The addition of nitriles to tetramesityldisilene: A comparison of the reactivity between surface and molecular disilenes

Article abstract of DOI:10.1002/chem.201405780

The addition of acetonitrile, propionitrile, and phenylacetonitrile to tetramesityldisilene (Mes₂Si=SiMes₂) was examined. In general, 1,2,3-azadisiletines and the tautomeric enamines were formed, although a ketenimine was formed as the major product in the addition of phenylacetonitrile to the disilene. In the presence of LiCl, the mode of addition changed for both acetonitrile and propionitrile: insertion into the α-CH bond of acetonitrile and/or formation of the formal HCN adduct was observed. Preliminary investigations of the reactivity of the nitrile adducts are also reported. A comparison between the reactivity of nitriles with Mes₂Si=SiMes₂ and the Si(100)-2 x 1 surface was made both in terms of the types of adducts formed and their reactivity. Some insights into the surface chemistry are offered.

Full text of DOI:10.1002/chem.201405780

DOI: 10.1002/chem.201405780
Full Paper
&
Disilenes
The Addition of Nitriles to Tetramesityldisilene: A Comparison of
the Reactivity between Surface and Molecular Disilenes
[a]
Julie A. Hardwick and Kim M. Baines*
Dedicated to Prof. Dr. Matthias Driess, Prof. Dr. Martin Oestreich, and Dr. Richard Weidner for their superb organization of the 17th In-
ternational Symposium on Silicon Chemistry and the 7th European Silicon Days
Abstract: The addition of acetonitrile, propionitrile, and
phenylacetonitrile to tetramesityldisilene (Mes Si=SiMes )
sertion into the a-CH bond of acetonitrile and/or formation
of the formal HCN adduct was observed. Preliminary investi-
gations of the reactivity of the nitrile adducts are also report-
ed. A comparison between the reactivity of nitriles with
Mes Si=SiMes and the Si(100)-2ꢀ1 surface was made both
2
2
was examined. In general, 1,2,3-azadisiletines and the tauto-
meric enamines were formed, although a ketenimine was
formed as the major product in the addition of phenylaceto-
nitrile to the disilene. In the presence of LiCl, the mode of
addition changed for both acetonitrile and propionitrile: in-
2
2
in terms of the types of adducts formed and their reactivity.
Some insights into the surface chemistry are offered.
Introduction
The attachment of organic molecules to semiconductor
surfaces has been extensively investigated over the past two
[
1]
decades. With potential applications in the area of bio-
[
1b]
sensors, the addition of nitriles to the Si(100)-2ꢀ1 surface is
of particular interest. If the nitrile group remains intact after re-
action with the surface, the nitrile group may be subsequently
hydrolyzed to a carboxylic acid or reduced to a terminal amine
and biologically active molecules, such as peptides or proteins,
could then be bound as a second layer. If, on the other hand,
the nitrile moiety reacts directly with the surface, different sur-
face reactivity can be expected demonstrating the need to
have a clear understanding of the structure of the organic
group present on the surface.
Figure 1. Acetonitrile adducts formed on the Si(100)-2ꢀ1 surface
[2,5,7–10]
[3,5,6]
cal
and experimental
evidence supports the forma-
tion of three types of nitrile adducts in equal amounts on the
Si surface at room temperature: an a-CH insertion adduct (1),
a cycloadduct involving the CꢀN bond (2a,b), and a twisted
ketenimine product (3a,b) (Figure 1). Despite many studies of
this reaction, only 1 has been identified unambiguously. The
presence of distinct adducts (2 and 3) with C=N and C=C=N
moieties on the surface have been confirmed; however, only
the functional group and the orientation of the p system rela-
tive to the Si dimer axis are known. The exact structures of 2
and 3 have not been established due to the limitations of the
experimental techniques employed.
The addition of acetonitrile to the Si(100)-2ꢀ1 surface was
[
2]
first reported by Xu in 2001. Since the initial study, the
addition of acetonitrile to the Si(100)-2ꢀ1 surface has been ex-
amined at various temperatures, including room temperature,
and the adducts have been identified using a variety of tech-
niques, including temperature-programmed desorption
[
2]
(
(
(
TPD), high-resolution electron energy loss spectroscopy
[
2]
HREELS), conventional X-ray photoelectron spectroscopy
[
2,3]
[4,5]
XPS),
synchrotron radiation XPS,
near-edge X-ray ab-
resonant Auger electron
spectroscopy (RAES), and multiple internal reflection Fourier
[
4,5]
sorption fine structures (NEXAFS),
[
6]
In contrast to surface adducts, the structures of molecular
compounds can be identified unambiguously by using experi-
mental techniques that are not available to surface scientists,
such as NMR spectroscopy and X-ray crystallography. Addition-
ally, molecular compounds and surface adducts can be charac-
terized by FTIR spectroscopy, which allows for a comparison
between the data sets. Furthermore, the reactivity of molecular
compounds can be examined more easily than the reactivity of
[
3]
transform infrared (MIR-FTIR) spectroscopy. Current theoreti-
[a] Dr. J. A. Hardwick, Prof. K. M. Baines
Department of Chemistry, University of Western Ontario
London, Ontario, N6A 5B7 (Canada)
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201405780.
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surface adducts, especially when the surface layer contains
several reactive functionalities.
The formation of 1,2,3-azadisiletines 5 and 6 can be under-
stood in terms of a formal [2+2] cycloaddition between the
CꢀN bond of the nitrile and the Si=Si bond of 4. Enamines 7
and 8 likely form as a result of tautomerization of the initial
1,2,3-azadisiletines. The addition of aceto- and propionitrile to
disilene 4 likely begins with coordination of a donor molecule
(D=THF or a molecule of nitrile) to 4 to give a complex
(Scheme 3). Although THF or nitrile complexes of 4 have not
Mes Si=SiMes (4) is a reasonable model for the Si(100)-2ꢀ1
2
2
[
11]
surface, as it has been demonstrated that 4 is comparable in
[
12]
reactivity to the Si surface.
For example, disilene 4 and
Si(100)-2ꢀ1 surface dimers exhibit the same reactivity towards
[
1d,g–k,13,14]
alkynes.
Surprisingly, the reactivity of disilenes to-
[15–18]
wards nitriles has not yet been thoroughly examined;
in
fact, there are no reports of the direct addition of acetonitrile,
or any nitrile with a-hydrogen atoms on a saturated carbon
atom, to disilenes. Herein, we examine the addition of aceto-
nitrile to tetramesityldisilene, 4, in order to compare the
structures of the molecular adducts with the structures of the
acetonitrile adducts formed on the Si(100)-2ꢀ1 surface and to
provide further insight into the structures present on the
surface. The reactivity of propionitrile and phenylacetonitrile
towards disilene 4 was also studied to investigate reactivity
trends.
