Olefin metathesis is a powerful tool for assembly of carbon-carbon bonds. Amines and related N-donors are problematic functional groups in Ru-catalyzed olefin metathesis - a well- documented, but poorly understood problem. The first part of this thesis focuses on amine-induced deactivation pathways; two of which are described in depth. Alkylidene abstraction, a previously unknown reaction for nitrogen nucleophiles, was observed for smaller and less Bronsted-basic amines. Deprotonation of the metallacyclobutane intermediate formed during catalysis is prominent for highly Bronsted basic or sterically bulky N-donors. Monosubstituted (and, by extension unsubstituted) metallacyclobutanes are particularly vulnerable to deprotonation. For each pathway, the fate of the alkylidene Ru=CHR functional group proved key in determining the nature of deactivation. Both pathways have been detected during catalysis, as evidenced by formation of diagnostic amine (RCH2NR2’) or substituted propene products. A combination of quantitative NMR and GC-MS analysis was used to identify these species on loss of the Ru-alkylidene functional group. The second part of this thesis focuses on incorporating amines into catalyst design – an under-utilized strategy in the context of Ru-catalyzed olefin metathesis. A modified Grubbs-type catalyst was developed featuring a bulky, relatively non-basic biaryldiamine ligand. Metathesis activity for this catalyst was comparable, and in some cases superior to the most widely-used homogeneous catalysts currently available. Several new, related Ru-benzylidenes were also prepared and fully characterized in conjunction with the mechanistic studies described above. Progress toward development of N-anion-containing metathesis catalysts is also discussed. Synthesis of Ru-hydride complexes originally intended for this purpose allowed for a fundamental study of the coordination chemistry and reductive elimination chemistry of the NPh2– anion.

Over the past 15 years, ruthenium-catalyzed olefin metathesis has emerged as a cornerstone synthetic methodology in academia. Applications in fine-chemicals and pharmaceutical manufacturing, however, are just beginning to come on stream. Industrial uptake has been impeded by economic constraints associated with catalyst costs. These are due both to direct costs (exacerbated by intellectual property issues), and to further pressure exerted by the low turnover numbers attainable, and the need for extensive purification to remove ruthenium residues. From another perspective, however, these difficulties can be seen as arising from our rudimentary understanding of the fundamental organometallic chemistry of the Ru=CHR bond. In particular, we know little about the nature and reaction pathways of the Ru-methylidene unit present in the active species that propagates metathesis, and in the catalyst resting state. We know slightly more about the ruthenacyclobutane species, but still too little to guide us as to their non-metathetical reaction pathways, their contribution to deactivation relative to the methylidene species, and potential work-arounds. This thesis work was aimed at improving our understanding of the reactivity, speciation, and decomposition of key ruthenium intermediates in olefin metathesis. A major focus was the behaviour and deactivation of species formed from the second-generation Grubbs catalyst RuCl2(H2IMes)(PCy3)(=CHPh) (S-GII), which dominates ring-closing metathesis. Also studied were derivatives of the corresponding IMes catalyst A-GIIm, containing an unsaturated Nheterocyclic carbene (NHC) ligand. The methylidene complexes RuCl2(NHC)(PCy3)(=CH2) (GIIm) represent the resting state of the catalyst during ring-closing and cross-metathesis reactions: that is, the majority Ru species present during catalysis. Mechanistic studies of these key intermediates have been restricted, however, by the low yields and purity with which they could be accessed. Initial work therefore focused on designing a clean, high-yield route to the second-generation Grubbs methylidene complexes S-GIIm and A-GIIm. These routes were subsequently expanded to develop access to isotopically-labelled derivatives. Locating a 13C-label at the key alkylidene site, in particular, offers a powerful means of tracking the fate of the methylidene moiety during catalyst deactivation. Access to GIIm enabled detailed studies of the behaviour and decomposition of the Grubbs catalysts. First, the long-standing question of the impact of saturation of the NHC backbone (i.e. IMes vs. H2IMes) was examined. Dramatic differences in the behaviour of the two complexes were traced to profound differences in PCy3 