Structural and spectroscopic studies of carbene and N-donor ligand complexes of group 13 hydrides and halides

Article abstract of DOI:10.1016/S0022-328X(02)01592-9

The syntheses of two Group 13 complexes of the sterically demanding carbene, 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene, (IPr), are reported, vis. [MX₃(IPr)] M = Al, X = H; M = In, X = Br; both of which have been structurally characterise

Full text of DOI:10.1016/S0022-328X(02)01592-9

Journal of Organometallic Chemistry 656 (2002) 203ꢁ210
/
www.elsevier.com/locate/jorganchem
Structural and spectroscopic studies of carbene and N-donor ligand
complexes of Group 13 hydrides and halides
Robert J. Baker, Aaron J. Davies, Cameron Jones *, Marc Kloth
Department of Chemistry, University of Wales, Cardiff, P.O. Box 912, Park Place, Cardiff CF10 3TB, UK
Received 9 April 2002; accepted 8 May 2002
Abstract
The syntheses of two Group 13 complexes of the sterically demanding carbene, 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene,
(IPr), are reported, vis. [MX3(IPr)] Mꢀ
reported is the crystal structure of the imidazolium salt [IPrH][InBr4], formed by the presence of adventitious water in the
preparation of the [InBr3(IPr)] adduct. The preparation of the complex [InBr3(IMes)], IMesꢀ1,3-bis(2,4,6-trimethylpheny)imida-
/
Al, Xꢀ
/
H; Mꢀ
/
In, Xꢀ/Br; both of which have been structurally characterised. Also
/
zol-2-ylidene, is described as are details of its crystal structure analysis. In addition, two indium tribromide adducts of nitrogen
donor ligands, namely a bulky diazabutadiene and quinuclidine have been investigated. The crystal structures of N,N?-1,4-bis(2,6-
diisopropylphenyl)diazabutadiene indium tribromide and bis(quinuclidine)indium tribromide are reported. # 2002 Elsevier Science
B.V. All rights reserved.
Keywords: Carbene; Indium halide; Aluminium hydride; N-donor; Crystal structures
1. Introduction
and [InX3{(CN(Pri)C2H2N(Pri)}n], Xꢀ
/
Cl or Br, nꢀ1
/
or 2 [9]. The stabilising properties of these carbene
ligands are perhaps best exemplified by [InH3(IMes)]
(dec. 115 8C) which is by far the most thermally robust
InH3 complex yet reported, a fact which has led to its
application in both organic [10] and inorganic synthesis
[11].
Herein, we report the preparation of a number of
related N-heterocyclic carbene and N-donor ligand
complexes of several Group 13 trihydride and trihalide
fragments, several of which have been crystallographi-
cally characterised.
Neutral ligands containing N, P, O or S donor atoms
show a rich variety of co-ordination complexes with
indium(III) halides [1]. Depending on the stoichiometry
employed, many geometries have been observed in the
solid state, e.g. [InI3(PHBu2t )] is distorted tetrahedral [2],
[InCl3(PMe3)2] is trigonal bipyramidal [3], whilst both
fac and mer isomers of [InCl3(OPMe3)3] have been
isolated [4]. There is also the possibility of ionic
complexes being formed as in [InI2(dmso)4][InI4]
(dmsoꢀdimethyl sulfoxide) [5].
/
The coordination chemistry of indium halides and
other Group 13 halides and hydrides has recently been
extended to complexes employing N-heterocyclic car-
bene ligands. In this area we have utilised such carbenes
as stabilising ligands in the formation of a variety of
2. Results and discussion
2.1. Carbene complexes
complexes, e.g. [MH3(IMes)], Mꢀ
[MCl3(IMes)], MꢀIn or
[MH3{(CN(Pri)C2H2N(Pri)}], Mꢀ
Al, Ga or In [8]
/
Ga or In [6];
Previous results from our laboratory have shown that
steric bulk is an important factor in the kinetic
/
Tl [7];
/
stabilisation of carbeneꢁInH3 complexes, e.g. [In-
/
H3(IMes)]. As such, it would be expected that the bulky
2,6-diisopropylphenyl substituted carbene (IPr) should
stabilise the InH3 fragment to an even greater extent
than IMes. However, following our published metho-
* Corresponding author. Tel.:
20874030
E-mail address: jonesca6@cardiff.ac.uk (C. Jones).
ꢂ
/
44-29-20874060; fax:
ꢂ/44-29-
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 5 9 2 - 9

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/
˚
Fig. 1. Molecular structure of compound 1. Selected bond lengths (A) and angles (8): Al(1)Ã
1.510(17), Al(1)ÃC(1) 2.0556(13), C(1)ÃN(1) 1.3562(15), C(1)ÃN(2) 1.3567(15), N(1)ÃC(3) 1.3824(15), N(1)Ã
1.3826(15), N(2)ÃC(4) 1.4474(15), C(2)ÃC(3) 1.3417(18), N(1)ÃC(1)ÃN(2) 103.86(10), C(1)ÃAl(1)ÃH(1a) 106.1(6), C(1)Ã
H(1a)ÃAl(1)ÃH(2a) 111.1(9), C(1)ÃAl(1)ÃH(3a) 104.6(6), H(1a)ÃAl(1)ÃH(3a) 113.9(9), H(2a)ÃAl(1)ÃH(3a) 114.3(9).
