ACS Catalysis
Letter
for the subunits C1, C2, and C3, we found the charge of cobalt
of C1 (0.380 eV) was a bit higher than those of C2 (0.365 eV)
and C3 (0.362 eV). So does the trend for the geometries of
C1, C2, and C3 loosing the chlorine ligands. For terminal
alkynes, since the electron cloud density of β-C is higher, the
catalyst with more positive charge is easier to form branched
products. We also analyzed the natural orbitals for the subunits
C1, C2, and C3. we found the gap between the highest
occupied molecular orbital (HOMO) and lowest unoccupied
molecular orbital (LUMO) for C1 (72.99 KJ·mol−1) was much
lower than those of C2 (76.40 KJ·mol−1) and C3 (76.93 KJ·
reactive when interacting with other reactants. The LUMO−
HOMO gap of C1 was lower than those of C2 and C3
suggested that the selectivity of C1 was superior to those of C2
and C3. This is because the smaller gap means an easier way
for the electron transition. When the reactant was absorbed by
the catalyst, electron transition may occur to trigger the
reaction. Thus, the easier for the electron to transfer, the easier
for the reaction to occur, and the better selectivity is illustrated.
In addition, we computed the adsorption energies between
SiH4 and the catalysts C1, C2, and C3 (Table S13). The lower
the adsorption energy, the easier the reaction will proceed.
Moreover, the Si−H bond in the complex of SiH4-C1 is easier
to extend from 1.478 to1.584 Å. The extension of Si−H bond
was not observed in the other two complexes.
favorable. Therefore, the product with α-regioselectivity was
the main product. Subsequently, alkynes underwent the
selective 1,2-insertion of Co−Si bonds to form Co alkenyl
species D and then reacted with Ph2SiH2 to form α-selective
products and regenerate A. In addition, the intermediate D
underwent the Crabtree−Ojima−type25 isomerization to
generate α-selective products.
In conclusion, a high-nuclearity {Co14} cluster C1 was
developed, showing highly regio- and stereoselective properties
in the hydrosilylation of alkynes with primary and secondary
silane to produce α-vinylsilanes. The reaction had broad
substrate adaptability and good yields. C1 could achieve high
regioselectivity for alkyl alkynes, and the α-selectivity of some
alkyl alkynes had not been achieved in previous reports.
Leaching tests and reusability of C1 proved that the reaction
was a heterogeneous process.
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge at
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sı
Experimental procedure, characterization data, and
1
copies of H and 13C NMR spectra (PDF)
Crystallographic data for 7c (CIF)
Crystallographic data for C1 (CIF)
Crystallographic data for C2 (CIF)
Crystallographic data for C3 (CIF)
According to Figure 1, the reaction can be regarded almost
as a zero-order reaction to both substrates. Thus, this result
suggests the rate-limiting step to be the event on the catalyst.
On the basis of the results of the selectivity of internal alkynes
in our experiments (syn H/[Si] addition), deuterium-labeling
experiments, and related reports on cocatalyzed alkyne and
alkene hydrosilylation reactions,24,9 we proposed a possible
reaction process (Scheme 6). The catalytic process is carried
AUTHOR INFORMATION
Corresponding Authors
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Hai-Tao Tang − State Key Laboratory for Chemistry and
Molecular Engineering of Medicinal Resources, School of
Chemistry and Pharmaceutical Sciences of Guangxi Normal
University, Guilin 541004, People’s Republic of China;
Scheme 6. Proposed Reaction Mechanisms of
Hydrosilylation Catalyzed by {Co14} Clusters
Fu-Ping Huang − State Key Laboratory for Chemistry and
Molecular Engineering of Medicinal Resources, School of
Chemistry and Pharmaceutical Sciences of Guangxi Normal
University, Guilin 541004, People’s Republic of China;
Ying-Ming Pan − State Key Laboratory for Chemistry and
Molecular Engineering of Medicinal Resources, School of
Chemistry and Pharmaceutical Sciences of Guangxi Normal
University, Guilin 541004, People’s Republic of China;
Authors
Jun-Song Jia − State Key Laboratory for Chemistry and
Molecular Engineering of Medicinal Resources, School of
Chemistry and Pharmaceutical Sciences of Guangxi Normal
University, Guilin 541004, People’s Republic of China
Yan Cao − State Key Laboratory for Chemistry and Molecular
Engineering of Medicinal Resources, School of Chemistry and
Pharmaceutical Sciences of Guangxi Normal University,
Guilin 541004, People’s Republic of China
Tai-Xue Wu − State Key Laboratory for Chemistry and
Molecular Engineering of Medicinal Resources, School of
Chemistry and Pharmaceutical Sciences of Guangxi Normal
University, Guilin 541004, People’s Republic of China
out by a crystalline catalyst. First, under the action of the base
NaOtBu, the CoCl2 in the high-nuclearity cluster reacted with
phenylsilane to obtain a low-valent cobalt silyl intermediate A,
which could further integrate with the carbon−carbon triple
bond of alkynes to generate the intermediate B. As β-C in the
terminal alkynes was more negative than α-C, the positively
charged cobalt in the cluster catalyst reacted with β-C first.
From the perspective of steric effect, the structure of B1 was
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ACS Catal. 2021, 11, 6944−6950