Synthesis and structure of 9,10-bis(2,4,6-triisopropylphenyl)-9,10-dihydro- 9,10-disilaanthracene

Article abstract of DOI:10.1016/j.jorganchem.2010.10.010

We prepared a 9,10-dihydro-9,10-disilaanthracene (DSA) derivative 4 bearing a bulky aryl substituent, a 2,4,6-triisopropylphenyl (Tip) group, on the silicon atoms via a Wurtz-type coupling reaction between two molecules of (2-chlorophenyl)(2,4,6-triisopro

Full text of DOI:10.1016/j.jorganchem.2010.10.010

Journal of Organometallic Chemistry 696 (2011) 982e985
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Note
Synthesis and structure of 9,10-bis(2,4,6-triisopropylphenyl)-9,10-dihydro-
9,10-disilaanthracene
*
*
Makoto Oba , Tomohiro Kondo, Kazuhito Tanaka, Shinichi Koguchi, Kozaburo Nishiyama
Department of Materials Chemistry, Tokai University, 317 Nishino, Numazu, Shizuoka 410-0395, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
We prepared a 9,10-dihydro-9,10-disilaanthracene (DSA) derivative 4 bearing a bulky aryl substituent,
a 2,4,6-triisopropylphenyl (Tip) group, on the silicon atoms via a Wurtz-type coupling reaction between
two molecules of (2-chlorophenyl)(2,4,6-triisopropylphenyl)silane (3) in a head-to-tail fashion. The
structural determination of cis-4 and trans-4 was examined using 1H NMR spectroscopy and theoretical
calculations. In addition, the molecular structure of cis-4 was unambiguously determined by X-ray
crystallography. The tricyclic DSA skeleton of cis-4 adopts a folded structure with a boat-like central ring
in which the rotation about the SieTip bond is restricted. In contrast, theoretical calculations suggest that
the tricyclic DSA skeleton of trans-4 has an almost planar structure.
Received 17 August 2010
Accepted 5 October 2010
Available online 13 October 2010
Keywords:
Disilaanthracene
Bulky substituent
Wurtz-type coupling
Crystal structure
Theoretical calculations
Ó 2010 Elsevier B.V. All rights reserved.
1. Introduction
2. Results and discussion
9,10-Dihydro-9,10-disilaanthracenes (DSAs) have attracted
considerable attention as precursors of organosilicon reactive
intermediates such as silyl anions [1,2] and silyl radicals [3]. We
[4,5] and Chatgilialoglu and coworkers [6] independently reported
that DSA derivatives can be used as radical-reducing agents, and the
DSA framework is essential to generate the silyl radical efficiently
[7]. An important goal in this area is the synthesis of 9,10-dis-
ilaanthracene, which is a novel silaaromatic compound. There have
been some reports on the transient generation of the related
9-silaanthracene [8e10] and 1,4-disilabenzene [11e14]. We also
reported the thermal generation and chemical trapping of the
transient 9-silaanthracenes [15]. In 2002, Tokitoh and coworkers
successfully isolated 9-silaanthracene, which was kinetically
stabilized by a bulky substituent [16]. However, there have been no
reports on the isolation or chemical trapping of the disilaaromatic
9,10-disilaanthracene. A simple route to 9,10-disilaanthracene
involves the thermal extrusion of molecular hydrogen from the
corresponding dihydride (DSA). In addition, the existence of bulky
substituents on the silicon atoms is expected to improve the
stability of the reactive silaaromatic species.
Generally, the DSA framework is constructed through a halo-
genemetal exchange reaction of bis(2-halophenyl)silane followed
by ring closure with an appropriate chlorosilane or hydrosilane (see
Scheme 1, route A) [17,18]. However, our initial attempt to obtain bis
(2-chlorophenyl)(2,4,6-triisopropylphenyl)silane (2) via a coupling
reaction of (2,4,6-triisopropylphenyl)silane (TipSiH3) with two
equivalents of (2-chlorophenyl)lithium (prepared by lithiation of
1-bromo-2-chlorobenzene (1) at ꢀ95 ꢁC) was unsuccessful, prob-
ably because of steric effects. Instead, we obtained a 1:1 coupling
product 3 in a 79% yield. Therefore, we focused our attention to the
Wurtz-type coupling between two molecules of 2-chlor-
ophenylsilane 3; Gilman and coworkers had previously synthesized
some DSA derivatives via this reaction [19]. When the intermo-
lecular cyclization reaction of 3 was performed using molten
sodium in refluxing toluene, 9,10-bis(2,4,6-triisopropylphenyl)-
9,10-dihydro-9,10-disilaanthracene (4) was obtained as a 43:57
mixture of the cis and trans isomers in a 21% yield. Cis-4 is ther-
modynamically more stable than the trans isomer by 1.13 kcal/mol
according to calculations at the B3LYP/6-31G(d,p) level of theory, as
described below. The slight predominant formation of trans-4 can
be attributed to the kinetically controlled ring closure reaction, as
observed in the synthesis of the corresponding 9,10-di-tert-butyl
derivatives reported by Kyushin and coworkers [3].
