Reaction between [Ir(coe)_2Cl]_2(coe = cyclooctene) and AgO_2CCF_3(4 equiv.) produces a highly active system for metathesis/isomerization of acyclic olefins, including methyl oleate

Feldman, Jerald

France, Marcia B.

Grubbs, Robert H.

Caltech Authors - Main

J. CHEM. SOC., CHEM. COMMUN., 1994 1307 
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An Iridium-based Catalyst System for Metathesis/lsomerization of Acyclic Olefins, 
including Methyl Oleate 
Marcia B. France,a Jerald Feldman*band Robert H. Grubbs*a 
a The Arnold and Mabel Beckman Laboratory of Chemical Synthesis, Division of Chemistry and Chemical 
Engineering, California Institute of Technology, Pasadena, California 91 125, USAt 
b Central Research and Development, E. 1. du Pont de Nemours & Company Inc., Wilmington, Delaware, 19880- 
0328, USAS 
Reaction between [ l r ( c ~ e ) ~ C I ] ~  (coe = cyclooctene) and Ag02CCF3 (4 equiv.) produces a highly active system for 
metathesis/isomerization of acyclic olefins, including methyl oleate. 
(a 1 
'bc, 
Olefin metathesis catalysts based on group 8-10 metals display 
tremendous tolerance of functional groups as compared to 
catalysts based on early metals: ruthenium, osmium and 
iridium catalysts are known that can metathesize olefins in the 
presence of esters, alcohols, ketones and even Bronsted 
acids.' However, the activity of these catalysts is almost 
invariably limited to ring-opening metathesis polymerization 
I I - .  I 
15 20 25 l o  t /min 5 
Fig. 1 Gas chromatogram of the product mixture formed in Scheme 1; 
for clarity, only the peaks corresponding to C4, C18 and C31 olefins are 
labelled. Clx  olefins account for cu. 10% of the olefins present 
i 
Octadec-1-ene + C4, C5, C6. . . . C3, olefins 
Scheme 1 Reugents and conditions: i ,  [ I r ( ~ o e ) ~ C l ] ~  (4 mol%), 
Ag02CCF3 (16 mol%), toluene, 25 "C, 9 h 
c I 
(ROMP) of strained bicyclic olefins such as norbornene and its 
derivatives. A rare exception was reported by Porri and 
coworkers in 1974: an ill-defined system comprising 
[Ir(coe)2C1]2-Ag02CCF3 (2 equiv.)-HO*CCF3 (14 equiv.) 
was found to catalyse ROMP of relatively unstrained cycloole- 
fins such as cyclopentene and ~0e.2.3 This same system was 
also found to simultaneously metathesize and isomerize an 
acyclic olefin, pent-1-ene, to give C4, C5, C6 and higher 
olefins.3 The role of the acid and silver salt was unclear,4 and 
acyclic functionalized olefins were not studied. We are 
interested in developing late metal catalysts for acyclic 
functionalized olefin metathesis,s and have been reinvestigat- 
ing the Porri catalyst system. 
We have found that a highly active catalyst for acyclic olefin 
metathesis/isomerizations can be prepared in situ from the two 
component system [ 1r(~oe)2Cl]~-AgO~CCF~; addition of acid 
is not necessary. The molar ratio of Ag02CCF3: [Ir(coe)2Cl]2 
must be 24: 1; a lower ratio (e .g .  2 :  1) results in extensive 
olefin isomerization, but no metathesis activity is observed. 
Analysis by XRD of the insoluble product formed in the 
reaction between [ Ir(coe)2C1]2 and Ag02CCF3 (4 equiv.) in 
toluene after several hours at 25 "C shows it to be a mixture of 
AgCl and metallic Ag in roughly equal amounts. Thus, the 
silver salt serves (i)  to precipitate silver chloride and (ii) to 
oxidize7,s the resulting Irl trifluoroacetate complex. An active 
i i  C9-C26alkanes 
Me(CH2)7CH=CH(CH2)7C02Me k C8-C28 saturated esters 
C, 1-C26 saturated diesters 
Scheme 2 Reagents and conditions; i ,  [ I r ( ~ o e ) ~ C l ] ~  (4 mol%), 
Ag02CCF3 (20 mol%), toluene, 85 "C, 22 h; ii, H2 (100 psi), 0.5% Pd/ 
C, methanol, 85 "C, 18 h 
:b ) 401 ( d  1 
; i 3 L  20 , , , , .  - 
(e ) 10 
0 
20.60 20.80 21.00 21.20 21.40 
t / min 
O J . . , ' . . . f . . . . I . . ' . I . . . . I . . . . I . . . ' I . . . . ~ ' . . . I . . '  
