Organometallics
Communication
corresponds to a four-coordinate boron atom, revealing no
multiple bonds connected to it. The molecular structure of 4
has been determined by X-ray single-crystal analysis, which is
shown in Figure 5. The newly formed B1−O1−C4−N2 four-
REFERENCES
■
(1) For selected references, see: (a) Loudet, A.; Burgess, K. Chem.
Rev. 2007, 107, 4891. (b) Bosdet, M. J. D.; Piers, W. E. Can. J. Chem.
2009, 87, 8. (c) Wakamiya, A.; Taniguchi, T.; Yamaguchi, S. Angew.
Chem., Int. Ed. 2006, 45, 3170. (d) Yoshino, J.; Kano, N.; Kawashima,
T. Chem. Commun. 2007, 559. (e) Ishida, N.; Moriya, T.; Goya, T.;
Murakami, M. J. Org. Chem. 2010, 75, 8709.
(2) For leading references, see: (a) Rao, Y. L.; Amarne, H.; Zhao, S.-
B.; McCormick, T. M.; Martic, S.; Sun, Y.; Wang, R.-Y.; Wang, S. J.
Am. Chem. Soc. 2008, 130, 12898. (b) Baik, C.; Hudson, Z. M.;
Amarne, H.; Wang, S. J. Am. Chem. Soc. 2009, 131, 14549. (c) Amarne,
H.; Baik, C.; Murphy, S. K.; Wang, S. Chem. Eur. J. 2010, 16, 4750.
(d) Baik, C.; Murphy, S. K.; Wang, S. Angew. Chem., Int. Ed. 2010, 49,
8224. (e) Schmid, G.; Schutz, M. Organometallics 1992, 11, 1789.
̈
(f) Liu, S.-Y.; Lo, M. M.-C.; Fu, G. C. Angew. Chem., Int. Ed. 2002, 41,
174. (g) Fang, X.; Assoud, J. Organometallics 2008, 27, 2408. (h) Fang,
X.; Li, X.; Hou, Z.; Assoud, J.; Zhao, R. Organometallics 2009, 28, 517.
(i) Ly, H. V.; Moilanen, J.; Tuononen, H. M.; Parvez, M.; Roesler, R.
Chem. Commun. 2011, 47, 8391.
(3) (a) Kinjo, R.; Donnadieu, B.; Celik, M. A.; Frenking, G.;
Bertrand, G. Science 2011, 333, 610. (b) Segawa, Y.; Yamashita, M.;
Nozaki, K. Science 2006, 314, 113. (c) Segawa, Y.; Suzuki, Y.;
Yamashita, M.; Nozaki, K. J. Am. Chem. Soc. 2008, 130, 16069.
(d) Bissinger, P.; Braunschweig, H.; Kraft, K.; Kupfer, T. Angew.
Chem., Int. Ed. 2011, 50, 4704. (e) Braunschweig, H.; Chiu, C.-W.;
Radacki, K.; Kupfer, T. Angew. Chem., Int. Ed. 2010, 49, 2041.
(f) Bissinger, P.; Braunschweig, H.; Damme, A.; Dewhurst, R. D.;
Kupfer, T.; Radacki, K.; Wagner, K. J. Am. Chem. Soc. 2011, 133,
Figure 5. Ortep drawing of 4 with 30% probability ellipsoids.
Hydrogen atoms have been omitted for clarity. Selected bond lengths
(Å) and angles (deg): B1−N2 = 1.543(2), B1−O1 = 1.505(2), C4−
O1 = 1.3598(18), C4−N2 = 1.368(2), C4−O2 = 1.2119(18), B1−N1
= 1.597(2), B1−C1 = 1.601(2), N1−C3 = 1.3058(19), C1−C2 =
1.346(2), C2−C3 = 1.463(2); N2−B1−O1 = 85.79(11), B1−O1−C4
= 88.49(11), O1−C4−N2 = 98.98(12), B1−N2−C4 = 86.63(11),
N1−B1−C1 = 99.46(12).
̀ ̂
19044. (g) Curran, D. P.; Boussonniere, A.; Geib, S. J.; Lacote, E.
Angew. Chem., Int. Ed. 2012, 51, 1602.
(4) (a) Cui, C.; Roesky, H. W.; Schmidt, H.-G.; Noltemeyer, M.;
Hao, H.; Cimpoesu, F. Angew. Chem., Int. Ed. 2000, 39, 4274.
(b) Hardman, N. J.; Eichler, B. E.; Power, P. P. Chem. Commun. 2000,
1991. (c) Hill, M. S.; Hitchcock, P. B. Chem. Commun. 2004, 1818.
