Hydroalumination of bis(alkynyl)silanes: Generation of chelating lewis acids, their application in the coordination of chloride ions and a 1,1-carbalumination reaction

Article abstract of DOI:10.1002/ejic.201100890

Treatment of diphenyl-diethynylsilanes, (H₅C₆) ₂Si(C=C-R′)₂ (R′ = -C₆H ₅, -4-Me-C₆H₄), with two equivalents of dialkylaluminium hydrides, R₂Al-H (R = -CMe₃, -CH ₂CMe₃), afforded the corresponding dialkenylsilanes (3-5) by hydroalumination. The mixed alkenyl-alkynyl compounds resulting from the reduction of only one C=C triple bond occurred as intermediates. Two of these (1 and 2) were isolated and characterized by crystal structure determinations. They show close interactions of the α-carbon atoms of the ethynyl groups with the coordinatively unsaturated aluminium atoms and a cis arrangement of H and Al atoms across the C=C double bonds. cis/trans Rearrangement took place upon the formation of the dialkenyl species 3-5 with an all-trans configuration of the alkenyl groups. These compounds have two tricoordinate aluminium atoms and are ideally preorganized to be applied as chelating Lewis acids, as was shown with the chelating coordination of chloride ions (compound 6). Rearrangement and 1,1-carbalumination was observed upon heating of a mixed alkenyl-alkynylsilane (7). A silacyclobutene derivative (8) was isolated, which has a SiC₃ heterocycle and an endo- and an exocyclic C=C double bond. Quantum chemical calculations give insight into the reaction mechanism. Chelating Lewis acids containing two coordinatively unsaturated, tricoordinate aluminium atoms were obtained from a facile route by the twofold hydroalumination of dialkynylsilanes. An intermediately formed alkenyl-alkynylsilane gave a silacyclobutene derivative by 1,1-carbalumination.

Full text of DOI:10.1002/ejic.201100890

FULL PAPER
DOI: 10.1002/ejic.201100890
Hydroalumination of Bis(alkynyl)silanes: Generation of Chelating Lewis Acids,
Their Application in the Coordination of Chloride Ions and a
1,1-Carbalumination Reaction
Werner Uhl,*[a] Denis Heller,[a] Jutta Kösters,[a] Ernst-Ulrich Würthwein,[b] and
Nugzar Ghavtadze[b]
Keywords: Aluminum / Lewis acids / Organoelement compounds / Heterocycles
Treatment of diphenyl–diethynylsilanes, (H5C6)2Si(CϵC–RЈ)2
(RЈ = –C6H5, –4-Me–C6H4), with two equivalents of dialkyl-
aluminium hydrides, R2Al–H (R = –CMe3, –CH2CMe3), af-
forded the corresponding dialkenylsilanes (3–5) by hydro-
alumination. The mixed alkenyl–alkynyl compounds re-
sulting from the reduction of only one CϵC triple bond oc-
curred as intermediates. Two of these (1 and 2) were isolated
and characterized by crystal structure determinations. They
show close interactions of the α-carbon atoms of the ethynyl
groups with the coordinatively unsaturated aluminium atoms
and a cis arrangement of H and Al atoms across the C=C
double bonds. cis/trans Rearrangement took place upon the
formation of the dialkenyl species 3–5 with an all-trans con-
figuration of the alkenyl groups. These compounds have two
tricoordinate aluminium atoms and are ideally preorganized
to be applied as chelating Lewis acids, as was shown with
the chelating coordination of chloride ions (compound 6). Re-
arrangement and 1,1-carbalumination was observed upon
heating of a mixed alkenyl–alkynylsilane (7). A silacyclobut-
ene derivative (8) was isolated, which has a SiC3 heterocycle
and an endo- and an exocyclic C=C double bond. Quantum
chemical calculations give insight into the reaction mecha-
nism.
many cases, the acceptor atoms occupy geminal positions
at a bridging carbon atom, which results in relatively
strained four-membered heterocycles upon coordination of
single atom donors. Therefore, we were very much inter-
ested in synthesizing corresponding compounds that have
larger spacers between the acceptor functions in order to
gain a higher flexibility in their backbones and their coordi-
nating properties. The twofold hydroalumination of silicon-
centred dialkynes seemed to be a suitable method for their
preparation.
Introduction
Molecular oligoacceptors (chelating Lewis acids) have
found some interest in recent research because they are po-
tentially applicable in phase-transfer processes, in catalysis
or in molecular recognition.[1] Compounds that have two or
more coordinatively unsaturated, tricoordinate aluminium
or gallium atoms in a single molecule are particularly suit-
able to act as such inverted chelating ligands. In previous
investigations with a sterically, highly shielded methylene-
bridged dialuminium compound, R2Al–CH2–AlR2 [R =
CH(SiMe3)2],[2] we observed the effective coordination of
different anions, such as nitrate, nitrite, hydride, hydroxide,
acetate etc., by the formation of ether soluble adducts.[3]
Twofold hydroalumination or hydrogallation of alkynes[4] is
a facile alternative method for the generation of such Lewis
acids possessing a geminal arrangement of two acceptor
functions. The resulting compounds were found to coordi-
nate halide, thiolate or benzoate anions.[5] The efficacy of
the chelating coordination of hydride ions by two alumin-
ium atoms was impressively shown by the formation of per-
sistent carbocations through C–H bond activation.[6] In
Results and Discussion
Hydroalumination of Dialkynylsilanes (H5C6)2Si(CϵC–RЈ)2
Treatment of dialkyl- or diphenyldialkynylsilanes,
R2Si(CϵC–C6H5)2, with equimolar quantities of dineopen-
tyl-, bis(tert-butyl)- or bis[bis(trimethylsilyl)methyl]alumin-
ium hydride afforded the mixed alkenyl–alkynylsilanes by
hydroalumination of one of their CϵC triple bonds.[7] In
most cases, the cis addition products were isolated, which
have the Al and H atoms on the same side of the resulting
C=C double bonds. Only the two sterically less-shielded ad-
dition products show spontaneous cis/trans isomerization,
which, in accordance with previous observations and quan-
tum chemical calculations, requires intermolecular acti-
vation.[8] With the exception of the bis(trimethylsilyl)methyl
compounds, we observed an interesting close intramolecu-
[a] Institut für Anorganische und Analytische Chemie der Uni-
versität Münster,
Corrensstraße 30, 48149 Münster, Germany
Fax: +49-251-8336660
E-mail: uhlw@uni-muenster.de
[b] Organisch-chemisches Institut der Universität Münster,
Corrensstraße 40, 48149 Münster, Germany
Eur. J. Inorg. Chem. 2012, 1359–1368
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1359

W. Uhl, D. Heller, J. Kösters, E.-U. Würthwein, N. Ghavtadze
FULL PAPER
lar interaction between the α-carbon atoms of the alkynyl
groups and the aluminium atoms. These interactions may
help to stabilize the cis addition products and to prevent
rearrangement. The p-tolyl derivatives 1 and 2 [Equa-
tion (1)] have not been reported previously. They were iso-
lated in 41 and 78% yield, respectively, by the reaction of
the corresponding diethynylsilane with one equivalent of
bis(tert-butyl)- or dineopentylaluminium hydride. Their 13
C
NMR spectra show the resonances characteristic of ethynyl
(δ = 92.5 and 117.4 ppm, on average) and ethenyl carbon
atoms (δ = 146.5 and 157.9 ppm). The cis arrangement of
Al and H atoms at the C=C double bond is evident from
crystal structure determinations (Figure 1) and from the
3
characteristic JH–C=C–Si coupling constant of 25.8 Hz
Figure 1. Molecular structure and numbering scheme of 1; the ther-
mal ellipsoids are drawn at the 40% probability level; hydrogen
atoms with the exception of the vinylic hydrogen atom are omitted.
Selected bond lengths [pm] and angles [°]: Al1–C11 199.9(2), Al1–
C21 248.2(2), C11–C12 134.8(2), C21–C22 121.2(2), Al1–C11–Si1
102.12(7), C11–Si1–C21 96.53(7), Si1–C21–Al1 85.44(6), C11–Al1–
C21 75.69(6). Data of the analogous compound 2: Al1–C11
199.3(1), Al1–C21 255.5(1), C11–C12 135.0(2), C21–C22 120.9(2),
Al1–C11–Si1 100.76(6), C11–Si1–C21 98.20(6), Si1–C21–Al1
82.53(5), C11–Al1–C21 75.02(5).
(trans positions of H and Si; see below for further dis-
cussion). The C=C and CϵC bond lengths (134.9 and
121.1 pm, on average) are in accord with standard values.
The relatively short intramolecular Al1–C21 distances
[248.2(2) (1) and 255.5(1) pm (2)], the positions of the Al
atoms up to 33.3 pm above the planes of the adjacent atoms
(C5, C6, C11) and the small torsion angles Al1–C11–Si1–
C21 of 4.37(8)° and –17.58(7)°, respectively, verify the inter-
action of the Al atoms with the α-carbon atoms of the triple
bonds (C21) bearing a relatively high negative charge.[9]
Similar structures have been observed for corresponding reaction times of at least 8 d at room temperature [Equa-
germanium compounds[10] or were derived from NMR tion (1)]. Faster reactions may be prevented by steric shield-
spectroscopic data for some products of hydroboration re- ing and electrostatic repulsion. The reaction rates could not
actions.[11]
be enhanced by heating of the mixtures under reflux be-
cause decomposition took place with the formation of un-
known components. Dimethylsilane and silacyclobutane de-
rivatives did not yield the products of twofold hydroalumi-
nation at all. Instead, the corresponding dimeric dialkylalu-
minium ethynides, (R2Al–CϵC–C6H5)2,[12] were formed
and identified by their characteristic NMR spectroscopic
data. Further products could not be isolated or identified.