lability arising from the diminished π-acidity of the IMes ligand. Secondly, the vulnerability of GIIm to nucleophiles was examined. This is an important issue from the perspective of decomposition by adventitious nucleophiles in the reaction medium during catalysis, but also reflects on substrate scope. For amine additives, the dominant deactivation pathway was shown to typically involve attack on the resting-state methylidene complex, not the metallacyclobutane, which has often been regarded as the most vulnerable intermediate. In addition, the sigma-alkyl intermediate formed by nucleophilic attack of displaced phosphine at the methylidene carbon was trapped by moving to the first-generation complex, and using a nitrogen donor (pyridine) that cannot promote decomposition via N–H activation pathways. Interception of this long-suspected species led to the proposal of “donorinduced” deactivation as a general decomposition pathway for Grubbs-class catalysts. Finally, the capacity of phosphine-free catalysts to overcome the shortcomings of the secondgeneration Grubbs catalysts was demonstrated, in a case study involving application of crossmetathesis (CM) to the synthesis of a high-value antioxidant. An efficient CM methodology was developed for the reaction of renewable essential-oil phenylpropenoids with vinyl acrylates. This work illustrates a new paradigm in sustainable metathesis. Rather than degrading unsaturated feedstocks via metathesis (a process that can be termed “metathe[LY]sis”), it demonstrates how metathesis with directly-functionalized olefins can be used to augment structure and function. From the perspective of organometallic chemistry and catalyst design, key comparisons built into this thesis are the effect of the NHC ligand (IMes vs. H2IMes) and its trans ancillary ligand on the efficient entry into catalysis; the susceptibility to nucleophilic attack of the alkylidene ligand (benzylidene vs. methylidene) vs. the metallacyclobutane; and the effect of replacing a phosphine ancillary ligand with a non-nucleophilic donor. From a practical standpoint, Chapter 2 brings new life to metathesis with the high-yield synthesis of the resting state species, Chapters 3 and 4 examine the deactivation, or death, of the methylidene complexes, and Chapter 5 establishes a new paradigm for olefin metathesis within the context of sustainable synthesis.

Olefin metathesis is the most powerful, versatile reaction in current use for the formation of new carbon-carbon bonds. While metathesis has been known for over 60 years, it has only recently been implemented into pharmaceutical and specialty chemical manufacturing. The slow uptake of olefin metathesis can be attributed in part to low catalyst productivity, a consequence of short catalyst lifetime. Improving catalyst activity is critical for the advancement of metathesis. This improvement can be achieved through greater understanding of the catalysts and their limitations. The ability to perform metathesis in aqueous media is desirable, but as yet largely unrealized, for the modification of water-soluble, biologically-relevant substrates. At present, high catalyst loadings are necessary even for less demanding metathesis reactions in water. The limited mutual solubility of the catalyst and substrate in water are one limitation. Examined in this thesis are more fundamental challenges associated with catalyst deactivation by water. The impact of water on catalyst productivity was assessed for both the second-generation Grubbs catalyst GII, and the phosphine-free Hoveyda catalyst HII, in ring-closing and cross-metathesis reactions. Water was shown to have a negative impact on metathesis productivity, owing to catalyst decomposition. The decomposition pathway was catalyst-dependent: GII was found to decompose through a pathway in which water accelerated abstraction of the methylidene ligand by dissociated phosphine. For HII, water was found to decompose the metallacyclobutane intermediate. A β-hydride transfer mechanism was proposed, to account for the organic decomposition products observed. Chapter 4 focuses on problems encountered during the synthesis of ruthenium catalysts, and presents improved methods. An updated method was developed for the synthesis of phenyldiazomethane, the principal source of the alkylidene ligand required in synthesis of GI. Challenges in use of the phosphine-scavenging resin Amberlyst-15 resin are discussed. Improving synthetic routes to the important first- and second-generation Grubbs catalysts will aid in expansion of olefin metathesis methodologies, particularly in the industrial context, in which batch-to-batch reproducibility is paramount.

