Academic literature on the topic 'Metal sandwich compounds'

Density functional theory shows the lowest energy bis(butadiene)metal structures (C₄H₆)₂M (M = Ti to Ni) to have a staggered orientation of the two butadiene ligands corresponding to a tetrahedral coordination of the central metal atom.

The pnictide halides La2I2P, La2I2As, La2I2Sb, La2Br2P and Y2Br2P have been synthesized from lanthanum and yttrium, red phosphorus, arsenic, and antimony, respectively, and the corresponding metal trihalides. Their structures contain close-packed metal atom double layers with pnicogen atoms in the octahedral voids. These layers are sandwiched by halogen atom layers. The compounds crystallize in the trigonal 1T-type with one sandwich-like layer per unit cell, or in the rhombohedral 3R-type with three layers per unit cell. Polytypism and twinning have been observed. For 3R-La2I2P, conductivity measurements have shown metallic behaviour

Ethyl group determined the toxicity of pyridylbenzimidazole Ir(iii) compounds and exchange of the group with sulfonate led to diminishing of the antibacterial activity. Increasing the metal content per complex, 3, gave rise to a compound with no toxicity.

The present work relates to the synthesis and spectral properties of erbium and sandwich type metal complexes containing tetraanthraquinoporphyrazine as well as phthalocyanine fragments. By reacting tetraanthrachinoporphirazine erbium (lutetium) acetate with excess phthalonitrile, 4-chloro, 4-bromophthalonitrile and unsubstituted phthalonitrile, sandwich-type complexes of an unsymmetrical structure were obtained. The compounds were extracted from the reaction mixture with a suitable organic solvent (DMF or toluene) and purified by prolonged extraction of impurities with acetone in a Soxlet apparatus. Final purification was carried out by column chromatography. The obtained complexes are green solids having solubility in DMSO, DMF, and concentrated sulfuric acid. The composition and structure of complexes were confirmed by elemental analysis, IR and electron spectroscopy. Influence of chemical structure of new "sandwich" compounds on their spectral properties and possible applications has been investigated. In particular, when analyzing the electron absorption spectra, it was found that the metal, the nature of the substituents in the tetraanthraquinone moiety and the replacement of hydrogen atoms with halogen atoms in the phthalocyanine moiety slightly affect the nature and position of the absorption maxima. Studies have been carried out on the coloristic properties of synthesized organosoluble metal complexes erbium and lutetium. The compounds have been found to exhibit the properties of pigments and dyes for polymeric materials such as polystyrene and polyethylene. The temperature parameters of thermal oxidative degradation were determined and it was found that the obtained "sandwich" type phthalocyanines have high resistance to thermal oxidative degradation.

π–π interaction-linked extension in the perpendicular direction to the monomers and corresponding effect on nonlinear optic properties have been clearly disclosed over the multiple-decker sandwich-type phthalocyaninato metal compounds.

With the aim of finding alternative reaction media for the synthesis of subvalent main group and transition metal cluster compounds, traditionally made through solid state reactions or in superacidic media, different alternative reaction media have been explored in this work. Room-temperature ionic liquids are amongst the more unconventional reaction media used. The syntheses performed have been aimed at both anionic and cationic cluster and the main tools used for characterization have been different X-ray diffraction and spectroscopic techniques. Selected ionic liquids have along with dichloromethane been shown to work as alternative reaction media for room temperature synthesis of the Bi5[GaCl4]3 salt. The salt containing the subvalent naked bismuth polycation Bi5 3+ was isolated from reduction reactions of BiCl3 in Ga/GaCl3-dichloromethane respectively Ga/GaCl3-ioinc liquid media. Three different classes of ionic liquids based on phosphonium-, imidazolium- and pyrrolidinium- salts have been used in synthesis. Homopolyatomic clusters from the lighter Group 15 element arsenic have also been studied. Solutions from the oxidative and reductive reaction routes of arsenic and AsCl3 in Lewis acidic toluene media were studied by EXAFS spectroscopy. The results were evaluated using molecular dynamics simulations of arsenic clusters. A discussion on how the calculated As4 cluster model relates to the experimental data resulted from this study. In terms of homopolyatomic anionic clusters the [K+(2,2,2-crypt)]2Ge9 2- compound containing the naked Ge9 2- anionic cluster has been isolated. The crystallographic investigation of [K+(2,2,2-crypt)]2Ge9 2- shows Zintl cluster anion Ge9 2- to be tricapped trigonal-prismatic with a symmetry very close to D3h. A chemical bonding analysis reveals two local minima of D3h symmetry and the cluster interaction scheme to be based on highly delocalised bonding. Ligand supported transition metal clusters from tungsten and palladium have also been prepared. Reduction of WCl6 in a reaction mixture of ionic liquid and co-solvent toluene resulted in tritungsten decachloride; W3Cl10(MeCN)3, being formed. Furthermore, palladium sandwich compounds; [Pd2(Ga2Cl7)(C7H8)2], [Pd2(GaCl4)(C9H12)2]∙C9H12 and [Pd2(Ga2Cl7)(C6H5Cl)2] have been prepared using GaCl3-arene reaction media.

