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Cleavage of Silicon- and Germanium-Cobalt Bonds Change of Stereochemistry with Different Ligands.

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Cleavage of Silicon- and Germanium-Cobalt Bonds :
Change of Stereochemistry with Different Ligands
By Genevieve Cerveau. Ernest0 Colomer, and
Robert J. P. Corriu"]
The stereochemical course of nucleophilic cleavage of
Fe-Si and Co-Si bonds"] is in good accord with the general rules for nucleophilic displacement at silicon['! (71'C,H,)(CO)LFe, a good nucleophile, is however a weakly
polarizable leaving group (retention of configuration upon
substitution) and (CO),Co, a poor nucleophile, a highly
polarizable leaving group (inversion of configuration upon
sub~titution)'~~.
L = CO, P P h 3 , P(OEt)3; N p = 1 - N a p h t h y l
In order to better understand the nature of Co-Si- and
Co-Ge bonds, we have studied changes in the stereochemistry of the nucleophilic cleavage at silicon or germanium as a function of the electronic nature of the transition metal.
Thus, the cobalt complexes (3a)-(3f) and (4) (Table 1)
were synthesized, under NZ,from the dicobalt complexes
(I) (L=CO, P(OPh),, PPh3) and the substituted silanes [Za)
and germanes [2b), respectively (R' = Me, R2= Ph, R3= 1naphthyl [eq. (a) and (b)][,l.
[(CO)3LCo]2 + 2R'RZR3MH
(1)
-
2 (C0)3LCoMR'RZR3+ Hz (a)
(,?a), M = Si
(Zh), M = Ge
[
(3)
P"
(3d) + n B u L i + nBuC(CO)3CoGeR1RZR3] Li@
EtsOBF4
OE t
I
nBuC(CO)3CoGeR1R2R3 (4)
The stereochemical course of cleavage reactions with
LiAIH,"" are quite similar for silyl- and germyl-cobalt
complexes and vary, depending on the ligands at cobalt,
from a high degree of inversion of configuration with [3a)
and (3b) or (3d) and (.?el respectively, to poor retention
with (4) (Table 1).
The absolute configurations of the ~ilanes'~"'
and the germanes'"', as well as that of the two tetracarbonyl complexes (3a)and (3d)Isd,were determined by X-ray structure
analysis: this enabled the stereochemistry and stereoselectivity o f the LiAlH,-cIeavage reactions to be determined
unequivocally16].The exchange of one CO-ligand, a good
x-acceptor, in the (CO),Co-residue by a good donor increases the electron density at
and hence reduces
the nucleofugicity of the substituents. The nucleophilic
cleavage of the complexes (CO)3LCoMR'R'R3 occurs
with considerable inversion when L=CO; the degree of
inversion decreases in the compounds with L = P(0Phh
and PPh3. The reaction of the carbene complex (4).
L= C(OEt)nBu, proceeds with slight retention of configuration. The o-donor character of the ligands increases
along the series (CO<P(OPH),<PPh,<(COEt)nBu). This
result is in accord with the leaving group rules found in silicon chemistry[3h1.
That this is only a crude analysis o f the results-based
on the assumption that the metal-silicon and halogen-silicon bonds are similar-is shown by the nucleophilic cleavage of (CO),(NO)WGeR'R'R3181. In this case, a high degree of inversion of the configuration is anticipated, since
the tungsten center is surrounded by five good n-acceptor
ligands (NO is a better n-acceptor than CO'91);however, a
67% retention of configuration is observed.
This inference shows that the situation is certainly more
complex than can be achieved vin a simple comparison of
the properties of the % - ( o r Ge)-X- and Si--(or Ge-)Co
bonds. Indeed, the Ge-Co- and Ge-W-bonds are hardly
Table 1. Some physical data and results of the stereochemical course of the reductive cleavage of complexes (3u)-(3fl and (4). All novel compounds gave correct
elemental analyses.
