Download or read book Low coordinate Iron and Cobalt Complexes written by Thomas R. Dugan and published by . This book was released on 2012 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Unsaturated transition metal complexes are important in many stoichiometric and catalytic bond cleavage reactions. Therefore, low-coordinate transition metal complexes coordinated with sterically hindered ancillary ligands have been used for C-H activation, N2, and CO bond cleavage reactions. In this thesis, the coordination chemistry and reactivity of low-coordinate [beta]-diketiminate cobalt and iron complexes toward bond-breaking and bond-making reactions is explored and presented. In chapter 2, the unsaturated complex LtBuCo (LtBu = bulky [beta]-diketiminate ligand) is reported. The [beta]-diketiminate ligand in LtBuCo was ligated to cobalt in a slipped [kappa]N, [eta]6-arene mode. Addition of Lewis bases to LtBuCo yielded rapid and reversible conversion to the [kappa]2N, N' mode. The rate law of ligand binding to LtBuCo was first-order in both cobalt and substrate concentration. Therefore, ligand coordination was consistent with an associative or interchange mechanism that either preceded or occurred simultaneously to [beta]-diketiminate isomerization. In addition, LtBuCo cleaved Sn-F and aryl C-F bonds, and homolytic Sn-F bond cleavage yielded [LtBuCo([mu]-F)]2. Aryl C-F bond cleavage by LtBuCo yielded [LtBuCo([mu]-F)]2 and a cobalt(II) aryl complex in a 1:2 molar ratio. [LtBuCo([mu]-F)]2 reacted with triethylsilane (Et3SiH) to give pure hydride complex [LtBuCo([mu]-H)]2, which has different properties than previously reported. In chapter 3, treatment of LMeFeNNFeLMe with 4-tert-butylpyridine (tBupy) displaced the dinitrogen ligand to give LMeFe(tBupy)2 which is formally iron(I). However, LMeFe(tBupy)2 can be defined as high-spin iron(I) with a resonance form that is high-spin iron(II) antiferromagnetically coupled to a radical on the tBupy ligand. In contrast, treatment of LMeFeNNFeLMe with pyridine (py) resulted in the reductive coupling of pyridine via C-C bond formation to give {LMeFepy}2([mu]-C10H10N2), a complex with a bridging 4,4'-bis(hydridopyridyl) ligand. {LMeFepy}2([mu]-C10H10N2) was diiron(II) in the solid state, but C-C bond formation was rapidly reversible as the solution properties were consistent with LMeFe(py)2. Chapter 4 reports new synthetic routes to iron hydride complexes with higher purity than previously achieved. The binuclear oxidative addition of H2 to a transient iron(I) intermediate yielded [LtBuFe([mu]-H)]2. This method was adapted for the synthesis of [LMeFe([mu]-H)]2, and the deuterated isotopologues, [LtBuFe([mu]-D)]2 and [LMeFe([mu]-D)]2, were synthesized using D2. The H/D exchange of hydride ligands between isotopologues and H2/D2 was observed"--Page ix-x.

