Advanced Search
RSS LinkedIn Twitter

Journal Archive

Platinum Metals Rev., 2006, 50, (2), 81

doi:10.1595/147106706x112996

Ruthenium Allenylidene Complexes

A PROMISING ALTERNATIVE IN METATHESIS CATALYSIS

  • Ileana Dragutan
  • Valerian Dragutan
  • Institute of Organic Chemistry, Romanian Academy, 202B Spl. Independentei, PO Box 35-108, 060023 Bucharest, Romania
  • Email: vdraguta@cco.ro
SHARE THIS PAGE:

Article Synopsis

This paper presents a detailed account of an array of well-defined ruthenium allenylidene complexes as a promising class of metathesis pre-catalysts. This type of ruthenium complex is readily accessible from commercial reagents, induces good to excellent metathesis catalytic activity and selectivity, and shows a great tolerance towards many organic functional groups. By virtue of these beneficial features, ruthenium allenylidene complexes allow synthesis of a wide range of heterocyclic and carbocyclic compounds through ring-closing metathesis (RCM) and enyne metathesis as well as production of specialty polymers by acyclic diene metathesis (ADMET) and ring-opening metathesis polymerisation (ROMP).

Previous papers in this series (1, 2), pointed out that ruthenium indenylidene and vinylidene complexes,

1 and 2,

where R is a phenyl (Ph) or a cyclohexyl (Cy) substituent, constitute a convenient alternative to the first generation Grubbs ruthenium alkylidene metathesis pre-catalysts,

3 and 4 (3, 4), used on a large scale in organic (59) and polymer syntheses (1014).

 

 

Variations in the ligand sphere of the ruthenium atom have been made. These involve mainly the association of certain ancillary ligands, such as N-heterocyclic carbenes (imidazolin-2-ylidene and its saturated derivative), heterocyclic N-donating ligands (pyridine or different N-heterocycles), O- and O,N-chelated ligands (such as phenyl isopropoxy, Schiff-bases),

5 to 12,
(R = Ph or Cy, R′ = Ph or Me) (1531). However, the synthesis of novel metathesis initiators of improved accessibility and with a better application profile is still a challenge to organometallic and metathesis researchers.

 

The present work is devoted to a vast and promising class of ruthenium metathesis pre-catalysts, derived essentially from neutral and cationic ruthenium allenylidene complexes,

13 and 14,
respectively, (R = Ph or Cy, X = PF6, BF4, BPh4, OTf), that gained wide applicability as metathesis initiators due to their easy accessibility and good to excellent catalytic properties.

 

Types of Ruthenium Allenylidene Complexes

The family of neutral and cationic ruthenium allenylidene complexes is very large (3237) and a considerable number of its members are now recognised as active metathesis catalysts (5, 6, 33).

Neutral Ruthenium Allenylidene Complexes

Three neutral, coordinatively unsaturated 16-electron ruthenium allenylidene complexes, of different types, namely the bisphosphane complex

15, the imidazolin-2-ylidene complex

16 and the bimetallic complex

17, have been prepared and evaluated for their catalytic efficacy in alkene metathesis reactions (38, 39).

 

 

 

The bisphosphane complex, 15, is the allenylidene analogue of Grubbs catalyst

3, but with PCy3 ligands (4). A complex similar to

15 but having PPh3 groups instead of PCy3, seems to be rather unstable under normal conditions and rearranges readily to indenylidene, as will be shown in a later section. More stable but less active, the imidazolin-2-ylidene complex,

16, which is the allenylidene analogue of complex

5, stems from complex

15 by simple ligand substitution. The binuclear allenylidene complex,

17, is a highly active metathesis ruthenium complex, and is related to the binuclear benzylidene complex [Ru2Cl4(=CHPh)(p-cymene)(PCy3)] reported earlier by Grubbs and coworkers (40).

Cationic Ruthenium Allenylidene Complexes

Up to now, a vast library of cationic, coordinatively saturated 18-electron ruthenium allenylidene complexes, has been reported (4148) and many of these have been successfully applied in various alkene metathesis (49) and ring-opening metathesis polymerisation (ROMP) reactions (50). Essentially, the main representatives of this class of allenylidene complexes, for example, complexes 18–21, contain η6-arene ligands associated with phosphane and chloride, in conjunction with a ‘non-coordinating’ counterion X.

 

By varying the substituents at the phosphine (R = Ph, Cy, i-Pr) and allenylidene moieties (R′ = Ph, p-chlorophenyl, p-methoxyphenyl, etc.), and the nature of the counterion X (X = PF6, BPh4, BF4, OTf, etc.) a great number of this type of ruthenium complex could be conveniently prepared. Due to easy accessibility, their potential as metathesis pre-catalysts has been extensively evaluated. Some of them allowed metathesis reactions to be performed in ionic liquids of the type 1-butyl-3- methylimidazolium salts, as their cationic nature ensured a high solubility of the catalytic species in the reaction medium (51).

Incorporation of imidazolin-2-ylidene as the ancillary ligand in the arene ruthenium allenylidene complexes, such as 22, provided very active initiators in the ROMP of cycloolefins (52).

 

Moreover, binding the arene ligand with the dihydroimidazolin-2-ylidene unit through a methylene tether, in a half-sandwich mode, led to the η16-arene-carbene ruthenium allenylidene complex,

23 which was highly active in ring-closing metathesis (RCM) of 1,6-dienes (53). Complex

23 allowed the metathesis of dienes to be selectively directed towards either RCM or cycloisomerisation products.

 

A structurally different cationic ruthenium allenylidene complex

24, with two phosphines containing hemilabile methoxy groups, has also been reported (54). This bidentate ruthenium complex showed a lower activity in RCM of dienes and ROMP of cycloolefins as compared with the arene ruthenium complex of type

18, but the synthesis and structure of

24 are challenging issues.

 

Numerous advantages are offered in many applications by the heterogenised version

25 of the arene ruthenium complex

18, obtained through immobilisation on polystyrene (55).

 

This supported ruthenium pre-catalyst has been reused several times in RCM of dienes, but this was possible only after reactivation in a separate process.

