Polybutadiene, the homopolymer of 1,3-butadiene, is a synthetic rubber especially important in the production of tires. Industrially, it is polymerized using multi-site catalysts that do not offer significant control over molecular weight distribution resulting in polymers with poor mechanical properties. Single-site polymerization of 1,3-butadiene results in narrow molecular weight distribution and thus increased impact resistance and durability. Complexes of chromium and neodymium bearing bis-phosphinimine pincer ligands have been synthesized and studied for their behavior in 1,3-butadiene polymerization in combination with methylaluminoxane. The complexes that were active produced highly cis-1,4-polybutadiene with high molecular weight and narrow polydispersities. The co-polymerization of acrylonitrile and 1,3-butadiene with the bis-phosphinimine chromium (III) complexes and methylaluminoxane to produce nitrile-butadiene rubber was also explored. The insertion of 1,3-butadiene into nickel-methyl and nickel-hydride complexes bearing the bis-phosphinimine pincer ligands was examined using nuclear magnetic resonance spectroscopy and will also be discussed.

The results of kinetic isotope determination and computational studies on Noyori-type catalytic systems for the hydrogenation of ketones are presented. The catalysts examined include RuH2(NHCMe2CMe2NH2)(R-binap) and RuH(NHCMe2CMe2NH2)(PPh3)2. These complexes are active catalysts for ketone hydrogenation in benzene without addition of an external base. The kinetic isotope effect (KIE) for catalysis by RuH2(NHCMe2CMe2NH2)(R-binap) was determined to be 2.0 ± (0.1). The calculated KIE for the model system RuH(NHCH2CH2NH2)(PH3)2 was 1.3, which is smaller than the experimentally observed value but does not include tunneling effects. The complex OsH(NHCMe2CMe2NH2)(PPh3)2 is known to display autocatalytic behaviour when it catalyzes the hydrogenation of acetophenone in benzene. Pseudo first-order reaction conditions are obtained via addition of the product alcohol at the beginning of each kinetic experiment. The KIE determined using various combinations of deuterium-labeled gas, alcohol and ketone was found to be 1.1 ± (0.2). DFT calculations were used to explore the effect of the alcohol and the KIE. An induction period is observed at the start of the hydrogenation that is attributed to the formation of an alkoxide complex. A novel, diamine-orchestrated hydrogen-bonding network is proposed based on DFT calculations to explain how the alkoxide is converted back to the active catalyst. The tetradentate complexes trans-RuHCl[PPh2(ortho-C6H4)CH2NHCH2)]2 and RuHCl[PPh2(ortho-C6H4)CH2NHCMe2)]2 are known to be catalysts for the hydrogenation of acetophenone and benzonitrile in toluene when activated by KOtBu/KH. DFT studies were performed and a mechanism is proposed. The calculated rate limiting step for acetone hydrogenation was found to be heterolytic splitting of dihydrogen, which agrees well with experiment. The novel outer-sphere sequential hydrogenation of a CN triple bond and then a C=N double bond is proposed. A mechanism is proposed, which is supported by DFT studies, to explain the selectivity observed in the nucleophilic attack of amines or aziridines on palladium -prenyl phosphines complexes. Calculations on based on a palladium complex with two phosphorus donor ligands indicated that the observed selectivity would not be produced. Using two new model intermediates with either THF or aziridine substituted for a phosphine ligand trans to the unhindered side of the prenyl ligand did predict the experimentally observed selectivity.

