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Competing Reactions of Silenes [2+2] [4+2] and [6+2] Cycloadditions with Cycloheptadiene and Cycloheptatriene.

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Fe-P edge. The structure of the trigold cluster 3 (Fig. 2 left) is
simply derived from addition of a third (Ph,P)Au+ fragment
(Au3) to a Fe,P face of the cluster As can be seen by comparing
the two structures in Figure 2, 4 is formally constructed by “insertion” of Au4 into the Aul -Au3 bond.
a
p2
Fe3
W
[5] a) F. Scherbaum, A. Grohmann, B. Huber, C. Kriiger, H. Schmidbaur,Angew.
Chem. 1988, 100, 1602; Angew. Chem. Int. Ed. Engl. 1988, 27, 1544; b)F.
Scherbaum, A. Grohmann, G. Miiller, H. Schmidbaur, ibid. 1989,101,464 and
1989,28,463; c) 0 . Steigelmann, P. Bissinger, H. Schmidbaur, ibid. 1990,102,
1473 and 1990,29, 1399.
[6] A. Grohmann, J. Riede, H. Schmidbaur, Nature 1990,345, 140.
[7] a) H. Schmidbaur, G. Weidenhiller, 0 . Steigelmann, Angew. Chem. 1991, 103,
442; Angew. Chem. Int. Ed. Engl. 1991,30,433; b) E. Zeller, H. Schmidbaur,
J. Chem. Sac. Chem. Commun. 1993, 69.
[S] a) K. P. Hall, D. M. P. Mingos, Prog. Inorg. Chem. 1984. 32, 237; b) I. D.
Salter, Adv. Organomet. Chem. 1989, 29. 249.
[9] D. L. Sunick, P. S. White, C. K. Schauer, Organometallics 1993, 12, 245.
[lo] D. L. Sunick, P. S. White, C. K. Schauer, Inorg. Chem., in press.
[Ill M. Brockhart, B. Grant, A. F. Volpe, Jr., Organometallics 1992, 11, 3920.
[I21 [4][BAr,] .1.5 Et,O: a =12.918(3), b =19.863(9), c = 23.256(4) A, a =
89.94(2), fl = 91.57(2), y = 94.31(3)” at -150°C. Space group PT ( Z = 2).
Least squares refinement of 729 least squares parameters and 7934 reflections
converged at R ( R J = 0.066 (0.069). Further details of the crystal structure
investigation are available on request from the Director of Cambridge Crystallographic Data Centre, 12 Union Road, GB-Cambridge CB2lEZ (UK), on
quoting the full journal citation.
[I31 E. Zeller, H. Beruda, A. Kolb, P. Bissinger, J. Riede, H. Schmidbaur, Nature
1991, 352, 141.
[14] H. Schmidbaur, E. Zeller, G. Weidenhiller, 0. Steigelmann. H. Beruda, Inorg.
Chem. 1992.31, 2370.
Fig. 2. View onto the Fe, plane of the ball and stick drawings of the Fe,P[Au,P,]
core of 3 (left) and Fe,P[Au,P,j core of 4 (right).
A C,, symmetry structure (with a square-planar array of Au’
ions) instead of & symmetry structure was recently predicted to
be the most stable for the hypothetical [P{Au(PH,)},]+ cluster,[4e1and is observed experimentally for [As{Au(PP~,)),]+.[’~~
Given the large number of possible other arrangements of gold
atoms involving different modes of bonding to the Fe, triangle,
the configuration adopted by the [Au,(PPh,),14+ fragment in 4
is likely governed by the stability of the nearly square-planar
arrangement of Au’ ions. Remarkably, the geometry of the Au,
array in 4 is similar to that adopted in the related monoarylphosphorus dication, [(~-tolyl)P{Au(PPh,)},]~+(Au ... Au =
2.97(5), Au-P, = 2.37(1), Au-PPh, = 2.293(7) A).[141Thus, 4
can be viewed either as a [{Au(PPh,)),l4+ derivative of the
[Fe,(CO),(p,-P)]3- cluster or as an Fe,(CO), derivative of
[P{Au(PPh,)},]+, in which bonding to the Fe, array requires six
electrons from the P3- ion. Such a cluster is not readily
amenable to classical bonding descriptions.
Experimental Procedure
Reactions were performed under purified nitrogen with standard Schlenk techniques.