Scheme 3. Proposed mechanism for the formation of the 1,2,3-azadisiletines
and tautomers
Results and Discussion
No reaction was observed upon the addition of excess CH CN
3
(
or CH CH CN) to disilene 4 in THF at room temperature, and
been observed, water and alcohols are known to coordinate to
3
2
[19]
thus, the reaction mixtures were heated in a sealed tube to
008C. The 1,2,3-azadisiletine 5 (or 6) was the initially formed
4
and a weak interaction between a donor molecule and 4
1
may be sufficient to polarize the Si=Si bond. Furthermore,
complexation between the nitrilic nitrogen of acrylonitrile and
the silicon dimer on the Si(100)-2ꢀ1 surface has been pro-
product; however, over time and/or upon handling or expo-
sure to the ambient atmosphere, the enamine tautomer, 7 (or
8
[20]
), appears to form at the expense of the imine (Scheme 1).
posed to occur, and adducts between stronger donors such
[21]
In contrast, the addition of excess PhCH CN to disilene 4 in
as NHCs or isonitriles have recently been reported.
After
2
THF at room temperature gave a mixture of 9 and 10 in a ratio
of about 5:1 (Scheme 2). Compound 9 hydrolyzed slowly to 11
upon exposure to the ambient atmosphere; however, upon
the addition of acid (1/2 drop of 1m HCl) or upon attempted
purification by chromatography, 9 rapidly hydrolyzed to 11.
Compound 10 also decomposed to an unidentified compound
under these conditions.
coordination of the donor molecule to the disilene, the basic
portion of the complex may attack the nitrilic carbon to give
a zwitterionic intermediate. The intermediate may then under-
go intramolecular nucleophilic attack at the silicon atom
bound to D, displacing the donor molecule and forming the
azadisiletine. Tautomerization gives the enamine.
In contrast, the formation of a ketenimine (9) was observed
in the addition of phenylacetonitrile to disilene 4 in addition
to an enamine analogous in structure to 7 (and 8). Again, the
reaction likely begins with coordination of a donor molecule
(
D=THF or phenylacetonitrile) to the disilene (Scheme 4).
However, in this case, formation of the ketenimine, either intra-
molecularly (not shown) or intermolecularly, appears to be
competitive with cyclization perhaps because of the increased
acidity of the a-hydrogen atoms in phenylacetonitrile. Further-
more, the cycloadduct, 1,2,3-azadisiletine 12, apparently under-
goes rapid tautomerization to give enamine 10, as it was not
observed as a product. The rate of tautomerization of 12 to 10
appears to be faster than the rearrangement of 5 to 7 (or of 6
to 8) most likely because of the increased acidity of the benzyl-
ic hydrogen atoms. Of the reactions examined in this study,
the addition of phenylacetonitrile to the disilene is the only
example in which two distinct types of nitrile adducts are
formed.
3 3 2
Scheme 1. Addition of CH CN and CH CH CN to disilene 4
The rate of addition of a variety of nitriles to bis[bis(trime-
thylsilyl)methyl]germylene ([(Me Si) CH] Ge:) in THF at room
3
2
2
Scheme 2. Addition of PhCH
2
CN to disilene 4
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Scheme 4. Proposed mechanism for the formation of compounds 9, 10 and
1
2
Figure 2. Molecular structure of 13 (50% probability level). All hydrogen
atoms, with the exception of the Si-H, are omitted for clarity. Selected bond
lengths (ꢂ) and angles (8): Si1ÀC11=1.908(2), Si1ÀC1=1.910(2), Si1À
C40=1.938(2), Si1ÀSi2=2.3866(8), Si2ÀC21=1.898(2), Si2ÀC31=1.900(2),
C40ÀC41=1.454(3), C41ÀN42=1.144(3), C11-Si1-C1=111.01(9), C11-Si1-
C40=104.61(10), C1-Si1-C40=108.02(10), C1-Si1-Si2=102.50(7), C11-Si1-
Si2=119.78(7), C21-Si2-C31=111.38(8), C21-Si2-Si1=124.22(7), C31-Si2-
Si1=106.91(6), C41-C40-Si1=116.1(2), N42-C41-C40=179.0(3).
the generation of silylenes from a disilene (ArBrSi=SiBrAr, in
which
Ar=2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimethyl-
3
Scheme 5. Addition of CH CN to disilene 4 in the presence of LiCl
[24]
silyl)methyl]phenyl) and alters the product of thermolysis
giving precedent to our observations.
[
22]
+
amounts of salts, such as LiCl, and, therefore, LiCl was added
LiCl forms a complex with acetonitrile, in which a Li ion is
coordinated to the nitrile group of four acetonitrile molecules
to the reaction mixture containing acetonitrile and disilene 4.
The addition of excess CH CN to disilene 4 dissolved in THF in
the presence of a catalytic amount of LiCl gave a mixture of 13
and 14 in a ratio of about 9:1 at room temperature
Scheme 5). The addition of propionitrile to 4 was attempted
[25]
in a tetrahedral arrangement. It is plausible that complexa-
tion enhances the acidity of the acetonitrile. We postulate the
following mechanism for the formation of 13. After initial
3
[26]
(
coordination of a donor (THF, the nitrile or chloride ) to the
under the same reaction conditions; however, 14 was the only
nitrile addition product isolated. The structure of 14 was
verified by independent synthesis by the addition of KCN to
disilene 4 in THF at room temperature followed by subsequent
exposure to atmospheric moisture.
disilene, abstraction of an a-H from a coordinated CH CN
3
+
would produce the CH CN anion (coordinated to Li ), which
2
can rebound, displacing the donor on silicon (Scheme 6). Ac-
The molecular structure of 13 was determined unambigu-
ously by X-ray crystallography (Figure 2). The SiÀSi bond
length of 2.3866(8) ꢂ is longer than the typical SiÀSi single
[
23]
bond length of 2.34 ꢂ and the Si(1)ÀC40 bond length of
1
.938(2) ꢂ is longer than the typical SiÀC single bond length of
[
23]
1
.87 ꢂ. The elongated SiÀSi and SiÀCH bonds are undoubt-
2
edly due to the presence of four bulky mesityl substituents. All
other bond lengths and angles fall within normal ranges.
