• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 4876
  • 1479
  • 686
  • 321
  • 181
  • 162
  • 148
  • 148
  • 148
  • 148
  • 148
  • 146
  • 83
  • 74
  • 37
  • Tagged with
  • 9794
  • 2032
  • 1443
  • 1325
  • 1106
  • 605
  • 585
  • 575
  • 500
  • 490
  • 464
  • 386
  • 376
  • 369
  • 352
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Stereochemistry and physical properties of several cyclopentadienyl cobalt and nickel carbonyl complexes

Byers, Lance Rollins. January 1978 (has links)
Thesis--Wisconsin. / Vita. Includes bibliographical references.

Ueber die Substitution des Chinolins und Tetrahydrochinolins in der 6-Stellung ...

Peters, Paul, January 1900 (has links)
Dissertation--Hamburg, 1925. / Lebenslauf.

Reduction of beryllium compounds with magnesium

Wang, Pei, January 1948 (has links) (PDF)
Thesis (M.S.)--University of Missouri, School of Mines and Metallurgy, 1948. / Vita. The entire thesis text is included in file. Typescript. Title from title screen of thesis/dissertation PDF file (viewed July 8, 2010) Includes bibliographical references (p. 39-41).

New approaches to nitrogen ligands bearing electron withdrawing groups and their role in coordination chemistry

Shukla, Piyush, Cowley, Alan H. January 2003 (has links)
Thesis (Ph. D.)--University of Texas at Austin, 2003. / Supervisor: Alan H. Cowley. Vita. Includes bibliographical references. Also available from UMI.

Synthesis and evaluation of ferrocenylpyrazolyl and ferrocenylpyrazolyl-phosphine palladium and nickel complexes as ethylene oligomerization catalysts

Van der Westhuizen, Arnoux 07 June 2012 (has links)
M.Sc. / Several bis[1-ferrocenyl(ethyl)pyrazolyl palladium dichloro (complexes 1 and 3) and palladium chloromethyl complexes (complexes 2 and 4) have been synthesized by the reactions of 1- ferrocenyl(ethyl)-1N-pyrazole and 1-ferrocenyl(ethyl)-1N-(3,5-dimethyl)pyrazole with [PdCl2(NCMe)2] and [PdClMe(cod)] respectively. Furthermore, a library of phosphorus^nitrogen (P^N) ferrocenyl(ethyl)-amine and -pyrazolyl ligands have been successfully synthesized using the well known Ugi amine (compound 5) as intermediate. 1- [2-{diphenylphosphino}ferrocenyl](ethyl)amine and 1-[{2-diphenylphosphino}ferrocenyl](ethyl)- pyrazolyl Ni(II) and Pd(II) complexes were synthesized by reacting 1-[2- {diphenylphosphino}ferrocenyl](ethyl)dimethylamine, 1-[2-{diphenylphosphino}ferrocenyl](ethyl)- 1N-pyrazole and 1-[2-{diphenylphosphino}ferrocenyl](ethyl)-1N-(3,5-dimethyl)pyrazole with [NiCl2•6H2O] (compounds 12 and 16), [NiBr2(DME)] (compounds 13, 17 and 19), [PdCl2(NCMe)2] (compounds 10, 14, and 18) and [PdClMe(cod)] (compounds 11 and 15), respectively. 1-[2- {Diphenylphosphino}ferrocenyl(ethyl)-1N-(3,5-dimethyl)pyrazole (compound 9) was synthesized by two distinct methodologies. In one method, 1-ferrocenyl(ethyl)dimethylamine was converted to 1-[2- {diphenylphosphino}ferrocenyl](ethyl)dimethylamine before it was subsequently reacted with 3,5- dimethylpyrazole to produce 1-[2-{diphenylphosphino}ferrocenyl(ethyl)-1N-(3,5-dimethyl)pyrazole. In the other method, 1-ferrocenyl(ethyl)-1N-(3,5-dimethyl)pyrazole was converted to 1-[2- {diphenylphosphino}ferrocenyl](ethyl)-1N-(3,5-dimethyl)pyrazole before the reaction with 3,5- dimethylpyrazole, producing 1-[2-{diphenylphosphino}ferrocenyl(ethyl)-1N-(3,5-dimethyl)pyrazole. These compounds synthesized via different methods as well as their palladium dichloro complexes show different structures in solution, but solid state structural analysis agrees on the same structure. The structural difference in solution is contributed to the high degree of flexibility at the stereogenic centre of the complex. The Ni(II) ferrocenyl phosphine complexes 12, 13, 16, 17 and 19 exist in equilibrium between diamagnetic square planar form and paramagnetic tetrahedral form. The tetrahedral geometry is xvi favoured over the square planar geometry, purely on steric grounds, but the square planar geometry occurs with d8 complexes because of the more favourable electronic situation of the complex. Activation of these P^N palladium and nickel ferrocenyl- amine and -pyrazolyl pre-catalysts 10, 12, 13, 14, 16, 17, 18a and 19 with EtAlCl2 results in the oligomerization of ethylene to C4 and C6 alkenes, followed by subsequent Friedel-Crafts alkylation of the toluene solvent. Moderate catalytic activities of up to 659 kg of alkylated toluene products.mol-1 Ni. h-1 were observed for catalyst 13 at 20 bar ethylene pressure. In general, the Ni(II) pre-catalysts were more active than the Pd(II) precatalyst.