4[BAr,]: Solid samples of purple-red 3 (57.5 mg, 0.031 mmol) and Na+[BAr,](27.4 mg, 1 equiv) were combined in a flask, and a freshly prepared solution of
[(Ph,P)Au] [BF,] [I41 in 10 mL of THF (prepared from 0.031 mmol each of Ag[BF,]
and (Ph,P)AuCI in the dark) at -70°C was filtered onto the solids. A new deep
purple color was observed as 3 dissolved. After stirring for 5 min, conversion to 4
was complete (as indicated by 1R spectroscopy). The solvent was removed under
vacuum and 4[BAr,] was extracted into Et,O. The solution was filtered, and then
layered with pentane to yield crystals of 4[BAr,]. Isolated yields: 56mg (57%).
‘ H N M R (300 MHz, [D,]THF): 6 =7.9, 7.7 (br s, Ar protons) 7.25, 7.50 (m, Au(PPh,));IR(Et,O): vc0 = 2041 cm-’ vs, 1993vs, 1983 s, 1974m, 1936w. br;correct
elemental analysis for C,,,H,,Au,BF,,Fe,O,P,.
Received: July 13.1993 [Z 6210 IE]
German version: Angew. Chem. 1994, 106, 108
[I] M. Jansen, Angew. Chem. 1987.99,1136; Angen. Chem. Int. Ed. Engl. 1987,26,
1098.
[2] S. S. Pathaneni. G. R. Desiraju, J. Chem. Sac. Dalton Trans. 1993, 319.
[3] A. Gorling, N. Rosch, D. E. Ellis, H. Schmidbaur, Inorg. Chem. 1991,30,3986.
[4] a) P. Pyykko, J.-P. Desclaux, Acc. Chem. Res. 1979, 12, 276; b) P. Pyykko,
Chem. Rev. 1988,88,563;c) P. Pyykko, Y. Zhao, Angew. Chem. 1991,103,622;
Angeh,. Chem. Int. Ed. Engl. 1991, 30, 604; d) J. Li, P. Pyykko, Chem. Phys.
Letr. 1992, 197, 586; e) Inorg. Chem. 1993, 32, 2630.
Angew. Chem. Int. Ed. Engl. 1994, 33, N o . 1
0 VCH
+
Competing Reactions of Silenes: [2 21,
[4 + 21, and [6 + 21 Cycloadditions with
Cycloheptadiene and Cycloheptatriene**
Wolfgang Ziche, Claudia Seidenschwarz,
Norbert Auner,* Eberhardt Herdtweck,
and Norbert Sewald
Dedicated to Professor Ernst Otto Fischer
on the occasion of his 75th birthday
+
(Hetero)olefins usually undergo [2 + 21 and [4 21 cycloadditions, while examples of thermal [6 + 21 cycloadditions
are comparatively rare.”] “Dichloroneopentylsilene” 1 is a
Cl,Si=CHCH,tBu
1
building block for synthetic organosilicon chemistry, which is
characterized by a highly polar Si=C bond and a strongly electrophilic silicon atom. These properties are mainly responsible
for its unique reactivity: on the one hand, 1 reacts with relatively
unreactive dienes like naphthalene[21 and f ~ r a n s [ to
~ ] give
Diels-Alder adducts and, on the other hand, it undergoes
[2 + 21 cycloadditions with disubstituted acetylenes to give silacycl~butenes.[~]
The reaction of 1 with 1,3-butadienes leads selectively to mono~ilacyclobutanes,[~1
and upon treatment of 1
with 1,3-cyclohexadiene the [2 + 21 and [4 + 21 cycloadditions
compete with each other;[61in both cases the [2 + 21 adducts are
converted thermally into Diels- Alder and retro-ene products.
We report here on the cycloadditions of 1 with 1,3-cycloheptadiene and 1,3,5-cycloheptatriene.