Olefin metathesis is arguably the most versatile catalytic route yet developed for the assembly of carbon-carbon bonds. Metathesis methodologies are attractive from both synthetic and ecological standpoints, because they employ unactivated double bonds. This reduces the total number of synthetic steps, and the associated generation of chemical wastes. The drive to deploy olefin metathesis in highly demanding contexts, including pharmaceutical manufacturing and chemical biology, puts severe pressure on catalyst lifetime and productivity. Understanding the relevant decomposition pathways is critical to achieve essential performance goals, and to enable informed catalyst redesign. This thesis work expands on significant prior advances that identified and quantified critical decomposition pathways for ruthenium catalysts stabilized by N-heterocyclic carbene (NHC) ligands. Because pristine catalyst materials are essential for mechanistic study, it focuses first on methods aimed at improving efficiency and purity in catalyst synthesis. Merrifield iodide resins were shown to function as efficient, selective phosphine scavengers in the production of clean second-generation catalysts from PCy3- stabilized precursors. The thesis then turns to mechanistic examination of decomposition pathways that underlie success and failure for leading NHC catalysts, for comparison with a new family of catalysts stabilized by cyclic (alkyl)(amino) carbene (CAAC) ligands. These represent the first in-depth mechanistic studies of the CAAC catalysts, which have attracted much attention for their breakthrough productivities in challenging metathesis reactions. The remarkable productivity of the CAAC catalysts is shown to originate in their resistance to decomposition of the key metallacyclobutane intermediate via b-elimination, and (to a lesser extent) in their resistance to attack by nucleophiles and Bronsted bases. Importantly, however, they are more susceptible to bimolecular decomposition. The latter behaviour, as well as their resistance to b-elimination, is traced to the strong trans influence of the CAACs relative to NHC ligands. This insight significantly advances our understanding of the fundamental properties governing both productivity and decomposition. Finally, two new catalysts are developed, building on the principle that nucleophilic stabilizing ligands should be avoided in the precatalysts. In the first of these complexes, an o-dianiline ligand is employed to stabilize the precatalyst. This flexible, H-bonding chelate serves the further purpose of accelerating macrocyclization of flexible dienes that bear polar functionalities. As its H-bonding capacity also increases its sensitivity to trace water, however, an alternative catalyst architecture was pursued. The latter consists of a dimer bearing bulky Ru-indenylidene centers, in which a dative bond from a bridging chloride affords the fifth ligand essential to stabilize the precatalyst.

Despite previous extensive study of the widely-employed ruthenium-catalysed olefin metathesis reaction, the finer mechanistic details have not been elucidated. An area that is noticeably lacking is spectroscopic exploration of the relevant complexes. In this work, organometallic ruthenium complexes of importance to olefin metathesis have been investigated using Ru K-edge X-ray absorption spectroscopy. The lowest energy feature in the Ru K-edge spectrum has been unambiguously assigned as due to Ru 4d←1s transitions. These electric-dipole-forbidden transitions are extremely sensitive to geometry. For centrosymmetric complexes, the pre-edge feature has very low intensity because it is limited by the weak electric quadrupole mechanism. By contrast, non-centrosymmetric complexes exhibit a substantial increase in pre-edge intensity because Ru 5p-4d mixing introduces electric-dipole-allowed character to the Ru 4d←1s transitions. The energy of the edge feature in the Ru K-edge spectrum corresponds to ionisation of 1s electrons and is a good indicator of the charge on the metal centre. Unexpectedly, we found that the first-generation (L = PCy₃) Grubbs precatalyst (1) has a higher 1s ionisation energy than the second-generation (L = H₂IMes) complex (2). This effect provides a compelling rationale for the unexplained differences in phosphine dissociation kinetics for complexes 1 and 2: the phosphine dissociation rate of 2 is slower than 1 because the metal centre is more electron-deficient in 2. Density functional theory calculations confirm the charge differences and offer some insight into the nature of bonding in these complexes, particularly with regard to the N-heterocyclic carbene and trialkylphosphine ligands. On the basis of these results, we propose that, for this system, the NHC ligand is a weaker σ-charge donor than the phosphine ligand, and that the NHC accepts significant π-electron density from the metal; both interactions function to reduce the electron density on the ruthenium centre. An ultimate goal is to investigate reactive species in the olefin metathesis mechanism; accordingly, we have made considerable progress toward collecting XAS data for a metallacyclobutane species, and we are pursuing methods to trap the four-coordinate intermediate in the metathesis cycle.