Treatment of compound 2 with an excess of dineopentylalu-
minium hydride did not result in the formation of the corre-
sponding dialkenyl derivative, and 2 remained unchanged
even after a prolonged reaction time. Sterically less-shielded
hydrides such as dimethyl- or diethylaluminium hydride
gave unclear reaction courses. The corresponding reactions
of dialkynylgermanium compounds proved to be even less
selective and only a single dialkenyl species could be iso-
lated and applied in secondary reactions.[13]
The central silicon atoms of the dialkenyl compounds 3–
5 (Figure 2) have a slightly distorted tetrahedral coordina-
tion sphere and are bound to two phenyl and two alkenyl
groups. As expected by charge separation in the starting
Dual hydroalumination of dialkynylsilanes to yield the bisalkynes, the aluminium atoms selectively attacked the α-
doubly reduced dialuminium species has not been achieved carbon atoms of the ethynyl groups. The metal atoms have
previously. The silane starting compounds (H5C6)2Si(CϵC– an almost ideally planar surrounding with a maximum devi-
RЈ)2 (RЈ = C6H5, 4-MeC6H4) reacted with two equivalents ation of the aluminium atom from the plane of the three
of dineopentyl- or bis(tert-butyl)aluminium hydride to give, adjacent carbon atoms of only 14.5 pm in compound 5. The
in the first step, the mixed alkenyl–alkynylsilanes analogous C=C double bond lengths are in a narrow range and deviate
to 1 or 2. In contrast to the relatively fast hydroalumination only slightly from the average value of 134.8 pm. Minimiz-
of the first triple bond (3–16 h), the addition of the second ation of steric repulsion seems to determine the molecular
equivalent of dialkylaluminium hydride to yield the fully conformation in the solid state, and the bulky dialkylalu-
reduced dialkenyl derivatives 3–5 is very slow and requires minium groups adopt the largest possible distance to one
1360
www.eurjic.org
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 1359–1368

Hydroalumination of Bis(alkynyl)silanes
another. Interestingly, cis/trans isomerization occurs, and their acceptor properties in a simple experiment prior to the
the H and Al atoms are on different sides of the C=C beginning of systematic investigations. We treated com-
double bonds. Hence, the isolation of persistent cis isomers pound 4 with equimolar quantities of tetra(n-butyl)ammo-
with the monoaddition products (e.g. 1) is not caused by nium chloride in toluene. A suspension was obtained,
steric shielding. Instead isomerization is prevented in these which, after evaporation of the solvent and treatment of the
cases by the intramolecular Al–C interaction and coordina- residue with n-hexane, gave a colourless amorphous solid.
tive saturation of the Al atoms, as described above and It was dissolved in a small volume of 1,2-difluorobenzene.
schematically shown in Equation (1).
Colourless crystals of adduct 6 were isolated upon cooling
of the solution to –15 °C [Equation (2)]. The crystal struc-
ture determination verified the complexation of the chloride
ion by both aluminium atoms in a chelating manner(Fig-
ure 3), which is accompanied by a dramatic change in the
Figure 2. Molecular structure and numbering scheme of 3; the ther-
mal ellipsoids are drawn at the 40% probability level; hydrogen
atoms with the exception of the vinylic hydrogen atoms are omitted.
Selected bond lengths [pm] and angles [°]: Al1–C11 197.6(2), C11–
C12 134.4(2), Al2–C21 198.6(2), C21–C22 134.3(3), C11–Si1–C21
116.10(8), Si1–C11–C12 119.4(1), Si1–C21–C22 117.7(1), Si1–C11–
Al1 118.11(9), Si1–C21–Al2 114.61(9), Al1–C11–C12 122.5(1),
Al2–C21–C22 127.2(1). Data of compound 4: Al1–C11 197.8(2),
C11–C12 134.7(2), C11–Si1–C11Ј 111.7(1), Si1–C11–C12 118.9(1),
Si1–C11–Al1 127.09(8), Al1–C11–C12 113.6(1); C11Ј generated
by –x + 1.5, –y + 0.5, z. Data for compound 5: Al1–C11 198.3(3),
C11–C12 135.4(3), C11–Si1–C11Ј 110.4(2), Si1–C11–C12 117.8(2),
Si1–C11–Al1 129.4(1), Al1–C11–C12 112.3(2); C11Ј generated by
–x + 1.5, –y + 0.5, z.
NMR spectroscopic data are in accordance with the mo-
lecular structures. The resonances for the ethenyl carbon
atoms are in a narrow range of the 13C NMR spectrum
between δ = 157.7 and 161.8 ppm; signals for ethynyl car-
bon atoms (δ = 90–120 ppm of 1 and 2 and other mixed
alkenyl–alkynyl derivatives[7,10,13]) are missing, which veri-
3
fies complete hydroalumination. The JSi–H coupling con-
stants across the C=C double bonds (11.4 to 12.4 Hz) are
much smaller than those in the monoaddition products (see
1 and 2 above). They clearly indicate the cis arrangement
of H and Si atoms,[8,14] and hence cis/trans isomerization.
Figure 3. Molecular structure and numbering scheme of 6; the ther-
mal ellipsoids are drawn at the 40% probability level; hydrogen
atoms with the exception of the vinylic hydrogen atoms and methyl
groups are omitted. Selected bond lengths [pm] and angles [°]: Al1–
C11 201.5(3), C11–C12 135.3(5), Al2–C21 202.9(3), C21–C22
136.2(4), Al1–Cl1 234.1(1), Al2–Cl1 232.7(1), Al1–Cl1–Al2
134.60(4), C11–Si1–C21 124.4(1), Si1–C11–C12 113.5(2), Si1–C21–
C22 110.4(2), Si1–C11–Al1 127.7(2), Si1–C21–Al2 126.4(2), Al1–
Dialuminium Compound 4 as a Chelating Lewis Acid
The molecular conformation of the dialkenylsilicon com-
pounds 3–5 in which the coordinatively unsaturated alu-
minium atoms point in opposite directions of the molecules
seems to contradict their potential application as chelating
Lewis acids. Therefore, it was particularly important to test C11–C12 118.7(2), Al2–C21–C22 123.1(2).
Eur. J. Inorg. Chem. 2012, 1359–1368
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1361

W. Uhl, D. Heller, J. Kösters, E.-U. Würthwein, N. Ghavtadze
FULL PAPER
molecular conformation of the bisacceptor and a reorienta- bon atom of the alkyne (see below for details of the reaction
tion of the alkenylaluminium fragments by rotation about mechanism). The central SiC3 heterocycle contains an en-
the Si–C bonds. Despite the bulkiness of the bis(tert-butyl)- docyclic C=C double bond, which with a length of
aluminium groups, the Al atoms coordinate the halide ion 138.8(2) pm is relatively long. The third carbon atom of the
in a chelating manner to give a six-membered ClAl2C2Si ring is part of an exocyclic double bond with a normal
heterocycle. The C=C double bonds that had an endo-type length of 134.1(3) pm.[16] The relatively long Si–C distances
orientation in the starting compound 4 are now in exo-posi- (186.4 pm on average) cause a distortion of the ring with
tions. The Al–Cl distances (233.4 pm on average) are in the an acute C–Si–C angle of 74.57(8)°. The remaining angles
normal range observed for bridging Al–Cl–Al groups in or- of the ring are 89.2(1) and 93.2(1)° (Si–C–C) and 102.9(1)°
ganoaluminium compounds (≈225–240 pm).[13,15] In ac- (C–C–C). Because of the sp2-hybridization of all carbon
cordance with the higher coordination numbers of the alu- atoms, these relatively small angles may indicate consider-
minium atoms, the Al–C bonds of 6 show the usual length- able strain in the heterocycle. The aluminium atom has a
ening relative to those in 4 (203.0 pm vs. 198.7 pm, on terminal position and is coordinatively saturated by coordi-
average). The C=C double bonds of 6 are only slightly nation of a THF molecule. The Al–C distance to the ring
longer [135.8 pm on average, vs. 134.7(2) pm for 4]. A rela- carbon atom C3 [202.1(2) pm] is in the expected range for
tively obtuse angle was observed at the chlorine atom [Al1– tetracoordinate aluminium atoms.
Cl1–Al2 134.60(4)°], while the most acute endocyclic angles
of the central heterocycle occur at the aluminium atoms
(Cl1–Al–C 98.9°). The configuration of the alkenyl groups
remains unchanged with a trans arrangement of the Al and
H atoms. Compound 6 crystallizes isotypically to the corre-
sponding germanium compound.[13] Interestingly, the
NMR spectroscopic data of both compounds 4 and 6 are
almost identical and obviously do not depend on adduct
formation. The only significant alteration involves the
chemical shift of the central silicon atom, which in the 29Si
NMR spectra changes from δ = –19.0(4) ppm to δ =
–2.0(6) ppm.