[*] Prof. N. Auner, Dr. W. Ziche, Dr. C. Seidenschwarz, Dr. E. Herdtweck,
Dr. N. Sewald
Anorganisch-chemisches Institut der Technischen Universitat Miinchen
Lichtenbergstrasse 4, D-85747 Garching (FRG)
Telefax: Int. code + (89)3209-3743
[**I Silaheterocycles, Part 30. This work was supported by the VolkswagenStiftung, the Deutsche Forschungsgemeinschaft, and the Fonds der Chemischen Industrie. -Part 29: W. Ziche, V. Popkova, C. Seidenschwara,N. Sewald,
E. Herdtweck, N. Auner, Organometallics, submitted.
Verlagsgesellschaff mbH. D-69451 Weinheim, 1994
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COMMUNICATIONS
Reaction of silene 1, prepared in situ from trichlorovinylsilane and tBuLi, with cycloheptadiene produces a mixture of
the [2 + 21 and [4 + 21 cycloadduct isomers, 2 and 3, respectively, which is not separable by di~tillation."~
To separate the struc-
Surprisingly, the reaction of 1 with 1,3,5-~ycloheptatriene
leads to four [2 + 21 ( 5 ) and two [6 + 21 cycloadducts (6)
(Scheme 1, for relative amounts see Table 1).
@&
Table 1. Selected spectroscopic data[a] for ( € ) - 4 , 5 . 6 , and endo-7.
SiC1,
(EIZ)- 2
exo/endo- 3
tural isomers the mixture was treated with phenylmagnesium
bromide. In this reaction only the two chloro substituents of the
[2 + 21 adducts are replaced by two phenyl groups giving 4. This
4
selective reactivity is analogous to that of the corresponding
cyclohexadiene adductsI61and is attributed to the angles at the
silicon atom in the monosilacyclobutane subunits (see also
Fig. l).[8-101Compound 4 was recrystallized from pentane and
shown by X-ray structure analysis (Fig. 1) to be the diphenylsubstituted [2 + 21 isomer (E)-4.f8]
C23
(€1-4: 'HNMR:6=0.78(s,9H),0.80-2.20(m,8H),2.50(m,2H),3.00(m,1H),
5.47 (m, l H ) , 5.55 (m, 1H). 7.35-7.45 (m, 4H), 7.55--7.67 (m, 6H); 1 3 C N M R :
6 = 25.07, 26.40, 26.91 (CH,), 29.86 (C(CH,),), 30.65 (C(CH,),), 43.96 (CH,C(CH,),), 28.01, 29.62, 43.95 (CH), 133.15. 136.60 (C), 125.39. 127.82, 127.83,
125.60. 133.62, 135.95, 135.96, 136.12, 136.13 (CH); 24SiN M R : 6 = 2.3 ( ( 2 ) - 4 :
5.4);MS(70eV):m/z:360(M+,3%),209(Ph2SiCHCH:,loo), l83(Ph2SiH+,39),
266 (M' - C,Hl,, 36), 292 (M' - C,H,, 11). 293 ( M ' - C,H,, 3).
5 : 29Si NMR: 6 = 12.6(27%), 13.3 (5),17.5 (4). 18.4(32); GC-MS: mjz: ( M ' . 3 %),
217 ( M + - IBU, 81, 181 (M' - C,H,, 5). 91 (C,H:, 5 9 , 57 (fBu, 100).
(€)-cis-5: ' H N M R : 6 = 0.90 (s. 9 H ; C(CH,),), 1.37, 1.56 (CH,-C(CH,),), 2.10
(m, 1 H ; Si-CH-CH,tBu). 2.40 (m, 1 H ; Si-CH), 2.45 (m, 1 H ; Si-CH-CH), 2.22 (m,
2 H ; CH,), 5.72-6.00 (m. 4 H ; CH=CH-CH=CH);
NMR: 6 = 29.75
(C(CH,),). 30.26 (C(CH,),), 26.84 (CH,). 41.60, 46.74. 48.04 (CH), 42.46 (CH,C(CH,),). 125.17. 127.31. 135.24. 135.75 (=CH); 29SiNMR: 6 =18.4.
(Z)-cis-5:' H NMR: 6 = 0.90(s, 9H;C(CH,),), 1.37, 1.56(CH2-C(CH,),). 1.70(m,
1 H ; Si-CH-CH,rBu), 1.95 (m.1 H ; Si-CH), 2.21 (m. 1 H ; Si-CH-CH), 2.34,2.57 (m,
2 H ; CH,), 5.68-5.90 (m, 4 H ; CH=CH-CH=CH); I3C N M R : 6 = 29.75
(C(CH,),). 30.96 (C(CH,),), 31.41 (CH,). 40.04, 42.24, 43.40 (CH), 43.29 (CH,C(CH,),). 124.79, 124.98, 134.16. 135.02 (=CH); % i N M R : 6 =12.6.
(E)/(Z)-truns-5:13CN M R : 6 = 29.75 (C(CH,),). 30.57. 30.77 (C(CH,),), 36.81,
40.33 (CHz-C(CH,),), 25.90, 31.27 (CHZ), 36.09, 38.31, 39.59, 40.44, 43.33, 54.04
(CH), 124.90, 128.52, 128.62, 132.78, 134.41, 135.15, 135.30 (=CH); '?3 N M R :
6 =13.3. 17.5.
endo-6: ' H NMR: 6 = 0.90 (s, 9 H ; C(CH,),). 1.58 (m, 2 H ; CH,-C(CH,),), 1.84
(m, 1 H ; Si-CH-CH,fBu), 1.98 (m31 H ; CH,). 2.19 (m, 1 H ; CH,), 2.51 (m, 1H ;
Si-CH). 2.95 (m, 1 H ; Si-CH-CH), 5.65, 5.69, 5.80, 5.93 (div. m, 4 H ,
CH=CH-CH=CH); 13CNMR: 6 = 29.71 (C(CH,),), 30.89 (C(CH,),), 31.77
(CH,), 33.89 (Si-CH), 37.54 (CH,-C(CH,),), 44.90 (Si-CH-CH), 46.35 (Si-CHCH,tBu), 123.56, 123.54, 126.39, 134.07 (=CH); ' % N M R : 6 = 46.5 (22%); MS
(70eV): mjz: 274 ( M + . 6%), 239 ( M + - C l , 6), 217 ( M + - tBu, 5), 181
(M' - C7H,, 15). 91 (C,H:. 56), 57 ( ~ B u100).
,
exo-6: ' H NMR: 0.90(s,9H:C(CH3),), 1.22, 1.62(m,2H;CHz-C(CH,),), 1.34(m,
1 H ; Si-CH-CH,tBu), 1.75 (m. 1 H ; CH,), 2.10 (m, 1 H; CH,), 1.34 (m, 1 H ; Si-CH),
2.46 (m, 1 H ; Si-CH-CH), 5.65, 5.73, 5.83, 5.90 (div. m, 4 H ,
CH = C H - CH = CH); 13C N M R : 6 = 29.75 (C(CH,),), 31.66(C(CH3),), 29.04
(CH,), 34.51 (Si-CH), 45.08 (CH,-C(CH,),), 47.52 (Si-CH-CH), 42.74 (Si-CHCH,lBu), 123.51, 123.89, 132.40. 133.35 (=CH); ,'Si NMR: 6 = 41.7 (10%); MS
(70 eV): m / z see endo-6.
endo-7: ' H N M R : 6 = 0.84 (s, 9 H ; C(CHJ3), 1.50 (dd, J = 14.6, 3.0 Hz, 1 H ; CH,C(CH,),), 1.85 (dd, J =14.6, 14.6 Hz, 1 H ; CH,-C(CH,),), 2.05-2.30 (m,3 H ;
CH,, Si-CH-CH,tBu). 2.62 (m. 1 H ; Si-CH), 3.18 (m. 1 H ; Si-CH-CH), 5.50, 5.755.95 (m, 4H, CH=CH-CH=CH), 7.15-7.40 (m. 6 H ; m-Ph, p W ) , 7.50-7.55 (m,
4 H , O-Ph); I 3 C N M R : 6 = 29.90 (C(CH,),), 32.02 (C(CH,),), 34.72, 38.28 (CH,),
31.32, 41.19, 46.48 (CH), 123.70, 132.43 ( = C ) . 121.56, 126.65, 127.06, 127.17,
127.73, 127.93, 129.13. 129.20, 134.18, 134.87, 135.47, 135.72, 136.93, 137.90
(=CH); 29SiNMR: 6 = 17.5; MS (70eV): mjr: 358 ( M + . 29%), 301 ( M + - tBu,
IBu - C,H,, 74), 183 (Ph,SiHf, loo), 105
14), 279 (M' - C,H:, 32). 209 (M'
(C,H:, 29). 57 (IBu. 100).
~
c2
[a] ' H N M R : CDCI,, 100, 270, and 360 MHz; 13C NMR: 25.14 MHz, CDCI,,
29SiNMR: 53.64 MHz, CDCI,. GC-MS at 70 eV.
Fig. 1. Crystal structure of (E)-4 (ORTEP representation). Selected distances [pm]
and angles ["I: Si-Cl 188.0(1), Sic31 188.4(1), Si-C11 187.3(1), Si-C21 187.5(1),
C1-C2 152.4(1), Cl-C37 158.9(1), C31-C37 156.4(1), Cl-Sic31 79.45(5), Si-Cl-C37
85.88(7), Si-C31-C37 86.44(7), Cl-C37-C31 99.46(9), C1 1-Si-C21 110.48(5), C31C37-C36 118.52(11), Si-Cl-C2 126.72(9), Si-C31-C32 118.51(9).
The most striking structural features of (E)-4 are the nonplanar central silacyclobutane unit and the small endocyclic angles ;
the angle at silicon (79.45 ") is significantly smaller than at the
opposite carbon atom (99.46"). These values are normal for
silacyclobutane derivatives.[']
78
0 VCH
Verlugsgesellschaft mbH, 0-69451 Weinheim. 1994
The 29Si NMR chemical shifts of the products, before and
after distillation, allow clear assessment of the type of cycloadducts formed. The signals for 5 lie between 6 = 12.6 and 18.4,
characterizing these compounds as the [2 + 21 cycloadducts.
For 6 the signals at 6 = 41.7 and 46.5 have chemical shifts typical of dichlorosilacyclopentanes, thus identifying the two compounds as the exolendo [6 + 21 cycloadduct isomers. Formation
of both the [6 + 21 and the [2 + 21 cycloadducts by a concerted
process is forbidden by the Woodward- Hoffmann rules." No
[4 + 21 cycloadducts are formed in the reaction sequence shown
in Scheme 1 ; their "Si NMR signals would be expected in the
region 6 % 25-30.[61
OS70-0833/94j0101-0078 $ 10.00+ .2SjO
Angew. Chem. I n l . Ed. Engl. 1994, 33, No. I
COMMUNICATIONS
Cl@CH=CH,/
LitBu/
0
C-C bond lengths (d = 151.9 pm). The bicyclo[4.2.1]-2,4-nonadiene unit is somewhat distorted in comparison to the analogous
all-carbon framework as a consequence of the larger atomic
radius of the Si
The [2 + 21 and [6 + 21 cycloadditions of silene 1 reported
here, as well as the isomerizations, can be explained in terms of
zwitterionic intermediates (Scheme 2). The strongly polarized
(2)-cis- 5
@)-cis-
C1,SiCH=CH2+LitBu
1
5
-LEI
C1 Si-CHCH,tBu
1
- 8
endo- 6
4x0-
8
Scheme 1. Reaction of' 1 with 1,3,5-cycloheptatriene.
The separation of the structural isomers of 5 and 6 into individual components was successfully achieved in a chemical fashion :
- When a mixture of 5 and 6 was stored at room temperature
for several months, endo/exo-6 (endolexo 75/25) was formed
exclusively. Thermolysis of this mixture in solution (toluene
110 "C, 120 h) or neat (200 "C, 120 h) significantly accelerated
the isomerization of 5 into 6. The endolexo ratio for 6 was
then 85/15. Compound 6 was characterized by 2D NMR
spectroscopy.
- Derivatizing 516 with phenylmagnesium bromide gave almost
selective isomerization to the diphenyl-substituted [6 + 21 cycloadduct, endo-7, which is crystalline and was characterized
by X-ray structure analysis (Fig. 2).(121
3. 4
Scheme 2. Possible reaction pathways for the formation and rearrangement of the
cycloadducts of 1.
and electrophilic silene 1 attacks one of the terminal carbons in
the conjugated w-electron system of cycloheptadiene and cycloheptatriene, forming the zwitterions A and B, respectively. Carbocation B is more effectively stabilized than A by greater delocalization, which thereby allows more time for stereochemical
orientation of the dipolar system and a number of possible
modes of ring closure. The attack of the carbanion at the terminal carbon atom of the cationic propenyl and pentadienyl moieties leads in both cases to rapid ring closure, giving the [2 + 21
cycloadducts 2 and 5 preferentially. Competing with this is the
formation of the Diels-Alder adduct 3, in a slower step, and the
[6 + 21 cycloadduct 6,which is mainly produced as the thermodynamically more stable endo isomer.[141The greater stability of
B is also confirmed by the fact that the ( Z )[2 21 adduct 5 does
not thermally isomerize to give the retro-ene compound. This
isomerization was observed for the related compounds formed
from 1 with b~tadienes,'~]
1,3-~yclohexadiene,[~~
and 1,3-cycloheptadiene.[' 51
These results open up wide-ranging possibilities for the transformation of the regiospecific but stereoisomeric [2 + 21 adducts
of silene 1 into stereochemically pure products with nucleophilic
reagents. In this way the whole process becomes stereoselective.
+
c2
c3
c35
c34
Fig. 2. Crystal structure ofendo-7 (ORTEP representation). Selecteddistances [pm]
and angles ["I: Si-CI 190.3(1), Si-C7 190.3(1), Si-C21 187.4(1), Si-C31 186.9(1),
C7-C9 153.3(1). C6-C7 155.8(1), CS-C6 149.1(2), C1-C2 148.1(2), CI-CI 153.0(1),
C6-C8 153.8(1), CI-Si-C7 96.35(6), Si-C7-C6 103.79(8),Si-C7-C9 118.49(9),Si-C1C2 113.92(10), C2-CI-C8 113.93(14), C5-C6-C7 114.03(13).
Experimental Procedure
516: A solution of tBuLi (I .7 M in pentane, 36.0 mL, 60.0 mmol) was added dropwise
+
As is clear from Fig. 2, the endo isomer of the [6 21 cycloadduct 7 shows no striking structural features; the C6-C7 bond
length is 155.9(2) pm, a little longer than the average of the other
Angew,. Chem. In!. Ed. E n d . 1994, 33, No. 1
0 VCH
to amixture of CI,SiCH=CH, (9.6 g, 60.0 mmol) and 1,3-cycloheptatriene (11.0 g,
119.6 mmol) in pentane (SO0 mL) at -78 "C. After the mixture was allowed to
warm to room temperature, it was stirred for another 12 h. After filtration the
mixture was distilled to give a mixture of 516 ( I O O T , lo-' mbar) as a colorless
viscous liquid (9.3 g, 34.0 mmol, 56.6% yield).
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79
COMMUNICATIONS
4: A mixture of 2/3 (2.76 g, 10.0 mmol, prepared analogously to 5/6) was added to
phenylmagnesium bromide (60.0 mmol) in T H F (50 mL) and heated a t reflux for
60 h. The solvent was then distilled off and the residue extracted with pentane. 3
(105°C. 10-2mbar;0.85g,3.0mmol, 30% yield)and4(185"C.
mbar; 1.19 g,
3.3 mmol, 33% yield; E/Z = 66/34) were isolated by distillation. (E)-4 solidified in
the receiving flask and was recrystallized from pentane to give a white solid (m.p.
85 "C).
7: The derivatization of 5/6 with phenylmagnesium bromide (3.40 g. 12.5 mmol)
followed that of 4. Compound 7 was isolated as a thick oil by distillation (200°C.
mbar), which crystallized in the receiving flask. Recrystallization from pentane gave pure 7 as a white solid (3.58 g, yield 83.3 %, m.p. 97 C).
Received: July 21, 1993 [Z6224IE]
German version: Angew. Chem. 1994. 106. 93
[I] K. Mach, H . Antropiusovi, L. Petrusova, V. Hanus. F. Turecek, Tetrahedron
1984,40, 3295.
[2] N . Auner. C. Seidenschwarz. N. Sewald. E. Herdtweck, Angew. Chem. 1991.
103, 425; Angew. Chem. Inr. Ed. Engl. 1991. 30, 444.
[3] N. Auner. A. Wolff. Chem. Ber. 1993, 126, 575.
[4] N. Auner, C. Seidenschwarz, E. Herdtweck, Angew. Chen?. 1991, 103, 1172:
Angeiv. Chem. Inl. Ed. Engl. 1991.30, 1151; N . Auner. C.-R. Heikenwalder, C.
Wagner, Organometallirs 1993, 12, 41 35.
[5] N. Sewald, W Ziche, A. Wolff, N. Auner, Orgunometallics 1993, 12, 4123.
[6] N. Auner, C. Seidenschwarz, N. Sewald, OrganometaNirs 1992, 1 1 , 1137.
[7] Nonetheless the assignment of the N M R signals to the individual isomers is
possible by comparison to the N M R data from the cycloadducts of 1 with
cyclohexadiene[6]; the 29Si N M R spectrum in particular can be used to determine the product type (2: 6 =16.45, 16.47 and 3: 6 = 28.90. 29.70) as well as
the relative proportions of the individual stereoisomers (E)/(Z)-2, and esojendo-3). ( E ) / ( Z describes
)
the position of the neopentyl group on the silacyclobuVanes relative t o the vicinal bond of the annulated ring; elo/endo denotes the
stereochemistry ofthe neopeutyl group in the [4 + 21 and [6 + 21 cycloadducts;
and cisltrans refers to the stereochemistry of the fusion of the seven- and fourmembered rings in 5.
[8] X-ray crystal structure analysis of (E)-4 (C25H32Si),M = 360.6; colorless
prisms (0.51 x 0.18 x 0.26 mm3); triclinic space group. Pi (no. 2). a = 993.6(1).
h =1055.5(1), c =1152.2(1)pm, I = 69.51(1), f l = 85.13(1), 7=76.42(1)'. 25
reflections with high diffraction angles (20,in,n,ax=79.7'/96.8-), V = 1100 x
1 0 6 p m 3 , Z = 2,p,,,, =1.0X6gcm~3,Fo,,= 3 9 2 , ~=9,4cm-'.Acrystdlsuitable for X-ray analysis was mounted in a capillary with perfluorinated
polyether. Data were collected on an Enraf-Nonius CAD-4 four-circle diffractometer. Intensity data for 4381 reflections were collected a t room temperature
(21 * I ) "C with graphite-monochromated Cu,, radiation, i.
= 154.184 pm. Bj
2B-Scan, 1.0" < O < 70.0'. From these data 594 reflections with negative intensities were removed. After correction for minor decomposition (99 h, - 7.1 YO)
and an empirical absorption correction (8 Psi-scan data, C,,.,,.,
= 0.9591
1.000) there remained, after averaging 414 reflections (R,= 0.010(F)), 3580
independent reflections. One reflection, obviously a measurement error. was
discounted. The structure was solved using a combination of direct and indirect
methods, difference-Fourier maps and full-matrix least-squares techniques, All
heavy atoms were refined with anisotropic parameters and all hydrogen atom
positions with isotropic parameters. Refinement lead to convergence with
R = 0.065 and R , = 0.048 for 3579 reflections and 363 variables. A difference
map showed no residual electron density outside 0.70 and -0.35 e k 3 . All
calculations were performed on a micro-Vax-3100 computer with the STRUX
IV program package (MULTAN 11/82, ORTEP-11. PLATON, SCHAKAL,
SDP and SHELX-86)[16]. Further details of the crystal structure investigation
may be obtained from the Fachinformationszentrum Karlsruhe, D-76344
Eggenstein-Leopoldshafen (FRG) on quoting the depository number CSD56657, the names of the authors, and the journal citation.
[9] E. S. Mastryukov, 0. V. Dorofeeva, L. V. Vilkov, B. N . Sivin, S. J. Sivin, Zh.
Strukr. Khim. 1975, 16, 473; E. S. Mastryukov, 0. V. Dorofeeva, L. V. Vilkov,
N. A. Tarasenko, J Mol. Strucr. 1975, 27, 216; 0. A. D'yachenko, Yu. A.
Sokolova, L. 0. Atovmyan, N. V. Ushakov, Izv. Akad. Nuuk SSSR Ser. Khim.
1985, 34, 937.
[lo] B. Rempfer, G. Pfafferott, H. Oberhammer, N. Auner. J. E. Boggs, Acta Cheni.
Scand. Ser. A 1988, 42, 352.
[ l l ] R. B. Woodward, R. Hoffmann, J. Am. Chem. SOC.1965.87, 395.
[12] X-ray crystal structure analysis of 7 (C2sH30Si),M = 358.6; colorless crystal
fragments; triclinic space group, Pi (no. 2). a = 993.0(2), h = 1067.8(3).
c =1123.5(2)pm, 1 = 92.69(1). fl =101.31(1), y =113.86(1)", 25 reflections
with high diffraction angles (20,,,,,,, = 35.0"/42.9"), V =lo58 x lo6 pm',
Z = 2, p.,,. =1.126 g ~ m - F,,,
~ . = 392, p =1.1 cm-'. A crystal suitable for
X-ray analysis was mounted in a capillary with perfluorinated polyether. Data
were collected on an Enraf-Nonius CAD-4 four-circle diffractometer. Intensity
data for 3934 reflections were collected at room temperature (21 f 1) "C with
graphite-monochromated Mo,, radiation, A = 71.073 pm, o-scan, 1.O' < 0 <
25.0'. From these data 647 reflections with negative intensity were removed;
[I31
[14]
[I51
[16]
there remained 31 15 independent reflections. One reflection, obviously a measurement error, was ignored. The structure was solved using a combination of
direct, difference-Fourier maps and full-matrix least-squares techniques. All
heavy atoms were refined with anisotropic parameters and all hydrogen atom
positions with isotropic parameters. Refinement lead to convergence with
R = 0.058 and R , = 0.029 for 31 14 reflections and 355 variables. A differenceFourier map showed no residual electron density outside + 0.26 and
-0.35 e k 3 .
To the best of our knowledge the crystal structure of the parent compound,
bicyclo[4.2.1]-2.4-nonadiene,
has not been recorded. Structural comparisons:
P. Berno, A. Ceccon, F. Dapra, A. GambdrO, A. Venzo, P. Ganis, G. Valle, J.
Organomet. Chem. 1986,301, 161; Z . Goldschmidt, H. E. Gottlieb, E. Genizi,
D. Cohen, I. Goldberg. ihid. 1986, 301, 337; M. Parvez, K. S. Feldman, B. J.
Kosmider, Actu Crvsral/ogr. Serr. C 1987, 43, 1410.
For force-field calculations on the relative stability of the cycloadducts of
l/cyclohexadiene see ref.[6]. Preliminary results of the force-field calculations
on (E)/(Z)-ric-jrrans-5 show that all four isomers have approximately the same
stability.
C. Seidenschwarz. Dissertation, Technische Universitat Munchen, 1991.
W. Scherer, P. Kiprof, E. Herdtweck, R. E. Schmidt. M. Birkhan, W. Massa,
"Srrux IV", program system for the manipulation of X-ray data, Technische
Universitdt Munchen and Universitit Marburg, 1987 and 1990.
Synthesis of the First 2 H-1-Aza-Zphosphirene
Complexes**
Rainer Streubel,* Jorg Jeske, Peter G. Jones,
and Regine Herbst-Irmer
The elucidation of the mechanisms of preparatively important reactions is fascinating, but also often very time-consuming. The rearrangement I --t I1 of a q2-cyclopropene into a vinyl
carbene complex during the insertion of an alkyne into the
metal-carbene carbon bond of an arylidene(pentacarbony1)tungsten(0) complex was verified only recently,"] although this
reaction sequence has long been utilized in preparative work.[21
In attempting to synthesize the first derivatives of 2-aza-I-phospha-4-tungsta-I ,3-butadiene (III), which is isolobal with 11, we
have now surprisingly obtained exclusively 2 H-1-aza-2-phosphirene tungsten complexes of type IV, which are isomeric with
111 (Scheme 1).
+
80
'Q VCH Verlagsgesellschafi mbH, 0-69451 Weinheim, 1994
Scheme 1 .
I
II
m
N
To the best of our knowledge neither 2 H-I-aza-2-phosphirenes nor their cyclic isomers are known, nor have there been
previous reports of complexes containing these three-membered
rings as ligands.13]
["I Dr. R. Streubel, Dipl.-Chem. J. Jeske, Prof. Dr. P. G. Jones
Institut fur Anorganische und Analytische Chemie der
Technischen Universitat
Postfach 3329, D-38023 Braunschweig (FRG)
Telefax: Int. code (531)391-5387
Dr. R. Herbst-Irmer
Institut fur Anorganische und Analytische Chemie der Universitat Gottingen
[**I This work was supported by the Fonds der Chemischen Industrie and BASF
AG, Ludwigshafen.
+
0570-0833/94/0101-0080$ l0.00+.25/0
Angew. Chem. Int. Ed. Engl. 1994, 33. N o . I
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