Miscellaneous Ruthenium Allenylidene Complexes

The exchange of the triphenylphosphines in [RuCl2(PPh3)3] with water-soluble phosphines, followed by reaction with 3,3-diphenylpropyn-3-ol (in methanol (MeOH)) gave the dimeric ruthenium allenylidene complex

26 which was able to initiate, under certain conditions (protic solvents), ROMP of cycloolefins (56). For instance, in ROMP of cyclopentene, complex

26 led to considerable polymer yields when, in order to activate the catalytic system, Brönsted acids were used as co-initiators.

 

A large array of neutral and ionic ruthenium allenylidene complexes, bearing quite diverse ligands and substituents, has been prepared and their catalytic properties in various chemical transformations investigated (5762). Some of these ligands or substituents might induce asymmetry in the metal complex, generating chiral ruthenium allenylidene catalysts of significance for enantio-selective metathesis catalysis.

Synthesis of Ruthenium Allenylidene Complexes

Neutral Ruthenium Allenylidene Complexes

The neutral, 16-electron ruthenium allenylidene complex

15 was synthesised almost simultaneously by Fürstner and Hill (38), and Nolan and coworkers (39) by reacting [RuCl2(PPh3)3] or [RuCl2(PPh3)4] with commercially-available 3,3-diphenylpropyn-3-ol, followed by PCy3, see Equation (i).

 

A similarly straightforward route for synthesis of the PPh3 analogue (15a) has been reported by Hill and coworkers (63) but subsequent detailed investigation of its structure has proved that the compound is really the ruthenium 3-phenyl-1-indenylidene complex 11, supposedly formed by intramolecular rearrangement of an allenylidene structure, 15a,

previously formulated for this complex (39b), see Equation (ii).

 

Synthesis of complex 15 can also conveniently start from the commercially available ruthenium dimer 27, which reacts with 3,3-diphenylpropyn-3-ol and 2 equivalents of tricyclohexylphosphine. Further substitution of a phosphane group with 1,3-dimesitylimidazolin-2-ylidene readily affords the ruthenium imidazolin-2-ylidene allenylidene complex

16 (39) (Scheme I).

 

Single-crystal X-ray studies on these two ruthenium allenylidene complexes,

15 and 16, provided significant information about bonding in the solid state and electronic environment at the metal centre (39). Unfortunately, the experimental catalytic activity of complexes 15 and 16 in some ring-closing metathesis of dienes was low, although both complexes are rather stable under the reaction conditions. However, a valuable representative of this group, the highly active bimetallic ruthenium allenylidene complex

17, has been prepared in appreciable yield from the same ruthenium dimer

27 and the ruthenium complex

15 (38), see Equation (iii).

 

This latter complex, 17, has been successfully employed in an array of RCM and enyne metathesis reactions.

Cationic Ruthenium Allenylidene Complexes

It is noteworthy that a wide range of cationic 18-electron ruthenium allenylidene complexes, prepared by several research teams using the commercial 3,3-diphenylpropyn-3-ol as the allenylidene moiety source, came as a valuable bonus to state-of-the-art metathesis catalysis (4047). Thus, a convenient method for synthesis of the ruthenium complex

18a (R = Ph, Cy or i-Pr) is based on the commercially available ruthenium dimer 27, which is first converted to the corresponding monophosphane complex 28 (R = Ph, Cy or i-Pr). The latter,

28, is then reacted with 3,3-diphenylpropyn-3-ol, in the presence of NaPF6 (or NaBPh4, etc.) in MeOH at room temperature to give high yields (92–97%) of allenylidene product (49), see Equation (iv).

 

In the final complex, the sterically encumbered phosphane ligand R3P prevents further attack of MeOH at the electrophilic α-C atom of the allenylidene group, which would lead to the formation of the Fischer-type carbene complex [(p-cymene)(R3P)ClRu=CH(OMe)CH=CPh2] (64). Several other ruthenium allenylidene complexes, such as

18b
(R = Ph, p-chlorophenyl, p-methoxyphenyl, CR2 = fluorenylidene, etc.) could be obtained by a similar method, in aprotic solvents. Thus, on treatment with AgX (X = PF6, BF4, OTf, etc.) in CH2Cl2, the monophosphane complex

28

forms the rather stable cationic 16-electron complex,

29. The latter compound reacts rapidly with the suitably substituted propyn-3-ol (in CH2Cl2 at room temperature) to give the corresponding ruthenium allenylidene complex

18b in appreciable yields (80–95%) (49, 65), see Equation (v).

 

It is important to emphasise the ready transformation of 18-electron ruthenium allenylidene complexes into their ruthenium indenylidene counterparts, via the alkenylcarbyne Ru species, in the presence of strong acids, such as triflic acid (TfOH). In this respect, Dixneuf and coworkers (66) clearly evidenced, by 13C{1H} and 1H NMR, the generation of the corresponding alkenylcarbyne derivative from complex

18b (R = Ph, X = OTf), at –40°C. However, at –20°C the latter intermediate (an alkenyl carbyne derivative) was transformed into the 18-electron arene ruthenium indenylidene complex,

30 (Scheme II).

 

Remarkably, this ionic, 18-electron arene ruthenium indenylidene complex, arising from the easily-made allenylidene precursor, showed exceedingly high catalytic activity in various metathesis reactions, such as RCM of N-containing dienes (e.g., of N,N-diallyltosyl amide), enyne metathesis (e.g., of N,N-allylpropargyltosyl amide), ADMET (e.g., of 1,8-decadiene) and ROMP of low-strain cycloolefins (e.g., cyclopentene and cyclooctene), even operating at 0°C.

A further variation on these ruthenium complexes consists of the replacement of the p-cymene ligand with other arenes, capable of binding coordinatively at the Ru centre, prior to introduction of the allenylidene ligand in the final step. Thus, cleavage of the commercial ruthenium dimer

27 with an aralkyl phosphine, in CH2Cl2 at room temperature, followed by an intramolecular substitution of the p-cymene ligand with the tethered phenyl ring (in chlorobenzene at 140°C) yields the ruthenium complex

31. This intermediate is finally converted, in substantial yields (83–91%), into the new chelated ruthenium allenylidene complex

32, via the above discussed protic or aprotic approach (49) (Scheme III).