Some iron and copper complexes

Morpurgo, Giorgio January 1967 (has links)
No description available.

Equilibrium studies of complex compounds of sulphur

Gidden, R. D. January 1965 (has links)
No description available.

Chemistry of bis(alkyl) nitrosyl and related complexes of molybdenum and tungsten

Dryden, Neil H. January 1990 (has links)
The reactions of (ɳ⁵-C₅R₅)M(NO)(CO)₂ (R = H, Me; M = Mo, W) with PCl₅ result in the formation of the corresponding (ɳ⁵-C₅R₅)M(NO)(Cl)₂ products in high isolated yields (85-95%). These products have been fully characterized by conventional analytical and spectroscopic techniques including an X-ray crystallographic study of [ɳ⁵-C₅Me₅)Mo(NO)(Cl)₂]₂. Alkylation of the (ɳ⁵-C₅R₅)W(NO)(Cl)₂ compounds with Grignard reagents results in the formation of the corresponding complexes, (ɳ⁵-C₅R₅)W(NO)(R')₂ (R = H, Me; R' = CH₂CM₃, CH₂CM₂Ph: R = Me; R' = p-C₆H₄Me, Ph). An electrochemical study of (ɳ⁵-C₅H₅)W(NO)(CH₂CMe₃)₂, (ɳ⁵-C₅H₅)W(NO)(CH₂CMe₂Ph)₂, and (ɳ⁵-C₅Me₅)W(NO)(p-C₆H₄Me)₂ shows 2 successive, chemically reversible, one electron reductions in THF for each complex. The complexes (ɳ⁵-C₅R₅)W(NO)(R')₂ (R = H; R' = CH₂CMe₃, CH₂CMe₂Ph: R = Me; R' = CH₂CMe₂Ph,p-C₆H₄Me) react with 1 atm of CO resulting in the formation of the singly inserted products (ɳ⁵-C₅R₅)W(NO){C(O)R'}(R') in good yields, presumably via initial CO coordination. These acyl complexes have been completely characterized by conventional techniques. The IR and NMR spectroscopic properties of these complexes are indicative of an ɳ²-acyl coordination mode for all of the acylalkyl and acylaryl products. Under 6 atm of CO the (ɳ⁵-C₅H₅)W(NO)(R')₂ (R' = CH₂CMe₃, CH₂CM₂Ph) complexes are doubly carbonylated to form the corresponding (ɳ⁵-C₅H₅)W(NO){C(O)R'}₂ products. Furthermore, (ɳ⁵-C₅Me₅)W(NO){C(O)p-C₆H₄Me}(p-C₆H₄Me) reacts to form (ɳ⁵-C₅Me₅)W(NO)(CO){C(O)p-C₆H₄Me}(p-C₆H₄Me) under 6 atm of CO, but there is no evidence for the formation of a bis(acyl) product. A preliminary X-ray crystallographic investigation of (ɳ⁵-C₅H₅)W(NO){C(O)CH₂CMe₂Ph}₂ reveals the presence of one ɳ²-acyl ligand and one ɳ¹acyl ligand. The ¹H and ¹³C{¹H} NMR spectra of the (ɳ⁵-C₅H₅)W(NO){C(O)R'}₂ compounds exhibit signals for only one type of acyl ligand, indicating that the complexes are stereochemically non-rigid in solution through a process which averages the signals for the ɳ¹and ɳ³- acyl ligands. The bis(benzyl) complexes, (ɳ⁵-C₅R₅)M(NO)(CH₂Ar)₂ (R = H, Me; M = Mo, W; Ar = Ph, p-Tol), react with HCl to form (ɳ⁵-C₅R₅)M(NO)( ɳ²-CH₂Ar)(Cl) complexes. These complexes have been reacted with Grignard reagents, R'MgCl, to form the corresponding (ɳ⁵-C₅R₅)M(NO)( ɳ²-CH₂Ar)(R') (R' = CH₂SiMe₃, CH₂CMe₃, p-Tol) products. The benzyl ligand in all of these complexes is coordinated in an ɳ²-fashion, similar to that seen in the solid-state molecular structures of the bis(benzyl) precursors. The coordination mode of the benzyl ligands has been confirmed by solid-state molecular structure determinations of the representative examples (ɳ⁵-C₅Me₅)Mo(NO)(CH₂Ph)(Cl) and (ɳ⁵-C₅Me₅)Mo(NO)(CH₂Ph)(CH₂SiMe₃). The ¹H and ¹³C{¹H} NMR spectroscopic data for all of the complexes are discussed, with focus on the diagnostic characteristics for the ɳ²-benzyl ligand. A possible qualitative interpretation for the symmetric ɳ²-bonding mode in these complexes is presented. The (ɳ⁵-C₅Me₅)M(NO)( ɳ²-CH₂Ph)(Cl) (M = Mo, W) complexes react with AgBF₄ in CH₃CN to form electrophilic complexes of the type [(ɳ⁵-C₅Me₅)M(NO)( ɳ²-CH₂Ph)(NCCH₃)]BF₄. The solid-state molecular structures of these complexes are discussed and contrasted with those found for the neutral ɳ²-benzyl complexes. The reaction of racemic AgO₂CCH(Et)(Ph) with the (ɳ⁵-C₅R₅)M(NO)( ɳ²-CH₂Ph)(Cl) (R = H, Me; M = Mo, W: R = H; M = Mo) compounds forms the corresponding diastereomeric (ɳ⁵-C₅R₅)M(NO)( ɳ¹-CH₂Ph)(O₂CCH(Et)(Ph)) products. The ɳ¹ coordination of the benzyl ligand and bidentate coordination of the carboxylate ligand are established by the IR, ¹H, and ¹³C{¹H} NMR spectroscopic data for these products. A mixture of two diasteromeric products is demonstrated by the ¹H and ¹³C{¹H} NMR spectroscopic data and initial attempts to separate these diastereomers by crystallization are described. / Science, Faculty of / Chemistry, Department of / Graduate

Tertiary phosphine complexes of zirconium(IV) and hafnium(IV)

Carter, Alan January 1985 (has links)
The tetra-halides of zirconium and hafnium were reacted with one equivalent of the potentially tridentate hybrid ligand, N(SiMe₂CH₂PR₂)2-, (R = Me, i-Pr, t-Bu) to generate the corresponding mono-ligand complexes MCl₃{N(SiMe₂CH₂PR₂)₂), (M = Zr, Hf). Based on the results obtained from the solution spectroscopic data and the single crystal X-ray diffraction analyses of HfCI₃{N(SiMe₂CH₂PMe₂)₂> and ZrCl₃{N(SiMe₂CH₂P(i-Pr)₂)₂) the stereochemistries of all the MCI ₃{N(SiMe ₂CH₂PR₂) ₂) complexes were found to be meridional in solution, but both facial and meridional geometries were displayed in the solid state dependent on the ligand. The mono-ligand derivatives served as useful starting materials for the generation of zirconium- and hafnium-carbon bonds. Thus the addition of three equivalents of MeMgCl to one equivalent of MCl₃{N(SiMe₂CH₂PR₂)₂} generated the trimethyl complexes M(CH₃)₃{N(SiMe₂CH₂PR₂)₂}. When two equivalents of MeMgCl was added to the mono-ligand complexes, an inseparable mixture of the monomethyl and dimethyl derivatives was obtained. The stereochemistry of Hf(CH₃)₃{N(SiMe₂CH₂PMe₂)₂} is facial in the solid state but displays unusual fluxional behaviour in solution. This behaviour is observed for all the trimethyl derivatives as a consequence of the dissociative nature of the phosphine donors. Several possible rearrangement pathways for these compounds are discussed in an attempt to interpret this behaviour in solution. / Science, Faculty of / Chemistry, Department of / Graduate

Aspects of the organometallic nitrosyl chemistry of Cr, Mo and W

Hunter, Allen Dale January 1985 (has links)
The principal organometallic products resulting from the reactions of Na[(ƞ⁵-C₅H₄R)Cr(CO)₃] (R = H or Me) with allyl chlorides in THF are the green, dimeric [(ƞ⁵-C₅H₄R)Cr(CO)₃]₂ complexes (51-67% yields). The red organometallic by-products usually formed during these conversions are novel (ƞ⁶-6-alkenylfulvene)Cr(C0)₃ complexes (5-8% yields) which have been characterized completely by conventional spectroscopic methods. Dark green [W(N0)₂Cl₂]n may be synthesized in high yields by two preparative methods. The first method involves treatment of WCl₆ in CH₂Cl₂ with an excess of NO, and it proceeds via the isolable intermediate complexes, dark violet c̲i̲̲s̲-W(N0)₂Cl₄ and bright green f̲a̲c̲-W(NO)₃Cl₃. The second method involves controlled reaction of W(CO)₆ with two equivalents of ClN0 in CH₂Cl₂. It is initiated by traces of oxidant and probably proceeds via a catalytic, radical-chain mechanism that is described. If either reaction is effected in the presence of two equivalents of CH₃CN, then yellow-green W(N0)Cl₃(CH₃CN)₂ is the only nitrosyl-containing product formed. Polymeric [W(N0)₂Cl₂]n may be cleaved by a variety of Lewis bases, L, and (n̲-Bu)₃Sn(C₅H₅) to form W(N0)₂Cl₂L₂ (L = phosphine, phosphite, CH₃CN, etc.) and CpW(N0)₂Cl (Cp - ƞ⁵-C₅H₅), respectively, in good yields. The synthesis of the electron-rich nitrosyl complexes CpM(NO)L₂ (M = Cr, Mo, or W; L = P(0Me)₃, PMePh₂, P(n̲-Bu)₃, SbPh₃ or 1/2 (dppe)) is described. They are preparable in moderate to high yields by the reduction of the iodo dimers [CpM(NO)In]₂ (M = Cr, n = 1; M = Mo or W, n = 2) with sodium amalgam in THF ln the presence of the appropriate Lewis base, L, and they exhibit metal-dependent trends in vNO (Cr » Mo > W), δ ³¹P (Cr > Mo » W), and ²J₃₁p (Cr < Mo < W). These reduction reactions proceed via a number of transient intermediates, some of which are isolable. A unified mechanism for these reductive syntheses is proposed. The novel complexes, CpMo(NO)(ƞ⁴-trans-diene) (diene = acyclic conjugated diene) and CpMo(NO)(ƞ⁴-c̲i̲s̲-2,3-dlmethyl-butadiene)t are preparable in moderate yields by the reduction of [CpMo(NO)I₂]₂ with sodium amalgam in THF in the presence of the appropriate diene. The reaction between [CpMo(NO)I₂]₂ and C₄H₆•Mg•2(THF) results in the formation of a green, isolable oligomeric complex CpMo(NO)I(ƞ³-C₃H₄R) (where R = CH₂MgI and the nitrosyl oxygen acts as a Lewis base towards Mg) that can be hydrolyzed to CpMo(NO)I(ƞ³-C₄H₇) or converted to CpMo(NO)(ƞ⁴+-t̲r̲a̲n̲s̲-C₄H₆). These diene complexes have been fully characterized by conventional spectroscopic techniques (extensive ¹H and ¹³C NMR spectra being particularly informative) and by single-crystal X-ray structural determinations of CpMo(NO)(ƞ⁴-t̲r̲a̲n̲s̲-2,5-dimethyl-2,4-hexadiene) and CpMo(N0)(ƞ⁴-c̲i̲s̲-2,3-dimethyl-butadlene). A molecular orbital rationale for the structural and spectrocopic properties and relative stabilities of these c̲i̲s̲- and t̲r̲a̲n̲s̲-diene complexes is then presented. / Science, Faculty of / Chemistry, Department of / Graduate

Page generated in 0.5229 seconds