Bidentate N-heterocyclic carbene complexes of group 13 trihydrides and trihalides

Article abstract of DOI:10.1039/b200500j

Treatment of the potentially chelating bis-carbene, 1,2-ethylene-3,3′-di-tert-butyl-diimidazole-2,2′-diylidene, EtIBu^t, with [MH₃(NMe₃)], M= Al, Ga, In, in a 1:1 or 1:2 stoichiometery led to good yields of the metal rich 2

Full text of DOI:10.1039/b200500j

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Bidentate N-heterocyclic carbene complexes of Group 13
trihydrides and trihalides
Robert J. Baker,a Marcus L. Cole,a Cameron Jones*a and Mary F. Mahonb
a Department of Chemistry, University of Wales, Cardiff, P. O. Box 912, Park Place, Cardiff,
UK CF10 3TB
b Department of Chemistry, University of Bath, Bath, UK BA2 7AY
Received 14th January 2002, Accepted 8th March 2002
First published as an Advance Article on the web 5th April 2002
Treatment of the potentially chelating bis-carbene, 1,2-ethylene-3,3Ј-di-tert-butyl-diimidazole-2,2Ј-diylidene, EtIBut,
with [MH3(NMe3)], M = Al, Ga, In, in a 1 : 1 or 1 : 2 stoichiometery led to good yields of the metal rich 2 : 1 adducts,
[(MH3)2(µ-EtIBut)]. These complexes have been spectroscopically characterised and the X-ray crystal structures of
two (M = Al or In) obtained. In contrast, the 1 : 1 or 1 : 2 reactions of EtIBut with MX3, M = In or Tl, X = Br or Cl,
led to the 1 : 1 adducts, [MX3(EtIBut)]. The X-ray crystal structure of one of these, [InBr3(EtIBut)], shows the ligand
to act in a chelating mode, taking up equatorial positions of an trigonal bipyramid. The reactions of EtIBut with
MCl3, M = Al or Ga, led to decomposition and in the aluminium reaction the major product of the decomposition
process was the bis-imidazolium salt, [EtIButH2][Cl]2, which has also been crystallographically characterised. Several
related reactions are described.
plexes, e.g. [AlH2(L)][AlH4], in combination with polydentate
Introduction
donors, L = pmdeta or tetramethylcyclam.12 The results of our
Since the isolation of the first room temperature stable
endeavours in this area are reported herein.
N-heterocyclic carbene (NHC) in 1991 these compounds have
been widely utilised in the synthesis of transition metal com-
plexes,1 many of which have been found to be catalytically
active.2 Their activity in this respect has been explained by
the now recognised close analogy between NHCs and nucleo-
philic tertiary phosphine ligands.3 This analogy has also been
exploited in the synthesis of an ever growing number of
unusually stable main group metal–carbene complexes.4 In this
arena we have utilised the stabilising properties of monodentate
NHCs in the preparation of a series of indium and thallium
halide complexes, 1 and 2,5–7 but also in the synthesis of
remarkably stable Group 13 hydride complexes. Most signifi-
cant of these are the first indium trihydride complexes, 38 and
4,6 the latter of which does not decompose until 115 ЊC in the
solid state and whose chemistry we are systematically studying.
It is noteworthy that as part of a broader study we have pre-
pared a range of tertiary phosphine and amine complexes of
Results and discussion
InH3, e.g. [InH3(PCy3)], Cy = cyclohexyl, and compared their
chemistry to that of compounds such as 3 and 4.9
Group 13 trihydride complexes
We wished to extend our studies in this area by exploring the
interaction of a bidentate carbene, viz. 1,2-ethylene-3,3Ј-di-tert-
butyl-diimidazole-2,2Ј-diylidene, EtIBut, with Group 13 tri-
hydrides and trihalides. The reason for this was that EtIBut has
been shown to behave similarly to bis-phosphine ligands in that
it can act in a chelating mode when complexed to transition
metal fragments.3a,10 We were intrigued to see if carbene che-
lation would occur in Group 13 complexes. In the case of
aluminium and gallium trihydrides only the bridging mode
has previously been observed in related monomeric or poly-
meric bis-phosphine complexes, e.g. [(MH3)2{µ-(Pri)2PCH2CH2-
P(Pri)2}], M = Al or Ga, [{(AlH3)[µ-(Pri)2PCH2CH2P(Pri)2]}∞].11
If, however, EtIBut could chelate MH3 fragments, the possi-
bility of forming ionic complexes, e.g. [MH2(EtIBut)][MH4],
would exist, especially considering the fact that the AlH3 frag-
ment is known to form similar, very thermally stable ionic com-
Treatment of EtIBut with two equivalents of [MH3(NMe3)],
M = Al, Ga, In, in either diethyl ether or toluene at low temper-
ature led to the precipitation of 5–7 in good yields upon warm-
ing to room temperature (Scheme 1). These compounds were
only sparingly soluble in most common solvents but could be
recrystallised from large volumes of diethyl ether or toluene.
