Lewis base stabilized group 14 metalylenes

Article abstract of DOI:10.1021/om301062d

The chemistry of stable metalylenes (the heavier group 14 element analogues of carbenes) is an intriguing target of main group chemistry due to their synthetic potential and industrial application. In the present study, we report on the utilization of an abnormal N-heterocyclic carbene (aNHC) and a cyclic alkyl-amino carbene (cAAC) as a Lewis base for the syntheses of compounds aNHC·SiCl₂ (3), aNHC·SnCl₂ (4), and cAAC·SnCl₂ (5). The synthesis of silylene 3 involved the ligand-substitution reaction between NHC·SiCl₂ and an aNHC. However, compounds 4 and 5 were synthesized by the reactions of aNHC and cAAC with SnCl₂ in the molar ratio of 1:1. Compounds 3-5 are well-characterized with various spectroscopic methods and single-crystal X-ray structural analysis.

Full text of DOI:10.1021/om301062d

Note
pubs.acs.org/Organometallics
Lewis Base Stabilized Group 14 Metalylenes
Amit Pratap Singh, Prinson P. Samuel, Kartik Chandra Mondal, Herbert W. Roesky,* Navdeep S. Sidhu,
and Birger Dittrich*
Institut fur Anorganische Chemie, Georg-August-Universitat, Tammannstrasse 4, D-37077 Gottingen, Germany
̈
̈
̈
S
* Supporting Information
ABSTRACT: The chemistry of stable metalylenes (the heavier group 14 element
analogues of carbenes) is an intriguing target of main group chemistry due to their
synthetic potential and industrial application. In the present study, we report on
the utilization of an abnormal N-heterocyclic carbene (aNHC) and a cyclic alkyl-
amino carbene (cAAC) as a Lewis base for the syntheses of compounds
aNHC·SiCl2 (3), aNHC·SnCl2 (4), and cAAC·SnCl2 (5). The synthesis of
silylene 3 involved the ligand-substitution reaction between NHC·SiCl2 and an
aNHC. However, compounds 4 and 5 were synthesized by the reactions of aNHC
and cAAC with SnCl2 in the molar ratio of 1:1. Compounds 3−5 are well-characterized with various spectroscopic methods and
single-crystal X-ray structural analysis.
Scheme 1. Synthesis of Compounds 1 and 2
INTRODUCTION
■
The chemistry of heavier group 14 elements has been
developed due to the interest in comparative studies with the
lighter congener carbon.1 In recent years, the highly reactive
metalylenes (heavier group 14 element analogues of carbene)2
have attracted considerable attention due to their potential role
in the development of advanced semiconductors, and in
microelectronic engineering.3 In 1994, West et al.4 isolated
the first divalent dicoordinate N-heterocyclic silylene, which is
comparable to the N-heterocyclic carbene reported by
Arduengo et al.5 in 1991. The first monomeric stanylene was
synthesized by Engelhardt et al.6 in 1988. Since then, a number
of stable silylenes and stanylenes have been synthesized and
structurally characterized.7 Stabilization of such metalylenes is
highly dependent on the nature of the ligands. At this juncture,
N-heterocyclic carbenes (NHCs) deserve special attention
because of their excellent properties to stabilize species with the
hitherto illusive and quite unusual low valency.8 In this context,
we synthesized and structurally characterized an NHC-
stabilized dichlorosilylene (NHC·SiCl2)9 by reductive elimi-
nation of HCl from HSiCl3. Many other highly reactive
compounds containing NHCs with low-valent group 14
elements are also documented.10 In searching to modify the
NHC unit, chemists have adopted a series of strategies, such as
changing the substituents on the nitrogen atoms, varying the
backbone of the carbene, and also changing the position of the
carbene carbon in the heterocyclic ring.11 Recently, Bertrand et
al. reported on stable cyclic alkyl-amino carbenes (cAACs)12
and an abnormal N-heterocyclic carbene (aNHC).13 Exper-
imental data suggest that the aNHC is a strong nucleophile as
well as an electrophile, and may be a better substitute for
NHCs.13 In line with this argument, we recently synthesized
and structurally characterized a biradical silicon compound
(cAAC)2·SiCl2 (1)14 by a ligand-substitution reaction of
NHC·SiCl2 with cAAC (Scheme 1). The Si−C bonds in 1
were found to be electron-sharing bonds instead of a
conventional coordinate bond (donor−acceptor bond) be-
tween the NHC carbene carbon atom and the silicon atom in
NHC·SiCl2.9 In another report, we have shown the dismutation
of trichlorosilane in the presence of aNHC, resulting in the
formation of aNHC·SiH2Cl2 (2)15 under the elimination of
SiCl4. The unique synthesis and structural properties of 1 and 2
encourage us to explore the chemistry of both aNHC, and
cAAC with other heavier group 14 elements.
