Hydroalumination of dialkynylgermanes - Synthesis of alkenyl- alkynylgermanes with intramolecular aluminium-carbon interactions

Article abstract of DOI:10.1039/c0nj00050g

Reactions of dialkylaluminium hydrides, R₂AlH [R = CH ₂CMe₃, CMe₃, CH(SiMe₃)₂], with di(phenylethynyl)germanes, R₂Ge(CC-C₆H ₅)₂ [R = CH₃ (1), C₆H₅ (2)], afforded mixed alkenyl-alkynylgermanes, R₂Ge(CC-C ₆H₅)[C(AlR₂)C(H)-C₆H₅] (3 to 7), by hydroalumination of one of the CC triple bonds. In all cases the cis-arrangement of the Al and H atoms across the resulting CC double bond was observed. Crystal structure determinations revealed relatively strong intramolecular bonding interactions between the coordinatively-unsaturated aluminium atoms and the α-carbon atoms of the intact triple bonds bearing a partial negative charge. This interaction is only prevented by application of the very bulky bis(trimethylsilyl)methyl substituent.

Full text of DOI:10.1039/c0nj00050g

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Hydroalumination of dialkynylgermanes—synthesis of
alkenyl–alkynylgermanes with intramolecular aluminium–carbon
interactionswz
¨
Werner Uhl,* Martina Rohling and Jutta Kosters
Received (in Montpellier, France) 22nd January 2010, Accepted 30th March 2010
DOI: 10.1039/c0nj00050g
Reactions of dialkylaluminium hydrides, R2AlH [R = CH2CMe3, CMe3, CH(SiMe3)2], with
di(phenylethynyl)germanes, R2Ge(CRC–C6H5)2 [R = CH3 (1), C6H5 (2)], afforded mixed
alkenyl–alkynylgermanes, R2Ge(CRC–C6H5)[C(AlR2)QC(H)–C6H5] (3 to 7), by
hydroalumination of one of the CRC triple bonds. In all cases the cis-arrangement of the Al and
H atoms across the resulting CQC double bond was observed. Crystal structure determinations
revealed relatively strong intramolecular bonding interactions between the coordinatively-
unsaturated aluminium atoms and the a-carbon atoms of the intact triple bonds bearing a partial
negative charge. This interaction is only prevented by application of the very bulky
bis(trimethylsilyl)methyl substituent.
dialkynes possessing a geminal arrangement of two triple
Introduction
bonds. These reactions have importance beyond the generation
of simple acceptor molecules. Monoaddition products,
for instance, have a coordinatively-unsaturated, highly Lewis-
acidic aluminium atom in close proximity to the a-carbon
atom of the alkynyl group which bears a relatively high
negative charge. This may initiate secondary reactions by
rearrangement similar to those observed for organoboron
derivatives.14 We report here on our first results obtained with
germanium.
Hydroalumination is a very effective method for the reduction
of unsaturated organic compounds and the generation of a
broad variety of mono- or oligonuclear aluminium compounds.1,2
Recent investigations of our group into the hydroalumination
of alkynes showed that in many cases the simple addition
products, R–C(H)QC(AlR02)–R0 0, are only transient species
which give very fast secondary reactions via condensation
and release of the corresponding trialkylelement derivatives.2
Carbaalane clusters3 or cyclophane-type molecules with up to
three aluminium atoms bridging two benzene rings4,5 are the
most prominent products of these reactions. Condensation
was prevented with very small alkyl groups attached to
aluminium (caused by polymerization),5 by steric shielding
with very bulky substituents6 or with trimethylsilylethyne
derivatives.7,8 Similar results were obtained upon the
addition of Ga–H bonds to alkynes.8–11 But interestingly hydro-
gallation proved to be more selective than hydroalumination
and more products could be isolated in a pure form. The
latter method merits a broader application in preparative
chemistry.