Interestingly, when the reactions were carried out in a 1 : 1
stoichiometry the same products resulted and the unreacted
EtIBut could be recovered. In addition, 7 has been prepared in
good yield via the reaction of EtIBut with two equivalents of
LiInH4 with a concomitant elimination of LiH, in a similar
fashion to the preparation of 4.6
The fact that only the “alane rich” 2 : 1 complex, 5, was
formed under any stoichiometry of reactants is of interest as
related bis-phosphine ligands nearly always form polymeric
1992
J. Chem. Soc., Dalton Trans., 2002, 1992–1996
This journal is © The Royal Society of Chemistry 2002
DOI: 10.1039/b200500j

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but interestingly three broad overlapping absorptions can be
detected in the spectra of 5 and 6. These have not been specific-
ally assigned and attempts to obtain solution IR data failed due
to the low solubility of both complexes.
The X-ray crystal structures of 5 and 7 were obtained (Figs.
1 and 2, Table 1) though 6 could only be obtained as a micro-
Scheme 1 Reagents and conditions: i, MH3(NMe3), –NMe3; ii, LiInH4,
–LiH.
1 : 1 complexes with alane due to the preference for the alumin-
ium centre of the AlH3 fragment to attain a coordination num-
ber of five or above.11 The “indane rich” compound, 7, is even
more surprising given our recent observation that the indane
fragment has an even greater tendency toward hypervalent
structures than alane.9a Compound 6, however, was expected as
the greater electronegativity of gallium relative to Al or In has
meant that the GaH3 fragment generally will not attain a
coordination number greater than four, even in the presence of
bis-phosphine ligands. These observations can be explained by
the highly nucleophilic nature of the carbene ligands in these
complexes, which apparently electronically satisfy the metal
centres. Evidence for this proposal comes from the fact that
treating 5 or 7 with an excess of EtIBut led to no reaction. In
addition, treating 7 with an excess of PEt3 at Ϫ10 ЊC in diethyl
ether did not lead to the formation of the five-coordinate com-
plex, [{(Et3P)InH3}2(µ-EtIBut)] but instead to rapid decom-
position to indium metal, PEt3 and free EtIBut. The cause of
this decomposition is presumed to be a ligand substitution
reaction leading to [InH3(PEt3)] which is known to rapidly
decompose above Ϫ30 ЊC.9a
Fig. 1 Molecular structure of compound 5. Selected bond lengths (Å)
and angles (Њ): Al(1)–C(1) 2.067(2), Al(1)–H(1) 1.52(3), Al(1)–H(2)
1.52(3), Al(1)–H(3) 1.47(3), N(1)–C(1) 1.362(3), N(1)–C(2) 1.463(3),
N(2)–C(4) 1.383(3), N(2)–C(1) 1.357(3), N(1)–C(3) 1.375(3), C(3)–C(4)
1.345(3), N(2)–C(1)–N(1) 104.21(18), C(1)–Al(1)–H(1) 105.0(12), C(1)–
Al(1)–H(2) 107.7(12), C(1)–Al(1)–H(3) 112.1(11), H(1)–Al(1)–H(2)
112.4(17), H(1)–Al(1)–H(3) 110.2(16), H(2)–Al(1)–H(3) 109.3(16).
Both compounds 5 and 6 proved to be moderately thermally
stable (dec. 122–124 ЊC and 168–171 ЊC) but less so than other
carbene–alane or gallane complexes. If a comparison is drawn
with the thermally stable indane complex, 4 (dec. 115 ЊC), com-
plex 7 is disappointingly thermally frail (dec. 10–12 ЊC). In
1
Fig. 2 Molecular structure of compound 7. Selected bond lengths (Å)
and angles (Њ): In(1)–C(1) 2.3069(16), N(1)–C(1) 1.355(2), N(1)–C(2)
1.376(2), N(2)–C(1) 1.362(2), N(2)–C(3) 1.384(2), C(2)–C(3) 1.346(3),
In(1)–H(1) 1.73(2), In(1)–H(2) 1.73(2), In(1)–H(3) 1.73(2), N(1)–C(1)–
N(2) 104.58(14), C(1)–In(1)–H(1) 105.7(11), C(1)–In(1)–H(2) 106.1(9),
C(1)–In(1)–H(3) 105.3(9), H(1)–In(1)–H(2) 113.0(15), H(1)–In(1)–H(3)
115.0(15), H(2)–In(1)–H(3) 110.9(13).
