Molecular Zinc Species with Ge-Zn and Sn-Zn Bonds: A Reversible Insertion of a Stannylene into a Zinc-Carbon Bond

Article abstract of DOI:10.1021/acs.organomet.6b00344

The tetrylenes Ge(Ar^Me6)₂ and Sn(Ar^Me6)₂ (Ar^Me6 = C₆H₃-2,6-(C₆H₂-2,4,6-(CH₃)₃)₂) reacted with dimethylzinc to afford the insertion products (Ar^Me6)₂Ge(Me)ZnMe (1) and (Ar^Me6)₂Sn(Me)ZnMe (3), which feature Ge-Zn and Sn-Zn bonds as well as two-coordinate zinc atoms. Crystals of 1 were found to be unsuitable for X-ray crystallography, so the ethyl-substituted (Ar^Me6)₂Ge(Et)ZnEt (2) was synthesized in a parallel way to provide crystals suitable for X-ray studies. These showed the structure to be similar to that of 3. The reaction of Pb(Ar^Me6)₂ with dimethylzinc yielded Ar^Me6ZnMe with a linearly coordinated zinc atom via ligand exchange but no characterizable, new lead product was obtained. The reaction of Sn(Ar^Me6)₂ with dimethylzinc is reversible in hydrocarbon solution at room temperature and displayed a dissociation constant K_diss and a ΔG_diss of 0.0028(5) and 14(4) kJ mol^-1 at 298 K, respectively. Compounds 1-4 were characterized by NMR and IR spectroscopy as well as by X-ray crystallography for 1, 3, and 4.

Full text of DOI:10.1021/acs.organomet.6b00344

Article
pubs.acs.org/Organometallics
Molecular Zinc Species with Ge−Zn and Sn−Zn Bonds: A Reversible
Insertion of a Stannylene into a Zinc−Carbon Bond
Jeremy D. Erickson, Ryan D. Riparetti,† James C. Fettinger, and Philip P. Power*
Department of Chemistry, University of California, One Shields Avenue, Davis, California 95616, United States
S
* Supporting Information
ABSTRACT: The tetrylenes Ge(ArMe
)
and Sn(ArMe
)
2
6
6
2
(ArMe = C6H3-2,6-(C6H2-2,4,6-(CH3)3)2) reacted with
6
dimethylzinc to afford the insertion products (ArMe )2Ge-
6
(Me)ZnMe (1) and (ArMe )2Sn(Me)ZnMe (3), which feature
6
Ge−Zn and Sn−Zn bonds as well as two-coordinate zinc
atoms. Crystals of 1 were found to be unsuitable for X-ray
crystallography, so the ethyl-substituted (ArMe )2Ge(Et)ZnEt
6
(2) was synthesized in a parallel way to provide crystals suitable for X-ray studies. These showed the structure to be similar to
Me6
that of 3. The reaction of Pb(ArMe )2 with dimethylzinc yielded Ar ZnMe with a linearly coordinated zinc atom via ligand
6
exchange but no characterizable, new lead product was obtained. The reaction of Sn(ArMe )2 with dimethylzinc is reversible in
6
hydrocarbon solution at room temperature and displayed a dissociation constant Kdiss and a ΔGdiss of 0.0028(5) and 14(4) kJ
mol−1 at 298 K, respectively. Compounds 1−4 were characterized by NMR and IR spectroscopy as well as by X-ray
crystallography for 1, 3, and 4.
reversible addition to ethylene13,14 and Si−X (X = H, Cl)32
INTRODUCTION
■
bonds. The addition of Ge(ArMe )2 to P4 can be reversed upon
6
The tetrylenes of the heavier group 14 elements (:ER2, E = Si,
Ge, Sn, or Pb; R = bulky substituent) have an extensive
chemistry that has been investigated for over four decades.1−4
They are characterized by a singlet ground state in which a
nonbonded electron pair occupies one of the two valence
orbitals and which may function as an electron pair donor. The
existence of an adjacent unoccupied p-orbital allows the
tetrylenes to behave as donor−acceptor molecules in a
synergistic manner, and this has enabled their facile reactions
with small molecules such as H2,5−8 NH3,8−11 CO,12 and
C2H4.13,14 The insertion chemistry of group 14 metalylenes has
also been especially well documented through reactions with
the aforementioned small molecules as well as with organo-
halides,15−17 transition metal halides,18 H2O,19−24 MeOH,21,25
N2H4,26 the group 13 alkyls AlMe3 and GaR3 (R = Me, Et),27
and white phosphorus P4.28 These insertions have proven
useful for the synthesis of uncommon bond types in molecular
species, such as Ge−Al, Sn−Al, and Sn−Ga bonds.