 

The single-crystal X-ray studies of complexes

18a (R = i-Pr),

31 and 32 gave, for the first time, interesting data about the structure of these types of complexes and convincingly unravelled the nature of the coordination bonds of the ligands around the ruthenium centre (49).

Catalytic Properties of Ruthenium Allenylidene Complexes

Except for a few cases, both families of ruthenium allenylidene complexes, that is: the neutral, coordinatively unsaturated 16-electron and the cationic, coordinatively saturated 18-electron complexes, evidenced good to excellent catalytic activity and selectivity in various metathesis reactions (RCM, ADMET, enyne metathesis, ROMP). By virtue of these catalytic properties and taking into account their easy accessibility from commercial reagents, the class of ruthenium allenylidene complexes holds promise as challenging candidates for productive applications in organic and polymer syntheses. For instance, the neutral, 16-electron ruthenium complex

17 proved to be a highly effective pre-catalyst for RCM of α,ω-dienes and dienynes, at ambient temperature (38). This complex is largely tolerant of functional groups including amide, sulfonamide, bromide, ester, ether, siloxane and fluorenylmethoxycarbonyl substituents. It allows facile and efficient formation of variously functionalised mono- and bicyclic ring systems. Among these compounds, we should mention the structurally complex precursors to exaltolide, a musk odorant, and epilachnene, an insect repellent alkaloid isolated from the pupae of a Mexican beetle.

Syntheses of cyclic compounds via RCM and enyne metathesis using the above binuclear ruthenium allenylidene pre-catalyst are illustrated in Equations (vi) and (vii).

 

 

The catalytic performances of the cationic, 18-electron ruthenium complexes of type

14 in RCM of a variety of dienes and in enyne metathesis have been extensively evaluated by Dixneuf and Fürstner (49). The most important finding was that the metathesis activity of these complexes depends essentially on the nature of the phosphane ligand, the remote substituent of the allenylidene moiety and the nature of the “non-coordinating” counterion. For instance, detailed studies on the catalytic activity of cationic complex

14, X = PF6, in RCM of N,N-diallyltosyl amide, revealed that when varying the phosphane ligands the catalytic activity decreased in the following order: PCy3 > Pi-Pr3 >> PPh3, in accordance with previous observations for the related ruthenium alkylidene pre-catalysts (67). With

14-PF6 (R = PCy3) (2.5 mol%) N,N-diallyltosyl amide was quantitatively converted to N-tosyl dihydropyrrole, after 4 h reaction time, in toluene, at 80°C (isolated yield 83%), see Equation (viii).

 

The above ruthenium pre-catalyst has been applied in RCM of several representative diene substrates allowing synthesis of essentially all ring sizes greater than four, including mono and bicyclic compounds, in good to excellent yields. As expected, the formation of medium sized rings required particularly long reaction times (up to 100 h) and high dilution conditions, while decomposition of the catalytic species seemed to occur with a rate similar to that of the productive RCM. Despite these inherent inconveniences, a large number of heterocyclic compounds pertaining to different heterocyclic systems could also be obtained in good yield (77–88%) by this procedure, see Equations (ix) and (x)

 

 

Of great synthetic utility, the complex

14-PF6
(R = PCy3) allows efficient synthesis of a set of uncommon macrocyclic compounds; for instance, smooth cyclisations of dienes

A

and

B

to the 16- and 18-membered cycloalkenes I and II, respectively, have been successfully achieved by this procedure, see Equations (xi) and (xii).

 

 

As just mentioned, compound

I is a precursor of the valuable macrocyclic musk, Exaltolide (a perfume ingredient). Furthermore, disaccharide

III, obtained by cyclisation of the polyfunctional diene

C, see Equation (xiii), constitutes an advanced intermediate for synthesis of tricolorin A, a carcinostatic resin glycoside.

 

A characteristic feature of these ionic catalytic systems is the fact that the counterion exerts a particular influence on the reactivity of the ruthenium allenylidene complex as well as on the selectivity to metathesis products (48). Thus, whereas cation

14, associated with PF6, BPh4 or OTf, leads to excellent yields at 80°C, in toluene, its combination with OTf was found to be effective – even at room temperature. This behaviour was tentatively ascribed to the weakly coordinating propensity of the triflate group which may assist the decomplexation process of the p-cymene ligand from the 18-electron allenylidene pre-catalyst and may also potentially stabilise, in solution, the resulting 14-electron Ru(II) species (49), see Equation (xiv).

 

Surprisingly, the allenylidene complex

14 having BPh4 or BF4 as counterions is less active and selective, giving rise to numerous side reactions. For instance, with BF4 as the counterion, the ruthenium complex

14 induced cycloisomerisation of N,N-diallyltosyl amide to methylenecyclopentane (42%), with concomitant cyclisation to N-tosyl dihydropyrrole (31%) and isomerisation to a new diene (18%) (48), see Equation (xv).

 

Relevant studies on the effect that some additives have on the catalytic activity of the allenylidene complex

14 during N,N-diallyltosyl amide cyclisation pointed out that addition of Lewis or Brönsted acids (e.g., BF3/Et2O, HBF4/Et2O, F3CSO3H) increased selectively the RCM activity while almost completely suppressing the above cycloisomerisation. By contrast, ammonium salts (e.g., n-Bu4NF) dramatically decreased the overall activity of the complex (49). These interesting observations constitute valuable information for assessing the reaction mechanisms promoted by cationic ruthenium allenylidene complexes.

It is worth noting that allenylidene ligands included in complexes

18 to 20
exert a pronounced influence on the activity of these catalytic systems, and essentially on the selectivity of the reaction products (49). For instance, in the reaction of N,N-diallyltosyl amide discussed above it was possible to alter the catalytic activity of the complex or to switch the reaction pathway from RCM to predominantly cycloisomerisation, simply by varying the distal para-substituents in the phenyl rings of the allenylidene units. This unprecedented result seems to indicate that the allenylidene moiety or a species derived thereof serves as a permanent ligand to the Ru-template throughout the entire catalytic cycle. This behaviour differs fundamentally from that of the parent Grubbs alkylidene complexes

3 and 4, in which the Ru=CHR fragment of the catalyst precursor intervenes only in the initiation process when CHR is cleaved off by reaction with the alkene substrate generating the Ru=CH2 unit, further responsible for the propagation (68).