Rearrangement and 1,1-Organoalumination Upon Heating
of an Alkenyl–Alkynylsilane
The close contact between the coordinatively unsaturated
aluminium atoms and the α-carbon atoms of the ethynyl
groups in the mixed alkenyl–alkynylsilanes analogous to 1
and 2 should facilitate interesting secondary reactions.
However, heating of the solutions in toluene or of the neat
materials led to decomposition with the formation of in-
separable mixtures of several unknown components in most
cases. An exception was the thermal treatment of the com-
pound (H5C6)2Si(CϵC–C6H5)[C(AlR2)=C(H)–C6H5] (7, R
= CMe3), the synthesis of which has been published by our
group only recently.[7] A relatively clear reaction course was
observed in refluxing toluene with the complete consump-
tion of 7 after 48 h and the formation of an oily product,
which shows an intensive resonance of tert-butyl groups in
1
the H NMR spectrum in addition to signals of unknown
impurities. Despite enormous efforts, we were not able to
purify this product by crystallization from different non-
coordinating solvents (n-pentane to pentafluorobenzene).
Addition of THF gave an adduct (8), which could be crys-
Figure 4. Molecular structure and numbering scheme of 8; the ther-
mal ellipsoids are drawn at the 40% probability level; hydrogen
tallized from diisopropyl ether and was isolated in 73%
yield [Equation (3)]. The crystal structure reveals the forma-
tion of an unusual heterocyclic silacyclobutene derivative
(Figure 4) by insertion of the negatively charged α-carbon
atom of the ethynyl group into an Al–C bond (1,1-carbalu-
atoms with the exception of the vinylic hydrogen atom and methyl
groups are omitted; only the oxygen atom of the THF ligand at-
tached to aluminium is shown. Selected bond lengths [pm] and
angles [°]: Si1–C1 186.7(2), Si1–C2 186.0(2), Al1–C3 202.1(2), C1–
C11 134.1(3), C1–C3 150.1(2), C2–C3 138.5(2), C1–Si1–C2
74.57(8), Si1–C1–C3 89.2(1), Si1–C2–C3 93.2(1), C1–C3–C2
mination) and formation of a new Si–C bond to the β-car- 102.9(1), Si1–C1–C11 143.1(1), C3–C1–C11 127.5(2).
1362 Eur. J. Inorg. Chem. 2012, 1359–1368
www.eurjic.org
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Hydroalumination of Bis(alkynyl)silanes
The most interesting feature of the NMR spectroscopic arrangement. The Si–C bond to the negatively charged car-
data of 8 is the unusual chemical shift for the carbon atoms bon atom of the ethynyl group is considerably weakened,
of the endocyclic C=C double bond [δ = 194.5 ppm (C=C– and its interaction to the aluminium atom becomes stronger
Al) and 174.1 ppm (C=C–Si)]. In contrast, the resonances (Al–C 264 pm in 7 to 194 pm in TS; Si–C 188 to 249 pm).
of the exocyclic C=C bond are in the normal range (δ = At the same time, a new Si–C bond is formed to the original
130.7 and 154.5 ppm). The signals of the vinylic hydrogen β-carbon atom of the alkyne (Si–C 191 pm). The transan-
atom [δ(1H) = 7.11 ppm ] and of the silicon atom [δ(29Si) = nular contact between the sp2 carbon atoms of the alkenyl
–1.4 ppm] are considerably shifted compared to the corre- groups (indicated by a dashed line) is relatively long at this
sponding resonances of the starting compound 7 (δ = 8.35 stage of the reaction (224 pm). It becomes a normal C–C
and –34.5 ppm[7]). Only compound 1 shows a similar re- bond (C–C 149 pm) in the next step, while the Al–C bond
arrangement upon heating in toluene. However, it was not to the original α-carbon atom of the ethynyl group is almost
completely consumed even after prolonged reaction times unchanged upon formation of 9 (Al–C 200 pm). The C–C
of 3 d, and several unknown by-products were detected in bond length of the original ethynyl group steadily increases
the NMR spectra. A solid material was isolated in 30% from 122 over 131 to 138 pm [further important calculated
yield by crystallization from n-pentane. Its main component parameters of 9: Si–C 188 and 190 pm; C=C (exo) 135 pm].
had NMR spectroscopic data similar to those of 8, but it C–C bond formation yields the four-membered SiC3 hetero-
had some impurities of unknown composition. Therefore, cycle as the characteristic structural motif of the rearranged
we abstain from a detailed discussion.
product. Overall this mechanism corresponds to the inser-
In order to elucidate the mechanism of the unusual re- tion of the negatively charged terminal carbon atom of the
arrangement of 7 to give 8, high level quantum chemical alkynyl group in 7 (NBO charge –0.52; Al +1.99) into the
calculations at the SCS-MP2/6-311G(d,p)//B3LYP/6- Al–C(vinyl) bond and formation of a new Si–C bond. The
311G(d,p) level were performed. The structural parameters activation barrier was calculated to be 33.5 kcal/mol, and
of the starting material 7 (in comparison to the X-ray the reaction is moderately exothermic (–3.7 kcal/mol),
data[7]) and of the product 9 as a solvent-free model com- which is in accordance with the experimental conditions for
pound of 8 are well reproduced by the theoretical method. thermal rearrangement. A similar activation barrier was
According to the theoretical results, the reaction proceeds calculated for the rearrangement of a germanium-centred
through a concerted mechanism via the transition structure alkenyl–alkynyl compound.[9] The calculations also give
TS, as shown in Scheme 1 and Figure 5. The highly ordered clear evidence that a mechanism involving the dissociation
structure of the transition state involves essentially five of the starting compound 7 into diphenyl(2-phenylvinyl-
atoms: the silicon and aluminium atoms together with both idene)silane and well-known bis(tert-butyl)(phenylethynyl)-
carbon atoms of the alkynyl group as well as the α-carbon aluminium[12] followed by 2+2-cycloaddition seems to be
atom of the alkenyl group in a planar tricyclic geometry. rather unlikely because the dissociation products are
The relatively weak intramolecular interaction of the alu- 62.8 kcal/mol higher in energy than the substrate 7.
minium atom with the α-carbon atom of the alkynyl moiety
is indeed the key structural element to initiate the re-
Figure 5. Calculated molecular structures of 7, 9 (model for 8 with-
out THF) and the relavant transition state TS with their relative
energies [kcal/mol] {SCS-MP2/6-311G(d,p)//B3LYP/6-311G(d,p)
incl. ZPE}.
This is only the second time that 1,1-carbalumination has
been observed, the first case involved the rearrangement of
an alkenyl–alkynylgermanium compound.[9] In principle,
this method seems to be a facile procedure for the simple
generation of sila- or germacyclobutene derivatives; how-
ever, up to now, this route could be applied successfully in
only two cases. We hope that optimization of the reaction
Scheme 1.
conditions in future investigations may allow a broader ap-
Eur. J. Inorg. Chem. 2012, 1359–1368
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1363

W. Uhl, D. Heller, J. Kösters, E.-U. Würthwein, N. Ghavtadze
FULL PAPER
colourless crystals of 1. Yield: 0.474 g (41%; after thorough evacua-
plication. In contrast, 1,1-carbaboration is quite common
and has been used for the synthesis of several unsaturated
heterocyclic compounds.[11,17] Silacyclobutenes similar to
compound 8 have also been obtained by other routes.[18]
They found some interest in research because they show
photoluminescence.[19]
tion). M.p. (argon; sealed capillary) 135 °C (dec.). 1H NMR
(400 MHz, C6D6): δ = 1.36 (s, 18 H, CMe3), 1.83 (s, 3 H, CH3
3
ethynyl-pTol), 1.94 (s, 3 H,CH3 ethenyl-pTol), 6.66 (d, JH,H
=
3
7.9 Hz, 2 H, meta-H ethynyl-pTol), 6.75 (d, JH,H = 8.0 Hz, 2 H,
meta-H ethenyl-pTol), 7.15 (m, 8 H, meta-H and para-H Ph2Si),
3
3
7.41 (d, JH,H = 7.9 Hz, 2 H, ortho-H ethynyl-pTol), 7.43 (d, JH,H
= 8.0 Hz, 2 H, ortho-H ethenyl-pTol), 8.00 (m, 4 H, ortho-H Ph2Si),
8.38 (s, JH–Si = 25.8 Hz, 1 H, C=CH) ppm. 13C NMR (100 MHz,
3
C6D6): δ = 19.6 (CMe3), 21.0 (CH3 ethenyl-pTol), 21.4 (CH3 eth-
ynyl-pTol), 31.1 (CMe3), 91.4 (Si–CϵC), 117.0 (ipso-C ethynyl-
pTol), 117.9 (Si–CϵC), 128:5 (meta-C Ph2Si), 128.8 (ortho-C eth-
enyl-pTol), 129.3 (meta-C ethenyl-pTol), 129.6 (meta-C ethynyl-
pTol), 130.4 (para-C Ph2Si), 133.9 (ortho-C ethynyl-pTol), 134.4
(ipso-C Ph2Si), 136.0 (ortho-C Ph2Si), 138.2 (para-C ethenyl-pTol),
138.9 (ipso-C ethenyl-pTol), 142.0 (para-C ethynyl-pTol), 145.1
(C=CH-pTol), 157.4 (C=CH-pTol) ppm. 29Si NMR (79.5 MHz,
Experimental Section
General: All procedures were carried out under an atmosphere of
purified argon in dried solvents (n-hexane and n-pentane with Li-
AlH4; pentafluoro- and 1,2-difluorobenzene with molecular sieves,
diethyl ether, THF and diisopropyl ether with Na/benzophenone).