Results and discussion
Synthesis of di(phenylethynyl)germanium compounds
Two different di(phenylethynyl)germanium compounds
[R2Ge(CRC–C6H5)2; R = Me (1), C6H5 (2)] were generated
by treatment of the corresponding diorganylgermanium
dichlorides with two equivalents of phenylethynyllithium in
diethyl ether/n-hexane solutions, eqn (1), according to a
procedure published for the generation of the corresponding
diethynylsilicon compounds.15 After crystallization from
n-pentane both products were isolated as colourless solids in
66 to 80% yields and characterized by NMR spectroscopy and
mass spectrometry. The carbon atoms of the CRC triple
bonds have the expected chemical shifts in the 13C NMR
spectra [d at about 90 (GeC) and 105]. Absorptions at about
2160 cmꢀ1 in the IR spectra are characteristic of the ethynyl
moiety. Crystal structure determination of 1 (Fig. 1) revealed
an only slightly distorted tetrahedral surrounding of the
germanium atom with bond angles between 106.5(1) and
114.3(1)1. The smallest angle is observed between the a-carbon
atoms of the ethynyl groups, while the largest one occurs
between the methyl substituents. The length of the CRC
triple bonds [119.7(3) pm] corresponds to the standard value.16
The alkynyl groups are almost ideally linear with bond angles
of 177.0(2)1 (Ge–C1–C2) and 178.2(2)1 (C1RC2–C3). Only
few structurally authenticated diethynylgermanium compounds
Trimethylsilylethynes gave relatively stable addition
products7,8,11 which have up to four coordinatively-unsaturated
aluminium or gallium atoms in a single molecule and are
applicable as chelating Lewis-acids.12 So far we were very
much focused on the application of benzene centred oligoalkynyl
derivatives. In order to systematically change the properties
of these oligoacceptors we started with investigations into
the hydroalumination of silicon13 or germanium centred
Institut fur Anorganische und Analytische Chemie, Universitat
¨
¨
¨
Munster, D-48149 Munster, Germany. E-mail: uhlw@uni-muenster.de
¨
w Dedicated to Prof. Pascal Le Floch. This article is part of a themed
issue on Main Group chemistry.
z CCDC reference numbers CCDC 762758–762762. For crystallo-
graphic data in CIF or other electronic format see DOI: 10.1039/
c0nj00050g
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between d = 150 and 160 of the 13C-NMR spectrum, while
the carbon atoms of the ethynyl groups resonate at about
d = 112 (C–Ph) and 95 (C–Ge). The vinylic hydrogen atoms
resulting from the addition of the Al–H bond to the triple
bond have chemical shifts in the 1H-NMR spectrum at d = 8.0
to 8.5 which represents the normal range observed also for the
hydroalumination products of silylethynyl derivatives.7,8,11,13
Reactions of the dialkynylgermanes with dimethyl- and
diethylaluminium hydrides yielded only mixtures of many
unknown products which could not be separated. Diisobutyl-
aluminium hydride gave the addition products in a relatively
impure form. They could not be purified by recrystallization of
the highly viscous raw products.
Fig. 1 Molecular structure of 1. The thermal ellipsoids are drawn at
the 40% probability level. Hydrogen atoms are omitted. Important
bond lengths (pm) and angles (1): Ge(1)–C(1) 191.5(2), Ge(1)–C(4)
193.1(2), C(1)–C(2) 119.7(3), C(1)–Ge(1)–C(1)0 106.5(1), C(1)–Ge(1)–C(4)
107.53(8), C(4)–Ge(1)–C(4)0 114.3(1), Ge(1)–C(1)–C(2) 177.0(2),
C(1)–C(2)–C(3) 178.2(2); C(1)0 and C(4)0 generated by ꢀx + 1, y,
ꢀz + 0.5.
with relatively complicated molecular structures have been
published in the literature.17
ð1Þ
ð2Þ
Compounds 3 and 5 to 7 were characterized by crystal
structure determinations (Fig. 2–5). The central germanium
atoms have a distorted tetrahedral coordination sphere and
are bonded to two terminal methyl or phenyl substituents, an
alkenyl and an intact alkynyl group. The CQC double (132 to
135 pm) and CRC triple bond lengths (120 to 121 pm)
correspond to standard values.16 The aluminium atoms are
bonded exclusively to the a-carbon atoms of the alkenyl
groups even in the case of the very bulky bis[bis(trimethylsilyl)-
methyl]aluminium substituent (7). The selective attack of the
positively charged aluminium atoms at this particular position
reflects the charge separation in the starting bisalkynes which
results from the electronegativity difference between the
sp-hybridized carbon atoms and germanium. The aluminium
atom has an almost ideally planar surrounding only in the
bis(trimethylsilyl)methyl compound 7 (deviation of the Al
atom from the C3 plane: 1.1 pm). In all other cases (3, 5 and
6) the aluminium atoms deviate considerably from the plane
spanned by the three directly bonded carbon atoms by 19.2 (5)
and about 34 pm (3 and 6). The pyramidal configuration of the
AlC3 moieties is caused by an intramolecular interaction of the
Reactions of the di(phenylethynyl)germanium compounds with
dialkylaluminium hydrides
The di(phenylethynyl)germanium compounds
1 and 2
were treated with equimolar quantities of dialkylaluminium
hydrides, R2AlH [R = CH2CMe3, CMe3, CH(SiMe3)2], in
n-hexane as the solvent, eqn (2). Independently of the strongly
differing steric shielding by the alkyl groups attached to
aluminium the reactions are completed after about 4 h at
room temperature. The colourless, solid products 3 to 7 were
isolated in 55 to 87% yield. The compounds 3, 5 and 6
decompose above 95 1C to give yellowish oils. Only the
sterically most shielded bis(trimethylsilyl)methyl compounds
4 and 7 melt reproducibly without decomposition at 111 and
119 1C, respectively. This behavior may correlate to the
different molecular structures in the solid state as discussed
below. NMR spectra show the resonances of two different
phenyl substituents as well as resonances characteristic of
CQC double and CRC triple bonds. This is in accordance
with the selective hydroalumination of only one alkynyl group.