addition, when its decomposition is followed by H NMR in
toluene, it deposits indium metal above Ϫ15 ЊC and a multitude
of resonances appear which are indicative of EtIBut ligand
decomposition, possibly via ring opening of the imidazole
heterocycles. This contrasts with 4 which decomposes in toluene
to give indium metal, H2 gas and regenerates the free carbene
intact.6
The spectroscopic data for 5–7 are consistent with their
proposed formulations. Their 1H NMR spectra display the
expected resonances for the carbene ligand and in the cases
of 6 and 7 broad resonances were observed at 4.61 ppm and
6.06 ppm respectively, each of which integrates for six hydride
ligands. The resonance for the hydride ligands of 5 was too
broad to be observed, probably because of the quadrupolar
nature of the aluminium centre to which they are attached. It
proved impossible to obtain meaningful 13C NMR data for
6 and 7 due to their very low solubility in all common solvents.
The IR spectra (Nujol mulls) of 5–7 displayed strong, broad
characteristic M–H stretches centred at 1757, 1804 and 1643
cmϪ1 respectively. A very similar pattern has been observed for
the monodentate carbene-MH3 complexes, [MH3{CN(Pri)C2-
crystalline solid. The two structurally characterised compounds
are isostructural but not isomorphous. They are centro-
symmetric monomers and show the EtIBut ligand bridging two
MH3 fragments in a similar fashion to that described for the
alane rich bis-phosphine complex, [(AlH3)2{µ-(Pri)2PCH2CH2-
P(Pri)2}].11 The hydride ligands of both complexes were located
from difference maps and refined isotropically. The average
In–H distance in 7 (1.73 Å) compares well to the mean of
all structurally characterised terminal In–H bond lengths
(1.70 Å).13 In contrast the average Al–H distance in 5 (1.50 Å) is
close to that in [AlH3{CN(Pri)C2Me2N(Pri)}] (1.52 Å)8b but
shorter than the mean for all structurally characterised Al–H
bonds (1.61 Å).13 This difference is not significant given the
errors involved in these bond lengths. Notwithstanding the
inherant problems that the refinement of hydrogen atom
positions using X-ray data pose, the broad indications are that
the geometry about the metal centre in 5 is close to tetrahedral
(av. C–Al–H 108.2Њ, av. H–Al–H 110.6Њ) whilst in 7 it is slightly
flattened tetrahedral (av. C–In–H 105.7Њ, av. H–In–H 113.0Њ).
Me2N(Pri)}] M = Al 1730 cmϪ1, Ga 1775 cmϪ1, In 1640 cmϪ1 8b
;
which reflects the strength of the M–H bonds involved. It is
worth noting that no structure is normally seen in the M–H
stretching bands of Group 13 trihydride complexes which
can be greater than 200 cmϪ1 wide. This is indeed the case for 7
J. Chem. Soc., Dalton Trans., 2002, 1992–1996
1993

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Table 1 Crystal data for compounds 5, 7, 9ؒ2CH2Cl2 and 11ؒCH2Cl2
5
7
9ؒ2CH2Cl2
11ؒCH2Cl2
Chemical formula
FW
Crystal system
Space group
C16H32Al2N4
334.42
Monoclinic
P21/n
C16H32In2N4
510.10
C18H30Br3Cl4InN4
798.81
Monoclinic
P21/n
C17H30Cl4N4
432.25
Orthorhombic
C2/c
Triclinic
¯
P 1
a/Å
b/Å
c/Å
α/Њ
6.0020(2)
25.0350(8)
6.8670(2)
90
100.031(2)
90
5.6110(1)
8.2530(2)
11.6770(3)
85.4570(10)
85.4100(10)
76.2580(10)
522.56(2)
1
12.0470(3)
14.3610(3)
16.8110(4)
90
105.887(1)
90
13.401(3)
15.748(3)
11.461(2)
90
90
90
β/Њ
γ/Њ
V/Å3
1016.06(6)
2
2797.33(11)
4
2281.4(8)
4
Z
T /K
150(2)
0.15
13427
2391 (0.0871)
0.0533
150(2)
2.21
13602
5444 (0.0446)
0.0294
150(2)
5.53
32746
6384 (0.0721)
0.0475
150(2)
0.53
14903
2244 (0.0395)
0.0311
0.0771
µ(Mo-Kα)/mmϪ1
Reflections collected
Unique reflections/Rint
R 1 (I > 2σ(I ))
wRЈ2 (all data)
0.1431
0.0689
0.1187
These geometries can be compared to the coordination
environment of the indium centre in [InH3(PCy3)] which is
much more flattened [av. P–In–H 101.4Њ. av. H–In–H 116.2Њ].9
This observation is in line with the greater nucleophilicity
of NHCs relative to tertiary phosphines and explains why
AlH3 and InH3 will not form five-coordinate complexes with
NHCs whilst they both readily do so with tertiary phosphines.