Download or read book Synthesis and Reactivity of Low coordinate Cobalt Complexes and Iron I Alkyl Complexes Supported by beta diketiminate Ligand written by Keying Ding and published by . This book was released on 2009 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis and Characterization of Low Coordinate Transition Metal Complexes written by Aimee M. Bryan and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes the synthesis, characterization, and reactivity studies of new low-coordinate complexes of readily available and inexpensive transition metals such as iron, cobalt and nickel. The compounds were magnetically characterized in detail and tested for single molecule magnet (SMM) behavior. SMMs are a topic of intense research because of their potential applications in magnetic memory, high-density information storage and quantum computing technologies. Low-coordinate compounds display magnetic moments that indicate high orbital angular momentum and are very promising candidates for SMM behavior because they also tend to have large negative zero-field splitting (D) values. The complexes reported here are stabilized by using a variety of amido, aryloxo and thiolato ligands with bulky terphenyl groups and also using aryl and alkyl substituted silylamides. A superconducting quantum interference device (SQUID) and Evans' methods were used to study the magnetic properties and single crystal X-ray crystallography and NMR (1H and 13C) were used to confirm the structures of these compounds in both the solid and solution states. Further characterization studies included UV-visible, near-IR, and IR spectroscopy, melting point, elemental analysis and DFT calculations, where applicable, in order to determine the electronic configurations and bonding schemes. At present there are ca. 100 stable open shell two-coordinate mononuclear transition metal complexes currently known but ca. 20% have a linear coordination at the metal atom with only a few being strictly 180° at their metal center. Very few of these compounds had been magnetically characterized. In Chapter 2, the synthesis and magnetic characterization of the late transition metal Co2+ (d7) and Ni2+ (d8) primary amido complexes Co{N(H)Ar(iPr6)}2, Co{N(H)Ar(Me6)}2, Ni{N(H)Ar(iPr6)}2 and Ni{N(H)Ar(Me6)}2 (Ar(Me6) = C6H3-2,6(C6H2-2,4,6-Me3)2, Ar(iPr6) = C6H3-2,6(C6H2-2,4,6-(i)Pr3)2) are described. The investigations showed that they exhibit interesting magnetic behavior. The bent versus linear geometries of the complexes enable direct observation of the effects of orbital angular momentum quenching upon bending the metal coordination geometry. The electronic configuration of the linear cobalt(II) complexes does not predict first order orbital angular momentum and yet, the magnetic moment of Co{N(H)Ar(iPr6))2 is much higher than the spin only value which suggests a large spin-orbit coupling effects due to mixing of the ground and excited states. In Chapter 3, the synthesis and characterization of the mononuclear chromium, iron, cobalt and nickel terphenyl substituted thiolate complexes Cr(SAr(Me6))2, Cr(SAr(iPr4))2, Fe(SAr(iPr4))2, Co(SAr(iPr4))2 and Ni(SAr(iPr4))2 are described. Their structures show bent coordination geometries of varying degree with strong secondary M-[eta]6 and M-C(ipso) flanking aryl ring interactions of ca. 2.153 [Angstrom] for Fe(SAr(iPr4))2, ca. 1.625 [Angstrom] for Co(SAr(iPr4))2 and ca. 1.731 [Angstrom] for Ni(SAr(iPr4))2. This observation is in sharp contrast to the almost linear coordination observed for the derivatives of the related but more crowded terphenyl thiolate ligand, SAr(iPr6), in M(SAr(iPr6))2 complexes where M = Cr, Fe, Co and Ni and the strictly linear geometry observed for the terphenyloxo analogs M(OAr(iPr4))2 where M = Fe and Co. Magnetic moments for these species are, in general, lower than the spin-only values. Expect for chromium, this is an unexpected observation for late transition metal low-coordinate complexes. The suppression of magnetic moments is most like due to the strong M-arene interactions which effectively increases the coordination number at the metal atom. These results demonstrate the important role that substituents play on the flanking rings of the terphenyl ligands and begs further investigations involving the role of dispersion in the isolation of low coordination mononuclear transition metal complexes. The divalent silylamides M{N(SiMe3)2}2 (M = Mn, Fe, and Co) are key synthons for low-coordinate transition-metal derivatives. In Chapter 4, the previously reported, but incorrectly characterized cobalt(II) silylamide, [Co{N(SiMe3)2}2]2 has been spectroscopically and magnetically characterized for the first time. In addition, the new Lewis base complexes [Co{N(SiMe3)2}2(PMe3)], and [Co{N(SiMe3)2}2(THF)], as well as a previously reported complex [Co{N(SiMe3)2}2(py)] were isolated and characterized. Magnetic studies showed that they had considerably larger magnetic moments than the spin-only value of 3.87 [mu](B), which is indicative of a significant zero-field splitting and g-tensor anisotropy. In addition to their interesting magnetic behavior and unexpectedly large D values in the range of -20 to -80 cm−1. The electronic spectrum of [Co{N(SiMe3)2}2]2 in solution showed that earlier characterization spectra of "Co{N(SiMe3)2}2" match that of the bright green THF adduct and not the dark brown cobalt dimer [Co{N(SiMe3)2}2]2. In Chapter 5, it is shown that the reaction of the versatile cobalt(II) amide, [Co{N(SiMe3)2}2]2, with four equivalents of the sterically crowded terphenyl phenols, HOAr(Me6) and HOAr(iPr4) (Ar(iPr4) = C6H3-2,6(C6H3-2,6-(i)Pr2)2) produced the first well-characterized, monomeric two-coordinate cobalt(II) bisaryloxides, Co{OAr(Me6))2 and Co(OAr(iPr4))2. Not only are these very rare examples of two-coordinate transition metal(II) aryloxides, but the magnetic moments of both the linear and the bent species were well in excess of the spin only value for cobalt(II) ion. It was demonstrated that careful manipulation of the synthetic conditions for Co(OAr(iPr4))2 could produce varying occupancies of the cobalt(II) site and that after weighting the magnetic susceptibilities of the compounds accordingly, the moments were shown to be in close agreement with each other. Chapter 6 reports the synthesis of the unstable nickel(II) bis(silylamide) complex Ni{N(SiMe3)2}2 via the reaction of NiI2 and two equivalents of NaN(SiMe3)2 in tetrahydrofuran, as well as two of its Lewis base adducts, Ni{N(SiMe3)2}2(THF) and Ni{N(SiMe3)2}2(py)2. The reaction of two equivalents of LiN(SiMe3)2 with NiCl2(DME) in tetrahydrofuran afforded the reduced homoleptic tetrameric nickel(I) amide complex, [Ni{N(SiMe3)2}]4. This unique polymetallic structure having a Ni4N4 planar array has four S = 1/2 nickel (I) ions and an antiferromagnetic exchange coupling constant of J = -102(2) cm−1. This study provides strong evidence that the formation of nickel(II) and nickel(I) amido complexes is possible without the use of sterically demanding ligand sets.

