3)
90
C20H35InS
422.36
Monoclinic
P21/c
13.1942 (13)
8.9451 (9)
17.4003 (17)
90
91.973 (1)
90
2052.4 (4)
4
880
1.367
1.250
173 (1)
0.71073
0.0220
0.0558
C16H22Se2In2
601.90
Monoclinic
Pc
10.9188 (15)
11.7444 (17)
7.7891 (11)
90
108.046 (2)
90
949.7 (2)
2
568
2.105
6.250
173 (1)
0.71073
0.0520
0.1264
C11H17SeIn
343.03
Monoclinic
Pca(2)1
22.591 (3)
7.2214 (9)
7.5586 (10)
90
C20H35InSe
469.26
Monoclinic
P21/c
13.226 (3)
9.016 (2)
17.484 (4)
90
92.547 (4)
90
2082.9 (9)
4
952
1.496
2.879
173 (1)
0.71073
0.0430
0.1072
Space group
˚
a/A
27.368 (6)
27.368 (6)
8.447 (2)
90
90
120
5479 (2)
9
2376
1.451
1.901
˚
b/A
˚
c/A
a/◦
b/◦
g /◦
V/A
Z
90
90
90
90
3
˚
1863.2 (5)
8
992
1.811
2.688
198 (1)
0.71073
0.0362
0.0591
1233.1 (3)
4
664
1.848
4.826
198 (1)
0.71073
0.0309
0.0606
F(000)
r
calcd/g cm-3
m/mm-1
T/K
198 (1)
0.71073
0.0522
0.1549
˚
l/A
a
R1
b
wR2
ꢀ
ꢀ
ꢀ
ꢀ
1
2
2
4
2
a R1 = [ ꢀFo|-|Fcꢀ]/[ |Fo|] for [Fo > 2s(Fo2)]. b wR2 = {[ w(Fo -Fc2)2]/[ w(Fo )]} .
◦
˚
Table 2 Selected bond distances (A) and angles ( ) for 2–9
2
3
4
57a
6
7
8
9
In1–C1
In1–C2
In2–C3
In2–C4
In1–E1
In1–E1*
In1–E2
In2–E1
2.137 (4)
2.141 (4)
2.066 (19)
2.110 (15)
2.148 (3)
2.138 (3)
2.159 (8)
2.154 (7)
2.135 (7)
2.134 (8)
2.140 (2)
2.145 (2)
2.178 (18)
2.110 (19)
2.157 (17)
2.130 (18)
2.786 (2)
2.145 (5)
2.142 (5)
2.134 (5)
2.136 (5)
2.184 (2)
2.203 (2)
2.047 (11)
2.6064 (9)
2.6041 (8)
2.5755 (5)
2.8948 (5)
2.7340 (7)
2.7328 (6)
2.6792 (8)
2.9007 (8)
2.602 (2)
2.584 (2)
2.591 (2)
2.581 (2)
131.2 (4)
135.0 (4)
2.712 (2)
2.742 (2)
2.777 (2)
137.7 (7)
138.2 (7)
In2–E2
C1–In1–C2
C3–In2–C4
E1–In1–E1*
E1–In1–E2
E1*–In1–E2
E1–In2–E2
In1–E1–In2
In1–E1–In1*
In1*–E1–In2
In1–E2–In2
131.0 (2)
73.47 (9)
109.3 (8)
133.77 (13)
101.94 (2)
144.30 (9)
137.5 (2)
143.6 (2)
124.240 (8)
111.154 (15)
119.07 (2)
92.61 (7)
90.03 (6)
92.82 (6)
92.16 (7)
87.19 (6)
106.53 (10)
108.54 (3)
139.764 (18)
120.274 (19)
144.16 (2)
130.47 (7)
123.3 (3)
88.00 (7)
Fig. 1 X-ray structure of 2 (50% probability ellipsoids). Hydrogen atoms
are not shown for clarity. Symmetry transformations used to generate
equivalent atoms: (*) -x+1, -y+2, -z.
Fig. 2 X-ray structure of 3 (50% probability ellipsoids). Hydrogen atoms
are not shown for clarity.