Very importantly, ruthenium complex

14 can be photochemically activated efficiently by irradiation with UV light (300 nm), as was found earlier for the immobilised phosphane complex

25 (R = Cy) (69). Thus, irradiation of a solution of this catalyst and N,N-diallyltosyl amide allows RCM of the unsaturated substrate to proceed in appreciable yield (81%), even at ambient temperature (49), see Equation (xvi).

 

Such a photochemical activation technique has been successfully applied to a number of enyne substrates which could be conveniently converted into the substituted 3-vinyl-2,5-dihydrofuran derivatives, under these relatively mild conditions (70).

Enyne metathesis, a versatile method for the synthesis of unsaturated bicyclic and polycyclic compounds, has also been effectively performed using the cationic ruthenium allenylidene complex

14. A representative example is the synthesis, in good yield (86%), of 2,2′,5,5′-tetrahydro-3,3′-bifuran from the corresponding dienyne using 2.5 mol% complex

14-BF4, in toluene, at 80°C (48), see Equation (xvii).

 

Related with the cationic p-cymene ruthenium allenylidene complexes discussed above, the chelated compound

32 (with OTf), containing the tethered phenyl ring instead of p-cymene as the ligand, showed good activity and stability in RCM reactions, allowing synthesis of macrocyclic compounds in appreciable yield, see Equation (xviii).

 

One of the basic structural parameters for this type of chelated ruthenium complexes, namely the nature of the ‘non-coordinating’ counterion X, was found to play an important part in determining their activity and stability in metathesis reactions.

Conclusions

The well defined, neutral and cationic ruthenium allenylidene complexes constitute a new, attractive class of highly effective pre-catalysts for various olefin metathesis reactions. They are easily accessible from commercial reagents, display a wide range of activity and selectivity in metathesis reactions, and show good tolerance towards a large array of functional groups.

This class of ruthenium complexes allows the synthesis of many hetero- and carbocyclic compounds by ring-closing metathesis (RCM) and enyne metathesis as well as production of specialty polymers from cycloolefins by ring-opening metathesis polymerisation (ROMP). Their activity and selectivity can be finely tuned by: suitable variations in the ligand sphere of the metal, appropriate substitution on the allenylidene moiety and a proper choice of the ‘non-coordinating’ counterion.

Of great significance for practical applications is the observation that the catalytic activity of the cationic, 18-electron ruthenium complexes can be further enhanced by addition of Lewis or Brönsted acids or by irradiation with UV light. Single-crystal X-ray studies unambiguously determined the structures of the neutral, 16-electron, and cationic, 18-electron ruthenium allenylidene complexes and also the defining features of the metal-ligand bonds.

The majority of the ruthenium allenylidene complexes are rather stable at room temperature or upon heating. Compelling proof exists that some ruthenium allenylidene complexes rearrange intramolecularly to the parent ruthenium indenylidene complexes, the latter also displaying high metathesis activity and selectivity. Elegant NMR studies clearly evidenced, for the first time, the transformation of cationic ruthenium allenylidene complexes into the indenylidene congeners via alkenylcarbyne ruthenium species.

Overall, the ready accessibility and good to excellent catalytic properties of the well-defined ruthenium allenylidene complexes turn out to be valuable bases for further development and refinement of this class of metathesis pre-catalysts.