QC 20121212

Thesis (Ph. D.)--Ohio State University, 2005.
Title from first page of PDF file. Document formatted into pages; contains xxxi, 309 p.; also includes graphics Includes bibliographical references. Available online via OhioLINK's ETD Center

This thesis expands the scope for using the permethylpentalene ligand and its precursors in the synthesis of organometallic complexes. Chapter one begins with a brief review of linked metallocenes, with which multimetallic compounds bridged by pentalene ligands have often been compared, followed by a comprehensive review of the routes used to make pentalenes and substituted pentalenes. Organometallic compounds of pentalenes are introduced, with a focus on bimetallic systems. Chapter two explores the diversification of substituents added to the permethylpentalene (Pn*) precursor WeissH₄, to include ethyl and isopropyl groups. Low-symmetry mono-, di-, tri- and tetraalkylated products are formed, eight such organic molecules have been identified by NMR spectroscopy, and two characterised crystallographically. It has been demonstrated that subsequent hydrolysis and decarboxylation of two of these products produces low-symmetry alkylpentalene precursors. The chapter concludes with discussions on the selectivity exhibited in these reactions, and the assignment of stereochemistry. Chapter three describes the synthesis of the first homoleptic double metallocene complex of iron. Fe₂Pn*₂ has been characterised by X ray diffraction, and cyclic voltammetry studies demonstrate four accessible oxidation states (-1, 0, +1, +2). Magnetic measurements in the solid and solution state reveal an unusual triplet configuration, and DFT calculations indicate the origin of a high magnetic moment likely resides in unquenched orbital angular momentum contributions from SOMOs which have metal d character. Fe₂Pn*₂ is EPR silent at 5, 40, and 300 K both in solution and the solid state, suggesting a large zero-field splitting parameter. The reaction of the di-iron complex with carbon monoxide, ethylene and H2 is reported; the bimetallic CO adduct, Fe₂(μ η⁵,η³ Pn*)(μ η⁵,η¹ Pn*)(CO)₂, has been crystallographically characterised, and contains a highly distorted allylic bonding motif, which to the author’s knowledge is believed to be unique among iron complexes. Chapter four discusses the interaction of the bidentate Pn* ligand in anti bimetallic fused metallocenes. A new ligand exchange route has been developed to access the complexes (MCp)₂Pn* (M = Co, Ni), and the isostructural complexes (MCp*)₂Pn* have been made for M = Fe, Co, Ni by salt metathesis reactions. All five complexes have been characterised by single crystal X-ray crystallography, and have diamagnetic ground states in solution in common with their Pn bridged analogues. Variable temperature NMR studies reveal a spin-equilibrium between S = 0 and S = 1 in the dinickel complexes. DFT calculations reproduce the spin states found, and suggest the distortion towards η³ coordination observed on crossing from Fe, to Co, to Ni, results from population of orbitals with M―bridgehead antibonding character. The electronic structures show it is important to draw comparisons between isoelectronic linked metallocenes. Electrochemical studies on the diiron, dicobalt, and (NiCp)₂Pn* complexes reveal at least three redox events for each. Chapter five documents the successful synthesis and characterisation of monometallic complexes of iron and manganese with Pn*H ligands. The isostructural complexes Fe(Pn*H)₂ and Mn(Pn*H)₂ can have been characterised crystallographically, and are potential precursors for accessing heterometallic, and multimetallic complexes. Mn(Pn*H)₂ is a rare example of a manganese sandwich compound and magnetic studies on a single isomer in the solution and solid states suggest it adopts intermediate spin states of S = 2 in solution, and S = 3/2 in the solid state. Chapter six gives experimental details for all syntheses and studies described in the preceding chapters. Chapter seven provides characterising data for all new compounds. Fitting data for VT NMR and SQUID studies are provided in the appendix at the end of this thesis. Crystallographic data in the form of .cif files, DFT output files, and raw SQUID data, can be found in the electronic appendix.

Wang, Yang.
"October 2011."
Thesis (M.Phil.)--Chinese University of Hong Kong, 2012.
Includes bibliographical references (leaves 87-92).
Abstracts in English and Chinese.
Acknowledgement --- p.I
Abstract (in English) --- p.III
Abstract (in Chinese) --- p.IV
Abbreviation --- p.V
List of Compounds --- p.VI
List of Figures --- p.IX
Contents --- p.X
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Synthesis and Structure of Half-Sandwich Group 4 Metallocarboranes Containing the Dicarbollyl Ligand --- p.2
Chapter 1.2 --- Half-Sandwich Group 4 Metallacarboranes Catalyzed Reactions --- p.20
Chapter 1.2.1 --- Polymerization of Olefins --- p.20
Chapter 1.2.2 --- Catalytic Dimerization and Hydrogenation of Alkynes --- p.22
Chapter 1.2.3 --- Catalytic Addition of Amines to Carbodiimides --- p.23
Chapter 1.2.4 --- Catalytic Transamination of Guanidines --- p.24
Chapter 1.2.5 --- Catalytic Synthesis of A^-Heterocycles --- p.25
Chapter 1.3 --- Research Objectives of This Thesis --- p.26
Chapter Chapter 2 --- Half-Sandwich Group 4 Metallacarborane Monoamindes --- p.27
Chapter 2.1 --- Introduction --- p.27
Chapter 2.2 --- Synthesis of Dicarbollyl Ligands Bearing Functional Side Arms --- p.27
Chapter 2.3 --- Synthesis and Characterization of Half-Sandwich Group 4 Metallacarborane Monoamindes --- p.33
Chapter 2.4 --- Summary --- p.43
Chapter Chapter 3 --- Synthesis of 2-Aminoimidazoles Catalyzed by Half-Sandwich Titanacarborane Monoamide --- p.44
Chapter 3.1 --- Introduction --- p.45
Chapter 3.2 --- Known Methods for the Synthesis of 2-Aminoimidazole --- p.44
Chapter 3.2.1 --- Condensations Methods --- p.44
Chapter 3.2.2 --- Direct Introduction of N at C2 Position --- p.46
Chapter 3.2.3 --- Heterocyclic Exchange Reactions --- p.47
Chapter 3.2.4 --- Transition Metal Catalyzed Reactions --- p.48
Chapter 3.3 --- Results and Discussion --- p.49
Chapter 3.3.1 --- Synthesis of Propargy 1 Amines --- p.49
Chapter 3.3.2 --- Synthesis and Characterization of 2-Aminoimidazoles --- p.50
Chapter 3.3.3 --- Proposed Reaction Mechanism --- p.55
Chapter 3.4 --- Summary --- p.57
Chapter Chapter 4 --- Conclusion --- p.59
Chapter Chapter 5 --- Experimental Section --- p.61
References --- p.87
Appendix
Chapter I. --- Publication Based on the Research Findings --- p.93
Chapter II. --- Crystal Data and Summary of Data Collection and Refinement --- p.94
Chapter III. --- X-ray crystallographic data in CIF (electronic form)