/
H(1a) 1.527(15), Al(1)Ã
C(16) 1.4488(14), N(2)Ã
Al(1)ÃH(2a) 106.0(6),
/
H(2a) 1.546(17), Al(1)Ã
/
H(3a)
/
/
/
/
/
/C(2)
/
/
/
/
/
/
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/
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/
/
dology [6] the product from the reaction of LiInH4 and
this carbene, [InH3(IPr)], proved to be of disappointing
thermal stability and slowly decomposed below ꢃ30 8C
/
in solution and thus was impossible to characterise. This
is possibly due to the close proximity of the isopropyl
groups to the hydride ligands in the complex which
could lead to decomposition via. metallation of the
isopropyl substituents by the InH3 unit. This has been
previously postulated for the complex [In-
H3{CN(Pri)C2H2N(Pri)}] [8]. In contrast, the 1:1 reac-
tion of IPr with either LiAlH4 or [AlH3(NMe3)] in
diethyl ether did afford the thermally stable alane
complex, [AlH3(IPr)] (1) in good yield (Scheme 1).
The infrared spectrum of 1 shows a broad, strong
stretch at 1729 cmꢃ1 confirming the presence of an
AlH3 unit. This is in the same region as other carbene
adducts of alane, e.g. [AlH3{CN(Pri)C2H2N(Pri)}]
n(AlÃ
/
H) 1730 cmꢃ1 [8]. Its proton NMR spectrum
does not show a resonance for the hydride ligands,
probably due to the quadrupolar nature of the alumi-
˚
Fig. 2. Molecular structure of compound 2. Selected bond lengths (A)
and angles (8): C(1)Ã
1.467(11), C(2)ÃC(3) 1.361(13), N(2)Ã
1.374(11), N(2)ÃC(16) 1.457(11), In(1)ÃBr(1) 2.4995(16), In(1)Ã
2.4862(16), In(1)ÃBr(3) 2.4699(17), In(1)Ã
C(1)ÃN(2) 108.0(7), C(1)ÃN(2)ÃC(3) 108.9(7), C(1)Ã
125.3(7), C(1)ÃN(1)ÃC(2) 109.3(7), C(1)ÃN(1)Ã
In(1)ÃBr(2) 111.16(6), Br(2)ÃIn(1)ÃBr(4) 107.27(9), Br(4)Ã
Br(3) 108.55(9), Br(3)ÃIn(1)ÃBr(1) 107.97(6).
/
N(1) 1.329(11), N(1)Ã
/
C(2) 1.367(11), N(1)Ã
/
C(4)
/
/
C(1) 1.339(10), N(2)Ã
/C(3)
/
/
/Br(2)
/
/
Br(4) 2.4814(19), N(1)Ã
/
/
/
/
/
N(2)Ã
/C(16)
/
/
/
/
C(4) 123.7(7), Br(1)Ã
/
/
/
/
/
In(1)Ã
/
Scheme 1.
/
/

R.J. Baker et al. / Journal of Organometallic Chemistry 656 (2002) 203ꢁ
/210
205
˚
Fig. 3. Molecular structure of compound 3. Selected bond lengths (A) and angles (8): C(1)Ã
1.407(12), N(1)ÃC(16) 1.449(13), C(2)ÃC(3) 1.320(13), N(2)ÃC(2) 1.397(11), N(2)ÃC(1) 1.322(12), N(2)Ã
In(1)ÃBr(2) 2.5000(12), In(1)ÃBr(3) 2.4999(13), N(1)ÃC(1)ÃN(2) 106.5(7), C(1)ÃN(2)ÃC(2) 109.8(8), C(1)Ã
110.3(8), C(1)ÃN(1)ÃC(16) 126.4(8), Br(1)ÃIn(1)ÃBr(2) 107.43(5), Br(2)ÃIn(1)ÃBr(3) 107.92(5), Br(3)ÃIn(1)Ã
113.6(3), C(1)ÃIn(1)ÃBr(2) 108.1(2), C(1)ÃIn(1)ÃBr(3) 112.2(3).
/
In(1) 2.212(8), C(1)Ã
C(4) 1.462(13), In(1)Ã
N(2)ÃC(4) 124.6(7), C(1)Ã
Br(1) 107.34(4), C(1)ÃIn(1)Ã
/
N(1) 1.331(12), N(1)Ã
/
C(3)
/
/
/
/
/
/
Br(1) 2.4935(14),
N(1)ÃC(3)
Br(1)
/
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nium, but there are two doublets arising from the
isopropyl methyl protons, indicating restricted rotation
of both the aryl and isopropyl substituents. The
compound is thermally robust but decomposes at
229 8C, a value which can be compared to the melting
angles are very similar to those seen in
[AlH3{CN(Pri)C2H2N(Pri)}] and [AlH3(IMes)].