6
˚
˚
˚
˚
In1–C2 = 2.110(15) A] and In–O [In1–O1 = 2.047(11) A] bond
distances are significantly shorter that those of 2 and previ-
ously reported dimeric [R2In–OR¢]2 analogues [In–C 2.206(18)–
2.219(12) A; In–O 2.118(2)–2.185(4) A], which is expected given
the three coordinate bonding environment for indium in 3. The
nearest In ◊ ◊ ◊ O distance is >9.5 A and well outside of the sum of
˚
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the metallic/van der Walls radii (3.07 A).13 This represents the first
˚
example of a monomeric R2In–OR¢ complex and a rare example
of a monomeric R2M–ER¢ (M = B, Al, Ga, In, Tl) complex.14
Me2In–SR¢ species. X-ray crystallographic analysis of
[Me2InS(C6H5)]• (4) (Fig. 3) shows the compound to be a
polymer in the solid state via bridging m2-SPh groups, giving
a four coordinate C2S2 bonding environment and a distorted
˚
tetrahedral geometry at indium. In–C [In1–C1 = 2.148(3) A,
˚
˚
In1–C2 = 2.138(3) A] and In–S [In1–S1 = 2.6064(9) A, In1–
˚
S1* = 2.6041(8) A] bond distances are within the range of those
of previously reported oligomeric complexes [In–C = 2.137(12)–
7,8
˚
˚
2.23(1) A; In–S = 2.562(4)–2.651(2) A]. Not surprisingly, both
the S1–In1–S1* [101.94(2)◦] and In1–S1–In1* [108.54(3)◦] bond
angles of 4 are significantly larger than those observed for dimeric
[R2In–SR¢]2 complexes. Interestingly, however, the S–In–S bond
angle is significantly larger and the In–S–In bond angle is signifi-
cantly smaller than those observed for the trimeric and tetrameric
complexes [Me2In–S-tBu]3 and [Me2In–S(2,6-Me2C6H3)]4 (5) [S–
In–S: 90.03(6)–96.89(11)◦; In–S–In 109.39(12)–130.47(7)◦].7a As
in most R2In–SR¢ complexes, the In–S bond distances in 4 are
not significantly different and each thiolate group is equally
associated with two neighbouring In atoms. A monomeric unit
cannot be distinguished. Interestingly, the phenyl groups are all
located on one side of the [–In–S–]• chain in an isotactic-type
arrangement, while all dimeric R2InSR ‘show thiolate R’ groups
in trans positions in the solid state.7,8
Fig. 4 X-ray structure of 6 (E = S) and 9 (E = Se) (50% probability
ellipsoids). Hydrogen atoms are not shown for clarity. Symmetry trans-
formations used to generate equivalent atoms: (*) -x+1, y+12 , -z+ 21 ; (**)
-x+1, y-12 , -z+ 12 .
Fig. 3 X-ray structure of 4 (50% probability ellipsoids). Hydrogen atoms
are not shown for clarity. Symmetry transformations used to generate
equivalent atoms: (*) -x+ 12 , y+21 , z; (**) -x+21 , y-12 , z.
The structure of [Me2In–S(2,4,6-tBu2C6H3)]• (6) (Fig. 4) shows
a polymeric structure via m2-S(2,4,6-tBu2C6H3) groups, similar to
4. In this case, however, the In–S bond distances are significantly
Fig. 5 X-ray structure of 7 (50% probability ellipsoids). Hydrogen atoms
are not shown for clarity.
˚
˚
different [In1–S1 = 2.5755(5) A, In1–S1* = 2.8948(5) A], with
In1–S1 being within the expected range and In1–S1* being ~0.2–
˚
for indium. In–C bond distances [2.110(19)–2.178(18) A] are
◦
˚
0.3 A longer. Further, the sum of the C1–In1–C2 [144.30(9) ],
C1–In1–S1 [105.57(7)◦] and C2–In1–S1 [102.53(6)◦] bond angles
is ~352◦. This suggests a distorted trigonal planar C2S bonding
environment at In, similar to that observed in 3, with a weak
intermolecular In…S interaction [sum of metallic/van der Waals
similar to those observed in previously reported dimeric analogues
[In–C = 2.16(2)–2.22(3) A].8b,9 However, the In–Se bond distances
˚
˚
in the dimer [In1–Se1 = 2.786(2) and In1–Se2 = 2.712(2) A;
˚
In2–Se1 = 2.742(2) and In2–Se2 = 2.777(2) A] are significantly
different when esd values are considered, with the longer distances
being outside of the range of those previously reported [In–Se =
2.699(7)–2.756(1)].8b,9 The differences are relatively small, however,
and the compound can be considered a strongly bonded dimer.
X-ray crystallographic analysis of [Me2InSe(2,4,6-Me3C6H2)]•
(8) (Fig. 6) shows the compound to be a polymer in the solid
state via bridging m2-Se(2,4,6-Me3C6H2) groups, giving a four
radii = 3.52 A].13 The polymeric structure may therefore be viewed
˚
as being composed of weakly associated monomers.
Me2In–SeR¢ species. The structure of [Me2InSe(C6H5)]2 (7)
(Fig. 5) shows the compound to be a dimer in the solid state via
intermolecular In ◊ ◊ ◊ Se interactions, and exhibits a characteristic
In2Se2 core and a distorted tetrahedral C2Se2 bonding environment
3836 | Dalton Trans., 2010, 39, 3833–3841
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identity of E, on the relative energies of [R2InER¢]n (n = 1–4)
systems. The geometry optimized structures resemble those of the
corresponding oligomers in the solid solid-state, i.e. monomeric
compounds show structures similar to [Me2InO(tBu3C6H2)] (3),
dimeric compounds contain planar symmetric In2E2 rings and
ligand arrangements similar to [Me2InO(2,6-Me2C6H3)] (2) and
[tBu2InStBu]2, while trimeric and tetrameric compounds show
puckered rings and ligand arrangements similar to [Me2InStBu]3
and [Me2InS(Me2C6H3)]4 (5), respectively. Representative struc-
tures are shown in Fig. 7. The resulting electronic energy of the
geometry optimized structures was divided by n to yield an energy
per monomer (E/n) value, which could be directly compared to
values for corresponding oligomers (i.e. those containing similar
R, R¢ and E groups). Results are presented in Table 3.
