Aryl-NHC-group 13 trimethyl complexes: structural, stability and bonding insights

Article abstract of DOI:10.1039/c6dt04448d

Treatment of aromatic N-substituted N-heterocyclic carbenes (NHCs) with trimethyl-gallium and -indium yielded the new Lewis acid-base adducts, IMes·GaMe₃ (1), SIMes·GaMe₃ (2), IPr·GaMe₃ (3), SIPr·GaMe₃ (4), IMes·InMe₃ (5), SIMes·InMe₃ (6), IPr·InMe₃ (7), and SIPr·InMe₃ (8), with all complexes being identified by X-ray diffraction, IR, and multinuclear NMR analyses. Complex stability was found to be largely dependent on the nature of the constituent NHC ligands. Percent buried volume (%V_Bur) and topographic steric map analyses were employed to quantify and elucidate the observed trends. Additionally, a detailed bond snapping energy (BSE) decomposition analysis focusing on both steric and orbital interactions of the M-NHC bond (M = Al, Ga and In) has been performed.

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PAPER
Joseph T. Hupp, Omar K. Farha et al.
Efficient extraction of sulfate from water using
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Aryl-NHC-group 13 Trimethyl Complexes: Structural, Stability and
Bonding Insights
Melissa M. Wu,a Arran M. Gill,b Lu Yunpeng,a Li Yongxin,a Rakesh Ganguly,a Laura Falivene*c and
Felipe García*a
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
Treatment of aromatic N-substituted N -heterocyclic carbene (NHC) with trimethyl-gallium and -indium yielded the new
Lewis acid-base adducts, IMes•GaMe3 (1), SIMes•GaMe3 (2), IPr•GaMe3 (3), SIPr•GaMe3 (4), IMes•InMe3 (5), SIMes•InMe3
(6), IPr•InMe3 (7), SIPr•InMe3 (8), with all complexes being identified by X-ray diffraction, IR, and multinuclear NMR
analyses. Complex stability was found to be largely dependent on the nature of the constituent NHC ligands. Percent
Buried Volume (%VBur) and topographic steric map analyses were employed to quantify and elucidate the observed trends.
Additionally, a detailed bond snapping energy (BSE) decomposition analysis focusing on both steric and orbital interactions
of the M-NHC bond (M = Al, Ga and In) has been performed.
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new NHC group 13 complexes remains an exciting area for
main group and organic chemists alike. Our group has
INTRODUCTION
Over the past thirty years, the use of arduengo carbenes to
stabilize transition metal compounds for organic syntheses have
previously reported that minimal adjustment to the steric
properties of the constituent NHC moiety in
trimethylaluminium complexes can have a profound effect on
their stability (Figure 1, ). This prompted us to seek to
been intensively studied.1, Conversely, in the case of Nꢀ
2
heterocyclic carbene group 13 metal complexes,3 only a limited
range of compounds have been applied to organic
transformations,3b,4 despite having shown excellent catalytic
activity in ring opening polymerization reactions (ROPs).4a,4c
Previous studies have shown that slight modifications within
these complexes can result in drastic changes in their reactivity
towards organic transformations – a good example of this being
the greater product yields and selectivity displayed by
IMes•AlH2Cl over IMes•AlHCl2 in hydroalumination reactions
on carbonyl or epoxide containing substrates.3b Cole et al. have
attributed this observation to a stronger AlꢀH bond and
increased steric bulk in IMes•AlHCl2 resulting in poorer
catalytic activity. Further highlighting the importance of steric
and electronic factors on the stability and accessibility of both
normal and abnormal NHC main group complexes are reports
by Hevia et al.5a on the structure, stability and isomerization
AꢀD
quantify and rationalize the structureꢀstabilityꢀreactivity
relationships of heavier group 13 NHC counterparts, using the
commonly employed IMes, SIMes, IPr and SIPr carbenes as
case studies.
Herein, we firstly report the synthesis and characterization of a
series of aromatic Nꢀsubstituted NHC gallium and indium alkyl
complexes. By combining Xꢀray crystallographic and
spectroscopic studies with theoretical calculations, we then
assess the stability and bonding characteristics of these
complexes. An insightful comparison between group 13ꢀNHC
complexes with transition metalꢀNHC and ꢀPHC (using Alꢀ
IMes, PdꢀIMes and Pd(P)IMes as case studies) is also provided.
reactions between normal (n) and abnormal (a) NHCꢀgallium
N
N
R
R
alkyl complexes. Whilst Dagorne et al.5b described the normalꢀ
toꢀabnormal NHC rearrangement and small molecule activation
on the aluminium, gallium and indium triad. With much yet to
be explored, the synthesis, characterization, and reactivity of
M
M = In
(5) R = Mes, Unsat.
M = Ga
M = Al
(A) R = Mes, Unsat.
) R = Mes, Sat.
(C) R = Dipp, Unsat.
(1) R = Mes, Unsat.
(2) R = Mes, Sat.
(3) R = Dipp, Unsat.
(4) R = Dipp, Sat.
6
( ) R = Mes, Sat.
B
(
(7) R = Dipp, Unsat.
(8) R = Dipp, Sat.
(D) R = Dipp, Sat.
Figure 1. New NHC trimethyl-gallium, -indium, and -aluminium complexes.
IMes•GaMe3 ), SIMes•GaMe3 ), IPr•GaMe3 ), SIPr•GaMe3 ), IMes•InMe3
), SIMes•InMe3 ), IPr•InMe3 ), SIPr•InMe3 ), IMes•AlMe3 ),
SIMes•AlMe3 ), IPr•AlMe3 ), SIPr•AlMe3
).6b
(
1
(
2
(
3
(4
(
5
(
6
(
7
(
8
(A
(
B
(
C
(D
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RESULTS AND DISCUSSION
Synthesis of complexes 1-8
The general synthetic route for the synthesis of these complexes
is via the formation of Lewis acidꢀbase adducts (Scheme 1).4ꢀ7
Hence, treatment of 1 equivalent of carbene (IMes, SIMes, IPr
and SIPr) with trimethylgallium8 or indium,9 resulted in the
formation of their respective complexes IMes•GaMe3
SIMes•GaMe3 ), IPr•GaMe3 ), SIPr•GaMe3
IMes•InMe3 ( ), SIMes•InMe3 ( ), IPr•InMe3 (
) as shown in Figure 1. Isolation of compounds was
(
1
),
(
2
(3
(
4
),
5
6
7), SIPr•InMe3
(
8
performed by crystallization in ether or toluene at room
temperature or at 0 oC.9
Figure 2. Previously reported trimethyl and dimethylgallium complexes E 4f
,
F,5b
G- , J- .
I 4a P 4b, 4b
Scheme 1. Synthetic strategy for the NHC adducts. Mes (2,4,6-trimethylphenyl);
Dipp (2,6-diisopropylphenyl).
5b
, R-
Figure 3. Previously reported mono-, di- and trimethylindium complexes
4d
Q
T
.
All compounds are highly airꢀ and moistureꢀsensitive and traces
of decomposition were consistently observed during their
characterization. Hence, all attempts of elemental analyses were
Table 1. Selected M-Ccarbene bond lengths for selected NHC group 13 alkyl complexes.
For depicted structures see Figures 2 and 3
unsuccessful. Moreover, this was also observed for
4 and 8 in
the solidꢀstate, where argonꢀgasꢀstored samples slowly
decomposed at room temperature.
Formulae
IMes•GaMe3
SIMes•GaMe3
IPr•GaMe3
Complex
1
M-Ccarbene[Å]
2.111(2)
2.124(5)
2.105(4)
2.137(2)
2.304(7)
2.316(8)
2.309(2)
2.342(2)
2.098(2)
2.112(6)
2.103(3)
2.127(2)
2.130(2)
2.089(2)
2.132(3)
2.079(1)
2.087(1)
2.080(1)
2.070(2)
2.066(1)
2.056(1)
2.267(2)
2.264(2)
2.183(2)
1
2
2
3
3
Crystallographic studies of complexes 1-8
4
4
SIPr•GaMe3
IMes•InMe3
SIMes•InMe3
IPr•InMe3
Complexes
2
ꢀ
6
recrystallized from solution as two
5
5
crystallographically independent, but chemically equivalent,
molecules and only one molecule will be described herein.
6
6
7
7
Complexes
6 and 8 are the first structurally characterized
8
8
SIPr•InMe3
IMes•AlMe3
SIMes•AlMe3
IPr•AlMe3
trimethylindium complexes containing saturated NHC moieties.
Previously reported gallium and indium NHC species are, for
the most part, heteroleptic complexes (see Figures 2 and 3).