The carbene, IPr, has also been used to prepare a
complex of indium tribromide. An initial reaction of IPr
with InBr3 in Et2O did not gave the expected 1:1 adduct,
[InBr3(IPr)], but instead the imidizolium salt [IPr-
H][InBr4] (2) which has been structurally characterised
point of the most stable carbeneꢁAlH3 complex, [Al-
/
H3(IMes)] (246 8C) [12]. The molecular structure of 1 is
shown in Fig. 1 and is consistent with its spectroscopic
data. The steric protection afforded by the bulky
carbene is obvious from the crystal structure; the two
diisopropylphenyl substituents are close to perpendicu-
lar to the imidazole ring and the isopropyl methyl
substituents are folded back from the metal centre.
The hydride ligands were located from difference maps
(Fig. 2). From our previous work on carbeneÃ
/
InX3
(XꢀCl, Br) compounds in which the formation of
/
similar imidazolium compounds has been observed
[9,14], it is thought that 2 probably arises from a trace
of water in the InBr3 starting material which reacts with
the carbene to give 2 and ‘InBr2OH’ as the reaction by-
product. The structure of 2 contains two crystallogra-
phically independent molecules in the asymmetric unit
which display very similar geometries so data for only
one will be discussed here. The tetrahedral InBrꢃ4 anion
has no interaction with the cation and the metric
parameters of the imidazole ring indicate a more
delocalised system than the heterocycle of the alane
and refined isotropically. The average AlÃ
/
H bond
˚
˚
length of 1.527 A is similar to the mean value (1.54 A)
for all crystallographically determined terminal AlÃ
bonds [13], whilst the angles about Al(1) indicate that it
is in a distorted tetrahedral environment. The AlÃ
/
H
/C
˚
bond length of 2.0556(13) A is close to those in both
˚
A]
[AlH3(IMes)]
[2.034(3)
i
[12]
and
complex, 1 [NÃ
/
CÃN angles 2 108.0(7); 1 103.86(10)8].
/
i
˚
[AlH3{CN(Pr )C2H2N(Pr )}] [2.046(5) A] [8]. The metric
parameters for the carbene ligand indicate some delo-
The reaction was repeated with carefully resublimed
InBr3 and the 1:1 adduct, [InBr3(IPr)] (3) was isolated in
low yield. The spectroscopic data for 3 are only slightly
calisation over the NCN fragment whilst the NÃ
/
CÃ
/
Al

206
R.J. Baker et al. / Journal of Organometallic Chemistry 656 (2002) 203ꢁ210
/
˚
equivalent (2.497 A average). The InÃ
/
C bond length is
very similar to that seen in [InBr3{CN(Pri)C2H2N(Pri)}]
˚
[2.212(8) and 2.199(5) A, respectively] but longer than
InÃC bonds in many indium alkyl complexes [e.g. 2.174
A in (trimethyl)quinuclidine indium) [15]]. The NÃCÃ
/
˚
/
/N
angle [106.5(7)8] is again indicative of a degree of
delocalisation over that fragment. As was the case for
the alane complex, 1, the aryl groups are almost
perpendicular to the imidazole ring and the isopropyl
methyl groups are directed away from the metal centre.
For the purposes of comparison the complex, [In-
Br3(IMes)] (4) was prepared using similar conditions.
The spectroscopic data are consistent with its proposed
structure which was confirmed by X-ray crystallogra-
phy. Again, it was found that there are two crystal-
lographically independent molecules in the asymmetric
unit, one of which is shown in Fig. 4. As expected, the
complex is monomeric and the bond lengths and angles
about the indium centre are similar to those in 3. It is
noteworthy that compound 4 is isomorphous and
isostructural with its known [InCl3(IMes)] analogue [6].