Complex
L
(30)
co
(36)
(34
(34
(3~)
(3fi
P(OPh),
PPh,
(4)
M
co
P(OPh),
PPh3
-
M.p. ["Cj [a]
Si
Si
Si
Ge
Ge
Ge
93 (100)
124-125 (86) [fl
186 (161) [fl
92.5-93 (96.5-97.5)
123-124 (74-76) [fl
198-199 (210-211.5)
-
oil
IR vCo [cm-'I
( C H W [bI
'H-NMR &,
(in C6D6/TMS)
[alg
(CbHb)
Stereo[c]
chemistry [%I
[ a j g of R'R2R3MH
IW
1.33
1.33
1.53
1.46
1.46
1.73
1.20 [g]
+ Z 0 [C]
-6.38"
-6.48"
+2.7" [el
-3.47'
-5.4"
91 1
91 I
68 I
- 28.3"
- 28.3"
87 I
87 I
60 1
55 R
- 19S0
- 19.5"
2050 w, 1965 vs
2030 w, 1945 vs
[Ib]
[fl
2060 w, 1965 vs
2040 w, 1945 vs
2040 w, 1947 vs
-
(Pentane) [dl
- 13.1"
'-
+
5.3"
2.5"
[aJ The melting points of the racemates are shown in brackets. [b] The complexes occur, as inferred from the IR spectra, as trans-isomers. An X-ray structure analysis was performed on the carbene complex (4) [4b]. [c] I=inversion, R=retention. [dl Maximum values of rotation: R'R'R'SiH [a]g*36 and R'R'R'GeH
[a]::+26.7. [el In pentane. [fl Decomposition. [g] In CDCI,.
['I Prof. Dr. R. J. P. Corriu, Dr. G. Cerveau, Dr. E. Colomer
Laboratoire de Chimie des Organometalliques
Equipe de Recherche associee au C.N.R.S. No. 554
Universite des Sciences et Techniques du Languedoc
Place Eugene Bataillon, F-34060 Montpellier-Cedex (France)
478
0 Verlug Chemie GmbH. 6940 Weinheim. 1981
4 79/480 Advertisement
comparable, since Co belongs to the first and W to the
third third transition metal series.
Received: September 11, 1980 [Z 757b IE]
German version: Angew. Chem. 93, 489 (1981)
0570-0833/81/0505-478 $ 02.50/0
Angew. Chem. Inr. Ed. Engl. 20 (1981) No. 5
[ I ] a) G. Cerveau. E. Colomer, R. J . P. Corriu. W. E. Douglas, J. Chem. SOC.
Chem. Commun. 1975,410: J. Organomet. Chem. 135, 373 (1977); b) E.
Colomer. R. J. P. Corriu. J. Chem. SOC.Chem. Commun. 1976, 176: J. Organomet. Chem. 133, 159 (1977).
121 R. J . P. Corriu. J. Organomet. Chem. Libr. 9, 357 (1980). R. J . P. Corrru.
C. Guerin. J. Organomet. Chem. 198, 231 (1980).
[3] a) R. B. King. Acc. Chem. Res. 3, 417 (1970); b) L . H. Sommer. C. L.
Frye, M . C . Musolf: G. A. Parker, P. G . Rodewald. K . W. Michael. Y.
Okqva. R. Pepmsky. J. Am. Chem. SOC.83, 2210 (1961).
[4] The complexes (3) and (4) were prepared as described for the silyl or germany1 complexes with R ’ = R’= R’= Ph: a) G. Cerveau, E. Colomer. R . J .
P. Corriu, J . C. Young, J. Organomet. Chem. 205, 31 (1981); b) F. Carrh.
G. Cerueau. E. Colomer. R . J . P. Corriu. J . C . Young, L. Ricard. R. Weiss.
ibid. 179, 2 15 ( 1979).