5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00 
t 1 min 
Fig. 2 Gas chromatogram of the product mixture formed in Scheme 2. Peaks corresponding to cyclooctane ( a )  (derived from hydrogenation of the 
coe ligand) and methyl octadecanoate (b) (derived from hydrogenation of methyl oleate and its double bond isomers) are off scale. Methyl 
octadecanoate accounts for ca. 50% of the material present; C9-C26 alkanes elute between 3 and 35 min; C8-C28 saturated methyl esters elute 
between 4 and 45 min; Cll-C26 saturated dimethyl esters elute between 14 and 46 min. Inset: expanded plot of the group of peaks with t R  c- 21 
min: octadecane. Cl8. (c), methyl pentadecanoate, C16, (d) and dimethyl dodecandioate, C14 ( e ) .  
1308 J. CHEM. SOC., CHEM. COMMUN., 1994 
catalyst can also be obtained by addition of Ag02CCF3 (2 
equiv.) to isolated [ I ~ ( c o ~ ) ~ ( O ~ C C F ~ ) ] ~ ~  in the presence of an 
acyclic olefin. When [ I ~ ( C O ~ ) ~ ( O ~ C C F ~ ) ] ~  is added to an 
acyclic olefin in the absence of an excess of Ag02CCF3 a violet 
solution is formed; the olefin is rapidly isomerized9 but no 
cross-metathesis of the resulting internal olefins is observed. 
Action of the [Ir(~oe)2C1]~-4 Ag02CCF3 catalyst system on 
an acyclic olefin is illustrated by the gas chromatogram shown 
in Fig. 1. Addition of [ I r ( c ~ e ) ~ C l ] ~  to a toluene solution of 
Ag02CCF3 (4 equiv.) and octadec-l-ene (25 equiv.) results in 
a bright orange solution plus a white precipitate (AgCI). When 
the reaction mixture is allowed to stir for several hours at 
25 "C, metallic silver slowly precipitates and metathesis/ 
isomerization of the starting CIH olefin is observed (Scheme 1). 
As shown in Fig. 1, new olefins containing 4 to at least 
31 carbon atoms can be observed by GC of the reaction 
mixture.1 The same result is obtained when [Ir(coe),- 
(02CCF3)]2 is added to a solution of Ag02CCF3 (2 equiv.) 
and octadec-l-ene (25 equiv.). Metathesis/isomerization of an 
acyclic functionalized olefin such as methyl oleate can also be 
effected by [Ir(coe)2Cl]z4 Ag02CCF3. In this case the 
product mixture is complex, consisting of a mixture of 
isomeric olefins, unsaturated esters and unsaturated diesters 
over a wide molecular mass range. Hydrogenation to give 
alkanes and saturated esters and diesters greatly simplifies 
analysis of the product mixture (Scheme 2), and a gas 
chromatogram of a hydrogenated mixture is shown in Fig. 2.1 
Analysis of this mixture by GCMS indicates the presence of 
three molecular mass distributions: C9 to C26 linear alkanes, 
C8 to C28 linear saturated methyl esters, and C1 to C26 linear 
saturated dimethyl esters. Each of the peaks in the gas 
chromatogram actually consists of two or three closely spaced 
peaks corresponding to an alkane, an ester, and a diester of 
nearly identical molecular mass; e.g. the peak with retention 
time ( f R )  ca. 21 min is composed of octadecane, methyl 
pentadecanoate, and dimethyl dodecandioate [Fig. 2 (inset)]. 
We have discovered that by allowing [Ir(coe)2C1]2 and an 
excess of Ag02CCF3 to react for several hours at room 
temperature prior to addition of the acyclic olefin, the reaction 
can become selective for metathesis, instead of metathesis/ 
isomerization (Scheme 3). When the olefin is methyl oleate, 
the major products are octadec-9-ene and 
toluene methyl oleate (10equiv.) 
[ I r ( ~ o e ) ~ C l ] ~  + 6 Ag02CCF3 A > 
25 "C, 22 h 25 "C, 8 h 
Me(CH2),CH=CH(CH2)7Me + M C O ~ C ( C H ~ ) , C H = C H ( C H ~ ) ~ C O ~ M ~  
Scheme 3 
Toluene 
Octadec-9-ene 
\ 
Methyl oleate 
Me02C(CH2)7CH=CH(CH2)7C02Me 
J 
1 - - . , . . . 1  
0 2 4 6 8 10 12 14 16 
t I min 
Fig. 3 Gas chromatogram of the product mixture formed in Scheme 3; 
unlabellcd peaks correspond to olefins formed by isomerization/cross- 