Herein, we report the synthesis of compounds aNHC·SiCl2
(3), aNHC·SnCl2 (4), and cAAC·SnCl2 (5) by using aNHC
and cAAC as Lewis bases. Compound 3 was synthesized by the
ligand-substitution reaction between aNHC and NHC·SiCl2.
Because of the stronger nucleophilic nature of aNHC in
comparison to that of NHC, aNHC selectively replaced NHC
from NHC·SiCl2 to afford compound 3 in toluene. However,
compounds 4 and 5 were synthesized by the reactions of
aNHC and cAAC each with SnCl2 in a 1:1 molar ratio.
Compounds 3−5 have been characterized with various
Received: November 7, 2012
Published: December 19, 2012
© 2012 American Chemical Society
354
dx.doi.org/10.1021/om301062d | Organometallics 2013, 32, 354−357

Organometallics
Note
spectroscopic methods and elemental analysis. The molecular
structures of compounds 4 and 5 were confirmed by single-
crystal X-ray analysis.
matching well with the theoretically calculated values, and
hence prove the composition of the compounds.
To establish unambiguously the structural features of
compounds 4 and 5, single-crystal X-ray structural analyses
were carried out. Suitable single crystals of both compounds
were obtained from saturated THF solutions. Both compounds
4 and 5 crystallize in the monoclinic crystal system with space
group P21/n (Table S1, Supporting Information). The
molecular structures of compounds 4 and 5 are shown in
Figures 1 and 2, respectively. The molecular structure of 4
RESULTS AND DISCUSSION
■
The reaction of abnormal N-heterocyclic carbene (aNHC) with
trichlorosilane in toluene produces dichlorosilane aNHC·-
SiH2Cl2 (2) instead of the expected dichlorosilylene
aNHC·SiCl2 (3) due to the dismutation reaction of
trichlorosilane.15 However, the synthesis of compound 1
where NHC was replaced by the cAAC encouraged us to
react NHC·SiCl2 with aNHC. In this reaction, aNHC
selectively replaced NHC from the tolulene solution of
NHC·SiCl2 to afford a mixture of compound 3 and NHC
(Scheme 2). The NHC was removed from the crude solid by
Scheme 2. Synthesis of Compounds 3 and 4
washing with n-hexane to afford pure colorless compound 3 in
a quantitative yield. Compounds 4 and 5 were synthesized by
the reactions of aNHC and cAAC with SnCl2 in a 1:1 molar
ratio (Schemes 2 and 3). Compounds 3−5 are highly soluble in
Figure 1. ORTEP representation of the molecular structure of
aNHC·SnCl2 (4). ADPs are depicted at the 50% probability level. All
C−H hydrogen atoms are omitted for clarity. Selected bond lengths
(Å) and angles (deg): Sn−C(5) 2.308(9), Sn−Cl(1) 2.427(3), Sn−
Cl(2) 2.460(3); C(5)−Sn−Cl(1) 96.9(2), C(5)−Sn−Cl(2) 89.8(2),
Cl(1)−Sn−Cl(2) 94.24(10). The crystal structure of 4 is affected by
the disorder at the tin site, with two split conformations of SnCl2
attached to aNHC (see the Supporting Information).
