1,720,990 research outputs found
Synthesis and reactivity of low-valent group 14-15 compounds
Full text linkxviii, 164 leaves : ill. ; 29 cm.Includes abstract and appendices.Includes bibliographical references (leaves 155-164).The synthesis, characterization and preliminary reactivity of a new diphosphine is discussed. Calculations indicated a favorable dissociation of the central P-P bond, corresponding to roughly 100kJ/mol relaxation energy for the full system. Reactions of (Dipp[subscript 2]C[subscript 2] H[subscript 4]N[subscript 2]P)[subscript 2] with elemental phosphorus (P[subscript 4]), sulfur (S[subscript 8]), oxygen (O[subscript 2]), selenium (Se[superscript 0]) and tellurium (Te [superscript 0]) yielded the trans,trans-tetraphosphabicyclobutane (LP-P[subscript 4]-PL), persulfide/sulfide (LP-S-S-PL/LP-S-PL), ethereal oxidative products (LP(O)-O-(O)PL, LP(Se)-Se-PL) as well as bridging selenide (LP-Se-PL) and telluride (LP-Te-PL) species. Reactions with boranes (BR[subscript 3], R = H or C[subscript 6]F[subscript 5]) supported an FLP-type reactivity profile (LP[arrow right]BR3 ) and subsequent hydrogen abstraction forming LPH[arrow right]BR[subscript 3]. Activation of heteroallenes including CS[subscript 2], Ph-NCO, and Ph-NCS was achieved, forming the corresponding insertion products (LP-C(=R)-X-PL). The nucleophilic ring-opening of S[subscript 4]N[subscript 4] with carbenes was investigated. IMes formed IMes=N-S[subscript 3]N[subscript 3] while more electrophilic carbenes formed zwitterionic R-S-N-S[subscript 4]N[subscript 3] (R = SIPr, CAAC) structures. Introduction of nucleophilic solvents induced degradation of the S[subscript 3]N[subscript 3] rings to R=NSNSS (R = IMes, SIPr) structures
Phosphorus cations and bulky cyclopentadienyl ligands
Full text linkxix, 164 leaves : ill. ; 29 cmIncludes abstract.Includes bibliographical references.The synthesis and characterisation of some ethynylphosphonium salts are described starting from 1-bromo-2-phenylacetylene and tertiary phosphines. Structural information for these molecules has been obtained using X-ray crystallography, and deviant reactivity was observed at elevated temperatures when the electron-rich tris(2,4,6-trimethoxyphenyl)phosphine was employed. A new approach to the corresponding 1,4-bis(ethynylphosphonium) salts was also developed by a similar reaction, and the first bis(ethynylphosphonium) salts were characterised using X-ray crystallography.
Exploratory research into the synthesis of m-terphenyl substituted cyclopentadienyl ligands (Ter[superscript Mes]Cp and Ter[superscript Dipp]Cp) is also described. A new synthetic route is presented and is accomplished through the reaction of aryl lithium reagents with cobaltocenium salts, followed by oxidation of the intermediate cobalt(I) species to afford the corresponding cyclopentadiene. The preparation, structural, and spectroscopic properties of the alkali metal salts (Li–Cs) is described, and some preliminary coordination chemistry is presented
Zirconocene derivatives for dehydrocoupling of acetylenes and carbene-phosphinidene adducts and their metal complexes
Full text link1 online resource (ix, 51 p.) : ill.Includes abstract.Includes bibliographical references (p. 48-51).Anionic Group 4 metallocenes have seen a significant amount of attention over the last 20 years with particular interest in titanocene and zirconocene derivatives.[superscript 1-5] The synthesis and characterization of dichlororbis([eta superscript 5]-cyclopentadienyl)zirconium (zirconocene dichloride or Cp[subscript 2]ZrCl[subscript 2] where Cp = [eta superscript 5]-C[subscript 5]H[subscript 5]) first described in 1954 by Wilkinson and Birmingham spurred extensive research in this field.[superscript 6] A particularly interesting area of these zirconocene derivatives comes from the work by Negishi et al. where an anionic zirconocene compound can be oxidized resulting in the coupling of two phenylacetylene molecules.[superscript 2] Similar to the Negishi zirconocene chemistry, Stephan et al. published a synthetic route for an anionic zirconocene trihydride.[superscript 7] Using both areas of research as a starting block, a catalytic process was investigated to dehydrocouple phenylacetylene using similar zirconocene derivatives. Although it was confirmed via Nuclear Magnetic Resonance (NMR) spectroscopy that a possible catalytic precursor was formed, no catalysis was successfully completed in this research.