This thesis reports the theoretical investigations aimed at understanding the structure, stability and properties of a few inorganic compounds. The first chapter presents an introductory overview of the theories used to solve the questions addressed in the thesis. A brief discussion of the work is also presented here. The second chapter deals with electron reservoirs which have been one of the basic motifs of single-electron device. Mononuclear vinylidene complexes of type Mn(C5H4R’)(R” 2 PCH2CH2PR "2)= C = C(R1)(H) were synthesized and reported [Venkatesan et al, Organometallics 25, 5190 (2006)] as potential electron reservoirs capable of storing and releasing electrons in a reversible fashion. These compounds have been of great interest because their red-ox chemistry (reversible oxidative coupling and reductive decoupling) is governed by the C - C bond. However slow oxidation of the mononuclear vinylidene complexes leads to undesired product. In our model compound Mn(C5H5)(PH3)2 = C = C(R1)(H), we substituted the cyclopentadienyl moiety by isolobal dianionic dicarbollyl ligand Dcab2- (C2B9H2-11 ). This simple substitution could reduce the production of undesired product. Calculations of vertical detachment energy, thermodynamic feasibility and molecular orbital analysis showed that this substitution was thermodynamically feasible and led to easy oxidation and dimerization of the parent compound accompanied with better reversibility of the reaction. The effect of substituents (R = H,Me,Ph) on Cβ atom of our model system was also analyzed. The substituent on β carbon had a great effect on the stability and reactivity of these complexes. Our comparative study between Mn(C5H5)(PH3)2 = C = C(R)(H) and Mn(Dcab)(PH3)2 = C = C(R)(H)−1 (where R = H,Me,Ph) predicted the latter to be a more potential electronic reservoir. Gas-phase observations on MAl 4- (M = Li, Na, Cu) and Li3Al-4 coupled with computations led to the conclusion that Al42− [Boldyrev and Wang et al, Science 291, 859 (2001)] is “aromatic” while Al44- is “antiaromatic” [Boldyrev and Wang et al, Science 300, 522 (2003)]. It has been reported by Pati et al [J. Am. Chem. Soc. 125, 3496 (2005)] that co-ordination with a transition metal can stabilize the “antiaromatic” Al4Li4. In the first section of chapter three, it has been reported that Al4Li4 can also be stabilized by capping it with main group element like C and its isoelectronic species BH. Calculations of binding energy, nuclear independent chemical shift (NICS), energy decomposition analysis and molecular orbital analysis supported the capping induced stability, reduction of bond length alternation and increase of aromaticity of these BH/C capped Al4Li4 systems. The interaction between px and py orbitals of BH/C and the HOMO and LUMO of Al4Li4 was responsible for such stabilization. Calculations suggested that capping might introduce fluxionality in the molecule at room temperature. Al has valence electronic configuration of s2p1 and Al42− has been shown to have multiple aromaticity [Boldyrev and Wang et al, Science 291, 859 (2001)]. Analogy between electronic configuration s2pof Al and d1sof Sc/Y prompted us to explore the aromaticity of M42− clusters (M = Sc, Y ) which have been described in the second section of chapter three. Different geometries of M42− clusters (M = Sc, Y ) were explored, and the planar butterfly-like D2h geometry (two fused triangles) was found to be the most stable isomer. This is unlike the case of Al42− where D4h isomer was the most stable one as reported in the literature. In D2h geometry of M42− clusters (M = Sc, Y ), significant electron delocalization in each wing of the butterfly indicated fused d aromaticity. Atomization energy and chemical hardness supported the preference of D2h geometry over the D4h geometry. Molecular orbital analysis showed that the d-electrons were delocalized in each triangle of D2h geometry. Our interest in the search of new kinds of binuclear sandwich compounds led us to consider sandwiched metal dimers CB5H6M - MCB5H6 (M = Si, Ge, Sn) which are at the minima in the potential energy hypersurface with a characteristic M - M single bond. This work has been described in the first section of chapter four. The NBO analysis and the M - M distances ( ˚A) (2.3, 2.44 and 2.81 for M= Si, Ge, Sn respectively) indicated substantial M - M bonding. Consecutive substitution of two boron atoms in B7H7−2 by M (Si, Ge, Sn) and carbon respectively led to neutral MCB5H7, where M - H bond bent towards the carbon side of the five membered ring. Dehydrogenation of two MCB5H7 might lead to our desired CB5H6M - MCB5H6 where similar bending of M -M bond has been observed. The bending of M - M bond in CB5H6M -MCB5H6 was more than the M - H bending in MCB5H7. Molecular orbital analysis has been done to understand the bending. Larger M - M bending observed in CB5H6M - MCB5H6 in comparison to M - H bending observed in MCB5H7 was suspected to be favored by stabilization of one of the M - M π bonding MO’s. Preference of M to occupy the apex of pentagonal skeleton of MCB5H7 over its icosahedral analogue MCB10H11 has been observed. Structures of sandwiched binuclear L- M – M - L where M = Ti, Zr and L = Cp, C3B3H6 were also investigated as described in second section of chapter four. We found that these compounds having bent geometry with short M - M distance (1.87˚A for M=Ti and 2.29˚A for M=Zr) lie at the minima in the potential energy hypersurface. Bending from the linear geometry led to the stabilization of M - L antibonding interaction in L - M – M - L. Molecular orbital analysis, NBO calculations, Wiberg bond index and charge analysis suggested M2+ unit to be embedded in between two L’s in L - M – M - L. Molecules that have the ability to perform interesting mechanical motions have always been of great interest. Umbrella inversion of ammonia is one of the most interesting and well studied phenomena. This study has led to the development of the MASER. The possibility of inversion of the molecule C9H9−Li+ by the movement of Li+ through the C9H9−ring was studied earlier [Das et al, Chem. Phys. Lett. 365, 320 (2002)]. In the fifth chapter theoretical investigation on a B12 cluster has been reported, which could exhibit a through ring umbrella inversion. Calculations showed that a part of the molecule, consisting of a three membered boron ring could invert through the rest, viz., a nine membered boron ring. Using a simple model, the double well potential for the motion was calculated. The barrier for inversion was found to be 4.31 kcal/mol. The vibrational levels and tunneling splitting were calculated using this potential. It was found that the vibrational excitation to the v = 17 level caused large amplitude “inversion oscillation” of the molecule. After considering the tunneling effect, inversion rate at 298K was calculated by using transition state theory and was found to be 1.17 x 1010/s. Finally, in the last chapter the main results of the thesis have been summarized.

