Ruthenium catalysts for metathesis reactions of olefins

Details Ruthenium catalysts for metathesis reactions of olefins Ruthenium catalysts for metathesis reactions of olefins

2000-01-27

2002-01-29

Nazario-Gonzalez, Porfirio (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Heavy metal containing

C556S018000, C556S022000, C556S136000, C556S137000, C549S206000, C546S002000, C526S160000, C526S161000, C526S169100, C526S281000, C526S282000, C526S283000, C502S155000, C502S162000

Reexamination Certificate

active

06342621

ABSTRACT:

The present invention relates to highly active catalysts for olefin metathesis reactions, and the preparation of the catalysts. The invention also relates to the olefin metathesis reactions catalyzed with the catalysts of the invention.
BACKGROUND
The past several years have witnessed a healthy surge in catalyst development related to metathesis reactions of olefins, in particular metathesis polymerization of olefins. These well defined catalysts usually possess a metal-carbon double bond (metal-carbene or alkylidene) that can coordinate to the alkene moiety of the olefin, and in particular, can perform the ring opening of cyclo-olefin monomers in a rather facile manner. Most of the metals that exhibit remarkable activity for this phenomenon are second-or third-row mid-to late- transition metals. Although the specific reason for this observation has not been clearly articulated, many theories have been proposed, the most prevalent of which is that late transition metals exhibit greater robustness towards the impurities that may inherently be present within a reaction system and, consequently, catalysts containing those metals resist degradation.
Among olefins, cyclo-olefin monomers like norbornene (NB) or dicyclopendadiene (DCPD) which possess a strained double bond can readily undergo ring opening metathesis polymerization (ROMP) because the ring opened product is thermodynamically favored. For ring opening to occur in these cyclo-olefins there is no pre-requisite for the catalyst to possess a metal-carbene moiety in its framework, because any organometallic complex that has the capability of initiating a metal-carbene formation in situ can also perform as a catalyst. For instance, it is well known that RuCl
3
.3H
2
O can accomplish the ROMP of NB quite effortlessly, even though there is no carbene present in the catalyst. It is hypothesized that the first step of the reaction, when the metal halide reacts with the monomer, is the formation of a metal carbene moiety that is responsible for further polymer propagation.
The catalysts that have received the greatest exposure in the literature by far are those designed by Schrock et al., as reported in Schrock et al.,
J. Am. Chem. Soc.,
1990, 112, 3875, and by Grubbs's group, as reported in Fu et al.,
J. Am. Chem. Soc.,
1993, 115, 9856; Nguyen et al.,
J. Am. Chem. Soc.,
1992, 114, 3974; and Grubbs et al., WO98/21214 (1998). The Grubbs catalyst (a ruthenium carbene) is slightly more versatile than the Schrock catalyst (a molybdenum alkylidene) because of its ease of synthesis as well as its utility from a commercial viewpoint. Cox and co-workers reported in Cox et al.,
Inorg. Chem.,
1990, 29, 1360; Cox, et al.,
J. Chem. Soc., Chem. Commun.,
1988, 951-953; and Porri et al,
Tetrahedron Letters,
No. 47., 1965, 4187-4189, the synthesis of a class of metal catalysts based on ruthenium metal. These catalysts consist primarily of a bis-allyl ligand wrapping the metal, along with two or three acetonitrile ligands. Additionally, these catalysts possess a mono- or di-anion that is virtually (i.e., almost) coordinated to the metal center, which is therefore considered to be formally in the +4 oxidation state. These complexes in conjunction with diazo ethyl acetate have been used by Herrmann's group, as reported in Herrmann et al.,
Angew. Chem. Int'l. Ed. Engl.,
1996, 35, 1087, to investigate the polymerization (specifically the ROMP) of NB. Herrmann has conjectured that the active species in the catalyst system is a metal carbene generated in situ when the ruthenium reacts with the diazo alkyl compound (such as diazo ethyl acetate).
A disadvantage of the above catalysts is that for the ROMP of cyclic olefins these catalysts must be used with a co-catalyst such as a diazo alkyl compound, which requires special caution in handling because of the instability of the diazo group.
SUMMARY OF THE INVENTION
One aspect of the invention is to provide catalysts which are highly active in initiating metathesis reactions in olefins.
Another aspect of the invention is to provide catalysts which are highly active in the ring-opening polymerization (ROMP) of cyclo-olefin monomers without requiring the presence of a co-catalyst such as a diazo alkyl compound.
Another aspect of the invention is to provide methods for the preparation in good yield of the catalysts for metathesis reactions in olefins.
Yet another aspect of the invention is to provide a highly effective method for polymerizing olefins, in particular cyclo-olefins, using the catalysts of the invention.
DESCRIPTION OF THE INVENTION
The catalysts of the invention are characterized by a complex cation represented by the formula I*, II* or III* below, wherein the ruthenium atom is in the 4+ oxidation state, has an electron count of 14, and is penta-coordinated.
wherein
each of X
1
and X
2
, which may be the same or different, is a C
3
-C
20
hydrocarbon group having an allyl moiety as an end group bonded to the ruthenium atom, optionally substituted with a C
1
-C
20
alkyl, a C
1
-C
20
alkoxy, or a C
6
-C
12
aryl group on its backbone, said allyl moiety optionally having up to three functional groups independently selected from the group consisting of hydroxyl, thiol, thioether, ketone, aldehyde, ester, ether, amine, imine, amide, nitro, carboxylic acid, disulfide, carbonate, isocyanate, carbodiimide, carboalkoxy, carbamate, and halogen; or
X
1
and X
2
together form a group which results from dimerization of an alkene and has at each end an allyl group bonded to the ruthenium atom, said group resulting from the alkene dimerization being optionally substituted on its backbone with a C
1
-C
20
alkyl, a C
1
-C
20
alkoxy, or a C
6
-C
12
aryl group, and further optionally having a functional group selected from the group consisting of hydroxyl, thiol, thioether, ketone, aldehyde, ester, ether, amine, imine, amide, nitro, carboxylic acid, disulfide, carbonate, isocyanate, carbodiimide, carboalkoxy, carbamate, and halogen;
L
1
and L
2
, which may be the same or different, are monodentate neutral electron donor ligands;
L
3
is a solvent molecule coordinated to the central ruthenium atom or a neutral monodentate electron donor ligand;
L{circumflex over ( )}L is a bidentate neutral electron donor ligand; and
L{circumflex over ( )}L{circumflex over ( )}L is a neutral tridentate electron donor ligand.
More specifically, the catalysts of the invention are cationic complexes represented by the formula I, II or III below, wherein the ruthenium complex cation is paired with a counter anion A.
wherein X
1
, X
2
, L
1
, L
2
, L
3
, L{circumflex over ( )}L and L{circumflex over ( )}L{circumflex over ( )}L are as described above, and A is a counter anion which is weakly coordinated to the central ruthenium atom in the complex cation.
The neutral electron donor ligand as recited in the definition of L
1
, L
2
, L
3
, L{circumflex over ( )}L and L{circumflex over ( )}L{circumflex over ( )}L in the complex cations of the invention is any ligand which, when removed from the central ruthenium atom in its closed shell configuration, has a neutral charge, i.e., is a Lewis base. Preferably, at least one of the monodentate neutral electron donor ligands in the complex cation is a sterically encumbered ligand. Examples of sterically encumbered monodentate ligands are phosphines, sulfonated phosphines, phosphites, phosphinites, phosphonites, arsines, stibines, ethers, amines, amides, imines, sulfoxides, carboxyls, nitrosyls, pyridines, and thioethers.
In a preferred embodiment, each of X
1
and X
2
, which may be the same or different, is a C
3
-C
20
hydrocarbon chain with an allyl moiety as an end group bonded to the ruthenium atom. The hydrocarbon chain may be substituted on its backbone with up to three substituents independently selected from C
1
-C
20
alkyl, C
1
-C
20
alkoxy, and C
6
-C
12
aryl groups. The allyl moiety may further have up to three functional groups independently selected from: hydroxyl, thiol, thioether, ketone, aldehyde, ester, ether, amine, imine, amid

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