Fig. 6 X-ray structure of 8 (50% probability ellipsoids). Hydrogen atoms
are not shown for clarity. Symmetry transformations used to generate
equivalent atoms: (*) -x, -y, z-12 ; (**) -x, -y, z+ 21 .
coordinate C2Se2 bonding environment and a distorted tetrahedral
˚
geometry at indium. In–C [In1–C1 = 2.145(5) A, In1–C2 =
˚
˚
2.142(5) A] and In–Se [In1–Se1 = 2.7340(7) A, In1–Se1* =
˚
2.7328(6) A] bond distances are within the range of those of
previously reported dimeric complexes. Not surprisingly, both
the Se1–In1–Se1* [111.154(15)◦] and In1–Se1–In1* [120.274(19)◦]
bond angles of 8 are significantly larger than those observed for
dimeric [R2In–SeR¢]2 complexes [Se–In–Se 81.7(1)–94.06(4)◦; In–
Se–In 85.94(4)–98.3(1)◦].8,9 Like 4, the In1–E1 and In1–E1* bond
distances in 8 are not significantly different and each selenolate
group is equally associated with two neighbouring In atoms.
Unlike 4, however, the (2,4,6-Me3C6H2) groups alternate along
the [–In–Se–]• chain in a syndiotactic-type arrangement.
The structure of [Me2InSe(2,4,6-tBu2C6H3)]• (9) (Fig. 4) is
isostructural with that of 6, and shows a polymeric structure via
m2-Se(2,4,6-tBu2C6H3) groups. As in 6, the In–Se bond distances
Fig. 7 Geometry optimized structures of [Me2InStBu]n (n = 1, 2, 3
and 4).
˚
are significantly different [In1–Se1 = 2.6792(8) A, In1–Se1* =
˚
Energies for the monomeric systems (n = 1) were found to
be the largest for each compound, due to the absence of the
extra intermolecular In–E bonding contacts found when n =
2–4 (see Chart 1). For [Me2InOMe]n, which contain minimal
steric bulk at In and O, the E/n value is lowest for n = 2
and increases significantly for higher oligomers. This suggests
a strong preference for dimeric structures when E = O, and is
consistent with observed structural data. Interestingly, E/n values
for the corresponding thiolate systems (i.e. [Me2InSMe]n) show
the opposite trend, with the tetramer value being the lowest. This
suggests that the [–In–S–]n ring structure is sufficiently flexible to
accommodate ring strain, and that there is potential for higher
(n > 2) degrees of oligomerization, as has been observed for 4–6
and other reported structures.7a
2.9007(8) A], with In1–Se1 being within the expected range and
8b,9
˚
In1–Se1* being ~0.2 A longer [sum of metallic/van der Waals
radii = 3.67 A]. In this case, however, the percentage difference
13
˚
in In–E (8%) is not great as that of 6 (12%), suggesting a stronger
secondary interaction and a more tightly bonded polymer. This
is presumably a result of the larger atomic radius of Se versus
S. Furthermore, the sum of the C1–In1–C2 [143.6(2)◦], C1–In1–
Se1 [105.82(18)◦] and C2–In1–Se1 [102.10(16)◦] bond angles is
~352◦. This suggests a distorted trigonal planar C2Se bonding
environment at In, similar to that observed in 3, with a weak
intermolecular In ◊ ◊ ◊ Se interaction. The polymeric structure may
therefore be viewed as being composed of weakly associated
monomers.
Given the strong preference for dimerization in E = O systems
and the observed structural flexibility in the E = S analogues,
the remainder of this computational study focused on thiolate
oligomers. First, the effect of varying the organic group at indium
(R) was studied in [R2InSMe]n [R = Me, Ph, tBu, (2,6-Me2C6H3);
n = 1–4]. For [Ph2InSMe]n, a similar trend as for [Me2InSMe]n
Computational studies
Given the varying degrees of oligomerization observed in 1–9, and
the vast majority of dimeric [R2InER¢]2 structures observed in the
literature, a computational study was undertaken to determine
the effect of varying the steric bulk of R and R¢, and the
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Dalton Trans., 2010, 39, 3833–3841 | 3837
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Table 3 Calculated energies for geometry optimized [R2InER¢]n species (E/n in parentheses) (kJ mol-1)
E
R
R¢
n = 1
n = 2
n = 3
n = 4
O
S
S
S
S
S
S
S
S
Me
Me
Ph
tBu
Me
Me
Me
Me
Me
Ph
tBu
2,6-Me2C6H3
2,6-tBu3C6H2
148 (148)
223 (223)
789 (789)
504 (504)
943 (943)
534 (534)
427 (427)
638 (638)
1046 (1046)
97.0 (48.5)
180 (90.0)
1342 (671.0)
756 (378)
1744 (872.0)
819 (410)
599 (299)
1015 (507.5)
1938 (969.0)
207 (69.0)
262 (87.3)
294 (73.5)
343 (85.8)
2008 (669.3)
1146 (382.0)
2683 (894.3)
1221 (407.0)
916 (305)
1569 (523.0)
2953 (984.3)
2675 (668.8)
1544 (386.0)
3641 (910.3)
1663 (415.8)
1242 (310.5)
2092 (523.0)
3959 (989.8)
2,6-Me2C6H3
Me
Me
Me
Me
is observed. However, introducing steric bulk at indium (R =
tBu, 2,6-Me2C6H3) results in an increase in the E/n values for
higher oligomers, with the R = 2,6-Me2C6H3 compounds showing
the steepest increase. Further, [(2,6-Me2C6H3)2InSMe] shows the
smallest decrease in energy on dimerization (71 kJ mol-1), as
compared to 118 and 126 kJ mol-1 for R = Ph and tBu. This
suggests that an increase in steric bulk at In leads to a more highly
strained system and less favorable dimeric structure. These results
correspond to what has been observed in previously reported
structures, where all R = tBu, Np and Mes (Np = neopentyl,
Mes = 2,4,6-Me3C6H2) systems are dimeric (no R = Ph structures
have been reported).