The olefin metathesis reaction has become one of the most powerful carbon-carbon bond forming reaction in synthetic chemistry. This work has expanded the utility of olefin metathesis in metal coordination spheres in three major directions (1) the synthesis and characterization of trans-spanning bis(pyridine)PtCl2 complexes, (2) the developme-adducts of polyacetylene (PA), and (3) the development of regioregular -adducts of poly(phenylene-vinylene) (PPV). Chapter I gives a brief overview of olefin metathesis and previous applications to organometallic substrates. Chapter II details the synthesis of pyridine ligands containing alkenyl substituents, 2-NC5H4(CH2O(CH2)nCH=CH2) (n = 1, 2), 3-NC5H4(CH2O(CH2)nCH=CH2) (n = 1-5, 8, 9), and 3,5-NC5H3(p-C6H4O(CH2)7CH=CH2)2. Metalation of the new ligands with PtCl2 affords the corresponding trans-bis(pyridine)dichloroplatinum complexes, trans-PtCl2(2-NC5H4(CH2O(CH2)nCH=CH2))2 (n = 1, 2), trans-PtCl2(3-NC5H4(CH2O(CH2)nCH=CH2))2 (n = 1-5, 8, 9), and trans-PtCl2(3,5-NC5H3(p-C6H4O(CH2)7CH=CH2))2. Ring-closing metathesefirst generation catalyst followed by hydrogenations with Pd/C afford the title complexes trans-PtCl2-(NC5H4(CH2O(CH2)2n+2OCH2)H4C5N)] (n = 1, 2), trans-PtCl2-(NC5H4(CH2O(CH2)2n+2OCH2)H4C5N)] (n = 4, 8, 9), and trans-PtCl2-(NC5H3(p-C6H4O(CH2)12O-p-C6H4)2H3C5N)]. Reactions with methylmagnesium bromide afford trans-PtCl(CH3)(3-NC5H4(CH2O(CH2)nCH=CH2))2 (n = 2, 8) and trans-PtCl(CH3-(NC5H4(CH2O(CH2)nOCH2)H4C5N)] (n = 10, 18), which feature dipolar rotators. Low temperature NMR spectra in the latter remained facile on the NMR time scale in CDFCl2 at -120 degrees Celsius. Chapter III focuses on the application of ROMP with organometallic monomers to form metal pi-adducts of polyacetylene. The new complex (n4-benzene)Cp*Ir has been synthesized, crystallographically characterized, and evaluated in the ROMP reaction. Monomers (n4-benzene)CpIr, [(n6-COT)CpRu][PF6], and (n4-COT)Fe(CO)3 were also evaluated in the ROMP reaction. ROMP of (?4-benzene)CpIr with Grubbs' first generation catalyst afforded the conductive regioregular polymer CpIr-PA. Chapter IV focuses on the synthesis of the divinyl benzene complexes [Cp*Ir(C6H4(CH=CH2)2)][BF4]2 and [Cp*Ru(C6H4(CH=CH2)2)][OTf] and their polymerization via ADMET to afford PPV systems. Treatment of divinyl benzene ed the conductive regioregular polymers [Cp*Ir-PPV][BF4]2n and [Cp*Ru-PPV][OTf]n. The photophysical properties of the new -metal adducts of PPV exhibit blue-shifts relative to typical PPVs and retain strong UV absorption.

Despite previous extensive study of the widely-employed ruthenium-catalysed olefin metathesis reaction, the finer mechanistic details have not been elucidated. An area that is noticeably lacking is spectroscopic exploration of the relevant complexes. In this work, organometallic ruthenium complexes of importance to olefin metathesis have been investigated using Ru K-edge X-ray absorption spectroscopy. The lowest energy feature in the Ru K-edge spectrum has been unambiguously assigned as due to Ru 4d←1s transitions. These electric-dipole-forbidden transitions are extremely sensitive to geometry. For centrosymmetric complexes, the pre-edge feature has very low intensity because it is limited by the weak electric quadrupole mechanism. By contrast, non-centrosymmetric complexes exhibit a substantial increase in pre-edge intensity because Ru 5p-4d mixing introduces electric-dipole-allowed character to the Ru 4d←1s transitions. The energy of the edge feature in the Ru K-edge spectrum corresponds to ionisation of 1s electrons and is a good indicator of the charge on the metal centre. Unexpectedly, we found that the first-generation (L = PCy₃) Grubbs precatalyst (1) has a higher 1s ionisation energy than the second-generation (L = H₂IMes) complex (2). This effect provides a compelling rationale for the unexplained differences in phosphine dissociation kinetics for complexes 1 and 2: the phosphine dissociation rate of 2 is slower than 1 because the metal centre is more electron-deficient in 2. Density functional theory calculations confirm the charge differences and offer some insight into the nature of bonding in these complexes, particularly with regard to the N-heterocyclic carbene and trialkylphosphine ligands. On the basis of these results, we propose that, for this system, the NHC ligand is a weaker σ-charge donor than the phosphine ligand, and that the NHC accepts significant π-electron density from the metal; both interactions function to reduce the electron density on the ruthenium centre. An ultimate goal is to investigate reactive species in the olefin metathesis mechanism; accordingly, we have made considerable progress toward collecting XAS data for a metallacyclobutane species, and we are pursuing methods to trap the four-coordinate intermediate in the metathesis cycle.

Despite previous extensive study of the widely-employed ruthenium-catalysed olefin metathesis reaction, the finer mechanistic details have not been elucidated. An area that is noticeably lacking is spectroscopic exploration of the relevant complexes. In this work, organometallic ruthenium complexes of importance to olefin metathesis have been investigated using Ru K-edge X-ray absorption spectroscopy. The lowest energy feature in the Ru K-edge spectrum has been unambiguously assigned as due to Ru 4d←1s transitions. These electric-dipole-forbidden transitions are extremely sensitive to geometry. For centrosymmetric complexes, the pre-edge feature has very low intensity because it is limited by the weak electric quadrupole mechanism. By contrast, non-centrosymmetric complexes exhibit a substantial increase in pre-edge intensity because Ru 5p-4d mixing introduces electric-dipole-allowed character to the Ru 4d←1s transitions. The energy of the edge feature in the Ru K-edge spectrum corresponds to ionisation of 1s electrons and is a good indicator of the charge on the metal centre. Unexpectedly, we found that the first-generation (L = PCy₃) Grubbs precatalyst (1) has a higher 1s ionisation energy than the second-generation (L = H₂IMes) complex (2). This effect provides a compelling rationale for the unexplained differences in phosphine dissociation kinetics for complexes 1 and 2: the phosphine dissociation rate of 2 is slower than 1 because the metal centre is more electron-deficient in 2. Density functional theory calculations confirm the charge differences and offer some insight into the nature of bonding in these complexes, particularly with regard to the N-heterocyclic carbene and trialkylphosphine ligands. On the basis of these results, we propose that, for this system, the NHC ligand is a weaker σ-charge donor than the phosphine ligand, and that the NHC accepts significant π-electron density from the metal; both interactions function to reduce the electron density on the ruthenium centre. An ultimate goal is to investigate reactive species in the olefin metathesis mechanism; accordingly, we have made considerable progress toward collecting XAS data for a metallacyclobutane species, and we are pursuing methods to trap the four-coordinate intermediate in the metathesis cycle. / Science, Faculty of / Chemistry, Department of / Graduate

Thesis advisor: Amir H. Hoveyda / Chapter One: Stereoretentive Cross-Metathesis of Trisubstituted Olefins The development of stereoretentive olefin metathesis catalysts has solved a long-standing problem in the field, allowing for trisubstituted alkenes to be synthesized in high stereochemical purity and under kinetic control. E- as well as Z-isomers of trisubstituted alkenyl halides, nitriles, and allylic alcohols can be accessed through cross-metathesis of commercially available and easily accessible alkenes. Through the use of the same strategy, macrocyclic trisubstituted alkenes have been accessed in either isomeric form through stereoretentive ring-closing metathesis of the corresponding diene starting materials. Thus, for the first time, a wide range of E- and Z-trisubstituted alkenes can be obtained selectively through olefin metathesis, regardless of the underlying thermodynamic preferences. Chapter Two: Development of Catalytic Stereoretentive Cross-Metathesis of Trisubstituted Alkenyl Bromides We have introduced a general and widely applicable strategy for the synthesis of E- and Z-trisubstituted alkenyl bromides through cross-metathesis. The reaction is applicable to terminal, disubstituted, and trisubstituted olefins bearing a variety of functional groups including alkenes with α-, or β-branches. The requisite stereodefined cross-partners, E- and Z-2-bromo-2-butene are commercially available and can be synthesized with ease in one step from abundant starting materials. This represents a notable improvement over our previous approach, where the non-halogenated alkene starting material had to be prepared through cross-coupling in high stereochemical purity to ensure high stereoretention in the subsequent cross-metathesis. Catalysts derived from Mo monoaryloxide pyrrolide complexes, some of which are commercially available, are optimal for this transformation. The applicability of the approach is underscored through the formal synthesis of phomactin A with improved overall yield and step count. Chapter Three: Total Synthesis of Ambrein We have completed a total synthesis of ambrein, a terpenoid isolated from whale secretion, a much sought perfume ingredient. The approach involved joining two fragments through formation of the central trisubstituted alkene. Our route entailed a sequence of cross-metathesis of alkenyl bromides and cross-coupling, providing access to a previously difficult-to-access trisubstituted olefin with high efficiency and selectivity. One fragment was generated from a readily accessible enantiomerically enriched compound, sclareolide, and the other from inexpensive methylcyclohexenone. The stereogenic center of the latter was established through a NHC-Cu-catalyzed enantioselective allylic substitution, which was followed by differentiation of these alkenes through site-selective epoxidation. The total synthesis is more efficient and offers a more practical route to ambrein. Chapter Four: Stereoretentive Cross-Metathesis of Trisubstituted α,β-Unsaturated Carbonyl Compounds We have developed a strategy for the synthesis of Z- and E-Trisubstituted α,β-unsaturated carbonyl compounds through stereoretentive CM involving commercially available or easily accessible alkene substrates. The method is applicable to a variety of α,β-unsaturated esters, thioesters, and acyl fluorides. Furthermore, mono-, di-, and trisubstituted alkenes can be used as starting materials. Transformations may be carried out on gram scale and, in some cases, with commercially available Mo catalysts. The utility of the catalytic approach was highlighted through synthesis of previously accessed intermediates more directly and with improved efficiency. / Thesis (PhD) — Boston College, 2022. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