IS] a) Y. Okuya. T. Ashida. Acta Crystallogr. 20,461 (1966): b) A. G. Brook. J.
Am. Chem. SOC. 85, 3051 (1963); A. G. Brock. G.J. D. Peddle, ibid. 85,
1869 (1963); c) M. Manassero. personal communicatlon: F. Dahan. Y.
Jeannin. J. Organomet. Chem. 136, 251 (1977).
[6] L. H. Sommer. J . D . Citron. G. A. Parker. J. Am. Chem. SOC. 91, 4729
(1969).
171 M . D. Curtis, Inorg. Chem. 11, 802 (1972).
[8] (CO)4(NO)WGeR’R’R’ was prepared from [(CO)5WGeR1R’R’]NEta (E.
Colomer. R. J P. Corriu. J. Chem. SOC.Chem. Commun. 1978, 435) by
treatment with NOBF,: E. E. Isaucs. W. A. G. Gruhum, J. Organomet.
Chem. 99, 119 (1975).
(91 7 A . Manuel. Adv. Organomet. Chem. 3, 191 (1965) and references therein.
“Isolated” Olefinic Double Bonds
as 2~-Componentsin I8 21-Cycloadditions
By Martin Riediker and Walter Graf [‘I
In the classical Diels-Alder reaction (D.-A. reaction with
normal electron demand) non-activated isolated double
bonds scarcely react with dienes. On the other hand,
charged heterodienes such as ( I ) display excellent reactivity towards isolated olefinic double bonds even at room
temperature“”’ (D.-A. reactions with inuerse electron demand) [cf. (I)+ (ZJ.
BO’
R3 = Me3
R~ = MeztBu
CF3S0P
R 3 s i o /m
0
i 71
( 5 ) . R2 = H
In the reaction of 2-oxiranylpyridine N-oxide (5) with
CF3S03SiR3(R3= Me, o r Me2tBu), only (7). the product of
a 1,2 H-shift in (6), could be isolated (cf. L3J; see Table 1).
Table I . Some physical data of the products. ‘H-NMR in CDCI’, except in
the case of (7), R = M e (CDzCIz)and (lO)(D,O); &values, J in Hz; MS: m/z.
(‘71. R = Me, ’H-NMR: 0.18 (s, 9 H),3.68 (d x d , I = 18, Y = I, 1 H), 4.22 (d x d,
J = 18, J‘= 5 , 1 H), 6.52 (d x d, J = 5, J’= I , 1 H), 7.85-8.50 (m. 3 H), 8.85 (m,
1 H)
(10). ‘H-NMR: 3.08 (s, 6H), 3.36 (s, 6H), 6.31 (d, JAH=13, 2H). 6.66 (d,
J,\H=
13, 2 H), 8.41 (s,4H). On warming, a rapid change of conformation of
the eight-membered ring occurs; thereby, the AB system of the methylene
groups simplifies to a singlet.