Furthermore, only four trimethylgallium complexes have been
E 4f G 4a I4a and J4c
previously structurally characterized (i.e., , , ,
see Figure 2).3, 4 Generally, heavy group 13 NHC complexes
adopt a four coordinate, distorted tetrahedral geometry at the
A6b
B6b
C6b
D6b
E4f
H4a
I4a
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
SIPr•AlMe3
a
IiPrMe•GaMe3
IMes•GaMe2OMe
SIPr•GaMe3
L4b
M4b
N4b
N’4b
O4b
P4b
R4d
S4d
T4d
SIMes[(CH2)2]L•GaMe2
SIMes[(CH2)3]L•GaMe2.GaMe3
SIMes[Ar’]L•GaMe2
SIMes[Ar’]L•GaMe2.GaMe3
SIPr[Ar’]L•GaMe2
metal centre, with the exception of indium complexes
(IMes•InMe2Cl, IMes•InMe2OTf and IMes•InMe(OTf)2,
respectively).4d Despite being fourꢀcoordinate, the indium
centre of complex does not conform to a distorted tetrahedral
R, S and
T
R
geometry due to the weak carbene chloride interaction that
causes the chloride to lie orthogonal to the carbene plane.4d In
SIPr[Ar”]L•GaMe2
the case of complexes
S and T, the indium centres interact with
IMes•InMe2Cl
an additional neighbouring triflate substituent belonging to an
adjacent molecule, hence directing the complex geometry
towards a pentacoordinate trigonal bipyramidal geometry in the
solidꢀstate.4d
IMes•InMe2OTf
IMes•InMe(OTf)2
a See abbreviations
2 | J. Name., 2012, 00, 1-3
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1
2
3
4
Figure 4. Molecular structures of IMes•GaMe3
(
1), SIMes•GaMe3
(2
), IPr•GaMe3
(
3
) and SIPr•GaMe3
(
4
). Selected bond lengths (Å) and angles (o) for
1
: Ga(1)-C(1)
: Ga(1)-
2.111(2), C(1)-Ga(1)-C(2) 108.8(1), C(1)-Ga(1)-C(3) 105.8(1), C(2)-Ga(1)-C(3) 111.1(1), C(3)-Ga(1)-C(3A) 114.0(2). Selected bond lengths (Å) and angles (o) for
2
C(1) 2.124(5), C(1)-Ga(1)-C(2) 105.0(2), C(1)-Ga(1)-C(3) 110.8(2), C(1)-Ga(1)-C(4) 106.8(2), C(2)-Ga(1)-C(3) 112.5(2), C(2)-Ga(1)-C(4) 113.1(2), C(3)-Ga(1)-C(4) 108.5(3).
Selected bond lengths (Å) and angles (o) for
: Ga(1)-C(1) 2.105(4), C(1)-Ga(1)-C(2) 101.3(1), C(1)-Ga(1)-C(3) 110.7(1), C(1)-Ga(1)-C(4) 108.4(2), C(2)-Ga(1)-C(3)
115.3(2), C(2)-Ga(1)-C(4) 112.4(2), C(3)-Ga(1)-C(4) 108.3(2). Selected bond lengths (Å) and angles (o) for
: Ga(1)-C(1) 2.137(2), C(1)-Ga(1)-C(2) 100.0(1), C(1)-Ga(1)-
C(3) 111.2(1), C(1)-Ga(1)-C(4) 107.5(1), C(2)-Ga(1)-C(3) 110.4(1), C(2)-Ga(1)-C(4) 115.1(1), C(3)-Ga(1)-C(4) 112.1(1). Thermal ellipsoids are drawn at the 50 %
probability level. Hydrogen atoms have been omitted for clarity.
3
4
The molecular structures of compounds 1ꢀ8 revealed the
1ꢀ4
show a relatively strong stretching signal at around 524 cmꢀ
formation of fourꢀcarbonꢀcoordinated gallium and indium 1, consistent with the presence of the methyl groups on the
atoms attached to three alkyl groups, and the presence of a metal centre.14 Unfortunately, in the case of indium analogues,
neutral carbene moiety (see Figures 4 and 5). The distorted no suitable IR stretching signals were clearly observed, since
tetrahedral geometry at the gallium and indium centres is the InꢀMe range falls within a high noise background region
evidenced by the CꢀMꢀC bond angles that range from 100.0 o to
(
i.e., ~400 cmꢀ1).14 An upfield shift of the Ccarbene signals
115.3o and 99.6o to 119.1o for gallium and indium respectively, provides further confirmation of the complexes, as observed
with metal to carbene carbon (MꢀCcarbene) bond lengths ranging with other reported trimethylgallium and indium complexes
from 2.111 Å – 2.137 Å, and 2.301 Å – 2.342 Å for gallium (Table 2).6b, 15 Despite several attempts, no Ccarbene signal was
and indium, respectively. In the case of 1ꢀ4, the GaꢀCcarbene obtained for complex 5, presumably due to the large quadrupole
bond lengths are consistent with the previously reported moment of the indium centre.4, 7
trimethylgallium complexes (cf. 2.130(2) Å, 2.105(2) Å,
2.132(3) Å and 2.121(3) Å and for E, G, I, J, respectively) (see
Lewis acid - Lewis base properties
The majority of previously reported NHCꢀgallium and ꢀindium
complexes comprise halide and hydride derivatives
Table 1).4a, 4e, 4f In agreement with our previous observations for
the lighter trimethylaluminium counterparts in which similar
MꢀCcarbene bond distances between SIPr•AlMe3 and the less
sterically encumbered IiPrMe•AlMe3 (2.127(2) Å and 2.124(6)
Table 2. Selected 1H and 13C NMR chemical shifts for complexes 1-8.
6b
Å, respectively),4f,
were observed. The GaꢀCcarbene bond
1H [InCH3]
(ppm)
-0.56
-0.60
-0.59
-0.58
-0.52
-0.58
-0.60
-0.62
-0.10
0.27
13C [MCcarbene
(ppm)
181.7
206.1
184.5
209.0
–
]
13C [Ccarbene
(ppm)a
219.4
243.8
220.4
244.0
219.4
243.8
220.4
244.0
207.5
212.9
212.9
]
distance in
4 is, also, comparable to that of IiPrMe•GaMe3 (E)
Complexes
(2.137(2) Å and 2.130(2) Å, respectively).4f
1
2
Spectroscopic studies of complexes 1–8
3
4
1
The H and 13C{1H} NMR spectra obtained for complexes
1
ꢀ
8
5
are consistent with the lowꢀtemperature Xꢀray crystallographic
analyses. The 1H NMR spectra for the gallium and indium
complexes display singlets ranging from δH ꢀ0.56 to ꢀ0.60, and
δH ꢀ0.52 to ꢀ0.62 ppm, respectively, which is indicative of the
presence of the methyl substituents on the metal centre. This is
further corroborated by 13C{1H} NMR spectra which display
singlets at δC ꢀ5.2 to ꢀ6.1 and δC ꢀ9.6 to ꢀ11 ppm for gallium and
indium complexes, respectively. Furthermore, the IR spectra of
6
209.3
186.8
211.7
176.8
183.7
183.4
7
8
E4f
F5b
Q5b
0.21
a 13C NMR chemical shifts were obtained from reference 15.
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5
6
7
8
Figure 5. Molecular structure of IMes•InMe3 (5) and SIMes•InMe3 (6) IPr•InMe3 (3) SIPr•InMe3 (8 5: In(1)-C(1) 2.304(8),
). Selected bond lengths (Å) and angles (o) for
C(1)-In(1)-C(2) 105.5(3), C(1)-In(1)-C(3) 105.2(3), C(1)-In(1)-C(4) 104.3(3), C(2)-In(1)-C(3) 114.7(3), C(2)-In(1)-C(4) 111.0(4), C(3)-In(1)-C(4) 114.9(4). Selected bond
lengths (Å) and angles (o)
114.1(3), C(3)-In(1)-C(4) 115.3(3). Selected bond lengths (Å) and angles (o) for
101.3(1), C(2)-In(1)-C(3) 111.4(1), C(2)-In(1)-C(4) 114.5(1), C(3)-In(1)-C(4) 113.3(1). Selected bond lengths (Å) and angles (o) for
99.6(1), C(1)-In(1)-C(3) 104.8(1), C(1)-In(1)-C(4) 108.5(1), C(2)-In(1)-C(3) 119.1(1), C(2)-In(1)-C(4) 109.8(1), C(3)-In(1)-C(4) 113.5(1).Thermal ellipsoids are drawn at the
50 % probability level. Hydrogen atoms have been omitted for clarity.
6
: In(1)-C(1) 2.316(8), , C(1)-In(1)-C(2) 105.9(3), C(1)-In(1)-C(3) 109.2(3), C(1)-In(1)-C(4) 101.8(3), C(2)-In(1)-C(3) 109.7(4), C(2)-In(1)-C(4)
: In(1)-C(1) 2.309(2), C(1)-In(1)-C(2) 106.8(1), C(1)-In(1)-C(3) 108.6(1), C(1)-In(1)-C(4)
: In(1)-C(1) 2.342(2), C(1)-In(1)-C(2)
7
8
(NHC•MH3ꢀnCln; M = Ga and In; n = 1, 2).7 For example, the Ccarbene 13C{1H} NMR signal of the complexes
1ꢀ4 and 6ꢀ8, (see
chlorogallane complexes IMes•GaH2Cl and IMes•GaHCl2 Table 2) are relatively downfield as compared to the gallium
displayed increased Lewis acidity of the metal centre with the and indium complexes IMes•GaClH2 and IMes•InMe2Cl. This
presence of increasing electron withdrawing groups (i.e.