(Me3C)2Al–H,[20] (Me3CCH2)2Al–H,[21] (H5C6)2Si(CϵC–C6H5)2
[22]
and compound 7[7] were obtained according to literature pro-
cedures. Commercially available tetrabutylammonium chloride was
employed as purchased. The assignment of the NMR spectra is
based on HMBC, HSQC, ROESY and DEPT135 data. The Si–
H coupling constants (3JSi–H) across the C=C double bonds were
determined from the 29Si satellite peaks of the vinylic hydrogen
C D ): δ = –37.1 ppm. IR (CsI, paraffin): ν = 2158 (s), 2126 [vs,
˜
6
6
ν(CϵC)], 2056 (vw), 1977 (w), 1962 (w), 1911 (m), 1890 (w), 1822
(w), 1795 (vw), 1773 (vw), 1707 (vw), 1655 (w), 1645 (w), 1605 (s),
1584 (s), 1552 (s), 1506 (s), 1483 [s, ν(C=C), phenyl], 1460 (vs),
1379 [vs, paraffin], 1355 (m), 1342 (w), 1304 (m), 1273 (w), 1263
[m, δ(CH3)], 1219 (w), 1190 (m), 1179 (m), 1157 (vw), 1107 (vs),
1040 (m), 1020 (w), 997 (m), 970 (w), 951 (w), 930 (w), 897 (s), 854
(s), 840 (m), 814 (vs), 789 [s, ν(CC), δ(CH)], 740 [s, δ(C=C)], 698
[vs, phenyl], 653 (s), 627 (s), 588 (s), 561 (m), 536 (m), 520 (w), 491
(m), 471 (s), 446 [m, ν(SiC), ν(AlC), δ(CC)] cm–1. MS (EI, 20 eV,
373 K): m/z (%) = 497 (13) [M+ – CMe3], 413 (83) [M+ – Al-
(CMe3)2]. C38H43AlSi (554.8): calcd. C 82.3, H 7.8; found C 81.8,
H 7.8.
1
atoms in the H NMR spectra.
Synthesis of (H5C6)2Si(CϵC-4-MeC6H4)2: A solution of p-tolyle-
thyne (8.0 mL, 7.33 g, 63.2 mmol) in diethyl ether (100 mL) was
treated with a solution of n-butyllithium in n-hexane (1.6 m,
39.5 mL, 63.2 mmol) at –78 °C. The mixture was stirred for 2 h at
this temperature. Diphenyldichlorosilane (6.0 mL, 7.22 g,
28.5 mmol) was added. After 2 h, the suspension was warmed to
room temperature and was further stirred for 16 h. Aqueous HCl
(10%; 100 mL) was added to completely dissolve the LiCl precipi-
tate. The organic phase was separated, and the aqueous phase was
extracted two times with diethyl ether (25 mL). The combined or-
ganic phases were dried with MgSO4 and filtered. All volatiles of
the filtrate were removed in vacuo. The residue was dissolved in n-
pentane. Colourless crystals of the dialkyne were obtained upon
cooling to –70 °C. Yield: 8.64 g (74%). M.p. (argon; sealed capil-
lary) 79 °C. 1H NMR (400 MHz, C6D6): δ = 1.91 (s, 6 H, CH3),
Synthesis of 2: A solution of dineopentylaluminium hydride
(0.151 g, 0.89 mmol) in n-hexane (25 mL) was treated with a solu-
tion of diphenylbis(p-tolylethynyl)silane (0.366 g, 0.89 mmol) in n-
hexane (25 mL). The solution was stirred at room temperature for
4 h. All volatiles were removed in vacuo. The residue was dissolved
in pentafluorobenzene and cooled to +2 °C to obtain colourless
crystals of 2. Yield: 0.403 g (78%). M.p. (argon, sealed capillary)
1
141 °C (dec.). H NMR (400 MHz, C6D6): δ = 0.87 (s, 4 H, CH2),
3
6.71 (d, 4 H, JH,H = 8.0 Hz, meta-H pTol), 7.21 (m, 2 H, para-H
1.31 (s, 18 H, CMe3), 1.84 (s, 3 H, CH3 ethynyl-pTol), 1.93 (s, 3 H,
Ph), 7.23 (m, 4 H, meta-H Ph), 7.35 (d, 4 H, 3JH,H = 8.0 Hz, ortho-
H pTol), 8.15 (m, 4 H, ortho-H Ph) ppm. 13C NMR (100 MHz,
C6D6): δ = 21.3 (Me), 88.0 (Si–CϵC), 109.8 (Si–CϵC), 120.0 (ipso-
C ethynyl-Ph), 128.5 (meta-C SiPh2), 129.3 (meta-C ethynyl-Ph),
130.5 (para-C Ph2Si), 132.6 (ortho-C ethynyl-Ph), 133.9 (ipso-C
Ph2Si), 135.5 (ortho-C Ph2Si), 139.5 (para-C ethynyl-Ph) ppm. 29Si
3
CH3 ethenyl-pTol), 6.67 (d, JH–H = 7.9 Hz, 2 H, meta-H ethynyl-
pTol), 6.74 (d, 3JH–H = 7.9 Hz, 2 H, meta-H ethenyl-pTol), 7.14 (m,
3
2 H, para-H Ph2Si), 7.19 (m, 4 H, meta-H Ph2Si), 7.37 (d, JH–H
=
3
7.9 Hz, 2 H, ortho-H ethynyl-pTol), 7.42 (d, JH–H = 7.9 Hz, 2 H,
ortho-H alkenyl-pTol), 8.02 (pseudo-d, 4 H, ortho-H Ph2Si), 8.34 (s,
3JH–Si = 25.7 Hz, 1 H, C=CH) ppm. 13C NMR (100 MHz, C6D6): δ
= 21.0 (CH3 ethenyl-pTol), 21.3 (CH3 ethynyl-pTol), 31.9 (CMe3),
33.7 (CH2), 35.3 (CMe3), 93.6 (Si–CϵC), 116.9 (Si–CϵC), 117.7
(ipso-C ethynyl-pTol), 128.5 (meta-C Ph2Si), 128.6 (ortho-C ethenyl-
pTol), 129.3 (meta-C ethenyl-pTol), 129.5 (meta-C ethynyl-pTol),
130.4 (para-C Ph2Si), 133.2 (ortho-C ethynyl-pTol), 134.4 (ipso-C
Ph2Si), 136.1 (ortho-C Ph2Si), 138.2 (para-C ethenyl-pTol), 139.2
(ipso-C ethenyl-pTol), 141.3 (para-C ethynyl-pTol), 147.9 (Si–C=C–
H), 158.3 (Si–C=C–H) ppm. 29Si NMR (79.5 MHz, C6D6): δ =
NMR (79.5 MHz, C D ): δ = –47.7 ppm. IR (CsI, paraffin): ν =
˜
6
6
2158 [s, ν(CϵC)], 1960 (vw), 1908 (w), 1821 (vw), 1653 (w), 1606
(w), 1580 (w), 1545 (w), 1528 [vw, phenyl], 1466 (vs), 1377 [vs,
paraffin], 1321 (m), 1265 (w), 1248 [w, δ(CH3)], 1218 (w), 1188 (w),
1173 (w), 1153 (w), 1113 (m), 1040 (vw), 1018 (w), 999 (w), 966
(w), 947 (w), 920 (w), 889 (w), 843 (s), 814 (s), 768 (m), 734 [vs,
ν(CC), δ(CH)], 721[vs, paraffin], 694 [w, δ(phenyl)], 637 (vw), 619
(w), 588 (s), 565 (s), 536 (s), 491 (m), 472 (m), 426 [m, ν(SiC),
ν(AlC), δ(CC)] cm–1. MS (EI, 20 eV, 393 K): m/z (%) = 412 (100)
[M+], 397 (9) [M+ – CH3], 335 (17) [M+ – Ph]. C30H24Si (412.6):
calcd. C 87.3, H 5.9; found C 87.6, H 6.0.
–35.4 ppm. IR (CsI, paraffin): ν = 2158 (s), 2126 [m, ν(CϵC)], 2052
˜
(w), 1983 (w), 1964 (w), 1952 (w), 1902 (w), 1827 (w), 1813 (w),
1775 (vw), 1701 (vw), 1649 (w), 1591 (m), 1566 (m), 1555 (w), 1506
[s, ν(C=C), phenyl], 1454 (vs), 1377 [vs, paraffin], 1304 (s), 1267 [s,
δ(CH3)], 1220 (m), 1190 (w), 1177 (w), 1153 (w), 1111 (s), 1038
(m), 1016 (s), 997 (m), 962 (w), 943 (m), 921 (vw), 843 (w), 849 (s),
816 (s), 802 (vw), 775 (w), 752 [w, ν(CC), δ(CH)], 737 [s, δ(C=C)],
721 [s, paraffin], 698 [s, phenyl], 660 (w), 615 (m), 597 (w), 565 (m),
536 (m), 519 (m), 484 (m), 465 (m), 440 [m, ν(SiC), ν(AlC), δ(CC)]
Synthesis of 1: A solution of bis(tert-butyl)aluminium hydride
(0.296 g, 2.08 mmol) in n-hexane (25 mL) was treated with a solu-
tion of diphenylbis(p-tolylethynyl)silane (0.859 g, 2.08 mmol) in n-
hexane (25 mL). The mixture was stirred for 16 h at room tempera-
ture. The colour changed to yellow. All volatiles were removed in
vacuo, and the remaining yellowish solid was recrystallized from
1,2-difluorobenzene or pentafluorobenzene (20/–30 °C) to yield
cm–1. MS (EI, 20 eV, 413 K): m/z (%) = 511 (100) [M+
–
1364
www.eurjic.org
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 1359–1368

Hydroalumination of Bis(alkynyl)silanes
CH2CMe3], 413 (46) [M+ – AlNp2], 336 (22) [M+ – AlNp2 – Ph]. vacuo. The remaining solid was dissolved in pentafluorobenzene.