Finally, the C–M bond lengths and NCN angles in 5 and 7 are
in the normal region for carbene–Group 13 metal trihydride
complexes.8b
It was thought worthy to investigate the reaction of a bulky
bis-phosphine, Cy2PCH2CH2PCy2, with [InH3(NMe3)] for pur-
poses of comparison. When this reaction was carried out under
either a 1 : 1 or 1 : 2 stoichiometry the polymeric compound,
[{(InH3)(Cy2PCH2CH2PCy2)}∞] 8, precipitated from the reac-
tion mixture in high yield. This result suggests that indane will
not form a metal rich 2 : 1 adduct with this phosphine as it does
with EtIBut, presumably because of the lower nucleophilicity of
the phosphine ligand. Moreover, it again confirms the prefer-
ence for hypervalency of the InH3 fragment over the AlH3
fragment as the latter does form an alane rich complex,
[(AlH3)2(Cy2PCH2CH2PCy2)], with this ligand.11
Scheme 2 Reagents and conditions: i, MX3, THF; ii, AlCl3, Et2O.
solvent. The reactions of InBr3 or TlCl3 with 0.5 equivalents of
EtIBut also yielded 9 and 10 as the only products, which shows
these are favourable to metal rich 2 : 1 adducts analogous to
5–7. This again gives evidence that InBr3 is a stronger Lewis
1
acid than InH3. The H and 13C NMR spectra of 9 are con-
sistent with its structure though the very low solubility of 10 in
CD2Cl2 made it impossible to obtain a 13C NMR spectrum on
1
this compound. Indeed, its H NMR spectrum was weak and
Although 8 has low solubility in diethyl ether it is sufficiently
soluble in toluene to allow NMR data to be obtained. These are
consistent with its 1 : 1 formulation and its 1H NMR spectrum
displays a broad peak at 5.76 ppm which was assigned to the
three hydride ligands. Their presence was confirmed by the IR
spectrum of the complex which shows a very strong, broad
absorption centred at 1657 cmϪ1 which is in the normal In–H
stretching region for indane complexes.14 Finally, the complex
exhibits reasonable thermal stability in that it decomposes at
18–20 ЊC (cf. 50 ЊC for [InH3(PCy3)]) giving an indium mirror
and the free phosphine ligand.
unavoidable precipitation of the sample lead to considerable
line broadening and a subsequent lack of resolution regarding
the expected 4JTlH coupling at the 4,5-positions of the imidazol-
2-ylidene groups which we have observed in similar systems.7
The X-ray crystal structure of 9ؒ2CH2Cl2 (Fig. 3, Table 1) was
obtained and this shows the molecule to be monomeric with the
carbene ligating the indium centre in a chelating mode and tak-
ing up two equatorial sites of a distorted trigonal bipyramid in
a similar fashion to that seen in the bis(carbene)–indium halide
complexes, 2.5 It is worthy of note that the EtIBut ligand has
previously been observed to act in a chelating mode in two
square planar nickel complexes, [cis-NiMe2(EtIBut)]3 and [cis-
NiCl(PMe3)(EtIBut)][BPh4].10 Both the In–C and In–Br bond
lengths in 9 are unexceptional though the axial In–Br bonds are
significantly longer (2.737 Å av.) than the equatorial In–Br
bond [2.5367(7) Å]. Obviously, it cannot be sure that 10 adopts
the same coordination mode as 9 but this seems likely given the
available spectroscopic evidence and the similar properties of
the two compounds.
Group 13 trihalide complexes
We have previously shown that monodentate NHCs can form
five-coordinate complexes with indium trihalides, 2, in which
the two carbene ligands take up equatorial positions of a tri-
gonal bipyramidal coordination environment.5 This suggests
that the InX3, X = Cl or Br, fragments are stronger Lewis acids
than InH3 which only forms four-coordinate complexes with
carbenes. We wished to explore the interaction of EtIBut with a
range of Group 13 halides to investigate any differences there
may be between the resulting complexes and 5–7.
Accordingly, treatment of THF solutions of either InBr3 or
TlCl3 with equimolar amounts of EtIBut resulted in the quanti-
tative precipitation of the 1 : 1 adducts 9 and 10 (Scheme 2).