Download or read book Inorganic Syntheses Volume 35 written by and published by John Wiley & Sons. This book was released on 2010-08-13 with total page 221 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Inorganic Syntheses series provides all users of inorganic substances with detailed and foolproof procedures for the preparation of important and timely compounds. Includes complete, up-to-date procedures involving important inorganic substances Contains subject, contributor, and formula indexes

Download or read book Inorganic Syntheses written by Philip P. Power and published by John Wiley & Sons. This book was released on 2018-07-04 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt: The newest volume in the authoritative Inorganic Syntheses book series provides users of inorganic substances with detailed and foolproof procedures for the preparation of important and timely inorganic and organometallic compounds that can be used in reactions to develop new materials, drug targets, and bio-inspired chemical entities.

Download or read book The Chemistry of Iron Cobalt and Nickel written by D. Nicholls and published by Elsevier. This book was released on 2013-10-02 with total page 201 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Chemistry of Iron, Cobalt and Nickel deals with the chemistry of iron, cobalt, and nickel and covers topics ranging from the occurrence and distribution of all three elements to their properties, allotropy, and analytical chemistry. Compounds of iron, cobalt, and nickel in both low and high oxidation states are also discussed. This book is divided into three sections and begins with the history of iron, along with its occurrence and distribution, allotropy, and preparation and industrial production. The nuclear, physical, and chemical properties of iron, as well as the biological importance of iron compounds, are also considered. Compounds of iron are discussed, including carbonyls and nitric oxide complexes. The next two sections deal with the history, occurrence and distribution, allotropy, analytical chemistry, and preparation and industrial production of cobalt and nickel, along with their nuclear, physical, and chemical properties. Compounds of cobalt and nickel are examined, from carbonyls and nitrosyls to cyanides and organometallic compounds. This monograph will be a useful resource for inorganic chemists.