The addition of LiCl alters the mode of addition of nitriles to
4
from cycloaddition to a-CH insertion. Notably, CH insertion
adducts were also obtained in the addition of nitriles to
[
22]
[
(Me Si) CH] Ge: in the presence of LiCl. However, in contrast,
3 2 2
the same reactions proceeded at room temperature in the
[
22]
absence of salt, albeit at a much slower rate. There is one
report in the literature in which a lithium halide (LiBr) assists in
Scheme 6. Proposed mechanism for the formation of 13
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cordingly, the addition of CD CN to disilene 4 in THF in the
13 and 15 are identical in length. However, the SiÀCH bond
3
2
presence of LiCl produced Mes Si(CD CN)Si(D)Mes (13’),
length of 13 (1.938(2) ꢂ) is slightly longer than the two SiÀCH
bond lengths of 1.929(2) and 1.917(2) ꢂ in 15 likely because of
steric crowding. In 15, the CHCN moiety acts as a spacer be-
2
2
2
Mes Si(CN)Si(D)Mes (14’), (and a mesityl-containing unknown
2
2
[
27]
compound) in a ratio of approximately 1:1.5, consistent with
our proposal.
tween the two Mes SiH groups which relieves crowding within
2
The addition of CH CN to disilene 4 in the presence of LiCl
resulted in the formation of small amounts of silyl cyanide 14,
the molecule. Clearly, the reduction of steric congestion in 15
and 16 increases their susceptibility towards hydrolysis under
basic conditions, which is more consistent with the reactivity
3
which was formed in significant quantities when CH CH CN
3
2
[33,34]
was added to the disilene. Although KCN reacted with 4 to
give 14, the presence of either HCN or a cyanide salt in the
acetonitrile or propionitrile is unlikely; the acetonitrile was pu-
rified by passage through a column of alumina and degassed
of typical silyl acetonitriles.
As the molecular structure of
13 indicates, the CH CN moiety is situated between two bulky
2
mesityl groups (Figure 2). In contrast to less hindered silyl ace-
tonitriles, the closely spaced mesityl groups of 13 appear to
protect the nitrile group from further reaction and protect the
silicon center from nucleophilic attack.
prior to use and the propionitrile was distilled from CaH and
2
degassed. Cleavage of the (iso)nitrile functional group has
been observed in the addition of (iso)nitriles to other low
Ketenimine 9 hydrolyzes cleanly to the amide 11 upon chro-
matography, exposure to the ambient atmosphere or under
acidic conditions. The azadisiletine 5 and 6 and their enamine
tautomers (7 and 8) decompose to a mixture of products upon
exposure to the ambient atmosphere; the mixtures were not
separated.
[
21,28]
valent Group 14 compounds.
Further work is necessary to
understand the formation of compound 14. Nonetheless, the
apparent CÀC bond activation demonstrated in these reactions
is very interesting and will be explored.
Reactivity studies
Comparison between the disilene-acetonitrile adducts and
the acetonitrile adducts on the Si(100)-2ꢀ1 surface
Given the potential of surface nitrile adducts to serve as linkers
for biological molecules, we performed some preliminary stud-
ies on the reactivity of the molecular adducts. We began with
the investigation of the reactivity of silyl acetonitrile 13. Specif-
ically, we were interested in converting the nitrile group of 13
to a carboxylic acid or an amine, as these functional groups
are useful in synthesis. Nitriles can typically be hydrolyzed to
carboxylic acids by treatment of the compound with dilute
Our studies indicate that disilene 4 and the Si(100)-2ꢀ1 surface
are similar in reactivity towards acetonitrile. Despite the signifi-
cant differences in the reaction conditions, a-CH insertion ad-
ducts (13 and 1) and cycloadducts (5 and 2a,b) are formed in
both instances. In contrast, a ketenimine was not observed in
the addition of acetonitrile to disilene 4, although one was ob-
served on the surface. The formation of the products in the
molecular system appears to be dependent on the polarization
of the Si=Si bond through coordination of a donor molecule
(either THF/nitrile or LiCl) to the disilene. The a-CH insertion is
only observed in the presence of LiCl; coordination of THF or
the nitrile apparently is not sufficient for the abstraction of an
a-hydrogen atom. The formation of a ketenimine in the molec-
ular system appears to rely on the enhanced acidity of the a-
CH bond in the nitrile as in phenylacetonitrile; no ketenimine
was formed in the addition of acetonitrile to disilene 4. On the
surface, the Si=Si dimers are not static, they rapidly tilt back
[
29]
aqueous acid or base at elevated temperatures; alternatively,
[
29]
nitriles can be reduced to amines using LiAlH4. In general,
silyl acetonitriles (R SiCH CN) are useful reagents in synthe-
3
2
[
30–32]
sis.
The nitrile group within a silyl acetonitrile increases
the acidity of the a-hydrogen atoms, but also increases the
susceptibility of the compound to SiÀC cleavage by nucleo-
[
33,34]
philic attack at silicon.
The weakened SiÀC bond is often
taken advantage of in synthesis; however, this property also
makes it difficult to modify the nitrile groups of silyl aceto-
nitriles without the formation of silanol (R SiOH) derivatives. In
3
fact, there are no reports of the hydrolysis or reduction of a
nitrile group within a silyl acetonitrile.
[1]
and forth polarizing the Si=Si bond and this motion appears
to enable the formation of a-CH insertion (1), cycloaddition
(2a,b), and ketenimine derivatives (3a,b) without donor
molecules.
Reactivity studies revealed that 13 is relatively stable under
a variety of conditions: in the presence of acid, only small
amounts of mesitylene were formed and, in the presence of
base, no reaction was observed. In reaction with excess LiAlH4,
only small amounts of (Mes SiH) and Mes SiH were isolated.
Of the three types of adducts formed on the Si surface, only
the a-CH insertion adduct (1) has been identified unambigu-
2
2
2
2
[2–7]
The formation of (Mes SiH) and Mes SiH suggests that the
ously.
However, all of the structures of molecular adducts
2
2
2
2
CH CN group of 13 is susceptible to cleavage under these
conditions.
were established unambiguously using spectroscopic tech-
niques. Although the majority of the characterization data ob-
tained for 13 cannot be compared to the data obtained for 1,
the FTIR spectroscopic data of 13 can be directly compared to
the MIR-FTIR spectroscopic data of 1. The wavenumber of the
absorption assigned to the CꢀN stretching vibration of 13
2
In comparison, silyl acetonitriles (Mes SiH) (CHCN) (15) and
2
2
Mes SiH(CH CN) (16) are stable towards acid; however, in con-
2
2
trast to 13, cleavage of the SiÀCH bonds of 15 and 16 occurs
x
rapidly and nearly quantitatively in the presence of base at
[
34]
À1
room temperature to give Mes SiH(OH).
The CÀC bond
(2235 cm ) is quite similar to that assigned to the CꢀN
2
À1 [3,7]
lengths within the CH CN moiety of 13 and 15 are similar
1.454(3) and 1.460(3) ꢂ, respectively) and the CꢀN bonds of
stretching vibration in 1 (2228 cm ).
