Nitrogen ligands have been little studied with gold(I) and almost no chemistry has been described using anionic bridging nitrogen ligands. This dissertation concerns the impact of the bridging ligands amidinate, ArNHC(H)NAr, on the chemistry of gold(I) and, in particular, the effect of substituents on the molecular arrangement. The electronic vs. steric effect of the substituents on the molecular arrangement of gold(I) amidinates complexes is studied in detail. Tetra-, tri-, and dinuclear gold(I) amidinate complexes are synthesized and characterized using X-ray diffraction. Spectroscopic and electrochemical studies of the amidinate complexes are described. Catalytic studies suggest that gold amidinates and related gold nitrogen complexes are the best catalyst precursors for CO oxidation on TiO2 surface reported to date (87% conversion). The dinuclear gold(I) amidinate complex with a Auâ ¦Au distance of 2.711(3) Ã is rare. To our knowledge, there is only one other example of a symmetrical dinuclear gold(I) nitrogen complex. Oxidative-addition reactions to the dinuclear gold(I) complex, [Au2(2,6-Me2-form)2] are studied in detail and result in the formation of gold(II) complexes. The gold(II) amidinate complexes are the first formed with nitrogen ligands. The complexes are stable at room temperature. Mixed ligand tetranuclear gold(I) clusters and tetranuclear mixed Au-Ag metal clusters of pyrazolate and amidinate ligands are synthesized and characterized using Xray diffraction.

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The mechanism of carbon coupling reactions is traditionally represented in a very broad schematic. This thesis seeks to explore the mechanism of these reactions by focusing on Heck olefination. The Heck reaction has become a powerful tool in synthetic labs but the mechanism of this reaction has remained a topic of debate since the reaction's discovery. The catalytic cycle that has come to be accepted, while accurate in its own right, is not nearly as detailed as the complexity of the various stages of the Heck reaction suggest it should be. This study seeks to elucidate the nature of the oxidative addition of aryl halide to a palladium catalyst using a ligand that has been shown to have high activity in facilitating oxidative addition of aryl chlorides and bromides in other coupling reactions. This information is then compared to other studies in the field so that conclusions can be drawn about the oxidative addition. Also, selectivity studies seek to determine the nature of the migratory insertion of an olefin into the Pd-Ar bond. Again, comparison of results obtained in this study are compared to previous results so that a more definitive conclusion can be drawn about the oxidative addition.

The mechanism of carbon coupling reactions is traditionally represented in a very broad schematic. This thesis seeks to explore the mechanism of these reactions by focusing on Heck olefination. The Heck reaction has become a powerful tool in synthetic labs but the mechanism of this reaction has remained a topic of debate since the reaction's discovery. The catalytic cycle that has come to be accepted, while accurate in its own right, is not nearly as detailed as the complexity of the various stages of the Heck reaction suggest it should be. This study seeks to elucidate the nature of the oxidative addition of aryl halide to a palladium catalyst using a ligand that has been shown to have high activity in facilitating oxidative addition of aryl chlorides and bromides in other coupling reactions. This information is then compared to other studies in the field so that conclusions can be drawn about the oxidative addition. Also, selectivity studies seek to determine the nature of the migratory insertion of an olefin into the Pd-Ar bond. Again, comparison of results obtained in this study are compared to previous results so that a more definitive conclusion can be drawn about the oxidative addition.

Group 9 transition metal pincer complexes have shown tremendous utility in a variety of E-H (E = main group element) bond activation reactions. In an effort to access new types of highly reactive pincer-like transition metal complexes this research focuses on the development of new late metal complexes supported by tridentate bis(phosphino)silyl ligands of the type [?3-(2-R2PC6H4)2SiMe]- ([R-PSiP]; R = Cy, iPr). The incorporation of a strongly electron donating and highly trans-labilizing silyl group at the central anionic position may promote the formation of new coordinatively unsaturated compounds capable of enhanced reactivity. In this regard, the synthesis of coordinatively unsaturated Rh and Ir complexes supported by R-PSiP ligation and their ability to activate E-H bonds will be detailed. The synthesis of Cy-PSiP ligated Rh and Ir species and the ability to access the products of N–H bond oxidative addition with these species was investigated. Both [Cy-PSiP]Rh and [Cy-PSiP]Ir complexes were shown to form isolable complexes of the type [Cy-PSiP]M(H)(NHR) (M = Rh, R = aryl; M = Ir, R = H, aryl). However, attempts to generate such amido hydride complexes by N-H activation of the corresponding amine led to divergent reactivity, where adducts of the type [Cy-PSiP]Rh(NH2R) were obtained for Rh, while N-H bond oxidative addition was observed for Ir to form the targeted amido hydride complexes, including a rare example of ammonia N-H bond oxidative addition to form a monomeric, terminal parent amido complex that was crystallographically characterized. Due to the scarcity of transition metal complexes that are capable of N-H bond oxidative addition, a thorough investigation of the N-H bond activation mediated by [Cy-PSiP]Rh and Ir with various N-H containing substrates, including alkyl amines, hydrazine derivatives, and benzamides was initiated. Extension of this reactivity to the related diisopropylphosphino derivative [iPr-PSiP]IrI was also probed, as the resulting complexes were envisioned to be less susceptible to potential cyclometalation processes. Indeed, oxidative addition of primary alkyl amines, hydrazines, and benzamides was observed for [R-PSiP]Ir. These results comprise an unprecedented example of a metal complex that is capable of facile N-H bond activation in such a wide range of substrates, including challenging substrates such as ammonia and alkyl amines. A rare example of Rh-mediated N-H oxidative addition was also observed for the reaction of [Cy-PSiP]RhI with benzophenone hydrazone. The potential for these [R-PSiP]Ir(H)(NHR) complexes to insert unsaturated substrates was investigated, as the development of new pathways for the formation of C-N bonds via transition metal catalyzed N-H bond oxidative addition to a metal center followed by insertion of an alkene or alkyne into the M-N or M-H bond may provide a new pathway for accessing intermolecular amination reactions. Insertion chemistry attempts with various alkenes, alkynes, allenes, C=O and C?N containing compounds is described. Lastly, the synthesis of IrIII complexes of the type {[R-PSiP]IrR'}+X? (R = Cy, iPr; R’ = H, Me; X = OTf, BF4, B(C6F5)4) and their interactions with the C-H bonds of arenes and aldehydes, as well as, the Si-H bonds of hydrosilanes is detailed. The Si-H bond activation chemistry observed was typically influenced by the counter anion X. Thus, the more coordinating anions OTF and BF4 were shown to coordinate to and stabilize the highly electrophilic Si in transiently generated Ir silylene species.

Die vorliegende Arbeit befasst sich mit der Funktionalisierung von SF4 mit Übergangsmetallkomplexen des Rhodiums und Iridiums. Ein besonderer Fokus lag dabei auf Vaska-ähnlichen Fluorido-Komplexen. Ausgehend von den entsprechenden Chloridokomplexen wurde die Darstellung von trans-[M(F)(CO)(PR3)2] (M = Rh, R = Et, Ph, iPr, Cy, tBu; M = Ir, R = Et, iPr, Cy, tBu) etabliert und die Produkte umfassend charakterisiert. Aufgrund des sterischen Anspruchs der Phosphanliganden, gelingt die Insertion in eine der S−F- Bindung von SF4 nur für trans-[M(F)(CO)(PEt3)2] (M = Rh, Ir). Des Weiteren kann SF4 auch an trans-[Ir(CH3)(CO)(PEt3)2], trans-[Rh(Cl)(CNtBu)(PEt3)2] und trans-[Rh(Cl)(CS)(PEt3)2] addiert werden. Die gebildeten Trifluorosulfanylkomplexe cis,trans-[M(F)2(SF3)(CO)(PEt3)2] (M = Rh, Ir) und trans-[Rh(Cl)(F)(SF3)(CR)(PEt3)2] (R = NtBu, S) zeigen ein dynamisches Verhalten auf der NMR-Zeitskala und sind nur bei tiefen Temperaturen stabil. Durch die Umsetzung mit den Lewis-Säuren BF3 und AsF5 lassen sich die SF3-Komplexe in die entsprechenden Difluorosulfonium-Verbindungen überführen. Auch diese Komplexe besitzen eine begrenzte Stabilität und zerfallen unter Bildung von cis,cis-[M(F)(µ-F)(CO)(PEt3)2]2[A]2 (M = Rh, Ir, A = BF4, AsF6). Des Weiteren resultieren SOF-Komplexe aus der Hydrolyse des SF3-Liganden. In Umsetzung von cis,trans-[Rh(F)2(SF3)(CO)(PEt3)2] mit Ethanol bzw. Morpholin wird die Übertragung der SF3-Einheit auf das Sauerstoff- bzw. Stickstoffatom beobachtet und stellt das erste Beispiel einer Trifluorosulfanylierung dar. Zudem konnten erstmalig 103Rh-NMR-spektrokopische Studien an Rhodium-Fluorido-Komplexen durchgeführt werden. / This work illustrates the functionalization of SF4 with rhodium and iridium complexes with a special focus on Vaska-type fluorido compounds. A route to access trans-[M(F)(CO)(PR3)2] (M = Rh, R = Et, Ph, iPr, Cy, tBu; M = Ir, R = Et, iPr, Cy, tBu) was established by halogen exchange at the corresponding chlorido complexes. The treatment of the fluorido complexes with SF4 furnished SF3-complexes only in the case of trans-[M(F)(CO)(PEt3)2] (M = Rh, Ir). Therefore the steric demand of the phosphine ligands was suggested to be the key factor for the oxidative addition of this substrate. Furthermore, the insertion of trans-[Ir(CH3)(CO)(PEt3)2], trans-[Rh(Cl)(CNtBu)(PEt3)2] and trans-[Rh(Cl)(CS)(PEt3)2] into one of the S−F-bonds was achieved. A dynamic behaviour on the NMR time scale was observed for cis,trans-[M(F)2(SF3)(CO)(PEt3)2] (M = Rh, Ir) and trans-[Rh(Cl)(F)(SF3)(CR)(PEt3)2] (R = NtBu, S) and all SF3-complexes show a limited stability. Upon reaction with the Lewis-acids BF3 and AsF5 the SF3-compounds can be converted into the corresponding difluorosulfonium-complexes. Those complexes are instable as well and decompose to form cis,cis-[M(F)(µ-F)(CO)(PEt3)2]2[A]2 (M = Rh, Ir, A = BF4, AsF6), which is a unprecedented structural motif so far. In addition, treatment of the trifluorosulfanyl complexes with H2O leads to the generation of a SOF-ligand. Trifluorosulfanylation was observed in the reaction of cis,trans-[Rh(F)2(SF3)(CO)(PEt3)2] with ethanol or morpholine and showed the presence of EtOSF3 or Morpholinosulfur trifluoride (MOST), respectively. So far, a transfer of a SF3-moiety has not been observed for transitionmetal- or organosulfur trifluorides. Moreover, first studies on 103Rh-NMR-spectroscopy have been conducted containing Rhodium-fluorido-complexes.

Strong bond activation mediated by pincer ligated transiton-metal complexes has been the subject of intense study in recent years, due to its potential involvement in catalytic transformations. This dissertation has focused on the net heterolytic cleavage of B-H and B-B bonds across the N-Pd bond in a cationic (PNP)Pd fragment, the C-H oxidative addition to a (PNP)Ir center and the recent results on the C-H and C-O oxidative addition in reactions of aryl carboxylates with the (PNP)Rh fragment. Transition metal carbene and carbyne complexes are of great interest because of their role in a wide variety of catalytic reactions. Our work has resulted in the isolation of a rhodium(I) difluorocarbene. Reaction of the rhodium difluorocarbene complex with a silylium salt led to the C-F bond cleavage and the formation of a terminal fluorocarbyne complex. Reductive elimination is a critical step of cross coupling reactions. In order to examine the effect of the pincer ligand on the reductive elimination reactions from Rh(III), the first pi-accepting PNP ligand bearing pyrrolyl substituents was prepared and installed onto the rhodium center. Arylhalide (halide = Br, I) oxidative addition was achieved in the presence of donor ligands such as acetonitrile to form stable six-coordinate Rh(III) compounds. The C-O reductive elimination reactions in this system were also explored.