The initial product of the metathesis of deca-2,8-diene with metathesis catalysts formed from either Me_4Sn–WCl_6 or Me_3Al_2Cl_3–(Ph_3P)_2(NO)_2Cl_2Mo is propene; labelling of the terminal groups of the diene and the alkylating agents gives a labelling pattern in the propene that is best explained in terms of generation of a carbene in the initiation step from the alkylating agent

Grubbs, Robert H.

Hoppin, Charles R.

English

Caltech Authors - Main

634 J.C.S. CHEM. COMM., 1977 
Initiation of Olefin Metathesis: Reaction of Deca-2,8-diene with Catalysts 
formed from Me4Sn-WC16 and Me3Al2Cl3-(Ph3P)2(N0)2Cl2Mo 
By RoBERT H. GRUBBS* and CHARLEs R. HoPPIN 
(Department of Chemistry, ~1\!Iichigan State University, East Lansing, Michigan 48824) 
Summary The initial product of the metathesis of deca-
2,8-diene with metathesis catalysts formed from either 
Me4Sn-WC16 or Me3Al2Cl3-(Ph3P)2 (N0)2Cl2Mo is propene; 
labelling of the terminal groups of the diene and the 
alkylating agents gives a labelling pattern in the propene 
that is best explained in terms of generation of a carbene 
in the initiation step from the alkylating agent. 
THE olefin metathesis reaction has provided one of the 
major mechanistic challenges in transition metal organic 
chemistry.l All the data to date are most consistent with 
a chain reaction involving odd carbon intermediates, with 
the reaction in Scheme 1 being the most reasonable propa-
gation step. 2 The major homogeneous catalyst systems are 
R 
LnM=CH2 + R-CH=CH2 • ,... LnM 6 • .,. L·nM=CHR+ CH2=CH2 
ScHEME 1 
prepared from a tungsten-, molybdenum-, or rhenium-
halide complex and an alkyl-aluminium or -tin co-catalyst. 
Although there are models for the initiation step (metal-
alkylidene complex formation) in such systems3 there is 
little evidence for the initiation mode4 in these catalysts. 
Different initiation modes have been proposed for other 
types of catalysts. 5 Schrock has shown that tantalum-
alkylidene complexes can be formed by the reaction of 
tantalum halides with alkyl lithium reagents (Scheme 2). aa 
ScHEME 2 
We now have good evidence that carbenoid species are 
formed in alkylaluminium-molybdenum complex6 and 
alkyltin-tungsten complex catalyst systems. 7 Mixing of 
the transition metal complex with the appropriate methyl-
tin or -aluminium cocatalyst results in the formation of 
methane and ethylene [equations (1) and (2)]. The 
products produced by using (CD3) 4Sn were perdeuteriated. 
PhCl 
Mo(Ph3P)2Cl2(N0)2 + Me3Al2Cl3 ~ CH4 
+ CH2=CH2 + Mo-catalyst (1) 
PhCl 
WC16 + Me4Sn~CH4 + CH2=CH2 + W-catalyst (2) 
When deca-2,8-diene (I) was mixed with the catalyst 
solution, the initial product was propene in both cases 
followed by the production of the usual products [equation 
(3) ]. 
(I) 
c~=cH-Me 
+ 
+Catalyst___. Me-CH=CH-Me 
+ 
Cyclohexene 
(3) 
When the reactions were repeated with [1,1,1,10,10,10-
2H6]deca-2,8-diene, the product was [3,3,3-2H 3]propene; 
reactions of (CD3) 4Sn-WC16 with (I) gave [1, l-2H 2]propene 
and of [2H 6]-(I) with (CD3) 4Sn-WC16 gave [1, l,3,3,3- 2H 5]-
propene as the initial product. 
These results, combined with the model studies, 3 provide 
a mechanism for initiation which is consistent with the 
labelling pattern (* and **) shown in Scheme 3. 
* I 
CH3-M ilf CHTM' * * 
LnM ~ LnM-CH3 ~LnM=CH2 + CH4 
*~ H3-CH-cH-[c><,].-CH=CH- CH3l 
• H H 
* ** X_·· LnM=CH-C 7H13 + CH:fCH-CH3 ~ LnMycH3 ! C7H13 
Normal metathesis 
SCHEME 3 
These experiments provide information concerning two 
other aspects of the reaction. The yield of propene based 
on the amount of transition metal indicates the percentage 
converted into the active catalyst in the initiation step. 
The molybdenum system is much more active for meta-
thesis than the WC16-SnMe4 system and produces a much 
higher yield of propene (ca. 90% compared to 8%). The 
production of ethylene, apparently by metal carbene 
J.C.S. CHEM. CoMM., 1977 
dimerization during the initiation, indicates one of the chain 
termination mechanisms; methylene-metal complexes have 
been found to dimerize3 according to equation (4). 
(4) 
635 
This labelling study provides considerable information 
concerning the initiation, activity, and termination of the 
methathesis reaction. 
(Received, 23rd June 1977; Com. 633.) 
1 N. Calderon, A. Ofstead, and W. A. Judy, Angew. Chem. Internat. Edn., 1976, 15, 401; R. H. Grubbs, 'New Applications of 
Organometal Reagents in Organic Synthesis,' ed. D. Seyferth, 1976, p. 423. 
2 R. H. Grubbs, D. D. Carr, C. Hoppin, and P. L. Burk,]. A mer. Chem. Soc., 1976, 98, 3478; T. J. Katz and J. McGinnis, ibid., 
1977, 99, 1903, and references therein; P. G. Gassman and T. H. Johnson, ibid., 1976, 98, 6055, 6057, 6058. 
3 (a) R. R. Schrock,]. Amer. Chem. Soc., 1975,97, 6577; (b) C. P. Casey, T. J. Burkhardt, C. A. Bunnell, and J. C. Calabase, ibid., 
1977, 99, 2127, and references therein. 
4 E. L. Muetterties, Inorg. Chem., 1975, 14, 951. 
5 M. F. Farona and W. S. Greenlee, J.C.S. Chem. Comm., 1975, 859; P. Krausz, F. Garnier, and J. E. Dubois,]. A mer. Chem. Soc., 
1975, 97, 437; R. Westnoff and J. A. Moulin,]. Catalysis, 1977,46, 414. 
6 E. A. Zeuch, Chem. Comm., 1968, ll82. 
7 P. B. Van Dam, M. C. Mittelmeijer, and C. Boelhouwer, J.C.S. Chem. Comm., 1972, 1221. 