A second aspect of fundamental main group chemistry involves the synthesis of carbene-phosphinidene adducts first described by Arduengo in 1997.[superscript 8] The bonding scenario of the P-C bond of the carbene-phosphinidene adduct was confirmed to have both single and double bond character.[superscript 9] With this unique property in mind, novel carbene-phosphinidene adducts were synthesized and characterized via single crystal X-ray diffraction techniques. Due to the interesting bonding nature of the carbene-phosphinidene adduct, the newly synthesized carbene-phosphinidene adducts were used in attempts to form metal complexes. Preliminary results indicate the formation of the first stable carbene-phosphinidene metal complex. Other preliminary results indicate the possibility of insertion reactions occurring with weaker P-C bonds in the carbene-phosphinidene adducts
Reduction of phosphorus substituted bulky amidines
Full text link1 online resource (viii, 57 pages) : illustrations, charts, graphsIncludes abstract and appendix.Includes bibliographical references (pages 40-45).A series of bulky N,N’ disubstituted amidines with bulky 2,6-diisopropyl substituents and theircorresponding PCl2 substituted derivatives were synthesized. PCl2 substituted formamidine, methyl amidine, and p-methylphenyl amidine derivatives were successfully synthesized, and characterized by 1H, 13C, and 31P NMR spectroscopy, along with X-ray crystallography. The P-N bonds were determined to be longer than previously described N-bound PCl2 substituted compounds. Furthermore, crystallographic data shows a planar geometry about the N-C-N-P linkage, proving conjugation within these compounds. Reducing agents, Mg, Cp2Co, and sodium napthalenide were then employed to the PCl2 substituted amidines. Notably, reduction of the PCl2 substituted p-methylphenyl amidine resulted in the selective formation of the corresponding diphosphene which was characterized by 1H, 13C, and 31P NMR spectroscopy, along with X-ray crystallography. Crystallographic data resulted in P-P bond lengths equivalent to previously reported N-bound diphosphenes. Furthermore, the P-P-N-C-N linkage for one side of the diphosphene existed in a cis-planar fashion, which is a new geometry observed for diphosphenes. This result prompted the idea to react the diphosphene with an oxonium acid which is believed to form a 5-membered heterocyclic cation that was characterized by 31P NMR.</p
A synthetic investigation of substituted cyclopentadienyl complexes of bismuth and germanium
Full text link1 online resource (xiv, 76 pages) : illustrations, chartsIncludes abstract and appendix.Includes bibliographical references (pages 57-64).A series of novel cyclopentadienyl bismuth and germanium metal complexes were prepared by using the sterically bulky 2,6-bis(2,4,6- trimethylphenyl)phenylcyclopentadienyl (TerMesCp) ligand. Mono-, bis-, and trisTerMesCp metal complexes were prepared by reacting TerMesCp-K with the metal halides: GeCl2, BiCl3, and BiI3. The bismuth complexes, TerMesCpBiI2, (TerMesCp)2BiI, and (TerMesCp)3Bi contained trigonal pyramidal bismuth metal centers coordinated to the cyclopentadienyl ring with hapticities of η1. The intermediate germanium complex, TerMesCpGeCl, contained a germanium metal center coordinated to the cyclopentadienyl ring with a hapticity of η1. Upon further reactivity, cationic germanium species [TerMesCpGe][GaCl4] and [TerMesCpGe][ B(3,5-CF3-C6H3)] were synthesized with germanium metal centers coordinated to the cyclopentadienyl ring with hapicities of η4 and η3 respectively. In some cases, stabilizing aryl interactions with the mesityl ring of the TerMesCp ligand are present. Cationic germanium species, [TerMesCp-Ge]+ , were synthesized by chloride abstraction from the germanium chloride using GaCl3, or by metathesis with Na[B(3,5-CF3-C6H3)]
Carbene reactivity with uncommon p-block molecules
No full text1 online resource (xxxiv, 445 pages) : illustrations (some colour), charts (some colour), graphs (some colour)Includes abstract and appendix.Includes bibliographical references (pages 16-20, 54-58, 79-83, 110-116, 140-145, 167-170).The p-block (main group) elements are those in groups 13-17 and this thesis involves reactivity of uncommon small molecules derived from p-block elements with carbenes, a highly reactive carbon-based functional group featuring low-oxidation state carbon. The recent historical isolation of carbenes and the discovery of their endlessly tunable chemical diversity has allowed for the subsequent isolation of many never-before-seen states of most elements. The behaviour of vastly different carbenes when reacted with common small molecules more has been widely explored. In this dissertation, an introduction to general chemistry and more specifically carbenes is included in chapter 1. Research into the use of a triazene derived from reacting a carbene and azide for the preparation of copper, silver, and gold metal complexes (and gold nanoparticles) is featured in chapter 2. Formation of a tellurourea by reacting a carbene with tellurium metal was then explored; subsequently reacting it