BACK TO TOP

References

  1.  V. Dragutan, I. Dragutan and F. Verpoort, Platinum Metals Rev., 2005, 49, (1), 33 LINK http://dx.doi.org/10.1595/147106705X24580
  2.  V. Dragutan and I. Dragutan, Platinum Metals Rev., 2004, 48, (4), 148 LINK http://dx.doi.org/10.1595/147106704X4835
  3.  P. Schwab, R. H. Grubbs and J. W. Ziller, J. Am. Chem. Soc., 1996, 118, (1), 100 LINK http://dx.doi.org/10.1021/ja952676d
  4.  B. M. Novak and R. H. Grubbs, J. Am. Chem. Soc., 1988, 110, (22), 7542 LINK http://dx.doi.org/10.1021/ja00230a047
  5.  S. T. Nguyen, L. K. Johnson, R. H. Grubbs and J. W. Ziller, J. Am. Chem. Soc., 1992, 114, (10), 3974 LINK http://dx.doi.org/10.1021/ja00036a053
  6.  S. T. Nguyen, R. H. Grubbs and J. W. Ziller, J. Am. Chem. Soc., 1993, 115, (21), 9858 LINK http://dx.doi.org/10.1021/ja00074a086
  7.  “Handbook of Metathesis”, ed.R. H. Grubbs, Wiley-VCH,Weinheim,2003, Vol. I–II
  8.  T. N. Trnka and R. H. Grubbs, Acc. Chem. Res., 2001, 34, (1), 18 LINK http://dx.doi.org/10.1021/ar000114f
  9.  R. H. Grubbs and S. Chang, Tetrahedron, 1998, 54, (18), 4413 LINK http://dx.doi.org/10.1016/S0040-4020(97)10427-6
  10.  V. Dragutan, I. Dragutan and A. T. Balaban, Platinum Metals Rev., 2001, 45, (4), 155 LINK http://www.ingentaconnect.com/content/matthey/pmr/2001/00000045/00000004/art00003
  11.  V. Dragutan, I. Dragutan and A. T. Balaban, Platinum Metals Rev., 2000, 44, (2), 58 LINK http://www.ingentaconnect.com/content/matthey/pmr/2000/00000044/00000002/art00006
  12.  V. Dragutan, I. Dragutan and A. T. Balaban, Platinum Metals Rev., 2000, 44, (3), 112 LINK http://www.ingentaconnect.com/content/matthey/pmr/2000/00000044/00000003/art00007
  13.  I. Dragutan, V. Dragutan and P. Filip, ARKIVOC, 2005, (x), 105 LINK http://www.arkat-usa.org/ark/journal/2005/I10_Balaban/1334/1334.asp
  14.  A. Fürstner, Angew. Chem. Int. Ed., 2000, 39, (17), 3012 LINK http://dx.doi.org/10.1002/1521-3773(20000901)39:173.3.CO;2-7
  15.  A. Fürstner, Top. Organomet. Chem., 1998, 1, 37
  16.  M. Buchmeiser, Chem. Rev., 2000, 100, (4), 1565 LINK http://dx.doi.org/10.1021/cr990248a
  17.  S. J. Connon and S. Blechert, Angew. Chem. Int. Ed., 2003, 42, (17), 1900 LINK http://dx.doi.org/10.1002/anie.200200556
  18.  K. J. Ivin, J. Mol. Catal. A: Chem., 1998, 133, (1–2), 1 LINK http://dx.doi.org/10.1016/S1381-1169(97)00249-5
  19.  “Novel Metathesis Chemistry: Well-Defined Initiator Systems for Speciality Chemical Synthesis, Tailored Polymers and Advanced Material Applications”,eds.Y. Imamoglou and L. Bencze, NATO Advanced Study Institute (ASI), Kluwer Academic Publishers, Dordrecht, The Netherlands, 2003
  20.  “Handbook of Metathesis”, ed.R. H. Grubbs, Wiley-VCH,Weinheim, 2003, Vol. III
  21.  V. Dragutan and R. Streck, “Catalytic Polymerisation of Cycloolefins”, Elsevier, Amsterdam, The Netherlands, 2000
  22.  K. J. Ivin and J. C. Mol, “Olefin Metathesis and Metathesis Polymerisation”, Academic Press, London, U.K., 1997
  23.  “Ring-Opening Metathesis Polymerisation and Related Chemistry”, eds.E. Khosravi and T. Szymanska-Buzar, NATO Advanced Study Institute (ASI), Kluwer Academic Publishers, Dordrecht, The Netherlands, 2002
  24.  V. Dragutan, I. Dragutan and A. Demonceau, Platinum Metals Rev., 2005, 49, (3), 123 LINK http://dx.doi.org/10.1595/147106705X54253
  25.  V. Dragutan, I. Dragutan and A. Demonceau, Platinum Metals Rev., 2005, 49, (4), 183 LINK http://dx.doi.org/10.1595/147106705X70282
  26.  I. Dragutan, V. Dragutan, L. Delaude and A. Demonceau, ARKIVOC, 2005, (x), 206 LINK http://www.arkat-usa.org/ark/journal/2005/I10_Balaban/1512/1512.asp
  27.  M. Scholl, T. M. Trnka, J. P. Morgan and R. H. Grubbs, Tetrahedron Lett., 1999, 40, (12), 2247 LINK http://dx.doi.org/10.1016/S0040-4039(99)00217-8
  28.  M. S. Sanford, M. Ulman and R. H. Grubbs, J. Am. Chem. Soc., 2001, 123, (4), 749 LINK http://dx.doi.org/10.1021/ja003582t
  29.  T. M. Trnka, E. L. Dias, M. W. Day and R. H. Grubbs, ARKIVOC, 2002, (xiii), 28 LINK http://www.arkat-usa.org/ark/journal/2002/I13_Karabatsos/GK-719F/719F.asp
  30.  T. Weskamp, W. Schattenmann, M. Spiegler and W. A. Herrmann, Angew. Chem., 1998, 110, (18), 2631 LINK http://dx.doi.org/10.1002/(SICI)1521-3757(19980918)110:183.0.CO;2-J
  31.  T. Weskamp, W. Schattenmann, M. Spiegler and W. A. Herrmann, Angew. Chem. Int. Ed., 1998, 37, (18), 2490 LINK http://dx.doi.org/10.1002/(SICI)1521-3773(19981002)37:183.0.CO;2-X
  32.  T. Weskamp, F. J. Kohl, W. Hieringer, D. Gleich and W. A. Herrmann, Angew. Chem., 1999, 111, (16), 2573 LINK http://dx.doi.org/10.1002/(SICI)1521-3757(19990816)111:163.3.CO;2-1
  33.  T. Weskamp, F. J. Kohl, W. Hieringer, D. Gleich and W. A. Herrmann, Angew. Chem. Int. Ed., 1999, 38, (16), 2416 LINK http://onlinelibrary.wiley.com/doi/10.1002/%28SICI%291521-3773%2819990816%2938:16%3C2416::AID-ANIE2416%3E3.0.CO;2-%23/abstract