,
is anticipated, given that the presence of the chlorido ligand(s)
chloride atoms), consequently shortening the GaꢀCcarbene bond on the metal centre exerts a strong electronꢀwithdrawing effect
length, and strengthening the gallium hydride bond (Table S3, and further corroborates that MMe3 moiety (M = Ga and In) is a
entries 10 and 11).7i The same effect has also been observed for poorer electron acceptor compared to MH3 and MX3. Jones et
the lighter counterparts IMes•AlH2Cl and IMes•AlHCl2, which al. showed that reactions of potentially chelating bidentate bisꢀ
result in significantly different catalytic activities in NHC or monodentate NHC ligands in 1:1 and 1:2 ratios,
hydroalumination reactions (vide supra).7g With the inclusion respectively, with indium halides produce pentacoordinate
of the herein reported trimethylgallium and indium complexes, trigonal bipyramidal chelate or 2:1 NHC adducts, whereas
a more complete perspective can be obtained regarding hydrides only form monomeric tetracoordinate tetrahedral
7t
substituent effects on the structural properties of group 13 NHC compounds due to the higher Lewis acidity of the former.7o,
complexes by comparison with previously reported halide and Since trimethylindium derivatives are expected to be poorer
hydride counterparts. As expected, in complexes
1 to 4, the Lewis acids than indium halides, only monomeric
trimethylgallium moiety proves a poorer Lewis acid as tetracoordinate tetrahedral species would be anticipated.
compared to their hydrides and halides analogues. This is Therefore, two equivalents of the IMes free carbene were
evident from the GaꢀCcarbene bond distances reported for the reacted with trimethylindium under various experimental
IMes, SIMes and IPr compounds (see SI, entries 1ꢀ3, 9ꢀ14). A conditions; however, despite several attempts pentacoordinate
similar trend can be established in the case of indium trigonal bipyramidal adducts were unable to be isolated
complexes ꢀ Lewis acid strength in increasing order: MMe3 < supporting our initial prediction.
MH3 < MX3. The reported InꢀCcarbene bond distances are shown
in Table S3 (entries 5, 7 and 15ꢀ
19).7
Stability studies
The Ccarbene 13C NMR chemical shift is sensitive to the extent of
the metal centre Lewis acidity, which in turn is directed by the
donor ability of the ligands surrounding the metal centre. The
majority of previously reported NHC gallium and indium
complexes failed to exhibit an MꢀCcarbene signal in their 13C{1H}
NMR spectra, due to the quadrupolar moment of the metal
We have reported that for the lighter trimethylaluminium
compounds
determining the resulting complex stability. Complexes
containing less sterically hindered NHC moieties, i.e and B
AꢀD, the NHC steric bulk plays a significant role in
.
A
(IMes and SIMes, respectively), are relatively stable in their
solidꢀstate and can be stored for prolonged periods under
7
centre.4, Indeed, Ccarbene signal of only one gallium and one
indium NHC complex (IMes•GaClH2 and IMes•InMe2Cl) have
been reported (δC 172.5 and 177.5 ppm, respectively).4d, 7i The
4 | J. Name., 2012, 00, 1-3
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Table 3. M-C(carbene) bond lengths, %VBur (X-ray and DFT) and dissociation energies for selected complexes.
M-Ccarbene [Å]
X-Ray
M-Ccarbene [Å]
DFT
%VBur
%VBur
%VBur
%VBur
Ediss
(kJ·mol–1
)
Entries
Complexes
R = X-ray
R = 2.0 Å(X-ray)
R = DFT
R = 2.0 Å (DFT)
1
2
1
2.111(2)
2.125(5)
2.105(4)
2.137(2)
2.301(8)
2.316(8)
2.309(2)
2.342(2)
2.098(2)
2.112(6)
2.103(3)
2.127(2)
2.130(2)
-
2.201
2.231
2.213
2.233
2.428
2.453
2.446
2.478
2.162
2.188
2.164
2.190
2.165
2.316
2.558
2.301
27.9
31.8
34.0
35.1
28.5
29.2
30.2
31.4
31.7
32.0
33.1
36.1
-
29.6
34.1
36.2
39.3
34.0
34.9
35.7
39.5
33.7
34.1
35.0
38.5
ꢀ
29.5
30.2
30.9
31.9
25.7
26.3
27.1
27.7
28.9
30.4
31.2
32.0
25.5
31.6
28.4
26.2
32.7
33.9
34.3
35.6
33.3
34.4
35.1
36.2
32.8
33.8
34.3
35.5
27.8
36.7
37.5
31.6
76.7
69.0
65.2
52.8
73.9
66.8
61.5
51.3
105.2
95.6
93.5
77.8
90.3
34.2
20.5
23.3
2
3
3
4
4
5
5
6
6
7
7
8
8
9
A6b
10
11
12
13
14b
19b
20
B6b
C6b
D6b
E4f
F5b
Q5b
-
ꢀ
-
-
ꢀ
5a
IPr•Ga(CH2SiMe3)3
2.196(2)
31.9
36.1
%VBur Me groups on IPr-GaR3 = 48.7
%VBur CH2SiMe3 groups on IPr-GaR3 = 64.5
nitrogen without any signs of decomposition, whereas case of compounds
4
and
8. However, signals indicative of the
complexes containing bulkier NHC ligands, i.e. and
C
D (IPr formation of abnormal species for the reported metals
and SIPr, respectively), slowly decompose to their respective complexes were not observed throughout our 1H NMR studies.
imidazolylidene and imidazolinylidene over time.6b These
stability differences were attributed to the larger Percent Buried In order to elucidate stability trends within the triad, %VBur
Volume (%VBur) occupied by the NHC ligands of
and SIPr), as compared to those of and
SIMes),6b,16 indicating that subtle variations in the steric bulk of bond length set at 2.0 Å ꢀ to enable a comparison between the
the NHC substituent ( %VBur ca. 2–4%) profoundly impact the various NHC ligands unbiased by variable MꢀNHC bond
overall complex stability. Additional insights gleaned by Hevia distances (see Table 3).16 In agreement with the calculated
C
and
D (IPr calculations were undertaken with the MꢀCcarbene bond distance
A
B (IMes and fixed as the value obtained from our Xꢀray studies, and the
ꢀ
et. al.5a and Dagorne et. al.5b showed that bulky
13 complexes, such as IPrGa•(CH2SiMe3)3, ItBu•GaMe3 (
ItBu•InMe3 ) all isomerize to their respective
n
NHC group dissociation energies, the %VBur increases gradually from
) and and to
NHC Consequently, the relatively low stability observed for 4 and
1
to
4
F
a
5
8
for the gallium and indium complexes, respectively.
(
Q
8
counterparts, with the latter two isomerizing too rapidly to may be qualitatively rationalized by the larger volume occupied
allow characterization in their normal form. Theoretical DFT by isopropylphenyl groups as compared to the mesityl groups
calculations performed for normal and abnormal model present in the NHC moieties.6b In a quantitative comparison
complexes of
with Gibbs free energy of ꢀ24.6 kJ·mol–1 and ꢀ5.8 kJ·mol–1 for
vs and vs , respectively.
F
and
Q
revealed that the latter are more stable between stable and unstable complexes – i.e., IPr vs. SIPr,
3 vs.
4
and vs. ca. 8.5% and 10.6% %VBur variances are
7
8
–
ꢀ
nF
.
aF
nQ
.
a
Q
observed for Ga and In, respectively – slightly greater than
those found for their lighter Al counterparts (ca. 4 %).6b
The mechanism proposed for the model complex
IPrGa•(CH2SiMe3)3 involves an initial dissociation to generate To gain a more thorough appreciation of NHC structureꢀ
the free carbene and subsequent formation of the abnormal stability relationships, we calculated the DFT optimized
carbene species. In the case of our complexes
C and D, solid structures for complexes 1ꢀ8 and our previously reported
crystalline samples stored under nitrogen showed complexes AꢀD. For completeness, we extended this study to
decomposition into the free carbene alongside other include IPr•Ga(CH2SiMe3)3 and the hypothetical ItBu
unidentifiable species in their NMR spectra.6b In the case of the trimethylgallium and indium
nNHC complexes (F and Q,
heavier Ga and In counterparts, compounds 1ꢀ8 showed respectively)5b (see Table 3). Theoretical parameters were
relatively greater stability as compared to their lighter consistent with the observed experimental trends, however,
analogues, with signs of decomposition observed only in the
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8
, localization of steric hindrance around the bulkier ortho
calculated
ꢀ%VBur reduced to only ca. 3.7% and 3.1%, for
isopropyl group was clearly observed on the steric contour map
(see Figure 6 and SI). This asymmetric spatial distribution of
gallium and indium, respectively.
the NHC ligand around the metal centres in
4
and
8
correlates
Inclusion of the hypothetical complex nF produced a ꢀ%VBur
to their reduced stability as compared to
(see ESI).
2
and
6 respectively
of ca. 7% in a comparison with the stable complex 3. This
relatively minor discrepancy in %VBur has a pronounced effect
in terms of dissociation energy, which is less than half for
than cf. 65.2 kJ respectively).
molꢀ1 and 34.2 kJ molꢀ1
Furthermore, the unstable complex , similar in steric bulk to
(%VBur of 35.6% and 36.7%, respectively) has a significantly
lower dissociation energy as compared to complex cf. 34.2
kJ and , respectively). These
molꢀ1 and 52.8 kJ molꢀ1 for
observations are in line with those we reported for Al
complexes SIPr•AlMe3 ( ) and ItBu•AlMe3 (cf. %VBur and Ediss
for complexes and ItBu•AlMe3 are 35.5%, 77.8 kJ
molꢀ1 and
36.9%, 46.2 kJ
molꢀ1, respectively) attributed to the varying
F
3
(
·
·
,
Bonding studies
4
F
To gain a better understanding of the nature of MꢀNHC bonds
with M= Al, Ga and In, a bond snapping energy BSE) analysis
4
(
(
·
·
F
4
was performed.16 The BSE is the energy required for the
dissociation of the MꢀL bond, analysed based on the interaction
between fragments possessing both the local equilibrium
geometry of the final molecule and an electronic structure
suitable for bond formation. To calculate the heterolytic BSE
for 1ꢀ8, the geometry of the metal fragment [M] – in this case
MMe3 – was fixed, and the complex fragmented into its
corresponding neutral [M] and NHC components.
D
D
·
·
electron donating properties of the SIPr and ItBu NHCs
moieties to the metal centre.6b
The DFT calculated %VBur between complexes
their ItBu analogues and , showed comparable values (cf.
35.6%, 36.2%, 36.7% and 37.5% and respectively).
The slightly lower values observed for and are in
accordance with their greater stability in normal NHC form as
4 and 8, and
n
F
nQ
Although BSE does not correlate in all instances with bond
dissociation enthalpies (since reorganization and relaxation of
the fragments are not considered), it closely relates to bond
enthalpy terms, providing a good approximation to bond
strength values.
4
,
8
,
F
Q
4
8
compared to
nF and nQ, which readily isomerize their
abnormal form.5b Unfortunately, all attempts to isolate metalꢀ
containing species resulting from the structural decay of
The BSE can be decomposed into two main terms, namely
steric interaction (ꢁE0) and orbital interaction (ꢁEint) (Eqn
1):17
complexes
4 and 8 were unsuccessful.
Our calculations indicate that the facile isomerization of the
5a
previously reported IPr•Ga(CH2SiMe3)3 to its abnormal
ꢀꢁꢂ ꢃ ꢄꢅ∆ꢂꢆ ꢇ ∆ꢂꢈꢉꢊ
ꢋ
(Equation 1)
isomeric form can be attributed to the higher steric congestion
imposed by the CH2SiMe3 when compared to Me groups
(%VBur 64.5% and 48.7% for CH2SiMe3 and Me groups). This
is further illustrated by the longer GaꢀCcarbene bond distance and
lower dissociation energies calculated for IPr•Ga(CH2SiMe3)3
The steric interaction term ꢁE0 can be further split into an
electrostatic interaction term ꢁEelstat and a Pauli repulsion term
ꢁEPauli. (Eqn 2):17
and IPr•GaMe3 (3) (cf., 2.196(2) Å vs. 2.105(4) Å and 65.2
kJ·mol–1 vs. 23.3 kJ·mol–1, respectively).
∆ꢂꢆ ꢃ ∆ꢌꢍꢎꢊꢏꢊ ꢇ ∆ꢂꢐꢏꢑꢍꢈ
(Equation 2)
The ꢁEPauli repulsion term describes the twoꢀorbital electron
interactions between the occupied orbitals of both fragments.
The ꢁEelstat and ꢁEPauli terms constitute stabilizing and
destabilizing contributions to BSE, respectively, with their
relative contributions determining the overall character of ꢁE0.
Comparative analysis of a stable vs. an unstable system using
topographic steric maps of saturated complexes
2
vs. 4 and 6 vs.
8
showed that the distribution of steric bulk of the SIMes ligand
in
2
and
6
is symmetrical around the metal, whereas for
4
and
The ꢁEint term may also be further broken down into
contributions from respective orbital interactions within the
various irreducible representations
group of the system (Eqn 3):17
ꢒ of the overall symmetry
ꢓ ∆ꢂꢓ
(Equation 3)
∑
∆ꢂꢈꢉꢊ
ꢃ
ꢈꢉꢊ
Each complex studied in the present work, 1ꢀ8, has been
optimized with a Cs imposed symmetry, where the NHC
ligands are positioned in the σxy mirror plane of the molecule.
Therefore, the A′ contributions to the orbital interaction energy
are associated with σꢀbonding, wheras the A” contributions
Figure 6. Topographic steric maps of the SIMes and SIPr ligands in
6
and
8
. The
iso-contour curves of the steric maps are in Å. The maps have been obtained
starting from the crystallographic data of the Al-NHC complexes (CIF), with the
Al-Ccarbene distance fixed at 2.0 Å. The xz plane is the mean plane of the NHC ring,
whereas the yz plane is the plane orthogonal to the mean plane of the NHC ring,
and passing through the Ccarbene atom of the NHC ring.
6 | J. Name., 2012, 00, 1-3
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represent πꢀinteractions. The A” contribution of the orbital greatest contribution, with ꢁ(ꢁEPauli(Ga)
interaction energy may be further divided into NHC→M π– times greater with respect to the electrostatic ꢁ(ꢁEelstat(Ga)
donation, ∆Eꢈꢔꢉꢊ
and M→NHC π–backdonation, ꢁEelstat(In)). The orbital interaction is much greater for the Gaꢀ
– ꢁEPauli(In)) being 1.5
–
,
C→M
∆Eꢈꢔꢉꢊ M→C. To estimate these two interactions, additional IMes bond, both at σ and π levels, compensating the unfavored
constrained space orbital variation (CSOV) calculations were steric term. Similarly, this was reported for the computed
performed.17 In particular, to assess the contribution of πꢀ IMe•GaH3 complex and it’s In analogue.18 For completeness, it
donation, bond decomposition analysis was performed by is worth noting that the greater BSE observed for the AlꢀNHC
considering the interaction of a [M] fragment and an NHC bond, with respect to that of GaꢀNHC, reflects the larger Ediss
ligand, excluding the set of virtual A” orbitals of the NHC associated with Al compounds compared to Ga (see last column
fragment from the variational space. In this way, the A” in Table 3). With regard to the Ga/In trend, the dissociation
contribution of the orbital interaction energy is associated only energies are almost identical (varying less than 4.0 kJ·mol–1), in
with the NHC→[M] A” donation, or πꢀdonation. Similarly, the agreement with the smaller discrepancy between the BSE for
level of
π
backꢀdonation was determined by explicitly the Ga/InꢀNHC bonds respect to the Al/GaꢀNHC bonds (i.e. 20
kJ molꢀ1 and 30 kJ molꢀ1 for Al and Ga, respectively).
excluding all virtual A” orbitals on the [TM] fragment.
1
The energy decomposition analysis (EDA) is performed in the Further group 13 bonding insights can be obtained from the H
gasꢀphase since it refers to the intrinsic strength of the MꢀNHC and 13C NMR spectra. Hence, DFTꢀNMR analyses were
bond, which is independent on the environment that may performed for the Ccarbene and Me group hydrogen atoms in the
stabilize the two fragments. We selected one NHC ligand, complexes IMes•AlMe3 (
namely IMes, as a case study for comparison between the three their 13C and 1H NMR spectra. The calculated chemical
metals (see Table 4). The data reported in Table 4 suggests that shielding ( C) is ꢀ3.9 and ꢀ24.3 ppm for the Ccarbene atom of
the greater strength of the Al–IMes bond with respect to that of IMes and SIMes system, respectively. Decomposition of the
the GaꢀIMes is mainly attributable to the steric term (ꢁE0). In isotropic σC into diaꢀ and paramagnetic terms, σC σd σp
fact, the Pauli contribution of the steric term, ꢁEPauli indicates that the change in σC is mainly due to the
destabilizes the Ga system more than the electrostatic term is paramagnetic term σp, that varies by almost 21 ppm downfield
able to stabilize it, with the ꢁ(ꢁEPauli(Ga)
ꢁEPauli(Al)) being from IMes to SIMes. Previous literature19 has indicated that the
almost 3.5 times larger with respect to the ꢁ(ꢁEelstat(Ga) carbene chemical shift in NHC ligands is related to transitions
ꢁEelstat(Al)). As a result, the steric term disfavours the GaꢀIMes between the filled orbitals of the MꢀNHC bond (HOMO) and
A) and SIMes•AlMe3 (B) to predict
σ
=
+
,
,
–
–
σ
bond by 45.7 kJ·mol–1. This is in agreement with theoretical the empty π orbital of the carbene (LUMO). Hence, we
studies by Frenking et. al. on a series of IMe NHC group 13 undertook analyses on the HOMOꢀLUMO energies of the NHC
metal hydride complexes.18 Our detailed orbital analysis shows ligand showing that the energy gap decreases by almost 0.2 eV
that the greater ꢁEPauli term for GaꢀIMes system is related to from IMes to SIMes. This can be attributed to a decreased
interactions between occupied orbitals on the NHC and stability of the SIMes NHC molecule HOMO, which results in
occupied 3d orbitals on the Ga atom whereby the smaller a stronger magnetic coupling, and additionally accounts for the
ꢁEPauli for Al is due to the lack of available dꢀelectrons. higher paramagnetic shielding (corresponding downfield shift)
Intuitively, the orbital interaction is primarily constituted by the in AlꢀSIMes with respect to AlꢀIMes. The DFT 1H NMR
σ term, which is larger in magnitude for the GaꢀIMes system, as analysis revealed that the upfield shift of the SIMes•AlMe3
18
also seen for the IMe•GaH3 compared to its Al counterpart methyl hydrogens corresponds to a reduced π backꢀdonation
(see Table 4). For the π term, the main difference is in the [Al]→NHC (π*) that results from a smaller π orbital overlap,
M→C interaction, i.e. almost 4 kJ·mol–1 stronger for Al.
probably as a consequence of the slightly elongated AlꢀSIMes
bond distance. As a result of this decreased [Al]→NHC backꢀ
In a comparison of Ga vs. In, the steric term (ꢁE0) once again donation, electron density is pushed towards neighbouring
disfavors the Ga system. In this case, the ꢁEPauli term has the ligands on the Al centre, i.e. the methyl groups, thus leading to
an upfield shift of the H atoms.
Table 4. EDA results (in kJ·mol–1
) of MꢀIMes bond (M= Al, Ga and In)
Our EDA results highlight that the interactions between
occupied orbitals on the NHC and occupied Ga 3d orbitals
destabilize this system with respect to Al and In counterparts.
However, a stronger orbital interaction for Ga compared to In
sets the trend of the total MꢀNHC bond strength as Al > Ga >
In. Overall orbital interaction is primarily constituted by the σ
term, with a relatively small π term that consists mostly of a
backꢀdonation from the metal fragment to the NHC. To further
extend our comparison and quantify existing bonding
discrepancies between our main group NHC complexes and
wellꢀestablished transition metal (TM)ꢀNHC and ꢀPHC
systems, BSE decomposition analyses were performed,
complexes
A(Al)
1(Ga)
45.7
5(In)
20.3
ꢁE0
10.0
ꢀ321.4
ꢁEelstat
ꢁEPauli
ꢁEint
ꢀ334.7
ꢀ287.6
331.4
380.4
308.0
ꢀ175.4
ꢀ180.8
ꢀ135.5
σ−ꢁEint
π−ꢁEint
ꢀ151.3 (86.3 %)
ꢀ24.1 (13.7 %)
ꢀ8.5
ꢀ161.4 (89.3 %)
ꢀ19.4 (10.7 %)
ꢀ7.3
ꢀ119.8 (88.5 %)
ꢀ15.6 (11.5 %)
ꢀ5.5
ꢕꢖꢗꢚꢘꢙ
C→M
∆ꢖꢗꢚꢘꢙ
ꢀ18.1
ꢀ14.3
ꢀ11.4
M→C
BSE
165.3
135.1
115.2
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implementing IMesꢀPdꢀIMes and IMes(P)ꢀPdꢀ(P)IMes as case
studies (see Table 5).
EXPERIMENTAL SECTION
Table 5. BSE-decomposition (in kJ·mol-1) of Al-IMes, Pd-IMes and Pd-(P)IMes
General Procedures
bond
All manipulations were carried out using standard Schlenk and
gloveꢀbox techniques under driedꢀargon atmosphere and using
ovenꢀdried glassware. Ether and toluene were distilled over
Na/benzophenone, degassed and purged with dry argon prior to
use, and stored under 4 Å molecular sieves. Deuterated
benzene, C6D6, was distilled over Na and stored under
potassium mirror. Acetonitrile, for highꢀresolution mass
Al-IMes
-321.4
Pd-IMes
-589.4
Pd-(P)IMes
-537.3
ΔEelstat
ΔEPauli
331.4
578.3
550.6
ΔE0
10.0
-11.1
13.3
ΔEint
-175.4
-182.7
-196.7
σ−ΔEint
π−ΔEint
ꢕꢖꢗꢚꢘꢙ C→M
∆ꢖꢗꢚꢘꢙ M→C
BSE
-151.3 (86.3 %)
-24.1 (13.7 %)
-8.5
-129.0 (70.6 %)
-53.8 (29.4 %)
-5.8
-143.2 (72.8 %)
-53.5 (27.2 %)
-5.6
spectrometry, was stirred over
4 Å molecular sieves,
subsequent distilled over CaH2 prior to use, and stored under 4
Å molecular sieves. Starting materials, IMes, SIMes, IPr, SIPr
-18.1
-50.6
-49.6
22
were prepared as previously described.13, Trimethylgallium
165.3
193.8
183.4
was synthesized by first dissolving gallium trichloride (5.00 g,
28.40 mmol) in 5 mL of degassed toluene followed by
dropwise addition of the mixture degassed triethylamine (4.44 g
43.89 mmol) and trimethylaluminium (3.16 g, 43.89 mmol).
Following the addition, the reaction was stirred overnight and
distilled at atmospheric pressure to obtain the neat
trimethylgallium.7 Solution of trimethylgallium (0.702 M) in
toluene was then prepared from the distilled trimethylgallium.
Trimethylindium was generated in situ by reacting MeLi (3 M
in DME) with InCl3 (0.221 g, 1 mmol) dissolved in ether at ꢀ78
oC and filtered through Celite before addition to the carbene.8
The increased strength of the PdꢀNHC bond (almost 30.0
kJ·molꢀ1) with respect to that of AlꢀNHC is largely attributed to
the steric term (20.0 kJ·molꢀ1) rather than to the orbital
interaction (10 kJ·molꢀ1). For the latter contribution, despite a
smaller σ term in the PdꢀNHC bond, a twoꢀfold greater π term
is found due to π backꢀdonation. In the case of the PdꢀPHC
system, the considered bond bears a greater resemblance to that
of AlꢀNHC for the steric and σ terms, and as expected, a
significant π backꢀdonation term, similar to the case of PdꢀNHC
is found. Substitution of N with P atoms results in both a
strengthening of orbital contribution (σ term) and disfavouring
of the steric term (mainly Pauli term) to the MꢀNHC bond.
Instrumentation
1H (400 MHz), 13C NMR (100/125 MHz) spectra were
CONCLUSIONS
The presented work describes the synthesis and characterization
collected using
a
Bruker Avance DPX400 and 500
spectrometers with the H, 13C NMR chemical shifts internally
referenced to the residual solvent used. All NMR spectroscopic
analyses were performed at room temperature (300K). Highꢀ
resolution mass spectra were obtained by using a Water QꢀTof
Premier, with ESI mode. Melting points were determined on a
SRSꢀOptimelt MPAꢀ100 apparatus using sealed glass
capillaries under argon and were uncorrected. Infrared
spectrums were recorded as Nujol mulls by using NaCl plates
on Shimadzu IR Prestigeꢀ21 FTIR Spectrometer.
1
of
a
series of new aromatic
Nꢀsubstituted NHC
trimethylgallium and indium species. Similarly, to their
aluminium counterparts, these complexes exhibit varying
stabilities, which are attributed to small differences in the steric
bulk of the chosen NHC. Our computational study has allowed
quantification and rationalisation of discrepancies between Mꢀ
NHC bond strengths for the Al, Ga, In triad. Moreover, a
quantiative comparison with wellꢀestablished transition metal
systems (PdꢀNHC and ꢀPHC) determine that an increase in both
the electrostatic interaction and [M]→NHC π backꢀbonding are
largely responsible for existing differences between group 13
and transition metals NHC complexes.
Procedure for the synthesis of complexes 1-8
IMes•GaMe3 (1): IMes (0.304g, 1 mmol) was dissolved in
toluene followed by the addition of trimethylgallium (GaMe3),
(1.45 mL, 1 mmol, 0.702 M in toluene) at room temperature.
The resulting solution was stirred overnight at room
temperature and later filtered through Celite to give a clear
solution. The solvent was then evaporated to dryness, followed
by the addition of ether to yield a saturated solution. Colourless
crystals were grown at room temperature. Yield: 37%. Mp: 196
– 199 oC. 1H NMR (400 MHz, C6D6): δ = ꢀ0.56 (s, 9H, GaMe3),
Abbreviations
IiPrMe (IiPrMe = 1,3ꢀisopropylꢀ4,5ꢀdimethylimidazolꢀ2ꢀylideꢀ
ne); ItBu (1,3ꢀdiꢀtertꢀbutylimidazolꢀ2ꢀylidene); IMes (1,3ꢀbisꢀ
(2,4,6ꢀtrimethylphenyl)imidazolꢀ2ꢀylidene); SIMes (1,3ꢀbisꢀ
(2,4,6ꢀtrimethylphenyl)imidazolinꢀ2ꢀylidene); IPr (1,3ꢀbisꢀ(2,6ꢀ
diisopropylphenyl)imidazolꢀ2ꢀylidene) and SIPr (1,3ꢀbisꢀ(2,6ꢀ
diisopropylphenyl)imidazolinꢀ2ꢀylidene); PHC (PꢀHeterocyclic
carbene).
2.01 (s, 12H,
NC ), 6.76 (s, 4H, C6
= ꢀ6.1 (GaMe3), 17.6 (ArMe), 21.0 (ArMe), 122.5 (N
Ar), 135.4 (Ar), 135.6 (Ar), 139.3 (Ar), 181.7 (Ccarbene, weak).
o
ꢀPh(C
H
3)), 2.09 (s, 6H,
2). 13C{1H} NMR (100 MHz, C6D6): δ
H), 129.3
pꢀPh(CH3)), 6.02 (s, 2H,
H
H
C
Acknowledgements
The F. G. would like to thank NTU startꢀup grant (M4080552)
and MOE Tier 1 grant (M4011441) for financial support. L. F
would like to thank KAUST for financial support.
(
IR (Nujol, cmꢀ1):
C24H33GaN2 [
ṽ = 525 (ꢛ GaꢀC stretch; m). HRMS: calcd for
M
+H]+: 419.1978; found 419.1992.
8 | J. Name., 2012, 00, 1-3
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SIMes•GaMe3 (2). The same procedure was adopted as that InMe3), 2.09 (s, 6H,
for except that colourless crystals were obtained in saturated (s, 4H, NC 2), 6.78 (s, 4H, C6
toluene solution. Yield: 53%. Mp: 201 – 205 oC. 1H NMR (400 C6D6): δ = ꢀ10.7 (InMe3, broad), 17.9 (ArMe), 21.0 (ArMe),
MHz, C6D6): δ = ꢀ0.60 (s, 9H, GaMe3), 2.08 (s, 6H, 50.9 (N H), 129.9 (Ar), 135.5 (Ar), 136.1 (Ar), 138.5 (Ar),
Ph(C 3)), 2.21 (s, 12H, ꢀPh(C 3)), 3.02 (s, 4H, NC 2), 6.77 209.3 (Ccarbene, weak). HRMS: calcd for C24H35InN2 [
+H]+:
(s, 4H, C6
2). 13C{1H} NMR (100 MHz, C6D6): δ = ꢀ5.9 467.1917; found 467.1923.
(GaMe3), 17.9 (ArMe), 21.0 (ArMe), 50.9 (N H), 129.7 (Ar),
135.6 (Ar), 136.1 (Ar), 138.4 (Ar), 206.1 (Ccarbene, weak). IR IPr•InMe3 (7). The same procedure was adopted as that for
p
ꢀPh(C
H
3)), 2.19 (s, 12H,
H
oꢀPh(CH3)), 3.01
1
H
2). 13C{1H} NMR (100 MHz,
p
ꢀ
C
H
o
H
H
M
H
C
5
(Nujol, cmꢀ1):
C24H35GaN2 [
ṽ
M
= 525 (
ꢛ GaꢀC stretch; s). HRMS: calcd for but reaction was conducted at room temperature. Colourless
+H]+: 421.2134; found 421.2140.
crystals were grown at 0 oC. Yield: 63%. Mp: 148 – 153 oC. 1H
NMR (400 MHz, C6D6): δ = ꢀ0.60 (s, 9H, InMe3), 0.99ꢀ1.01 (d,
IPr•GaMe3 (3). The same procedure was adopted as that for
1
12H, JHꢀH = 6.8 Hz, CH(C
3)2), 2.72ꢀ2.79 (p, 4H, JHꢀH = 6.9 Hz, C
toluene solution. Yield: 35%. Mp: 167 – 172 C.1H NMR (400 6.48 (s, 2H, NC
2), 7.11ꢀ7.13 (m, 4H, ꢀC6 3), 7.23ꢀ7.26 (m,
MHz, C6D6): δ = ꢀ0.59 (s, 9H, GaMe3), 0.99ꢀ1.00 (d, 12H, JHꢀH 2H, ꢀC6
3). 13C{1H} NMR (100 MHz, C6D6): δ = ꢀ10.3
= 6.8 Hz, CH(C 3)2), 1.38ꢀ1.40 (d, 12H, JHꢀH = 6.8 Hz, (InMe3, broad), 23.1 (CH( H3)2), 25.6 (CH( H3)2), 28.8
CH(C 3)2), 2.75ꢀ2.82 (p, 4H, JHꢀH = 6.8 Hz, C (CH3)2), 6.46 H(CH3)2), 124.2 (Ar), 130.6 (N H), 135.6 (Ar), 145.8 (Ar),
(s, 2H, NC 2), 7.11ꢀ7.13 (m, 4H, ꢀC6 3), 7.22ꢀ7.26 (m, 2H, 186.8 (Ccarbene, weak). HRMS: calcd for C30H45InN2 [
+H]+:
ꢀC6
3). 13C{1H} NMR (100 MHz, C6D6): δ = ꢀ5.6 (GaMe3), 549.2700; found 549.2704.
22.8 (CH( H3)2), 25.8 (CH( H3)2), 28.8 ( H(CH3)2), 124.1
Ar), 124.2 (Ar), 130.6 (N H), 135.6 (Ar), 145.8 (Ar), 184.3 SIPr•InMe3 (8). The compound SIPr (0.390 g, 1 mmol) were
H
3)2), 1.36ꢀ1.38 (d, 12H, JHꢀH = 6.8
except that colourless crystals were obtained in saturated Hz, CH(C
H
H(CH3)2),
o
H
m
H
p
H
H
C
C
H
H
(
C
C
H
m
H
M
p
H
C
C
C
(
C
(Ccarbene, weak). IR (Nujol, cmꢀ1):
HRMS: calcd for C30H45GaN2
503.2930.
ṽ = 525 (ꢛ GaꢀC stretch; m). dissolved in ether followed by the addition of inꢀsitu generated
[
M
+H]+: 503.2917; found trimethylindium (InMe3, 1 mmol) to the reaction mixture at 0
oC. The resulting solution was stirred for 30 mins at 0 oC,
subsequently colourless crystals were formed. The solution was
SIPr•GaMe3 (4). The same procedure was adopted as that for
1
removed to isolate the crystals and later concentrated to yield
except that colourless crystals were obtained in saturated more compound. Colourless crystals were grown at 0 oC. Yield:
toluene solution. Yield: 39%. Mp: 207 – 210 oC. 1H NMR (400 36%. Mp: 194 – 200 C. H NMR (400 MHz, C6D6): δ = ꢀ0.62
MHz, C6D6): δ = ꢀ0.58 (s, 9H, GaMe3), 1.15ꢀ1.17 (d, 12H, JHꢀH (s, 9H, InMe3), 1.10ꢀ1.11 (d, 12H, JHꢀH = 6.8 Hz, CH(C 3)2),
= 6.8 Hz, CH(C 3)2), 1.50ꢀ1.51 (d, 12H, JHꢀH = 6.8 Hz, 1.43ꢀ1.45 (d, 12H, HꢀH = 6.8 Hz, CH(C 3)2), 3.19ꢀ3.26 (p, 4H,
CH(C 3)2), 3.28ꢀ3.35 (p, 4H, JHꢀH = 6.7 Hz, C (CH3)2), 3.50 JHꢀH = 6.8 Hz, C (CH3)2), 3.42 (s, 4H, NC 2), 7.10ꢀ7.12 (m,
(s, 4H, NC 2), 7.14ꢀ7.16 (m, 2H, ꢀC6 3), 7.21ꢀ7.27 (m, 4H, 4H, ꢀC6 3), 7.19ꢀ7.23 (m, 2H, ꢀC6
3). 13C{1H} NMR (125
ꢀC6 MHz, C6D6): δ = ꢀ9.6 (InMe3, broad), 23.9 (CH( H3)2), 25.9
3). 13C{1H} NMR (100 MHz, C6D6): δ = ꢀ5.2 (GaMe3
broad), 23.7 (CH( H3)2), 26.1 (CH( H3)2), 28.8 ( H(CH3)2), (CH( H3)2), 28.8 ( H(CH3)2), 54.1 (N H), 124.7 (Ar), 129.9
54.0 (N H), 124.6 (Ar), 129.8 (Ar), 135.8 (Ar), 146.8 (Ar), Ar), 135.7 (Ar), 146.8 (Ar), 211.7 (Ccarbene, weak). HRMS:
209.0 (Ccarbene, weak). IR (Nujol, cmꢀ1): +H]+: 551.2856; found 551.2878.
= 521 ( GaꢀC calcd for C30H47InN2 [
+H]+: 505.3073;
o
1
H
H
J
H
H
H
H
H
H
p
H
m
H
p
H
m
H
,
C
C
C
C
C
C
C
C
(
ṽ
ꢛ
M
stretch; m). HRMS: calcd for C30H47GaN2 [
found 505.3090.
M
X-ray crystallographic studies.
Di
ffractionꢀquality crystals 1ꢀ8 were obtained in toluene or
IMes•InMe3 (5): The compound IMes (0.304g, 1 mmol) was
dissolved in ether followed by the addition of in situ generated
trimethylindium (InMe3, 1 mmol) to the reaction mixture at 0
oC. The resulting solution was stirred overnight at 0 oC and later
filtered through Celite to give a clear solution. Solution was
concentrated and colourless crystals were grown at 0 oC. Yield:
o
ether solvent at room temperature or 0 C. The crystals were
mounted onto quartz fibres, and the Xꢀray di
data were measured at 103 with
di
ff
raction intensity
K
a Bruker Kappa
ff
ractometer equipped with a CCD detector, employing Mo K
α radiation (λ = 0.71073 Å), with the SMART suite of
programs.20 All data were processed and corrected for Lorentz
o
34%. Mp: 172 – 179 C. 1H NMR (400 MHz, C6D6): δ = ꢀ0.52
and polarization effects with SAINT and for absorption effects
(s, 9H, InMe3), 1.99 (s, 12H,
Ph(C 3)), 6.03 (s, 2H, NC ), 6.77 (s, 4H, C6
NMR (100 MHz, C6D6): δ = ꢀ11.0 (InMe3), 17.6 (ArMe), 21.0
(ArMe), 122.5 (N H), 129.4 (Ar), 135.3 (Ar), 135.6 (Ar), 139.4
Ar). HRMS: calcd for C24H33InN2 [
+H]+: 465.1761; found
465.1757.
o
ꢀPh(C
H
3)), 2.09 (s, 6H,
pꢀ
with SADABS.21 Structural solution and refinement were
carried out with the SHELXTL suite of programs.22 The
structures were solved by direct methods or Patterson maps to
H
H
H
2). 13C{1H}
C
locate the heavy atoms, followed by di
light, nonꢀhydrogen atoms. All nonꢀhydrogen atoms were
refined with anisotropic thermal parameters. The crystals of
fference maps for the
(
M
7
had one disordered isoꢀpropyl group and is modelled in two
alternative sites (with ~0.5 occupancy) and refined with
appropriate restraints.
SIMes•InMe3 (6). The same procedure was adopted as that for
but reaction was conducted at room temperature. Colourless
crystals were grown at room temperature (25 C). Yield: 60%.
Mp: 213 – 216 oC. 1H NMR (400 MHz, C6D6): δ = ꢀ0.58 (s, 9H,
5
o
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ARTICLE
Journal Name
Angew. Chem. Int. Ed., 2010, 49, 10158ꢀ10162; (
R. E. Mulvey, S. D. Robertson, Dalton Trans., 2010, 39
) A.ꢀ L. Schmitt, G. Schnee, R. Welter, S. Dagorne, Chem.
Commun., 2010, 46, 2480ꢀ2482; ( ) W.ꢀC. Shih, C.ꢀH. Wang, Y.ꢀT.
Chang, G. P. A. Yap, T.ꢀG. Ong, Organometallics, 2009, 28, 1060ꢀ
1067; ( ) Y. Lee, B. Li, A. H. Hoveyda, J. Am. Chem. Soc., 2009,
131, 11625ꢀ11633; ( ) M. Schiefer, N. D. Reddy, H.ꢀJ. Ahn, A.
Stasch, H. W. Roesky, A. C. Schlicker, H.ꢀG. Schmidt, M.
Noltemeyer, D. Vidovic, Inorg. Chem., 2003, 42, 4970ꢀ4976; ( ) H.
Zhou, E. J. Campbell, S. T. Nguyen, Org. Lett., 2001, 14, 2229ꢀ2231.
) C. Bour, J. Monot, S. Tang, R. Guillot, J. Farjon, V. Gandon,
Organometallics, 2014, 33, 594ꢀ599; ( ) A. ElꢀHellani, J. Monot, S.
Tang, R. Guillot, C. Bour, V. Gandon, Inorg. Chem., 2013, 52
11493ꢀ11502; ( ) A. Higelin, S. Keller, C. Göhringer, C. Jones, I.
Krossing, Angew. Chem. Int. Ed., 2013, 52, 4941ꢀ4944; ( ) A. Elꢀ
Hellani, J. Monot, R. Guillot, C. Bour, V. Gandon, Inorg. Chem.
2013, 52, 506ꢀ514; ( ) S. Tang, J. Monot, A. ElꢀHellani, B. Michelet,
R. Guillot, C. Bour, V. Gandon, Chem. Eur. J., 2012, 18, 10239ꢀ
10243; ( ) G. E. Ball, M. L. Cole, A. I. McKay, Dalton Trans., 2012,
41, 946ꢀ952; ( ) S. G. Alexander, M. L. Cole, C. M. Forsyth, Chem.
Eur. J., 2009, 15 9201ꢀ9214; (h) S. G. Alexander, M. L. Cole, S. K.
Furfari, M. Kloth, Dalton Trans., 2009, 16 2909ꢀ2911; ( ) M. L.
Cole, S. K. Furfari, M. Kloth, J. Organomet. Chem., 2009, 694
2934ꢀ2940; ( ) N. Marion, E. C. EscuderoꢀAdán, J. BenetꢀBuchholz,
E. D. Stevens, L. Fensterbank, M. Malacria, S. P. Nolan,
Organometallics, 2007, 26 3256ꢀ3259; ( ) C. Jones, D. P. Mills, R.
P. Rose, J. Organomet. Chem., 2006, 691, 3060ꢀ3064; ( ) R. J. Baker,
H. Bettentrup, C. Jones, Eur. J. Inorg. Chem., 2003, 13, 2446ꢀ2451;
) R. J. Baker, C. Jones,. Appl. Organomet. Chem., 2003, 17, 807ꢀ
808; ( ) R. J. Baker, R. D. Farley, C. Jones, M. Kloth, D. M. Murphy,
Chem. Commun., 2002, 11, 1196ꢀ1197; ( ) R. J. Baker, M. L. Cole,
C. Jones, M. F. Mahon, Dalton Trans., 2002, 1992ꢀ1996; ( ) R. J.
Baker, A. J. Davies, C. Jones, M. Kloth, J. Organomet. Chem., 2002,
656 203ꢀ210; C. D. Abernethy, M. L. Cole, C. Jones,
Organometallics, 2000, 19, 4852ꢀ4857; ( ) M. D. Francis, D. E.
Hibbs, M. B. Hursthouse, C. Jones, N. A. Smithies, Dalton Trans.,
1998, 19 3249ꢀ3254; ( ) D. E. Hibbs, M. B. Hursthouse, C. Jones, N.
A. Smithies, Chem. Commun., 1998, , 869ꢀ870; ( ) S. J. Black, D. E.
Hibbs, M. B. Hursthouse, C. Jones, K. M. A. Malik, N. A. Smithies,
Dalton. Trans., 1997, 22 4313ꢀ4319.
e
) A. R. Kennedy,
Computational details
,
9091ꢀ9099;
All calculations have been performed with the Amsterdam
Density Functional suite of programs, ADF.23ꢀ25 Gradientꢀ
corrected densityꢀfunctional calculations were based on the
local density approximation with Slater exchange26 and VWN
correlation.27 Gradient corrections for exchange and correlation
were those proposed by Becke28 and Perdew,29 respectively.
Valence electrons were described with an STO basis of tripleꢀζ
quality, augmented by one polarization function.30 Electrons of
the core shells (1s2s2p for Al, 1s2s2p3s3p for Ga,
1s2s2p3s3p3d4s4p for In, 1s2s2p for P, 1s2s2p for Si, 1s for C
and N) have been treated within the frozen core
approximation.23 Relativistic effects have been incorporated
based on the zeroꢀorder regular approximation.
(
f
g
h
i
j
7
(a
b
,
c
d
,
e
f
%VBur calculations parameters: All calculations were
performed on DFT optimized structures using the SambVca
program.16b The Ccarbene centre is coordinated at the origin of the
sphere with a distance equal to the fixed value of 2.0 Å. 3.50 Å
was selected as the value for the sphere radius; mesh spacing
for numerical integration was scaled to 0.05; hydrogen atoms
were omitted for the calculations; and bond radii was scaled by
1.17.
g
,
,
i
,
j
,
k
l
(
m
n
Notes and references
o
1
L. Cavallo, C. S. J. Cazin, in Nꢀheterocyclic Carbenes in Transition
Metal Catalysis and Organocatalysis, (Eds: Cazin, C. S. J.), Springer,
9
,
p
Netherlands, 2011, vol. 32
) D. Zhang, G. Zi, Chem. Soc. Rev., 2015, 44, 1898ꢀ1921; (
BelleminꢀLaponnaz, S. Dagorne, Chem. Rev., 2014, 114, 8747ꢀ8774;
) S. J. Hock, L.ꢀA. Schaper, W. A. Herrmann, F. E. Kühn, Chem.
Soc. Rev., 2013, 42, 5073ꢀ5090; ( ) V. P. Boyarskiy, K. V. Luzyanin,
V. Y. Kukushkin, Coord. Chem. Rev., 2012, 256, 2029ꢀ2056; ( ) H.
D. Velazquez, F. Verpoort, Chem. Soc. Rev., 2012, 41, 7032ꢀ7060.
) C. Bour, V. Gandon, Synlett., 2015, 26, 1427ꢀ1436; ( ) C.
Fliedel., G. Schnee, T. Avilés, S. Dagorne, Coord. Chem. Rev., 2014,
275, 63ꢀ86; ( ) C. Bour, V. Gandon, Coord. Chem. Rev., 2014, 279
43ꢀ57; ( ) Y. Wang, G. H. Robinson, Inorg. Chem., 2014, 53, 11815ꢀ
11832; ( ) S. Aldridge, A. J. Downs, in The Group 13 Metals
Aluminium, Gallium, Indium and Thallium: Chemical Patterns and
, pp. 1ꢀ22ꢀ.
,
(q)
2
(
a
b) S.
r
(c
,
s
d
8
t
e
,
3
4
(a
b
8
9
Rohm and Hass Electronic Materials LLC, Synthesis of
trimethylgallium, U.S. Patent 2006/47132 A1, 2006.
I. Pérez, J. P. Sestelo, L. A. Sarandeses, J. Am. Chem. Soc., 2001,
123, 4155ꢀ4160.
c
,
d
e
10 Horeglad et. al., previously reported the obtention of complex
1 and 2
via an indirect synthetic route,3c, 3e in which reaction of 2 equivalents
Peculiarities, (Eds: Aldridge, S.; Downs, A. J.), Wiley, UK, 2011
vol. 3.
,
of a NHC alkoxy dimethylgallium complex with an equal amount of
GaMe3 yielded complexes IMes•GaMe3 (
and a dimeric dialkylgallium byproduct (Scheme 2). As for complex
, it has been recently reported according to Scheme 1 to yield
SIPrGaMe3 and the structure was used to compare the
G) and SIMes•GaMe3 (J)
(a
) P. Horeglad, M. Cybularczyk, B. Trzaskowski, G. Z. Żukowska,
M. Dranka, J. Zachara, Organometallics, 2015, 34, 3480ꢀ3496; ( ) P.
Horeglad, O. Ablialimov, G. Szczepaniak, A. M. Dąbrowska, M.
Dranka, J. Zachara, Organometallics, 2014 , 33, 100ꢀ111; ( ) P.
Horeglad, G. Szczepaniak, M. Dranka, J. Zachara, Chem. Comm.
2012, 48, 1171ꢀ1173; ( ) J. H. Cotgreave, D. Colclough, G. Kociokꢀ
Köhn, G. Ruggiero, C. G. Frost, A. S. Weller, Dalton Trans., 2004,
10 1519ꢀ1520; ( ) J. D. Gorden, C. L. B. Macdonald, A. H. Cowley,
J. Organomet. Chem., 2002, 643ꢀ644, 487ꢀ489; ( ) X.ꢀW. Li, J. Su,
G. H. Robinson, Chem. Commun., 1996, 23, 2683ꢀ2684.
) M. Uzelac, A. HernánꢀGómez, D. R. Armstrong, A. R. Kennedy,
E. Hevia, Chem. Sci., 2015, , 5719ꢀ5728; ( ) G. Schnee, O. N. Faza,
b
4
(I)
coordination properties of G3c and J3e on their reactivity on
polymerization of racꢀLA.3c Nevertheless, these complexes have been
included in this report to maintain the rigor of our studies.
11 A. M. Magill, K. J. Cavell, B. F. Yates, J. Am. Chem. Soc., 2004,
126, 8717ꢀ8724.
c
,
d
,
e
f
12 H. V. Huynh, Y. Han, R. Jothibasu, J. A. Yang, Organometallics
2009, 28, 5395ꢀ5404.
,
5
6
(a
13 S. LeuthäuƁer, D. Schwarz, H. Plenio, Chem. Eur. J., 2007, 13
7195ꢀ7203.
,
6
b
D. Specklin, B. Jacques, L. Karmazin, R. Welter, C. S. López, S.
Dagorne, Chem. Eur. J., 2015, 21, 17959ꢀ17972.
(a) G. Schnee, D. Specklin, J.ꢀP. Djukic, S. Dagorne,
14 G. Davidson, in Characteristic Vibrations of Compounds of Main
Group Elements, (Eds: Davidson, G.), Royal Society of Chemistry,
UK, 2001, vol. 24, 217ꢀ267.
Organometallics, 2016, 35, 1726ꢀ1734; (
Lu, L. Falivene, Y. Li, R. Ganguly, L. Cavallo, F. García, Dalton
Trans., 2015, 44, 15166ꢀ15174; ( ) R. A. Musgrave, R. S. P.
Turbervill, M. Irwin, J. M. Goicoechea, Angew. Chem. Int. Ed., 2012,
51, 10832ꢀ10835; ( ) Y. Zhang, G. M. Miyake, E. Y.ꢀX. Chen,
b) M. M. Wu, A. M. Gill, Y.
15 (
2015, 17, 1866ꢀ1869; (
2011, , 69ꢀ77; (
Lough, J. Organomet. Chem., 2001, 617ꢀ618, 242ꢀ253 (
a
) S. J. Ryan, S. D. Schimler, D. C. Bland, M. S. Sanford, Org. Lett.
,
,
b
) X. Bantreil, S. P. Nolan, Nature Protocols
c
6
c
) M. K. Denk, J. M. Rodezno, S. Gupta, A. J.
) A. J.
d
d
10 | J. Name., 2012, 00, 1-3
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ARTICLE
Arduengo, R. Krafczyk, R. Schmutzler, Tetrahedron, 1999, 55
,
14523ꢀ1453.
16 (a) H. Clavier, S. P. Nolan, Chem. Comm., 2010, 46, 841ꢀ861; (b) A.
Poater, B. Cosenza, A. Correa, S. Giudice, F. Ragone, V. Scarano, L.
Cavallo, Eur. J. Inorg. Chem., 2009, 13, 1759ꢀ1766.
17 H. Jacobsen, A. Correa, A. Poater, C. Costabile, L. Cavallo, Coord.
Chem. Rev., 2009, 253, 687ꢀ703.
18 (
a
) N. Holzmann, A. Stasch, C. Jones, G. Frenking, Chem. Eur. J.,
) N. Holzmann, A. Stasch, C. Jones, G.
2013, 19, 6467ꢀ6479; (
b
Frenking, Chem. Eur. J., 2011, 17, 13517ꢀ13525
19 L. Falivene, L. Caporaso, L. Cavallo, H. Jacobsen, Dalton. Trans.,
2013, 42, 7281ꢀ7286.
20 SMART version 5.628, Bruker AXS Inc., Madison, WI, USA, 2001.
21 G. M. Sheldrick, SADABS V2014/4 (Bruker AXS Inc.), University
of Göttingen, Göttingen, Germany, 2014.
22 ‘SHELXTLꢀ2014/6 (Sheldrick, 2014); Bruker AXS Inc., Madison,
WI, USA, 2014.
23 E. J. Baerends, D. E. Ellis, P. Ros, Chem. Phys., 1973,
24 L. Versluis, T. Ziegler, J. Chem. Phys., 1988, 88, 322ꢀ328.
25 ( ) G. te Velde, F. M. Bickelhaupt, E. J. Baerends, C. F. Guerra, S. J.
A. van Gisbergen, J. G. Snijders, T. Ziegler, J. Comput. Chem., 2001,
22, 932ꢀ942;; ( ) C. F. Guerra, J. G. Snijders, G. te Velde, E. J.
Baerends, Theor. Chem. Acc., 1998, 99 391ꢀ403 SCM,
2, 41ꢀ51.
a
b
,
(c)
Theoretical Chemistry, Vrije Universiteit, Amsterdam, The
Netherlands, http://www.scm.com; ADF2008ꢀ01: Baerends, E. J. et
all.
26 J. C. Slater, Phys. Rev., 1951, 81, 385ꢀ390.
27 S. H. Vosko, L. Wilk, M. Nusair, Can. J. Phys., 1980, 58, 1200ꢀ1211.
28 A. D. Becke, Phys. Rev. A, 1988, 38, 3098ꢀ3100.
29 J. P. Perdew, Phys. Rev. B: Condens. Matter, 1986, 33, 8822ꢀ8827.
30 E. van Lenthe, E. J. Baerends, J. Comput. Chem., 2003, 24,1142ꢀ
1156.
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