In this paper, we report the synthesis and structure of 9,10-bis(2,4,6-
triisopropylphenyl)-9,10-dihydro-9,10-disilaanthracene (4), the first
DSA derivative bearing bulky aryl substituents on the silicon atoms.
Cis-4 and trans-4 were partially separated by silica gel column
chromatography and were isolated in 7% and 9% yields, respec-
tively. Characterizations of these new DSA derivatives included 1H,
13C, and 29Si NMR; IR; MS; and elemental analyses. In particular,
* Corresponding authors. Tel.: þ81 55 968 1111; fax: þ81 55 968 1155.
E-mail address: moba@tokai-u.jp (M. Oba).
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.10.010

M. Oba et al. / Journal of Organometallic Chemistry 696 (2011) 982e985
983
indicating the restricted SieTip bond rotation. The through-space
distances of these hydrogens in the solid phase were 2.202 Å and
2.223 Å for H1eH13 and H2eH50, respectively, which are shorter
than the sum of van der Waals radii (2.4 Å). These findings indi-
cated that the solution structure of cis-4 is rigid and almost iden-
tical to the crystal structure.
In contrast, the 1H NMR spectrum of trans-4 indicated twotypes of
isopropyl groups over the observed temperature range –90e22 ꢁC),
though the signals assigned to the ortho isopropyl groups were rather
broad even at 22 ꢁC, probably because of slow rotation about the
SieTip bond. The above observation indicates the chemical equiva-
lency of the twoTip groups as well as the two ortho isopropyl groups.
It is not clear whether the reason for the chemical equivalency of the
two Tip groups is rapid ring-flapping of the boat-like central ring or
a rigid chair-like conformation of the central ring as observed in the
trans-9,10-di-tert-butyl derivative [3].
X-ray crystallographic analysis of trans-4 is expected to resolve
the above mentioned uncertainty; however, our repeated
attempts to refine the structure to a satisfactory resolution failed.
Therefore, we carried out theoretical calculations on cis-4 and
trans-4 using Gaussian 03 [22]. The geometries were fully opti-
mized and characterized by frequency analysis at the B3LYP/6-
31G(d,p) level. Fig. 2 shows the results. Including the zero-point
vibrational energy (ZPVE) correction scaled by 0.9804 [23], cis-4
is 1.13 kcal/mol more stable than trans-4. The calculated
stretching vibrational frequencies of the SieH bond in cis-4 and
trans-4 are 2148 and 2132 cmꢀ1 (scaled by 0.9613 [24]), respec-
tively, which are in good agreement with the experimental data
(2150 cmꢀ1 for cis-4 and 2124 cmꢀ1 for trans-4). The optimized
structure of cis-4 is in good agreement with the X-ray structure,
also validating the calculations. Unlike cis-4, the DSA ring of
trans-4 is almost planar (mean deviation 0.032 Å). The two silicon
atoms are slightly displaced above and below the DSA plane, and
the central ring adopts a flat chair conformation with the two Tip
groups in pseudoequatorial positions. These results are consistent
with the observations concerning the chemical equivalency of the
Tip groups.
Scheme 1. Preparation of DSA 4. Reagents and conditions: (i) BuLi, THF, ꢀ95 ꢁC, then
TipSiH3, 79%; (ii) Na, toluene, reflux, 21%. Tip ¼ 2,4,6-triisopropylphenyl.
X-ray crystallographic analysis unambiguously confirmed the
structure of cis-4.