methathesis of the reaction mixture 
Me02C(CH2)7CH=CH(CH2)7C02Me; i.e. the products of 
selective methyl oleate metathesis. However, small amounts 
of products derived from metathesishsomerization are still 
observed as shown in Fig. 3. 
The iridium catalyst described above is an extremely rare 
example of a late metal system for acyclic olefin metathesis; 
our observation of acyclic functionalized olefin metathesis by 
this system is almost without precedent for a metal from 
groups 8-10.9 Although in the case of methyl oleate metathe- 
sis conversions and selectivities are low, it should be 
emphasized that this is a 'black box' catalyst: the amount of 
iridium present as active catalyst may in fact be quite small. 
The development of highly active iridium catalysts for acyclic 
functionalized olefin metathesis will probably depend on the 
discovery of routes to iridium carbene complexes in the right 
oxidation state (we believe IrI*I) and with suitable ligands (e.g. 
labile triflouroacetates). This approach has recently met with 
success in the case of ruthenium catalysts.9~ 
J. F. thanks Alicia Glatfelter and Beth Fenner for skilled 
technical assistance. M. B. F. thanks the National Science 
Foundation for a predoctoral fellowship. R. H. G. thanks the 
National Science Foundation for support. 
Received, 7th February 1994; Corn. 4100747F 
Footnotes 
-1- Contribution no. 8937. 
$ Contribution no. 6798. 
Ei E.g. pcnt-l-ene in toluene is isomerized to >95% pent-2-ene by 
[I~(co~) , (O~CCF,)]~ (0.5 mol%) within 30 min at 25 "C. 
7 GC analyses were made using a crosslinked methyl silicone capillary 
column (25 m X 0.32 mm X 0.52 pm film thickness) and a flame 
ionization detector. 
References 
1 K. J .  Ivin. Olejin Metathesis. Academic, New York, 1983, ch. 2.6. 
2 L. Porri. R. Rossi, P. Diversi and A. Lucherini. Makrom. Chem., 
1974, 175, 3097. 
3 L. Porri, P. Diversi. A. Lucherini and R. Rossi, Makvom. Chem., 
1975, 176, 3121. 
4 F. Bianchi, M. C. Gallazzi, L. Porri and P. Diversi, J .  Organomet. 
Chem., 1980, 202.99. 
5 For recent examples of Mo, W and Re based catalysts for acyclic 
functionalized olefin metathesis see R. Toreki, G. A. Vaughan, 
R. R. Schrock and W. E. Davis, J .  Am. Chem. SOC., 1993,115,127 
and refercnccs therein. 
6 Catalysts that can simultaneously isomerize and metathesize olefins 
arc potentially useful: these reactions carried out sequentially are 
the basis for the Shell Higher Olefins Process (SHOP); see G. W. 
Parshall and S. D. lttcl Homogeneous Catalysis, 2nd edn.. Wiley, 
New York, 1992, ch. 4.3. 
7 By 1H NMR, the oxidized product appears to be a complex mixture 
of diamagnetic iridium complexes. The oxidation state of the 
catalyst is probably IrIII,  although IrII cannot be ruled out; 
oxidation of IrI to Ir"1 by silver triflouroacetate is known: F. A. 
Cotton and R. Poli, lnorg. Chem., 1987. 26, 590. 
8 The oxidation reaction requires several hours at room temp. and 
likely proceeds via intermediate Iri-  AgI complexes; recently, we 
structurally characterized an Irl.AgI complex formed in the reaction 
between [Ir(cod)(O2CCF,)], and Ag02CCF3 (2 equiv.); J .  Feld- 
man and J .  C. Calabrese, manuscript in preparation. 
9 Rare exceptions: ( a )  S.  T. Nguyen and R. H .  Grubbs, J .  Am. Chem. 
SOC., 1993, 115, 9858; ( b )  B .  Marciniec and C. Pietraszuk, 
J .  Organomet. Chem., 1993,447, 163; ( c )  D. J. Cardin, M. J.  Doyle 
and M .  F. Lappert. J .  Chem. SOC. ,  Chem. Commun.. 1972,927. 


An Iridium-based Catalyst System for Metathesis/lsomerization of Acyclic Olefins, including Methyl Oleate

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An Iridium-based Catalyst System for Metathesis/lsomerization of Acyclic Olefins, including Methyl Oleate

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