Scheme 3. Synthesis of Compound 5
tetrahydrofuran (THF) and less soluble in toluene and
benzene. Compounds 3−5 have been characterized by their
1H and 13C NMR spectra and show resonances for the
respective ligands. However, the positions of the resonances are
shifted when compared with those of the uncoordinated
reveals that an aNHC is coordinated to the tin atom through
the carbene center C5, whereas in the case of compound 5,
cAAC is coordinated to tin through the carbene carbon C2. In
both the compounds 4 and 5, the tin atom is surrounded by
one carbon (C5 for 4 and C2 for 5) and two chlorine (Cl1 and
Cl2) atoms, resulting in a distorted trigonal-pyramidal
geometry around the tin center. Moreover, nearly the same
bond lengths and angles were observed in compound 4 and 5.
The Sn−Cl1 and Sn−Cl2 bond lengths for compound 4 are
2.427(3) and 2.460(3) Å, respectively, while the Cl1−Sn−Cl2
bond angle is 94.24(10)°. The C5−Sn bond length is 2.308(9)
Å, which is very similar to that of other reported analogous
compounds.10c Both chlorine atoms Cl1 and Cl2 are nearly
perpendicular to the C5−Sn bond. In compound 5, the C2−Sn
bond length is 2.358(3) Å, which is about 0.05 Å longer than
the C5−Sn bond length found in 4. The Sn−Cl1 and Sn−Cl2
bond lengths for compound 5 are 2.4617(9) and 2.4691(10) Å,
respectively. The chlorine atoms Cl1 and Cl2 are showing an
angle of 94.94(3)° with the tin center. Similar to compound 4,
the chlorine atoms Cl1 and Cl2 are nearly perpendicular (92−
95°) to the C2−Sn bonds in compound 5.
1
ligands. For example, the CH proton of iPr groups in the H
NMR spectrum of 3 resonates as two septets at significantly
different positions (δ 2.85 and 2.71 ppm) when compared with
those of the free ligand (δ 2.95 and 2.73 ppm). Furthermore, to
investigate the electronic environments around the silicon (for
3) and tin (for 4 and 5) atoms, the 29Si and 119Sn NMR spectra
were measured. The 29Si NMR spectrum of compound 3
exhibits a resonance at δ 24.18 ppm, which is comparable to the
reported value (δ 19.06 ppm)9 for the analogous compound
NHC·SiCl2. This suggests that both compounds (NHC·SiCl2
and aNHC·SiCl2) have identical electronic environments
around the silicon center. The 119Sn NMR spectra of
compounds 4 and 5 show resonances at δ −60.01 and δ
−53.14 ppm, respectively. The molecular ions for 3−5 were
observed in the EI-mass spectra at m/z 638.4, 730.2, and 475.1,
respectively. The elemental analyses for compounds 3−5 are
355
dx.doi.org/10.1021/om301062d | Organometallics 2013, 32, 354−357

Organometallics
Note
(0.81 g, 1.67 mmol) at −78 °C under a nitrogen atmosphere. The
mixture was then warmed to room temperature and stirred for 3 h. All
volatiles were removed under vacuum to afford a mixture of
aNHC·SiCl2 and NHC. The NHC was removed from the solid by
washing with n-hexane (2 × 50 mL) to yield pure colorless 3 (yield:
0.89 g, 75%). mp 265 °C (dec.). Elemental analysis (%) calcd for
C39H44Cl2N2Si (638.27): C, 73.22; H, 6.93; N, 4.38. Found: C, 73.43;
H, 7.02; N, 4.25. 1H NMR (500 MHz, THF-d8, TMS, 25 °C): δ 7.77−
7.75 (m, 3H, CHar), 7.53−7.43 (m, 3H, CHar), 7.34−7.14 (m, 8H,
CHar), 7.08−6.93 (m, 2H, CHar), 2.85 (sept, 2H, Ar−CH(CH3)2),
2.71 (sept, 2H, Ar−CH(CH3)2), 1.40 (d, J = 6.8 Hz, 6H, CH3), 0.98
(d, J = 6.8 Hz, 6H, CH3), 0.89 (d, J = 6.8 Hz, 6H, CH3), 0.87 (d, J =
6.8 Hz, 6H, CH3) ppm. 13C NMR (500 MHz, THF-d8, TMS, 25 °C):
δ 144.2, 143.2, 140.2, 139.9, 138.3, 136.4, 133.6, 130.8, 130.1, 129.6,
129.2, 128.5, 128.1, 127.9, 126.5, 126.2, 123.9, 29.5 (CHCH3), 29.1
(CHCH3), 25.9(CH3), 24.5 (CH3), 24.0 (CH3), 22.5 (CH3) ppm. 29Si
NMR (500 MHz, THF-d8, TMS, 25 °C): δ 24.18 ppm. EI-MS: m/z
638.4 (M+) (100%).
Synthesis of aNHC·SnCl2 (4). For the synthesis of compound 4,
the toluene solution of aNHC (1.00 g, 1.85 mmol) was treated with
solid SnCl2 (0.36 g, 1.86 mmol) under a nitrogen atmosphere at −78
°C. The mixture was then warmed to room temperature and stirred for
6 h. All volatiles were removed under vacuum to afford a colorless
crude product. The crude product was dissolved in a minimum
amount of THF and filtered through a pad of Celite of a medium
porosity frit. The filtrate was stored for 2 days at room temperature to
give colorless crystals of 4 suitable for single-crystal X-ray structural
analysis (yield: 1.10 g, 81%). mp 278 °C (dec.). Elemental analysis
(%) calcd for C39H44Cl2N2Sn (730.19): C, 64.13; H, 6.07; N, 3.84.
Figure 2. ORTEP representation of the molecular structure of
cAAC·SnCl2 (5). ADPs are depicted at the 50% probability level.
Hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and
angles (deg): Sn−C(2) 2.358(3), Sn−Cl(1) 2.4617(9), Sn−Cl(2)
2.4691(10); C(2)−Sn−Cl(1) 92.30(7), C(2)−Sn−Cl(2) 94.20(7),
Cl(1)−Sn−Cl(2) 94.94(3).
1
Found: C, 64.45; H, 5.95; N, 3.97. H NMR (500 MHz, THF-d8,
TMS, 25 °C): δ 7.61−7.57 (m, 3H, CHar), 7.53−7.44 (m, 3H, CHar),
7.39−7.20 (m, 8H, CHar), 7.16−7.01 (m, 2H, CHar), 2.91−2.62 (m,
4H, Ar−CH(CH3)2), 1.45 (d, J = 6.8 Hz, 6H, CH3), 1.03 (d, J = 6.8
Hz, 6H, CH3), 0.99 (d, J = 6.8 Hz, 6H, CH3), 0.93 (d, J = 6.8 Hz, 6H,
CH3) ppm. 13C NMR (500 MHz, THF-d8, TMS, 25 °C): δ 155.8,
140.4, 138.2, 135.4, 133.2, 130.1, 129.6, 125.2, 123.3, 120.1, 118.4,
115.4, 113.8, 110.2, 109.2, 106.3, 103.1, 101.4, 29.7 (CHCH3), 29.5
(CHCH3), 25.2(CH3), 24.3 (CH3), 24.1 (CH3), 23.9 (CH3) ppm.
119Sn NMR (500 MHz, THF-d8, TMS, 25 °C): δ −60.01 ppm. EI-MS:
m/z 730.2 (M+) (100%).
SUMMARY
■
The synthesis and reactivity of compounds with heavier group
14 elements is a rapidly growing field in chemistry because of
their extensive use in various applications. In the present study,
we have shown that abnormal N-heterocyclic carbene (aNHC)
easily replaces the N-heterocyclic carbene (NHC) molecule
from a toluene solution of NHC·SiCl2 to afford compound 3.
This experiment proves the strong nucleophilic and electro-
philic nature of aNHC in comparison to that of NHC.
Compounds 4 and 5 were synthesized by the reactions of
aNHC and cAAC with SnCl2 each in a 1:1 molar ratio.
Compounds 3−5 were well-characterized with various
spectroscopic methods and elemental analysis. The structural
analysis of compounds 4 and 5 showed that tin is coordinated
to the respective carbene, resulting in a distorted trigonal-
pyramidal geometry. Compounds 3−5 might prove to be
promising candidates for the synthesis of other potentially
important derivatives with low-valent group 14 elements. Such
types of investigations will be reported in due course from our
laboratory.