Initiation of Olefin Metathesis: Reaction of Deca-2,8-diene with Catalysts formed from Me_4Sn-WC1_6 and Me_3Al_2Cl_3-(Ph_3P)_2(NO)_2Cl_2Mo

634 J.C.S. CHEM. COMM., 1977 
Initiation of Olefin Metathesis: Reaction of Deca-2,8-diene with Catalysts 
formed from Me4Sn-WC16 and Me3Al2Cl3-(Ph3P)2(N0)2Cl2Mo 
By RoBERT H. GRUBBS* and CHARLEs R. HoPPIN 
(Department of Chemistry, ~1\!Iichigan State University, East Lansing, Michigan 48824) 
Summary The initial product of the metathesis of deca-
2,8-diene with metathesis catalysts formed from either 
Me4Sn-WC16 or Me3Al2Cl3-(Ph3P)2 (N0)2Cl2Mo is propene; 
labelling of the terminal groups of the diene and the 
alkylating agents gives a labelling pattern in the propene 
that is best explained in terms of generation of a carbene 
in the initiation step from the alkylating agent. 
THE olefin metathesis reaction has provided one of the 
major mechanistic challenges in transition metal organic 
chemistry.l All the data to date are most consistent with 
a chain reaction involving odd carbon intermediates, with 
the reaction in Scheme 1 being the most reasonable propa-
gation step. 2 The major homogeneous catalyst systems are 
R 
LnM=CH2 + R-CH=CH2 • ,... LnM 6 • .,. L·nM=CHR+ CH2=CH2 
ScHEME 1 
prepared from a tungsten-, molybdenum-, or rhenium-
halide complex and an alkyl-aluminium or -tin co-catalyst. 
Although there are models for the initiation step (metal-
alkylidene complex formation) in such systems3 there is 
little evidence for the initiation mode4 in these catalysts. 
Different initiation modes have been proposed for other 
types of catalysts. 5 Schrock has shown that tantalum-
alkylidene complexes can be formed by the reaction of 
tantalum halides with alkyl lithium reagents (Scheme 2). aa 
ScHEME 2 
We now have good evidence that carbenoid species are 
formed in alkylaluminium-molybdenum complex6 and 
alkyltin-tungsten complex catalyst systems. 7 Mixing of 
the transition metal complex with the appropriate methyl-
tin or -aluminium cocatalyst results in the formation of 
methane and ethylene [equations (1) and (2)]. The 
products produced by using (CD3) 4Sn were perdeuteriated. 
PhCl 
Mo(Ph3P)2Cl2(N0)2 + Me3Al2Cl3 ~ CH4 
+ CH2=CH2 + Mo-catalyst (1) 
PhCl 
WC16 + Me4Sn~CH4 + CH2=CH2 + W-catalyst (2) 
When deca-2,8-diene (I) was mixed with the catalyst 
solution, the initial product was propene in both cases 
followed by the production of the usual products [equation 
(3) ]. 
(I) 
c~=cH-Me 
+ 
+Catalyst___. Me-CH=CH-Me 
+ 
Cyclohexene 
(3) 
When the reactions were repeated with [1,1,1,10,10,10-
2H6]deca-2,8-diene, the product was [3,3,3-2H 3]propene; 
