Copper acetylides may be the intermediate of some carbon-carbon coupling reactions. Metal acetylides were studied extensively due to their variable coordination modes. In order to mimic the structure of the intermediate, we synthesized different thioaminophosphine copper(I) complexes and tested their reactivity toward alkynes in this thesis. We introduced steric effect by controlling the carbon-chain length between second and third donor atoms of ligands and electronic effect by altering substituent groups of pheneylacetylenes. Results showed that alkynylcopper complexes were dimmeric in which the two copper(I) centers were brideged by two £g2-£b1-acetylides. Since sulfur atom of thioaminophosphine ligand was not coordinated to copper center, there was no steric effect observed in alkynylcopper complexes. No significant structural difference among alkynylcopper complexes due to electronic effect was seen either. Finally we tested reactions of thioiminophosphine copper(I) complexes toward thiophenolate. The product was a dinuclear copper(I) complex brideged by a £g2-£b1-thiophenolate ligand. Both copper(I) centers were coordinated with phosphorus, nitrogen and sulfur atoms of thioiminophosphine ligand extremely distorted tetrahedron geometry.

Nitrous oxide is a greenhouse gas produced in large quantity by several industrial processes. Efficient means of eliminating N2O are therefore of interest. The denitrification enzyme nitrous oxide reductase (N2OR), which reduces N2O to N2 and water , has recently been shown to contain an unprecedented [Cu4-µ4S] active site. Multinuclear copper sulfide compounds are known but have not been studied in the context of modeling N2OR or as N2O reduction catalysts. The synthesis of new tetranuclear [Cu4-µ4S] compounds is proposed to model the N2OR active site.The purpose of our research is to synthesize [Cu2-µ2S] complex, which original compound of [Cu4-µ4S] complex. This can be groundwork for mimicking the copper protein active site.

Hemilabile ligands attracted much attention in past thirty years because they were effectively utilized in the field of coordination chemistry and homogenous catalysis. We have synthesized four tridentate iminophosphine ligands (o-Ph2P(C6H4)-C(H)=N-(CH2)n-R, n = 2, R = SnBu, LPNS1; n = 3, R = SMe, LPNS2; n = 3, R = OMe, LPNO3; and n = 3, R = NMe2, LPNN4) and one tridentate aminophosphine ligand (o-Ph2P(C6H4)CH2N(H)(CH2)3NMe2, LPNHN5) in this work. The structures of the iminophosphine copper(I) complexes were determined by the carbon-chain length between imino-nitrogen and third donor atom, the coordination ability of the third donor atom, and the nature of the anions (i.e. its donor ability and atomic radius). An unexpected tetranuclear copper(I) iodide complex [(CuI)2(LPNN4)]2 (16) was obtained due to the larger atomic radius of iodide ion. The ligand LPNN4 displayed versatile coordination behavior after complexing with some late transition metals such as Pd(II), Ag(I), Zn(II), Cd(II). These tridentate ligands may act as PN-chelator or PNE-chelator (E = S, N¡¦). Both chelating and bridging modes were observed at the same time in Cu(I) and Ag(I) complexes. In Zn(II) complex, however, chelating by LPNN4 chelated only occurred through its N donor atoms. In term of the reactivity study of these complexes, we found that the complex [Cu(LPNN4)(CH3CN)0.2](BF4) (17) would successful react with Na(SCN), NaN3, and PhCCH/KOH to generate corresponding substitution products. However when reacted with PhCCC(O)OH/KOH, copper complexes bearing LPNN4 could not give the corresponding substituted carboxylate copper(I) product and gave the complex [Cu(CCPh)(LPNN4)]2 (18) via auto-decarboxylation instead.

Late transition metal complexes bearing nitrogen-containing ligands have many applications in biotechnology or industrial catalysis. In this thesis, we react two nitrogen-containing tridentate ligands with some late transition metal salts to yield complexes (1)-(18). Besides spectroscopic characterization, complexes (3), (5)-(7), (8), (10), (12)-(16) yielded crystal structures analyzed using X-ray single crystal diffraction. From crystal structure of complexes (3), (5)- (7), we concluded that the reaction of ligand and Cu(£L£L) salts always gave the CuLX2 products. In Ni series, structures of different coordination types were obtained by using different crystal-growing methods. Crystals obtained using diffusion method take on the form of MLX2 while different structures of complexes (8), (10) were obtained using double layer method. Judging from the result of ESI-Mass analyses, complexes (8) and (10) were both of the dimeric form[NiL1Cl(£g-Cl)]2. However complex (10) was shown by X-ray single crystal to be [NiL 2(H2O)2 Cl]Cl. This could be the hydration product from [NiL1Cl(£g-Cl)]2.

The late transition metal complexes containing sulfide ligands have trem- endous applications not only in biochemistry but also in industrial catalysis. We have successfully synthesized four different bidentate ligands, 2- (Benzylidene)benzenethiol(NS-1), 2-[2,6-(Dimethylbenzylidene)]benzenethi- ol(NS-2), 2-(2-Chloro-1-methylethylidene)benzenethiol(NS-3) and 2-(Diphe- nylphosphanyl)benzenethiol(PS), and five tridentate ligands, N-{N-[2-(Diph- enylphosphino)benzylidene]-2-sec-butylethylsulfide}(PNS-1), N-{N-[2-(Di- phenylphosphino)benzylamino]-2-sec-butylethylsulfide}(PNS-2), 2-[2-(Diph- enylphosphino)phenylsulfanylmethyl]pyridine(PSN-1), 2-[2-(Diphenylphos- phino)phenylsulfanyl]ethylamine(PSN-2) and 2-(Diphenylphosphino)phenyl- sulfanylacetonitrile(PSN-3). These ligands reacted with the late transition metal (Zn, Ag, Pd, and Ni) salts, and produced complexes 1-12. Besides their spectra, we also obtained crystal structures of complexes 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12. We found that the PNS tridentate ligands had different bonding modes in zinc, silver, palladium, and nickel complexes. For examples, in zinc complexes 1 and 2 only P and S atoms were coordinated to the metal while all P, N, and S atoms were coordinated to the Pd metal in Pd complexes. It indicated that thiolether prefers to coordinate to palladium but not to zinc in our cases. When PNS-2 went through different reaction routes, two silver complexes 4 and 5 with different coordination modes a M2L2 type dinuclear complex and a ML2 type mononuclear complex were obtained.. When reacting PNS-2 with nickel, we obtained an unique tetranuclear nickel complex 6. PSN-1 showed two different coordinate modes in complexes 8-10 while PSN-2 and silver produced a dinuclear silver complex 11 that resembled complex 4. PSN-3 coordinated to Pd ion by phosphorus and sulfide atoms. As such, we demonstrated the various coordinated modes in PNS and PSN ligands. Finally PS bidentate ligand reacted with zinc salt produced complex 7 with one oxidized ligand. The variable temperature NMR experiment was also used to probe the structural change that occurred in solution state for 3.

Late transition metal complexes bearing nitrogen-containing ligands may act as catalyst in biotechnology or industrial catalysis. Imidazole is one of the most common biofunctional ligands that play critical roles in meta1loenzymes, since the imidazole moiety of the histidyl residues often constitutes all or part of the binding sites of various transition metal centers. In this work, some new zinc(II), copper(II) and nickel(II) complexes containing the imidazolate and pyridyl moieties incorporated in the imine (ImPyI) and amine (ImPyA) ligands were obtained. Different methods of crystallization yield crystals of complexes (2), (6), (8), (9), (10), (17) and (18). Subsequent structural analyses revealed their interesting structures. In zinc(II) and nickel(II) complexes, facial isomers were isolated while none of the meridional isomers were observed. Particularly interesting is the zinc(II) complexes where two facial complexes with different geometries were identified. The mixture of the different nitrogen donor groups in the same ligand provides handy comparison of these structural variations due to the different nature of these donor groups. One tridentate ligand with bromide substitution on the imidazolate and a tetradentate ligand with an additional pyridyl group were synthesized as an extension of this work. One crystal structure of each of the corresponding metal complex bearing these ligands is also discussed here. Most metal complexes are consolidated by extensive weak hydrogen bonds among them in the crystal lattices.

This thesis is focused on the development of new pincer complex-catalyzed transformations. Optimization of the catalytic properties (fine-tuning) was directed to increase the catalytic activity as well as the chemo-, stereo- and enantioselectivity of the complexes. This was achieved by varying the heteroatoms in the terdentate pincer ligand, by changing the electronic properties of the coordinated aryl moiety and by implementing chiral functionalities in the pincer complexes. In the cross-coupling reaction of vinyl epoxides and aziridines with organoboronic acids the chemoselectivity of the reaction could be increased by employment of pincer complexes instead of commonly used Pd(0) catalysts. Furthermore, the introduction of a methoxy substituent in the aromatic subunit of the complex considerably increased the activity of the pincer complex catalyst. Fine-tuning of the enantioselectivity in electrophilic allylation reactions was achieved by using a wide variety of new BINOL- and biphenanthrol-based pincer complexes. The highest enantioselectivity (85% ee) was obtained by applying biphenanthrol-based pincer complexes. Stereoselective pincer complex-catalyzed condensation of sulfonylimines with isocyanoacetate could be achieved under mild reaction conditions. By application of chiral PCP catalysts, 2-imidazolines could be obtained with up to 86% ee. A new pincer complex-catalyzed C-H bond functionalization based reaction between organonitriles and sulfonylimines affords homoallylic amines and beta-aminonitriles in high yields. The asymmetric version of this process affords beta-aminonitriles with up to 71% ee. In the last chapter, a pincer complex-catalyzed redox coupling reaction is described. In this highly regio- and stereoselective process the integrity of the pincer catalysts is fully retained. This catalytic reaction proceeds with a high level of functional group tolerance, as allylic acetate and aryl halide functionalities are retained.

The goal of this research is to test the design constraints of active dpp-bridged RuII,RhIII (dpp = 2,3-bis(2-pyridyl)pyrazine)) supramolecular photocatalysts for water reduction to H2 and provide mechanistic insights into the catalytic cycle. Two member of a new RuII,RhIII motifs with only one Rh-'Cl bond, [(bpy)2Ru(dpp)RhCl(tpy)](PF6)4 ( bpy = 2,2'-bipyridine, tpy = 2,2':6,2"-terpyridine) and [(bpy)2Ru(dpp)RhCl(tpm)](PF6)4, (tpm = tris(1-pyrazolyl)methane), and a cis-RhCl2 model system, [(bpy)2Ru(dpp)RhCl2(bpy)](PF6)3, were prepared. This new motif was to test whether two Rh-'Cl bonds on RhIII are required for the photocatalytic water reduction. 1H NMR spectroscopic analysis of complexes prepared using deuterated ligands was used to characterize these three RuII,RhIII supramolecular complexes. Electrochemical studies suggested that replacing bpy with a tridentate ligand on RhIII shifts the RhIII/II and RhII/I reduction couples positively, which can modulate the orbital energetics of the RhIII LUMO (lowest-unoccupied molecular orbital). This substitute also changes the rate of ligand dissociation following the reduction of RhIII. In tpm and bpy systems, RhII intermediate is more stable than that in the tpy system. All three complexes were good light absorbers in the visible region and weak emitters from their emissive Ru(dπ)-'dpp(π*) 3MLCT (metal-to-ligand charge transfer) excited states at room temperature. The population of a low-lying 3MMCT (metal-to-metal charge transfer) ES (excited state) from the 3MLCT ES contributed to the weak emission, indicating an important intramolecular electron transfer process from dpp' to RhIII upon photoexcitation. The lower-lying 3MMCT excited state in the tpm and tpy systems relative to the bpy system result in a higher rate constant (ket = 2.6 x 10^7 vs 1.7 x 10^7 s-1) for intramolecular electron transfer. Spectrophotochemical analysis suggested that all three complexes were photoinitiated electron collectors capable of collecting two electrons on the RhIII center to generate the RuII,RhI species in the presence of DMA (N,N-dimethylaniline). The observed H2 production from water using [(bpy)2Ru(dpp)RhCl(tpm)](PF6)4 and [(bpy)2Ru(dpp)RhCl(tpy)](PF6)4 established that two halides on RhIII are not necessary in the dpp-bridge RuII,RhIII supramolecular photocatalytic-water-reduction system. This new discovery opens a new approach to the design of different RuII,RhIII motifs for photocatalysis. The active species for water reduction is proposed to be [(bpy)2Ru(dpp)RhICl(TL)]3+ from [(bpy)2Ru(dpp)RhCl(TL)](PF6)4 (TL (terminal ligand) = tpy or tpm) and [(bpy)2Ru(dpp)Rh(bpy)]3+ from [(bpy)2Ru(dpp)RhCl2(bpy)](PF6)3 respectively. Included here is the design and study of a RuII,RhI complex, [(bpy)2Ru(dpp)RhCl(COD)](PF6)3 (COD =1,5-cyclooctadiene) to provide more insights into the photophysical and photochemical properties of polypyridyl RuII,RhI species. Electrochemical and photophysical studies revealed a dpp-based LUMO in this RuII,RhI complex, suggesting dpp reduction upon photoexcitation. Photochemical study found that [(bpy)2Ru(dpp)RhCl(COD)](PF6)3 is an active photocatalyst for water reduction and that additional reduction(s) is (are) required after the generation of the RuII,RhI active species in the RuII,RhIII supramolecular photocatalytic H2 production system. This hypothesis was supported by the electrocatalytic behaviors of the RuII,RhIII supramolecular complexes for proton reduction. Cyclic voltammetry results in the presence of an acid suggested that the protonolysis of the RuII,RhIIH and RuII,RhIH species are electrocatalytic H2-evolution pathways. The mechanism is acid-dependent and influenced by terminal ligand. The studies of electrocatalytic proton reduction on these RuII,RhIII complexes suggested several possible intermediates involved in the photocatalytic water reduction cycle. The insights gained from this research can provide guidance in designing new type of RuII,RhIII and RuII,RhI complexes with better photocatalytic and/or electrocatalytic H2 production performance. / Ph. D.