2.2. Nitrogen donor ligand complexes
An intermediate in the synthesis of the IPr carbene is
N,N?-bis(2,6-diisopropylphenyl)diazabutadiene (DAB)
and thus it was deemed of interest to synthesise the
InBr3 complex of this ligand. The reaction of DAB with
one equivalent of InBr3 in Et2O gave the 1:1 adduct, 5,
in good yield (Scheme 2). It is noteworthy that the same
product was obtained when the reaction was carried out
in a 1:2 stoichiometry. Both the 1H- and 13C-NMR
spectra suggest that the four isopropyl methyl groups
are chemically equivalent in solution. The molecular
structure of 5 is shown in Fig. 5. This represents the first
˚
Fig. 4. Molecular structure of compound 4. Selected bond lengths (A)
and angles (8): C(1)ÃIn(1) 2.195(5), C(1)ÃN(1) 1.355(7), N(1)ÃC(2)
1.385(7), N(1)ÃC(4) 1.427(7), C(2)ÃC(3) 1.344(9), N(2)ÃC(3) 1.392(8),
N(2)ÃC(1) 1.346(7), N(2)ÃC(13) 1.442(7), In(1)ÃBr(1) 2.4994(8),
In(1)ÃBr(2) 2.4935(8), In(1)ÃBr(3) 2.4947(9), N(1)ÃC(1)ÃN(2)
106.3(5), C(1)ÃN(2)ÃC(3) 109.5(5), C(1)ÃN(2)ÃC(13) 127.5(5),
C(1)ÃN(1)ÃC(2) 110.0(5), C(1)ÃN(1)ÃC(4) 126.4(5), Br(1)ÃIn(1)Ã
Br(2) 107.38(3), Br(2)ÃIn(1)ÃBr(3) 109.33(3), Br(3)ÃIn(1)ÃBr(1)
107.95(3), In(1)ÃBr(1) 112.54(14), C(1)ÃIn(1)ÃBr(2)
C(1)Ã
110.52(13), C(1)ÃIn(1)ÃBr(3) 109.03(14).
/
/
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/
structural characterisation of a diazabutadieneꢁ
/MX3
/
/
/
/
/
/
/
/
/
/
complex (MꢀGroup 13 metal, Xꢀhalide) reported in
/
/
/
/
/
/
the literature. The compound crystallises in the chiral
space group P1 with four crystallographically indepen-
dent molecules in the asymmetric unit. The geometries
of these are significantly different, ranging from dis-
torted square based pyramidal to distorted trigonal
pyramidal. Despite these differences, comment will
only be made on one of the molecules here. It is
/
/
/
/
/
/
shifted from those for the free carbene with the
exception of the carbene carbon resonance which cannot
be observed in its 13C-NMR spectrum, presumably due
1
to the quadrupolar nature of indium. As in 1, the H-
NMR spectrum displays two doublets for the isopropyl
methyl protons suggesting restricted rotation of the aryl
and isopropyl substituents. An X-ray crystal structure
determination was carried out and it was found that the
asymmetric unit contains two crystallographically in-
dependent molecules with no significant geometrical
differences between them. The ORTEP diagram for one
of these is shown in Fig. 3. The compound is monomeric
and the indium atom sits in a slightly distorted tetra-
hedral environment with the InÃ/Br bond lengths almost
Scheme 2.

R.J. Baker et al. / Journal of Organometallic Chemistry 656 (2002) 203ꢁ
/210
207
interesting, in light of these solid state geometrical
differences, that in solution all the methyl groups of 5
are chemically equivalent which strongly suggests that
there is a fluxional process occurring in solution
involving the decomplexation/complexation of the
DAB molecule from the InBr3 unit. Cooling solutions
of 5 to ꢃ50 8C did not lead to a resolution of the
/
spectrum and all resonances broadened only slightly,
presumably because the fluxional process is rapid even
at this temperature.
The chirality of the crystal structure arises from an
‘end to end’ packing of the molecules of 5 which gives
rise to an infinite helical chain. The geometry around
In(1) is distorted square based pyramidal with the two
Br ligands trans to the nitrogen centres and at similar
distances from the indium atom [In(1)Ã
/
Br(1) 2.532(2)
˚
and In(1)Ã
ligand [In(1)Ã
are comparable but slightly longer than the mean for all
crystallographically characterised InÃN bond lengths,
2.294 A [13]. There is an acute NÃInÃN angle at
71.1(4)8 and the CÃN and CÃC bond lengths within
/
Br(3) 2.539(2) A] with one closer apical Br
˚
/
Br(2) 2.505(2) A]. The InÃ
/N bond lengths
/
˚
/
/
/
/
the DAB ligand suggest that there is little delocalisation
over this ligand.
Quinuclidine (quin) has been used as a ligand in the
formation of aluminium and gallium halide complexes
but structurally characterised examples of indium triha-
lide adducts are unknown. In order to prepare such a
complex two equivalents of quinuclidine were reacted
with one equivalent of InBr3 in Et2O which yielded the
complex, [InBr3(quin)2] (6) in good yield. Interestingly,
the analogous 1:1 adduct could not be prepared as only
˚
Fig. 5. Molecular structure of compound 5. Selected bond lengths (A)
and angles (8): In(1)ÃN(1) 2.332(14), N(1)ÃC(2) 1.27(2), N(1)ÃC(15)
1.45(2), C(1)ÃC(2) 1.57(2), N(2)ÃC(1) 1.24(2), N(2)ÃC(3) 1.46(2),
In(1)ÃN(2) 2.314(12), In(1)ÃBr(1) 2.532(2), In(1)ÃBr(2) 2.505(2),
In(1)ÃBr(3) 2.539(2), N(1)ÃIn(1)ÃN(2) 71.1(4), N(1)ÃIn(1)ÃBr(1)
88.8(3), Br(1)ÃIn(1)ÃBr(3) 95.37(7), Br(3)ÃIn(1)ÃN(2) 89.4(3),
Br(1)ÃIn(1)ÃBr(2) 108.98(8), Br(3)ÃIn(1)ÃBr(2) 107.34(8), N(1)Ã
In(1)ÃBr(2) 101.5(3), N(2)ÃIn(1)ÃBr(2) 100.0(3).
/
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/
/
˚
Fig. 6. Molecular structure of compound 6. Selected bond lengths (A) and angles (8): In(1)Ã
/
Br(1) 2.5271(8), In(1)Ã
/
Br(2) 2.5254(5), In(1)ÃN(1)
/
2.364(3), N(1)ÃIn(1)ÃN(1?) 178.40(14), Br(2)ÃIn(1)ÃBr(2?) 117.86(3), Br(1)ÃIn(1)ÃBr(2) 121.07(2).
/
/
/
/
/
/

208
R.J. Baker et al. / Journal of Organometallic Chemistry 656 (2002) 203ꢁ210
/
the 2:1 complex crystallised when the reaction was
carried out in a 1:1 stoichiometry. This observation is
consistent with the preference of indium to attain
coordination numbers of 5 or 6 as opposed to 4 [1].
The spectroscopic data for 6 were of limited value in
determining its structure as they closely resemble those
for the free quin ligand. As a result an X-ray structural
analysis was carried out and the molecular structure of 6
is shown in Fig. 6. The complex is trigonal bipyramidal
with the bromide ligands in the equatorial sites and the
amine ligands in the axial positions. A similar arrange-
4.1. [AlH3(IPr)] (1)
To a cold (ꢃ
/
78 8C) solution of LiAlH4 (0.05 g, 1.32
mmol) in Et2O (20 cm3) was added a cold solution of IPr
(0.51 g, 1.31 mmol) in Et2O (40 cm3) over 5 mins. This
was allowed to warm to room temperature (r.t.) and
stirred overnight. The solvent was removed in vacuo and
the white residue extracted with C6H5CH3 (2ꢄ
Concentration and cooling to ꢃ35 8C yielded colour-
/
40 cm3).
/
less crystals of 1 (0.41 g, 74%). M.p. 229ꢁ234 8C (dec);
/
1H-NMR (400 MHz, C6D6, 300 K): d 1.17 (d JHH
ꢀ6
/
3
3
Hz, 12H, CH3), 1.54 (d, JHH
ment has been seen in [GaHCl2(quin)2] [16] and
˚
ꢀ6 Hz, 12H, CH3), 2.80
/
[AlClH2(quin)2] [17]. Both the InÃ
/
Br (2.5959 A average)
(sept 3JHH
(d, 3JHH
ꢀ
/
6Hz, 4H, CH), 6.55 (s, 2H, NC2H2N), 7.22
and InÃ
/
ꢀ
/
7 Hz, 4H, m-Ph), 7.36 (t, 3JHH
ꢀ
/
7 Hz, 2H, p-
˚
N bond lengths [2.364(3) A] are unexceptional
being close to those in related complexes, e.g [InBr3(tri-
methyltriazacyclononane)] [18].
Ph); 13C-NMR (100.6 MHz, C6D6, 300 K): d 23.4
(CH3), 24.5 (CH3), 28.75 (CH), 123.26 (p-Ph), 123.86
(m-Ph), 126.56 (o-Ph), 130.15 (ipso-Ph), 145.5
(NC2H2N); MS APCI: m/z (%) 417.2 [Mꢃ
389.2 [IprHꢂ, 100]; IR (Nujol, cmꢃ1): n 1061 (sh), 1112
(s), 1212 (s), 1257 (s), 1322 (s), 1729 (br s, AlÃH).
/
Hꢂ, 5],
3. Conclusion
/
The very bulky carbene, 1,3-bis(2,6-diisopropylphe-
nyl)imidazol-2-ylidene, has been used to prepare the
Group 13 hydride and halide complexes, [AlH3(IPr)]
and [InBr3(IPr)], which have been structurally charac-
terised. Also structurally characterised is the related
[InBr3(IMes)] adduct. In addition, two nitrogen donor
ligand complexes of InBr3 have been prepared and
structurally characterised, viz. [InBr3(DAB)] and [In-
Br3(quin)2]. We are currently investigating the reduction
of the InBr3 adducts in order to prepare subvalent
indium halide complexes. The results of these investiga-
tions will be reported in forthcoming publications.
4.2. [IPrH][InBr4]×
/
(Et2O)0.5 (2)
To a solution of IPr (0.54 g, 1.4 mmol) in Et2O (10
cm3) was added a solution of InBr3 (0.50 g, 1.4 mmol) in
Et2O (10 cm3). After stirring for 2 h the solution was
concentrated and cooled to ꢃ
crystals of 2 (0.11 g, 9%). M.p. 187ꢁ
NMR (400 MHz, CDCl3, 300 K): d 1.15 (d, JHH
/
35 8C to yield colourless
1
/
189 8C (dec); H-
3
ꢀ7
/
3
Hz, 12H, CH3), 1.26 (d, JHH
(sept 3JHH
7 Hz, 4H, CH), 7.86 (s, 2H, NC2H2N), 7.30
(d, 3JHH 8 Hz, 4H, m-Ph), 7.51 (t, 3JHH
8 Hz, 2H, p-
ꢀ/7 Hz, 12H, CH3), 2.38
ꢀ
/
ꢀ
/
ꢀ
/
Ph), 8.42 (s, 1H NCHN); 13C-NMR (100.6 MHz, C6D6,
300 K): d 23.1 (CH3), 26.1 (CH3), 29.1 (CH), 124.8 (p-
Ph), 126.6 (m-Ph), 131.9 (o-Ph), 136.5 (ipso-Ph), 145.0
(NCN), 145.3 (NC2H2N); IR (Nujol, cmꢃ1): n 1594 (m),
1328 (m), 1212 (m), 1117 (m), 1062 (m) 800 (w);
C29H42Br4InN2O0.5 requires: C, 40.45; H, 4.92; N,
3.25. Found: C, 41.69; C, 4.77; N, 3.45%.
4. Experimental
All manipulations were carried out using standard
Schlenk and glove box techniques under an atmosphere
of high purity argon. The solvents Et2O, C6H5CH3 and
THF were distilled over either potassium or Naꢁ
/K alloy
4.3. [InBr3(IPr)] (3)
then freeze/thaw degassed prior to use. CH2Cl2 was
purified by distillation from CaH2 under a dinitrogen
To a solution of IPr (0.54 g, 1.4 mmol) in Et2O (10
cm3) was added a solution of InBr3 (0.50 g, 1.4 mmol) in
Et2O (10 cm3). After stirring for 2 h the solution was
1
atmosphere. H- and 13C-NMR spectra were recorded
on Bruker DXP400 or JEOL Eclipse 300 spectrometers
in deuterated solvents and were referenced to the
residual 1H resonances of the solvent used. Mass spectra
were recorded using a VG Fisons Platform II instrument
under APCI conditions. Microanalyses were carried out
by the Warwick Microanalytical Service. M.p.s were
determined in sealed glass capillaries under argon and
are uncorrected. InBr3 was purchased from Aldrich and
resublimed before use. The compounds IMes [19], IPr
[20] and DAB [20] were prepared by literature methods
and all other materials were used as received.
concentrated and cooled to ꢃ35 8C to yield colourless
/
crystals of 3 (0.11 g, 11%). M.p. 187 8C; 1H-NMR (400
3
MHz, CDCl3, 300 K): d 1.10 (d, JHH
ꢀ7 Hz, 12H,
/
3
CH3), 1.35 (d, JHH
3JHH
7 Hz, 4H, CH), 7.86 (s, 2H, NC2H2N), 7.31 (d,
3JHH
ꢀ8 Hz, 2H, p-
ꢀ/7 Hz, 12H, CH3), 2.48 (sept
ꢀ
/
3
ꢀ
/
8 Hz, 4H, m-Ph), 7.57 (t, JHH
/
Ph); 13C-NMR (100.6 MHz, C6D6, 300 K) d 24.1 (CH3),
24.8 (CH3), 29.3 (CH), 125.1 (p-Ph), 126.7 (m-Ph), 129.4
(o-Ph), 132.7 (ipso-Ph), 145.0 (NC2H2N); MS APCI: m/
z (%) 663 [Mꢃ
Brꢂ, 41], 388 (IPrꢂ, 100); IR (Nujol,
/

R.J. Baker et al. / Journal of Organometallic Chemistry 656 (2002) 203ꢁ
/210
209
cmꢃ1): n 1568 (m), 1328 (m), 1257 (m), 1117 (m), 1062
(m).
NCH); 13C-NMR (100.1 MHz, C6D6, 300 K): d 23.5
(CH3), 28.9 (CH), 124.0 (m-Ar), 124.5 (p-Ar), 138.8 (o-
Ar), 146.4 (ipso-Ar), 163.6 (CN); MS APCI: m/z (%):
4.4. [InBr3(IMes)] (4)
649 [Mꢃ
Brꢂ, 2], 376 (DABꢂ, 5), 333 (DAB-Priꢂ, 100);
/
IR (Nujol, cmꢃ1): n 1654 (m), 1594 (m), 1172 (s), 1107
(m), 1042(m), 936 (m); C26H36Br3N2In requires: C,
42.71; H, 4.96; N, 3.83%. Found: C, 41.51; H, 4.98; N,
3.55%.
To a solution of InBr3 (0.50 g, 1.44 mmol) in Et2O (10
cm3) was added a solution of IMes (0.43 g, 1.44 mmol)
in Et2O (10 cm3). This was stirred for 2 h and the solvent
removed in vacuo. The white residue was extracted with
CH2Cl2 (2ꢄ
/
20 cm3) and concentrated. Placement at ꢃ
/
4.6. [InBr3(quin)2] (6)
30 8C overnight yielded large blocks of 4 (0.818 g, 88%).