As moléculas de 4-CH2X-piperidinas, X = OH (1), H (2) e Ph (3) foram investigadas como ligantes ancilares nos novos complexos [RuCl2(PPh3)2(4-CH2X-pip)] para a polimerização via metátese por abertura de anel (ROMP) de norborneno (NBE) e norbornadieno (NBD). Os complexos foram obtidos pela síntese com [RuCl2(PPh3)3] e caracterizado por análise elementar de CHN, infravermelho e RMN 31P {1H}. Os resultados sugeriram moléculas pentacoordenadas com ambos os íons cloreto e ambos os ligantes fosfinas trans-posicionados em uma geometria pirâmide de base quadrada em cada caso; a amina está no eixo axial.<br /> ROMP de NBE com 1 foram realizadas em argônio em função do volume de etildiazoacetato (EDA; 2 - 8 &micro;L), razão molar [NBE]/[Ru] (1.000 - 10.000), tempo ( 5 - 60 minutos) e temperatura (25 e 50 &deg;C) para obter a melhor condição de reação. Com 2 &micro;L de EDA a 50 &deg;C por 30 minutos e [NBE]/[Ru] = 5000, poliNBE foi quantitativamente isolado com Mw = 20,6 x 104 e IPD = 2,2. Em condições similares, rendimentos de 80 e 83% foram obtidos com 2 e 3, respectivamente (Mw = 2,4 x 104 e 0,2 x 104; IPD = 2,3 e 1,8). Os rendimentos em presença de PPh3 em excesso (20 equivalentes) foram reduzidos para 18 - 32%, enquanto na presença de amina (20 equivalentes) o complexo foi totalmente inativo. É sugerido que as reações de ROMP ocorrem quando o ligante PPh3 abandona a esfera de coordenação do Ru, e a amina em excesso envenena o catalisador devido à forte coordenação &sigma;. Experimentos com NBE em ar atmosférico resultaram em 68-77% de rendimentos, sugerindo boa resistência dos complexos à oxidação com O2.<br /> Os rendimentos para a ROMP de NBD foram de 100, 54 e 73% para 1, 2 e 3 respectivamente, utilizando as mesmas condições. Os poliNBD foram insolúveis em CHCl3. Poli[NBE-co-NBD] foram obtidos com 57 - 71% de rendimento com cada um dos complexos em presença de diferentes frações molares de comonômeros. / The molecules 4-CH2X-piperidines, X = OH (1), H (2) e Ph (3) were investigated as ancillary ligands in the new [RuCl2(PPh3)2(4-CH2X-pip)] complexes for ring opening metathesis polymerization (ROMP) of norbornene (NBE) and norbornadiene (NBD). The complexes were obtained from syntheses with [RuCl2(PPh3)3] and characterized by CHN elementary analyses, infrared and 31P-NMR. The results suggested penta-coordinated molecules with both chloro and both phosphine ligands trans-positioned in a square pyramid geometry in each case; the amine is the axial axis.<br /> ROMP of NBE with 1 were carried out in argon atmosphere in a function of ethyldiazoacetate volume (EDA; 2 - 8 &micro;L), [NBE]/[Ru] molar ration (1,000 - 5,000), time (5- 60 min) and temperature (25 and 50 &deg;C) to obtain the best reaction conditions. With 2 &micro;L of EDA at 50 &deg;C for 30 min and [NBE]/[Ru] = 5,000, polyNBE was quantitatively isolated with Mw = 20,6 x 104 e IPD = 2,2. In similar conditions, yields of 80 and 83% were obtained with 2 e 3, respectively (Mw = 2,4 x 104 and 0,2 x 104; PDI = 2,3 and 1,8). The yields in presence of PPh3 in excess (20 equivalents) were reduced to 18 - 32%, whereas in presence of amine (20 equivalents) the complexes were totally inactive. It is suggested that the ROMP reactions occurs when a PPh3 ligand leaves the Ru coordination sphere and the amine in excess poison the catalyst due to a strong &sigma;-coordination. Experiments with NBE in atmospheric of air resulted in 68-77% yields, suggesting good O2-resitances of the complexes to oxidation.<br /> The yields for ROMP of NBD were 100, 54 and 73% with 1, 2 e 3, respectively, under the same conditions. The polyNBD were insolubles in CHCl3. Poly[NBE-co-NBD] were obtained with 57 - 71% yield with either one of the complexes in presence of different comonomer molar fractions.