Both signals of the ethenyl carbon atoms are in a narrow range
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Fig. 2 Molecular structure of 3. The thermal ellipsoids are drawn at
the 40% probability level. Hydrogen atoms with the exception of the
vinylic hydrogen atom are omitted. Important bond lengths (pm) and
angles (1) (values of the second molecule in square brackets):
Al(1)–C(111) 198.1(2) [198.9(2)], Al(1)–C(121) 245.1(2) [240.5(2)],
Ge(1)–C(111) 193.9(2) [193.8(2)], Ge(1)–C(121) 197.4(2) [198.0(2)],
C(111)–C(112) 132.5(3) [132.6(3)], C(121)–C(122) 120.0(3) [120.2(3)],
C(111)–Ge(1)–C(121) 94.02(8) [93.45(8)], Ge(1)–C(111)–Al(1)
100.82(8) [100.06(8)], Ge(1)–C(111)–C(112) 130.0(1) [127.7(1)],
Ge(1)–C(121)–C(122) 175.3(2) [173.9(2)], C(121)–C(122)–C(123)
176.7(2) [176.9(2)].
Fig. 4 Molecular structure of 6. The thermal ellipsoids are drawn at
the 40% probability level. Hydrogen atoms with the exception of the
vinylic hydrogen atom are omitted. Important bond lengths (pm) and
angles (1): Al(1)–C(11) 199.6(2), Al(1)–C(21) 244.6(2), Ge(1)–C(11)
193.5(2), Ge(1)–C(21) 196.8(2), C(11)–C(12) 134.1(3), C(21)–C(22)
120.7(3), C(11)–Ge(1)–C(21) 93.46(9), Ge(1)–C(11)–Al(1) 101.2(1),
Ge(1)–C(11)–C(12) 128.6(2), Ge(1)–C(21)–C(22) 177.5(2), C(21)–
C(22)–C(23) 177.9(2).
Fig. 3 Molecular structure of 5. The thermal ellipsoids are drawn at
the 40% probability level. Hydrogen atoms with the exception of the
vinylic hydrogen atom are omitted. Important bond lengths (pm) and
angles (1): Al(1)–C(11) 199.4(2), Al(1)–C(21) 248.1(2), Ge(1)–C(11)
194.9(2), Ge(1)–C(21) 195.0(2), C(11)–C(12) 133.4(3), C(21)–C(22)
120.3(3), C(11)–Ge(1)–C(21) 93.21(7), Ge(1)–C(11)–Al(1) 102.26(8),
Ge(1)–C(11)–C(12) 124.6(1), Ge(1)–C(21)–C(22) 176.5(2), C(21)–
C(22)–C(23) 177.0(2).
Fig. 5 Molecular structure of 7 (only one of the two independent
molecules is shown). The thermal ellipsoids are drawn at the 40%
probability level. Hydrogen atoms with the exception of the vinylic
hydrogen atom and methyl groups are omitted. Important bond
lengths (pm) and angles (1) (values of the second molecule in square
brackets): Al(1)–C(141) 198.1(3) [196.7(4)], Ge(1)–C(131) 189.3(4)
[188.9(5)], Ge(1)–C(141) 193.8(3) [195.6(4)], C(131)–C(132) 121.4(6)
[121.0(7)], C(141)–C(142) 134.6(5) [133.3(6)], C(131)–Ge(1)–C(141)
110.9(2) [113.0(2)], Ge(1)–C(141)–Al(1) 124.2(2) [122.3(2)],
Ge(1)–C(141)–C(142) 124.9(3) [123.5(3)], Ge(1)–C(131)–C(132)
173.8(4) [174.9(6)], C(131)–C(132)–C(133) 179.0(5) [177.7(6)].