Finally, varying steric bulk at the thiolate group (R¢) was studied
in [Me2InSR¢]n [R¢ = Me, Ph, tBu, (2,6-Me2C6H3); n = 1–4]. As
with the [R2InSMe]n (R = tBu, 2,6-Me2C6H3) systems, a general
increase in E/n is observed with higher oligomers for all systems.
Interestingly, however, the R¢ = Ph systems show the lowest value
for the trimer (n = 3), while the n = 3 and 4 structures show similar
values when R¢ = 2,6-Me2C6H3. Again, the sharpest increases
in energy with increasing n are for the bulkiest groups, with the
Me2InS(2,6-tBu3C6H2) showing the smallest decrease in energy on
dimerization (77 kJ mol-1) versus 124–130 kJ mol-1 for R¢ = Ph,
tBu and 2,6-Me2C6H3. Overall, these results support the observed
formation of higher oligomers for [Me2InSR¢] systems, particular
with small to intermediate sized R¢ groups.
explore intermolecular indium chalcogen bonding interactions, we
are currently undertaking further structural and computational
studies on oligomeric diorganoindium chalcogenolate species.
Experimental
General Considerations
Phenol (≥99.0%), 2,6-dimethylphenol (99%), 2,4,6-tri-tert-
butylphenol (99%), thiophenol (≥99%), benzene selenol (97%),
elemental sulfur (>99.5%), elemental selenium (>99%), 2,4,6-
trimethylphenylmagnesium bromide (1.0 M in diethyl ether), 1-
bromo-2,4,6-tri-tert-butylbenzene (97%), n-butyl lithium (1.6 M
solution in hexanes) and anhydrous pentane (>99%), were used
as received from Sigma-Aldrich. InMe3 was used as received
from Strem. 2,4,6-trimethylbenzeneselenol was prepared via a
modified literature procedure, as described below.15 2,4,6-tri-
tert-butylbenzenethiol and 2,4,6-tri-tert-butylbenzeneselenol were
prepared via literature methods.16 Hexane, toluene and diethyl
ether were dried using an MBraun SPS column solvent purification
system. Despite several attempts in various deuterated solvents,
the poor solubility of compounds 6 precluded collection of useful
1
solution 13C{ H} data.
Instrumentation
Solution 1H, 13C{ H} and 77Se NMR were recorded at 23 ◦C
1
on either a JEOL GMX 270 MHz + spectrometer (270, 67.9
and 109.4 MHz, respectively), or a Varian Mercury 200 MHz +
Conclusions
1
spectrometer (200 and 50 MHz; 1H and 13C{ H}, respectively), and
The effect on oligomerization of increased steric bulk in
dimethylindium(III) chalcogenolates (Me2InER¢) (E = O, S, Se)
has been examined. The structures of 1 and 2 are dimeric via short
intermolecular In–O interactions, while increasing steric bulk in
3 results in the isolation of a monomeric species. In contrast
to 1, compound 4 exhibits a polymeric structure via m2–SPh
groups, while the S(2,4,6-tBu3C6H3) analogue (6) shows a similar
polymeric species to 3, but is composed of weakly associated
monomeric units. Although 7 shows a dimeric species similar
to 1, the Se(2,4,6-Me3C6H3) analogue (8) exhibits a polymeric
structure, while the Se(2,4,6-tBu3C6H3) analogue (9) shows a
similar polymeric species to 6. This variation in oligomeriza-
tion highlights the significance of the methyl substituents on
indium in permitting higher (non-dimeric) oligomers in the E =
S and Se structures. This is further supported by theoretical
studies, which demonstrate the importance of the chalcogen
(i.e. E = O versus S) and significance of altering the R and R¢ groups
in [R2InSR¢]n species on the degree of oligomerization. To further
are calibrated to the residual solvent signal. Infrared spectra were
recorded as Nujol mulls on a Mattson Genesis II FT-IR spectrom-
eter in the range 4000–400cm-1. Melting points were recorded on
an Electrothermal MEL-TEMP melting point apparatus and are
uncorrected. Elemental analyses were performed on an elementar
vario ELIII universal CHNOS analyzer, or were performed by
Chemisar Laboratories Inc., Guelph, Ontario. All reactions were
performed under an atmosphere of inert dinitrogen using standard
Schlenk techniques.
Electron impact mass spectrometry (EI-MS) data were collected
after direct insertion of the solid sample from a 1177 injection port
on the Varian 3800◦GC using a Varian Saturn MS/MS. An initial
temperature of 35 C was held for 3.5 min, ramped at a rate of
10 ◦C min-1 to 300 ◦C, and held for 5 min, for a total of 35 min.