  34.  L. Ackermann, A. Fürstner, T. Weskamp, F. J. Kohl and W. A. Herrmann, Tetrahedron Lett., 1999, 40, (26), 4787 LINK http://dx.doi.org/10.1016/S0040-4039(99)00919-3
  35.  J. Huang, H. J. Schanz, E. D. Stevens and S. P. Nolan, Organometallics, 1999, 18, (25), 5375 LINK http://dx.doi.org/10.1021/om990788y
  36.  J. Huang, E. D. Stevens, S. P. Nolan and J. L. Petersen, J. Am. Chem. Soc., 1999, 121, (12), 2674 LINK http://dx.doi.org/10.1021/ja9831352
  37.  M. Scholl, S. Ding, C. W. Lee and R. H. Grubbs, Org. Lett., 1999, 1, (6), 953 LINK http://dx.doi.org/10.1021/ol990909q
  38.  C. W. Bielawski, O. A. Sherman and R. H. Grubbs, Polymer, 2001, 42, (11), 4939 LINK http://dx.doi.org/10.1016/S0032-3861(00)00504-8
  39.  A. Mühlebach, P. A. van der Schaaf, A. Hafner, R. Kolly, F. Rime and H. J. Kimer, in“Ring-Opening Metathesis Polymerisation and Related Chemistry”, eds.E. Khosravi and T. Szymanska-Buzar, NATO Advanced Study Institute (ASI), Kluwer Academic Publishers, Dordrecht, The Netherlands, 2002, pp. 23–44
  40.  S. B. Garber, J. S. Kingsbury, B. L. Gray and A. H. Hoveyda, J. Am. Chem. Soc., 2000, 122, (34), 8168 LINK http://dx.doi.org/10.1021/ja001179g
  41.  S. Chang, L. Jones, C. Wang, L. M. Henling and R. H. Grubbs, Organometallics, 1998, 17, (16), 3460 LINK http://dx.doi.org/10.1021/om970910y
  42.  B. De Clercq and F. Verpoort, Adv. Synth. Catal., 2002, 344, (6–7), 639 LINK http://www3.interscience.wiley.com/cgi-bin/abstract/98015856/ABSTRACT
  43.  B. De Clercq and F. Verpoort, J. Mol. Catal. A: Chem., 2002, 180, (1–2), 67 LINK http://dx.doi.org/10.1016/S1381-1169(01)00451-4
  44.  R. Drozdzak, B. Allaert, N. Ledoux, I. Dragutan, V. Dragutan and F. Verpoort, Adv. Synth. Catal., 2005, 347, (14), 1721 LINK http://dx.doi.org/10.1002/adsc.200404389
  45.  R. Drozdzak, B. Allaert, N. Ledoux, I. Dragutan, V. Dragutan and F. Verpoort, Coord. Chem. Rev., 2005, 249, (24), 3055 LINK http://dx.doi.org/10.1016/j.ccr.2005.05.003
  46.  B. De Clercq, F. Lefebvre and F. Verpoort, New J. Chem., 2002, 26, (9), 1201 LINK http://dx.doi.org/10.1039/b202872g
  47.  B. De Clercq, F. Lefebvre and F. Verpoort, Appl. Catal. A: Gen., 2003, 247, (2), 345 LINK http://dx.doi.org/10.1016/S0926-860X(03)00126-1
  48.  T. Opstal and F. Verpoort, Angew. Chem. Int. Ed., 2003, 42, (25), 2876 LINK http://dx.doi.org/10.1002/anie.200250840
  49.  R. Drozdzak, N. Ledoux, B. Allaert, I. Dragutan, V. Dragutan and F. Verpoort, Central Eur. J. Chem., 2005, 3, (3), 404 LINK http://dx.doi.org/10.2478/BF02479271
  50.  J. A. Love, J. P. Morgan, T. M. Trnka and R. H. Grubbs, Angew. Chem. Int. Ed., 2002, 41, (21), 4035 LINK http://dx.doi.org/10.1002/1521-3773(20021104)41:213.0.CO;2-I
  51.  T. L. Choi and R. H. Grubbs, Angew. Chem. Int. Ed., 2003, 42, (15), 1743 LINK http://dx.doi.org/10.1002/anie.200250632
  52.  A. Demonceau, A. F. Noels, E. Saive and A. J. Hubert, J. Mol. Catal., 1992, 76, (1–3), 123 LINK http://dx.doi.org/10.1016/0304-5102(92)80151-6
  53.  A. W. Stumpf, E. Saive, A. Demonceau and A. F. Noels, J. Chem. Soc., Chem. Commun., 1995, (11), 1127 LINK http://dx.doi.org/10.1039/c39950001127
  54.  A. Demonceau, A. W. Stumpf, E. Saive and A. F. Noels, Macromolecules, 1997, 30, (11), 3127 LINK http://dx.doi.org/10.1021/ma961040j
  55.  F. Simal, A. Demonceau and A. F. Noels, Recent Res. Develop. Org. Chem., 1999, 3, 455
  56.  A. Hafner, A. Mühlebach and P. A. van der Schaaf, Angew. Chem., 1997, 109, (19), 2213 LINK http://www3.interscience.wiley.com/cgi-bin/abstract/112392561/ABSTRACT
  57.  A. Hafner, A. Mühlebach and P. A. van der Schaaf, Angew. Chem. Int. Ed., 1997, 36, (19), 2121 LINK http://dx.doi.org/10.1002/anie.199721211
  58.  T. Karlen, A. Ludi, A. Muhlebach, P. Bernhard and C. Pharisa, J. Polym. Sci. A: Polym. Chem., 1995, 33, (10), 1665 LINK http://dx.doi.org/10.1002/pola.1995.080331013
  59.  A. F. Hill, in“Comprehensive Organometallic Chemistry”, eds., E. W. Abel, F. G. A. Stone and G. Wilkinson, Vol. II, Pergamon Press, Oxford, 1995, Vol. 7, pp. 348–356;
  60.  M. I. Bruce, Coord. Chem. Rev., 2004, 248, (15–16), 1603 LINK http://dx.doi.org/10.1016/j.ccr.2004.05.007
  61.  M. I. Bruce, Chem. Rev., 1998, 98, (8), 2797 LINK http://dx.doi.org/10.1021/cr970473x
  62.  N. Mantovani, M. Brugnati, L. Gonsalvi, E. Grigiotti, F. Laschi, L. Marvelli, M. Peruzzini, G. Reginato, R. Rossi and P. Zanello, Organometallics, 2005, 24, (3), 405 LINK http://dx.doi.org/10.1021/om0492193
  63.  D. Semeril and P. H. Dixneuf, in: “Novel Metathesis Chemistry: Well-Defined Initiator Systems for Speciality Chemical Synthesis, Tailored Polymers and Advanced Material Applications”, eds., Y. Imamoglou and L. Bencze, NATO Advanced Study Institute (ASI), Kluwer Academic Publishers, Dordrecht, The Netherlands, 2003