C40H47AlSi (582.9): calcd. C 82.4, H 8.1; found C 82.2, H 7.8.
Cooling of the solution to +2 °C afforded colourless crystals of
compound 5. Yield: 0.362 g (63%). M.p. (argon; sealed capillary)
185 °C (dec.). 1H NMR (400 MHz, C6D6): δ = 0.94 (s, 36 H,
CMe3), 2.00 (s, 6 H, CH3 pTol), 7.02 (d, 3JH–H = 8.2 Hz, 4 H, meta-
Synthesis of 3: A solution of dineopentylaluminium hydride
(0.207 g, 1.22 mmol) in n-hexane (10 mL) was treated with a solu-
tion of diphenylbis(phenylethynyl)silane (0.234 g, 0.609 mmol) in
n-hexane (25 mL). The mixture was stirred at room temperature for
8 d. The colour changed to yellow. All volatiles were removed in
vacuo. The remaining viscous liquid was dissolved in a few milli-
litres of pentafluorobenzene. Cooling of the solution to +2 °C af-
forded colourless crystals of 3. Yield: 0.157 g (36%). M.p. (argon;
sealed capillary) 132 °C (dec.). 1H NMR (400 MHz, C6D6): δ =
0.52 (s, 8 H, CH2), 0.99 (s, 36 H, CMe3), 7.02 (m, 2 H, para-H
alkene-Ph), 7.15 (m, 4 H, meta-H alkene-Ph), 7.22 (m, 2 H, para-
H Ph2Si), 7.31 (m, 4 H, meta-H Ph2Si), 7.39 (m, 4 H, ortho-H
alkene-Ph), 7.98 (m, 4 H, ortho-H Ph2Si), 8.32 (s, 3JH–Si = 12.4 Hz,
2 H, C=CHPh) ppm. 13C NMR (100 MHz, C6D6): δ = 31.3
(CMe3), 34.6 (CMe3), 34.9 (CH2), 125.7 (ortho-C alkene-Ph), 128.7
(para-C alkene-Ph), 129.1 (meta-C Ph2Si), 130.1 (para-C Ph2Si),
130.2 (meta-C alkene-Ph), 136.1 (ortho-C Ph2Si), 139.0 (ipso-C
Ph2Si), 145.8 (ipso-C alkene-Ph), 157.7 (C=CHPh), 161.7
(C=CHPh) ppm. 29Si NMR (79.5 MHz, C6D6): δ = –19.1 ppm. IR
3
H pTol), 7.21 (m, 2 H, para-H Ph2Si), 7.23 (dd, JH–H = 8.2,
4JH–H = 1.4 Hz, 4 H, ortho-H pTol), 7.30 (m, 4 H, meta-H Ph2Si),
7.95 (m, 4 H, ortho-H Ph2Si), 8.49 (s, 3JH–Si = 11.8 Hz, 2 H, CHPh)
ppm. 13C NMR (100 MHz, C6D6): δ = 19.4 (CMe3), 21.0 (CH3
pTol), 30.5 (CMe3), 123.7 (ortho-C pTol), 129.0 (meta-C Ph2Si),
129.9 (para-C Ph2Si), 132.1 (meta-C pTol), 136.0 (ortho-C Ph2Si),
138.9 (para-C pTol), 139.4 (ipso-C Ph2Si), 145.3 (ipso-C pTol), 159.1
(C=CHPh), 160.2 (C=CHPh) ppm. 29Si NMR (79.5 MHz, C6D6):
δ = –18.8 ppm. IR (CsI, paraffin): ν = 1904 (w), 1829 (vw), 1798
˜
(vw), 1777 (vw), 1699 (vw), 1649 (vw), 1605 (m), 1564 [vw, ν(C=C),
phenyl], 1466 (vs), 1377 [vs, paraffin], 1312 (m), 1265 [m, δ(CH3)],
1219 (vw), 1204 (vw), 1177 (m), 1153 (vw), 1109 (vs), 1063 (vw),
1040 (m), 1028 (m), 1001 (s), 962 (vw), 939 (m), 908 (m), 885 (s),
841 (m), 804 [m, ν(CC), δ(CH)], 735 [s, δ(C=C)], 721 [s, paraffin],
702 (w), 660 (vw), 642 (m), 623 [w, phenyl], 596 (s), 542 (m), 521
(m), 502 (w), 480 (vw), 463 (m), 440 [m, ν(SiC), ν(AlC), δ(CC)]
cm–1. MS (EI, 20 eV, 310 K): m/z (%) = 640 (100) [M+ – butene],
498 (60) [M+ – AltBu3]. C46H62Al2Si (697.1): calcd. C 79.3, H 9.0;
found C 78.5, H 9.0.
(CsI, paraffin): ν = 1649 (w), 1599 (m), 1574 (m), 1532 [m, ν(C=C),
˜
phenyl], 1462 (vs), 1377 [vs, paraffin], 1308 (w), 1250 [vw, δ(CH3)],
1155 (m), 1109 (w), 1072 (w), 1027 (w), 1013 (w), 991 (m), 931 (m),
920 (m), 833 (m), 797 [w, ν(CC), δ(CH)], 732 [m, δ(C=C)], 723 [m,
paraffin], 698 [m, phenyl], 628 (w), 594 (w), 551 (w), 474 [w, ν(SiC),
ν(AlC), δ(CC)] cm–1. MS (EI, 20 eV, 333 K): m/z (%) = 441 (100)
[M+ – 4 CH2CMe3 + H], 386 (2) [M+ – 2 Al(CH2CMe3)2].
C48H66Al2Si (725.1): calcd. C 79.5, H 9.2; found C 79.2, H 8.9.
Synthesis of 6: The dialuminium compound
4
(0.342 g.
0.511 mmol) was dissolved in toluene (25 mL) and added to a sus-
pension of tetra(n-butyl)ammonium chloride (0.142 g, 0.512 mmol)
in toluene (25 mL). The mixture was stirred at room temperature
for 16 h. All volatiles were removed in vacuo. The oily residue was
washed with a few millilitres of n-hexane to obtain a colourless
solid material. It was recrystallized from 1,2-difluorobenzene
(20/–15 °C) to yield colourless crystals of 6. Yield: 0.128 g (26%).
M.p. (argon; sealed capillary) 84 °C (dec.). 1H NMR (400 MHz,
[D8]THF): δ = 0.71 (s, 36 H, CMe3), 0.98 [t, 3JH–H = 7.3 Hz, 12 H,
N(CH2CH2CH2CH3)4], 1.38 [m, 8 H, N(CH2CH2CH2CH3)4], 1.64
[m, 8 H, N(CH2CH2CH2CH3)4], 3.20 [m, 8 H, N(CH2CH2-
CH2CH3)4], 7.03 (m, 2 H, para-H alkene-Ph), 7.10 (m, 2 H, para-
H Ph2Si), 7.13 (m, 4 H, meta-H alkene-Ph), 7.13 (m, 4 H, meta-H
Ph2Si), 7.26 (m, 4 H, ortho-H alkene-Ph), 7.62 (m, 4 H, ortho-H
Synthesis of 4: Bis(tert-butyl)aluminium hydride (0.286 g,
2.01 mmol) was dissolved in n-hexane (10 mL) and treated with a
solution of diphenylbis(phenylethynyl)silane (0.387 g, 1.01 mmol)
in n-hexane (10 mL). The mixture was stirred at room temperature
for 8 d. The colour changed to yellow. All volatiles were removed
in vacuo. The residue was dissolved in a few millilitres of pentafluo-
robenzene and cooled to +2 °C to yield colourless crystals of com-
pound 4. Yield: 0.316 g (47%). M.p. (argon; sealed capillary)
180 °C (dec.). 1H NMR (400 MHz, C6D6): δ = 0.90 (s, 36 H,
CMe3), 6.99 (m, 2 H, para-H alkene-Ph), 7.14 (m, 4 H, meta-H
alkene-Ph), 7.20 (m, 2 H, para-H Ph2Si), 7.26 (m, 4 H, ortho-H
alkene-Ph), 7.29 (m, 4 H, meta-H Ph2Si), 7.93 (m, 4 H, ortho-H
3
Ph2Si), 7.71 (s, JH–Si = 14.2 Hz, 2 H, CHPh) ppm. 13C NMR
(100 MHz, [D8]THF): δ = 14.0 [N(CH2CH2CH2CH3)4], 17.8
(CMe3), 20.6 [N(CH2CH2CH2CH3)4], 24.6 [N(CH2CH2CH2-
CH3)4], 32.9 (CMe3), 59.3 [N(CH2CH2CH2CH3)4], 126.6 (para-C
alkene-Ph), 127.1 (meta-C Ph2Si), 127.4 (para-C Ph2Si), 128.4 (or-
tho-C alkene-Ph), 128.5 (meta-C alkene-Ph), 138.1 (ortho-C Ph2Si),
144.4 (ipso-C Ph2Si), 148.1 (ipso-C alkene-Ph), 159.6 (C=CHPh),
160.9 (C=CHPh) ppm. 29Si NMR (79.5 MHz, [D8]THF): δ =
3
Ph2Si), 8.47 (s, JH–Si = 11.4 Hz, 2 H, C=CHPh) ppm. 13C NMR
(100 MHz, C6D6): δ = 19.5 (CM3), 30.4 (CMe3), 123.7 (ortho-C
alkene-Ph), 128.9 (para-C alkene-Ph), 129.1 (meta-C Ph2Si), 130.0
(para-C Ph2Si), 131.4 (meta-C alkene-Ph), 135.9 (ortho-C Ph2Si),
139.2 (ipso-C Ph2Si), 147.9 (ipso-C alkene-Ph), 159.2 (C=CHPh),
161.8 (C=CHPh) ppm. 29Si NMR (79.5 MHz, C6D6):
δ =
–2.0 ppm. IR (KBr, paraffin): ν = 1701 (vw), 1597 (w), 1580 (m),
˜
–19.0 ppm. IR (CsI, paraffin): ν = 1647 (w), 1597 (w), 1533 [w,
˜
1560 [vw, ν(C=C), phenyl], 1463 (vs), 1377 [vs, paraffin], 1304 (w),
1261 (vw), 1213 (vw), 1169 (w), 1153 (w), 1111 (m), 1099 (m), 1076
(w), 1026 (s), 1005 (s), 926 (m), 887 (m), 845 (vw), 812 (vw), 772
[m, ν(CC), δ(CH)], 721 [s, paraffin], 627 [m, phenyl], 592 (vw), 522
(s), 463 [m, ν(AlC), δ(CC)], 422 [m, ν(SiC), ν(AlC), ν(AlCl), δ(CC)]
cm–1. C60H94Al2ClNSi (946.9): calcd. C 76.1, H 10.0, N 1.5; found
C 75.4, H 10.0, N 1.5.
ν(C=C), phenyl], 1460 (vs), 1377 [vs, paraffin], 1308 (w), 1283 (w),
1269 [w, δ(CH3)], 1153 (vs), 1078 (vw), 1028 (vw), 999 (vw), 964
(vw) 935 (w), 887 (w), 843 (w), 812 (vw), 798 (vw), 771 [vw, ν(CC),
δ(CH)], 732 [m, δ(C=C)], 721 [m, paraffin], 700 (w), 623 [s, phenyl],
594 (w), 524 (vw), 474 [w, ν(SiC), ν(AlC), δ(CC)] cm–1. MS (EI,
20 eV, 310 K): m/z (%) = 611 (91) [M+ – CMe3], 469 (67) [M+
AltBu3 – H]. C44H58Al2Si (669.0): calcd. C 79.0, H 8.7; found C
–
Synthesis of 8: The mixed alkenyl–alkynylsilane (H5C6)2Si(CϵC–
C6H5)[C(AlR2)=C(H)–C6H5] (7, R = CMe3[7]) (0.826 g, 1.57 mmol)
was dissolved in toluene (25 mL). The solution was heated under
reflux for 48 h. All volatiles were removed in vacuo at room tem-
perature. The residue was dissolved in a few millilitres of THF, the
solvent was removed in vacuo, and the residue was dissolved in
diisopropyl ether. Crystals of compound 8 were obtained upon
slow concentration of the solution at room temperature under
78.5, H 8.8.
Synthesis of 5: Bis(tert-butyl)aluminium hydride (0.234 g,
1.65 mmol) was dissolved in n-hexane (10 mL) and treated with
diphenylbis(p-tolylethynyl)silane (0.339 g, 0.822 mmol) dissolved in
the same solvent (25 mL). The mixture was stirred at room tem-
perature for 8 d. Toluene (5 mL) was added after 1 d in order to
dissolve the colourless precipitate. All volatiles were removed in
Eur. J. Inorg. Chem. 2012, 1359–1368
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1365

W. Uhl, D. Heller, J. Kösters, E.-U. Würthwein, N. Ghavtadze
slightly reduced pressure. Yield: 0.683 g (73%). M.p. (argon; sealed fiber and immediately mounted in the cooled nitrogen stream of the
FULL PAPER
1
capillary) 196 °C (dec.). H NMR (400 MHz, [D8]THF): δ = 1.08
(s, 18 H, CMe3), 1.77 and 3.61 (each m, 4 H, THF), 6.98 (pseudo-
t, 1 H, para-H vinylic phenyl), 7.07 (pseudo-t, 2 H, meta-H vinylic
phenyl), 7.11 (m, 2 H, vinylic H and para-H phenyl attached to
heterocycle), 7.22 (pseudo-t, 2 H, meta-H phenyl attached to het-
erocycle), 7.28 (m, 2 H, ortho-H vinylic phenyl), 7.30 (m, 4 H, meta-
H Ph2Si), 7.32 (m, 2 H, para-H Ph2Si), 7.37 (m, 2 H, ortho-H
phenyl attached to heterocycle), 7.67 (m, 4 H, ortho-H Ph2Si) ppm.
diffractometer. The crystallographic data and details of the final R
values are provided in Tables 1 and 2.[25] All non-hydrogen atoms
were refined with anisotropic displacement parameters; hydrogen
atoms were calculated on ideal positions and allowed to ride on
the bonded atom with U = 1.2Ueq(C). The crystals of compound
1 enclose one molecule of pentafluorobenzene per formula unit.
The molecules of 4 and 5 reside on crystallographic twofold rota-
tion axes. One tert-butyl group of 4 (C31) showed a disorder, the
13C NMR (100 MHz, [D8]THF): δ = 16.6 (CMe3), 32.2 (CMe3), atoms were refined on split positions (0.66:0.34).
121.7 (ortho-C phenyl attached to heterocycle), 126.9 (para-C vin-
Quantum Chemical Calculations: All computations were performed
ylic phenyl), 127.2 (para-C phenyl attached to heterocycle), 127.3
(ortho-C vinylic phenyl), 128.9 (meta-C vinylic phenyl, meta-C
phenyl attached to heterocycle and meta-C Ph2Si), 130.5 (para-C
Ph2Si), 130.7 [H–C=C(Si)], 136.3 (ortho-C Ph2Si), 136.1 (ipso-C
Ph2Si), 141.0 (ipso-C vinylic phenyl), 143.6 (ipso-C phenyl attached
to heterocycle), 154.5 [H–C=C(Si) heterocycle], 174.1 (Al–C=C–Si
heterocycle), 194.5 (Al–C=C–Si heterocycle) ppm. 29Si NMR
by using the Gaussian 09 suite of programs.[26] The Becke three-
parameter exchange functional and the correlation functional of
Lee, Yang, and Parr (B3LYP) with the 6-311G(d,p) basis set were
used to compute the geometries and the normal mode vibration
frequencies of the starting structure 7, the corresponding transition
structure TS, and the model compound 9. For single-point energy
calculations on DFT-optimized geometries, the SCS-MP2 method
was used.[27] The transition structure was localized by the option:
opt = qst3, by using approximate geometries of the corresponding
starting compound, transition state and product. In order to verify
the character of the stationary points, they were subjected to fre-
quency analyses. In the text, total energies (0 K, kcal/mol) are dis-
cussed, which contain zero-point corrections. The vibration related
to the imaginary frequency corresponds to the nuclear motion
along the reaction coordinate under study. An intrinsic reaction
coordinate (IRC) calculation was performed in order to unambigu-
ously interconnect the transition structure with the reactant and
the product.
(79.5 MHz, [D ]THF): δ = –1.4 ppm. IR (CsI, paraffin): ν = 1593
˜
8
[m, ν(C=C), phenyl], 1464 (vs), 1375 [vs, paraffin], 1306 (s), 1265
(m), 1250 [w, δ(CH3)], 1184 (vw), 1169 (m), 1157 (m), 1109 (s), 1055
(vw), 1026 (w), 1003 (m), 960 (w), 951 (w), 918 (w), 903 (w), 845
(s), 806 (s), 764 [s, ν(CC), δ(CH)], 741 [s, δ(C=C)], 719 [vs, paraffin],
696 (m), 682 (w), 646 (m), 621 [w, phenyl], 596 (s), 567 (m), 542
(s), 515 (vs), 469 (m), 441 [m, ν(SiC), ν(AlC), δ(CC)] cm–1. MS (EI,
20 eV, 373 K): m/z (%) = 526 (0.4) [M+ – THF]; 469 (17) [M+
THF – tBu]; 386 (100) [cyclo-Ph2Si–C{=C(H)–C6H5}–CH=C–
C6H5]+. C40H47AlOSi (598.9): calcd. C 80.2, H 7.9; found C 79.3,
H 7.8.