This thesis reports the theoretical investigations aimed at understanding the structure, stability and properties of a few inorganic compounds. The first chapter presents an introductory overview of the theories used to solve the questions addressed in the thesis. A brief discussion of the work is also presented here. The second chapter deals with electron reservoirs which have been one of the basic motifs of single-electron device. Mononuclear vinylidene complexes of type Mn(C5H4R’)(R” 2 PCH2CH2PR "2)= C = C(R1)(H) were synthesized and reported [Venkatesan et al, Organometallics 25, 5190 (2006)] as potential electron reservoirs capable of storing and releasing electrons in a reversible fashion. These compounds have been of great interest because their red-ox chemistry (reversible oxidative coupling and reductive decoupling) is governed by the C - C bond. However slow oxidation of the mononuclear vinylidene complexes leads to undesired product. In our model compound Mn(C5H5)(PH3)2 = C = C(R1)(H), we substituted the cyclopentadienyl moiety by isolobal dianionic dicarbollyl ligand Dcab2- (C2B9H2-11 ). This simple substitution could reduce the production of undesired product. Calculations of vertical detachment energy, thermodynamic feasibility and molecular orbital analysis showed that this substitution was thermodynamically feasible and led to easy oxidation and dimerization of the parent compound accompanied with better reversibility of the reaction. The effect of substituents (R = H,Me,Ph) on Cβ atom of our model system was also analyzed. The substituent on β carbon had a great effect on the stability and reactivity of these complexes. Our comparative study between Mn(C5H5)(PH3)2 = C = C(R)(H) and Mn(Dcab)(PH3)2 = C = C(R)(H)−1 (where R = H,Me,Ph) predicted the latter to be a more potential electronic reservoir. Gas-phase observations on MAl 4- (M = Li, Na, Cu) and Li3Al-4 coupled with computations led to the conclusion that Al42− [Boldyrev and Wang et al, Science 291, 859 (2001)] is “aromatic” while Al44- is “antiaromatic” [Boldyrev and Wang et al, Science 300, 522 (2003)]. It has been reported by Pati et al [J. Am. Chem. Soc. 125, 3496 (2005)] that co-ordination with a transition metal can stabilize the “antiaromatic” Al4Li4. In the first section of chapter three, it has been reported that Al4Li4 can also be stabilized by capping it with main group element like C and its isoelectronic species BH. Calculations of binding energy, nuclear independent chemical shift (NICS), energy decomposition analysis and molecular orbital analysis supported the capping induced stability, reduction of bond length alternation and increase of aromaticity of these BH/C capped Al4Li4 systems. The interaction between px and py orbitals of BH/C and the HOMO and LUMO of Al4Li4 was responsible for such stabilization. Calculations suggested that capping might introduce fluxionality in the molecule at room temperature. Al has valence electronic configuration of s2p1 and Al42− has been shown to have multiple aromaticity [Boldyrev and Wang et al, Science 291, 859 (2001)]. Analogy between electronic configuration s2pof Al and d1sof Sc/Y prompted us to explore the aromaticity of M42− clusters (M = Sc, Y ) which have been described in the second section of chapter three. Different geometries of M42− clusters (M = Sc, Y ) were explored, and the planar butterfly-like D2h geometry (two fused triangles) was found to be the most stable isomer. This is unlike the case of Al42− where D4h isomer was the most stable one as reported in the literature. In D2h geometry of M42− clusters (M = Sc, Y ), significant electron delocalization in each wing of the butterfly indicated fused d aromaticity. Atomization energy and chemical hardness supported the preference of D2h geometry over the D4h geometry. Molecular orbital analysis showed that the d-electrons were delocalized in each triangle of D2h geometry. Our interest in the search of new kinds of binuclear sandwich compounds led us to consider sandwiched metal dimers CB5H6M - MCB5H6 (M = Si, Ge, Sn) which are at the minima in the potential energy hypersurface with a characteristic M - M single bond. This work has been described in the first section of chapter four. The NBO analysis and the M - M distances ( ˚A) (2.3, 2.44 and 2.81 for M= Si, Ge, Sn respectively) indicated substantial M - M bonding. Consecutive substitution of two boron atoms in B7H7−2 by M (Si, Ge, Sn) and carbon respectively led to neutral MCB5H7, where M - H bond bent towards the carbon side of the five membered ring. Dehydrogenation of two MCB5H7 might lead to our desired CB5H6M - MCB5H6 where similar bending of M -M bond has been observed. The bending of M - M bond in CB5H6M -MCB5H6 was more than the M - H bending in MCB5H7. Molecular orbital analysis has been done to understand the bending. Larger M - M bending observed in CB5H6M - MCB5H6 in comparison to M - H bending observed in MCB5H7 was suspected to be favored by stabilization of one of the M - M π bonding MO’s. Preference of M to occupy the apex of pentagonal skeleton of MCB5H7 over its icosahedral analogue MCB10H11 has been observed. Structures of sandwiched binuclear L- M – M - L where M = Ti, Zr and L = Cp, C3B3H6 were also investigated as described in second section of chapter four. We found that these compounds having bent geometry with short M - M distance (1.87˚A for M=Ti and 2.29˚A for M=Zr) lie at the minima in the potential energy hypersurface. Bending from the linear geometry led to the stabilization of M - L antibonding interaction in L - M – M - L. Molecular orbital analysis, NBO calculations, Wiberg bond index and charge analysis suggested M2+ unit to be embedded in between two L’s in L - M – M - L. Molecules that have the ability to perform interesting mechanical motions have always been of great interest. Umbrella inversion of ammonia is one of the most interesting and well studied phenomena. This study has led to the development of the MASER. The possibility of inversion of the molecule C9H9−Li+ by the movement of Li+ through the C9H9−ring was studied earlier [Das et al, Chem. Phys. Lett. 365, 320 (2002)]. In the fifth chapter theoretical investigation on a B12 cluster has been reported, which could exhibit a through ring umbrella inversion. Calculations showed that a part of the molecule, consisting of a three membered boron ring could invert through the rest, viz., a nine membered boron ring. Using a simple model, the double well potential for the motion was calculated. The barrier for inversion was found to be 4.31 kcal/mol. The vibrational levels and tunneling splitting were calculated using this potential. It was found that the vibrational excitation to the v = 17 level caused large amplitude “inversion oscillation” of the molecule. After considering the tunneling effect, inversion rate at 298K was calculated by using transition state theory and was found to be 1.17 x 1010/s. Finally, in the last chapter the main results of the thesis have been summarized.

Over the past few decades, Ru catalyzed transfer hydrogenation (TH) and asymmetric transfer hydrogenation (ATH) reactions of unsaturated hydrocarbons, imine, nitro and carbonyl compounds have emerged as economic and powerful tools in organic synthesis. These reactions are most preferred processes having applications in the synthesis of fine chemicals to pharmaceuticals due to safe handling as these do not require hazardous pressurized H2 gas. The catalytic activity and selectivity of Ru complexes were investigated with a variety of ligands based on pincer NHC, cyclophane, half-sandwich, organophosphine etc. These ligands coordinate to Ru center in a proper orientation with a labile group replaced by H-source (like methanol, isopropanol, formic acid, dioxane, THF), which facilitate the β-hydrogen transfer to generate metal hydride species (Ru-H) and produce desired reduced product. This chapter describes the recent advances in TH and ATH reactions with homogeneous and heterogeneous Ru catalysts having different ligand environments and mechanistic details leading to their sustainable industrial applications.

The paper outlines the development and applications of compound bearings made of PTFE (Poly Tetra Fluoro Ethylene) and synthetic rubber, which enable the shaft to start up without initial lubricating water. The unique characteristic is the three-layer structure using elastic, synthetic rubber which is sandwiched between the PTFE compound and the outer metal shell. This special structure is designed to solve bearing issues that are incompatible with each other. That the bearing has sufficient hardness to be excellent against wear and yet is flexible to compensate for shaft misalignment and vibration. Friction characteristics and performance data are introduced comparing PTFE and conventional rubber bearings. Long-time running tests are carried out in very demanding conditions and the test data are shown. Over 15 years of actual operational service data on naval vessels and high speed, long-distance cruising ferries are introduced.

Abstract While some polymers are engineered to improve strength and endurance under elevated temperatures, these same materials are costly both economically and environmentally with the latter of the two stimulating the interest for this study. Polymers, more specifically foam cells are generally flame retardant. When ignited, toxins such as fluorine, bromine and other metallic salts are given off in the air. This poses potential environmental hazards. However, metallic materials (Aluminum) with their high strength, stiffness and ductility are much more environmentally friendly. Even if alloyed with appropriate compounds, the resulting core material could be melted down, separated then cast into new stock. Moreover, the use of an alloyed material can generally enhance the strength and stiffness of sandwich composite structures so essential in aerospace applications. United Technologies Research Center provided a plate of Aluminum alloy foam for impact testing by North Carolina A&T Researchers and graduate students. The material was provided by Austrian Metals Co. (AMAG) to UTRC under ONR Contract # N00014-95-C-0231, Thompson & Renauld (1997). All specimens were cut from one sample of nominal dimensions of 20 inches by 20 inches by 0.65 inches in thickness. The sample mass was 3142 grams and the apparent density was 0.737 g/cc. The chemical composition is close to that of 6061. The sheet sample was formed by AMAG and heat treated to T5 specifications consisting of 14 hours in a furnace at 160 °C. Generally the bending stiffness and failure mechanisms were substantially different from those of polymeric foam sandwich cores made of Rohacell, a polymethacrylimide (PMI) foam in a prior study, Craft et al (1997). Rohacell is an easily machined, but a hygroscopic form with low shear strength and stiffness, but it and many other organic foams have a relatively uniform cellular construction in a wide variety of densities.