  64.  R. Castarlenas, C. Fischmeister, C. Bruneau and P. H. Dixneuf, J. Mol. Catal. A: Chem., 2004, 213, (1), 31 LINK http://dx.doi.org/10.1016/j.molcata.2003.10.048
  65.  R. Castarlenas, C. Vovard, C. Fischmeister and P. H. Dixneuf, J. Am. Chem. Soc., 2006, 128, (12), 4079 LINK http://dx.doi.org/10.1021/ja0579762
  66.  C. Bruneau and P. H. Dixneuf, Angew. Chem. Int. Ed., 2006, 45, (14), 2176 LINK http://dx.doi.org/10.1002/anie.200501391
  67.  R. Rigaut, D. Touchard and P. H. Dixneuf, Coord. Chem. Rev., 2004, 248, (15–16), 1585 LINK http://dx.doi.org/10.1016/J.ccr.2004.04.016
  68.  P. H. Dixneuf and C. Bruneau, in“Organic Synthesis via Organometallics”, ed.G. Helmchen, Viegweg, Wiesbaden, Germany, 1997, pp. 1–20
  69.  C. Bruneau, Top. Organomet. Chem., 2004, 11, 125 LINK http://dx.doi.org/10.1007/b94647
  70.  R. F. Winter and S. Zalis, Coord. Chem. Rev., 2004, 248, (15–16), 1565 LINK http://dx.doi.org/10.1016/j.ccr.2004.05.005
  71.  R. F. Winter, K.-W. Klinkhammer and S. Zalis, Organometallics, 2001, 20, (7), 1317 LINK http://dx.doi.org/10.1021/om000925n
  72.  B. Schmidt, Angew. Chem. Int. Ed., 2003, 42, (41), 4996 LINK http://dx.doi.org/10.1002/anie.200301688
  73.  S. Hartmann, R. F. Winter, B. Sarkar and F. Lissner, Dalton Trans., 2004, (20), 3273 LINK http://dx.doi.org/10.1039/b406940d
  74.  M. Tamm, T. Jentzsch and W. Werncke, Organometallics,1997, 16, (7), 1418 LINK http://dx.doi.org/10.1021/om9610556
  75.  A. Fürstner, A. F. Hill, M. Liebl and J. D. E. T. Wilton-Ely, Chem. Commun., 1999, (7), 601 LINK http://dx.doi.org/10.1039/a900187e
  76.  H. J. Schanz, L. Jafarpour, E. D. Stevens and S. P. Nolan, Organometallics, 1999, 18, (24), 5187 LINK http://dx.doi.org/10.1021/om9906316
  77.  L. Jafarpour, H. J. Schanz, E. D. Stevens and S. P. Nolan, Organometallics, 1999, 18, (25), 5416 LINK http://dx.doi.org/10.1021/om990587u
  78.  E. L. Dias and R. H. Grubbs, Organometallics, 1998, 17, (13), 2758 LINK http://dx.doi.org/10.1021/om9708788
  79.  J. P. Selegue, Organometallics, 1982, 1, (1), 217 LINK http://dx.doi.org/10.1021/om00061a038
  80.  J. P. Selegue, Coord. Chem. Rev., 2004, 248, (15–16), 1543 LINK http://dx.doi.org/10.1016/j.ccr.2004.08.009
  81.  A. Wolinska, D. Touchard, P. H. Dixneuf and A. J. Romero, J. Organomet. Chem., 1991, 420, (2), 217 LINK http://dx.doi.org/10.1016/0022-328X(91)80264-K
  82.  D. Touchard, S. Guesmi, M. Bouchaib, P. Haquette, A. Daridor and P. H. Dixneuf, Organometallics, 1996, 15, (11), 2579 LINK http://dx.doi.org/10.1021/om960139b
  83.  D. Touchard, P. Haquette, A. Daridor, A. Romero and P. H. Dixneuf, Organometallics, 1998, 17, (18), 3844 LINK http://dx.doi.org/10.1021/om980273r
  84.  M. P. Gamasa, J. Gimeno, C. Gonzales-Bernardo, J. Borge and S. Garcia-Granda, Organometallics, 1997, 16, (12), 2483 LINK http://dx.doi.org/10.1021/om970154w
  85.  P. Crochet, B. Demerseman and M. I. Valejo, Organometallics, 1997, 16, (25), 5406 LINK http://dx.doi.org/10.1021/om970513n
  86.  M. A. J. Tenorio, M. J. Tenorio, M. C. Puerta and P. Valerga, Organometallics, 1997, 16, (25), 5528 LINK http://dx.doi.org/10.1021/om970543q
  87.  V. Cadierno, M. P. Gamasa, J. Gimeno, L. Iglesias and S. Garcia-Granda, Inorg. Chem., 1999, 38, (12), 2874 LINK http://dx.doi.org/10.1021/ic9813258
  88.  A. Fürstner, M. Picquet, C. Bruneau and P. H. Dixneuf, Chem. Commun., 1998, (12), 1315 LINK http://dx.doi.org/10.1039/a803286f
  89.  H. Werner, C. Grunwald, P. Steinert, O. Grevert and J. Wolf, J. Organomet. Chem., 1998, 565, (1–2), 231 LINK http://dx.doi.org/10.1016/S0022-328X(98)00623-8
  90.  B. Buriez, I. D. Burns, A. F. Hill, A. J. P. White, D. J. Williams and J. D. E. T. Wilton-Ely, Organometallics, 1999, 18, (8), 1504 LINK http://dx.doi.org/10.1021/om980937x
  91.  A. Fürstner, M. Liebl, C. W. Lehmann, M. Picquet, R. Kunz, C. Bruneau, D. Touchard and P. H. Dixneuf, Chem. Eur. J., 2000, 6, (10), 1847 LINK http://dx.doi.org/10.1002/(SICI)1521-3765(20000515)6:103.0.CO;2-1
  92.  D. Semeril, J. Le Notre, C. Bruneau, P. H. Dixneuf, A. F. Kolomiets and S. N. Osipov, New J. Chem., 2001, 25, (1), 16 LINK http://dx.doi.org/10.1039/b007396m
  93.  R. Castarlenas, D. Semeril, A. F. Noels, A. Demonceau and P. H. Dixneuf, J. Organomet. Chem., 2002, 663, (1–2), 235 LINK http://dx.doi.org/10.1016/S0022-328X(02)01880-6
  94.  S. Csihony, C. Fischmeister, C. Bruneau, I. T. Horvath and P. H. Dixneuf, New J. Chem., 2002, 26, (11), 1667 LINK http://dx.doi.org/10.1039/b205920g
  95.  D. Semeril, H. Olivier-Bourbigou, C. Bruneau and P. H. Dixneuf, Chem. Commun., 2002, (2), 146 LINK http://dx.doi.org/10.1039/b110040h
  96.  D. Semeril, C. Bruneau and P. H. Dixneuf, Adv. Synth. Catal., 2002, 344, (6–7), 585 LINK http://www3.interscience.wiley.com/cgi-bin/abstract/98015829/ABSTRACT