Both compounds were sparingly soluble in dichloromethane
but only 9 could be recrystallised from large volumes of this
The 1 : 1 reactions of AlCl3 and GaCl3 with EtIBut proved
less successful and in the latter case led to numerous unidenti-
fied products. The former reaction did not yield a 1 : 1 adduct
but instead gave a moderate yield of the bis-imidazolium
dichloride, 11. It is not known how this forms but it presumably
involves the aluminium analogue of 9 as an intermediate. We
have previously noted that imidazolium salts can form in the
reactions of carbenes with Group 13 halides when water is
1994
J. Chem. Soc., Dalton Trans., 2002, 1992–1996

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Experimental
General
All manipulations were carried out using standard Schlenk and
glove box techniques under an atmosphere of high purity argon
or dinitrogen. The solvents diethyl ether, toluene and THF were
distilled over either potassium or Na/K alloy then freeze/thaw
degassed prior to use. CH2Cl2 was purified by distillation from
1
CaH2 under a dinitrogen atmosphere. H, 13C and 31P NMR
spectra were recorded on Bruker DPX400 or Jeol Eclipse 300
spectrometers in deuterated solvents and were referenced to the
1
residual H resonances of the solvent used (1H NMR) or to
external 85% H3PO4, 0.0 ppm (31P NMR). Mass spectra were
recorded using a VG Fisons Platform II instrument under
APCI conditions. Melting points were determined in sealed
glass capillaries under argon, and are uncorrected. Repro-
ducible microanalyses of 5–8 could not be obtained due to their
thermal and/or extreme air sensitivity. Microanalyses on 9 and
11 could not be obtained as they readily lost dichloromethane
of crystallisation over time. The starting materials EtIBut,10
[LiInH4]8 and [MH3(NMe3)] M = Al,16 Ga17 or In,8 were pre-
pared by literature procedures. All other reagents were used as
received.
Fig. 3 Molecular structure of compound 9. Selected bond lengths (Å)
and angles (Њ): In(1)–C(8) 2.233(6), In(1)–C(1) 2.236(6), In(1)–Br(2)
2.5367(7), In(1)–Br(1) 2.7290(7), In(1)–Br(3) 2.7449(7), N(1)–C(1)
1.357(8), N(2)–C(1) 1.345(7), N(3)–C(8) 1.344(7), N(4)–C(8) 1.351(7),
N(2)–C(1)–N(1) 105.2(5), N(3)–C(8)–N(4) 105.8(5), C(8)–In(1)–C(1)
112.5(2), C(8)–In(1)–Br(2) 123.68(15), C(1)–In(1)–Br(2) 123.86(15),
C(8)–In(1)–Br(1) 92.98(15), C(1)–In(1)–Br(1) 85.46(15), Br(2)–In(1)–
Br(1) 91.04(2), C(8)–In(1)–Br(3) 84.71(15), C(1)–In(1)–Br(3) 92.97(15),
Br(2)–In(1)–Br(3) 92.44(2), Br(1)–In(1)–Br(3) 176.50(2).
present.5,15 However, in this case efforts were made to rigorously
exclude moisture and still 11 was formed in a moderate yield.
Presumably, the acidic imidazolium protons originate from the
solvent and the chloride from the AlCl3 fragment. The outcome
of the aluminium in this reaction could not be determined.
[(AlH3)2(ꢀ-EtIBut)] 5. EtIBut (0.20 g, 0.73 mmol) in toluene
(55 ml) was added dropwise to a solution of [AlH3(NMe3)]
(0.13 g, 1.46 mmol) in toluene (35 ml) at Ϫ50 ЊC over 15 min.
The resulting slurry was warmed to room temperature and
stirred for 3 h whereupon volatiles were removed in vacuo. The
residue was extracted with toluene (50 ml), filtered and the fil-
trate placed at Ϫ30 ЊC yielding colourless prisms of 5 overnight
(0.18 g, 74%). mp 122–124 ЊC dec.; 1H NMR (400 MHz, C6D6,
300 K) δ 1.58 (s, 18H, But), 4.53 (s, 4H, CH2), 6.46 (s, 2H, CH),
6.65 (s, 2H, CH); 13C NMR (100.6 MHz, C6D6, 300 K) δ 31.7 (s,
C(CH3)3), 46.7 (s, CH2), 53.4 (s, C(CH3)3), 115.9 (s, CH), 119.2
(s, CH); MS APCI: m/z (%) 138 [{H2EtIBut}2ϩ, 100], 303 [{M Ϫ
AlH4}ϩ, 35]; IR (Nujol) ν/cmϪ1 1713 (s br, Al–H str.), 1762 (s br,
Al–H str.), 1797 (s br, Al–H str.).
1
The H NMR spectrum of 11 displayed a resonance for the
imidazolium protons at the 2-positions of the heterocycles and
the carbon centres at the same positions resonate in the normal
region for imidazolium salts. To confirm the nature of 11 its
X-ray crystal structure was obtained and found to include one
molecule of dichloromethane of solvation for each mole-
cule of the salt (Fig. 4, Table 1). The bond lengths and angles
within the heterocycles suggest full delocalisation and all other
geometrical parameters are unexceptional.