Synthesis of cAAC·SnCl2 (5). For the synthesis of compound 5,
the solvent THF (40 mL) was added to a mixture of cAAC (1.00 g,
3.50 mmol) and solid SnCl2 (0.67 g, 3.50 mmol) under a nitrogen
atmosphere at −78 °C. The mixture was then warmed to room
temperature and stirred for 3 h. The reaction mixture was filtered
through a pad of Celite of a medium porosity frit. The volume of
filtrate was reduced up to 50% of the original volume and then stored
for 2 days at −32 °C to give the colorless crystals of 5 suitable for
single-crystal X-ray structural analysis (yield: 1.20 g, 72%). mp 255 °C
(dec.). Elemental analysis (%) calcd for C20H31Cl2NSn (475.09): C,
1
50.65; H, 6.58; N, 2.95. Found: C, 50.55; H, 6.79; N, 3.05. H NMR
(500 MHz, THF-d8, TMS, 25 °C): δ 7.55−7.39 (m, 3H, CHar), 2.95−
2.84 (sept, 2H, Ar−CH(CH3)2), 2.19 (s, 2H, CH2), 1.87 (s, 6H, CH3),
1.50 (s, 6H, CH3), 1.37 (d, J = 6.8 Hz, 6H, CH3), 1.29 (d, J = 6.8 Hz,
6H, CH3) ppm. 13C NMR (500 MHz, THF-d8, TMS, 25 °C): δ 145.8,
132.7, 127.9, 123.6, 119.2, 85.5, 49.1, 30.4, 28.4, 26.5, 24.4 ppm. 119Sn
NMR (500 MHz, THF-d8, TMS, 25 °C): δ −53.14 ppm. EI-MS: m/z
475.1 (65%) (M+), 405.4 (M+ − 2Cl) (100%).
EXPERIMENTAL SECTION
■
All manipulations were performed in a dry and oxygen-free
atmosphere (N2) using standard Schlenk-line techniques and inside
a MBraun MB 150-GI glovebox maintained at or below 1 ppm of O2
and H2O. All solvents were dried by a MBraun solvent purification
system prior to use. Compound NHC·SiCl2, cyclic alkyl-amino
carbene (cAAC) and abnormal N-heterocyclic carbene (aNHC)
were synthesized by the reported procedures.9,12,13 Other chemicals
ASSOCIATED CONTENT
■
S
* Supporting Information
were purchased and used as received. The H, 13C, and 29Si NMR
1
CIFs CCDC Nos. 896601 (4) and 896602 (5) and crystal
structure determination. This material is available free of charge
via the Internet at http://pubs.acs.org.
spectra were recorded on a Bruker Avance DRX instrument (300 or
500 MHz). The chemical shifts δ are given in parts per million with
tetramethylsilane as an external standard. Elemental analyses were
performed by the Analytisches Labor des Instituts fur Anorganische
̈
AUTHOR INFORMATION
■
Chemie der Universitat Gottingen.
̈
̈
Corresponding Author
*E-mail: hroesky@gwdg.de (H.W.R.), bdittri@gwdg.de (B.D.).
Synthesis of aNHC·SiCl2 (3). Compound 3 was synthesized by the
reaction of aNHC (1.00 g, 1.85 mmol) in toluene with NHC·SiCl2
356
dx.doi.org/10.1021/om301062d | Organometallics 2013, 32, 354−357

Organometallics
Note
45, 1348−1352. (c) Hahn, F. E.; Jahnke, M. C. Angew. Chem., Int. Ed.
2008, 47, 3122−3172.
Notes
The authors declare no competing financial interest.
(9) Ghadwal, R. S.; Roesky, H. W.; Merkel, S.; Henn, J.; Stalke, D.
Angew. Chem., Int. Ed. 2009, 48, 5683−5686.
ACKNOWLEDGMENTS
■
(10) (a) Wang, Y.; Xie, Y.; Wei, P.; King, R. B.; Schaefer, H. F., III;
Schleyer, P.; von, R.; Robinson, G. H. Science 2008, 321, 1069−1071.
(b) Thimer, K. C.; Ibrahim Al-Rafia, S. M.; Ferguson, M. J.;
McDonald, R.; Rivard, E. Chem. Commun. 2009, 7119−7121.
(c) Bantu, B.; Pawar, G. M.; Decker, U.; Wurst, K.; Schmidt, A. M.;
Buchmeiser, M. R. Chem.Eur. J. 2009, 15, 3103−3109. (d) Filippou,
A. C.; Chernov, O.; Schnakenburg, G. Angew. Chem., Int. Ed. 2009, 48,
5687−5690.
H.W.R. and B. D. thank the Deutsche Forschungsgemeinschaft
for financial support.
DEDICATION
■
This paper is dedicated to Professor Heinz-Dieter Fenske on
the occasion of his 70th birthday.
(11) (a) Kuhl, O. Coord. Chem. Rev. 2009, 253, 2481−2492.
̈
(b) Lavallo, V.; Mafhouz, J.; Canac, Y.; Donnadieu, B.; Schoeller, W.
W.; Bertrand, G. J. Am. Chem. Soc. 2004, 126, 8670−8671. (c) Frey, G.
D.; Lavallo, V.; Donnadieu, B.; Schoeller, W. W.; Bertrand, G. Science
2007, 316, 439−441.
REFERENCES
■
(1) (a) Nava, M.; Reed, C. A. Organometallics 2011, 30, 4798−4800.
(b) Muller, T. Adv. Organomet. Chem. 2005, 53, 155−215. (c) West,
̈
R.; Moser, D. F.; Guzei, I. A.; Lee, G.-H.; Naka, A.; Li, W.; Zabula, A.;
Bukalov, S.; Leites, L. Organometallics 2006, 25, 2709−2711.
(d) Willey, G. R.; Somasundaram, U.; Aris, D. R.; Errington, W.
Inorg. Chim. Acta 2001, 315, 191−195. (e) Ejfler, J.; Szafert, S.; Jiao,
H.; Sobota, P. New J. Chem. 2002, 26, 803−805. (f) Cheng, F.; Davis,
M. F.; Hector, A. L.; Levason, W.; Reid, G.; Webster, M.; Zhang, W.
Eur. J. Inorg. Chem. 2007, 2488−2495. (g) Cheng, F.; Davis, M. F.;
Hector, A. L.; Levason, W.; Reid, G.; Webster, M.; Zhang, W. Eur. J.
Inorg. Chem. 2007, 4897−4905. (h) Cowley, A. H. Acc. Chem. Res.
1984, 17, 386−392. (i) Mandal, S. K.; Roesky, H. W. Chem. Commun.
2010, 46, 6016−6041. (j) Singh, A. P.; Roesky, H. W.; Carl, E.; Stalke,
D.; Demers, J.-P.; Lange, A. J. Am. Chem. Soc. 2012, 134, 4998−5003.
(k) Ibrahim Al-Rafia, S. M.; Malcolm, A. C.; Liew, S. K.; Ferguson, M.
J.; Rivard, E. J. Am. Chem. Soc. 2011, 133, 777−779.
(12) Lavallo, V.; Canac, Y.; Prasang, C.; Donnadieu, B.; Bertrand, G.
̈
Angew. Chem., Int. Ed. 2005, 44, 5705−5709.
(13) Aldeco-Perez, E.; Rosenthal, A. J.; Donnadieu, B.;
Parameswaran, P.; Frenking, G.; Bertrand, G. Science 2009, 326,
556−559.
(14) Mondal, K. C.; Roesky, H. W.; Schwarzer, M. C.; Frenking, G.;
Tkach, I.; Wolf, H.; Kratzert, D.; Herbst-Irmer, R.; Niepotter, B.;
̈
Stalke, D. Angew. Chem., Int. Ed. 2012. DOI: 10.1002/anie.201204487.
(15) Singh, A. P.; Ghadwal, R. S.; Roesky, H. W.; Holstein, J. J.;
Dittrich, B.; Demers, J.-P.; Chevelkov, V.; Lange, A. Chem. Commun
2012, 48, 7574−7576.