coordinatively-unsaturated metal atoms with the a-carbon
atoms of the intact ethynyl groups which bear a partial
negative charge (the b-carbon atom is too far apart for
a significant bonding interaction due to the constraints
of the AlCGeCC linkage). The resulting Al–C(a) distances
(240.5 to 248.1 pm) are relatively long compared to the
values of o200 pm for the terminal Al–C bonds, but the
relevance of these interactions is underlined by several
observations: (i) the aluminium atoms have a pyramidal
configuration, (ii) the torsion angles across the Ge–C(vinyl)
bonds [C(ethynyl)–Ge–C(ethenyl)–Al] are close to 01 in order
to allow an optimum interaction, and (iii) the C–Ge–C angles
between the a-carbon atoms of the ethenyl and ethynyl groups
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are relatively small (941). Despite this significant interaction
the Ge–CRC groups deviate only slightly from linearity with
angles of 173.8 to 179.01. However, bending is not required
because the Lewis-acidic aluminium atom may interact with a
p-orbital essentially located at the negatively charged a-carbon
atom of the triple bond. Similar interactions have been
determined by NMR spectroscopy or crystal structure
determinations for products of the hydroboration or hydro-
alumination of silicon centred bisalkynes.13,14 The bulky
bis(trimethylsilyl)methyl group prevents this interaction. The
respective torsion angles across the Ge–C bonds (95.21)
indicate an almost perpendicular arrangement of the relevant
groups, and the C–Ge–C bond angle between the ethenyl
and ethynyl groups (112.01 on average) resembles the
normal tetrahedral angle. IR spectroscopy allows a simple
differentiation between both structural motifs. The bis-
(trimethylsilyl)methyl compounds have only one absorption
for the CRC stretching vibration, while two absorptions
result for those compounds which have the intramolecular
Al–C interaction. In all cases the H and Al atoms of
the ethenyl groups adopt a cis arrangement, and cis/trans
isomerisation8,11 did not take place. Intermolecular activation
is required to initiate this rearrangement process which may be
prevented here by steric shielding and the intramolecular Al–C
interaction.
Syntheses of the diethynylgermanium compounds
R2Ge(CRCPh)2 1 (R = Me) and 2 (R = C6H5); general
procedure
A solution of n-butyllithium (1.6 M) in n-hexane was added
dropwise to a solution of equimolar quantities of phenylethyne
(about 30 mmol) in 50 ml of diethyl ether at ꢀ78 1C. The
mixture was stirred for 2 h, and half an equivalent of dimethyl-
or diphenylgermanium dichloride (about 15 mmol) was added
dropwise. After 2 h at ꢀ78 1C the mixture was warmed to
room temperature and further stirred for 16 h. The suspension
was treated with 100 ml of diluted aqueous HCl (10%) and 50 ml
of diethyl ether. The organic phase was separated and the
aqueous phase was extracted three times with 20 ml of diethyl
ether. The combined organic phases were dried over MgSO4 and
filtrated. The solvent was removed under reduced pressure. The
residue was recrystallized from n-pentane (20/ꢀ30 1C).
Characterization of Me2Ge(CRCPh)2 1
Yield 80%. Mp (argon, sealed capillary): 93 1C. Found C 70.4,
H 5.5%. Calcd for C18H16Ge C 70.9, H 5.3%. Mass spectrum
(EI, 20 eV, 30 1C, only the most intense masses are given,
the isotopic patterns are in complete agreement with the
calculated ones): m/z (%) = 306 (100) [M]+, 291 (88)
[M ꢀ CH3]+, 175 (15) [Ge(CRCPh)]+. 1H NMR (C6D6,
400 MHz): d 0.59 (s, 6H, GeCH3), 6.92 (m, 6H, meta-H,
para-H), 7.47 (m, 4H, ortho-H). 13C NMR (C6D6): d 0.8
(CH3), 91.0 (CCPh), 105.5 (CCPh), 123.6 (ipso-C), 128.5
(meta-C), 128.7 (para-C), 132.3 (ortho-C). IR (Nujol, cmꢀ1):
2158 m n(CRC), 1888 vw, 1597 w (phenyl), 1463 vs, 1377 vs
(Nujol), 1300 w, 1242 w d(CH3), 1215 m, 1155 w, 1070 w, 1024 m,
968 vw, 914 w, 885 vw, 843 m, 799 s, 754 vs n(CC), 723 s
(Nujol), 689 vs d(phenyl), 665 w, 608 m, 584 s, 532 s n(GeC).
Conclusion
Hydroalumination of diethynylgermanes with one equivalent
of dialkylaluminium hydrides afforded mixed ethynyl–
ethenyl germanium derivatives. An interaction between
the coordinatively-unsaturated aluminium atoms and the
a-carbon atoms of the remaining ethynyl groups was observed
for compounds with relatively small R2Al groups. The
different structural motifs may influence the chemical properties
of these compounds. An obvious difference is their thermal
stability. While bis(trimethylsilyl)methyl derivatives exhibit
a well defined melting point, all compounds having the
intramolecular Al–C interaction decompose by the formation
of a yellow oil. Compounds 3, 5 and 6 are ideally preorganized
to allow elimination of the corresponding dialkylaluminium
alkynides which indeed was observed for hydroalumination
reactions with diethynylphosphines.18 Hence, these ethenyl–
ethynyl germanes are interesting starting compounds for
future investigations.
