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Substitution Chemistry of the Cobalt Complexes [Co₂(CO)₆(PhC≡CR) (R=Ph, H) and PhCCo₃(CO)₉] with the Diphosphine Ligands [Bis(diphenylphosphino)maleic Anhydride (BMA) and (Z)-Ph₂PCH=CHPPh₂]. Reversible Chelate-to-Bridge Diphosphine Ligand Exchange, Phosphorus-Carbon Bond Cleavage and Phosphorus-Carbon Bond Formation

Description: The tricobalt cluster PhCCo3(CO)9 (1) reacts with the bidentate phosphine ligand 2,3-bis(diphenylphosphino)maleic anhydride (bma) in the presence of added Me3NO to give the diphosphine-substituted cluster PhCCo3(CO)7(bma) (2). Cluster 2 is unstable in solution, readily losing CO to afford Co3(CO)6[(μ2-η2/η1-C(Ph)C=C(PPh2)C(O)OC(O)](μ2-PPh2) (3) as the sole observed product. VT-31P NMR measurements on cluster 2 indicate that the bma ligand functions as both a chelating and a bridging ligand. At -97 °C, 31P NMR analysis of 2 reveals a Keq of 5.7 in favor of the bridging isomer. The bridged bma cluster 2 is the only observed species above -50°C. The solid-state structure of 2 does not correspond to the major bridging isomer observed in solution but rather the minor chelating isomer. The conversion of 2 to 3 followed first-order kinetics, with the reaction rates being independent of the nature of the reaction solvent and strongly suppressed by added CO, supporting a dissociative loss of CO as the rate-determining step. The activation parameters for CO loss were determined to be ΔH≠ = 29.9 ± 2.2 kcal/mol and ΔS≠ = 21.6 ± 6 eu.
Date: December 1994
Creator: Yang, Kaiyuan
Partner: UNT Libraries

Synthetic Approaches to (smif)₂Ti (smif=1,3-di-(2-pyridyl)-2-azaallyl) Reveal Redox Non-Innocence and C-C Bond-Formation

Description: Article discussing synthetic approaches to (smif)₂Ti(smif=1,3-di-(2-pyridyl)-2-azallyl) revealing redox non-innocence and C-C bond-formation.
Date: July 25, 2012
Creator: Frazier, Brenda A.; Wolczanski, Peter T.; Keresztes, Ivan; DeBeer, Serena 1973-; Lobkovsky, Emil B.; Pierpont, Aaron W. et al.
Partner: UNT College of Arts and Sciences

A Ferrocene-Based Catecholamide Ligand: the Consequences of Ligand Swivel for Directed Supramolecular Self-Assembly

Description: A ferrocene-based biscatecholamide ligand was prepared and investigated for the formation of metal-ligand supramolecular assemblies with different metals. Reaction with Ge(IV) resulted in the formation of a variety of Ge{sub n}L{sub m} coordination complexes, including [Ge{sub 2}L{sub 3}]{sup 4-} and [Ge{sub 2}L{sub 2}({mu}-OMe){sub 2}]{sup 2-}. The ligand's ability to swivel about the ferrocenyl linker and adopt different conformations accounts for formation of many different Ge{sub n}L{sub m} species. This study demonstrates why conformational ligand rigidity is essential in the rational design and directed self-assembly of supramolecular complexes.
Date: February 4, 2010
Creator: Mugridge, Jeffrey; Fiedler, Dorothea & Raymond, Kenneth
Partner: UNT Libraries Government Documents Department

Influence of Fluorine Substitution on the Properties of Metal Chelate Compounds

Description: From introduction: "This is the first of three articles dealing with the influence of fluorine substitution in the ligand on the properties of metal chelate compounds. Although the primary purpose of this project was to study the influence of fluorine substitution on the properties -- particularly light absorption -- of uranyl compounds, copper chelates were chosen for preliminary study as model substances, because they are easily prepared."
Date: June 9, 1955
Creator: Belford, R. Linn; Martell, Arthur E. & Calvin, Melvin
Partner: UNT Libraries Government Documents Department