–
Crystal Structure Determinations: Single crystals were obtained di-
rectly from the reaction mixtures as described above. The crystallo-
graphic data were collected with a Bruker APEX diffractometer
with graphite-monochromated Cu-Kα or Mo-Kα radiation. The
crystals were coated with perfluoropolyether, picked up with a glass
Acknowledgments
We are grateful to the Deutsche Forschungsgemeinschaft for gener-
ous financial support.
Table 1. Crystal data and structure refinement for compounds 1–4.[a,b]
1·C6F5H
2
3
4
Empirical formula
Temperature [K]
Crystal system
Space group[23]
a [pm]
b [pm]
c [pm]
C44H44AlF5Si
153(2)
C40H47AlSi
153(2)
C48H66Al2Si
153(2)
C44H58Al2Si
153(2)
Monoclinic
P21/c (no. 14)
1450.97(2)
1105.09(2)
2483.31(4)
90
103.352(1)
90
3.8742(1)
4
1.239
1.204 (Cu-Kα)
0.17ϫ 0.15ϫ 0.09 0.21ϫ 0.16ϫ 0.04
3.13 Յ 72.68
–17 Յ h Յ 17
–13 Յ k Յ 13
–29 Յ l Յ 30
Triclinic
Monoclinic
P21/c (no. 14)
1290.95(3)
1877.33(4)
1866.25(4)
90
97.078(1)
90
4.4885(2)
4
Orthorhombic
Pccn (no. 56)
1290.38(5)
1624.45(6)
1970.80(8)
90
90
90
4.1311(3)
4
1.076
1.104 (Cu-Kα)
0.26ϫ 0.12ϫ 0.07
4.38 Յ 72.43
–15 Յ h Յ 15
–20 Յ k Յ 20
–23 Յ l Յ 24
¯
P1 (no. 2)
960.40(6)
1093.04(7)
1874.0(2)
96.476(1)
103.069(1)
112.222(1)
1.7306(2)
2
α [°]
β [°]
γ [°]
V [nm3]
Z
Dcalcd. [gcm–3]
1.119
0.119 (Mo-Kα)
1.073
μ [mm–1]
1.049 (Cu-Kα)
0.15ϫ 0.13ϫ 0.04
3.35 Յ 72.33
–14 Յ h Յ 15
–21 Յ k Յ 21
–22 Յ l Յ 22
Crystal size [mm]
θ range [°]
Index ranges
1.14 Յ 28.69
–12 Յ h Յ 12
–14 Յ k Յ 14
–25 Յ l Յ 25
Independent reflections
7402 (Rint
0.0304)
468
0.0426 (6481)
0.1241
=
8885 (Rint = 0.0249) 8482 (Rint = 0.0409) 4008 (Rint =
0.0452)
250
Parameters
387
472
R1 [IϾ2σ(I)][c]
wR2 (all data)[c]
0.0425 (7166)
0.1193
+0.388/–0.307
0.0438 (6657)
0.1210
+0.402/–0.202
0.0447 (3333)
0.1299
+0.372/–0.190
Max./min. residual electron density [1030 em–3] +0.457/–0.354
[a] Programme SHELXL-97;[24] solutions by direct methods, full-matrix refinement with all independent structure factors. [b] See ref.[25]
for CCDC reference numbers. [c] R1 = Σ||Fo | – |Fc||/Σ|Fo|; wR2 = {Σ[w(Fo – Fc ) ]/ Σ[w(Fo2)2]}1/2
.
2
2 2
1366
www.eurjic.org
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 1359–1368

Hydroalumination of Bis(alkynyl)silanes
Table 2. Crystal data and structure refinement for compounds 5 to 6 and 8.[a,b]
5
6
8
Empirical formula
Temperature [K]
Crystal system
Space group[23]
a [pm]
b [pm]
c [pm]
C46H62Al2Si
153(2)
C60H94Al2ClNSi
153(2)
C40H47AlOSi
153(2)
Orthorhombic
Pccn (no. 56)
1263.69(2)
1716.16(3)
1996.22(3)
90
Monoclinic
P21 (no. 4)[c]
1202.42(6)
1984.98(7)
1239.51(5)
90
Monoclinic
P21/c (no. 14)
2043.49(3)
1029.78(2)
1763.94(3)
90
α [°]
β [°]
90
90
4.3292(1)
99.084(3)
90
2.9213(2)
106.631(1)
90
3.5567(1)
γ [°]
V [nm3]
Z
4
2
4
Dcalcd. [gcm–3]
1.069
1.076
1.118
μ [mm–1]
Crystal size [mm]
θ range [°]
Index ranges
1.071 (Cu-Kα)
0.16ϫ 0.04ϫ 0.04
4.34 Յ 72.81
–14 Յ h Յ 15
–21 Յ k Յ 19
–22 Յ l Յ 19
4188 (Rint = 0.0591)
229
1.320 (Cu-Kα)
0.14ϫ 0.12ϫ 0.11
3.61 Յ 72.26
–12 Յ h Յ 14
–24 Յ k Յ 20
–15 Յ l Յ 15
8600 (Rint = 0.0502)
602
1.026 (Cu-Kα)
0.49ϫ 0.48ϫ 0.09
2.26 Յ 72.52
–23 Յ h Յ 24
–12 Յ k Յ 10
–18 Յ l Յ 21
6248(Rint = 0.0392)
394
Independent reflections
Parameters
R1 [IϾ2σ(I)][d]
0.0656 (3174)
0.1950
+0.753/–0.539
0.0519 (7766)
0.1358
+0.658/–0.261
0.0495 (5353)
0.1457
+0.452/–0.247
wR2 (all data)[d]
Max./min. residual electron density [1030 em–3]
[a] Programme SHELXL-97;[24] solutions by direct methods, full-matrix refinement with all independent structure factors. [b] See ref.[25]
2
2 2
for CCDC reference numbers. [c] Flack parameter: 0.003(17). [d] R1 = Σ||Fo | – |Fc||/Σ|Fo|; wR2 = {Σ[w(Fo – Fc ) ]/ Σ[w(Fo2)2]}1/2
.
[9] W. Uhl, M. Rohling, E.-U. Würthwein, N. Ghavtadze, K. Ber-
gander, Organometallics 2010, 29, 5236–5240.
[10] W. Uhl, M. Rohling, J. Kösters, New J. Chem. 2010, 34, 1630–
1636.
[11] a) B. Wrackmeyer, E. Khan, R. Kempe, Appl. Organomet.
Chem. 2007, 21, 39–45; b) B. Wrackmeyer, E. Khan, R. Kempe,
Appl. Organomet. Chem. 2008, 22, 383–388; c) E. Khan, R.
Kempe, B. Wrackmeyer, Appl. Organomet. Chem. 2009, 23,
124–131.
[12] a) W. Uhl, F. Breher, S. Haddadpour, R. Koch, M. Matar, Z.
Anorg. Allg. Chem. 2004, 630, 1839–1845; b) W. Uhl, E. Er, A.
Hepp, J. Kösters, M. Layh, M. Rohling, A. Vinogradov, E.-U.
Würthwein, N. Ghavtadze, Eur. J. Inorg. Chem. 2009, 3307–
3316.
[13] W. Uhl, D. Heller, M. Rohling, J. Kösters, Inorg. Chim. Acta
2011, 374, 359–365.
[1] a) G. Reeske, G. Bradtmüller, M. Schürmann, K. Jurkschat,
Chem. Eur. J. 2007, 13, 10239–10245; b) G. Reeske, M.
Schürmann, K. Jurkschat, Dalton Trans. 2008, 3398–3400; c)
A. C. Tagne Kuate, G. Reeske, M. Schürmann, B. Costisella,
K. Jurkschat, Organometallics 2008, 27, 5577–5587; d) T. W.
Hudnall, Y.-M. Kim, M. W. P. Bebbington, D. Bourissou, F. P.
Gabbai, J. Am. Chem. Soc. 2008, 130, 10890–10891; e) S. Solé,
F. P. Gabbai, Chem. Commun. 2004, 1284–1285; f) T. D. Hud-
nall, C.-W. Chiu, F. P. Gabbai, Acc. Chem. Res. 2009, 42, 388–
397; g) M. Melaimi, F. P. Gabbai, Adv. Organomet. Chem. 2005,
53, 61–99; h) A. Cottone III, M. J. Scott, Organometallics 2002,
21, 3610–3627.
[2] a) M. Layh, W. Uhl, Polyhedron 1990, 9, 277–282; b) W. Uhl,
M. Layh, J. Organomet. Chem. 1991, 415, 181–190.
[3] a) W. Uhl, M. Layh, Z. Anorg. Allg. Chem. 1994, 620, 856–862;
b) W. Uhl, M. Koch, M. Heckel, W. Hiller, H. H. Karsch, Z.
Anorg. Allg. Chem. 1994, 620, 1427–1433; c) W. Uhl, F. Hanne-
mann, W. Saak, R. Wartchow, Eur. J. Inorg. Chem. 1998, 921–
926; d) W. Uhl, F. Hannemann, J. Organomet. Chem. 1999,
579, 18–23.
[14]
[15]
a) W. Uhl, H. R. Bock, F. Breher, M. Claesener, S. Haddadp-
our, B. Jasper, A. Hepp, Organometallics 2007, 26, 2363–2369;
b) W. Uhl, M. Claesener, Inorg. Chem. 2008, 47, 4463–4470.