Fig. 1 illustrates the crystal structure of cis-4. The central ring
of DSA adopts a boat-like conformation in which each silicon
atom has a pseudoaxial hydrogen and a pseudoequatorial Tip
group. The phenyl groups of the Tip groups are oriented
perpendicular to the C1eC6eC7eC12 plane. The tricyclic DSA
framework has a folded structure with a dihedral angle (also
known as a butterfly angle) of 157ꢁ, which is within the range of
reported values for similar compounds (9,9,10,10-tetramethyl-
9,10-dihydro-9,10-disilaanthracene [20] and 9,10-dihydro-9,10-
disilaanthracene, 156ꢁ [21]; cis-9,10-di-tert-butyl-9,10-dihydro-
9,10-disilaanthracene, 161ꢁ [3]).
In the 1H NMR spectrum of cis-4, we observed three types of
isopropyl groups over the observed temperature range (22e110 ꢁC).
The assignment of proton resonances was achieved by NOESY and
decoupling experiments. The two ortho isopropyl substituents of
the Tip group hinder the rotation about the SieTip bond and are
discriminated on the NMR time scale. As shown in Fig. 1, one of the
ortho isopropyl groups lies inside the folded DSA framework and
therefore within its shielding region. As a result, the methyl proton
Since the obtained DSA derivative is expected to serve as
a potential precursor for a novel silaaromatic 9,10-disilaanthracene,
we performed flow thermolysis of cis-4 in the presence of various
trapping reagents. However, we were unable to isolate the products
that would indicate the formation of the expected silaaromatics.
Further investigations of the generation of 9,10-disilaanthracene
are ongoing.
signal of the internal isopropyl group resonated at a higher field (
d
0.66) to some degree. Furthermore, we observed an unexpected
HeH long-range coupling (ca. 1 Hz) between SieH and the methine
proton of the external isopropyl group through five bonds, also
Fig. 1. X-ray crystal structure of cis-4. Hydrogen atoms except for H1, H2, H13, and H50 are omitted for clarity. Selected bond distances [Å] and angles [ꢁ]: Si1eH1 1.433, Si2eH2
1.355, Si1eC1 1.879(2), Si1eC12 1.882(2), Si1eC13 1.898(2), Si2eC6 1.872(2), Si2eC7 1.884(2), Si2eC28 1.885(2), C1eSi1eH1 107.1, C12eSi1eH1 105.3, C13eSi1eH1 111.1,
C6eSi2eH2 105.9, C7eSi2eH2 105.8, C28eSi2eH2 112.0, C1eSi1eC12 109.95(11), C1eSi1eC13 110.29(11), C12eSi1eC13 112.87(9), C6eSi2eC7 110.45(10), C6eSi2eC28 112.66(11),
C7eSi2eC28 109.76(10).

984
M. Oba et al. / Journal of Organometallic Chemistry 696 (2011) 982e985
Fig. 2. Optimized structures and ZPVE-corrected relative energies of cis-4 and trans-4 computed at the B3LYP/6-31G(d,p) level. Hydrogen atoms, except those attached to the silicon
atoms, are omitted for clarity.
3. Conclusion
1H). 13C NMR
d 23.8, 24.4, 34.3, 34.4, 121.1, 123.2, 126.1, 128.7, 131.3,
133.1, 137.6, 141.4, 151.5, 156.4. 29Si NMR
d
ꢀ54.6. IR (KBr) nSieH
We have synthesized the highly crowded 9,10-bis(2,4,6-
triisopropylphenyl)-9,10-dihydro-9,10-disilaanthracene (4) via the
intermolecular Wurtz-type coupling of 2-chlorophenylsilane
derivative 3. The structures of cis-4 and trans-4 were confirmed
using X-ray crystallography, 1H NMR spectroscopy, and theoretical
calculations and found to have different features. The central ring of
cis-4 has a boat-like conformation, whereas that of trans-4 is almost
planar. The introduction of a Tip group provides steric crowding
around the silicon atom; in particular, the rotation about the SieTip
bond of the cis isomer is significantly restricted even in solution.
2164 cmꢀ1. HRMS m/z 344.1719 (Mþ, calcd for C21H29ClSi 344.1727).
Anal. Calcd for C21H29ClSi: C, 73.11; H, 8.47. Found C, 73.11; H, 8.67.
4.3. Synthesis of 9,10-bis(2,4,6-triisopropylphenyl)-9,10-dihydro-
9,10-disilaanthracene (4)
Silane 3 (17.9 g, 51.9 mmol) was added to a refluxing mixture of
sodium (3.44 g, 150 mmol) in toluene (60 mL), and the mixture was
refluxed overnight. Then, the mixture was cooled in an ice bath,
quenched with ethanol, and diluted with diethyl ether. The organic
layer was washed with water, dried over MgSO4, and evaporated.