Download or read book Synthesis Characterization and Reactivity Studies of Low coordinate Late Transition Metal Complexes and the Preparation and Characterization of a Low coordinate Samarium Complex written by Pei Zhao and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Comprehensive Coordination Chemistry II written by J. A. McCleverty and published by Newnes. This book was released on 2003-12-03 with total page 11845 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comprehensive Coordination Chemistry II (CCC II) is the sequel to what has become a classic in the field, Comprehensive Coordination Chemistry, published in 1987. CCC II builds on the first and surveys new developments authoritatively in over 200 newly comissioned chapters, with an emphasis on current trends in biology, materials science and other areas of contemporary scientific interest.

Download or read book Low Valent Iron and Cobalt Isocyanide Complexes written by Charles Cameron Mokhtarzadeh and published by . This book was released on 2017 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes the targeted attempts at the generation of transition metal species that function as precise electronic structure mimics to the well known spin triplet (S =1) metal carbonyls fragments Fe(CO)4 and CpCo(CO). These unsaturated fragments have been shown to display a wide range reactivity, and competency towards important reaction chemistry such as alkane and N2 binding, and E-H bond activation due to a unique interplay of a strong ligand field, formal dn count, and orbital symmetry, rendering these fragments primed for bond activation. Accordingly, ligand architectures that can accurately mimic the ligand field provided by CO to kinetically stabilize these fragments could provide new inroads to novel small molecule activation pathways. To this end, sterically encumbering m-terphenyl isocyanides serve as isolobal ligand surrogates for carbon monoxide (CO). Additionally isocyanides have the added benefit of providing kinetic stabilization by virtue of readily tunable isocyano-R (CN-R) group. The first section of this dissertation describes the synthesis and protonation of an encumbered tetra-isocyanide iron dianion, Na2[Fe(CNArMes2)4] (ArMes2 = 2,6-(2,4,6 --Me3C6H2)2C6H3), which serves as a platform for targeting species of the formulation Fe(CNArMes2)4. It is shown that the reactivity of the electronically unsaturated Fe(CNR)4 fragment upon protonation of Na2[Fe(CNArMes2)4] and subsequent alkylation of Na[HFe(CNArMes2)4], yields the dinitrogen stabilized species Fe(N2)(CNArMes2)4. Fe(N2)(CNArMes2)4 is shown to readily undergo intramolecular C-H activation of the ligand scaffold upon liberation N2 under ambient conditions purportedly through and insipient [Fe(CNArMes2)4] fragment. Further more, ability of Na2[Fe(CNArMes2)4] to facilitate the reductive disproportionation of CO2, in addition to CO2 capture with electrophilic silyl sources is presented culminating in a rare class of low valent Fe-aminocarbyne complexes. The second vignette of this dissertation focuses on the generation of species that mimic the formulation CpCo(L). It is shown that with less encumbering m-terphenyl isocyanides that aggregation akin to the unsaturated carbonyl congeners is realized. Use of encumbering m-terphenyl isocyanides provides access to the three memebered electron transfer series [([mu]2-CNArMes2)2[CpCo]2]n (n = 0,-1, -2). Notably, this series is the first of its kind to span all three ostensible electronic states (e.g. d8-d8, d8-d9, and d9-d9), previously unavailable with other [pi]-acidic ligand frameworks. Additionally this allows for a systematic reassessment of the metal-metal bonding within this class of dimeric species. Evidence is put forth in favor of no M-M bonding interactions occur within these systems and the integrity of the dimeric framework is in fact mitigated through a unique interplay of the metal d-manifold and the isocyanide [pi]*-system. Modulation of the steric profile of the m-terphenyl isocyanide and the Cp unit to Cp* so as to increase the steric pressure provides access to the first reported mono-nuclear Cp*Co(N2)L fragments. It is shown that these species function as viable sources of Cp*Co(CNR) for a number of bond activation processes including Si-H, H-H, and P-P bond scission. Moreover, the reactivity of these species culminates with the isolation of the second example of a structurally authenticated transition metal nitrous oxide (N2O) adduct, which exhibits an unprecedented [eta]2-(N,N) coordination mode to Co. Finally, the reduction of the encumbered Cp*Co(CNArTripp2) (CNArTripp2 2,6-(2,4,6-(i-Pr)3C6H3)2C6H3) fragment provide access to the unique dianion K2[Cp*Co≡CNArTripp2]. It is shown that the dianion K2[Cp*Co≡CNArTripp2] exhibits 3-fold bonding between Co and the isocyanide -Ciso through an extreme case of M-->(CN) [pi]*-back donation and gives rise to the first example of a Co-carbyne complex. The reactivity and electronic structure are presented for K2[Cp*Co≡CNArTripp2] and it is concluded that this reactive dianion behaves as a potent metal based nucleophile and source of [Cp*Co(CNR)]2- for a number of bond activation process.