1
M.p. 208ꢁ
/
210 8C (dec); H-NMR (400 MHz, CDCl3,
To a solution of quinuclidine (0.31 g, 2.8 mmol) in
Et2O (10 cm3) was added a solution of InBr3 (0.50 g, 1.4
mmol) in Et2O (10 cm3). The reaction was stirred for 2 h
to give a white precipitate, which was isolated by
300 K) d 2.04 (s, 12H, o-CH3), 2.15 (s, 6H, p-CH3), 6.75
(s, 4H, m-CH), 7.32 (s, 2H, NCHCHN); 13C-NMR
(100.6 MHz, CDCl3, 300 K): d 17.96 (o-CH3), 21.35 (p-
CH3), 125.69 (NC2H2N), 132.31 (p-Ar), 133.91 (o-Ar),
135.24 (m-Ar), 141.21 (ipso-Ar); MS APCI: m/z (%)
filtration and extracted into C6H5O3 (2ꢄ
Concentration and cooling to ꢃ35 8C gave colourless
crystals of 6 (0.67 g, 83%). M.p. 178ꢁ
180 8C; 1H-NMR
/
20 cm3).
/
579.1 [Mꢃ
/
Brꢂ, 100], 277 [IMesꢂ, 15]; IR (Nujol,
/
cmꢃ1): n 1593 (sh), 1465 (s), 1378 (s), 1234 (s), 1122
(s), 1029 (s), 927 (m), 860 (sh), 753 (sh), 727 (m), 691
(m); C21H24Br3N2In requires: C, 38.20%; H, 3.67; N,
4.25. Found: C, 38.12; H, 3.62; N, 4.05%.
(400 MHz, CDCl3, 300 K): d 1.88 (br m, 12H, CH2),
2.17 (br m, 2H, CH), 3.24 (br m, 12H, CH2N); 13C-
NMR (100.1 MHz, CDCl3, 300 K): d 19.6 (CH), 23.1
(CH2), 46.8 (NCH2); MS APCI: m/z (%) 385 [Mꢃ
Brꢂ,
/
13], 274 [InBrꢂ2 ; 21]; 112 [quinꢂ, 100]; IR (Nujol,
cmꢃ1): n 1323 (m), 1281 (w), 1258 (w), 1044 (m), 979
(m), 771(m).
4.5. [InBr3(DAB)]×
/
(OEt2)0.5 (5)
To a solution of DAB (0.53 g, 1.4 mmol) in Et2O (10
cm3) was added a solution of InBr3 (0.50 g, 1.4 mmol) in
Et2O (10 cm3). This was stirred for 2 h to give a deep red
solution, which was filtered, concentrated and cooled to
4.7. Crystallographic studies
Crystals of 1ꢁ6 suitable for X-ray structure determi-
/
ꢃ
/
35 8C yielding red crystals of 5 (0.16 g, 31% on ether
nation were mounted in silicone oil. Crystallographic
measurements were made using a Nonius Kappa CCD
diffractometer. The structures were solved by direct
methods and refined on F2 by full-matrix-least-squares
1
free sample). M.p. 178ꢁ
/
180 8C; H-NMR (400 MHz,
3
C6D6, 300 K) d 1.28 (d, 12H, JHH
ꢀ7 Hz, CH3), 3.25
/
3
(sept, JHH
3
7 Hz, 2H, CH), 7.16 (d, 4H, JHH
ꢀ
/
ꢀ
/
7 Hz,
7 Hz, p-ArH), 8.45 (s, 2H,
3
m-ArH), 7.18 (t, 2H, JHH
ꢀ
/
(SHELX-97) [21] using all unique data. All non-hydrogen
Table 1
Crystal data for compounds 1, 2×(Et2O)0.5, 3, 4, 5×(Et2O)0.5 and 6
1
2×(Et2O)0.5
3
4
5×(Et2O)0.5
6
Chemical formula
Formula weight
T (K)
C27H39AlN2
418.58
150(2)
C29H42Br4N2InO0.5
861.11
150(2)
C27H36Br3N2In C21H24Br3N2In C28H41Br3N2InO0.5
743.13
150(2)
C14H26Br3N2In
576.92
150(2)
658.97
150(2)
768.18
150(2)
Crystal system
Space group
Monoclinic
P21/n
Monoclinic
P21/c
Orthorhombic
Pbca
Orthorhombic
Pca21
Triclinic
P1
Orthorhombic
Pbcn
˚
a (A)
10.287(2)
18.396(4)
14.707(3)
90
19.322(4)
20.090(4)
19.322(4)
90
16.759(3)
20.352(4)
35.424(7)
90
16.502(3)
16.541(3)
17.896(4)
90
10.456(2)
15.351(3)
21.508(4)
95.81(3)
101.71(3)
105.11(3)
3219.9(11)
4
8.9280(18)
12.017(2)
17.058(3)
90
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
104.06(3)
90
90.99(3)
90
90
90
90
90
90
90
3
˚
V (A )
Z
2699.8(9)
4
0.089
7500(3)
8
4.912
12082(4)
16
4.768
4884.9(17)
8
5.884
1830.2(6)
4
7.835
m (Moꢁ
/
Ka) (mmꢃ1
)
4.476
49 392
Reflections collected
Unique reflections (Rint
R1 (I ꢀ2s(I))
39 261
5290 (0.0328) 13 646 (0.1046)
105 988
110 551
11 885 (0.1438)
0.0852
0.1716
73 059
22 032
)
11 164 (0.0753)
0.0399
0.0808
23 638 (0.0785)
0.0833
0.2217
2024 (0.0607)
0.0360
0.0779
0.0387
0.0987
0.0767
0.2352
/
wR? (all data)
2

210
R.J. Baker et al. / Journal of Organometallic Chemistry 656 (2002) 203ꢁ210
/
[2] N.W. Alcock, I.A. Degan, O.W. Howarth, M.G.H. Wallbridge, J.