Characterization of Ph2Ge(CRCPh)2 2
Yield 66%. Mp (argon, sealed capillary): 121 1C. Found C
78.2, H 4.7%. Calcd for C28H20Ge C 78.4, H 4.7%. Mass
spectrum (EI, 20 eV, 120 1C; only the most intense masses are
given, the isotopic patterns are in complete agreement with the
calculated ones): m/z (%) = 429 (100) [M ꢀ H]+, 353 (88)
[M
ꢀ
Ph]+, 329 (56) [M
ꢀ
CRCPh]+, 276 (56)
[Ge(CRCPh)2]+. 1H NMR (C6D6, 400 MHz): d 6.87 (m,
4H, meta-H of alkynyl-Ph), 6.89 (m, 2H, para-H alkynyl-Ph),
7.16 (m, 2H, para-H of GePh2), 7.18 (m, 4H, meta-H of
GePh2), 7.39 (m, 4H, ortho-H of alkynyl-Ph), 7.97 (m, 4H,
ortho-H of GePh2). 13C NMR (C6D6, 100 MHz): d 87.8
(CCPh), 107.9 (CCPh), 123.2 (ipso-C of alkynyl-Ph), 128.5
(meta-C of alkynyl-Ph), 129.0 (meta-C of GePh2, para-C of
alkynyl-Ph), 130.3 (para-C of GePh2), 132.6 (ortho-C of
alkynyl-Ph), 134.4 (ortho-C of GePh2), 134.8 (ipso-C of GePh2).
IR (Nujol, cmꢀ1): 2162 m n(CRC), 1890 vw, 1825 vw, 1595 w,
1574 w (phenyl), 1460 vs, 1377 s (Nujol), 1306 w, 1215 w, 1157 w,
1094 m, 1026 w, 970 vw, 914 w, 814 m, 754 m, 733 s n(CC), 723 s
(Nujol), 694 m d(phenyl), 581 w, 532 m, 463 m n(GeC).
Experimental section
All procedures were carried out under purified argon. n-Hexane,
n-pentane and cyclopentane were dried over LiAlH4, diethyl
ether over Na/benzophenone, and 1,2-difluoro- and pentafluoro-
benzene over molecular sieves (4 A). The starting compounds
(tBuCH2)2AlH,19 tBu2AlH20 and [(Me3Si)2CH]2AlH21 were
obtained according to literature procedures. Commercially
available Cl2GeMe2 and Cl2Ge(C6H5)2 (Aldrich) were applied
as purchased. Phenylethyne was dried over molecular sieves
(4 A). The assignment of the NMR spectra is based on HSQC,
HMBC, ROESY and DEPT135 data.
Hydroalumination of di(phenylethynyl)germanium compounds;
general procedure
A solution of the di(phenylethynyl)germanes 1 and 2 (about
0.6 to 0.8 mmol) in 10 ml of n-hexane was added to equimolar
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quantities of the corresponding dialkylaluminiumhydride
dissolved in 10 ml of n-hexane. The mixture was stirred at
room temperature for 4 h and became yellow in most cases. All
volatiles were removed under reduced pressure. The residue
was recrystallized from n-hexane (20/ꢀ30 1C, 3), cyclopentane
(20/+2 1C, 4), pentafluorobenzene (20/ꢀ30 1C, 5; 20/+2 1C, 7)
or difluorobenzene (20/ꢀ30 1C, 6) to obtain colourless
crystals.
575 m, 532 m, 505 w, 496 w, 476 w, 420 m, 380 w n(AlC),
n(GeC).
Characterization of Ph2Ge(CRCPh)[(AlNp2)QC(H)Ph] 5
Yield 61%. Mp (argon, sealed capillary): 112 1C (dec). Found
C 75.4, H 7.1%. Calcd for C38H43GeAl C 76.2, H 7.2%. Mass
spectrum (EI, 20 eV, 60 1C; only the most intense masses are
given, the isotopic patterns are in complete agreement with the
calculated ones): m/z (%) = 431 (57) [M ꢀ Al(CH2CMe3)2]+,
252 (36) [PhGe(CCPh)]+, 228 (100) [Ph2Ge]+. 1H NMR
(C6D6, 400 MHz): d 0.88 (s, 4H, AlCH2), 1.31 (s, 18H,
CMe3), 6.87 (m, 2H, meta-H alkynyl-Ph), 6.88 (m, 1H,
para-H alkynyl-Ph), 6.92 (m, 1H, para-H alkenyl-Ph), 6.95
(m, 2H, meta-H alkenyl-Ph), 7.12 (m, 2H, para-H GePh2), 7.15
(m, 4H, meta-H GePh2), 7.41 (m, 2H, ortho-H alkenyl-Ph),
7.43 (m, 2H, ortho-H alkynyl-Ph), 7.82 (m, 4H, ortho-H
GePh2), 8.27 (s, 1H, CHPh). 13C NMR spectrum (C6D6,
100 MHz): d 31.9 (CMe3), 33.6 (AlCH2), 35.2 (CMe3), 95.4
(CRCPh), 115.7 (CRCPh), 121.0 (ipso-C alkynyl-Ph), 127.8
(ortho-C alkenyl-Ph), 128.0 (para-C alkenyl-Ph), 128.7
(meta-C alkenyl-Ph, meta-C alkynyl-Ph), 128.9 (meta-C
GePh2), 129.9 (para-C GePh2), 130.4 (para-C alkynyl-Ph),
133.1 (ortho-C alkynyl-Ph), 135.0 (ortho-C GePh2), 136.7
(ipso-C GePh2), 142.5 (ipso-C alkenyl-Ph), 153.0 (CQCHPh),
154.9 (CQCHPh). IR (Nujol, cmꢀ1): 2162 s, 2127 m n(CRC),
1952 vw, 1879 vw, 1765 vw, 1697 w, 1647 vw, 1553 m n(CQC),
phenyl, 1458 vs, 1375 vs (Nujol), 1306 vw d(CH3), 1229 m,
1175 vw, 1157 w, 1125 vw, 1094 w, 1028 m, 918 m, 879 vw,
843 w n(CC), d(CC), 727 m (Nujol), 692 m d(phenyl), 534 w,
509 vw, 461 m n(AlC), n(GeC).
Characterization of Me2Ge(CRCPh)[C(AltBu2)QC(H)Ph] 3
Yield 56%. Mp (argon, sealed capillary): 95 1C (dec). Found C
69.5, H 7.7%. Calcd for C26H35GeAl C 69.8, H 7.9%. Mass
spectrum (EI, 20 eV, 20 1C; only the most intense masses are
given, the isotopic patterns are in complete agreement with the
calculated ones): m/z (%) = 391 (100) [M ꢀ CMe3]+, 307 (10)
[M ꢀ AltBu2]+, 204 (81) [Me2GeCRC–Ph ꢀ H]+. 1H NMR
(C6D6, 400 MHz): d 0.61 (s, 6H, GeMe2), 1.32 (s, 18H, CMe3),
6.86 (m, 2H, meta-H alkynyl-Ph), 6.90 (m, 1H, para-H
alkynyl-Ph), 7.05 (m, 1H, para-H alkenyl-Ph), 7.12 (m, 2H,
meta-H alkenyl-Ph), 7.16 (m, 2H, ortho-H alkenyl-Ph), 7.52
(m, 2H, ortho-H alkynyl-Ph), 8.02 (s, 1H, CHPh). 13C NMR
(C6D6, 100 MHz): d 2.1 (GeMe2), 19.2 (CMe3), 30.3 (CMe3),
93.6 (CRCPh), 116.4 (CRCPh), 120.7 (ipso-C alkynyl-Ph),
127.1 (ortho-C alkenyl-Ph), 127.6 (para-C alkenyl-Ph), 128.7
(meta-C alkenyl-Ph, meta-C alkynyl-Ph), 130.8 (para-C
alkynyl-Ph), 133.8 (ortho-C alkynyl-Ph), 142.7 (ipso-C alkenyl-
Ph), 152.1 (CQCHPh); 155.2 (CQCHPh). IR (Nujol, cmꢀ1):
2158 m, 2114 m n(CRC), 1593 m, 1562 m, 1487 s n(CQC),
phenyl, 1462 vs, 1377 s (Nujol), 1238 m d(CH3), 1215 m, 1177
w, 1070 s, 1026 w, 1001 w, 918 m, 878 w, 835 s, 810 s, 756 s
n(CC), d(CC), 691 s d(phenyl), 625 w, 590 m, 536 m, 509 w,
436 w, 413 w, 382 w, 361 w n(AlC), n(GeC).
Characterization of Ph2Ge(CRCPh)[C(AltBu2)QC(H)Ph] 6
Yield 55%. Mp (argon, sealed capillary): 125 1C (dec). Found
C 74.8, H 6.9%. Calcd for C36H39GeAl C 75.7, H 6.9%. Mass
spectrum (EI, 20 eV, 120 1C; only the most intense masses are
given, the isotopic patterns are in complete agreement with the
calculated ones): m/z (%) = 515 (23) [M ꢀ CMe3]+, 431 (65)
[M ꢀ Al(CMe3)2]+, 353 (20) [PhGe(CCPh)2]+, 252 (36)
[PhGe(CCPh)]+, 228 (100) [Ph2Ge+]. 1H NMR (C6D6,
400 MHz): d 1.36 (s, 18H, CMe3), 6.81 (m, 2H, meta-H
alkynyl-Ph), 6.89 (m, 1H, para-H alkynyl-Ph), 6.93 (m, 1H,
para-H alkenyl-Ph), 6.95 (m, 2H, meta-H alkenyl-Ph), 7.11 (m,
2H, para-H GePh2), 7.13 (m, 4H, meta-H GePh2), 7.42 (m, 2H,
ortho-H alkenyl-Ph), 7.47 (m, 2H, ortho-H alkynyl-Ph), 7.80
(m, 4H, ortho-H GePh2), 8.29 (s, 1H, CHPh). 13C NMR
Characterization of
Me2Ge(CRCPh)(C[Al{CH(SiMe3)2}2]QC(H)Ph) 4
Colourless, waxy solid, yield 72%. Mp (argon, sealed
capillary): 111 1C. Mass spectrum (EI, 20 eV, 30 1C):
m/z (%) = 493 (22) [M ꢀ CH(SiMe3)2]+ (complete isotopic
1
pattern in agreement with a calculated one). H NMR (C6D6,
400 MHz): d 0.05 (s, 2H, AlCH), 0.33 (s, 36H, SiMe3), 0.54
(s, 6H, GeMe2), 6.95 (m, 1H, para-H alkynyl-Ph), 6.99 (m, 2H,
meta-H alkynyl-Ph), 7.05 (m, 1H, para-H alkenyl-Ph), 7.12 (m,
2H, meta-H alkenyl-Ph), 7.39 (m, 2H, ortho-H alkenyl-Ph),
7.53 (m, 2H, ortho-H alkynyl-Ph), 8.19 (s, 1H, CHPh).