Download or read book Facilitating Multi electron Reactivity at Low coordinate Cobalt Complexes Using Redox active Ligands written by Aubrey L. Smith and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this study, we describe a detailed investigation of cobalt complexes containing redox-active ligands. We have prepared an electronic series of the complex in three oxidation states: [CoIII(ap)2]-, CoIII(isq)(ap), and [CoIII(CH3CN)(isq)2]+. Characterization shows that the metal center remains cobalt(III) through the redox changes and indicates that the oxidation state changes occur with gain or loss of electrons from the ligand set. While CoIII(isq)(ap) reacts with halide radicals to form a new cobalt-halide bond in a single electron reaction, [CoIII(ap)2]- appears to be prone to multi-electron reactivity in reactions with sources of "Cl+". Both reactions occur with electrons derived from the ligand set. Mechanistic studies suggest a single, two electron step is responsible for the bond-formation. Similarly, [CoIII(ap)2]- reacts with alkyl halides to pseudo-oxidatively add the alkyl at the cobalt center. The product of the reaction can be isolated and fully characterized and was found to be best assigned as CoIII(alkyl)(isq)2. This assignment indicates that the reaction occurs, again, with the new bond formed with two electrons formally derived from the ligand set and with no change in oxidation state at the metal center. Mechanistic investigations of the pseudo-oxidative addition suggest the reaction is SN2-like. The reaction occurs with a wide scope of alkyl halides, including those containing beta-hydrogens. : The cross-coupling reaction of CoIII(alkyl)(isq)2 with RZnX forms a new carbon-carbon bond. Similarly, the two electron oxidized complex [CoIII(CH3CN)(isq)2]+ reacts with organozinc reagents to couple two carbon nucleophiles and form a new carbon-carbon bond. Both reactions are successful with both sp2 and sp3 carbons. When followed substoichiometrically, the homocoupling reaction can be observed to form CoIII(alkyl)(isq)2. This indicates that the homocoupling and cross-coupling reactions proceed by the same mechanism. However, both reactions have low yields. The yield of the reactions are decreased by steric bulk of the alkyl or aryl fragments or around the metal center created by substituents on the ligand. Also, while the steric congestion disfavors the addition of the first alkyl fragment, the addition of the second alkyl fragment and subsequent rapid elimination of the coupling product is almost completely inhibited. This result also implies that the coupling of the two alkyl fragments is entirely inner-sphere requiring installation of both for coupling.

Download or read book Coordination Chemistry of Manganese Iron Cobalt and Zinc Complexes Bearing Pentadentate Ligands and Their Application in Oxidation Catalysis written by Michaela Grau and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Chemical Bonds written by Harry B. Gray and published by University Science Books. This book was released on 1994-12-05 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: This profusely illustrated book, by a world-renowned chemist and award-winning chemistry teacher, provides science students with an introduction to atomic and molecular structure and bonding. (This is a reprint of a book first published by Benjamin/Cummings, 1973.)