[(GaH3)2(ꢀ-EtIBut)] 6. EtIBut (0.41 g, 1.52 mmol) in diethyl
ether (25 ml) was added dropwise to a solution of [GaH3-
(NMe3)] (0.40 g, 3.04 mmol) in diethyl ether (35 ml) at Ϫ50 ЊC
over 15 min. The resulting slurry was warmed to room temp-
erature and stirred overnight and the precipitate isolated by
filtration. The residue was washed with diethyl ether (2 × 5 ml)
and extracted with toluene (50 ml). The extract was placed at
Ϫ30 ЊC yielding 6 as a colourless powder (0.88 g, 59%). mp
1
168–171 ЊC dec.; H NMR (400 MHz, C6D6, 300 K) δ 1.20 (s,
18H, But), 3.95 (s, 4H, CH2), 4.61 (br. s, 6H, GaH3), 5.31 (s, 2H,
CH), 5.35 (s, 2H, CH); MS APCI: m/z (%) 138 [{H2EtIBut}2ϩ
,
100]; IR (Nujol) ν/cmϪ1 1849 (s br, Ga–H str.), 1808 (s br, Ga–H
str.), 1757 (s br, Ga–H str.).
Fig. 4 Molecular structure of compound 11. Selected bond lengths
(Å) and angles (Њ): N(1)–C(1) 1.3274(18), N(1)–C(2) 1.3862(18), N(2)–
C(1) 1.3360(19), N(2)–C(3) 1.3804(19), C(2)–C(3) 1.345(2), N(1)–C(1)–
N(2) 108.23(12), C(1)–N(1)–C(2) 108.71(12), C(1)–N(2)–C(3)
108.88(12), C(3)–C(2)–N(1) 107.20(13), C(2)–C(3)–N(2) 106.98(12).
[(InH3)2(ꢀ-EtIBut)] 7. (i) EtIBut (0.19 g, 0.69 mmol) in
diethyl ether (25 ml) was added dropwise to a solution of
[InH3(NMe3)] (ca. 1.38 mmol) in diethyl ether (35 ml) at
Ϫ50 ЊC over 15 min. The resulting slurry was warmed to Ϫ30 ЊC
and stirred for 3 h whereupon it was filtered. The filtrate was
placed at Ϫ30 ЊC yielding colourless rods of 7 overnight (0.17
g, 48%). mp 10–12 ЊC dec. (ii) EtIBut (0.15 g, 0.55 mmol) in
diethyl ether (20 ml) was added dropwise to a solution of
LiInH4 (ca. 1.10 mmol) in diethyl ether (35 ml) at Ϫ78 ЊC over
15 min. The resulting slurry was warmed to Ϫ30 ЊC and stirred
for 3 h whereupon it was filtered. The filtrate was placed at
Ϫ30 ЊC yielding colourless rods of 7 overnight (0.16 g, 58%).
mp 10–12 ЊC dec. 1H NMR (300 MHz, C6D5CD3, 223 K)
δ 1.31 (s, 18H, But), 4.53 (s, 4H, CH2), 5.46 (s, 2H, CH), 6.06
(br s, 6H, InH3), 6.22 (s, 2H, CH); IR (Nujol) ν/cmϪ1 1643 (s br,
In–H str.).
Conclusions
In summary, we have described the reactions of the bis-carbene
ligand EtIBut with a series of Group 13 trihydride and trihalide
fragments. The results have shown that the MH3 fragments
form only monomeric, four-coordinate metal rich complexes,
[(MH3)2(µ-EtIBut)], whereas InBr3 and TlCl3 form mono-
meric complexes in which the carbene ligand coordinates the
metal in a chelating mode. The observed differences have been
explained in terms of the relative Lewis acidities of the MH3
and MX3, X = halide, fragments. Work continues in our
group on the stabilisation and application of InH3 and TlH3
complexes.
J. Chem. Soc., Dalton Trans., 2002, 1992–1996
1995

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[{(InH3)(Cy2PCH2CH2PCy2)}∞] 8. Cy2PCH2CH2PCy2 (1.07 g,
2.53 mmol) in diethyl ether (30 ml) was added dropwise to
a solution of [InH3(NMe3)] (ca. 2.54 mmol) in diethyl ether
(70 ml) at Ϫ70 ЊC over 15 min. The resulting slurry was warmed
to Ϫ30 ЊC and stirred for 3 h whereupon the precipitate of 8 was
isolated by filtration and washed with cold diethyl ether (2 ×
measurements were made using a Nonius Kappa CCD dif-
fractometer. The structures were solved by direct methods and
refined on F 2 by full matrix least squares (SHELX-97)18 using
all unique data. All non-hydrogen atoms are anisotropic with
H-atoms included in calculated positions (riding model), except
the hydride ligands in 7 and all hydrogen atoms in 5 which were
located from difference maps and refined isotropically. Two
molecules of dichloromethane of solvation are included in the
crystal lattice of 9 and one molecule of dichloromethane in the
lattice of 11. Crystal data, details of data collections and
refinements are given in Table 1. The molecular structures of
the complexes are depicted in Figs. 1–4 and show ellipsoids at
the 30% probability level.