  97.  L. Jafarpour, J. Huang, E. D. Stevens and S. P. Nolan, Organometallics, 1999, 18, (18), 3760 LINK http://dx.doi.org/10.1021/om990357f
  98.  B. Cetinkaya, S. Demir, I. Ozdemir, L. Toupet, D. Semeril, C. Bruneau and P. H. Dixneuf, New J. Chem., 2001, 25, (4), 519 LINK http://dx.doi.org/10.1039/b100264n
  99.  B. Cetinkaya, S. Demir, I. Ozdemir, L. Toupet, D. Semeril, C. Bruneau and P. H. Dixneuf, Chem. Eur. J., 2003, 9, (10), 2323 LINK http://dx.doi.org/10.1002/chem.200204533
  100.  S. Jung, C. D. Brandt and H. Werner, New J. Chem., 2001, 25, (9), 1101 LINK http://dx.doi.org/10.1039/b104787f
  101.  R. Akiyama and S. Kobayashi, Angew. Chem. Int. Ed., 2002, 41, (14), 2602 LINK http://dx.doi.org/10.1002/1521-3773(20020715)41:143.0.CO;2-3
  102.  M. Saoud, A. Romerosa and M. Peruzzini, Organometallics, 2000, 19, (20), 4005 LINK http://dx.doi.org/10.1021/om000507i
  103.  V. Cadierno, J. Diez, M.-P. Gamasa and J. Gimeno, Coord. Chem. Rev., 1999, 193–195, 147 LINK http://dx.doi.org/10.1016/S0010-8545(99)00163-0
  104.  V. Cadierno, S. Conejero, M. P. Gamasa and J. Gimeno, J. Chem. Soc., Dalton Trans., 2000, (4), 451 LINK http://dx.doi.org/10.1039/a908493b
  105.  V. Cadierno, S. Conejero, M. P. Gamasa and J. Gimeno, Dalton Trans., 2003, (15), 3060 LINK http://dx.doi.org/10.1039/b305608b
  106.  V. Cadierno, M.-P. Gamasa and J. Gimeno, Coord. Chem. Rev., 2004, 248, (15–16), 1627 LINK http://dx.doi.org/10.1016/j.ccr.2004.05.008
  107.  V. Cadierno, M. P. Gamasa and J. Gimeno, Eur. J. Inorg. Chem., 2001, (3), 571 LINK http://dx.doi.org/10.1002/1099-0682(200103)2001:33.0.CO;2-2
  108.  C.-Y. Wong, C.-M. Che, M. C. W. Chan, K.-H. Leung, D. L. Philips and N. Zhu, J. Am. Chem. Soc., 2004, 126, (8), 2501 LINK http://dx.doi.org/10.1021/ja0380648
  109.  S. Rigaut, O. Maury, D. Touchard and P. H. Dixneuf, Chem. Commun., 2001, (4), 373 LINK http://dx.doi.org/10.1039/b008893p
  110.  S. Rigaut, F. Monnier, F. Mousset, D. Touchard and P. H. Dixneuf, Organometallics, 2002, 21, (13), 2654 LINK http://dx.doi.org/10.1021/om0200555
  111.  S. Rigaut, D. Touchard and P. H. Dixneuf, Organometallics, 2003, 22, (20), 3980 LINK http://dx.doi.org/10.1021/om0304098
  112.  C. Fischmeister, R. Castarlenas, C. Bruneau and P. H. Dixneuf, in“Novel Metathesis Chemistry: Well-Defined Initiator Systems for Speciality Chemical Synthesis, Tailored Polymers and Advanced Material Applications”, eds., Y. Imamoglou and L. Bencze, NATO Advanced Study Institute (ASI), Kluwer Academic Publishers, Dordrecht, The Netherlands, 2003
  113.  D. Touchard and P. H. Dixneuf, Coord. Chem. Rev., 1998, 178–180, Part 1, 409 LINK http://dx.doi.org/10.1016/S0010-8545(98)00079-4
  114.  M. A. Esteruelas, A. V. Gomez, A. M. Lopez, J. Modrego and E. Onate, Organometallics, 1997, 16, (26), 5826 LINK http://dx.doi.org/10.1021/om9708539
  115.  K. J. Harlow, A. F. Hill and J. D. E. T. Wilton-Ely, J. Chem. Soc., Dalton Trans., 1999, (3), 285 LINK http://dx.doi.org/10.1039/a808817i
  116.  D. Pilette, K. Ouzzine, H. LeBozec, P. H. Dixneuf, C. E. F. Rickard and W. R. Roper, Organometallics, 1992, 11, (2), 809 LINK http://dx.doi.org/10.1021/om00038a046
  117.  M. Picquet, D. Touchard, C. Bruneau and P. H. Dixneuf, New J. Chem., 1999, 23, (2), 141 LINK http://dx.doi.org/10.1039/a808859d
  118.  R. Castarlenas and P. H. Dixneuf, Angew. Chem. Int. Ed., 2003, 42, (37), 4524 LINK http://dx.doi.org/10.1002/anie.200352108
  119.  B. M. Novak and R. H. Grubbs, J. Am. Chem. Soc., 1988, 110, (22), 7542 LINK http://dx.doi.org/10.1021/ja00230a047
  120.  E. L. Dias, S. T. Nguyen and R. H. Grubbs, J. Am. Chem. Soc., 1997, 119, (17), 3887 LINK http://dx.doi.org/10.1021/ja963136z
  121.  A. Fürstner and L. Ackermann, Chem. Commun., 1999, (1), 95 LINK http://dx.doi.org/10.1039/a808810a
  122.  M. Picquet, C. Bruneau and P. H. Dixneuf, Chem. Commun., 1998, (20), 2249 LINK http://dx.doi.org/10.1039/a806005c

The Authors

Valerian Dragutan is a Senior Researcher at the Institute of Organic Chemistry of the Romanian Academy. His research interests are homogeneous catalysis by transition metals and Lewis acids; olefin metathesis and ROMP of cycloolefins; bioactive organometallic compounds; and mechanisms and stereochemistry of reactions in organic and polymer chemistry.

Ileana Dragutan is a Senior Researcher at the Institute of Organic Chemistry of the Romanian Academy. Her interests are in sterically hindered amines, syntheses of olefinic monomers via olefin metathesis, stable organic free radicals as spin probes for ESR of organised systems and membrane bioenergetics. She is also interested in transition metal complexes with free radical ligands.

Read more from this issue »

BACK TO TOP

SHARE THIS PAGE: