[PDF] Synthesis Structures And Characterization Of Coordination Compounds With The Transition Metals Niii Cuii Mnii Criii Feiii Using Ligands Based On Iminodiacetic Acid And N Heterocycles eBook

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Publisher : Cuvillier Verlag
Page : 150 pages
File Size : 37,58 MB
Release : 2004-03-29
Category : Science
ISBN : 3736910304

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The research into supramolecular chemistry presented in tis work has resulted in the synthtesis and characterization of twenty coordination compounds. These can be considered to fall into three categories:

Author : Peter J. Harrington
Publisher : Wiley-Interscience
Page : 520 pages
File Size : 23,28 MB
Release : 1990-04-13
Category : Science
ISBN :

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Examines the use of transition metal complexes as reagents for the synthesis of complex organic molecules. Presented here are total syntheses whose efficiency depends upon the unique reactivity patterns of organometallic complexes. For each total synthesis, the biological activity of the molecule is presented, followed by discussion of the principles of the organometallic processes involved.

Author : Pei Zhao
Publisher :
Page : pages
File Size : 32,36 MB
Release : 2015
Category :
ISBN : 9781339544052

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This dissertation focuses on the synthesis, characterization and reactivity study of terphenyl ligand stabilized bis([mu]-oxo) dimeric iron and cobalt complexes. The synthesis and characterization of low-coordinate cobalt alkyl and iron alkyl complexes are also described. In addition, it describes the preparation of the first monomeric homoleptic solvent-free bis(aryloxide) lanthanide complex. The solid state structures of new compounds were determined by single crystal X-ray crystallography. Magnetic properties of paramagnetic compounds were measured by superconducting quantum interference device (SQUID) or Evans' methods for solid state or solution phase, respectively. The new compounds were also characterized by UV-Visible spectroscopy. Furthermore, infrared spectroscopy, Mössbauer spectroscopy, electron paramagnetic resonance spectroscopy, mass spectrometry, cyclic voltammetry and elemental analysis were employed to characterize some of the compounds when applicable. In some cases, DFT calculations were applied to elucidate the bonding and energy levels of molecular orbitals in the complexes. In Chapter 2, The bis([mu]-oxo) dimeric complexes {Ar[superscript iPr8]OM([mu]-O)}2 (Ar [superscript iPr8] = -C6H-2,6-(C6H2-2,4,6-[superscript i]Pr3)2-3,5-[superscript i]Pr2; M = Fe or Co) were prepared by oxidation of the metal (I) half-sandwich complexes {Ar[superscript iPr8]M([eta]6-arene)} (arene = benzene or toluene; M = Fe or Co). The iron species {Ar[superscript iPr8]OFe([mu]-O)}2 was prepared by reacting {Ar[superscript iPr8]Fe([eta]6-benzene)} with N2O or O2 and the cobalt species {Ar[superscript iPr8]OCo([mu]-O)}2 was prepared by reacting {Ar[superscript iPr8]Co([eta]6-toluene)} with O2. Both {Ar[superscript iPr8]OFe([mu]-O)}2 and {Ar[superscript iPr8]OCo([mu]-O)}2 were characterized by X-ray crystallography, UV-vis spectroscopy, magnetic measurements and, in the case of the iron species, by Mössbauer spectroscopy. The solid-state structures of both compounds reveal unique M2([mu]-O)2 (M = Fe or Co) cores with formally three-coordinate metal ions. The Fe···Fe separation in {Ar[superscript iPr8]OFe([mu]-O)}2 bears a resemblance to that in the Fe2([mu]-O)2 diamond core proposed for the methane monooxygenase intermediate Q. The structural differences between {Ar[superscript iPr8]OFe([mu]-O)}2 and {Ar[superscript iPr8]OCo([mu]-O)}2 are reflected in rather differing magnetic behavior. Compound {Ar[superscript iPr8]OCo([mu]-O)}2 is thermally unstable and its decomposition at room temperature resulted in the oxidation of the Ar[superscript iPr8] ligand via oxygen insertion and addition to the central aryl ring of the terphenyl ligand to produce the 5,5'-peroxy-bis[4,6-[superscript i]Pr2-3,7-bis(2,4,6-iPr3-phenyl)oxepin-2(5H)-one]. The structure of the oxidized terphenyl species is closely related to that of a key intermediate proposed for the oxidation of benzene. In Chapter 3, the homoleptic, cobalt(I) alkyl [Co{C(SiMe2Ph)3}]2 was prepared by reacting CoCl2 with [Li{C(SiMe2Ph)3}(THF)] in a 1:2 ratio though the initial intent was to synthesize a dialkyl cobalt (II) complex. Attempts to synthesize the corresponding iron(I) species led to the iron(II) salt [Li(THF)4][Fe2([mu]-Cl)3{C(SiMe2Ph)3}2]. Both complexes were characterized by X-ray crystallography, UV-vis spectroscopy, and magnetic measurements. The structure of [Co{C(SiMe2Ph)3}]2 consists of dimeric units in which each cobalt(I) ion is [sigma]-bonded to the central carbon of the alkyl group -C(SiMe2Ph)3 and [pi]-bonded to one of the phenyl rings of the -C(SiMe2Ph)3 ligand attached to the other cobalt(I) ion in the dimer. The structure of [Li(THF)4][Fe2([mu]-Cl)3{C(SiMe2Ph)3}2] features three chlorides bridging two iron(II) ions. Each iron (II) ion is also [sigma]-bonded to the central carbon of a terminal -C(SiMe2Ph)3 anionic ligand. The magnetic properties of [Co{C(SiMe2Ph)3}]2 reveal the presence of two independent cobalt (I) ions with S = 1 and a significant zero-field splitting of D = 38.0(2) cm−1. The magnetic properties of [Li(THF)4][Fe2([mu]-Cl)3{C(SiMe2Ph)3}2] reveal extensive antiferromagnetic exchange coupling with J = -149(4) cm−1 and a large second-order Zeeman contribution to its molar magnetic susceptibility. Formation of the alkyl [Co{C(SiMe2Ph)3}]2 and the halide complex [Li(THF)4][Fe2([mu]-Cl)3{C(SiMe2Ph)3}2] under similar conditions is probably due to the fact that Co(II) is more readily reduced than Fe(II). Some other synthetic routes were also attempted to synthesize a dialkyl cobalt (II) complex and they are described in this chapter. Neither [Co(NPh2)2]2 nor cobaltocene reacts with [Li{C(SiMe2Ph)3}(THF)] to afford a dialkyl cobalt (II) complex. Metathesis reactions of cobalt halides with lithium salts of alkyl ligand HCPh2R (R = -Ph or -SiMe3) resulted in the reduction of cobalt (II) to cobalt metal and the coupling of ligands, which indicate that homolytic cleavage of the cobalt-carbon bond was probably involved in the metathesis reactions. Furthermore, in chapter 4, reaction of Sm[N(SiMe3)2]2(THF)2 with two equivalents of bulky aryloxide ligand HOAr[superscript iPr6] (Ar[superscript iPr6] = -C6H3-2,6-(C6H2-2,4,6-[superscript i]Pr3)2) afforded the first monomeric homoleptic solvent-free bis(aryloxide) lanthanide complex Sm(OAr[superscript iPr6])2. The complex was characterized by crystallography, UV-Visible spectrum, IR and magnetically by the Evans' method. The O-Sm-O angle is bent at 111.08(9)̊. The samarium ion in Sm(OAr[superscript iPr6])2 also shows weak interactions with the flanking aryl rings of the terphenyloxide ligands. The complex is paramagnetic at room temperature with magnetic moment of 3.51 [mu]B.

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Publisher :
Page : 512 pages
File Size : 13,34 MB
Release : 2009
Category :
ISBN :

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A group of ligands were designed based on a minimalist reduction of the structure of metalloproteins. It was thought that a modular design with facile synthesis could lead to a new family of privileged ligands. Towards this goal a series of tri-, tetra, and penta-dentate ligands were synthesized. The ligands had a common chiral core based on inexpensive amino acid starting materials. A modular diamine backbone was adjusted to control the size, bite angle and electronic nature of the binding pocket. The ligands were capped with Schiff base imines to provide an initial binding point for the metal and to create steric bulk at one face of the complex. The tetra-dentate ligands were shown to efficiently bind zinc(II), copper((II), nickel(II), and palladium(II). In the case of the penta-dentate ligands the series was extended to cobalt(II), manganese(II) and iron(II). The tri-dentate ligands did not form isolated metal complexes. The structures of these complexes were confirmed by NMR, ESR and X-ray crystallography. The chiral copper complexes were applied to a model asymmetric acylation reaction. The results were disappointing as the reactions showed no stereoselectivity.