exposure to UV radiation,28 and a cationic tungsten−metal-
logermylene has been found to reversibly insert into H−H, Si−
5
H, and B−H bonds. Also, the insertion of Sn(ArMe )2 into the
6
Ga−C bond in GaR3 (R = Me, Et) was shown recently to be
fully reversible under ambient conditions.27
The latter discovery led us to investigate insertion reactions
into other metal−carbon bonded species. Herein, we
demonstrate that the group 14 metalylenes E(ArMe )2 (E =
6
Ge, Sn) react with ZnMe2 to form (ArMe )2E(Me)ZnMe in
6
good yield (Scheme 1), with the formation of the tin insertion
Scheme 1. Insertion of Group 14 Tetrylenes into
Dimethylzinc to Form 1 and 3
The ability of tetrylenes to undergo reversible insertions is of
particular interest, as it suggests such compounds may be of use
in catalytic cycles.13 While some germanium(II) and tin(II)
hydrides have been found to catalyze hydroborations of ketones
and aldehydes,29 a catalytic cycle involving a diorganotetrylene
as a redox-active species is unknown. The greater stability of
diorganostannylenes in contrast to the divalent hydrido
derivatives makes them an important target for group 14
catalysis.
product (3) being reversible at room temperature. In addition,
(ArMe )2Ge(Et)ZnEt (2) was synthesized in order to obtain a
6
Ge−Zn bonded species that was suitable for structural studies
by X-ray crystallography.
The plumbylene Pb(ArMe
) did not afford an insertion
2
6
product with ZnMe2, but instead undergoes ligand ex-
Currently, the scope of reversible tetrylene insertion/
additions is limited to a handful of examples. The silylenes
30
31
Si(SArMe
)
2
and Si(SAriPr
)
2
(AriPr = C6H3-2,6-(C6H2-2,6-
6
4
4
Received: April 27, 2016
(CH(CH3)2)2)2) and some phosphonium silylides have shown
© XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.6b00344
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Article
change27,33 to give ArMe ZnMe in moderate yield with no
isolable lead product (Scheme 2).
Reaction of ZnMe2 with Pb(ArMe
) yielded a colorless
2
6
6
solution along with an intractable black precipitate. Filtration
and crystallization produced a colorless solid that was found to
be ArMe ZnMe, 4. No lead-containing products were character-
6
Scheme 2. Reaction of Pb(ArMe )2 and ZnMe2 to Afford 4
6
izable. After 1 week of storage, 4 assumed a dark color due to
its decomposition to metallic zinc and ArMe H.
6
Structures. Structurally characterized Zn−Ge bonds fall
into two classes: those in Zintl clusters37−42,44 and those in
organozinc germanes incorporating tetravalent germa-
nium.46−49 The latter largely exist as dimers with bridging
halides,46,48 solvent adducts,48,49 or, in one case, an oxygen−
zinc cubane-like structure.49 Only one zinc-germyl species,
Zn{Ge(SiMe3)3}2,46,47 with a two-coordinate zinc atom has
been structurally characterized. A single crystal of 1 could not
be obtained for structural analysis, but the closely related ethyl-
substituted 2 was obtained through a very similar synthetic
route using diethylzinc, and its structure was determined
crystallographically.
RESULTS AND DISCUSSION
■
Reactions of E(ArMe
)
(E = Ge, Sn, and Pb) with
6
2
ZnMe2. The reactions of Ge(ArMe )2 or Sn(Ar )2 with ZnMe2
afforded products 1 and 3 as colorless microcrystals in
moderate yield. Although sufficiently large crystals of 3 were
easily grown and their structures determined crystallographi-
cally, a single crystal of 1 suitable for X-ray crystallography
Me6
6
could not be obtained. However, the analogous reaction of
Ge(ArMe
)
with ZnEt2 was carried out under identical
2
6
6
conditions to produce (ArMe )2Ge(Et)ZnEt (2) as colorless
crystals, which were sufficiently large for X-ray diffraction
studies (Figure 1).