Diphosphine Ligand Activation Studies with Organotransition-Metal Compounds

Description: Thermolysis of CoRu(CO)7(m -PPh2) (1) in refluxing 1,2-dichloroethane in the presence of the diphosphine ligands 2,3-bis(diphenylphosphino)maleic anhydride (bma) and 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) furnishes the new mixed-metal complexes CoRu(CO)4(μ -P-P)(μ -PPh2) [where P-P = bma (3); bpcd (6)], along with trace amounts of the known complex CoRu(CO)6(PPh3)(μ -PPh2) (4). The requisite pentacarbonyl intermediates CoRu(CO)5(μ -P-P)(μ -PPh2) [where P-P = bma (2); bpcd (5)] have been prepared by separate routes and studied for their conversion to CoRu(CO)4(μ -P-P)(μ -PPh2). The complexes 2/3 and 5/6 have been isolated and fully characterized in solution by IR and NMR spectroscopy. The kinetics for the conversion of 2→3 and of 5→6 were measured by IR spectroscopy in chlorobenzene solvent. On the basis of the first-order rate constants, CO inhibition, and the activation parameters, a mechanism involving dissociative CO loss as the rate-limiting step is proposed. The solid-state structure of CoRu(CO)4(μ -bma)(μ -PPh2) (3) reveals that the two PPh2 groups are bound to the ruthenium center while the maleic anhydride π bond is coordinated to the cobalt atom. Thermolysis of the cluster Ru3(CO)12 with the bis(phosphine)hydrazine ligand (MeO)2PN(Me)N(Me)P(OMe)2 (dmpdmh) in toluene at 75°C furnishes the known clusters Ru4(CO)12[μ -N(Me)N(Me)] (9) and Ru3(CO)11[P(OMe)3] (10), in addition to the new cluster Ru3(CO)10(dmpdmh) (8) and the phosphite-tethered cluster Ru3(CO)9[μ -P(OMe)3] (11). The simple substitution product Ru3(CO)10(dmpdmh), a logical intermediate to clusters 9-11, was synthesized by treating Ru3(CO)12 and dmpdmh with Me3NO in CH2Cl2 at room temperature, and independent thermolysis reactions using cluster 8 were shown to yield clusters 9-11. The tetrahedrane cluster FeCo2(CO)9(μ3-S) reacts with the redox-active ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) to give the disubstituted cluster FeCo2(CO)7(bpcd)(μ3-S) as the sole product. This diphosphine-substituted cluster contains a cobalt-bound, chelating bpcd ligand. The solid-state structure has been unequivocally established by X-ray diffraction analysis. Cyclic voltammetric studies on FeCo2(CO)7(bpcd)(μ3-S) reveal the presence of two quasireversible ...
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Date: December 2000
Creator: Wang, Jiancheng
Partner: UNT Libraries

Studies of the Mechanisms of Reactions of Binary Metal Carbonyls

Description: A kinetic study of the reactions of Group VI-B hexacarbonyls with primary amine and halide ligands was undertaken in order to determine the possible mechanisms of these reactions. As well as the expected dissociative pathway, the reactions with the primary amines were seen to proceed by a concurrent pathway which was dependent upon the ligand concentration. Since nitrogen donor ligands are expected to be poor donor ligands, the mechanism proposed was a "dissociative interchange" mechanism which should not be too dependent upon the nucleophilicity of the ligand. Comparison of the rate constants for the amines studied as well as those of the previously investigated Lewis base ligands indicated all such reactions may proceed through the same mechanism. The similarity in rate constants for the ligand-independent and ligand-dependent pathways supports this mechanism. The rate of formation of the final product was seen to be dependent upon the square of the mercuric halide concentration. Therefore, the conversion of Fe(CO)4(HgX)2 to the final product was proposed to proceed by the successive abstraction by each HgX group of two molecules of mercuric halide. These oxidative elimination reactions are related to a chemical model for the intermediate step in the reduction of dinitrogen to ammonia and their similarities and differences are discussed.
Date: May 1977
Creator: Pardue, Jerry E.
Partner: UNT Libraries

A Priori Assessment of the Stereoelectronic Profile of Phosphines and Phosphites

Description: This article discusses research that has demonstrated the utility of a rigorously calibrated, molecular mechanics/semiempirical quantum mechanical protocol for developing stereoelectronic (Tolman) maps for phosphine ligands.
Date: March 15, 2003
Creator: Cooney, Katharine D.; Cundari, Thomas R., 1964-; Hoffman, Norris W.; Pittard, Karl A.; Temple, M. Danielle & Zhao, Yong
Partner: UNT College of Arts and Sciences

Oxovanadium(IV) Complexes of Substituted N-(2-Thiophenyl)Salicylideneimine

Description: In an effort to study the spectral, magnetic, and stereochemical properties of vanadyl complexes, both a new series of vanadyl complexes derived from type (VII) ligands with subnormal magnetic moment and from type (VIII) ligands with normal magnetic moment are synthesized and characterized.
Date: June 1970
Creator: Lee, Cheng Chang
Partner: UNT Libraries

Experimental and Computational Studies of the Isomerization Reactions of Bidentate Phosphine Ligands in Triosmium Clusters: Kinetics of the Rearrangements from Bridged to Chelated Isomers and X-ray Structures of the Clusters Os3 (CO)10 (dppbz), 1,1-Os3 (CO)10 (dppbzF4), HOs3 (CO)9 [μ -1,2-PhP (C6H4-ɳ1) C6H4PPh2], and HOs3 (CO)9- [μ-1,2-PhP (C6H4-ɳ 1) C6F4PPh2]

Description: Article on experimental and computational studies of the isomerization reactions of bidentate phosphine ligands in triosmium clusters.
Date: February 22, 2011
Creator: Zhang, Xue; Kandala, Srikanth; Yang, Li; Watson, William H.; Wang, Xiaoping; Hrovat, David A. et al.
Partner: UNT College of Arts and Sciences

Synthesis of Gold Complexes From Diphosphine Ligands and Screening Reactions of Heterocyclic Acetylacetonato (ACAC) Ligands with Transitional Metal Complexes

Description: Syntheses of diphosphine gold (I) complexes from gold THT and two ligands, 4, 5-bis (diphenylphosphino)-4-cyclopenten-1, 3-dione (BPCD) and 2,3-bis(diphenylphosphino)-N-phenylmaleimide (BPPM), were done separately. The reactions happened under ice conditions followed by room temperature conditions and produced two diphosphine gold (I) complexes in moderated yield. Spectroscopic results including nuclear magnetic resonance (NMR) and X-ray crystallography were used to study and determine the structures of the products formed. Moreover, X-rays of all newly synthesized diphosphine gold (I) complexes were compared with the known X-ray structures of other phosphine and diphosphine gold (I) complexes. There were direct resemblances in terms of bond length and angle between these new diphosphine gold (I) complex structures and those already published. For instance, the bond lengths and angles from the newly prepared diphosphine gold (I) complexes were similar to those already published. Where there were some deviations in bond angles and length between the newly synthesized structures and those already published, appropriate explanation was given to explain the deviation. Heterocyclic ligands bearing acetylacetonate (ACAC) side arm(s) were prepared from ethyl malonyl chloride and the heterocyclic compounds 8-hydroxylquinoline, Syn-2-peridoxyaldoxime, quinoxalinol and 2, 6-dipyridinylmethanol. The products (heterocyclic ACAC ligands) from these reactions were screened with transition metal carbonyl compounds in thermolytic reactions. The complexes formed were studied and investigated using NMR and X-ray crystallography. Furthermore, the X-ray structures of the heterocyclic ACAC ligand or ligand A and that of rhenium complex 1 were compared with similar published X-ray structures. The comparison showed there were some similarities in terms of bond length and bond angles.
Date: August 2015
Creator: Nyamwihura, Rogers
Partner: UNT Libraries

Unusual Electronic Features and Reactivity of the Dipyridylazaallyl Ligand: Characterizations of (smif)2M [M = Fe, Co, Co+, Ni; smif = {(2-py)CH}2N] and [(TMS)2NFe]2(smif)2

Description: Article discussing unusual electronic features and reactivity of the dipyridylazaallyl ligand and characterizations of (smif)2M [M = Fe, Co, Co+, Ni; smif = {(2-py)CH}2N and [(TMS)2NFe] 2(smif)2.
Date: February 19, 2009
Creator: Frazier, Brenda A.; Wolczanski, Peter T.; Lobkovsky, Emil B. & Cundari, Thomas R., 1964-
Partner: UNT College of Arts and Sciences

Substitution chemistry of Ruthenium clusters with the diphosphine ligands: 4,5-Bis(diphenylphosphino)-4-cyclo-penten-1,3-dione (bpcd), (Z)-Ph₂PCH=CHPP₂ and 3,4-Bis(diphenylphosphino)-5-methoxy-2(5H)-furanone (bmf)

Description: This study embarks on a program designed to study the reactivity of polynuclear clusters with redox-active phospines in an effort to prepare new ligand/cluster redox systems. This study aims to prove that such compounds will display superior electron reservoir capabilities, as a result of the cooperative mixing of ligand and cluster orbitals.
Date: May 1997
Creator: Shen, Huafeng
Partner: UNT Libraries

Heats of Solution of the Cobaltous Nitrate Hydrates in Water and in Certain Organic Solvents and Binding Energies of Molecular Ligands

Description: Abstract: "Heats of solution have been measured for the hexahydrate, tetrahydrate, trihydrate and dihydrate of cobaltus nitrate in water and in a series of organic solvents, including isobutyl alcohol, diethyland monoethyl ether of ethylene glycol, acetone, methyl ethyl ketone, tetrahydrofuran, tributyl phosphate and dimethyl formanide. For some solvents, where the solubility of the salt of its reaction product was insufficient, measurements were made in a mixture with acetone. Such solvents include diethyl ether, tetrahydrofurfuryl alcohol, and pyridine. Measurements were also made with mixtures of the other solvents cited and acetone. In the cases of pyridine, water, tetrahydrofurfuryl alcohol and isobutyl alcohol, evidence is found for a transition from a probably tetrasolvated neutral molecule in solution to a hexasolvated entity, frequently of lowered solubility. The solvents can be arrayed in order of base strengths on the basis of the heat measurements, and it is possible to estimate energies of binding of solvent groups by the metal atom. As a check on these some measurements of the heats of solution of some cobaltous nitrate pyridinates are also presented."
Date: February 1952
Creator: Katzin, Leonard I. & Ferraro, John R.
Partner: UNT Libraries Government Documents Department

A Reinvestigation of the Kinetics and Mechanism of Ligand Exchange in Mu-(2,2,8,8-Tetramethyl-3, 7-Dithianonane)-Decacarbonylditungsten(0)

Description: This student is interested in reinvestigating the kinetics and mechanism of the bridged compound in l,2-dichloroethane with triisopropyl phosphite and in finding the reasons why the values of competition ratio k₋₂ /k₃ in this reaction are so large.
Date: August 1988
Creator: Liao, Jing-Piin
Partner: UNT Libraries