13C NMR (C6D6, 100 MHz): d 3.3 (GeMe2), 4.8 (SiMe3),
10.1 (AlCH), 97.9 (PhCRCGe), 107.8 (PhCRCGe), 124.1
(ipso-C alkynyl-Ph), 127.7 (ortho-C alkenyl-Ph), 128.1 (para-C
alkenyl-Ph), 128.5 (meta-C alkynyl-Ph), 128.6 (para-C
alkynyl-Ph, meta-C alkenyl-Ph), 132.4 (ortho-C alkynyl-Ph),
142.8 (ipso-C alkenyl-Ph), 157.0 (CQCHPh), 159.6
(CQCHPh). 29Si NMR (C6D6, 79.5 MHz): d ꢀ2.8. IR (neat,
cmꢀ1): 3080 m, 3059 m, 3022 w, 2949 vs, 2897 vs, 2855 s, 2808
m n(CH), 2154 vs n(CRC), 1946 vw, 1879 vw, 1803 vw, 1751
vw, 1670 vw, 1597 s, 1576 m, 1541 s, 1489 vs n(CQC), phenyl,
1445 s, 1417 m, 1288 m, 1248 vs d(CH3), 1215 s, 1177 w, 1070 s
n(CC), 1013 m d(CHSi2), 932 m, 843 s, 777 m, 754 s r(CH3Si),
689 s, 677 s d(phenyl), nas(SiC), 625 m, 606 m ns(SiC), 586 m,
(C6D6, 100 MHz):
d 19.6 (CMe3), 30.9 (CMe3), 92.5
(CRCPh), 117.6 (CRCPh), 120.6 (ipso-C alkynyl-Ph),
127.9 (ortho-C alkenyl-Ph), 128.1 (para-C alkenyl-Ph), 128.7
(meta-C alkenyl-Ph, meta-C alkynyl-Ph), 128.9 (meta-C
GePh2), 130.0 (para-C GePh2), 131.0 (para-C alkynyl-Ph),
134.0 (ortho-C alkynyl-Ph), 135.0 (ortho-C GePh2), 136.8
(ipso-C GePh2), 142.1 (ipso-C alkenyl-Ph), 150.0 (CQCHPh),
154.2 (CQCHPh). IR (Nujol, cmꢀ1): 2160 w, 2141 w
n(CRC), 1958 w, 1888 w, 1819 w, 1759 w, 1649 w, 1597 w
n(CQC), phenyl, 1458 vs, 1377 vs (Nujol), 1304 m, 1269 m
d(CH3), 1157 m, 1086 s, 1026 m, 997 w, 966 w, 918 m, 891 w,
841 m, 812 m, 754 s n(CC), d(CH3), 723 s (Nujol), 696 s
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Table 1 Crystal data, data collection parameters, and structure refinement details for 1, 3, 5, 6 and 7
1
3
5
6
7
Formula
Fw
Crystal system
Space group
Z
a/pm
b/pm
c/pm
C18H16Ge
304.90
Monoclinic
C2/c (No. 15)
4
1625.68(3)
959.68(2)
1102.82(2)
90
118.958(1)
90
1505.43(5)
153(2)
2.609 (CuKa)
1377 (0.0220)
0.0266 (1304)
0.0728
C26H35AlGe
447.11
Orthorhombic
P212121 (No. 19)
8
1100.26(2)
1377.03(2)
3382.33(5)
90
90
90
5124.5(1)
153(2)
1.994 (CuKa)
9693 (0.0275)
0.0261 (9423)
0.0686
C38H43AlGe
599.29
Monoclinic
P21/c (No. 14)
4
1003.03(2)
3070.31(5)
1099.98(2)
90
98.733(1)
90
3348.2(1)
153(2)
1.655 (CuKa)
5984 (0.0266)
0.0330 (5468)
0.0884
C36H39AlGe
571.24
Triclinic
P1 (No. 2)
2
844.49(3)
991.62(4)
2011.86(7)
87.777(2)
87.692(2)
66.821(2)
1547.0(1)
153(2)
1.768 (CuKa)
5288 (0.0218)
0.0362 (4697)
0.0996
C42H59AlGeSi4
775.82
Triclinic
P1 (No. 2)
4
1188.18(2)
1763.70(3)
2327.30(3)
74.141(1)
81.102(1)
79.039(1)
4578.5(1)
153(2)
2.281 (CuKa)
15605 (0.0566)
0.0760 (12009)
0.2104
a
ꢀ
ꢀ
a/1
b/1
g/1
V/10ꢀ30 m3
T/K
m/mmꢀ1
Unique rflns (Rint
)
R1 (reflns I 4 2s(I))
wR2 (all data)
CCDC
762758
762760
762762
762761
762759
a
Flack parameter: ꢀ0.007(12).