Selected examples: a) D. Zhang, Eur. J. Inorg. Chem. 2007,
3077–3082; b) A. Asadi, A. G. Avent, M. P. Coles, C. Eaborn,
P. B. Hitchcock, J. D. Smith, J. Organomet. Chem. 2004, 689,
1238–1248; c) T. D. Graham, C. Ong, P. Wei, D. W. Stephan,
J. Organomet. Chem. 2007, 692, 4481–4485; d) X. Tian, R.
Fröhlich, N. W. Mitzel, Z. Anorg. Allg. Chem. 2006, 632, 307–
312; e) A. Jabri, C. B. Mason, Y. Sim, S. Gambarotta, T. J.
Burchell, R. Duchateau, Angew. Chem. 2008, 120, 9863–9867;
Angew. Chem. Int. Ed. 2008, 47, 9717–9721; f) P. Wie, D. W.
Stephan, Organometallics 2003, 22, 1712–1717; g) A. Jabri, C.
Temple, P. Crewdson, S. Gambarotta, I. Korobkov, R. Duch-
ateau, J. Am. Chem. Soc. 2006, 128, 9238–9247; h) D. Chakra-
borty, E. Y.-X. Chen, Inorg. Chem. Commun. 2002, 5, 698–701;
i) M. Tschinkl, R. E. Bachman, F. P. Gabbai, Chem. Commun.
1999, 1367–1368; j) W. Uhl, M. Layh, J. Organomet. Chem.
1991, 415, 181–190; k) C. N. MacMahon, J. A. Francis, A. R.
Barron, J. Chem. Crystallogr. 1997, 27, 191–194.
[4] a) W. Uhl, Coord. Chem. Rev. 2008, 252, 1540–1563; b) W. Uhl,
A. Hepp, H. Westenberg, S. Zemke, E.-U. Würthwein, J.
Hellmann, Organometallics 2010, 29, 1406–1412; c) W. Uhl, M.
Claesener, A. Hepp, B. Jasper, A. Vinogradov, L. van Wüllen,
T. K.-J. Köster, Dalton Trans. 2009, 10550–10562.
[5] a) W. Uhl, M. Claesener, A. Hepp, Organometallics 2008, 27,
2118–2122; b) W. Uhl, M. Claesener, Inorg. Chem. 2008, 47,
729–735.
[6] a) W. Uhl, J. Grunenberg, A. Hepp, M. Matar, A. Vinogradov,
Angew. Chem. 2006, 118, 4465–4468; Angew. Chem. Int. Ed.
2006, 45, 4358–4361; b) W. Uhl, A. Vinogradov, S. Grimme, J.
Am. Chem. Soc. 2007, 129, 11259–11264.
[7] W. Uhl, D. Heller, Z. Anorg. Allg. Chem. 2010, 636, 581–588.
[8] a) W. Uhl, H. R. Bock, M. Claesener, M. Layh, I. Tiesmeyer,
E.-U. Würthwein, Chem. Eur. J. 2008, 14, 11557–11564; b) W.
Uhl, M. Claesener, S. Haddadpour, B. Jasper, I. Tiesmeyer, S.
Zemke, Z. Anorg. Allg. Chem. 2008, 634, 2889–2896.
[16]
F. H. Allen, O. Kennard, D. G. Watson, L. Brammer, A. G.
Orpen, R. Taylor, J. Chem. Soc. Perkin Trans. 2 1987, S1–S19.
Eur. J. Inorg. Chem. 2012, 1359–1368
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1367

W. Uhl, D. Heller, J. Kösters, E.-U. Würthwein, N. Ghavtadze
FULL PAPER
[17] a) B. Wrackmeyer, G. Kehr, J. Süß, Chem. Ber. 1993, 126, 2221–
2226; b) E. Khan, S. Bayer, B. Wrackmeyer, Z. Naturforsch. B
2009, 64, 47–57; c) G. Dierker, J. Ugolotti, G. Kehr, R.
Fröhlich, G. Erker, Adv. Synth. Catal. 2009, 351, 1080–1088;
d) B. Wrackmeyer, W. Milius, E. V. Klimkina, Y. N. Bubnov,
Chem. Eur. J. 2001, 7, 775–782.
[21]
O. T. Beachley Jr., L. Victoriano, Organometallics 1988, 7, 63–
67.
[22]
[23]
M. E. Freeburger, L. Spialter, J. Org. Chem. 1970, 35, 652–657.
T. Hahn (Ed.), International Tables for Crystallography, Space-
Group Symmetry, Vol. A, Kluwer Academic Publishers, Dord-
recht-Boston-London, 1989.
[18] a) J. Pinkas, I. Cisarova, R. Gyepes, M. Horacek, J. Kubista,
J. Cejka, S. Gomez-Ruiz, E. Hey-Hawkins, K. Mach, Organo-
metallics 2008, 27, 5532–5547; b) N. Pirio, S. Bredeau, L. Du-
puis, P. Schütz, B. Donnadieu, A. Igau, J.-P. Majoral, J.-C. Gu-
illemin, P. Meunier, Tetrahedron 2004, 60, 1317–1327; c) Z. Xi,
R. Fischer, R. Hara, W.-H. Sun, Y. Obora, N. Suzuki, K.
Nakajima, T. Takahashi, J. Am. Chem. Soc. 1997, 119, 12842–
12848; d) M. Horacek, N. Bazyakina, P. Stepnicka, R. Gyepes,
I. Cisarova, S. Bredeau, P. Meunier, J. Kubista, K. Mach, J.
Organomet. Chem. 2001, 628, 30–38; e) A. C. Dema, C. M. Lu-
kehart, A. T. McPhail, D. R. McPhail, J. Am. Chem. Soc. 1989,
111, 7615–7616; f) M. Zirngast, C. Marschner, J. Baumgartner,
Organometallics 2008, 27, 2570–2583; g) P.-M. Pellny, N. Peu-
lecke, V. V. Burlakov, W. Baumann, A. Spannenberg, U. Rosen-
thal, Organometallics 2000, 19, 1198–1200; h) C. K. Jin, T. Ya-
mada, S. Sano, M. Shiro, Y. Nagao, Tetrahedron Lett. 2007, 48,
3671–3675; i) D. Ostendorf, L. Kirmaier, W. Saak, H.
Marsmann, M. Weidenbruch, Eur. J. Inorg. Chem. 1999, 2301–
2307; j) D. Ostendorf, W. Saak, D. Haase, M. Weidenbruch, J.
Organomet. Chem. 2001, 636, 7–11; k) D. Ostendorf, W. Saak,
M. Weidenbruch, H. Marsmann, Organometallics 2002, 21,
636–640; l) D. Ostendorf, W. Saak, M. Weidenbruch, H.
Marsmann, Organometallics 2000, 19, 4938–4940; m) C. K. Jin,
T. V. Dang, Y. Ikee, T. Yamada, S. Sano, M. Shiro, Y. Nagao,
Heterocycles 2006, 70, 71–75.
[24]
a) SHELXTL-Plus, REL. 4.1, Siemens Analytical X-RAY In-
struments Inc., Madison,WI, 1990; b) G. M. Sheldrick,
SHELXL-97, Program for the Refinement of Structures, Uni-
versity of Göttingen, 1997.
[25] CCDC-796937 (for 1), -840608 (for 2), -796938 (for 3), -796939
(for 4), -796940 (for 5), -796941 (for 6) and -840607 (for 8)
contain the supplementary crystallographic data for this paper.
These data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif..
[26] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, B.
Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li,
H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng, J. L. Son-
nenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hase-
gawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai,
T. Vreven, J. A. Montgomery Jr., J. E. Peralta, F. Ogliaro, M.
Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V. N. Starov-
erov, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell,
J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J. M.
Millam, M. Klene, J. E. Knox, J. B. Cross, V. Bakken, C. Ad-
amo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev,
A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Mar-
tin, K. Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador,
J. J. Dannenberg, S. Dapprich, A. D. Daniels, O. Farkas, J. B.
Foresman, J. V. Ortiz, J. Cioslowski, and D. J. Fox, Gaussian 09,
Revision A.02, Gaussian, Inc., Wallingford CT, 2009. Details of
the quantum chemical calculations (Gaussian archive entries)
may be obtained from E.-U. W. upon request.
[19] a) D. Yan, J. Mohsseni-Ala, N. Auner, M. Bolte, J. W. Bats,
Chem. Eur. J. 2007, 13, 7204–7214; b) D. Yan, M. Bolte, N.
Auner, J. Organomet. Chem. 2008, 693, 908–916; c) J. Liu, S.
Zhang, W.-X. Zhang, Z. Xi, Organometallics 2009, 28, 413–
417; and references cited therein.
[20] a) W. Uhl, L. Cuypers, R. Graupner, J. Molter, A. Vester, B.
Neumüller, Z. Anorg. Allg. Chem. 2001, 627, 607–614; b) W.
Uhl, L. Cuypers, G. Geiseler, K. Harms, W. Massa, Z. Anorg.
Allg. Chem. 2002, 628, 1001–1006.
[27] S. Grimme, J. Chem. Phys. 2003, 118, 9095–9102.
Received: August 25, 2011
Published Online: November 7, 2012
1368
www.eurjic.org
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 1359–1368