Metal dithiolenes [M(S2C2R2)n] have been studied for decades because of their interesting chemical and spectroscopic properties, which are related to the unusual electronic properties of the dithiolene ligand. The ligand-based reactivity of metal bisdithiolenes [M(S2C2R2)2] toward alkenes has been proposed for use in alkene purification schemes. According to the proposal, compounds Ni(S2C2R2)2 (R=CF3,CN) react with simple alkenes to form stable S,S-interligand adducts and the alkene can be released from the adduct by reduction. We showed that Ni(S2C2(CF3)2)2 reacts with ethylene and 1-hexene to form, preferentially, S,S-intraligand adducts, which rapidly decompose to inactive metal-containing materials and dihydrodithiins. However, the product selectivity can be significantly modified so that stable S,S-interligand adducts are obtained as dominant products by adding [Ni(S2C2(CF3)2)2]- to Ni(S2C2(CF3)2)2/alkene reaction mixtures. Mechanistic implications are discussed. Next, the reactions of Pt(S2C2(CF3)2)2 with 2,3-dimethyl-1,3-butadiene are addressed. Prior to our report, only symmetry-allowed S,S-interligand adducts had been observed as products in the reactions between conjugated dienes and metal bisdithiolenes. We discovered a novel mode of diene binding, where two dienes bind to one dithiolene ligand of Pt(S2C2(CF3)2)2, in an C,S-intraligand fashion, forming a new chiral bisthioether ligand. From bisdithiolenes, the focus shifts to new mixed-ligand molybdenum trisdithiolenes [Mo(S2C2(CF3)2)2(S2C6H4) and Mo(S2C6H4)2(S2C2(CF3)2)]. These complexes rapidly and cleanly bind ethylene, in an S,S-intraligand fashion, as predicted by MO arguments. The resulting intraligand adducts are sufficiently stable to be characterized, in contrast to the nickel bisdithiolene case. The metal-chelated dihydrobenzodithiin, formed upon ethylene addition, can be substituted with a variety of donor ligands, allowing access to new types of molybdenum dithiolenes. We have recently extended these studies to catalytic reactions: Mo(S2C2(CF3)2)2(S2C6H4) was used as a catalyst to form dihydrobenzodithiins from (S2C6H4)2 and a variety of alkenes, in the first example of dithiolene-based reactivity being exploited for carbon-heteroatom bond-forming catalysis. Finally, the synthesis, characterization and redox reactivity of a new Fe2Ni bis-double-decker complex is described, demonstrating for the first time a sandwich complex of a metal bisdithiolene with both NiS2C2 rings in an η5 π-donating mode. For the radical cation, experimental and computation evidence indicates that the lone electron is delocalized over the entire molecule.

With hundreds of papers published since 2006 on frustrated Lewis pair (FLP) chemistry the development of innovative Lewis acids and Lewis bases is a quickly expanding field. This thesis is separated into two parts. The first part investigates the incorporation of tridentate ligands on ruthenium alkylidene species and their subsequent reactivity with Lewis acids and FLPs in an attempt to synthesize innovative olefin metathesis catalysts. The second part explores the use of ligands coordinated to ruthenium metal centers as a method for expanding the Lewis acid and base functionalities in the field of FLP chemistry. Ruthenium-alkylidene complexes of the general formula ((PEP-Cy)RuX2(CHPh) (E = O, NH, NMe; X = Cl, Br)) were obtained via the reaction of Grubbs 1st generation catalysts with the tridentate ancillary ligands O(CH2CH2PCy2)2 [POP-Cy], HN(CH2CH2PCy2)2 [PN(H)P-Cy] and MeN(CH2CH2PCy2)2 [PN(Me)P-Cy]. Subsequent treatment of GaX3 with these alkylidene species resulted in the formation of cationic alkylidyne-hydride complexes, ([(PEP Cy)Ru(H)(X)(CPh)][GaX4] where E = O, NH, NMe; X = Cl, Br; however, when E = NH, a mixture of alkylidyne-hydride and cationic alkylidene species was observed. Conversely, when E = NMe, alkylidyne-hydride formation was followed by transfer of the alkylidene fragment to the Me of the ligand framework. Subsequently, Ru-acetylide complexes [LRu(PPh3)2CCPh] were reacted with the B(C6F5)3 to afford the para-attacked products [LRu(PPh3)2C=C(Ph)((C6F4)B(F)(C6F5)2)] (L = Cp, Indenyl). Further studies revealed that [IndRu(PPh3)2CCPh] and ER3 (E = B, R = C6F4H; E = Al, R = C6F5) formed FLP mixtures that effected the activation of CO2 between the nucleophilic β-acetylide carbon and the Lewis acid to form [IndRu(PPh3)2C=C(Ph)C(O)O-ER3] or [IndRu(PPh3)2C=C(Ph)C(O ER3)2] when E = Al and R = C6F5. Similarly, these FLP combinations were used to activate phenylacetylene and benzaldehyde forming the species [IndRu(PPh3)2C=C(Ph)C(Ph)=C(H)(ER3)] and [IndRu(PPh3)2C=C(Ph)C(Ph)O-ER3], respectively. Lastly, the synthesis of [((Ph2PC6H4)2BCl)(η6-Ph))RuCl] was achieved via the reaction of (Ph2PC6H4)2BPh with (Ph3P)RuCl2. Subsequent halide abstraction with K[B(C6F5)4] resulted in the formation of [((Ph2PC6H4)2B)(η6-Ph))RuCl][B(C6F5)4] which was used as a carbon-based Lewis acid in adduct formation with Lewis bases to yield products of the general form [((Ph2PC6H4)2B)(η5 C6H5 o-LB))RuCl][B(C6F5)4] (LB = PPh3, PCy3, PMe3, SIMes, etc). The activation of H2 was also achieved when combinations of [((Ph2PC6H4)2B)(η6-Ph))RuCl][B(C6F5)4] and bulky phosphines were employed, resulting in the products [((Ph2PC6H4)2B)(η5 C6H6))RuCl][B(C6F5)4], [((Ph2PC6H4)2B)(η6 C6H5))RuCl][B(C6F5)4] and [R3PH][B(C6F5)4] (R = Mes, tBu, Cy). Similarly, [((Ph2PC6H4)2B)(η6-Ph))RuCl][B(C6F5)4] was used to catalytically hydrogenate sterically encumbered aldimines at room temperature with catalyst loadings as low as 1 mol% via a FLP-type mechanism.

With hundreds of papers published since 2006 on frustrated Lewis pair (FLP) chemistry the development of innovative Lewis acids and Lewis bases is a quickly expanding field. This thesis is separated into two parts. The first part investigates the incorporation of tridentate ligands on ruthenium alkylidene species and their subsequent reactivity with Lewis acids and FLPs in an attempt to synthesize innovative olefin metathesis catalysts. The second part explores the use of ligands coordinated to ruthenium metal centers as a method for expanding the Lewis acid and base functionalities in the field of FLP chemistry. Ruthenium-alkylidene complexes of the general formula ((PEP-Cy)RuX2(CHPh) (E = O, NH, NMe; X = Cl, Br)) were obtained via the reaction of Grubbs 1st generation catalysts with the tridentate ancillary ligands O(CH2CH2PCy2)2 [POP-Cy], HN(CH2CH2PCy2)2 [PN(H)P-Cy] and MeN(CH2CH2PCy2)2 [PN(Me)P-Cy]. Subsequent treatment of GaX3 with these alkylidene species resulted in the formation of cationic alkylidyne-hydride complexes, ([(PEP Cy)Ru(H)(X)(CPh)][GaX4] where E = O, NH, NMe; X = Cl, Br; however, when E = NH, a mixture of alkylidyne-hydride and cationic alkylidene species was observed. Conversely, when E = NMe, alkylidyne-hydride formation was followed by transfer of the alkylidene fragment to the Me of the ligand framework. Subsequently, Ru-acetylide complexes [LRu(PPh3)2CCPh] were reacted with the B(C6F5)3 to afford the para-attacked products [LRu(PPh3)2C=C(Ph)((C6F4)B(F)(C6F5)2)] (L = Cp, Indenyl). Further studies revealed that [IndRu(PPh3)2CCPh] and ER3 (E = B, R = C6F4H; E = Al, R = C6F5) formed FLP mixtures that effected the activation of CO2 between the nucleophilic β-acetylide carbon and the Lewis acid to form [IndRu(PPh3)2C=C(Ph)C(O)O-ER3] or [IndRu(PPh3)2C=C(Ph)C(O ER3)2] when E = Al and R = C6F5. Similarly, these FLP combinations were used to activate phenylacetylene and benzaldehyde forming the species [IndRu(PPh3)2C=C(Ph)C(Ph)=C(H)(ER3)] and [IndRu(PPh3)2C=C(Ph)C(Ph)O-ER3], respectively. Lastly, the synthesis of [((Ph2PC6H4)2BCl)(η6-Ph))RuCl] was achieved via the reaction of (Ph2PC6H4)2BPh with (Ph3P)RuCl2. Subsequent halide abstraction with K[B(C6F5)4] resulted in the formation of [((Ph2PC6H4)2B)(η6-Ph))RuCl][B(C6F5)4] which was used as a carbon-based Lewis acid in adduct formation with Lewis bases to yield products of the general form [((Ph2PC6H4)2B)(η5 C6H5 o-LB))RuCl][B(C6F5)4] (LB = PPh3, PCy3, PMe3, SIMes, etc). The activation of H2 was also achieved when combinations of [((Ph2PC6H4)2B)(η6-Ph))RuCl][B(C6F5)4] and bulky phosphines were employed, resulting in the products [((Ph2PC6H4)2B)(η5 C6H6))RuCl][B(C6F5)4], [((Ph2PC6H4)2B)(η6 C6H5))RuCl][B(C6F5)4] and [R3PH][B(C6F5)4] (R = Mes, tBu, Cy). Similarly, [((Ph2PC6H4)2B)(η6-Ph))RuCl][B(C6F5)4] was used to catalytically hydrogenate sterically encumbered aldimines at room temperature with catalyst loadings as low as 1 mol% via a FLP-type mechanism.

This thesis examines the use of anionic nitrogen chelate ligands in coordination-driven self-assembly and small molecule activation. The two classes of anionic nitrogen chelate ligands that were explored are β-diiminate and 4,5-diazafluorenide derivatives. Chapter 2 deals with Pd β-diiminate chemistry. Chloro-bridged dimers served as versatile starting materials, and their reactivity toward pyridine and arylboronic acids was explored. An unusual transmetallation reaction with arylboronic acids triggered the self-assembly of tetrapallada-macrocycles. The formation of the self-assembled tetrapallada-macrocycles is through the generation of new Pd-C bonds. Chapter 3 deals with 4,5-diazafluorenide as an actor ligand in CO2 activation. A reversible formal insertion of CO2 into a remote ligand C-H bond was discovered. A variety of spectator metal centres were used to tune the reactivity of the actor ligand toward CO2. The spectator metal centre could even be replaced entirely with an organic group allowing for the first metal-free reversible tandem CO2 and C-H activation. Chapter 4 deals with the reactivity of dinuclear Rh 4,5-diazafluorenide-9-carboxylate complexes with dihydrogen in an attempt to reduce the trapped CO2 moiety. A series of stepwise stoichiometric reactions with H2, NMR experiments at low temperatures with added PPh3 or CO2, along with 13C-labelling experiments were conducted in an attempt to identify the products of this reaction and gain some mechanistic insight. Chapter 5 deals with using ambidentate 4,5-diazafluorene derivatives to synthesize linkage isomers, heterobimetallic complexes, and self-assembled macrocycles. The synthesis a new ligand family, 3,6-substituted 4,5-diazafluorene ligands is presented, along with coordination chemistry towards a {RuCp*}+ fragment. Finally in Chapter 6 the coordination chemistry of 3,6-diaryl substituted 4,5-diazafluorene derivatives was explored with the goal of generating low-coordinate species for the activation of small molecules, especially N2. The synthesis of the first trialkylborohydride complex of vanadium is presented.