The structure of 2 is shown in Figure 1 and establishes that it
is the product of a simple insertion of the germylene into a Zn−
C bond of diethylzinc while maintaining the two coordination
of the zinc atom that is bonded to an ethyl group as well as to a
germanium atom of a −Ge(Et)(ArMe )2 moiety. The structure
6
has a disorder in which the ethyl group at zinc occupies two
positions. The Ge−Zn−C angles are 159.6(6)° and 168.0(13)°.
The deviation from a 180° angle at zinc appears to be due to an
interaction of the zinc atom with a flanking aryl ring. The
structure features a 3.060 Å distance between zinc and the
centroid of the flanking ring plane. The terphenyl ligands
provide steric bulk, which shields the compound against
association. The Zn−C distances to the disordered ethyl
carbons C3 and C3B are essentially identical at 1.998(9) and
1.998(11) Å, which is slightly longer than the range of
published two-coordinate dialkylzinc compounds (range
1.930−1.982).50−54 The Ge−Zn bond length of 2.3839(11)
Å is similar to the sum of the single-bond covalent radii of
germanium (1.22 Å) and zinc (1.18 Å)55 and is close to that in
the homoleptic bis-germyl species Zn{Ge(SiMe3)3}2 (2.382
Å),46,47 which is the only previously structurally characterized
compound with a Ge−Zn bond in which the zinc atom is two-
coordinate.
Figure 1. Thermal ellipsoid plot (30% probability) of (ArMe )2Ge-
6
(Et)ZnEt (2). Hydrogen and a disordered 41% occupied zinc-ethyl
group are not shown for clarity. Selected distances (Å) and angles
(deg): Ge1−Zn1 2.3839(11), Zn1−C3 1.998(9), Zn1−C3B
1.998(11), Ge1−C1 1.991(5), Ge1−C5 2.022(5), Ge1−C29
2.022(5), Ge1−Zn1−C3 159.6(6), Ge1−Zn1−C3B 168.0(13), C5−
Ge1−C29 114.0(2).
The structure of 3 is illustrated in Figure 2, and selected
distances and angles are given in the figure legend. The zinc
While molecular species containing Zn−Ge and Zn−Sn
bonds have been known for a number of years,34,35 the
structures of only a few of these compounds have been
determined. Moreover, the majority of the known structurally
characterized species are either clusters, ionic salts, or Zintl
phases.36−42 The insertion of germylenes and stannylenes into
Zn−C bonds represents a new route to the formation of Ge−
Zn and Sn−Zn bonded compounds that previously required
synthetic approaches that used either salt or organic
metatheses.34,35,43−48
Attempts to redissolve the colorless crystals of 3 in hexane at
room temperature resulted in the reappearance of the violet
color of the stannylene precursor. The solution’s violet color
intensified with further warming but faded upon cooling,
suggesting a reversible equilibrium between the reactants
Me6
Sn(ArMe )2 and ZnMe2 and the product (Ar )2Sn(Me)ZnMe.
6
Figure 2. Thermal ellipsoid plot (50% probability) of (ArMe )2Sn-
6
The characterization of this equilibrium is discussed below. In
the solid state, transformation of 3 to the starting materials
Sn(ArMe6)2 and ZnMe2 occurred slowly so that a change from
colorless to pale violet was observed only over several weeks.
(Me)ZnMe (3). Hydrogens are not shown for clarity. Selected
distances (Å) and angles (deg): Sn1−Zn1 2.5529(6), Zn1−C2
1.950(4), Sn1−C1 2.154(3), Sn1−C3 2.207(3), Sn1−C27 2.216(3),
Sn1−Zn1−C2 167.92(14).