Given the limitations
x
[
34]
(
of the techniques available to characterize surface adducts, the
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exact structure of surface adduct 2 could not be estab-
Conclusion
[
2–7]
lished.
Two structures for 2 have been proposed: an 1,2,3-
azadisiletine, formed by the reaction between the CꢀN bond
of acetonitrile and the Si=Si bond of the dimer (2a), and a cy-
The a-CH insertion products and cycloadducts were formed by
the addition of nitriles to Mes Si=SiMes (4); the outcome de-
2
2
cloadduct containing a CH CH=N moiety within a five-mem-
pended upon the nature of the nitrile and the reaction condi-
tions. In THF, in the absence of salt, nitriles reacted with 4
through the CꢀN bond to give 1,2,3-azadisiletines. Enamines
were also observed and likely formed by tautomerization of
the initial cycloadducts. With phenylacetonitrile, a ketenimine
was formed as a major product rather than an azadisiletine.
The change in reactivity was attributed to the enhanced acidity
of the a-hydrogen atoms in phenylacetonitrile. In the presence
of LiCl, acetonitrile and propionitrile added to the disilene to
give an a-CH insertion product (13) and/or the formal HCN
adduct of the disilene (14).
2
bered ring (2b) (Figure 1). On the basis of our results, we be-
lieve that 2a is the correct structure and that 2b is not pres-
ent. Finally, we propose that a ketenimine similar in structure
to 9, without a bond between the
surface and the terminal carbon, is
more reasonable and may indeed
be the actual species present on
the surface (Figure 3).
Figure 3. Proposed structure
for the surface ketenimine
The acetonitrile adducts formed
on the Si(100)-2ꢀ1 surface may be
modified to allow for the attach-
ment of another layer of organic
Unlike typical silyl acetonitriles, Mes Si(CH CN)Si(H)Mes (13)
2
2
2
was stable under a variety of conditions likely due to the pres-
ence of four bulky mesityl substituents. On the other hand, the
phenylacetonitrile adduct of disilene 4, that is, ketenimine 9,
rapidly hydrolyzed and rearranged in the presence of acid to
give silyl amide 11. 1,2,3-Azadisiletines and their enamine
tautomers were susceptible to uncontrolled hydrolysis under
the ambient atmosphere.
molecules. However, since three types of adducts are formed
on the Si surface, which cannot be separated from one anoth-
er, modifying the surface by simple chemical procedures may
lead to a complex mixture. It is, therefore, instructive to under-
stand the reactivity of the molecular adducts prior to modifica-
tion of any surfaces. Since molecular adducts are similar in
structure to surface adducts, the reactivity of the adducts
should also be comparable. Silyl acetonitrile 13 was unreactive
Since the acetonitrile adducts formed on the Si(100)-2ꢀ1 sur-
face were similar in structure to those formed by the addition
of acetonitrile to disilene 4, the reactivity of the molecular ad-
ducts was investigated to gain some insight into the possible
reactivity of the surface adducts. Silyl acetonitrile 13 is analo-
gous in structure to surface adduct 1; however, the bulky mesi-
tyl substituents within 13 reduced the reactivity of the nitrile
group, and thus, 13 could not be used as a molecular model
towards acid, base, or LiAlH ; the mesityl substituents appear
4
to protect the SiCH CN moiety from further reaction. Although
2
silyl acetonitriles 15 and 16 contain more accessible nitrile
groups than 13, they appear to be unreactive towards acid as
well, since 15 and 16 are isolated under acidic conditions.
However, the intentional hydrolysis of the nitrile groups of 15
[34]
and 16 under acidic conditions has not been investigated.
for surface adduct 1. The CH CN moiety of 1 is more exposed
2
Under basic conditions, the SiÀCH CN bonds of 15 and 16 are
on the surface, which may lead to increased reactivity of the
nitrile group; however, previous results suggest that only
x
[
34]
readily cleaved and the SiÀCH bonds of simple silyl acetoni-
[34]
triles are cleaved under both acidic and basic conditions;
cleavage of the SiÀCH CN bond will occur on the surface if hy-
2
[34]
thus, hydrolysis of the nitrile group within a silyl acetonitrile
has not been observed previously. The nitrile group of surface
adduct 1 may be more reactive than the nitrile group within
drolysis of the nitrile group is attempted. As an alternative,
reduction of the nitrile group of 1 using H /W may be success-
2
[35]
ful.
1,2,3-Azadisiletine 5 is structurally similar to surface
1
3; the bonds to the bulk crystal are pinned back in a cis fash-
adduct 2a; both adducts appear to contain an exposed C=N
bond. Thus, 5 may be comparable in reactivity to 2a; however,
ion which exposes the CH CN group on the surface. Given that
2
silyl acetonitriles are more susceptible to cleavage of the SiÀ our results suggest that the hydrolysis of 5 will not be straight-
CH bond than to hydrolysis of the nitrile group, we believe
forward although the reactivity of 5 needs to be examined in
greater detail. The addition of phenylacetonitrile to the surface
should be examined as the enhanced acidity of the a-hydro-
gen atoms may lead to a cleaner reaction and an adduct that
is easily and cleanly hydrolyzed in a subsequent step.
that attempted hydrolysis of the nitrile group of 1 may simply
result in cleavage of the CH CN group from the surface.
2
On the basis of the observed decomposition of the 1,2,3-
azadisiletines and their enamine tautomers under ambient
conditions, it is unlikely that the hydrolysis of the analogous
compounds on the surface (i.e., 2a) will be clean and lead to
a single product. In contrast, the hydrolysis of a surface
ketenimine (as in Figure 3) may cleanly lead to an amide or di-
rectly to an amine on the surface which could be utilized for
the attachment of more complex molecules. To achieve the
clean formation of a ketenimine on the surface, we propose
the use of phenylacetonitrile.
Interestingly, Hamers has recognized that the degree of zwit-
terionic character of a Group 14 (001) surface dimer, achieved
by the tilting of the dimers on the surface, can strongly influ-
[36]
ence the reaction pathway. Herein, we have reported that
the use of a simple salt (i.e., LiCl) can alter the course of a reac-
tion of a disilene. The use of donor molecules to enhance or
alter reactivity is a concept that has not been widely recog-
nized or exploited in disilene chemistry although there have
been a few scattered reports which indicate that the use of
a donor to influence a reaction pathway may be more widely
[21,24]
applicable.
We intend to explore this concept more fully.
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ꢁ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
increase in the relative amount of 8 until 6, 8a, and 8b were pres-
ent in a ratio of about 1:7:1 as estimated by H NMR spectroscopy.