Chem. Soc. Dalton Trans. (1992) 2775.
atoms are anisotropic with H-atoms included in calcu-
lated positions (riding model) except for the hydride
ligands of 1 which were located from difference maps
and refined isotropically. Although the data for 2, 3 and
5 were of poor quality the crystal structures of these
compounds unambiguously confirm their gross mole-
cular frameworks. Crystal data, details of data collec-
tions and refinement are given in Table 1.
[3] N.W. Alcock, I.A. Degan, S.M. Roe, M.G.H. Wallbridge, Acta
Crystallogr. Sect. C 48 (1992) 995.
[4] W.T. Robinson, C.J. Wilkins, Z. Zeying, J. Chem. Soc. Dalton
Trans. (1990) 219.
[5] F.W.B. Einstein, D.G. Tuck, J. Chem. Soc. Chem. Commun.
(1970) 1182.
[6] C.D. Abernathy, M.L. Cole, C. Jones, Organometallics 19 (2000)
4852.
[7] M.L. Cole, A.J. Davies, C. Jones, J. Chem. Soc. Dalton Trans.
(2001) 2451.
5. Supplementary material
[8] M.D. Francis, D.E. Hibbs, M.B. Hursthouse, C. Jones, N.A.
Smithies, J. Chem. Soc. Dalton Trans. (1988) 3249.
[9] S.J. Black, D.E. Hibbs, M.B. Hursthouse, C. Jones, K.M.A.
Malik, N.A. Smithies, J. Chem. Soc. Dalton Trans. (1997) 4313.
[10] C.D. Abernathy, M.L. Cole, A.J. Davies, C. Jones, Tetrahedron
Lett. 41 (2000) 7567.
Crystallographic data (excluding structure factors) for
the structures of 1ꢁ
Cambridge Crystallographic Data Centre, CCDC nos.
183314ꢁ183319 for compounds 1ꢁ6. Copies of this
/6 have been deposited with the
/
/
[11] C. Jones, Chem. Commun. (2001) 2293.
[12] A.J. Arduengo, III, H.V.R. Dias, J.C. Calabrese, F. Davidson, J.
Am. Chem. Soc. 114 (1992) 9724.
information may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge, CB2
[13] Value obtained from a survey of the Cambridge Crystallographic
Database.
1EZ, UK (Fax:
it@ccdc.cam.ac.uk or www:http://www.ccdc.cam.ac.uk).
ꢂ44-1223-336033; email: depos-
/
[14] D.E. Hibbs, M.B. Hursthouse, C. Jones, N.A. Smithies, Main
Group Chem. 2 (1998) 293.
[15] J.L. Atwood, S.G. Bott, N.C. Means, C.M. Means, Inorg. Chem.
26 (1987) 1466.
Acknowledgements
[16] B. Luo, V.G. Young, W.L. Gladfelter, Chem. Commun. (1999)
123.
We thank the EPSRC for funding (studentships for
AJD and MK and postdoctoral fellowship for RJB).
[17] C. Jones, P.C. Junk, M.L. Cole, Main Group Chem. 24 (2001)
249.
[18] G.R. Willey, D.R. Aris, J.V. Haslop, W. Errington, Polyhedron
20 (2001) 423.
[19] A.J. Arduengo, III, H.V.R. Dias, R.L. Harlow, M. Kline, J. Am.
Chem. Soc. 114 (1992) 5530.
References
[20] L. Jafarpour, E.D. Stevens, S.P. Nolan, J. Organomet. Chem. 606
(2000) 49.
[21] G.M. Sheldrick, SHELX-97, University of Gottingen, 1997.
[1] D.G. Tuck, in: A.J. Downs (Ed.), Chemistry of Aluminium,
Gallium, Indium and Thallium (chapter 8 and references therein),
¨
Blackie, Glasgow, 1993, pp. 430ꢁ473.
/