Organometallics
Communication
(12) Reported Tolman cone angles PCy3 170°, PCyp3 165°, and
P(NC4H8)3 ca. 145° show that the bulkiness of these phosphines are in
the order PCy3 > PCyp3 > P(NC4H8)3. See: (a) Tolman, C. A. Chem.
Rev. 1977, 77, 313. (b) Chaplin, A. B.; Weller, A. S. J. Organomet. Chem.
2013, 730, 90. (c) Moloy, K. G.; Petersen, J. L. J. Am. Chem. Soc. 1995,
117, 7696.
(13) (a) Cheng, C.; Hartwig, J. F. Science 2014, 343, 853. (b) Cheng,
C.; Hartwig, J. F. J. Am. Chem. Soc. 2014, 136, 12064. (c) Cheng, C.;
Hartwig, J. F. J. Am. Chem. Soc. 2015, 137, 592. (d) Murata, M.;
Fukuyama, N.; Wada, J.; Watanabe, S.; Masuda, Y. Chem. Lett. 2007, 36,
910. (e) Sakurai, T.; Matsuoka, Y.; Hatanaka, T.; Fukuyama, N.;
Namikoshi, T.; Watanabe, S.; Murata, M. Chem. Lett. 2012, 41, 374.
(f) Takada, K.; Hatanaka, T.; Namikoshi, T.; Watanabe, S.; Murata, M.
Adv. Synth. Catal. 2015, 357, 2229.
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AUTHOR INFORMATION
Corresponding Author
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ORCID
Notes
The authors declare no competing financial interest.
(14) We also examined the reactions of MeCCPh and HCCPh
with HSiMe(OSiMe3)2, but in both cases, target 2,α-bis(silyl)styrenes
ACKNOWLEDGMENTS
■
This work was supported by JSPS KAKENHI Grant Numbers
JP25410058, JP15H03782, and JP16K05714 from the Japan
Society for the Promotion of Science (JSPS). We are grateful to
Dr. Eunsang Kwon (Tohoku University) for his kind help with
the X-ray analysis of 2d. We also acknowledge the Research and
Analytical Center for Giant Molecules, Tohoku University, for
some mass spectroscopic measurements and elemental analysis.
(15) The final R factors for the crystal structure analysis of 2d, i.e. R1 (I
> 2σ(I)) = 0.1247 and wR2 (all data) = 0.2825, are slightly higher than
the usual upper limits of 0.10 and 0.25, respectively, for a reliable
crystallographic model. This is possibly caused by the low quality of the
single crystal (a thin plate). Nevertheless, this analysis clearly showed
that 2d adopts a 2,α-bis-silylated trans-stilbene structure with reasonable
(16) Crystals of (Z)-2,α-bis(silyl)stilbene 2d showed blue fluorescence
upon irradiation with 254 nm UV light.
(17) (a) Takano, K.; Ikeda, Y.; Kodama, S.; Ishii, Y. Chem. Commun.
2015, 51, 4981 and references therein. (b) Ikeda, Y.; Takano, K.;
Kodama, S.; Ishii, Y. Chem. Commun. 2013, 49, 11104. (c) Ma, S.; Gu, Z.
Angew. Chem., Int. Ed. 2005, 44, 7512. (d) Shi, F.; Larock, R. C. Top.
Curr. Chem. 2009, 292, 123.
(18) The kH/kD value is small but significantly larger than unity,
implying that the C−H cleavage process (1,4-H migration) would affect
the turnover-limiting step (TLS) in some way. We are thinking at
present that the C−H cleavage may be involved in the TLS or occur in
the pre-equilibrium steps of the TLS. See also: Simmons, E. M.; Hartwig,
J. F. Angew. Chem., Int. Ed. 2012, 51, 3066.
(19) Stoichiometric reaction of complex 1-Pip with PhCCPh (1
equiv) for 24 h at room temperature consumed ca. 50% of 1-Pip and
gave a complicated mixture of unidentified products and 1-Pip (see the
equiv) at room temperature was slower, which consumed only 4% of 1-
Pip after 24 h to give 9,9-dimethyl-4,5-bis(dimethylsilyl)xanthene
(xantsilH2). On the basis of these results, we proposed a catalytic
mechanism that involved the reaction of 1-R with arylalkyne in the first
step as illustrated in Scheme 2.
(20) When the reaction of PhCCPh with HSiMe(OSiMe3)2
catalyzed by 1-Pyrr (5 mol %) was conducted in the presence of ca.
20 mol % of P(NC4H8)3, the reaction rate considerably decreased. This
result implies that phosphine dissociation or coordination possibly takes
place in the TLS or in the pre-equilibrium of the TLS.
(21) (a) Ojima, I.; Clos, N.; Donovan, R. J.; Ingallina, P.
Organometallics 1990, 9, 3127. (b) Tanke, R. S.; Crabtree, R. H. J.
Am. Chem. Soc. 1990, 112, 7984.
(22) We have previously reported a dehydrogenation reaction of a
hydrido(η2-silane)ruthenium complex by alkene, which is closely related
to the last step (from G to 1-R) of the mechanism (Scheme 2). See:
Komuro, T.; Arai, T.; Kikuchi, K.; Tobita, H. Organometallics 2015, 34,
1211.
REFERENCES
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