(5) (a) Wang, H.; Zhang, J.; Hu, H.; Cui, C. J. Am. Chem. Soc. 2010,
132, 10998. (b) Wang, Y.; Hu, H.; Zhang, J.; Cui, C. Angew. Chem., Int.
Ed. 2011, 50, 2816. (c) Xie, L.; Hu, H.; Cui, C. Organometallics 2012,
31, 4405.
(6) Prior to the following publication, we discussed the reduction
chemistry of L′BF2 with Prof. Nozaki, and our group focused on the
chemistry of the five-membered iminoboranes while the Nozaki group
studied the six-membered ring radical thereafter. See: Aramaki, Y.;
Omiya, H.; Yamashita, M.; Nakabayashi, K.; Ohkoshi, S.-I.; Nozaki, K.
J. Am. Chem. Soc. 2012, 134, 19989.
membered ring in 4 is practically planar (the sum of the angles
is 359.9°) and is perpendicular to the BC3N backbone. The
B1−N2 bond (1.543(2) Å) is remarkably lengthened in
comparison to that in 2 (1.3396(19) Å) into the range for a
single bond, illustrating the participation of the B−N π bond in
this reaction.
In summary, the first intramolecular donor stabilized π-
conjugated iminoboranes 2 and 2′ have been prepared and
structurally characterized. Reactions of 2 with NHC yielded 3,
indicating an electrophilic α-carbon atom in 2. 4 was isolated by
[2 + 2] cycloaddition of 2 with CO2, which underwent CO2
elimination at high temperature. DFT calculations on 2
strongly support the interaction of the exocyclic BN double
bond with the cyclic π-conjugated system. Further reactivity
studies of 2 are currently in progress.
(7) (a) Haase, M.; Klingebiel, U. Angew. Chem., Int. Ed. Engl. 1985,
24, 324. (b) Luthin, W.; Elter, G.; Heine, A.; Stalke, D.; Sheldrick, G.
M.; Meller, A. Z. Anorg. Allg. Chem. 1992, 608, 147.
(8) Rivard, E.; Merrill, W. A.; Fettinger, J. C.; Wolf, R.; Spikes, G. H.;
Power, P. P. Inorg. Chem. 2007, 46, 2971.
ASSOCIATED CONTENT
* Supporting Information
Text, figures, tables, and CIF files giving synthetic procedures
and characterization data for compounds 1−4, crystallographic
data for compounds 2−4, and DFT calculations on 2. This
material is available free of charge via the Internet at http://
(9) (a) Tomson, N. C.; Arnold, J.; Bergman, R. G. Organometallics
2010, 29, 5010. (b) Woodul, W. D.; Richards, A. F.; Stasch, A.; Driess,
M.; Jones, C. Organometallics 2010, 29, 3655. (c) Basuli, F.; Huffman,
J. C.; Mindiola, D. J. Inorg. Chim. Acta 2007, 360, 246. (d) Bailey, B.
C.; Basuli, F.; Huffman, J. C.; Mindiola, D. J. Organometallics 2006, 25,
3963. (e) Basuli, F.; Kilgore, U. J.; Brown, D.; Huffman, J. C.;
Mindiola, D. J. Organometallics 2004, 23, 6166. (f) Li, X.; Cheng, X.;
Song, H.; Cui, C. Organometallics 2007, 26, 1039. (g) Li, J.; Li, X.;
Huang, W.; Hu, H.; Zhang, J.; Cui, C. Chem. Eur. J. 2012, 18, 15263.
(10) Braunschweig, H.; Radacki, K.; Rais, D.; Uttinger, K. Angew.
Chem., Int. Ed. 2006, 45, 162.
■
S
AUTHOR INFORMATION
Corresponding Author
Notes
■
́
́
(11) (a) Rodrıguez-Mendez, M. L.; Souto, J.; de Saja, J. A.; Aroca, R.
J. Mater. Chem. 1995, 5, 639. (b) Steinert, M.; Acker, J.; Krause, M.;
Oswald, S.; Wetzig, K. J. Phys. Chem. B 2006, 110, 11377. (c) Guo, Z.;
Kim, G.-H.; Shin, I.; Yoon, J. Biomaterials 2012, 33, 7818. (d) Zhou,
Y.; Yang, Z.; Xu, M. Anal. Methods 2012, 4, 2711.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
(12) Furstner, A.; Alcarazo, M.; Goddard, R.; Lehmann, C. W. Angew.
̈
We are grateful to the National Natural Science Foundation of
China and the 973 program (Grant No. 2012CB821600) for
financial support.
Chem., Int. Ed. 2008, 47, 3210.
(13) Mannig, D.; Narula, C. K.; Noth, H.; Wietelmann, U. Chem. Ber.
̈
̈
1985, 118, 3748.
6878
dx.doi.org/10.1021/om4008407 | Organometallics 2013, 32, 6875−6878