Direct analysis of the reaction mixture by 1H NMR spectroscopy
showed that the ratio of the cis and trans isomers was 43:57. The
residue was separated by column chromatography on silica gel
(hexane). The former fraction contained the cis isomer (1.17 g,
1.90 mmol, 7%) and further elution gave a mixture of the cis and
trans isomers (780 mg, 1.26 mmol, 5%). Finally, the trans isomer
(1.44 g, 2.33 mmol, 9%) was obtained from the latter fraction. The
total yield of compound 4 was 21%.
4. Experimental
4.1. General
Melting points were determined using a Yamato MP-21 melting
point apparatus with open capillaries and are uncorrected. 1H, 13C,
and 29Si NMR spectra were measured in CDCl3 solution using
a Varian Mercury plus 400 spectrometer at 400, 100, and 79 MHz,
respectively. All chemical shifts are reported as
relative to residual chloroform (dH 7.26), the central peak of CDCl3
dC 77.0), or tetramethylsilane (dSi 0.0). J-Values are given in Hz.
d
-values (ppm)
cis-4, mp 235e237 ꢁC. 1H NMR (CDCl3)
d
0.66 (d, J ¼ 7 Hz, 12H),
1.32 (d, J ¼ 7 Hz, 12H), 1.37 (d, J ¼ 7 Hz, 12H), 2.68 (sep, J ¼ 7 Hz, 2H),
2.95 (sep, J ¼ 7 Hz, 2H), 3.86 (d sep, J ¼ 1 and 7 Hz, 2H), 5.84 (d,
J ¼ 1 Hz, 2H), 6.99 (s, 2H), 7.21 (s, 2H), 7.27 (m, 4H), 7.42 (m, 4H). 13C
(
GCeMS (EI) was measured by the direct combination of GC
(HewlettePackard GC 5890 Series II with a 25 m ꢂ 0.25 mm methyl
silicone capillary column) and a JEOL JMS-AX-500 spectrometer
with a DA7000 data system. Infrared spectra were recorded using
a JASCO IR Report-100 spectrometer. Elemental analyses were
performed using a PerkinElmer 2400 Series II Analyzer.
NMR (CDCl3)
d 23.8, 24.2, 24.9, 33.3, 34.2. 34.9, 120.7, 122.0, 125.2,
128.3, 135.1, 141.4, 151.4, 156.9, 157.5. 29Si NMR (CDCl3)
d
ꢀ46.7. IR
(KBr) nSieH 2150 cmꢀ1. HRMS m/z 616.3935 (Mþ, calcd for C42H56Si2
616.3921). Anal. Calcd for C42H56Si2: C, 81.75; H, 9.15. Found C,
81.40; H, 9.26.
trans-4, mp 247e249 ꢁC 1H NMR (CDCl3)
d
1.00 (d, J ¼ 7 Hz, 24H),
1.26 (d, J ¼ 7 Hz, 12H), 2.88 (sep, J ¼ 7 Hz, 2H), 3.55 (sep, J ¼ 7 Hz,
4.2. Preparation of (2-chlorophenyl)(2,4,6-triisopropyl)
phenylsilane (3)
4H), 5.86 (s, 2H), 7.01 (s, 4H), 7.24 (m, 4H), 7.49 (m, 4H). 13C NMR
(CDCl3)
d 23.8, 24.3, 34.3, 34.4, 121.3, 127.5, 128.0, 135.4, 142.2, 151.1,
156.5. 29Si NMR (CDCl3)
d
ꢀ47.1. IR (KBr) nSieH 2124 cmꢀ1. HRMS m/z
Butyllithium in hexane (1.6 M, 63 mL, 100 mmol) was added to
a solution of 2-chlorobromobenzene (1, 19.2 g, 100 mmol) in THF
(100 mL) and diethyl ether (100 mL) at ꢀ95 ꢁC under an argon
atmosphere. After the above mixture was stirred for an additional
616.3911 (Mþ, calcd for C42H56Si2 616.3921). Anal. Calcd for
C42H56Si2: C, 81.75; H, 9.15. Found C, 81.35; H, 9.18.
1
h,
a
solution of (2,4,6-triisopropylphenyl)silane (23.4 g,
4.4. X-ray structure determination of cis-4
100 mmol) in THF (100 mL) and diethyl ether (100 mL) was added
dropwise into it and the resulting solution was stirred for 1 h. Then
the reaction mixture was allowed to warm up to room temperature
and quenched with a mixture of concentrated HCl (20 mL) and
ethanol (50 mL). The mixture was diluted with diethyl ether and
the organic layer was washed with brine, dried over MgSO4, and
evaporated. The residue was purified by column chromatography
on silica gel (hexane) to give silane 3 (27.2 g, 79%) as a colorless
Crystal data were collected using a Rigaku RAXIS RAPID imaging
plate area detector with graphite monochromated Cu-Ka radiation.
An empirical absorption correction was applied, which resulted in
transmission factors ranging from 0.742 to 0.901. The data were
corrected for Lorentz and polarization effects. A correction for
secondary extinction [25] was applied (coefficient ¼ 93.535004).
The structure was solved by direct methods [26] and expanded
using Fourier techniques [27]. The non-hydrogen atoms were
refined anisotropically. Hydrogen atoms were refined using the
riding model.
solid, mp 78e79 ꢁC. 1H NMR (CDCl3)
d
1.19 (d, J ¼ 7 Hz, 12H), 1.29 (d,
J ¼ 7 Hz, 6H), 2.92 (sep, J ¼ 7 Hz, 1H), 3.22 (sep, J ¼ 7 Hz, 2H), 5.07 (s,
2H), 7.09 (s, 2H), 7.16 (m, 1H), 7.22 (m, 1H), 7.36 (m, 1H), 7.38 (m,

M. Oba et al. / Journal of Organometallic Chemistry 696 (2011) 982e985
985
[6] T. Gimisis, M. Ballestri, C. Ferreri, C. Chatgilialoglu, Tetrahedron Lett. 36 (1995)
3897e3900.
[7] K. Nishiyama, M. Oba, H. Takagi, T. Saito, Y. Imai, I. Motoyama, S. Ikuta,
H. Hiratsuka, J. Organomet. Chem. 626 (2001) 32e36.
[8] Y. van den Winkel, B.L.M. van Baar, F. Bickelhaupt, W. Kulik, C. Sierakowski,
G. Maier, Chem. Ber. 124 (1991) 185e190.
[9] H. Hiratsuka, M. Tanaka, T. Okutsu, M. Oba, K. Nishiyama, J. Chem. Soc. Chem.
Commun. (1995) 215e216.
Crystal data for cis-4: C42H56Si2, M ¼ 617.08, crystal dimensions
0.10 ꢂ 0.08 ꢂ 0.06 mm3, monoclinic, a ¼ 16.8703(3), b ¼ 12.8553
(2), c ¼ 18.3357(3) Å,
b
¼ 109.3719(10)ꢁ, V 3751.40(12) Å3,
T ¼ 123.1 K, space group P21/c (#14), Z ¼ 4, rcalcd ¼ 1.092 gcmꢀ3
, m
(Cu-K
a
) ¼ 1.040 mmꢀ1, 33663 reflections measured, 6777 inde-
pendent reflections (Rint ¼ 0.058). The final R1 values were 0.0485
(I > 2s
(I)). The final wR(F2) values were 0.1386 (all data). The
[10] H. Hiratsuka, M. Tanaka, H. Horiuchi, Narisu, Y. Tetsutaro, M. Oba,
K. Nishiyama, J. Organomet. Chem. 611 (2000) 71e77.
goodness of fit on F2 was 0.958.
[11] J.D. Rich, R. West, J. Am. Chem. Soc. 104 (1982) 6884e6885.
[12] G. Maier, K. Shottler, H.P. Reisenauer, Tetrahedron Lett. 26 (1985) 4079e4082.
[13] K.M. Welsh, J.D. Rich, R. West, J. Organomet. Chem. 325 (1987) 105e115.
[14] Y. Kabe, K. Ohkubo, H. Ishikawa, W. Ando, J. Am. Chem. Soc. 122 (2000)
3775e3776.
4.5. Theoretical calculations
[15] M. Oba, Y. Watanabe, K. Nishiyama, Organometallics 21 (2002) 3667e3670.
[16] N. Takeda, A. Shinohara, N. Tokitoh, Organometallics 21 (2002) 256e258.
[17] W.Z. McCarthy, J.Y. Corey, E.R. Corey, Organometallics 3 (1984) 255e263.
[18] J.Y. Corey, W.Z. McCarthy, J. Organomet. Chem. 271 (1984) 319e326.