Download or read book Steric and Electronic Effects of the beta diketiminate Ligand on Low coordinate Iron Complexes written by Sarina M.. Bellows and published by . This book was released on 2014 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This work focuses on the steric and electronic effects of the [beta]-diketiminate ligand when coordinated to iron. Smaller [beta]-diketiminates were used in comparison to their bulkier analogues. The effects of the [beta]-diketiminate on iron complexes and their reactivities were investigated by density function theory studies, kinetic studies, and by comparing spectroscopic data to analogous compounds. Chapter 1 introduces the various [beta]-diketimines and their synthetic preparations. This supporting ligand can provide a range of steric hindrance which has resulted in differences in reactivity of the iron complexes. The few studies of [beta]-diketimines with electron withdrawing groups are discussed in detail to understand the current knowledge of electronic effects of the [beta]-diketiminate ligand. Chapter 2 describes the DFT study of [beta]-hydride elimination via high-spin iron(II)- and cobalt(II)-alkyl complexes. For these high-spin complexes to acquire the empty d orbital necessary for [beta]-hydride elimination a spin flip must occur to access a lower spin state. In the iron(II)-alkyl and cobalt(II)-alkyl complexes, a spin crossover mechanism was calculated to occur in order to obtain the lowest energy transition state through a lower spin state than the starting alkyl complex. This study has also given insight into an iron(II) complex that is resistant to [beta]-hydride elimination due to the steric hindrance of the ligand. Chapter 3 describes the synthesis of a ([beta]-diketiminate)iron(I) dimer and a ([beta]-diketiminate)iron(III)-imido dimer. The imido complex was formed by the N=N bond cleavage of the azobenzene substrate. Kinetic and DFT studies were performed to elucidate the mechanism of N=N bond cleavage. Chapter 4 describes two new synthetic routes to a new [beta]-diketiminate ligand with trifluoromethyl groups as electron withdrawing substituents. This ligand was used to produce low-coordinate iron complexes analogous to previously published complexes without an electron withdrawing [beta]-diketiminate ligand as an effort to ascertain the electronic effects of the [beta]-diketiminate ligand on the iron and the other coordinated ligands"--Pages viii-ix.

Download or read book The Coordination Chemistry of Thioether supported Low valent Cobalt Complexes written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The tridentate S3- donor ligand, phenyltris((tert-butylthio)methyl)borate, [PhTttBu]-, has been used to investigate the coordination chemistry of cobalt. A series of coordinatively and electronically unsaturated organocobalt(II) complexes [PhTttBu]Co(R) (R = CH3, CH2CH3, C6H5, CH2C6H5, C3H5) was synthesized through reaction of the starting material [PhTttBu]COCl, with the appropriate Grignard reagent. The resultant pseudotetrahedral complexes (allyl derivative is square pyramidal) proved to be both air and moisture sensitive. The complexes were characterized spectroscopically and crystal lographically. The small molecule reactivity of these complexes was assayed through reactions with CO and NO. The former reagent showed sensitivity to the identity of the organocobalt while the latter gave rise to the same product, regardless of the organic ligand. When R = CH3, CH2CH 3, C6H5, reaction of [PhTttBu]Co(R) with CO yielded red, five-coordinate [PhTttBu]Co(CO)(C(O)R). These square-pyramidal complexes contain apical thioether ligation with the remaining four ligands in the basal plane. Alternatively, when R = CH 2C6H5, C3H5, reaction with CO resulted in Co-C bond homolysis with formation of the brown Co(I) complex, [PhTtBu]Co(CO)2. In all cases, reaction of the organocobalt(II) complexes with NO resulted in the formation of the & kappa;2-dinitrosyl complex, [& kappa;2-PhTttBu]Co(NO)2. These results were confirmed both spectroscopically and crystallographically. A series of cobalt(I) phosphine complexes, [PhTttBu ]Co(PR3), PR3 = PMe3, PEt3, PMe2Ph, PMePh2, PPh3, P(OPh3), was prepared by reduction of [PhTttBu]COCl in the presence of the phosphine. These four-coordinate complexes were characterized spectroscopically and crystal lographically. The structures may be grouped into two classes, pseudo-tetrahedral and cis-divacant (i.e. an octahedron where two cis ligands have been removed, & alpha; = 54.7° for this complex; a & alpha; is the degree to which L lies off of the linear vector). The former class, for which PR 3 = PMe3, PEt3, PMe2Ph, the phosphine donor resides approximately on the B ... Co vector. The latter class, for which PR3 = PMePh2, PPh3, P(OPh) 3, the phosphine is significantly 'off-axis.' These complexes exhibited varying a angles allowing for insight into the structural choice of the complex based on the & sigma;-donating and & pi;-accepting properties of the phosphine donor. The cobalt and nickel isocyanide complexes, [PhTttBu]M(CNBu t) are readily alkylated with MeI, leading to the corresponding cationic iminoacyl complexes, [[PhTttBu]M(C(Me)NBut)]I.

Download or read book Organometallic Compounds of Low Coordinate Si Ge Sn and Pb written by Vladimir Ya. Lee and published by John Wiley & Sons. This book was released on 2011-07-22 with total page 390 pages. Available in PDF, EPUB and Kindle. Book excerpt: Until recently the low-coordinate compounds of the heavier elements of group 14 were known only as transient, unstable species which were difficult to isolate. However recent developments have led to the stabilisation of these compounds and today heavier group 14 element cations, radicals, anions, carbene analogues, alkene and alkyne analogues and aromatics have all been prepared as highly reactive, stable, fully characterizable and readily available organometallic reagents. Organometallic Compounds of Low-Coordinate Si, Ge, Sn and Pb describes the chemistry of this exciting new class of organometallics, with an emphasis on their major similarities and differences with the analogous species in organic chemistry. Topics covered include include the synthesis, structure, reactions and synthetic applications of : Si-, Ge-, Sn and Pb-centered cations, radicals and anions heavy analogues of carbenes: silylenes, germylenes, stannylenes and plumbylenes heavy analogues of alkenes: disilenes, digermenes, distannenes, diplumbenes heavy analogues of alkynes: disilynes, digermynes, distannynes, diplumbynes, and their valence isomers heteronuclear derivatives: silenes, germenes, stannenes, silagermenes, silastannenes, germastannenes heavy analogues of alkenes of the type: >E14=E13-, >E14=E15-, >E14=E16 [where E13, E14, E15 and E16 are elements of the groups 13, 14, 15 and 16] cyclic compounds (three-, four-, five-, and six-membered rings) heavy analogues of 1,3-dienes, allenes and other cumulenes heavy analogues of aromatic compounds; including a comparison between organometallic and organic aromaticity Organometallic Compounds of Low-Coordinate Si, Ge, Sn and Pb is an essential guide to this emerging class of organometallic reagents for researchers and students in main group, organometallic, synthetic and silicon chemistry

Download or read book The Chemistry of Coordination Complexes and Transition Metals written by P.L. Soni and published by CRC Press. This book was released on 2021-05-13 with total page 403 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers all important nomenclature, theories of bonding and stereochemistry of coordination complexes. The authors have made an effort to inscribe the ideas knowledge, clearly and in an interesting way to benefit the readers. The complexities of Molecular Orbital theory have been explained in a very simple and easy manner. It also deals with transition and inner transition metals. Conceptually, all transition and inner transition elements form complexes which have definite geometry and show interesting properties. General and specific methods of preparation, physical and chemical properties of each element has been discussed at length. Group wise study of elements in d-block series have been explained. Important compounds, complexes and organometallic compounds of metals in different oxidation states have been given explicitly. Note: T&F does not sell or distribute the Hardback in India, Pakistan, Nepal, Bhutan, Bangladesh and Sri Lanka.

Download or read book Synthesis Characterization and Reactivity of Transition Metal Complexes Supported by Heteropolydentate Ligation written by Adam Ruddy and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: