Electron-transfer reactions of 1,2-dimetallacyclohexa-3,5-dienes with TCNE

Article abstract of DOI:10.1016/S0022-328X(03)00171-2

Thermal reactions of 1,2-dimetallacyclohexa-3,5-dienes (1-3) with tetracyanoethylene (TCNE) were investigated. The reaction of 1,2-disilacyclohexa-3,5-diene (1) with TCNE mainly gave 4-amino-5,6-dicyano-2,2,11,11-tetramethyl-1,8,9,10-tetraphenyl-3-aza-2, 11-disilatricyclo[6.2.1.0^3,7]undeca-4,6,9-triene through a charge-transfer complex. The reaction of 1,2-digermacyclohexa-3,5-diene (2) with TCNE afforded 4-amino-5,6-dicyano-2,2,11,11-tetramethyl-1,8,9, 10-tetraphenyl-3-aza-2,11-digermatricyclo[6.2.1.0^3,7] undeca-4,6,9-triene. 2,2,3,3-Tetracyano-7,7-dimethyl-1,4,5,6- tetraphenyl-7-germabicyclo[2.2.1]hept-5-ene was also detected. On the other hand, 1-germa-2-silacyclohexa-3,5-diene (3) reacted with TCNE to give 4-amino-5,6-dicyano-2,2,11,11-tetramethyl-1,8,9,10- tetraphenyl-3- aza-11-germa-2-silatricyclo[6.2.1.0^3,7] undeca-4,6,9-triene, 4-amino-5,6-dicyano-2,2,11,11-tetramethyl-1,8,9,10- tetraphenyl-3-aza-11- germa-2-silatricyclo[6.3.0^1,8 .0^3,7]undeca-4,6,9- triene, and 2,2,3,3-tetracyano-7,7-dimethyl-1,4,5, 6-tetraphenyl-7- germabicyclo[2.2.1]hept-5-ene as main products. The mechanism of the formation of new heterocyclic compounds through electron-transfer reactions of 1,2-dimetallacyclohexa-3,5-dienes with TCNE is discussed.

Full text of DOI:10.1016/S0022-328X(03)00171-2

Journal of Organometallic Chemistry 673 (2003) 84Á94
/
www.elsevier.com/locate/jorganchem
Electron-transfer reactions of 1,2-dimetallacyclohexa-3,5-dienes with
TCNE
Kunio Mochida a,*, Hiromi Shimizu a, Tsuyoshi Kugita b, Masato Nanjo a
a Department of Chemistry, Faculty of Science, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo 171-8588, Japan
b Department of Material Science, Teikyo University of Science and Technology, 2525 Yatsuzawa, Uenohara-machi, Yamanashi 409-0193, Japan
Received 6 November 2002; received in revised form 27 January 2003; accepted 25 February 2003
Abstract
Thermal reactions of 1,2-dimetallacyclohexa-3,5-dienes (1Á3) with tetracyanoethylene (TCNE) were investigated. The reaction of
/
1,2-disilacyclohexa-3,5-diene (1) with TCNE mainly gave 4-amino-5,6-dicyano-2,2,11,11-tetramethyl-1,8,9,10-tetraphenyl-3-aza-
2,11-disilatricyclo[6.2.1.03,7]undeca-4,6,9-triene through a charge-transfer complex. The reaction of 1,2-digermacyclohexa-3,5-diene
(2) with TCNE afforded 4-amino-5,6-dicyano-2,2,11,11-tetramethyl-1,8,9,10-tetraphenyl-3-aza-2,11-digermatricyclo[6.2.1.03,7]un-
deca-4,6,9-triene. 2,2,3,3-Tetracyano-7,7-dimethyl-1,4,5,6-tetraphenyl-7-germabicyclo[2.2.1]hept-5-ene was also detected. On the
other hand, 1-germa-2-silacyclohexa-3,5-diene (3) reacted with TCNE to give 4-amino-5,6-dicyano-2,2,11,11-tetramethyl-1,8,9,10-
tetraphenyl-3-aza-11-germa-2-silatricyclo[6.2.1.03,7]undeca-4,6,9-triene, 4-amino-5,6-dicyano-2,2,11,11-tetramethyl-1,8,9,10-tetra-
phenyl-3-aza-11-germa-2-silatricyclo[6.3.01,8.03,7]undeca-4,6,9-triene, and 2,2,3,3-tetracyano-7,7-dimethyl-1,4,5,6-tetraphenyl-7-ger-
mabicyclo[2.2.1]hept-5-ene as main products. The mechanism of the formation of new heterocyclic compounds through electron-
transfer reactions of 1,2-dimetallacyclohexa-3,5-dienes with TCNE is discussed.
# 2003 Elsevier Science B.V. All rights reserved.
Keywords: 1,2-Dimetallacyclohexa-3,5-diene; TCNE; Electron-transfer
1. Introduction
Group 14 elements (silicon, germanium)Á
their ion radicals by means of UV, ESR, and other
spectroscopies. A few reports on ring contraction
through CT interactions between cyclic Group 14
elements catenate compounds and TCNE have been
reported [4]. We describe herein the formation of new
heterocyclic compounds through electron-transfer reac-
tions of 1,2-dimetallacyclohexa-3,5-dienes having
/Group 14
elements s bonds with rather low oxidation potentials in
solutions are excellent electron donors. As electron-rich
species, these Group 14 elements catenates are subject to
cleavage by various organic electrophiles as well as
transition metal complexes through a charge-transfer
(CT) complex [1]. During the past two decades, the CT
interactions between Group 14 elements catenates s
bonds and common electron acceptors such as tetra-
cyanoethylene (TCNE) have been amply investigated
Group 14 elementsÁGroup 14 elements s bonds with
/
TCNE.
2. Results
[2Á8]. However, a large portion of studies on their CT
/
interactions are limited to CT spectra between Group 14
catenates and electron acceptors such as TCNE and
2.1. Reactions of 1,2-dimetallacyclohexa-3,5-dienes with
TCNE
* Corresponding author. Tel.: ꢀ
1029.
E-mail address: kunio.mochida@gakushuin.ac.jp (K. Mochida).
/
81-3-3986-0221; fax: 81-3-5992-
Reactions of Group 14 elementsÁ
s bonds of 1,2-disila-, 1,2-digerma-, and 1-germa-2-sila-
/
Group 14 elements
0022-328X/03/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0022-328X(03)00171-2

K. Mochida et al. / Journal of Organometallic Chemistry 673 (2003) 84Á
/94
85
cyclohexa-3,5-dienes (1-3) with TCNE at 90 8C were
examined.
A solution of 1,1,2,2-tetramethyl-1,2-disila-3,4,5,6-
tetraphenylcyclohexa-3,5-diene [9] (1) (0.4 mmol) and
TCNE (0.4 mmol) in dichloromethane (CH2Cl2) was
placed in a Pyrex tube under argon and sealed. The
color of the solution changed from yellowish-green to
reddish-brown. The reaction mixture was heated at
90 8C for 3 h to give 4-amino-5,6-dicyano-2,2,11,11-
tetramethyl-1,8,9,10-tetraphenyl-3-aza-2,11-disilatricy-
clo[6.2.1.03,7]undeca-4,6,9-triene (4, 38%) and 2,2,3,3-
tetracyano-7,7-dimethyl-1,4,5,6-tetraphenyl-7-silabicy-
clo[2.2.1]hept-5-ene (5, trace). 1,1,3,3-Tetramethyl-
4,5,6,7-tetraphenyl-2-oxa-1,3-disilacyclohepta-4,6-diene
(6, 16%) and some unidentified products were also
formed (Eq. (1)). The rest of 1 (40%) was recovered
unchanged from the CH2Cl2 solution. The yields of
products (4, 5, 6) were based on the amounts of initial
amount of 1 and were determined by NMR spectra.
Concentration of the reaction mixture by evaporation of
CH2Cl2 followed by both preparative GPC and TLC
(silica gel) gave pure 4. The structure of 4 was
determined by NMR and MS spectra. 7-Silabicy-
clo[2.2.1]hept-5-ene 5 and 2-oxa-1,3-disilacyclohepta-
4,6-diene 6 could not be isolated. Compounds 5 and 6
were characterized by NMR and MS spectra in com-
parison with those of authentic samples. In spite of
every efforts of minimizing moisture and air, 6 was
obtained in substantial amounts.
Fig. 1. Molecular structure of the 4-amino-5,6-dicyano-2,2,11,11-
tetramethyl-1,8,9,10-tetraphenyl-3-aza-2,11-disilatricyclo[6.2.1.03,7]un-
deca-4,6,9-triene (4). (30% probability thermal ellipsoids). Hydrogen
atoms are omitted for clarity.
˚
(1.9310(13) A) and bond angle of C(3)Ã
/
Si(1)Ã
Si(1) and
Me (1.852(2)
and 1.8597(19) A) in 5. The bond angles of Si(1)ÃC(8)Ã
C(4), Si(1)ÃC(3)ÃC(5), and C(4)ÃC(3)ÃC(5) are 123.9,
122.0, and 114.18, respectively.
/
C(3)*(82.08(8)8). The bond lengths of C(3)Ã
/
C(3)*ÃSi(1) are longer than those of SiÃ
/
/
˚
/
/
/
/
/
/
The colored solution of 1 and TCNE in CH2Cl2 at
70 8C was examined by ESR spectroscopy. The observed
ESR spectrum showed a weak broad signal with gꢁ
/
2.0031. The g value suggests the presence of the TCNE
radical anion [3].
A Pyrex tube containing CH2Cl2 solution of 1,1,2,2-
tetramethyl-1,2-digerma-3,4,5,6-tetraphenylcyclohexa-
3,5-diene [10] (2) (0.01 mmol) and TCNE (0.01 mmol)
was placed in argon and sealed. The tube was heated at
90 8C for 4 h to give 4-amino-5,6-dicyano-2,2,11,11-
tetramethyl-1,8,9,10-tetraphenyl-3-aza-2,11-digermatri-
cyclo[6.2.1.03,7]undeca-4,6,9-triene (7, 3%) together with
2,2,3,3-tetracyano-7,7-dimethyl-1,4,5,6-tetraphenyl-7-
germabicyclo[2.2.1]hept-5-ene (8, 9%). 1,1,3,3-Tetra-
methyl - 4,5,6,7 - tetraphenyl - 2 - oxa - 1,3 - digermacyclo-
hepta-4,6-diene (9, 16%), 2,2,4,4,6,6-hexamethyl-1,3,5-
trioxa-2,4,6-trigermacyclohexane (10, trace), and some
unidentified products were also detected (Eq. (2)). The
rest of 2 (45%) remained unreacted and was recovered
from the CH2Cl2 solution. The color of the solution of 2
and TCNE changed from yellow to green. The yields of
ð1Þ
The molecular structures of 4 and 5 were fully
established by spectroscopic and X-ray diffraction
methods. The molecular structure of 4 is shown in Fig.
1, and crystallographic data are summarized in Table 1.
Selected bond lengths and angles in compound 4 are
summarized in Table 2. The pyrrole ring and the C(5)Ã
C(4)ÃN(1)ÃSi(2)ÃC(8) plane are nearly planar. The
bond angles of Si(1)ÃC(8)ÃC(7) and Si(1)ÃC(8)ÃSi(2)
/
/
/
/
/
/
/
/
are 97.2(2) and 107.65(16)8, respectively. Fig. 2 shows
the molecular structure of 5. The crystallographic data
are included in Table 1. Selected bond lengths and bond
angles are summarized in Table 3. The 7-silabicy-
clo[2.2.1]hept-5-ene 5 shown in Fig. 2 has a distorted
products (7Á
/
10) were based on the amounts of initial
geometry, with bond lengths of C(3) or C(3)*Ã
/Si(1)
amount of 2 and were determined by NMR spectra.

86
K. Mochida et al. / Journal of Organometallic Chemistry 673 (2003) 84Á94
/
Table 1
Crystallographic data for 4, 5, 7, 8, 11 and 12
4
5
7
8
11
12
Chemical formula
Formula weight
Temperature (K)
Crystal system
Space group
C
38H32N4Si2
C36H26N4Si
542.70
200(0)
C39H36Ge2N4
776.80
293(2)
C36H26GeN4
587.20
293(2)
C38H32GeN4Si
730.28
200(0)
C38H34GeN4Si
647.37
295(2)
685.78
295(2)
monoclinic
P21/c
monoclinic
P21/m
monoclinic
P21/c
monoclinic
P21/m
monoclinic
P21/c
monoclinic
P21/n
˚
a (A)
9.7060(6)
15.7580(10)
23.6360(8)
90
8.8570(5)
20.1310(10)
8.7790(5)
90
9.7410(8)
15.6950(5)
23.3660(14)
90
8.8680(3)
20.1090(9)
8.9420(3)
90
9.6500(5)
15.6930(5)
23.5020(13)
90
10.4920(4)
16.8670(11)
18.8150(10)
90
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
98.928(4)
90
111.823(3)
90
98.207(3)
90
111.797(2)
90
98.446(3)
90
94.920(3)
90
3
˚
V (A )
Z
3571.3(3)
4
1.275
1453.07(17)
2
1.240
3535.7(4)
4
1.459
1480.59(10)
2
1.317
3520.5(3)
4
1.378
3317.4(3)
4
1.296
Dcalc (g cmꢂ3
)
Crystal dimensions (mm)
Reflections (hkl) limits
0.45ꢃ
05h 5
05k 5
265l 5
/
0.45ꢃ
10,
17,
25
/0.40
0.2ꢃ
05h 5
05k 5
95l 5
2168
/
0.2ꢃ
9,
22,
/0.2
0.2ꢃ
05h 5
05k 5
265l 5
/
0.2ꢃ
10,
17,
25
/
0.2
0.4ꢃ
05h 5
05k 5
115l 5
/
0.3ꢃ
11,
26,
10
/
0.2
0.3ꢃ
05h 5
05k 5
265l 5
/
0.3ꢃ
10,
17,
25
/
0.2
0.50ꢃ
05h 5
05k 5
205l 5
/
ꢃ
/
/
0.45ꢃ
11,
18,
20
/0.20
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
ꢂ/
/
/
ꢂ/
/
/9
ꢂ/
/
/
ꢂ/
/
/
ꢂ/
/
/
ꢂ/
/
/
Unique reflections
5114
4907
3492
5094
4546
R [I ꢀ
(All data)
Rw [I ꢀ2s(I)]
(All data)
Goodness-of-fit
/
2s(I)]
0.0691
0.0794
0.2192
0.2306
1.831
0.0391
0.0407
0.1521
0.1521
1.480
0.0487
0.0558
0.1566
0.1566
1.356
0.0360
0.0382
0.1105
0.1105
1.040
0.0441
0.0510
0.1417
0.1489
1.238
0.0403
0.0463
0.1279
0.1345
1.161
/
Table 2
˚
Selected bond distances (A) and angles (8) for 4
Si(1)Ã
Si(1)Ã
Si(2)Ã
Si(2)Ã
C(1)Ã
C(3)Ã
C(5)Ã
C(7)Ã
/
C(11)
C(8)
1.847(4)
1.902(4)
1.811(3)
1.858(4)
1.367(5)
1.368(5)
1.553(4)
1.556(4)
Si(1)Ã
Si(1)Ã
Si(2)Ã
Si(2)Ã
C(2)Ã
C(4)Ã
C(6)Ã
/
C(12)
1.859(4)
1.927(3)
1.843(4)
1.888(3)
1.451(4)
1.515(5)
1.358(5)
/
/C(5)
/
N(1)
C(13)
/C(14)
/
/C(8)
/
C(2)
C(4)
C(6)
C(8)
/
C(3)
C(5)
C(7)
/
/
/
/
/
C(11)Ã
C(12)Ã
C(12)Ã
N(1)ÃSi(2)Ã
N(1)ÃSi(2)Ã
C(1)ÃN(1)Ã
C(4)ÃN(1)Ã
/
Si(1)Ã
Si(1)Ã
Si(1)Ã
/
C(12)
C(8)
C(5)
110.7(2)
C(11)Ã
/
Si(1)Ã
Si(1)Ã
Si(1)ÃC(5)
108.71(17) C(14)ÃSi(2)ÃC(13)
105.29(14) C(14)ÃSi(2)ÃC(8)
N(1)ÃSi(2)
/
C(8)
112.29(18)
109.76(17)
91.08(14)
111.3(2)
/
/
118.38(18) C(11)Ã
113.06(17) C(8)Ã
/
/C(5)
/
/
/
/
/
/
C(14)
/
/
/
/C(8)
/
/
111.69(18)
124.2(2)
/
/C(4)
107.8(3)
127.4(2)
C(1)Ã
/
/
/
/Si(2)
Fig. 2. Molecular structure of the 2,2,3,3-tetracyano-7,7-dimethyl-
1,4,5,6-tetraphenyl-7-silabicyclo[2.2.1]hept-5-ene (5). (50% probability
thermal ellipsoids.) Hydrogen atoms are omitted for clarity.
Concentration of the CH2Cl2 solvent by evaporation
followed by both preparative GPC and the TLC (silica
gel) gave pure 7, which showed satisfactory NMR and
MS data. Products 8Á
and GCÁMS spectra in comparison with those of
authentic samples [11,12]. In spite of every efforts of
/
10 were characterized by NMR
/
ð2Þ

K. Mochida et al. / Journal of Organometallic Chemistry 673 (2003) 84Á
/94
87
Table 3
Selected bond distances (A) and angles (8) for 5
˚
Si(1)Ã
Si(1)Ã
C(3)Ã
C(4)Ã
/
C(1)
C(3)
1.852(2)
Si(1)Ã
/
C(2)a
C(3)a
1.8597(19)
1.9310(13)
1.6055(19)
1.616(3)
/
1.9311(13) Si(1)Ã
1.5427(17) C(3)Ã
1.350(3)
/
/
C(4)
/
C(5)
/
C(4)a
C(5)Ã
C(1)Ã
C(1)Ã
C(3)aÃ
/
C(5)a
C(1)Ã
C(2)Ã
C(2)Ã
/
Si(1)Ã
Si(1)Ã
Si(1)Ã
/
C(2)
C(3)a
C(3)
109.85(9)
113.39(6)
113.39(6)
/
Si(1)Ã
Si(1)Ã
Si(1)Ã
/
C(3)a
C(3)
117.93(6)
117.93(6)
82.08(8)
/
/
/
/
/
/
/
/
C(3)
a
x, ꢂy
3/2, z.
/
minimizing moisture and air, 9 and 10 were obtained in
an appreciable amount.
The molecular structures of 7 and 8 were fully
established by spectroscopic methods and X-ray diffrac-
tion analysis. The molecular structures of 7 and 8 are
shown in Figs. 3 and 4, respectively, and crystallo-
graphic data are included in Table 1. Selected bond
lengths and angles in compounds 7 and 8 are summar-
ized in Tables 4 and 5, respectively. The pyrrole ring and
the C(5)Ã
nar. The bond angles of Ge(1)Ã
C(8)ÃGe(2) are 99.0(3) and 105.57 (19)8, respectively.
/
C(4)Ã
/
N(1)Ã
/
Ge(2)Ã
/
C(8) plane are nearly pla-
Fig. 4. Molecular structure of the 2,2,3,3-tetracyano-7,7-dimethyl-
1,4,5,6-tetraphenyl-7-germabicyclo[2.2.1]hept-5-ene (8). (50% prob-
ability thermal ellipsoids.) Hydrogen atoms are omitted for clarity.
/
C(8)ÃC(7) and Ge(1)Ã
/
/
/
The 7-germabicyclo[2.2.1]hept-5-ene 8 shown in Fig. 4
A CH2Cl2 solution of 1,1,2,2-tetramethyl-1-germa-
2-sila-3,4,5,6-tetraphenylcyclohexa-3,5-diene (3) (0.4
mmol) and TCNE (0.4 mmol) was placed in a Pyrex
tube under argon and sealed. Heating of the reaction
mixture of 3 at 90 8C for 3 h afforded 4-amino-5,6-
dicyano-2,2,11,11-tetramethyl-1,8,9,10-tetraphenyl-3-
aza-11-germa-2-silatricyclo[6.2.1.03,7]undeca-4,6,9-tri-
ene (11, 5%), 4-amino-5,6-dicyano-2,2,11,11-tetra-
methyl-1,8,9,10-tetraphenyl-3-aza-11-germa-2-silatricy-
clo[6.3.01,8.03,7]undeca-4,6,9-triene (12, 4%), and 2,2,3,3-
tetracyano-7,7-dimethyl-1,4,5,6-tetraphenyl-7-germabi-
cyclo[2.2.1]hept-5-ene (8, 15%). 1,1,3,3-Tetramethyl-
4,5,6,7-tetraphenyl-2-oxa-1-germa-3-silacyclohepta-4,6-
diene (13, 23%) and some unidentified products were
has a distorted geometry, with bond lengths of C(3) or
˚
C(3)*Ã
Ge(1)Ã
C(3)*Ã
and 1.952(2) A) in 8. The bond angles of Ge(1)Ã
C(4), Ge(1)ÃC(3)ÃC(5), and C(4)ÃC(3)ÃC(5) are 123.3,
122.2, and 115.68, respectively.
/
Ge(1) (2.0269(15) A) and bond angle of C(3)Ã
/
/
C(3)* (78.72(8)8). The bond lengths of C(3) or
Ge(1) are longer than those of GeÃMe (1.939(2)
C(8)Ã
/
/
˚
/
/
/
/
/
/
ESR studies of the colored CH2Cl2 solution contain-
ing 2 and TCNE revealed a well resolved radical anion
of TCNE (gꢁ
/
2.0031, aNꢁ1.56 G) [3].
/
Table 4
˚
Selected bond distances (A) and angles (8) for 7
Ge(1)Ã
Ge(1)Ã
Ge(2)Ã
Ge(2)Ã
/
C(11)
1.934(4)
1.987(3)
1.927(4)
1.945(5)
1.372(6)
1.371(7)
1.559(6)
1.541(6)
Ge(1)Ã
Ge(1)Ã
Ge(2)Ã
Ge(2)Ã
/
C(12)
1.938(4)
2.012(3)
1.935(5)
1.972(4)
1.450(6)
1.515(6)
1.339(6)
/C(8)
/C(5)
/N(1)
/C(13)
/C(14)
/C(8)
C(1)Ã
C(3)Ã
C(5)Ã
C(7)Ã
/
C(2)
C(4)
C(6)
C(8)
C(2)Ã
C(4)Ã
C(6)Ã
/
C(3)
C(5)
C(7)
/
/
/
/
/
C(11)Ã
C(12)Ã
C(12)Ã
N(1)ÃGe(2)Ã
N(1)ÃGe(2)Ã
C(1)ÃN(1)Ã
C(4)ÃN(1)Ã
/
Ge(1)Ã
Ge(1)Ã
Ge(1)Ã
/
C(12)
C(8)
C(5)
113.2(2)
119.5(2)
112.3(2)
103.4(2)
C(11)Ã
C(11)Ã
C(8)ÃGe(1)Ã
C(14)ÃGe(2)Ã
Ge(2)Ã
N(1)ÃGe(2)
/
Ge(1)Ã
G(1)ÃC(5)
C(5)
C(13)
C(8)
/
C(8)
111.7(2)
108.7(2)
88.63(17)
113.8(2)
115.2(2)
122.9(3)
/
/
/
/
/
/
/
/
/
/
C(14)
C(8)
/
/
/
/
102.86(16) C(14)Ã
108.2(4)
128.2(3)
/
/
Fig. 3. Molecular structure of the 4-amino-5,6-dicyano-2,2,11,11-
tetramethyl-1,8,9,10-tetraphenyl-3-aza-2,11-digermatricy-
clo[6.2.1.03,7]undeca-4,6,9-triene (7). (30% probability thermal ellip-
soids.) Hydrogen atoms are omitted for clarity.
/
/
C(4)
C(1)Ã
/
/
/
/
Ge(2)

88
K. Mochida et al. / Journal of Organometallic Chemistry 673 (2003) 84Á94
/
Table 5
2.2. Electrochemical properties of 1,2-
dimetallacyclohexa-3,5-dienes
˚
Selected bond distances (A) and angles (8) for 8
Ge(1)Ã
Ge(1)Ã
/
C(1)
1.952(2)
2.0269(1)
Ge(1)Ã
Ge(1)Ã
/
C(2)
C(3)a
1.939(2)
2.0269(15)
1.593(2)
1.629(3)
The one-electron oxidation potentials of 1,2-dimetal-
/C(3)
/
C(3)Ã
C(4)Ã
/
C(4)
C(4)a
1.5314(19) C(3)Ã
1.355(3)
/
C(5)
C(5)a
lacyclohexa-3,5-dienes, 1Á3, in solutions are one of
/
/
C(5)Ã
/
important characters in the electron-transfer reactions.
Electrochemical measurements were carried out in a
three-electrode system. The working and counter elec-
trodes were platinum disk and platinum wire, respec-
C(1)Ã
C(2)Ã
C(2)Ã
/
Ge(1)Ã
Ge(1)Ã
Ge(1)Ã
/
C(2)
C(3)a
C(3)
111.02(11) C(1)Ã
112.26(7)
112.26(7)
/
Ge(1)Ã
Ge(1)Ã
C(3)aÃ
Ge(1)Ã
/
C(3)a
C(3)
119.56(7)
119.55(7)
78.72(8)
/
/
C(1)Ã
/
/
/
/
/
/C(3)
tively.
Dimetallacyclohexa-3,5-dienes, 1Á
The
reference
was
Ag j Agꢀ.
1,2-
3 were dissolved in
a
x, ꢂy
3/2, z.
/
/
dry acetonitrile (CH3CN) containing 0.1 M of tetra-
butylammonium tetrafluoroborate. The cyclic voltam-
also formed (Eq. (3)). The color of the solution changed
from yellowish-green to reddish-brown. The rest of 3
(46%) was recovered unchanged from the CH2Cl2
solution. Concentration of the reaction mixture by
evaporation of CH2Cl2 followed by both preparative
GPC and TLC (silica gel) gave pure 11 and 12, which
showed satisfactory NMR and MS data. In spite of
every efforts of minimizing moisture and air, 13 was
obtained in substantial amounts. The yields of products
mogram (CV) of 1Á3 is shown in Fig. 7. The scan was
/
started around 0 V vs. Ag j Agꢀ. The CV of 1Á
/
3 are
characterized by anodic waves, but no cathodic waves
were observed on the reverse scan, even at high scan
rates. The irreversible behavior suggests that the one-
electron oxidation species are unstable and the easiness
of oxidation processes for 1Á
the CV measurements. It has several oxidation peaks.
The half peak potentials (Ep/2) of peak 1 for 1Á3 are
/3 is fast on the time scale of
/
(8, 11Á/13) were based on the amounts of initial amount
involved in Table 8 together with containing (Me2Ge)6
as reference sample [13]. The Ep/2 values increase in
of 3 and were determined by NMR.
order 2B
/
1B3 as shown in Table 8.
/
3. Discussion
In order to obtain information on the reaction
intermediates, 1-sila- and 1-germacyclopenta-2,4-dienes
reacted with TCNE at room temperature to give the
corresponding 7-sila- and 7-germabicyclo[2.2.1]hept-5-
enes (5 and 8), respectively [14].
ð3Þ
Products 8, 13 were characterized by NMR and GCÁ
MS spectra in comparison with those of authentic
/
samples.
The molecular structures of 11 and 12 were fully
established by spectroscopic methods and X-ray diffrac-
tion analysis. The molecular structures of 11 and 12 are
shown in Figs. 5 and 6, respectively, and crystallo-
graphic data are included in Table 1. Selected bond
lengths and angles of 11 and 12 are summarized in
Tables 6 and 7, respectively. The pyrrole ring and the
C(5)Ã
planar. The bond angles of Ge(1)Ã
Ge(1)ÃC(8)ÃGe(2) are 99.0(3) and 105.57(19)8, respec-
tively.
The TCNE anion radical generated by a CT complex
between 3 and TCNE in CH2Cl2 at 70 8C is evidenced by
ESR signals [3].
/
C(4)Ã
/
N(1)Ã
/
Ge(2)Ã
/
C(8) plane in 11 are nearly
/
C(8)ÃC(7) and
/
/
/
Fig. 5. Molecular structure of the 4-amino-5,6-dicyano-2,2,11,11-
tetramethyl - 1,8,9,10 - tetraphenyl - 3 - aza - 11 - germa - 2 - silatricyclo-
[6.2.1.03,7]undeca-4,6,9-triene (11). (30% probability thermal ellip-
soids.) Hydrogen atoms are omitted for clarity.

K. Mochida et al. / Journal of Organometallic Chemistry 673 (2003) 84Á
/94
89
Table 7
Selected bond distances (A) and angles (8) for 12
˚
Ge(1)Ã
Ge(1)Ã
/
C(1)
1.942(3)
1.943(3)
1.787(2)
1.371(3)
1.335(4)
1.522(3)
1.443(4)
Ge(1)Ã
Ge(1)Ã
/
C(9)
C(8)
1.945(3)
1.998(3)
1.911(3)
1.390(3)
1.566(4)
1.374(4)
1.386(4)
/C(10)
/
Si(1)Ã
N(1)Ã
C(1)Ã
C(3)Ã
C(5)Ã
/
N(1)
Si(1)Ã
N(1)Ã
C(2)Ã
C(4)Ã
C(6)Ã
/
C(8)
/C(7)
/C(4)
/
C(2)
C(4)
C(6)
/
C(3)
C(5)
C(7)
/
/
/
/
C(1)Ã
C(9)Ã
C(9)Ã
N(1)Ã
N(1)Ã
C(7)ÃN(1)Ã
C(4)ÃN(1)Ã
/
Ge(1)Ã
Ge(1)Ã
Ge(1)Ã
/
C(9)
C(10)
C(8)
113.50(12) C(1)Ã
106.71(14) C(1)Ã
116.37(14) C(10)Ã
105.89(15) N(1)ÃSi(1)Ã
C(11)Ã
C(7)ÃN(1)Ã
C(1)ÃGe(1)
/
Ge(1)Ã
G(1)ÃC(8)
/
C(10)
115.27(13)
88.77(10)
/
/
/
/
/
/
/
Ge(1)Ã
/
C(8)
115.82(12)
108.93(14)
120.66(14)
136.09(19)
111.74(19)
/
Si(1)Ã
/
C(11)
/
/C(112)
/
Si(1)Ã
/
C(8)
91.88(11)
109.6(2)
/
Si(1)Ã
/
C(8)
/
/
C(4)
Si(1)
/
/
Si(1)
/
/
114.14(17) C(2)Ã
/
/
Fig. 6. Molecular structure of the 4-amino-5,6-dicyano-2,2,11,11-
tetramethyl-1,8,9,10-tetraphenyl-3-aza-2,11-digermatricy-
clo[6.3.01,8.03,7]undeca-4,6,9-triene (12). (30% probability thermal
ellipsoids.) Hydrogen atoms are omitted for clarity.
Table 6
˚
Selected bond distances (A) and angles (8) for 11
Ge(1)Ã
Ge(1)Ã
/
C(11)
1.934(4)
1.987(3)
1.823(3)
1.847(4)
1.371(5)
1.373(5)
1.554(4)
1.545(4)
Ge(1)Ã
Ge(1)Ã
/
C(12)
C(5)
C(13)
1.938(4)
2.012(3)
1.856(4)
1.882(3)
1.444(4)
1.500(5)
1.349(4)
/C(8)
/
Si(1)Ã
Si(2)Ã
C(1)Ã
C(3)Ã
C(5)Ã
C(7)Ã
/
N(1)
C(14)
Si(1)Ã
Si(1)Ã
C(2)Ã
C(4)Ã
C(6)Ã
/
/
/C(8)
/
C(2)
C(4)
C(6)
C(8)
/
C(3)
C(5)
C(7)
/
/
/
/
/
Fig. 7. CVs for 1,2-dimetallacyclohexa-3,5-diene (1Á
/
3) in 0.1 M TBAP
C(11)Ã
C(12)Ã
C(12)Ã
N(1)ÃSi(1)Ã
N(1)ÃSi(1)Ã
C(1)ÃN(1)Ã
C(4)ÃN(1)Ã
/
Ge(1)Ã
Ge(1)Ã
Ge(1)Ã
/
C(12) 112.85(18) C(11)Ã
/
Ge(1)Ã
G(1)ÃC(5)
Ge(1)ÃC(5)
108.27(15) C(14)ÃSi(1)Ã
105.38(13) C(14)ÃSi(1)Ã
N(1)ÃSi(1)
/
C(8)
111.86(15)
109.06(15)
88.09(12)
CH3CN solution at the scan rate of 100 mV sꢂ1
.
/
/C(8)
119.69(15) C(11)Ã
/
/
/
/C(5)
112.50(15) C(8)Ã
/
/
/
/
C(14)
/
/
C(13) 111.95(19)
Table 8
One-electron oxidation potentials of 1,2-dimetallacyclohexa-3,5-
dienes, 1Á3 and (Me2Ge)6
/
/C(8)
/
/
C(8)
111.66(17)
123.1(2)
/
/C(4)
108.2(3)
128.1(2)
C(1)Ã
/
/
/
/
/Si(1)
Compound
Ep/2 (V) vs. Ag j Agꢀ
1
0.61
0.56
0.65
0.53
2
3
(Me2Ge)6
ducts derived from TCNE with the decomposition of 5
(60%). The yield of unidentified products from TCNE
could not be determined by NMR and GC spectra. The
generation of dimethylsilylene from thermolysis of 5 was
also expected. However, no formation of products
derived from dimethylsilylene was detected. On the
other hand, heating of 8 in CH2Cl2 solution at 70 8C
for 6 h led to the decomposition of 8 (13%) with the
The 7-sila- and 7-germabicyclo[2.2.1]hept-5-ene 5, 8
were stable at room temperature for at least 72 h, but
very slowly decomposed at above 70 8C. Thus, com-
pound 5 in CH2Cl2 was heated at 70 8C for 6 h to give 1-
silacyclopenta-2,4-diene in 41% and unidentified pro-

90
K. Mochida et al. / Journal of Organometallic Chemistry 673 (2003) 84Á94
/
formation of 1-germacyclopenta-2,4-diene (6%), cyclic
germoxane 10 (4%), and unidentified products. The
presence of 10 is explained by the oligomerization of
germanones, which formed by the reaction of dimethyl-
germylene with included oxygen [15].
From these results, we propose the following scheme
as one possible reaction pathway of the formation of
heterocyclic compounds. Since Group 14 elementsÁ
Group 14 elements s bonds of 1,2-dimetallacyclohexa-
/
/
3,5-dienes, 1Á
/
3, with low oxidation potentials (0.56Á
0.65 V vs. Ag j Agꢀ) are excellent electron donors,
electron-transfer from compounds 1Á3 to TCNE gen-
/
erates the geminate radical ions composed of the radical
cation of 1Á3 and the radical anion of TCNE. For
/
obtaining their radical ions we attempted the detection
of an intermediate species by ESR spectroscopy. The
radical anion of TCNE was observed in all reactions,
but the radical cation of the compounds 1Á
be detected due to their instability at even low tempera-
ture [16]. In the radical cation of 1Á3 the Group 14
elementsÁGroup 14 elements bonds are possibly cleaved
/
3 could not
/
/
to give the corresponding open intermediates 14ꢀ+ Á
/
Scheme 1.
16ꢀ+, respectively. Then, subsequent intramolecular
addition of one of the silyl or germyl radicals to the
diene moiety gives 17ꢀ+ Á
Scheme 1.
/
19ꢀ+, respectively, depicted in
intermediates 17ꢀ+ Á
/
19ꢀ react with the anion radical
+
of TCNE (TCNEꢂ+) to give the corresponding biradi-
The intermediates 17ꢀ+ Á
/
19ꢀ undergo spontaneous
+
cal species 20Á
/
22, respectively. The carbon-centered
scission to cation radicals of 1-sila- and 1-germacyclo-
penta-2,4-dienes with extrusion of silylene and germy-
lene units. The cation radicals of 1-metallacyclopenta-
2,4-dienes are reduced by the anion radical of TCNE to
give 1-metallacyclopenta-2,4-dienes. However, we failed
to detect the silylene and germylene with trapping
reagents such as 2,3-dimethylbuta-1,3-diene and
triethylsilane (Et3SiH) [17]. The silylene and germylene
generated are easily converted into silicon- and germa-
nium-containing oligomers. On the other hand, the
radical in the biradical intermediates 20Á
cularly adds to one of the two allylic position to give
tricyanovinyl substituted 3-aza-2,8-disilabicyclo[3.2.1]
/
22 intramole-
octa-3,6-diene derivatives 23Á
Compounds 4, 7, 11 may be considered to be derived
from the intermediates 23Á25 after several steps. On the
/
25, respectively (path a).
/
other hand, the carbon-centered radical in the biradical
intermediate 22 intramolecularly adds to the another of
the two allylic position to give tricyanovinyl substituted
3-aza-2-germa-8-silabicyclo[3.3.0]oct-3,6-diene deriva-

K. Mochida et al. / Journal of Organometallic Chemistry 673 (2003) 84Á
/94
91
tives 26 (path b). Compounds 12 may be derived from
the intermediates 26 after several steps.
4.2. Materials
Some parts of the radical cations of 1,2-dimetallacy-
clohexa-3,5-dienes react with included oxygen to give
1,3-dimetalla-2-oxacyclohepta-4,6-dienes 6, 9, 13 [10].
1,1,2,2-Tetramethyl-1,2-disila-3,4,5,6-tetraphenylcy-
clohexa-3,5-diene [9], 1,1,2,2-tetramethyl-1,2-digerma-
3,4,5,6 - tetraphenylcyclohexa - 3,5 - diene [10], 1,1 - di-
methyl-1-sila-2,3,4,5-tetraphenylcyclopenta-2,4-diene
[20], 1,1 - dimethyl - 1 - germa - 2,3,4,5 - tetraphenylcyclo-
penta-2,4-diene [21], 1,1,3,3-tetramethyl-4,5,6,7-tetra-
phenyl - 2 - oxa - 1,3 - digermacyclohepta - 4,6 - diene [10],
2,2,4,4,6,6-hexamethyl-1,3,5-trioxa-2,4,6-trigermacyclo-
hexane [12], triethylsilane [22], dimethyldichloroger-
mane [23] were prepared as reported in the literature.
TCNE, CCl4, 2,3-dimethylbuta-1,3-diene, and m-chlor-
operoxybenzoic acid were commerically available.
1,2-Dimetallacyclohexa-3,5-dienes (1Á3) do not react
/
with oxygen.
4. Experimental
4.1. General methods
4.3. Preparation of 1,1,2,2-tetramethyl-1-germa-2-
sila-3,4,5,6-tetraphenylcyclohexa-3,5-diene (3)
The NMR spectra were obtained on a Varian Unity
Inova 400 MHz spectrometer. The GCÁMS spectra
were measured on a JEOL JMS-DX 303 mass spectro-
meter. The UV and UVÁvis spectra were recorded with
a Shimadzu UV 2000 spectrometer. The infrared spectra
were recorded with a Shimadzu FT IR 4200 spectro-
meter. Gas chromatography was performed on a
Shimadzu GC 8A with a 1 m 20% SE30 column. GPC
was performed on a Twincle with an Asahipak GS 310
column. X-ray crystallographic data and diffraction
intensities were collected on a MacScienec DIP2030
/
A mixture of lithium metal (0.25 g, 3.6 mmol) and
diphenylacetylene (6.3 g, 35 mmol) in anhydrous diethyl
ether (40 ml) was stirred for 1 d at room temperature.
To this solution was added anhydrous THF (50 ml) and
then (dimethylchlorogermyl)dimethylchlorosilane 4.11 g
/
(18 mmol). After it was stirred for 51 h for 35Á40 8C, the
/
mixture was hydrolyzed with water. The organic layer
was extracted with diethyl ether and dried over Na2SO4.
After the solvent had been evaporated, the residue was
diluted with aetone to cause crystallization of pure
1,1,2,2-tetramethyl-1-germa-2-sila-3,4,5,6-tetraphenyl-
diffractometer utilizing graphite-monochromated MoÁ
/
˚
Ka (lꢁ0.71073 A) radiation. The structures were
/
solved by direct methods using SIR-92 [18] and refined
with all data on F2 by means of SHELXL-97 [19]. A
refinement was performed by a SILICON Graphics O2
with maXus. CH2Cl2 and other solvents were purified
and dried as reported in the literature.
cyclohexa-3,5-diene (4.23 g, 8.2 mmol, 70%): m.p.: 172Á
/
1
173 8C. H-NMR (d, CDCl3) 0.28 (s, 6H), 0.32 (s, 6H),
6.72Á6.84 (m, 14H), 6.94Á7.01 (m, 2H), 7.08Á7.14 (m,
4H); 13C-NMR (d, CDCl3) ꢂ
4.7, ꢂ3.7, 124.3, 124.5,
125.1, 125.2, 126.6, 127.5, 127.8, 128.3, 129.6, 141.0,
/
/
/
/
/

92
K. Mochida et al. / Journal of Organometallic Chemistry 673 (2003) 84Á94
/
141.6, 141.9, 142.9, 143.6, 145.8, 149.0, 152.4; MS m/z
518 (74Ge); UV (cyclohexane) lmax 352 nm (log o 3.88).
Anal. Calc. for C32H32GeSi: C, 73.05; H, 6.54. Found:
C, 73.37; H, 6.21.
125.0, 125.8, 126.8, 127.5, 129.6, 140.5, 143.0, 144.8,
154.3; MS m/z 488; UV (cyclohexane) lmax 274 nm
(log o 4.16). Anal. Calc. for C32H32OSi2: C, 78.64; H,
6.60. Found: C, 78.70; H, 6.46.
4.4. Preparation of 2,2,3,3-tetracyano-7,7-dimethyl-
1,4,5,6-tetraphenyl-7-silabicyclo[2.2.1]hept-5-ene (5)
4.7. Preparation of 1,1,3,3-tetramethyl-4,5,6,7-
tetraphenyl-2-oxa-1-germa-3-silacyclohepta-4,6-diene
(13)
A mixture of 1,1-dimethyl-2,3,4,5-tetraphenyl-1-sila-
cyclopenta-2,4-diene (0.41 g, 0.1 mol) and TCNE (0.13
g, 0.1 mmol) in CH2Cl2 (30 ml) was stirred for 3 d at
room temperature. After the solvent had been evapo-
rated, the residue was diluted with CH2Cl2 to cause
crystallization of pure 2,2,3,3-tetracyano-7,7-dimethyl-
1,4,5,6-tetraphenyl-7-silabicyclo[2.2.1]hept-5-ene (0.42
g, 0.75 mmol, 75.1%): dec. 170 8C. 1H-NMR (d,
A
mixture of 1,1,2,2-tetramethyl-1-germa-2-sila-
3,4,5,6-tetraphynycyclo-hexa-3,5-diene (0.26 g, 0.5
mmol) and m-chloroperoxybenzoic acid (0.17 g, 1.0
mmol) in diethyl ether (20 ml) was stirred for 4 h at
room temperature. After the solvent had been evapo-
rated, the residue was diluted with CH2Cl2 to cause
crystallization of pure 1,1,3,3-tetramethyl-4,5,6,7-tetra-
phenyl-2-oxa-1-germa-3-silacyclohepta-4,6-diene (0.19
CDCl3) 1.00 (s, 3H), 1.10 (s, 3H), 6.78Á
/
7.30 (m,
20H); 13C-NMR (d, CDCl3) ꢂ
/3.0, 3.9, 54.4, 59.3,
11.3, 113.5, 127.4, 127.5, 128.6, 128.9, 129.7, 130.0,
132.4, 134.2, 144.4; MS m/z 416 (-TCNE); UV (CH2Cl2)
lmax 264 nm (log o 4.43). Anal. Calc. for C36H26N4Si: C,
79.67; H, 4.83; N, 10.32. Found: C, 79.46; H, 4.94; N,
10.27.
g, 0.35 mmol, 69.8%): 1H-NMR (d, CDCl3) ꢂ
7.20 (m, 20H);
/0.02
(broad, s, 3H), 0.70 (broad s, 3H), 6.69Á
/
13C-NMR (d, CDCl3) 1.56, 125.0, 125.8, 126.8, 127.5,
129.6, 140.5, 143.0, 144.8, 154.3; MS m/z 534; UV
(cyclohexane) lmax 275 nm (log o 4.09). Anal. Calc. for
C32H32OGeSi: C, 72.07; H, 6.05. Found: C, 72.38; H,
6.29.
4.5. Preparation of 2,2,3,3-tetracyano-7,7-dimethyl-
1,4,5,6-tetraphenyl-7-germabicyclo[2.2.1]hept-5-ene (8)
A mixture of 1,1-dimethyl-2,3,4,5-tetraphenyl-1-ger-
macyclopenta-2,4-diene (0.23 g, 0.5 mol) and TCNE
(0.063 g, 0.5 mmol) in CH2Cl2 (30 ml) was stirred for 3 h
at room temperature. After the solvent had been
evaporated, the residue was diluted with CH2Cl2 to
cause crystallization of pure 2,2,3,3-tetracyano-7,7-di-
methyl-1,4,5,6-tetraphenyl-7-germabicyclo[2.2.1]hept-5-
ene (0.26 g, 0.43 mol, 87.4%): dec. 150 8C. 1H-NMR (d,
4.8. Reaction of 1,2-disilacyclohexa-3,5-diene (1) with
TCNE
A solution of 1,1,2,2-tetramethyl-1,2-disila-3,4,5,6-
tetraphenylcyclohexa-3,5-diene (1) (0.18 g, 0.4 mmol)
and TCNE (0.4 mmol) in CH2Cl2 (6 ml) was placed in a
Pyrex tube (fꢁ1 cm) under argon and sealed. The
/
CDCl3) 1.17 (s, 3H), 1.36 (s, 3H), 6.79Á
/
7.31 (m, 20H);
13C-NMR (d, CDCl3) ꢂ
/
1.56, ꢂ1.51, 8.25, 8.33, 55.4,
/
color of the solution changed from yellowish-green to
reddish-brown. The reaction mixture was heated at
90 8C for 3 h to give 4-amino-5,6-dicyano-2,2,11,11-
tetramethyl-1,8,9,10-tetraphenyl-3-aza-2,11-disilatricy-
clo[6.2.1.03,7]undeca-4,6,9-triene (4, 38%), 2,2,3,3-tetra-
cyano-7,7-dimethyl-1,4,5,6-tetraphenyl-7-silabicy-
clo[2.2.1]hept-5-ene (5, trace), 1,1,3,3-tetramethyl-
4,5,6,7-tetraphenyl-2-oxa-1,3-disilacyclohepta-4,6-diene
(6, 16%), and some unidentified products. The rest of 1
(40%) was recovered unchanged from the CH2Cl2
solution. Concentration of the reaction mixture by
evaporation of CH2Cl2 followed by both preparative
62.1, 107.2, 11.3, 113.5, 127.3, 129.8, 130.1, 130.3, 133.0,
134.6, 144.2; MS m/z 460 (-TCNE) (74Ge); UV (CH2Cl2)
lmax 266 nm (log o 3.96). Anal. Calc. for C36H26N4Ge:
C, 73.63; H, 4.46; N, 4.46. Found: C, 73.53; H, 4.44; N,
4.44.
4.6. Preparation of 1,1,3,3-tetramethyl-4,5,6,7-
tetraphenyl-2-oxa-1,3-disilacyclohepta-4,6-diene (6)
A mixture of 1,1,2,2-tetramethyl-1,2-disila-3,4,5,6-tet-
raphenylcyclohexa-3,5-diene (0.33 g, 0.7 mmol) and m-
chloroperoxybenzoic acid (0.24 g, 1.0 mmol) in diethyl
ether (30 ml) was stirred for 4 h at room temperature.
After the solvent had been evaporated, the residue was
diluted with CH2Cl2 to cause crystallization of pure
1,1,3,3-tetramethyl-4,5,6,7-tetraphenyl-2-oxa-1,3-disila-
cyclohepta-4,6-diene (0.26 g, 0.38 mmol, 76.1%): 1H-
GPC and TLC (silica gel) gave pure 4. 4: m.p.: B
220 8C; 1H-NMR (d, CDCl3) 0.10 (s, 3H), 0.17 (s,
3H), 0.61 (s, 3H), 0.65 (s, 3H), 4.03 (broad s, 2H), 6.45Á
7.16 (m, 20 H); 13C-NMR (d, CDCl3) ꢂ
5.7, ꢂ2.3, ꢂ
1.4, ꢂ0.9, 15.2, 18.4, 93.6, 103.7, 125.5, 126.1, 126.3,
/
/
/
/
/
/
126.6, 127.1, 128.0, 129.4, 130.6, 131.4, 136.5, 137.5,
137.7, 139.0, 146.3, 148.7; MS m/z 602; UV (CH2Cl2)
lmax 277 nm (log o 3.43).
NMR (d, CDCl3) ꢂ
/
0.02 (broad, s, 3H), 0.70 (broad s,
7.14 (m, 20H); 13C-NMR (d, CDCl3) 1.56,
3H), 6.79Á
/

K. Mochida et al. / Journal of Organometallic Chemistry 673 (2003) 84Á
/94
93
4.9. Reaction of 1,2-digermacyclohexa-3,5-diene (2)
with TCNE
93.5, 99.9, 113.3, 114.1, 125.1, 126.1, 126.2, 126.4, 127.1,
127.5, 128.1, 129.4, 130.8, 131.4, 137.1, 138.0, 138.2,
139.0, 139.6, 143.8, 146.0, 146.4, 148.8; MS m/z 648; UV
1
A solution of 1,1,2,2-tetramethyl-1,2-digerma-3,4,5,6-
tetraphenylcyclohexa-3,5-diene (2) (0.22 g, 0.4 mmol)
and TCNE (0.4 mmol) in CH2Cl2 (6 ml) was placed in a
Pyrex tube under argon and sealed. The color of the
solution changed from yellow to green. The Pyrex tube
was heated at 90 8C for 4 h to give 4-amino-5,6-dicyano-
2,2,11,11-tetramethyl-1,8,9,10-tetraphenyl-3-aza-2,11-
digermatricyclo[6.2.1.03,7]undeca-4,6,9-triene (7, 3%),
2,2,3,3-tetracyano-7,7,dimethyl-1,4,5,6-tetraphenyl-7-
germabicyclo[2,2,1]hepta-5-ene (8, 9%), 1,1,3,3-tetra-
methyl - 4,5,6,7 - tetraphenyl - 2 - oxa - 1,3 - digermacyclo-
hepta-4,6-diene (9, 16%), 2,2,4,4,6,6-hexamethyl-1,3,5-
trioxa-2,4,6-trigermacyclohexane (10, trace), and some
unidentified products. The rest of 2 (45%) was recovered
unchanged from the CH2Cl2 solution. Concentration of
the reaction mixture by evaporation of CH2Cl2 followed
by both preparative GPC and TLC (silica gel) gave pure
7. 7: 1H-NMR (d, CDCl3) 0.33 (s, 3H), 0.71 (s, 3H), 0.72
(CH2Cl2) lmax 345 nm (log o 3.27). 12: H-NMR (d,
CDCl3) 0.19 (s, 3H), 0.27 (s, 3H), 0.65 (s, 3H), 0.78 (s,
3H), 3.98 (broad s, 2H), 6.45Á
/
7.16 (m, 20H); 13C-NMR
(d, CDCl3) ꢂ1.8, 0.9, 2.0, 2.2, 3.9, 12.7, 71.6, 106.3,
/
112.7, 113.9, 125.8, 126.3, 127.1, 127.4, 127.9, 128.1,
128.2, 129.1, 130.5, 130.7, 134.8, 137.5, 138.8, 139.2,
145.4, 146.3, 154.7; MS m/z 646; UV (CH2Cl2) lmax 269
nm (log o 4.48).
4.11. Reactions of 1,2-dimetallacyclohexa-3,5-dienes
with TCNE in the presence of trapping reagents
As a representative example, the reaction of 1,1,2,2-
tetramethyl-1,2-disila-3,4,5,6-tetraphenylcyclohexa-3,5-
diene (1) with TCNE in the presence of 2,3-dimethyl-
1,3-butadiene is described. A solution of 1,1,2,2-tetra-
methyl-1,2-disila-3,4,5,6-tetraphenylcyclohexa-3,5-diene
(1) (0.01 mmol), TCNE (0.01 mmol), and 2,3-dimethyl-
buta-1,3-diene (0.08 mmol) in CD2Cl2 (0.6 ml) was
placed in a NMR tube under argon and sealed. The
color of the solution changed from yellowish-green to
reddish-brown. The reaction products were examined by
(s, 3H), 1.10 (s, 3H), 3.86 (broad s, 2H), 6.76Á
/
7.65 (m,
20H); 13C-NMR (d, CDCl3) ꢂ
/
0.5, 0.8, 1.7, 1.9, 56.2,
76.6, 93.2, 94.6, 113.1, 114.2, 126.3, 126.3, 127.1, 127.3,
128.1, 128.2, 128.3, 130.4, 130.6, 130.8, 135.1, 137.7,
138.8, 139.2, 144.6, 145.0, 146.5, 155.0; MS m/z 692; UV
(CH2Cl2) lmax 287 nm (log o 3.49).
NMR and GCÁMS spectra analysis.
/
4.10. Reaction of 1-germa-2-silacyclohexa-3,5-diene (3)
with TCNE
Acknowledgements
The authors thank Mitsubishi Material Co., Ltd, for
providing us tetrachlorogermane.
A solution of 1,1,2,2-tetramethyl-1-germa-2-sila-
3,4,5,6-tetraphenylcyclohexa-3,5-diene (3) (0.207 g, 0.4
mmol) and TCNE (0.4 mmol) in CH2Cl2 (6 ml) was
placed in a Pyrex tube (fꢁ1 cm) under argon and
/
References
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tetramethyl-1,8,9,10-tetraphenyl-3-aza-11-germa-2-sila-
tricyclo[6.2.1.03,7]undeca-4,6,9-triene (11, 5%), 4-amino-
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dentified products were also detected. The rest of 3
(46%) was recovered unchanged from the CH2Cl2
solution. Concentration of the reaction mixture by
evaporation of CH2Cl2 followed by both preparative
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