( 1 3 ~ )R. = H , ‘H-NMR: 1.00-2.50 (m. 9H), 4.50 (d, J = 3 , I H), 4.94 (m,
wy2=9, IH),7.00-8.20(m,8H),8.73(dxd, J = 6 , J ’ = l , 1H)
+
(1)
/
(2)
(136). R = H , ‘H-NMR: 1.43 (t. J = 7 , 3H). 1.25-2.50 (m, 9H), 2.99 ( d x d ,
JAH=IS, 3-1.6, 1 H),3.60(dxd, JAH=18, J = 7 , 1 H),4.20(q, J=7,2H),4.90
(m, wy2= 7 , I H), 7.74 (singletoid m, 2 H), 8.90 (singletoid m, I H)
( 1 5 ~ ) .R = H , ‘H-NMR, E/Z-mixture: 1.20-1.80 (m,4H), 1.90-2.45 (m,
4H), 6.75-7.80 (m, 8H), 8.57 (m, 1 H), 9.69 (m, 1 H). Additionally for 2c6.12
(1. J=7, ca. 0.5 H), for E:6.88 (t, J = 7 , ca. 0.5 H); MS: 265 ( M + ,29%). 208
( 100)
( 1 5 ~ ) .R=Me, ‘H-NMR, E/Z-mixture: 1.20-1.90 (m, 4H), 2.08 (s, 3 H),
1.90-2.45 (m, 4H). 6.95-8.00 (m. 8H), 8.58 (m, I H). Additionally, for Ze
6.10 (1, J = 7 , 0.6H). for Ec6.84 (1. J=7.5, 0.4H); MS: 279 ( M + ,41%). 208
(100)
(Isib).R = H , ‘H-NMR, E/Z-mixture(1 : I ) : 1.20-11.80(m,4H), l.40(t, J = 8 ,
3H). 2.00-2.80 (m,4H), 4.05 (9. J = 8 , 2H), 7.10(m, 2H), 8.241111, I H), 9.72
(m, I H). Additionally, for Ec 6.38 (d, J = 14, I H), 6.60 (d x t, J = 14, J’=5,
1 H), for 2 , 5 6 4 (d x t, J = 12, Y = 7 , I H), 6.38 (d, J = 12, I H); MS: 233 ( M + ,
28%). 176 (100)
(16al. R=Me, ‘H-NMR: 1.40-2.20 (m. 8H). superposed by 1.63 (s, 3H),
5.98(s,1H),6.90-7.50(m,8H),8.23(dxd,J=3,5’=4,1H);MS:279(M’,
(3)
(4)
71%). 168 (100)
(17). ‘H-NMR: 1.39 (1. J = 7 , 3H). 3.74 (s. 6H), 3.99 (9, J = 7 , 2H), 4.14 (s,
2H). 6.78 (singletoid m, SH), 7.99 (singletoid m, I H); MS: 289 ( M + , 24%).
272 (100)
(18). ‘H-NMR: 1.20-2.50 (m, 8H), superposed by 1.43 (t, J = 7 , 3 H), 4.08 (4,
5 = 7 , 2 H ) , 4 . 3 3 ( b r . s , 2 H ) , 5 . 7 5 ( b r . t , J=7,IH),?.lO(singletoidm.2H),8.20
(m. I H), 9.70 (m, I H)
=i4,
(a), X = C ,
R=H
(6). X=N‘, Y = C H , R = H or Alkyl
(c), X = N e . Y = C H , R = C H 2 0 S i R I
1,2-Oxazinium salts (2b)12“1
enabled, inter a h , the cycloreversion (3)- (4), initiated by proton abstraction (2)- (3). to
be carried out[2h’.
We demonstrate here that the [8 21-cycloaddition-cycloreversion sequence [cf. (IZ)+ (13)- (Is)]with heterocyclic N-oxides is a useful, and, in our opinion, potentially
versatile synthetic reaction.
+
The (ch1oromethyl)pyridine N-oxide derivative (a),
which cannot undergo such an H-shift, reacts with AgBF,
to give the intermediary reactive product (9). which dirnerizes to a salt of the dication (10) (see Table I).
The hypothetical intermediates (6) and (9) d o not react
with cyclohexene. However, the iifetime of the reactive in-
[*I Dr. W. Graf [**I, DipLChem. M. Riediker
[**I
Laboratorium fur Organische Chemie
der Eidgen6ssischen Technischen Hochschule
CH-8092 Zurich (Switzerland)
Present address:
Fluka AG
CH-9470 Buchs/SG (Switzerland)
Angen,. Chem. Int. Ed. Engl. 20 (1981) No. 5
0 Verlag Chemie GmbH. 6940 Weinheim, 1981
0570-0833/81/0505-481$ 02.50/0
48 1
4 79/480 Advertisement
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bond, cleavage, change, silicon, germanium, different, cobalt, ligand, stereochemistry
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