1
10 ml) (1.23 g, 90%). mp 18–20 ЊC dec.; H NMR (400 MHz,
C6D5CD3, 270 K) δ 1.02–2.05 (unresolved m, 44H ϩ 4H, Cy ϩ
C2H4), 5.76 ppm (br s, 3H, InH3); 13C NMR (100.6 MHz,
1
C6D5CD3, 270 K) δ 21.3 (s, C2H4), 28.0 (d, CH, JPC 23.1 Hz),
2
30.1 (s, CH2), 31.3 (s, CH2), 34.4 (d, CH2, JPC 12.9 Hz); 31P
NMR (121.5 MHz, C6D5CD3, 270 K) δ 1.45 (s); MS APCI:
m/z (%) 212 [{Cy2PCH2CH2PCy2}H2ϩ, 100]; IR (Nujol) ν/cmϪ1
1657 (s br, In–H str.).
CCDC reference numbers 177618–177621.
See http://www.rsc.org/suppdata/dt/b2/b200500j/ for crystal-
lographic data in CIF or other electronic format.
[InBr3(EtIBut)] 9. EtIBut (0.22 g, 0.80 mmol) in THF (20 ml)
was added dropwise to a solution of InBr3 (0.29 g, 0.82 mmol)
in THF (30 ml) at Ϫ50 ЊC over 15 min. The resulting slurry was
warmed to room temperature and stirred overnight whereupon
volatiles were removed in vacuo. The residue was extracted with
dichloromethane (50 ml), filtered and the filtrate concentrated
to ca. 30 ml. Placement at Ϫ30 ЊC overnight yielded colourless
Acknowledgements
We gratefully acknowledge financial support from EPSRC
(studentships for M.L.C and postdoctoral fellowship for
R.J.B). We thank the EPSRC Mass Spectrometry Service for
the accurate mass measurement on compound 10.
1
prisms of 9 (0.21 g, 41%). mp 159 ЊC; H NMR (400 MHz,
CD2Cl2, 300 K) δ 1.61 (s, 18H, But), 5.20 (s, 4H, CH2), 7.20
(s, 2H, CH), 8.50 (s, 2H, CH); 13C NMR (100.6 MHz, CD2Cl2,
300 K) δ 30.5 (s, C(CH3)3), 47.2 (s, CH2), 61.8 (s, C(CH3)3),
118.9 (s, CH), 124.8 (s, CH); MS APCI: m/z (%) 138 [{H2EtI-
But}2ϩ, 100], 549 [{M Ϫ Br}ϩ, 46]; IR (Nujol) ν/cmϪ1 782 (s),
1129 (s), 1289 (s), 1375 (s).
References
1 W. A. Herrmann and C. Köcher, Angew. Chem., Int. Ed. Engl., 1997,
36, 2162 and references therein.
2 e.g. (a) A. A. D. Tulloch, A. A. Danopolous, R. P. Tooze, S. M.
Cafferkey, S. Kleinhenz and M. B. Hursthouse, Chem. Commun.,
2000, 1247; (b) D. S. McGuinness and K. J. Cavell, Organometallics,
2000, 19, 741; (c) J. Huang and S. P. Nolan, J. Am. Chem. Soc., 1999,
121, 9889; (d ) W. A. Herrmann, M. Elison, J. Fischer, C. Kocher
and G. R. J. Artus, Angew. Chem., Int. Ed. Engl., 1995, 34, 2371
and references therein.
3 (a) R. E. Douthwaite, M. L. H. Green, P. J. Silcock and P. T. Gomes,
Organometallics, 2001, 20, 2611; (b) K. Öfele, W. A. Herrmann,
D. Mihalios, M. Elison, E. Herdtweck, W. Scherer and J. Mink,
J. Organomet. Chem., 1993, 459, 177 and references therein.
4 C. J. Carmalt and A. H. Cowley, Adv. Inorg. Chem., 2000, 50, 1.
5 S. J. Black, D. E. Hibbs, M. B. Hursthouse, C. Jones, K. M. A. Malik
and N. A. Smithies, J. Chem. Soc., Dalton Trans., 1997, 4313.
6 C. D. Abernethy, M. L. Cole and C. Jones, Organometallics, 2000,
19, 4852.
[TlCl3(EtIBut)] 10. EtIBut (0.28 g, 1.02 mmol) in THF
(30 ml) was added dropwise to a solution of TlCl3 (0.61 g,
1.97 mmol) in THF (30 ml) at Ϫ50 ЊC over 15 min. The result-
ing slurry was warmed to room temperature and stirred over-
night whereupon the precipitate was isolated by filtration,
washed with THF (30 ml) and dried in vacuo to yield 10 as
1
a colourless powder. (0.55 g, 92%). mp 132 ЊC dec.; H NMR
(400 MHz, CD2Cl2, 300 K) δ 1.58 (s, 18H, But), 5.17 (s, 4H,
CH2), 7.03 (s, 2H, CH), 8.42 (s, 2H, CH); MS APCI: m/z (%)
138 [{H2EtIBut}2ϩ, 100], 310 [{EtIButCl}ϩ, 41], 550 [{M Ϫ
Cl}ϩ, 23]; IR (Nujol) ν/cmϪ1 817 (m), 1207 (s), 1325 (m), 1555
(s); accurate mas FAB m/z [M ϩ Hϩ] calc. 585.1045, found
585.1045.
7 M. L. Cole, A. J. Davies and C. Jones, J. Chem. Soc., Dalton Trans.,
2001, 2451.
8 (a) D. E. Hibbs, M. B. Hursthouse, C. Jones and N. A. Smithies,
Chem. Commun., 1998, 869; (b) M. D. Francis, D. E. Hibbs, M. B.
Hursthouse, C. Jones and N. A. Smithies, J. Chem. Soc., Dalton
Trans., 1998, 3249.
9 (a) M. L. Cole, D. E. Hibbs, C. Jones and N. A. Smithies, J. Chem.
Soc., Dalton Trans., 2000, 545; (b) D. E. Hibbs, C. Jones and
N. A. Smithies, Chem. Commun., 1999, 185.
10 R. E. Douthwaite, D. Haüssinger, M. L. H. Green, P. J. Silcock,
P. T. Gomes and A. M. Martins, Organometallics, 1999, 18, 4584.
11 (a) M. G. Gardiner and C. L. Raston, Coord. Chem. Rev., 1997, 166,
1; (b) C. Jones, G. A. Koutsantonis and C. L. Raston, Polyhedron,
1993, 12, 1829 and references therein.
12 J. L. Atwood, K. D. Robinson, C. Jones and C. L. Raston, J. Chem.
Soc., Chem. Commun., 1991, 1697.
[EtIButH2][Cl]2 11. EtIBut (0.20 g, 0.73 mmol) in diethyl
ether (20 ml) was added dropwise to a solution of AlCl3 (0.10 g,
0.72 mmol) in diethyl ether (30 ml) at Ϫ78 ЊC over 15 min. The
resulting pale yellow slurry was warmed to room temperature
and stirred overnight whereupon the precipitate was isolated by
filtration, washed with diethyl ether (2 × 5 ml) and extracted
into CH2Cl2 (40 ml). Concentration of the extract and cooling
to Ϫ30 ЊC yielded colourless prisms of 11 (0.09 g, 36%). mp
1
132 ЊC dec.; H NMR (400 MHz, D6-dmso, 300 K) δ 1.64 (s,
18H, But), 4.85 (s, 4H, CH2), 7.81 (s, 2H, CH), 8.15 (s, 2H, CH),
9.72 (s, 2H, NCHN); 13C NMR (100.6 MHz, D6-dmso, 300 K)
δ 29.5 (s, C(CH3)3), 45.6 (s, CH2), 60.1 (s, C(CH3)3), 120.1
(s, CH), 123.2 (s, CH), 153.5 (s, NCHN); IR (Nujol) ν/cmϪ1
1562(s), 1470(sh), 1372(s), 1255(s), 1106(s), 1014(s), 799(s).
13 Value obtained from a survey of the Cambridge Crystallographic
Database.
14 C. Jones, Chem. Commun., 2001, 2293.
15 D. E. Hibbs, M. B. Hursthouse, C. Jones and N. A. Smithies, Main
Group Chem., 1998, 2, 293.
16 J. K. Ruff and M. F. Hawthorne, J. Am. Chem. Soc., 1960, 82, 2141.
17 D. F. Shriver and A. E. Shirk, Inorg. Synth., 1977, 17, 45.
18 G. M. Sheldrick, SHELXL-97, University of Göttingen, 1997.
Structure determinations
Crystals of 5, 7, 9 and 11 suitable for X-ray structure deter-
mination were mounted in silicone oil. Crystallographic
1996
J. Chem. Soc., Dalton Trans., 2002, 1992–1996