reactions of (CD3) 4Sn-WC16 with (I) gave [1, l-2H 2]propene 
and of [2H 6]-(I) with (CD3) 4Sn-WC16 gave [1, l,3,3,3- 2H 5]-
propene as the initial product. 
These results, combined with the model studies, 3 provide 
a mechanism for initiation which is consistent with the 
labelling pattern (* and **) shown in Scheme 3. 
* I 
CH3-M ilf CHTM' * * LnM ~ LnM-CH3 ~LnM=CH2 + CH4 
*~ H3-CH-cH-[c><,].-CH=CH- CH3l 
• H H 
* ** X_·· LnM=CH-C 7H13 + CH:fCH-CH3 ~ LnMycH3 ! C7H13 
Normal metathesis 
SCHEME 3 
These experiments provide information concerning two 
other aspects of the reaction. The yield of propene based 
on the amount of transition metal indicates the percentage 
converted into the active catalyst in the initiation step. 
The molybdenum system is much more active for meta-
thesis than the WC16-SnMe4 system and produces a much 
higher yield of propene (ca. 90% compared to 8%). The 
production of ethylene, apparently by metal carbene 
J.C.S. CHEM. CoMM., 1977 
dimerization during the initiation, indicates one of the chain 
termination mechanisms; methylene-metal complexes have 
been found to dimerize3 according to equation (4). 
(4) 
635 
This labelling study provides considerable information 
concerning the initiation, activity, and termination of the 
methathesis reaction. 
(Received, 23rd June 1977; Com. 633.) 
1 N. Calderon, A. Ofstead, and W. A. Judy, Angew. Chem. Internat. Edn., 1976, 15, 401; R. H. Grubbs, 'New Applications of 
Organometal Reagents in Organic Synthesis,' ed. D. Seyferth, 1976, p. 423. 
2 R. H. Grubbs, D. D. Carr, C. Hoppin, and P. L. Burk,]. A mer. Chem. Soc., 1976, 98, 3478; T. J. Katz and J. McGinnis, ibid., 
1977, 99, 1903, and references therein; P. G. Gassman and T. H. Johnson, ibid., 1976, 98, 6055, 6057, 6058. 
3 (a) R. R. Schrock,]. Amer. Chem. Soc., 1975,97, 6577; (b) C. P. Casey, T. J. Burkhardt, C. A. Bunnell, and J. C. Calabase, ibid., 
1977, 99, 2127, and references therein. 
4 E. L. Muetterties, Inorg. Chem., 1975, 14, 951. 
5 M. F. Farona and W. S. Greenlee, J.C.S. Chem. Comm., 1975, 859; P. Krausz, F. Garnier, and J. E. Dubois,]. A mer. Chem. Soc., 
1975, 97, 437; R. Westnoff and J. A. Moulin,]. Catalysis, 1977,46, 414. 
6 E. A. Zeuch, Chem. Comm., 1968, ll82. 
7 P. B. Van Dam, M. C. Mittelmeijer, and C. Boelhouwer, J.C.S. Chem. Comm., 1972, 1221. 


http://authors.library.caltech.edu/32990/1/GRUjcscc77a.pdf

Initiation of Olefin Metathesis: Reaction of Deca-2,8-diene with Catalysts formed from Me_4Sn-WC1_6 and Me_3Al_2Cl_3-(Ph_3P)_2(NO)_2Cl_2Mo

Abstract

Similar works

Full text

Available Versions

Caltech Authors - Main

Caltech Authors - Main