B
DOI: 10.1021/acs.organomet.6b00344
Organometallics XXXX, XXX, XXX−XXX

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Article
atom is two-coordinate and is bonded to a methyl group and to
a tin atom. The coordination of zinc deviates ca. 12° from
linearity, and there is a relatively close approach between the
centroid of the flanking aryl ring nearest to zinc of 2.982 Å. The
Zn−Me distance in 3 is 1.950(4) Å and is slightly longer than
the Zn−Me distance in dimethylzinc, 1.927(6) Å,56 but well
within the range of previously published dialkylzinc compounds
(range 1.930−1.982 Å).50−54
descend to a low enough temperature to resolve the aromatic
signals. Both metal-methyl substituents are observed upfield at
−0.32 and −0.65 ppm for Sn-Me and Zn-Me, respectively.
Their respective metal-methyl signals are observed at 0.10 and
−4.54 ppm in the 13C NMR spectrum. The 119Sn NMR
spectrum of 3 displays a signal with an upfield chemical shift at
−155 ppm, which is near the chemical shifts of the 119Sn NMR
signals observed for the group 13 derivatives (ArMe )2Sn(Me)-
6
27
GaMe2 and (ArMe )2Sn(Et)GaEt2 (−170 and −146 ppm).
6
The Sn−Zn bond lengths in 3 of 2.5524(7) and 2.5529(7) Å
are very similar to the sum of the single-bond covalent radii of
tin (1.40 Å) and zinc (1.18 Å).57 No species with a Sn−Zn
bond in which the zinc is two-coordinate has been structurally
characterized, so a direct comparison is impossible. However,
the Sn−Zn bond lengths in both molecules of the asymmetric
unit in 3 are shorter than the Sn−Zn bond lengths in Sn−Zn
bond containing clusters (range 2.78−2.99 Å)38,39,42 or
coordination compounds (range 2.578−2.679 Å).45,58,59
This is due to similar coordination of the tin atom60 and the
similar electronegativity values of Ga (1.6) and Zn (1.8).61
Upon dissolving crystals of 3, a pale violet color slowly
appears over several hours due to the establishment of an
equilibrium between 3 and Sn(ArMe )2 and ZnMe2 at room
6
temperature. The violet color fades to colorless upon cooling
below room temperature (Scheme 3). Repeated cycles of
The reaction of Pb(ArMe )2 with ZnMe2 produced 4 (Figure
6
Scheme 3. Room-Temperature Dissociation of 3 in
Hydrocarbon Solution
3) via ligand exchange. The zinc atom is linearly coordinated
dissolving the solid in hexanes and removing the solvent under
reduced pressure eventually yielded a violet solid (a result of
gradual ZnMe2 removal) that was identified by NMR
spectroscopy to be the stannylene Sn(ArMe )2.
6
The reaction equilibrium parameters were determined by
1
variable-temperature H NMR spectroscopy (see SI), and it
Figure 3. Thermal ellipsoid plot (50% probability) of ArMe ZnMe (4).
6
was found that the reaction has a Kdiss and ΔGdiss of 0.0028(5)
and 14(4) kJ mol−1 at 298 K. This equilibrium is precedented
Hydrogens are not shown for clarity. Selected distances (Å) and angles
(deg): Zn1−C1 1.941(8), Zn1−C2 1.925(7), C1−Zn1−C2 180.0.
only by the reversible insertion of Sn(ArMe )2 into GaMe3 and
6
GaEt3,27 which were the first reported reversible insertions of a
diarylstannylene into a metal−carbon bond and displayed
similar values of a Kdiss of 8.09(6) × 10−3 and ΔGdiss of 11.8(9)
kJ mol−1 at 296 K.
with an angle of 180.0°, and the Zn−C bond lengths are
1.941(8) and 1.925(7) Å for the methyl and aryl groups,
respectively, and fall within the range of previously published
dialkylzinc molecules (range 1.930−1.982 Å).50−54
The 1H NMR chemical shift of the zinc-methyl group of 4 is
observed upfield at −0.89, and the 13C NMR chemical shift of
the same moiety is at −10.51 ppm.
Spectroscopy. At 65 °C the 1H NMR spectrum of 1 shows
two metal-methyl signals assignable to Zn-Me and Ge-Me.
There are also two mesityl-methyl signals and two aromatic
proton signals. At −53 °C, however, 11 mesityl-methyl signals
are observed as the rotation of the flanking mesityl rings is
slowed (see SI). At this temperature, the aromatic signals also
devolve into ca. 5 multiplets that could not be resolved within
the temperature limits of the instrument. The signals of the Zn-
Me and Ge-Me groups were observed at −0.72 and 0.00 ppm,
respectively, and displayed no change in shape over this
temperature range, suggesting that no intermolecular inter-
action occurs within this range.
CONCLUSIONS
■
Me6
The germylene Ge(ArMe )2, the stannylene Sn(Ar )2, and the
6
plumbylene Pb(ArMe
) were shown to react readily with
6
2
ZnMe2. The germylene and stannylene inserted into a Zn−C
bond to form tetravalent group 14 centers as well as a two-
coordinate zinc atom, providing a novel synthesis for Ge−Zn
and Sn−Zn bonded species. The insertion of Sn(ArMe )2 into a
6
zinc−carbon bond of ZnMe2 was found to be reversible at
room temperature, with a dissociation constant Kdiss and a
ΔGdiss of 0.0028(5) and 14(4) kJ mol−1 at 298 K, respectively.
1
In the H NMR spectrum of 2 the rotation of the ligands is
In contrast, the reaction of Pb(ArMe )2 with ZnMe2 did not
6
sufficiently slow at room temperature such that all terphenyl
proton signals resolve separately and the diastereotopic
character of the CH2 moieties of the ethyl groups is observable.
These diastereotopic proton signals are multiplets that appear
at −0.14, 0.10, 0.62, and 0.87 ppm. The signals of the 13C NMR
spectrum are likewise magnetically nonequivalent such that 27
aromatic 13C signals are observed, and all 16 signals of the
nonaromatic carbon atoms are observed upfield (see SI).
produce a Pb−Zn bonded species, but instead underwent
ligand exchange to produce the alkylaryl complex ArMe ZnMe.
6
EXPERIMENTAL SECTION
■
General Considerations. All products were formed in strictly
anhydrous and anaerobic conditions by use of modified Schlenk
techniques. All solvents were initially dried using a Grubbs-style
solvent purification system62 and further dried over NaK. Ge(ArMe )2,
6
1
The H NMR spectrum of 3 exhibits a smaller barrier to
Me6
Sn(ArMe )2, and Pb(Ar )2 were synthesized according to literature
6
methods.63 Dimethylzinc was purchased neat from Strem and used as
received. All NMR spectroscopy was carried out on a Bruker 500 MHz
spectrometer. 119Sn NMR was referenced to SnBu4 (−11.7 ppm).
Infrared spectroscopy was collected as a Nujol mull using a Bruker
ligand rotation than 1 so that at room temperature only three
methyl signals of the mesityl groups are observed, one triplet
signal for the para-C6H3 proton, and a multiplet for the
remaining 12 aryl protons. Our instrument lacked the range to
C
DOI: 10.1021/acs.organomet.6b00344
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Tensor 27 IR spectrometer. Melting points were measured using a
Mel-Temp II apparatus using capillary tubes sealed under a nitrogen
atmosphere. The purity of the compounds was established via their 1H
and 13C NMR spectra for all compounds and in addition by 119Sn
product was extracted into hexanes and reduced in volume under
reduced pressure to ca. 15 mL. Cooling to −30 °C produced 3 as
1
colorless crystals. Yield: 0.122 g, 86%. Mp: 158−161 °C. H NMR
(500 MHz, C6D6, 25 °C, ppm): −0.89 (s, 3H, ZnMe), 2.16 (s, 6H, p-
Me), 2.17 (s, 12H, o-Me), 6.87 (s, 4H, p-C6H2), 7.08 (d, JHH = 7.5 Hz,
2H, m-C6H3), 7.32 (t, JHH = 7.5 Hz, 1H, p-C6H3). 13C{1H} NMR (125
MHz, C6D6, 25 °C, ppm): −10.51 (ZnMe), 21.15 (p-Me), 21.35 (o-
Me), 126.02, 128.97, 135.60, 136.60, 143.00, 149.62, 156.02. IR
(cm−1): 2920 (s), 2860 (s), 2650 (m), 1600 (w), 1505 (s), 1340 (s),
1255 (s), 1175 (s), 1010, (s), 850 (w), 800 (s), 720 (m).
NMR spectroscopy for 3 (see SI).