(2) (a) Driess, M.; Grutzmacher, H. Angew. Chem., Int. Ed. 1996, 35,
̈
828−856. (b) Weidenbruch, M. Eur. J. Inorg. Chem. 1999, 373−381.
(c) Tokitoh, N.; Okazaki, R. Coord. Chem. Rev. 2000, 210, 251−277.
(d) Hill, N. J.; West, R. J. Organomet. Chem. 2004, 689, 4165−4183.
(e) Kuhl, O. Coord. Chem. Rev. 2004, 248, 411−427. (f) Ottosson, H.;
̈
Steel, P. G. Chem.Eur. J. 2006, 12, 1576−1585. (g) Nagendran, S.;
Roesky, H. W. Organometallics 2008, 27, 457−492. (h) Zabula, A. V.;
Hahn, F. E. Eur. J. Inorg. Chem. 2008, 5165−5179. (i) Mizuhata, Y.;
Sasamori, T.; Tokitoh, N. Chem. Rev. 2009, 109, 3479−3511. (j) Asay,
M.; Jones, C.; Driess, M. Chem. Rev. 2011, 111, 354−396.
(3) (a) Bazargan, S.; Heinig, N. F.; Pradhan, D.; Leung, K. T. Cryst.
Growth Des. 2011, 11, 247−255. (b) Hahn, N. T.; Mullins, C. B. Chem.
Mater. 2010, 22, 6474−6482. (c) Semenov, S. N.; Blacque, O.; Fox, T.;
Venkatesan, K.; Berke, H. Organometallics 2010, 29, 6321−6328.
(d) Bundhun, A.; Ramasami, P.; Gaspar, P. P.; Schaefer, H. F., III
Inorg. Chem. 2012, 51, 851−863.
(4) Denk, M.; Lennon, R.; Hayashi, R.; West, R.; Belyakov, A. V.;
Verne, H. P.; Haaland, A.; Wagner, M.; Metzler, N. J. Am. Chem. Soc.
1994, 116, 2691−2692.
(5) Arduengo, A. J.; Harlow, R. L.; Kline, M. J. Am. Chem. Soc. 1991,
113, 361−363.
(6) Engelhardt, L. M.; Jolly, B. S.; Lappert, M. F.; Raston, C. L.;
White, A. L. J. Chem. Soc., Chem. Commun. 1988, 336−338.
(7) (a) Haaf, M.; Schmedake, T.; West, R. Acc. Chem. Res. 2000, 33,
704−714. (b) Kira, M. Chem. Commun. 2010, 46, 2893−2903.
(c) Yao, S.; Xiong, Y.; Driess, M. Organometallics 2011, 30, 1748−
1767. (d) So, C.-W.; Roesky, H. W.; Magull, J.; Oswald, R. B. Angew.
Chem., Int. Ed. 2006, 45, 3948−3950. (e) Sen, S. S.; Roesky, H. W.;
Stern, D.; Henn, J.; Stalke, D. J. Am. Chem. Soc. 2010, 132, 1123−
1126. (f) Sen, S. S.; Khan, S.; Samuel, P. P.; Roesky, H. W. Chem. Sci.
2012, 3, 659−682. (g) Driess, M.; Yao, S.; Brym, M.; van Wullen, C.;
̈
Lentz, D. J. Am. Chem. Soc. 2006, 128, 9628−9629. (h) Kong, L.;
Zhang, J.; Song, H.; Cui, C. Dalton Trans. 2009, 5444−5446.
(i) Yamaguchi, T.; Sekiguchi, A.; Driess, M. J. Am. Chem. Soc. 2010,
132, 14061−14063. (j) Neumann, W. P. Chem. Rev. 1991, 91, 311−
334. (k) McBurnett, B. G.; Cowley, A. H. Chem. Commun. 1999, 17−
18. (l) Jones, J. N.; Cowley, A. H. Chem. Commun. 2005, 1300−1302.
(8) (a) Bourissou, D.; Guerret, O.; Gabbaï, F. P.; Bertrand, G. Chem.
Rev. 2000, 100, 39−92. (b) Hahn, F. E. Angew. Chem., Int. Ed. 2006,
357
dx.doi.org/10.1021/om301062d | Organometallics 2013, 32, 354−357