Several new late transition metal complexes containing P-O and P-N ligands derived from 2-dicyclohexylphosphinoacetaldehyde were synthesized. A facile one-pot template method is used for the synthesis of P-N complexes, where the phosphine aldehyde and amine can undergo a condensation reaction to form a phosphine-imine metal complex in the presence of a metal precursor. Metal complexes with phosphino-enolate, imine, and oxime ligands are synthesized. Ni(II), Pt(II), Rh(I) and Ir(I) metal centres were investigated. The Rh(I) and Ir(I) complexes contain a 1,5-cyclooctadiene ligand, thus resembling Crabtree’s hydrogenation catalyst [Ir(COD)(py)(PCy3)][PF6]. These complexes are also active catalysts for olefin hydrogenation. Furthermore, the synthesis of a new chiral amine functionalized NHC ligand is explored, which has potential applications as a ligand in the metal-catalyzed enantioselective hydrogenation of polar bonds. This ligand is inspired by previous achiral hydrogenation catalysts reported by Morris et al. that displayed high activity for a variety of unsaturated substrates.

Doctor of Philosophy / Department of Chemistry / Kenneth J. Klabunde / A new approach to synthesize nanosized strontium titanate (SrTiO3) and barium titanate (BaTiO3) has been developed. Nanocrystals of mixed metal oxide were synthesized by a modified aerogel procedure from alkoxides. The textural and surface characteristic properties were studied by nitrogen BET analysis, transmission electron microscopy, and powder XRD. The crystallite sizes of aerogel prepared powders can vary from 6 to 25 nm by the use of different solvents. A mixture of ethanol and toluene was found to be the best binary solvent for supercritical drying, which produced a SrTiO3 sample with a surface area of 159 m2/g and an average crystallite size of 8 nm, and a BaTiO3 sample with a surface area of 175 m2/g and an average crystallite size of 6 nm. These titanates have been studied for photocatalytic oxidation of volatile organic compounds and acetaldehyde (CH3CHO) in particular. The big band gaps of the bulk (3.2 eV for SrTiO3 and 3.1 eV for BaTiO3) limit their application to a UV light region only. The modification of titanates by doping with transition metal ions (partial substitution of Ti ions with metal ions) creates a valence band or electron donor level inside of the band gap, narrows it, and increases the visible light absorption. The enhanced adsorption of visible light was achieved by the synthesis of nanosized SrTiO3 and BaTiO3 by incorporating Cr ions during the modified aerogel procedure. Gaseous acetaldehyde photooxidation has been studied on pure SrTiO3 and BaTiO3, and on chromium doped Cr-SrTiO3 and Cr-BaTiO3 under UV and visible light irradiation, and compared with the photoactivity of P25 TiO2. SrTiO3 doped with antimony/chromium shows absorption in visible light and show photocatalytic activity for CH3CHO oxidation. The reason for the codoping of SrTiO3 with Sb/Cr was to maintain the charge balance and to suppress oxygen defects in the lattice. This photocatalyst shows high photoactivity under visible light irradiation even after several continuous runs. The photoactivity under visible and UV light irradiation was almost identical for the Sb/Cr-SrTiO3 photocatalyst. Dielectric properties of aerogel prepared barium titanate samples have being studied and the bulk resistance values of AP-BaTiO3 were significantly lower than that of commercial BaTiO3, by several orders of magnitude.

Doctor of Philosophy / Department of Chemistry / Christer B. Aakeroy / The directed-assembly of small molecular building-blocks into discrete supermolecules or extended networks through non-covalent intermolecular interactions is an on-going challenge in the field of crystal engineering. This synthetic challenge may be overcome by identifying or establishing a hierarchy of intermolecular interactions which, in turn, may facilitate a modular supramolecular assembly process producing final products in high yields. A family of three 3-pyridine/amino-pyrimidine supramolecular reactants (SR’s) was prepared and allowed to react with aromatic carboxylic acids producing nine 1:1 molecular co-crystals and four 1:1 ionic salts through heteromeric O-H···N/N-H···O or charge-assisted N–H+···O-/N–H···O- hydrogen bonds with the amino-pyrimidine binding site. We introduced a Q-value, based on AM1 calculations, to show that the amino-pyrimidine moiety is a superior hydrogen-bond acceptor for an incoming carboxylic acid. The amino-pyrimidine/carboxylic acid synthon resulted 13/13 times (100 % yield) even in the presence of other potentially disruptive intermolecular interactions. However, reacting a 4-pyridine/amino-pyrimidine SR and a carboxylic acid in a 1:2 ratio, resulted in structures containing both acid/amino-pyrimidine and acid/pyridine synthons. The same family of pyridine/amino-pyrimidine SR’s were allowed to react with halogentated benzoic acids in which the amino-pyrimidine/carboxylic acid synthon formed 7/7 times (100 % yield) and halogen bonds (N···I or N···Br) extended the SR/acid dimers into polymeric networks 4/7 times (57 %). These results were rationalized through a hierarchial view of intermolecular interactions consisting of hydrogen and halogen bonds. Four bifunctional 3-pyridine/amino-pyrimidine or amino-pyridine SR’s were reacted with neutral metal complexes producing thirteen crystal structures in which the pyridyl moiety coordinates to the metal center 13/13 times (100 % yield) and amino-pyrimidine···amino-pyrimidine hydrogen bonds link the neighboring metal-ligand complexes 10/13 times (77 % yield) into 1-D or 2-D extended architectures. Finally, we synthesized and characterized a series of tetra-substituted hydrogen bond donor and acceptor functionalized, i.e. pyridyl, amino-pyridine, carboxylic acid, resorcinarene-based cavitands forming deep-walled cavitands through amino-pyridine···carboxylic acid heteromeric synthons and a heterodimeric molecular capsule through pyridyl···carboxylic acid hydrogen bonds. The heterodimeric capsule is only one of three, of its type, characterized crystallographically.

Doctor of Philosophy / Department of Chemistry / Eric A. Maatta / Polyoxometalates have attracted much attention over the last few decades and have been studied in a wide variety of fields such as catalysis, medicine, imaging, photochromism, and magnetic materials. While many of these systems are easy to prepare, the ability to functionalize polyoxometalates is an ongoing challenge. Two approaches used to functionalize polyoxometalates involve insertion of metal fragments into a lacunary polyoxometalate or the direct replacement of terminal oxo ligands with the isoelectronic organoimido ligand. This process has been proven successful in many cases and with a wide variety of organoimido compounds. One of our group’s goals has been to synthesize a functionalized hexamolybdate species that is capable of metal coordination. However, previous results have been hindered because the electron withdrawing effect of the cluster is transmitted to the metal binding sites. In order to combat the electron withdrawing effect of the cluster, 4-amino piperidine dithiocarbamate ligands, which have no conjugation in the ring and are capable of metal binding, have been synthesized and characterized. A series of transition metal complexes have been made and a single crystal has been grown of a nickel(II) complex. Attempts to attach these species to clusters are described. Imido hexamolybdate clusters have been functionalized with styryl and iodophenyl groups. The styrene functionalized hexamolybdate was copolymerized with 4- chloromethylstyrene in moderate yields. This copolymer has the capabilities for further substitution at the chloromethyl group. The iodophenyl functionalized hexamolybdate was fully characterized including a single-crystal X-ray structural determination. This functionalized hexamolybdate can be used in carbon-carbon bond formation through coupling reactions. A chromium(V) nitrido polyoxometalate has been synthesized from a lacunary Keggin precursor and characterized. This nitrido species shows promise as a nitrogen transfer agent. Likewise, this nitrido species could be an entry point to other derivatives through reactions with various nucleophiles and electrophiles.