Spectra were collected in the range of m/z 50–650 at 70 eV.
Preparation of [Me2InO(C6H5)]2 (1). C6H5OH (0.176 g,
1.88 mmol) was added to a solution of InMe3 (0.300 g, 1.88 mmol)
3838 | Dalton Trans., 2010, 39, 3833–3841
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in hexane (15 mL). The solution was stirred for 1 h, followed
by filtration. The filtrate was allowed to sit at 23 ◦C. After
1 d, the solution was filtered to yield colorless crystals of 1
(0.173 g, 0.727 mmol, 39%). Anal. Calcd for C16H22O2In2: C,
40.51; H◦, 4.64; N, 0.00. Found: C, 40.83; H, 4.73; N, <0.10.
Mp 102 C. FT-IR (cm-1): 622 m, 684 w, 724 w, 756 w, 836 m,
866 w, 992 w, 1022 w, 1076 m, 1103 w, 1150 w, 1244 w, 1579 s.
FT-Raman (cm-1): 115 m, 140 m, 182 m, 252 w, 491 vs, 537 w,
580 vw, 623 vw, 753 vw, 847 w, 994 m, 1028 m, 1165 m, 1263
w, 1331 vw, 1448 vw, 1590 m, 2928 m, 2995 w, 3026 w, 3048
137.7 [s, Me2InO(2,4,6-tBu3C6H2)], 138.2 [s, Me2InO(2,4,6-
tBu3C6H2)], 161.2 [s, Me2InO(2,4,6-tBu3C6H2)]. EI-MS (m/z):
248 [HO-2,4,6-tBu3C6H2]∑+.
Preparation of [Me2InS(C6H5)]n (4). C6H5SH (0.207 g,
1.88 mmol) was added to a solution of InMe3 (0.300 g, 1.88 mmol)
in ether (15 mL). The solution was stirred for 3 h, then concen-
trated to 8 mL, followed by filtration. After sitting for 1 d at 23 ◦C,
the solution was filtered to yield colorless crystals of 4 (0.217 g,
0.858 mmol, 46%). Anal. Calcd for C8H11SIn: C, 37.83; H, 4.33;
N, 0.00. Found: C, 37.40; H, 3.92; N, <0.10. Mp 98 ◦C. FT-
IR (cm-1): 688 m, 723 s, 901 vw, 1022 w, 1080 w, 1153 w, 1261
w, 1300 vw, 1574 w. FT-Raman (cm-1): 118 s, 137 s, 153 s, 170
m, 194 m, 251 vw, 278 vw, 321 vw, 422 vw, 485 vs, 522 m, 616
w, 695 w, 1002 s, 1024 m, 1081 m, 1118 w, 1154 m, 1181 w,
1438 w, 1577 m, 2540 vw, 2595 vw, 2924 m, 2985 m, 3018 vw,
3063 s, 3145 w. Solution NMR data (toluene-d8): 1H NMR, d =
0.12 [s, 6H, Me2InS(C6H5)], 6.89 [d, 1H, Me2InS(C6H5)], 6.93 [t,
1
m, 3060 m. Solution NMR data (benzene-d6): H NMR, d =
0.00 [s, 6H, Me2InO(C6H5)], 6.64 [m, 2H, Me2InO(C6H5)], 6.80
1
[m, 2H, Me2InO(C6H5)], 7.08 [m, 2H, Me2InO(C6H5)]. 13C{ H}
NMR, d = -3.5 [s, Me2InO(C6H5)], 118.2 [s, Me2InO(C6H5)],
119.6 [s, Me2InO(C6H5)], 129.9 [s, Me2InO(C6H5)], 159.9 [s,
Me2InO(C6H5)]. EI-MS (m/z): 94 [HOC6H5]∑+, 145 [Me2In]∑+, 476
[dimer]∑+.
Preparation of [Me2InO(2,6-Me2C6H3)]2 (2). 2,6-Me2C6H3OH
(0.230 g, 1.88 mmol) was added to a solution of InMe3 (0.300 g,
1.88 mmol) in hexane (15 mL). The solution was stirred for 1 h,
followed by filtration. The solution was allowed to sit at 23 ◦C for 1
d, and filtered to yield colorless crystals of 2 (0.195 g, 0.81 mmol,
43%). Anal. Calcd for C20H30O2In2: C, 45.28;◦H, 5.66; N, 0.00.
Found: C, 45.33; H, 6.49; N, <0.10. Mp 180 C. FT-IR (cm-1):
582 w, 723 s, 762 m, 845 s, 893 vw, 916 vw, 970 w, 1020 w,
1093 m, 1157 w, 1203 m, 1259 m, 1589 m. FT-Raman (cm-1):
119 m, 141 m, 167 m, 241 w, 314 w, 487 s, 527 m, 556 vw, 695
w, 978 vw, 1095 w, 1157 m, 1264 w, 1377 w, 1445 vw, 1591 w,
2872 w, 2923 m, 2999 w. Solution NMR data (chloroform-d):
1H NMR, d = -0.34 [s, 6H, Me2InO(2,6-Me2C6H3)], 2.27 [s,
6H, Me2InO(2,6-Me2C6H3)], 6.92 [d, 2H, Me2InO(2,6-Me2C6H3)],
1
2H, Me2InS(C6H5)], 7.29 [d, 2H, Me2InS(C6H5)]. 13C{ H} NMR,
d = -3.5 [s, Me2InS(C6H5)], 126.1 [s, Me2InS(C6H5)], 128.9 [s,
Me2InS(C6H5)], 132.9 [s, Me2InS(C6H5)], 133.2 [s, Me2InS(C6H5)].
EI-MS (m/z): 110 [HSC6H5]∑+, 115 [In]∑+, 145 [Me2In]∑+.
Preparation
of
[Me2InS(2,4,6-tBu3C6H2)]
(6). 2,4,6-
tBu3C6H2SH (0.250 g, 0.898 mmol) was added to a solution of
InMe3 (0.146 g, 0.898 mmol) in toluene (8 mL). The solution
was stirred for 1 h, then filtered and concentrated to 1 mL. The
solution was filtered to yield colorless crystals of 6 (0.031 g,
0.0734 mmol, 8%). Anal. Calcd for C20H35SIn: C, 56.87; H, 8.35;
N, 0.00. Found: C, 56.68; H, 8.59; N, <0.10. Mp 250(d) ◦C. FT-IR
(cm-1): 647 w, 693 w, 724 s, 877 m, 923 w, 1018 w, 1158 w, 1213
m, 1240 m, 1260 w, 1363 s, 1410 w, 1549 vw, 1594 m. FT-Raman
(cm-1): 139 s, 172 s, 255 m, 417 w, 488 s, 517 m, 565 m, 641 vw,
750 vw, 766 vw, 823 m, 926 m, 1003 w, 1028 w, 1133 m, 1158
m, 1179 m, 1201 m, 1244 w, 1285 w, 1363 vw, 1392 w, 1448 m,
1594 m, 2708 w, 2776 w, 2904 vs, 2922 vs, 2960 vs. Solution
1
6.99 [s, 1H, Me2InO(2,6-Me2C6H3)]. 13C{ H} NMR, d = 18.9 [s,
Me2InO(2,6-Me2C6H3)], 19.1 [s, Me2InO(2,6-Me2C6H3)], 121.6 [s,
Me2InO(2,6-Me2C6H3)], 129.9 [s, Me2InO(2,6-Me2C6H3)], 130.0
[s, Me2InO(2,6-Me2C6H3)], 154.9 [s, Me2InO(2,6-Me2C6H3)]. EI-
MS (m/z): 77 [C6H5]∑+, 115 [In]∑+, 122 [HO-2,6-Me2C6H3]∑+, 145
[Me2In]∑+, 476 [dimer]∑+.
1
NMR data (thf-d8): H NMR, d = -0.46 [s, 6H, Me2InS(2,4,6-
tBu3C6H2)], 1.29 [m, 9H, Me2InS(2,4,6-tBu3C6H2)], 1.60 [s, 18H,
Me2InS(2,4,6-tBu3C6H2)], 7.25 [s, 2H, Me2InS(2,4,6-tBu3C6H2)].
EI-MS (m/z): 277 [HS-2,4,6-tBu3C6H2]∑+.
Preparation
of
[Me2InO(2,4,6-tBu3C6H2)]
(3). 2,4,6-
tBu3C6H2OH (0.492 g, 1.88 mmol) was added to a solution
of InMe3 (0.300 g, 1.88 mmol) in pentane (15 mL). The solution
was stirred for 1 h, followed by filtration, and allowed to sit at
23 ◦C for 1 d. The colorless solution was then concentrated to
8 mL, and allowed to sit for 2 d at 23 ◦C. The solution was
then filtered to yield colorless crystals of 3 (0.560 g, 1.38 mmol,
74%). Anal. Calcd for C20H35OIn: C, 59.26; ◦H, 8.64; N, 0.00.
Found: C, 58.80; H, 8.59; N, <0.10. Mp 88 C. FT-IR (cm-1):
639 vw, 690 w, 728 w, 787 w, 810 m, 880 s, 963 w, 1025 vw, 1057
w, 1115 m, 1149 w, 1192 w, 1221 m, 1266 w, 1287 w, 1581 w,
1621w. FT-Raman (cm-1): 135 s, 174 vs, 258 w, 310 w, 487 m, 515
vs, 561 w, 766 vw, 807 vw, 824 w, 862 w, 931 w, 1109 vw, 1174
m, 1201 w, 1462 w, 1598 vw, 1664 m, 1840 vw, 2114 vw, 2608
vw, 2714 vw, 2852 w, 2929 vs, 2961 s, 3632 vw. Solution NMR
data (chloroform-d): 1H NMR, d = -0.15 [s, 6H, Me2InO(2,4,6-
tBu3C6H2)], 1.35 [s, 9H, Me2InO(2,4,6-tBu3C6H2)], 1.41 [s, 18H,
Me2InO(2,4,6-tBu3C6H2)], 7.16 [s, 2H, Me2InO(2,4,6-tBu3C6H2)].
Preparation of [Me2InSe(C6H5)]2 (7). A solution of C6H5SeH
(0.295 g, 1.88 mmol) in toluene (10 mL) was added drop-wise to a
solution of InMe3 (0.300 g, 1.88 mmol) in toluene (15 mL). The so-
lution was stirred for 1 h, and then concentrated to 12 mL, followed
by filtration. The clear colorless solution was then layered with
hexane (12 mL) and allowed to sit at 4 ◦C. After 2 d, the solution
was filtered to yield 7 as colorless crystals (0.265 g, 0.882 mmol,
47%). Anal. Calcd for C16H22Se2In2: C, 31.91;◦H, 3.66; N, 0.00.
Found: C, 31.66; H, 3.59; N, <0.10. Mp 120 C. FT-IR (cm-1):
685 m, 725 s, 772 m, 846 vw, 891 w, 961 w, 1018 w, 1065 w, 1156
m, 1572 w, 1622 w. FT-Raman (cm-1): 111 s, 159 vs, 196 s, 207 s,
250 w, 305 w, 406 vw, 504 s, 615 w, 667 w, 1000 vs, 1022 m, 1067 m,
1136 m, 1155 w, 1179 w, 1436 vw, 1573 m, 2929 w, 2993 w, 3013 w,
3055 s, 3141 w. Solution NMR data (benzene-d6): 1H NMR, d =
0.50 [s, 6H, Me2InSe(C6H5)], 6.70 [d, 2H, Me2InSe(C6H5)], 6.99
1
13C{ H} NMR, d = 0.4 [s, Me2InO(2,4,6-tBu3C6H2)], 31.9 [s,
1
Me2InO(2,4,6-tBu3C6H2)], 34.4 [s, Me2InO(2,4,6-tBu3C6H2)], 35.4
[s, Me2InO(2,4,6-tBu3C6H2)], 121.9 [s, Me2InO(2,4,6-tBu3C6H2)],
[d, 2H, Me2InSe(C6H5)], 7.33 [d, 2H, Me2InSe(C6H5)]. 13C{ H}
NMR, d = 32.8 [s, Me2InSe(C6H5)], 128.6 [s, Me2InSe(C6H5)],
Dalton Trans., 2010, 39, 3833–3841 | 3839
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130.0 [s, Me2InSe(C6H5)], 132.3 [s, Me2InSe(C6H5)], 138.5 [s,
Me2InSe(C6H5)]. EI-MS (m/z): 115 [In]∑+, 145 [Me2In]∑+.
32.6 [s, Me2InSe(2,4,6-tBu3C6H2)], 34.7 [s, Me2InSe(2,4,6-
tBu3C6H2)], 38.7 [s, Me2InSe(2,4,6-tBu3C6H2)], 122.2 [s,
Me2InSe(2,4,6-tBu3C6H2)], 148.2 [s, Me2InSe(2,4,6-tBu3C6H2)],
153.9 [s, Me2InSe(2,4,6-tBu3C6H2)]. EI-MS (m/z): 326 [HSe-
2,4,6-tBu3C6H2]∑+.
Preparation of [(2,4,6-Me3C6H2)SeH]. 2,4,6-Me3C6H2MgBr
(38.0 mL, 1 M solution in ether, 38.0 mmol) was added drop-
wise to a solution of elemental Se (3.99 g, 38.0 mmol) in ether
(25 mL). The solution was stirred for 3 h. HCl (40 mL, 3 M)
was then added dropwise, and stirred for 0.5 h. The ether layer
was decanted and concentrated to 15 mL. Distillation of the
orange oil under reduced pressure at 52–54 ◦C yield a clear, pale
yellow liquid [(2,4,6-Me3C6H2)SeH] (1.51 g, 7.99 mmol, 21%).
X-ray Structural Analysis
Crystals of 1–4 and 6–9 were isolated from the reaction mixtures
as indicated above. Single crystals were coated with Paratone-N
oil, mounted using a polyimide MicroMount and frozen in the
cold nitrogen stream of the goniometer. A hemisphere of data
was collected on a Bruker AXS P4/SMART 1000 diffractometer
using w and q scans with a scan width of 0.3◦, and 10 s (3, 6, 8, 9)
or 30 s (2, 4, 7) exposure times. The detector distance was 5 cm.
The crystals of 2 and 9 were twinned and the orientation matrixes
for two components in each were determined (CELL_NOW).17
For 3, the molecule was disordered over two sites with equal
occupancies. The data were reduced (SAINT)18 and corrected
for absorption [TWINABS19 (2, 9), SADABS20 (3, 4, 6–8)]. The
structure was solved by direct methods and refined by full-matrix
least squares on F2(SHELXTL).21 All non-hydrogen atoms were
refined using anisotropic displacement parameters. Hydrogen
atoms were included in calculated positions and refined using a
riding model. Lattice solvent (hexane) in 2 could not be modelled
properly.
1
Solution NMR data (benzene-d6): H NMR, d = 2.01 [s, 1H,
(2,4,6-Me3C6H2)SeH], 2.12 [s, 6H, (2,4,6-Me3C6H2)SeH], 2.15
[s, 3H, (2,4,6-Me3C6H2)SeH], 6.66 [s, 2H, (2,4,6-Me3C6H2)SeH].
1
13C{ H} NMR, d = 21.0 [s, (2,4,6-Me3C6H2)SeH], 24.1 [s, (2,4,6-
Me3C6H2)SeH], 135.2 [s, (2,4,6-Me3C6H2)SeH], 137.3 [s, (2,4,6-
Me3C6H2)SeH], 138.2 [s, (2,4,6-Me3C6H2)SeH]. 77Se NMR, d =
26.9 [d, (2,4,6-Me3C6H2)SeH, 1J(77Se-1H) = 120 Hz].
Preparation of [Me2InSe(2,4,6-Me3C6H2)]n (8). A solution of
2,4,6-Me3C6H2SeH (0.355 g, 1.88 mmol) in hexane (5 mL) was
added drop-wise to a solution of InMe3 (0.300 g, 1.88 mmol) in
hexane (15 mL). The mixture was stirred for 1 h, followed by
◦
filtration, and then allowed to sit at 23 C for 1 d. The colorless
solution was then concentrated to 10 mL, and allowed to sit at
◦
23 C. After 1 d, the solution was filtered to yield 8 as colorless
crystals (0.212 g, 0.62 mmol, 33%). Anal. Calcd for C11H17SeIn:
C, 38.51;◦H, 4.96; N, 0.00. Found: C, 38.35; H, 5.15; N, <0.10.
Mp 180 C. FT-IR (cm-1): 721 s, 850 s, 1016 m, 1157 w, 1269
w, 1298 vw, 1599 w. FT-Raman (cm-1): 121 s, 169 m, 333 w,
482 vs, 524 w, 539 w, 562 m, 591 w, 704 vw, 1019 w, 1097 vw,
1157 m, 1296 m, 1378 w, 1456 vw, 1570 vw, 1599 m, 2727 w,
2849 w, 2914 m, 2982 m. Solution NMR data (chloroform-d):
1H NMR, d = 0.08 [s, 6H, Me2InSe(2,4,6-Me3C6H2)], 2.24 [s, 3H,
Me2InSe(2,4,6-Me3C6H2)], 2.39 [s, 6H, Me2InSe(2,4,6-Me3C6H2)],
Computational methods
Semi-empirical calculations were performed using Gaussian 03 at
the PM3 level. All structures were geometry optimized and struc-
tural parameters for input files were derived from crystal structure
data where possible. Frequency calculations were performed on
all structures and gave no imaginary frequencies. Energy values
reported are the electronic energy values corrected for zero-point
energies derived from frequency calculations.
1
6.88 [s, 2H, Me2InSe(2,4,6-Me3C6H2)]. 13C{ H} NMR, d = 15.3 [s,
Me2InSe(2,4,6-Me3C6H2)], 20.8 [s, Me2InSe(2,4,6-Me3C6H2)], 26.2
[s, Me2InSe(2,4,6-Me3C6H2)], 125.9 [s, Me2InSe(2,4,6-Me3C6H2)],
136.2 [s, Me2InSe(2,4,6-Me3C6H2)], 141.3 [s, Me2InSe(2,4,6-
Me3C6H2)]. 77Se NMR, d = 31.7 [s, Me2InSe(2,4,6-Me3C6H2)].
EI-MS (m/z): 115 [In]∑+, 145 [Me2In] ∑+, 199 [Se-2,4,6-Me3C6H2]∑+.
Acknowledgements
We thank the following: Dan Durant for assistance in collecting
solution NMR data; Dr Stephen Duffy and Martin Wightman for
assistance in collecting mass spectrometry data; and the Natural
Sciences and Engineering Research Council of Canada, the New
Brunswick Innovation Foundation, the Canadian Foundation for
Innovation and Mount Allison University for financial support.
Preparation
of
[Me2InSe(2,4,6-tBu3C6H2)]
(9). 2,4,6-
tBu3C6H2SeH (0.250 g, 0.768 mmol) was added to a solution of
InMe3 (0.123 g, 0.768 mmol) in toluene (8 mL). The solution
was stirred for 1 h, then filtered and concentrated to 1 mL. The
solution was filtered to yield colorless crystals of 9 (0.169 g,
0.360 mmol, 47%). Anal. Calcd for C20H35SeIn: C, 51.1◦9; H, 7.52;
N, 0.00. Found: C, 51.22; H, 7.77; N, <0.10. Mp 184 C. FT-IR
(cm-1): 645 w, 718 s, 801 vw, 875 m, 898 w, 921 w, 1012 m, 1126
w, 1155 w, 1184 m, 1211 m, 1235 m, 1256 w, 1278 w, 1504 vw,
1540 w, 1587 m. FT-Raman (cm-1): 140 s, 257 w, 329 vw, 475 vs,
524 m, 567 m, 720 w, 747 vw, 822 m, 927 m, 1013 m, 1129 m,
1157 m, 1181 w, 1201 w, 1236 vw, 1280 w, 1356 vw, 1384 vw, 1446
m, 1588 m, 2702 vw, 2768 vw, 2917 s, 2964 s, 3002 m, 3110 vw,
3179 vw. Solution NMR data (benzene-d6): 1H NMR, d = -0.03
[s, 6H, Me2InSe(2,4,6-tBu3C6H2)], 1.30 [s, 9H, Me2InSe(2,4,6-
tBu3C6H2)], 1.77 [s, 18H, Me2InSe(2,4,6-tBu3C6H2)], 7.48 [s,
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