[19] H. Gilman, E.A. Zuech, W. Steudel, J. Org. Chem. 27 (1962) 1836e1839.
[20] O.A. D’yachenko, L.O. Atovmyan, S.V. Soboleva, T.Y. Markova,
N.G. Komalenkova, L.N. Shamshin, E.A. Chernyshev, Zh. Strukt. Khim.
15 (1974) 667e674.
The structures of cis-4 and trans-4 were fully optimized with the
6-31G(d,p) basis set using the three-parameter functional of Becke
(B3) [28], augmented by the correlation functional of Lee, Yang, and
Parr (LYP) [29]. The B3LYP vibrational analyses were performed for
each optimized structure to characterize the stationary points as
minima and to calculate the ZPVE. All calculations were performed
with Gaussian 03 [22].
[21] O.A. D’yachenko, L.O. Atovmyan, S.V. Soboleva, Zh. Strukt. Khim. 16 (1975)
505e508.
[22] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb,
J.R. Cheeseman, J.A. Montgomery Jr., T. Vreven, K.N. Kudin, J.C. Burant,
J.M. Millam, S.S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi,
G. Scalmani, N. Rega, G.A. Petersson, H. Nakatsuji, M. Hada, M. Ehara,
K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao,
H. Nakai, M. Klene, X. Li, J.E. Knox, H.P. Hratchian, J.B. Cross, C. Adamo,
J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R. Cammi,
C. Pomelli, J.W. Ochterski, P.Y. Ayala, K. Morokuma, G.A. Voth, P. Salvador,
J.J. Dannenberg, V.G. Zakrzewski, S. Dapprich, A.D. Daniels, M.C. Strain,
O. Farkas, D.K. Malick, A.D. Rabuck, K. Raghavachari, J.B. Foresman, J.V. Ortiz,
Q. Cui, A.G. Baboul, S. Clifford, J. Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko,
P. Piskorz, I. Komaromi, R.L. Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng,
A. Nanayakkara, M. Challacombe, P.M.W. Gill, B. Johnson, W. Chen,
M.W. Wong, C. Gonzalez, J.A. Pople, Gaussian 03, Revision B.04. Gaussian, Inc.,
Pittsburgh PA, 2003.
[23] C.W. Bauschlicher, H.J. Partridge, J. Chem. Phys. 103 (1995) 1788e1791.
[24] A.P. Scott, L. Radom, J. Chem. Phys. 100 (1996) 16502e16513.
[25] A.C. Larson, The inclusion of secondary extinction in least squares refinement
of crystal structures. in: F.R. Ahmed, S.R. Hall, C.P. Huber (Eds.), Crystallo-
graphic Computing. Munksgaard, Copenhagen, 1970, pp. 291e294.
[26] A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, M.C. Burla, G. Polidori,
M. Camalli SIR92, J. Appl. Crystallogr. 27 (1994) 435.
Appendix A. Supplementary material
CCDC 787292 contains the supplementary crystallographic data
for the structural analysis of cis-4. These data can be obtained free
of charge from The Cambridge Crystallographic Data Centre via
http://www.ccdc.cam.ac.uk/data_request/cif.
Appendix A. Supplementary material
Supplementary material associated with this article can be found
in the online version, at doi:10.1016/j.jorganchem.2010.10.010.
References
[1] W. Ando, K. Hatano, R. Urisaka, Organometallics 14 (1995) 3625e3627.
[2] K. Hatano, K. Morihashi, O. Kikuchi, W. Ando, Chem. Lett. (1997) 293e294.
[3] S. Kyushin, T. Shinnai, T. Kubota, H. Matsumoto, Organometallics 16 (1997)
3800e3804.
[4] M. Oba, K. Nishiyama, J. Chem. Soc. Chem. Commun. (1994) 1703e1704.
[5] M. Oba, Y. Kawahara, R. Yamada, H. Mizuta, K. Nishiyama, J. Chem. Soc. Perkin
Trans. 2 (1996) 1843e1848.
[27] P.T. Beurskens, G. Admiraal, G. Beurskens, W.P. Bosman, R. de Gelder, R. Israel,
J.M.M. Smits, The DIRDIF-99 program system, Technical Report of the Crys-
tallography Laboratory. University of Nijmegen, The Netherlands, 1999.
[28] A.D. Becke, J. Chem. Phys. 98 (1993) 5648e5652.
[29] C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785e789.