Me6
(ArMe )2Ge(Me)ZnMe (1). Ge(Ar )2 (0.501 g, 0.717 mmol) was
6
dissolved in pentane (35 mL) and cooled using a liquid N2−ethanol
bath to ca. −116 °C. To this solution was added ZnMe2 (73.46 μL,
0.717 mmol) predissolved in pentane (10 mL) over the course of 30
min. Upon completion of addition, the still-violet solution was allowed
to warm to room temperature overnight with continued stirring. This
resulted in a colorless solution, whose volume was reduced to ca. 10
mL under reduced pressure and stored at ambient temperature. Over 2
weeks, white microcrystals of 1 were precipitated. Yield: 0.364 g,
X-ray Crystallographic Data Collection. Crystals were removed
from Schlenk flasks under a positive N2 stream and immediately
immersed in Paratone oil. Single crystals were selected and placed on a
plastic loop filament pin and placed on the diffractor under a cold N2
stream (90 K). All crystallographic calculations were performed on an
eight-core Intel Xeon E5-1620v2 at 3.70 GHz with 16 GB of extended
memory. Data collected were corrected for Lorentz and polarization
effects with Saint64 and absorption using Blessing’s method and
merged as incorporated with the program SADABS.65,66 The
SHELXTL67 program package was implemented to determine the
probable space group and set up the initial files. The structure was
determined by direct methods with a majority of the non-hydrogen
atoms being located directly using the program XT.68 The structure
was refined with XL.66
1
63.8%. Mp: 166 °C (dec). H NMR (500 MHz, C6D6, 65 °C, ppm):
−0.77 (s, 3H, ZnMe), −0.02 (s, 2H, GeMe), 1.86 (s, 24H, o-Me), 2.20
(s, 12H, p-Me), 6.73 (m, 12H, p-C6H2, m-C6H3), 7.06 (t, 2H, p-
C6H3). 13C{1H} NMR (125 MHz, PhMe-d8, −53 °C, ppm): −3.04
(ZnMe), 2.22 (GeMe), 21.41, 21.64, 22.23, 22.97, 23.40, 23.64,
129.65, 129.95, 130.33, 130.88, 131.20, 131.50, 135.08, 135.89, 136.36,
136.66, 137.28, 139.16, 142.09, 142.57, 142.90, 144.09, 145.28, 146.34,
148.30, 148.87, 150.50, 151.31. IR (cm−1): 2920 (br), 2850 (s), 1610
(w), 1455 (m), 1370 (m), 1255 (w), 1050 (br), 845 (w), 800 (m), 720
(m), 530 (w), 350 (w).
Me6
(ArMe )2Ge(Et)ZnEt (2). Ge(Ar )2 (0.388 g, 0.554 mmol) was
6
dissolved in pentane (35 mL) and cooled using a liquid N2−ethanol
bath to ca. −116 °C. To this solution was added ZnEt2 (58.0 μL, 0.567
mmol) predissolved in pentane (10 mL) over 30 min. Upon
completion of addition, the still-violet solution was allowed to warm
to room temperature overnight with continued stirring, which
produced a colorless solution. This solution was filtered and reduced
in volume under reduced pressure to 5 mL and stored at −30 °C for 4
weeks to afford colorless crystals of 2. Yield: 0.287 g, 73%. Mp: 168 °C
(dec). 1H NMR (500 MHz, C6D6, 65 °C, ppm): −0.14 (m, 1H,
ZnCH2CH3), 0.10 (m, 1H, ZnCH2CH3), 0.62 (m, 1H, GeCH2CH3),
0.87 (t, 3H, GeCH2CH3), 0.90 (s, 3H, PhCH3), 1.19 (m, 1H,
GeCH2CH3), 1.30 (t, 3H, GeCH2CH3), 1.44 (s, 3H, PhCH3), 1.65 (s,
3H, PhCH3), 1.75 (s, 3H, PhCH3), 1.92 (m, 9H, PhCH3), 2.13 (m,
6H, PhCH3), 2.21 (s, 3H, PhCH3), 2.26 (s, 3H, PhCH3), 6.57 (d, 1H,
PhH), 6.71 (m, 8H, PhH), 6.80 (d, 2H, PhH), 6.86 (d, 1H, PhH), 7.03
(m, 2H, PhH). 13C{1H} NMR (125 MHz, C6D6, −53 °C, ppm):
10.61, 11.33, 11.49, 14.29, 16.27, 20.95, 21.10, 21.66, 22.03, 22.16,
22.74, 22.90, 23.02, 23.72, 23.85, 34.46, 128.78, 129.57, 129.93,
130.30, 130.79, 131.14, 131.38, 131.57, 134.50, 135.97, 136.28, 136.48,
136.63, 136.85, 137.48, 137.75, 138.86, 142.53, 142.99, 143.60, 144.09,
145.42, 147.62, 148.48, 149.20, 150.58, 150.83. IR (cm−1): 2920 (s),
2860 (s), 2675 (m), 1660 (w), 1610 (w), 1460 (m), 1375 (m), 1100
(br), 950 (w), 850 (w), 800 (m), 730 (m), 650 (w), 475 (w), 375 (w).
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.6b00344.
■
S
Variable-temperature 1H NMR spectra of 3, data used in
van’t Hoff analysis of the equilibrium of 3, infrared and
NMR spectra for 1−4 (PDF)
Crystallographic information files for 2−4 (CIF)
AUTHOR INFORMATION
Corresponding Author
*E-mail: pppower@ucdavis.edu.
■
Present Address
†Department of Chemistry, University of Texas at Austin, 105
E. 24th Street, Austin, Texas 78712, United States.
Notes
The authors declare no competing financial interest.
Me6
(ArMe )2Sn(Me)ZnMe (3). Sn(Ar
) (0.373 g, 0.5 mmol) was
6
ACKNOWLEDGMENTS
2
■
dissolved in pentane (35 mL) and cooled to ca. −116 °C. To this
solution was added dropwise ZnMe2 (53.8 μL, 0.525 mmol) dissolved
in pentane (15 mL). After warming to room temperature over 2 h, the
solution had changed from violet to colorless. The solution was filtered
and reduced in volume under reduced pressure to ca. 10 mL, resulting
in the formation of colorless crystals. Yield: 0.247 g, 58.3%. Mp: white
solid becomes violet at temperatures > ca. 80 °C and melts to an
We are grateful to the U.S. Department of Energy, Office of
Basic Energy Sciences (FG02-07ER46475), for support of this
work. We thank the National Science Foundation (Grant
1531193) for the Dual Source X-ray diffractometer.
REFERENCES
■
1
opaque violet liquid at 102 °C. H NMR (500 MHz, C6D6, 25 °C,
(1) Mizuhata, Y.; Sasamori, T.; Tokitoh, N. Chem. Rev. 2009, 109,
3479.
(2) Davidson, P. J.; Lappert, M. F. J. Chem. Soc., Chem. Commun.
ppm): −0.64 (t, JZnH = 16.8 Hz, 3H, ZnMe), −0.32 (t, JSnH = 40.21,
3H, SnMe) 1.89 (s, 12H, o-Me), 1.91 (s, 12H, o-Me), 2.21 (s, 12H, p-
Me), 6.74 (m, 12H, p-C6H2 and m-C6H3), 7.08 (t, JHH = 7.5 Hz, 2H,
p-C6H3). 13C{1H} NMR (125 MHz, C6D6, 25 °C, ppm): −4.54
(ZnMe), 0.10 (SnMe), 21.12 (p-Me), 22.69 (o-Me), 22.74 (o-Me),
129.47, 129.56, 129.71, 136.41, 136.49, 136.72, 143.49, 146.88, 150.79.
119Sn {1H} NMR (186.36 MHz, C6D6, 25 °C): −155 ppm. IR (cm−1):
1973, 317a.
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2920 (s), 1460 (m), 1370 (w), 1255 (w), 1050 (br), 800 (m).
Me6
(ArMe )ZnMe (4). Pb(Ar )2 (0.417 g, 0.5 mmol) was dissolved in
6
toluene (35 mL) and cooled to −78 °C. To this solution was added
ZnMe2, dissolved in toluene (15 mL), dropwise over the course of 25
min. The solution slowly warmed to room temperature overnight,
resulting in a cloudy violet mixture and a black precipitate. The
D
DOI: 10.1021/acs.organomet.6b00344
Organometallics XXXX, XXX, XXX−XXX

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DOI: 10.1021/acs.organomet.6b00344
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