d(phenyl), 667 m, 623 m, 577 w, 554 w, 534 w, 496 m, 461 m
n(AlC), n(GeC).
(CuKa). The crystals were coated with a perfluoropolyether,
picked up with a glass fiber and immediately mounted in the
cooled nitrogen stream of the diffractometer. The structures
were solved by direct methods and refined with the program
SHELXL-9722 by a full-matrix least-squares method based on
F2. Crystal data, data collection parameters and structure
refinement details are given in Table 1. The molecules of 1
are located on crystallographic twofold rotation axes with the
germanium atoms on the special positions. Compounds 3 and
7 crystallize with two independent molecules. A phenyl group
of 7 was disordered; the atoms were refined on split positions
with site occupation factors of 0.54 and 0.46.
Characterization of
Ph2Ge(CRCPh)[C(Al{CH(SiMe3)2}2)QC(H)Ph] 7
Yield 87%. Mp (argon, sealed capillary): 119 1C. Found C
64.0, H 7.5%. Calcd for C42H59GeAlSi4 C 65.0, H 7.7%. Mass
spectrum (EI, 20 eV, 140 1C; only the most intense masses are
given, the isotopic patterns are in complete agreement with the
calculated ones): m/z (%) = 617 (6) [M ꢀ CH(SiMe3)2]+, 431
(72) [M ꢀ AlR2]+, 353 (25) [PhGe(CCPh)2]+, 329 (26)
[Ph2GeCCPh]+, 252 (36) [PhGe(CCPh)]+, 228 (100)
1
[Ph2Ge]+. H NMR (C6D6): d ꢀ0.22 (s, 2H, AlCH), 0.31 (s,
36H, SiMe3), 6.84 (m, 1H, para-H alkenyl-Ph), 6.94 (m, 2H,
meta-H alkenyl-Ph), 6.99 (m, 3H, meta- and para-H alkynyl-
Ph), 7.05 (m, 2H, para-H Ph2Ge), 7.12 (m, 4H, meta-H
Ph2Ge), 7.58 (m, 2H, ortho-H alkynyl-Ph), 7.67 (m, 2H,
ortho-H alkenyl-Ph), 7.84 (m, 4H, ortho-H Ph2Ge), 8.48
(s, 1H, CHPh). 13C NMR (C6D6, 100 MHz): d 4.8 (SiMe3),
9.9 (AlCH), 93.8 (PhCRCGe), 109.8 (PhCRCGe), 123.9
(ipso-C alkynyl-Ph), 128.3 (meta-C alkenyl-Ph), 128.4 (para-C
alkenyl-Ph), 128.62 (meta-C Ph2Ge), 128.57 (meta-C
alkynyl-Ph), 128.8 (ortho-C alkenyl-Ph), 128.9 (para-C
alkynyl-Ph), 129.2 (para-C Ph2Ge), 132.4 (ortho-C alkynyl-Ph),
134.8 (ortho-C Ph2Ge), 138.9 (ipso-C Ph2Ge), 141.1 (ipso-C
alkenyl-Ph), 154.1 (CQCHPh), 160.6 (CHPh). 29Si NMR
(C6D6, 79.5 MHz): d ꢀ3.0 (SiMe3). IR (Nujol, cmꢀ1):
2160 m n(CRC), 1948 vw, 1875 vw, 1734 vw, 1690 w, 1647
vw, 1597 w, 1572 w, 1553 w, 1485 s n(CQC), phenyl, 1454 vs,
1377 vs (Nujol), 1302 w, 1248 s d(CH3), 1215 w, 1155 w, 1092
m, 1051 w n(CC), 1015 m d(CHSi2), 926 m, 845 vs, 779 w, 754
m r(CH3Si), 733 m (Nujol), 696 m, 675 m d(phenyl), n(SiC),
581 w, 532 w, 496 w, 467 m, 390 w n(AlC), n(GeC).
Acknowledgements
We are grateful to the Deutsche Forschungsgemeinschaft for
generous financial support.
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1636 | New J. Chem., 2010, 34, 1630–1636