with (PCF3)4 and S8 to form distinct nano-/micro-particles of tellurium with morphology control apparent through various solid substrates under a variety of controlled conditions in chapter 3. Reactivity of a carbene and carbon suboxide for the first time is featured in chapter 4. A wide scope of carbenes were then reacted with tetrasulfur tetranitride and thoroughly explored in chapter 5. Formation of germanium and tin dichloride carbene adducts is then studied with respect to preparing low-oxidation state allotropic group 14 metals in chapter 6, along with isolation of their trichloride salts. Finally, chapter 7 highlights how each of these works could be built upon, expanded, or further studied in order to probe the wide range of potential uses and applications each topic touches on. Supporting information for each is provided in the appendix at the end
New bulky cyclopentadienyl ligands and their metal complexes
Full text link1 online resource (xiii, 65 pages) : illustrations, graphs, chartsIncludes abstract and appendix.Includes bibliographical references (pages 50-54).Two novel bulky cyclopentadiene ligands were prepared, 2,6-bis(2,4,6-triisopropylphenyl) phenylcyclopentadiene (TerTripCpH) and 2-(2,4,6-triisopropylphenyl) phenylcyclopentadiene (TripBpCp). An optimized synthetic route is presented through the reaction of aryl lithium reagents with cobaltocenium salts, with subsequent oxidation using AgNO3 to afford the corresponding cyclopentadiene ligands. A series of novel metal complexes with both ligands were synthesized with their spectroscopic properties, structure, and preparation reported. The alkali metal salts (LiK), a ferrocene derivative, and the In metal complex of the TerTripCp ligand are reported with the Al complex being attempted. The K salt of the TripBpCp ligand is reported with a ferrocene derivative being attempted.</p
Biphenyl substituted cyclopentadienyl ligand complexes
Full text link1 online resource (71 p.) : illustrations (some colour)Includes abstract and appendix.Includes bibliographical references (p. 57-60).The synthesis of biphenyl substituted cyclopentadienyl ligands are described. The synthetic route
is accomplished through the reaction of aryl lithium reagents with cobaltocenium salts, followed
by oxidation of the intermediate cobalt(I) species to give the corresponding cyclopentadiene.
Detailed information on their preparation, structural, and spectroscopic properties are described.
A preliminary reaction towards the biphenyl substituted cyclopentadienyl ligand complexes
yielding the corresponding alkali metal salt (K) is also described. Its structural and spectroscopic
properties are described briefly
Cyclic alkyl phosphino carbenes – a synthetic investigation
Full text link1 online resource (64 pages) : illustrations (some colour), graphsIncludes abstract.Includes bibliographical references (pages 63-64).A proposed synthetic pathway to produce a cyclic (alkyl)(phosphino) carbene (CAPC)has been investigated. 1-bromo-2,4,6-tritertbutylbenzene (-2,4,6-tritertbutylbenzene =mes*) was used to produce Mes*PCl2. A ring closure to form a phosphacycle was performed, a methyl group was added to the phosphorus and was reacted with N-bromosuccinimide to form the carbene precursor. The purpose for this synthesis is to attempt to replicate CAACs and improve their properties by replacing nitrogen with phosphorus. A less sterically bulky approach was done using only one ortho tBu to allow the use of more sterically bulky substituents at phosphorus. This synthesis provides a start to synthesizing the first CAPC
Identification of key reaction products from molybdenum trioxide and ethylene glycol mixtures used for attempted molybdenum disulfide electrodeposition and synthesis of bidentate ligands and related group 1 and 13 metal complexes
Full text link1 online resource (XXI, 281 pages) : illustrations (chiefly colour), charts (some colour), graphs (some colour)Includes abstract.Includes bibliographical references (pages 12-16, 28-35, 93-103, 147-153, 204-208).Replication of a procedure to electrodeposit MoS2 required use of an uncharacterized crude MoO3 and ethylene glycol reaction mixture as a molybdenum precursor. Multiple attempts to replicate the desired “brown oil” resulted in isolating four crystals, with three being previously unknown products for this reaction. This evidence highlights possible identities for the molybdenum precursor responsible during this MoS2 electrodeposition. A sterically bulky phosphine-imine treated with either H2O2, S8, Se0 , or reacted with 9-bromofluorene followed by one equivalent of a base made four ligand precursors that can be deprotonated to act as mono-anionic ligands for a variety of metal complexes including Li-K, Al, and In. The four ligands undergo tautomerization revealing 2-4 isomers observed by 1H, 13C, and 31P NMR spectroscopy, with two of these supported by SC-XRD analysis. Alkali metal complexes showed diverse η2 to η4+6 interactions with the delocalized phosphonium fluorenylide and η1 /η2 with 2,6-diisopropylphenyl aromatic ring systems
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