Experimental Section
1
Addition of CH CN to disilene 4: A deep yellow solution of 4
Compounds 6 and 8 decomposed upon prolonged exposure to at-
mospheric moisture; therefore, 6 and 8 were characterized as
a mixture. NMR spectral data for 6 were obtained from a solution
containing 6 and 8a/b in a ratio of about 6:4:1. NMR spectral data
for 8 were obtained from a solution containing 6 and 8a/b in
3
(
made from Mes Si(SiMe ) (50 mg, 0.12 mol) and dissolved in THF
2 3 2
(
8 mL)) and CH CN (1 mL, excess) was heated in a sealed Schlenk
3
tube in an oil bath at 1008C for 24 h; the deep yellow solution de-
1
colorized to very pale yellow. Analysis of an aliquot by H NMR
+
spectroscopy revealed the presence of 5 and 7 in a ratio of >10:1.
The relative amount of 7 in solution increased slowly under an
inert atmosphere and, upon exposure to trace amounts of atmos-
pheric moisture (sample in an NMR tube sealed only with Parafilm),
the relative amount of 7 appeared to increase more rapidly. Expo-
sure to atmospheric moisture led to decomposition of 5 and 7,
and therefore, they were not separated prior to characterization.
NMR spectral data for 5 were obtained from a solution containing
a ratio of about 1:7:1. High-resolution EI-MS for C H Si N [M ]:
39
49
2
m/z calcd: 587.3404; found: 587.3403.
1
Data for 6: H NMR (C D , 400 MHz): d=6.69 (s, 4H; Mes m-H), 6.65
6
6
(
s, 4H; Mes m-H), 2.87 (q, 2H; CH , J=7 Hz), ~2.7–2.4 (vbrs, 12H;
2
Mes o-CH ), 2.23 (s, 12H; Mes o-CH ), 2.07 (s, 6H; Mes p-CH ), 2.06
3
3
3
13
(
s, 6H; Mes p-CH ), 1.23 ppm (t, 3H; CH , J=7 Hz); C NMR (C D ,
3
3
6
6
1
00 MHz): d=217.12 (C=N), ~144.8 (vbr, Mes o-C), 143.71 (Mes o-
C), 139.19 (Mes p-C), 139.06 (Mes p-C), 133.87 (Mes i-C), 133.53
Mes i-C), 129.44 (br, Mes m-C), 129.28 (Mes m-C), 38.07 (CH2),
4.53 (Mes o-CH ), 24.38 (Mes o-CH ), 21.03 (Mes p-CH ), 21.00 (Mes
5
and 7 in a ratio of about 8:1. NMR spectral data for 7 were ob-
(
tained from a solution containing 5 and 7 in a ratio of about 1:5.
Solutions of 5 and 7 were contaminated with a minor amount of
2
3
3
3
29
p-CH ), 9.50 ppm (CH ); Si NMR (C D ): d=7.7 ppm (Mes SiN,
Mes SiC).
3
3
6
6
2
+
impurities. High-resolution EI-MS for C H Si N [M ]: m/z calcd:
[40]
38
47
2
2
5
73.3247; found: 573.3225.
1
Data for 8: H NMR (C D , 600 MHz): d=6.67 (s, 4H; Mes m-H), 6.65
6
6
1
Data for 5: H NMR (C D , 600 MHz): d=6.69 (s, 4H; Mes m-H), 6.64
6
6
(s, 4H; Mes m-H), 5.15 (q, 1H; =CH, J=7 Hz, a), 5.05 (q, 1H; =CH,
(
s, 4H; Mes m-H), ~2.8–2.2 (vbrs, Mes o-CH ), 2.55 (s, CH ; total
3
3
3
3
J=7 Hz, b), 4.56 (s, 1H; NH, J =24 Hz, a), 4.21 (s, 1H; NH, J =
SiH SiH
1
5H), 2.22 (s, 12H; Mes o-CH ), 2.08 (s, 6H; Mes p-CH ), 2.06 ppm
3
3
25 Hz, b), 2.40 (s, 12H; Mes o-CH ), 2.34 (s, 12H; Mes o-CH ), 2.06
3 3
1
3
(
s, 6H; Mes p-CH3); C NMR (C D , 150 MHz): d=214.76 (C=N),
6 6
(s, 12H; Mes p-CH ), 1.69 (d, 3H; CH , J=7 Hz, b), 1.56 ppm (d, 3H;
3 3
~
144.8 (v br, Mes o-C), 143.71 (Mes o-C), 139.22 (Mes p-C), 139.13
13
CH , J=7 Hz, a); C NMR (C D , 100 MHz): d=151.52 (=C-NH),
3
6
6
(
Mes p-C), 133.77 (Mes i-C), 133.25 (Mes i-C), ~129.4 (br, Mes m-C),
1
44.47 (Mes o-C), 143.74 (Mes o-C), 138.74 (Mes p-C), 138.70 (Mes
1
2
7
29.29 (Mes m-C), 33.35 (CH ), 24.5 (Mes o-CH ), 24.35 (Mes o-CH ),
3
3
3
p-C), 136.15 (Mes i-C), 133.41 (Mes i-C), 129.43 (Mes m-C), 129.27
(Mes m-C), 103.79 (=CH, b), 102.06 (=CH, a), 24.53 (Mes o-CH3),
29
1.03 (Mes p-CH ), 20.99 ppm (Mes p-CH ); Si NMR (C D ): d=8.1,
3
3
6
6
.0 ppm.
2
(CH
0.7 (Mes
4.22 (Mes o-CH ), 21.01 (Mes p-CH ), 21.00 (Mes p-CH ), 16.58
3
3
3
1
29
Data for 7: H NMR (C D , 600 MHz): d=6.66 (s, 4H; Mes m-H), 6.64
3
, b), 11.28 ppm (CH
3
, a); Si NMR (C
6
D
6
): d=1.5 (Mes
SiC, b).
SiN, a),
2
6
6
3
(
s, 4H; Mes m-H), 4.70 (s, 1H; =CH ), 4.62 (s, 1H; =CH , J =
SiH
2 Hz), 4.53 (s, 1H; NH, J =25 Hz), 2.42 (s, 12H; Mes o-CH ), 2.29
SiH 3
2
SiN, b), À7.1 (Mes
2
SiC, a), À11.5 ppm (Mes
2
cis
trans
3
1
Addition of PhCH CN to disilene 4: A deep yellow solution of 4
2
(
s, 12H; Mes o-CH ), 2.06, 2.05 ppm (both s, 12H; Mes p-CH );
3 3
(made from Mes Si(SiMe ) (51 mg, 0.12 mol) and dissolved in THF
2
3 2
1
3
C NMR (C D , 150 MHz): d=160.17 (=C-NH), 144.55 (Mes o-C),
6
6
(5 mL)) and PhCH CN (26 mg, 0.22 mmol) was stirred at room tem-
2
1
43.77 (br, Mes o-C), 138.86 (Mes p-C), 138.85 (Mes p-C), 135.73 (br,
Mes i-C), 132.98 (Mes i-C), 129.43 (Mes m-C), 129.29 (Mes m-C),
2.95 (=CH ), 24.55 (Mes o-CH ), 24.47 (Mes o-CH ), 21.02 (Mes p-
perature for 48 h, then the solvent was removed under vacuum;
a bright yellow oil was obtained. H NMR spectroscopic analysis of
the crude product revealed the presence of 9 and 10 in a ratio of
about 5:1, as well as a small amount of impurities and unreacted
1
9
2
3
3
29
CH ), 20.99 ppm (Mes p-CH ); Si NMR (C D ): d=0.5 (Mes SiN),
3
3
6
6
2
À6.7 ppm (Mes SiC).
2
PhCH CN; 9 and 10 were characterized as a mixture. Separation of
the mixture by preparative thin-layer chromatography (silica gel,
2
Tautomerization of 5 to 7: Half of a mixture containing 5 and 7
(
ratio of 10:1) was dissolved in C D (0.6 mL) and the other half
1:1 CH Cl /hexanes) yielded a white solid (11 mg, 26%) identified
2 2
6
6
was dissolved in [D ]THF (0.6 mL). The solutions were transferred
to Teflon screw-capped NMR tubes (J. Young tubes) and heated in
as 11, which was contaminated with about 4% of a mesityl-con-
taining unknown and silicone grease. Compounds 9 and 10 were
not recovered from the chromatographic plate. Data for 9 and 10:
8
an oil bath at 1008C overnight (ca. 17 h) to give 5 and 7 in a ratio
1
À1
of about 1:1 in both solutions, as estimated by H NMR spectrosco-
IR (thin film): n˜ =2100 cm (SiH and N=C=C); high-resolution
+
py. Additional heating resulted in a slow increase in the relative
amount of 7 in both solutions until 5 and 7 were present in a ratio
of about 1:2 (C D ) and about 1:1.5 ([D ]THF).
EI-MS for C44
H
51Si
2
N [M ]: m/z calcd: 649.3560; found: 649.3534.
1
Data for 9: H NMR (C D , 600 MHz): d=7.14–7.09 (m, 2H; Ph m-H),
6
6
6
6
8
7.04–7.00 (m, 2H; Ph o-H), 6.88–6.83 (m, 1H; Ph p-H), 6.69 (s, 4H;
1
Mes m-H), 6.63 (s, 4H; Mes m-H), 5.78 (s, 1H; SiH, J =184 Hz,
Addition of CH CH CN to disilene 4: A deep yellow solution of 4
SiH
3
2
2
JSiH =11 Hz), 4.17 (s, 1H; =CHPh), 2.33 (vbrs, Mes o-CH ꢀ2), 2.08
(
(
made from Mes Si(SiMe ) (50 mg, 0.12 mol) and dissolved in THF
3
2
3 2
13
(s, 6H; Mes p-CH ), 2.04 (s, 6H; Mes p-CH ) ppm; C NMR (C D ,
8 mL)) and CH CH CN (1 mL, excess) was heated in a sealed
3
3
6
6
3
2
1
1
50 MHz): d=175.04 (N=C=C), 145.42 (Mes o-C), 144.70 (Mes o-C),
39.80 (Mes p-C), 139.26 (Mes p-C), 137.40 (Ph i-C), ~131.3 (br, Mes
Schlenk tube in an oil bath at 1008C for 12 h; the deep yellow so-
lution decolorized to very pale yellow. The solvent was removed
under vacuum; a pale yellow solid was obtained. The crude prod-
i-C), 129.94 (br, Mes i-C, Mes m-C), 129.28 (Mes m-C), 128.98 (Ph m-
1
C), 123.97 (Ph o-C), 122.22 (Ph p-C), 42.64 (N=C=CHPh), 24.30 (br,
uct was analyzed by H NMR spectroscopy; 6 was the only nitrile
2
9
Mes o-CH ꢀ2), 21.06 (Mes p-CH ), 20.96 ppm (Mes p-CH ); Si NMR
adduct observed. The crude solid was then washed twice with hex-
anes to remove impurities, including small amounts of
3
3
3
(
C D ): d=À24.7 (Mes SiN), À55.1 ppm (Mes SiH).
6
6
2
2
[
37]
[38,39]
1
(
Mes SiH)
and Mes SiH .
The remaining solvent was re-
Data for 10: H NMR (C D , 600 MHz): d=7.33–7.29 (m, 2H; Ph o-
6 6
2
2
2
2
1
moved under vacuum; a white solid was obtained. H NMR spec-
troscopic analysis of the purified product revealed the presence of
H), 7.21–7.16 (m, 2H; Ph m-H), 7.00–6.96 (m, 1H; Ph p-H), 6.68 (s,
Mes m-H), 6.60 (s, 4H; Mes m-H), 6.16 (s, 1H; =CHPh), 6.15 (brs,
3
[41]
6
and two diastereomers of 8 (a and b) in a ratio of about 19:2:1.
Exposure of the solution to trace amounts of atmospheric moisture
sample in an NMR tube sealed only with Parafilm) resulted in an
1H; NH, JSiH =24 Hz), 2.45 (s, Mes o-CH ), 2.30 (s, Mes o-CH ),
3 3
13
2.07 (s, Mes p-CH ), 2.03 ppm (s, Mes p-CH ); C NMR (C D ,
3
3
6
6
(
150 MHz): d=154.16 (=C-NH), ~144.7 (br, Mes o-C), 143.83 (Mes o-
Chem. Eur. J. 2015, 21, 2480 – 2488
www.chemeurj.org
2485 ꢁ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
[42]
[42]
C), 139.72 (Ph i-C), 139.05 (Mes p-C), 139.00 (Mes p-C), 135.33
Mes i-C), 132.59 (Mes i-C), 129.52 (Mes m-C), 129.45 (Mes m-C),
The addition of excess LiCl to disilene 4 indeed produced
(
Mes Si(Cl)Si(H)Mes .
2
2
1
2
28.98 (Ph m-C), 127.48 (Ph o-C), 124.81 (Ph p-C), 108.86 (=CHPh),
4.77 (Mes o-CH ), 24.39 (Mes o-CH ), 21.03 (Mes p-CH ), 20.96 ppm
[
43] 1
Data for 14:
H NMR (C D , 600 MHz): d=6.66 (s, 4H; Mes m-H),
6
6
3
3
3
1
2
9
6.59 (s, 4H; Mes m-H), 5.84 (s, 1H; SiH, JSiH =186 Hz), 2.36 (vbrs,
4H; Mes o-CH ), 2.05 (s, 6H; Mes p-CH ), 2.01 ppm (s, 6H; Mes p-
CH3); C NMR (C D , 150 MHz): d=145.63 (Mes o-C), ~145.41 (v br,
(
(
Mes p-CH3);
Mes SiC).
Si NMR (C D ): d=4.0 (Mes SiN), À4.1 ppm
6
6
2
2
3
3
2
13
6
6
1
Data for 11: White solid; H NMR (C D , 600 MHz): d=7.05–6.93 (m,
Mes o-C), 140.24 (Mes p-C), 139.65 (Mes p-C), 130.00 (br, Mes m-C),
6
6
5
H; Ph), 6.70 (s, 4H; Mes m-H), 6.62 (s, 4H; Mes m-H), 5.75 (s, 1H;
129.95 (Mes i-C), 129.43 (br, Mes m-C), 128.53 (Mes i-C), 24.55 (br,
1
[44] 29
SiH, J =184 Hz), 5.58 (br s, 1H; NH), 3.46 (s, 2H; CH ), 2.36 (s,
1
6
Mes o-CH
(C
3
), 21.02 (Mes p-CH
3
), 20.92 ppm (Mes p-CH
3
);
Si NMR
SiH
2
2H; Mes o-CH ), 2.09 (s, 18H; Mes o-CH , Mes p-CH ), 2.04 ppm (s,
D
6
6
): d=À49.7 (Mes
2
SiCN), À53.5 ppm (Mes
2
SiH); Raman: n˜ =
3
3
3
1
3
H; Mes p-CH3); C NMR (C D , 150 MHz): d=172.96 (C=O), 145.44
2919 (s), 2730 (w), 2180 (m, CꢀN), 2160 (w, SiH), 1604 (s), 1445 (w),
6
6
(
Mes o-C), 144.23 (Mes o-C), 138.88 (Mes p-C), 138.81 (Mes p-C),
1379 (m), 1289 (s), 1058 (w), 945 (w), 573 (s), 552 (w), 536 (w),
À1
1
1
35.86 (Ph i-C), 132.61 (Mes i-C), 131.17 (Mes i-C), 130.04 (Ph o-C),
29.89 (Mes m-C), 129.18 (Ph m-C), 129.13 (Mes m-C), 127.26 (Ph p-
477 cm (w); IR: n˜ =3023 (w), 2964 (m), 2919 (m), 2851 (w), 2176
(w, Cꢀ N), 2139 (w, SiH), 1603 (m), 1549 (w), 1449 (m), 1409 (m),
C), 47.23 (CH ), 24.77 (br, Mes o-CH ), 24.37 (Mes o-CH ), 21.04 (Mes
p-CH3), 20.91 ppm (Mes p-CH3);
1378 (w), 1288 (w), 1263 (s), 1094 (m), 1063 (m), 1027 (s), 848 (m),
2
3
3
29
À1
Si NMR (C D ): d=À18.7
800 (s), 740 (m), 707 (m), 625 (m), 604 cm (m); EI-MS: m/z (%):
6
6
+
+
+
(
2
Mes SiN), À54.4 ppm (Mes SiH); IR: n˜ =3407 (w, NH), 3024 (m),
559 (86) [M ], 544 (64) [M ÀMe], 440 (24) [M ÀMes], 424 (21)
2
2
+
+
+
961 (m), 2920 (m), 2854 (w), 2137 (w, SiH), 1689 (m, C=O), 1604
[M ÀMesÀMe], 292 (21) [Mes
2
SiCN ], 267 (100) [Mes
2
SiH ], 251
+
(
1
m), 1549 (w), 1495 (w), 1452 (m), 1404 (s), 1233 (w), 1061 (w),
028 (w), 928 (w), 847 (m), 829 (m), 802 (m), 747 (m), 702 (m), 619
(36), 235 (23), 220 (21), 147 (55) [MesSi ], 120 (14); high-resolution
+
EI-MS for C37H45Si N [M ]: m/z calcd: 559.3091; found: 559.3072.
2
À1
+
(
m), 591 (m), 566 (m), 550 cm (m); EI-MS: m/z (%): 667 (17) [M ],
+
+
+
Addition of CD
(5 drops) was added to a yellow solution of disilene 4 (made from
Mes Si(SiMe (210 mg, 0.51 mol) and partially dissolved in THF
3
CN to disilene 4 in the presence of LiCl: CD CN
3
6
52 (25) [M ÀMe], 576 (29) [M ÀPhCH ], 533 (14) [M
2
+
+
ÀPhCH CONH], 400 (75) [M ÀMes SiH], 309 (16) [Mes SiNHCO ],
2
2
2
+
+
+
2
)
3 2
2
1
82 (100) [Mes SiNH ], 267 (28) [Mes SiH ], 147 (13) [MesSi ],
2 2 2
+
(10 mL)) followed by LiCl (5 mg), which had been flame dried
under vacuum. The yellow solid slowly dissolved and the solution
decolorized to clear, pale yellow within 90 min. The solution was
20 (17) [MesH], 91 (8) [PhCH2 ]; high-resolution EI-MS for
+
C H Si NO [M ]: m/z calcd: 667.3666; found: 667.3646.
4
4
53
2
stirred at room temperature overnight. The THF and CD CN were
Addition of CH CN to disilene 4 in the presence of LiCl: CH CN
3
3
3
removed under vacuum and C D (ca. 0.7 mL) was added to the
(
(
0.1 mL, 1.9 mmol) was added to a yellow solution of disilene 4
6
6
light yellow residue to precipitate the LiCl. A clear, yellow solution
was obtained after filtering the solution through a cotton plug.
made from Mes Si(SiMe ) (150 mg, 0.36 mol) and partially dis-
2
3 2
solved in THF (10 mL)), followed by addition of a solution of LiCl in
THF (0.25 mL, 2 mgmL , 0.012 mmol). Upon addition of the LiCl
À1
1
H NMR analysis of the crude product revealed the presence of
Mes Si(CD CN)Si(D)Mes (13’), Mes Si(CN)Si(D)Mes (14’), and a mesi-
solution, the yellow solid began to dissolve and, upon complete
dissolution, the yellow color of the solution began to fade. The so-
lution was allowed to stir at room temperature overnight. The sol-
vent was then removed under vacuum and a pale yellow film was
obtained. The crude product consisted of four compounds: 13, 14,
2
2
2
2
2
[27]
tyl-containing unknown compound in a ratio of ca. 1:1.5:1.4, and
other impurities in small amounts, including Mes Si(OH)Si(H)Mes
2
2
and Mes
Si(Cl)Si(H)Mes
2
. The mixture was separated by preparative
Cl –hexanes). Com-
2
thin-layer chromatography (silica gel, 3:7 CH
2
2
[13b]
[13b]
Mes Si(OH)Si(H)Mes
about 9:1:1:1, respectively, as estimated by H NMR spectroscopy.
Preparative thin-layer chromatography (silica gel, 3:7 CH Cl -hex-
and Mes Si(Cl)Si(H)Mes
in a ratio of
pound 13’ was isolated as a white solid contaminated with small
amounts of a mesityl-containing unknown, as well as trace
amounts of other impurities including 13 (13 mg total). Compound
2
2,
2
2,
1
2
2
1
4’ was isolated as a white solid contaminated with 14 and
anes) of the mixture yielded 13 as a white solid (43 mg, 42%).
Impure 14 was also obtained from the chromatographic plate, but
in trace amounts.
1
Mes Si(OH)Si(H)Mes (ratio of ca. 13:1:1) (23 mg total). The H NMR
2
2
spectrum of the unknown compound revealed signals at 6.67,
.48, and 2.06 ppm; however, this compound has not yet been
identified.
2
1
Data for 13: White solid; m.p. 186–1928C; H NMR (C D , 600 MHz):
6
6
1
d=6.66 (s, 8H; Mes m-H), 5.78 (s, 1H; SiH, J =184 Hz), 2.54 (s,
SiH
2
Data for 13’: H NMR (C H , 92 MHz): d=5.77 (SiD), 2.47 ppm (CD ).
2
2
6
1
H; CH ), 2.31 (brs, 12H; Mes o-CH ), 2.10 (brs, 12H; Mes o-CH ),
6
6
2
2
3
3
13
.06 and 2.04 ppm (each s, 12H; total, Mes p-CH3); C NMR (C D ,
2
6
6
Data for 14’: H NMR (C H , 92 MHz): d=5.85 ppm (SiD); IR: n˜ =
6
6
00 MHz): d=145.02 (Mes o-C), 144.70 (Mes o-C), 139.47 (Mes p-C),
39.17 (Mes p-C), 131.43 (Mes i-C), 130.69 (Mes i-C), 130.10 (Mes m-
3
1
1
024 (m), 2966 (m), 2922 (m), 2855 (w), 2177 (w, CꢀN), 2150 (w),
604 (s), 1552 (m), 1449 (s), 1409 (m), 1377 (m), 1288 (m), 1265 (m),
C), 129.28 (Mes m-C), 118.71 (CꢀN), 24.80 (Mes o-CH ꢀ2), 21.00
À1
3
234 (w), 1063 (m), 1028 (m), 848 cm (s); EI-MS: m/z (%): 560
29
(
Mes p-CH ), 20.89 (Mes p-CH ), 8.10 ppm (CH ); Si NMR (C D ):
+
+
+
3
3
2
6
6
(
(
100) [M ], 545 (73) [M ÀMe], 441 (25) [M ÀMes], 425 (21), 292
d=À22.8 (Mes SiCH ), À54.7 ppm (Mes SiH); IR: n˜ =3023 (m), 2963
+
+
+
2
2
2
17) [Mes SiCN ], 268 (95) [Mes SiD ], 251 (33), 147 (42) [MesSi ],
2
2
(
(
(
s), 2921 (s), 2856 (m), 2731 (w), 2235 (s, CꢀN), 2138 (s, SiH), 1731
+
119 (17) [Mes ].
w), 1604 (s), 1549 (m), 1451 (s), 1408 (m), 1377 (m), 1287 (m), 1264
À1
m), 1235 (m), 1156 (w), 1027 (m), 953 (w), 928 (w), 848 cm (m);
Addition of H SO to 13: Compound 13 (32 mg, 0.06 mmol) was
dissolved in THF (15 mL) and 1m H SO (10 mL) was added to the
2 4
solution. The solution was heated in an oil bath at 908C overnight
then cooled to room temperature and extracted with CH Cl (3ꢀ
2
4
+
+
+
EI-MS: m/z (%): 573 (58) [M ], 558 (69) [M ÀMe], 453 (18) [M
+
+
ÀMesH], 306 (34) [M ÀMes SiH], 267 (100) [Mes SiH ], 147 (57)
2
2
+
+
[
MesSi ]; high-resolution EI-MS for C H Si N [M ]: m/z calcd:
38
47
2
2
2
5
73.3247; found: 573.3259; elemental analysis calcd (%) for
10 mL). The combined organic layers were dried over MgSO , fil-
4
C H Si N: C 79.52, H 8.25, N 2.44; found: C 79.65, H 7.99, N 2.69.
tered, and concentrated. A clear, colorless film was obtained
(28 mg). H NMR spectroscopic analysis of the crude product re-
3
8
47
2
1
Note: Mes Si(OH)Si(H)Mes was likely formed by the addition of ad-
2
2
ventitious water to the disilene and Mes Si(Cl)Si(H)Mes was likely
vealed the presence of 13 and mesitylene in a ratio of about 13:1,
2
2
formed by the addition of trace amounts of HCl present in the LiCl.
as well as a small amount of impurities.
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Addition of NaOH to 13: A mixture of 13 and mesitylene (ob-
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perature and extracted with CH Cl , as described above; a clear,
colorless film was obtained (26 mg). The H NMR spectrum of the
crude product revealed the presence of unreacted 13 and some
impurities.
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Addition of LiAlH to 13: Compound 13 (43 mg, 0.08 mmol) was
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3811.
[
39] Compounds (Mes
2
SiH)
2
and Mes
2
SiH
2
are often present in trace
Si(SiMe , and are commonly
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amounts in the disilene precursor, Mes
2
3 2
)
observed in reactions involving 4.
Chem. Eur. J. 2015, 21, 2480 – 2488
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1
29
29
[
40] In the H- Si gHMBC spectrum of 6, both Si signals are at the same
chemical shift. The sample contained a number of impurities; thus, the
assignment is tentative.
[44] A signal which could be assigned to a nitrile group was not observed
1
3
in the C NMR spectrum of 14, even after increasing the delay between
pulses to 5 s.
1
29
[
[
[
41] The coupling constant was estimated from correlations in the H- Si
gHMBC spectrum of 10.
42] Due to overlap in the H- C gHMBC spectrum, the assignment is tenta-
tive.
1
13
43] A sample of 14 was prepared by the addition of CH
3
CH
2
CN to disilene
Received: October 22, 2014
4
in the presence of LiCl and used for characterization purposes.
Published online on December 18, 2014
Chem. Eur. J. 2015, 21, 2480 – 2488
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2488
ꢁ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim