Organometallics
Communication
apical sites of the trigonal-bipyramidal coordination. The sum
0.103, while I in Figure 2 shows a bond order of 0.764 between
the Si and S atoms. This indicates that the reaction in Scheme
1ii proceeds via a pathway different from that of complex 2.
H SiPh reacts with [AuCl(PCy )] more smoothly than with
of the C−N−C angle and two Si−N−C angles of TS1
(
353.3°) suggests minor pyramidalization of the nitrogen
atom.
Elimination of amino(pinacol)borane from intermediate I
2
2
3
thiolate complex 2. The (aminosilyl)boronic ester and H SiPh
2
2
occurs easily to form the complex with an S-coordinated silyl
sulfide anion as the ligand (intermediate II). Further migration
of the Au center from S-coordination to Si-coordination leads
to formation of the thermodynamically stable product with an
are used as complementary precursors for insertion of the
diphenylsilylene group into the Au−SAr and Au−Cl bonds.
In summary, we obtained Au complexes with a thiolatosilyl
ligand by using an (aminosilyl)boronic ester as the source of a
diphenylsilylene group. The reaction occurs via initial
formation of the Si−S bond rather than direct approach of
the Si atom to the Au center, as shown by theoretical
calculations. The resulting intermediate and proposed pathway
of the total reaction were unexpected but account for the
smooth formation of the gold complex with the thiolatosilyl
ligand.
(
arenethiolate)silyl ligand (3). These two reactions from
intermediate I to II and from intermediate II to the product
occur with much lower activation energies. Formation of
intermediate I occurs with an activation energy of 22.5 kcal
−
1
mol , which should be the rate-determining step of the total
reaction. The transition state (TS1), with a structure similar to
that of intermediate I, may account for the results of kinetic
measurement.
Another pathway via direct bond formation between the Si
and Au atoms can be also considered for formation of complex
ASSOCIATED CONTENT
sı Supporting Information
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*
3
from the reaction of 1 with 2. Scheme 2 shows a possible
Scheme 2. Possible Au−Si Bond Formation for the Early
Stage of the Reaction on the Basis of DFT Calculations
1
Synthetic procedures, spectroscopic data ( H and
31
1
P{ H} NMR), and DFT calculations (PDF)
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
Corresponding Authors
■
Kohtaro Osakada − Laboratory for Chemistry and Life Science,
early stage of the reaction on the basis of DFT calculations. An
approach of the Si atom of the substrate to the Au(I) center
accompanies the formation of an Si···N···B three-membered
ring (intermediate III). Further progress of the reaction would
form a Au−Si bond and Si−N and N−B bonds of the ligand,
accompanied by cleavage of the Si−B bond. The resulting
intermediate IV has a (pinacolboryl)amine-coordinated
diphenylsilylene ligand, with coordination similar to that of
Tomohito Ide − Department of Chemical Science and
2a−d
Authors
the base-stabilized silylene complexes.
Another pathway
Yoshitaka Tsuchido − Laboratory for Chemistry and Life
Science, Institute of Innovative Research, Tokyo Institute of
Technology, Yokohama 226-8503, Japan
Kazuki Okuma − Laboratory for Chemistry and Life Science,
Institute of Innovative Research, Tokyo Institute of Technology,
Yokohama 226-8503, Japan
involving a Au(I) intermediate with a bare diphenylsilylene
ligand is not plausible for this reaction. Intermediate III has
higher energy in comparison to the substrate by 25.4 kcal
−
1
mol . The real transition state was not determined for the
formation of III and IV, and the activation for the early stage
of the reaction is higher than that for the pathway in Figure 2.
Thus, the reaction in Scheme 1i prefers the pathway initiated
by S−Si bond formation (Figure 2) rather than the pathway
that includes the direct Au−Si bond forming process in
Scheme 2.
Notes
The authors declare no competing financial interest.
We already reported that the reaction of 1 with [AuCl-
(
PCy )] gave [Au(SiPh Cl)(PCy )] in 11% yield after heating
3 2 3
9
ACKNOWLEDGMENTS
for 7 days. Attempted DFT calculations on the reaction
according to the pathway shown in Figure 2 were not
successful. The approach of 1 to [AuCl(PCy )] did not
provide a possible intermediate or transition state, and Cl and
Si atoms are separated from each other (>3.61 Å). The
calculated bond order between Si and Cl atoms is lower than
■
This work was financially supported by Grants-in-Aid for
Scientific Research (B) (No. 17H03029) from Japan Society
for the Promotion of Science and by “Dynamic Alliance for
Open Innovation Bridging” from the Ministry of Education,
Culture, Sports, Science and Technology of Japan (MEXT).
3
C
Organometallics XXXX, XXX, XXX−XXX
Tsuchido, Yoshitaka
