Metal complexes Fe

A wide variety of cyclopropenylium metal cations has been prepared and studied over the past two decades, ranging from main group elements (Li, Mg) through transition metal -complexes (Fe, Mn, Pd, Pt). Extensive NMR studies suggest that the metal carbene... 

Oxidative addition of Cl2CNPh with the low-valent metal complexes Fe(CO)5, [Fe(CO)4]2-, Pt(PPh3)4, and RhCl(PPh3)3 produced Fe(CO)4 CNPh, PtCl2(CNPh)PPh3, and RhCl3(CNPh)(PPh3)2 (107, 108). 

Diebold, A., Elbouadili, A., and Hagen, K.S. Crystal structures and solution behaviour of paramagnetic divalent transition metal complexes (Fe, Co) of the sterically encumbered tridentate macrocycles l,4,7-R3-l,4,7-triazacyclononane coordination numbers 5 (R = i-Pr) and 6 (R = /-Bu), Inorg. Chem. 39 (2000), 3915-3923. 

Although superoxide ion reacts with reduced transition metal complexes (Fe , Mn Co Fe (EDTA), Fe (TPP)) bi62 to give oxidized products, for simple solvated cations the reaction sequence is a Tewis acid catalyzed disproportionation (equation 155) with subsequent Fenton... 

The next group of methods to be considered represents a far more recent development than the Rosenmund the use of the anionic metal complexes [Fe(CO)4] , [HFe(CO)4] , [HCr(CO)s]", [HW(CO)5] and [CpV(CO)3H] . Although it is only the first of these reagents which is clearly a nonhydride reducing agent, they are all considered here because of their close structural relationship and because of possible mechanistic similarities vide infra). 

The double bond migration or cis-trans isomerization of linear pentenes catalyzed by a variety of transition metal complexes (Fe(CO)s, Fe3(CO)i2, Ru3(CO)i2) in the presence of irradiation illustrates the operation of case 1.3 [20, 21] (Scheme 3). Case 1.4, which covers photoinduced electron transfer... 

A. D. Bacon and M. C. Zerner, Theor. Chim. Acta, 53, 21 (1979). An Intermediate Neglect of Differential Overlap Theory for Transition Metal Complexes Fe, Co, and Cu Chlorides,... 

Bacon, A. D., Zemer, M. C. (1979). An intermediate neglect of differential overlap theory for transition metal complexes Fe, Co and Cu chlorides. Theor. Chim. Acta 53,21-54. Baird, N. C., Dewar, M. J. S. (1969). Ground states of a-bonded molecules. IV. The MINDO method and its apphcation to hydrocarbons. J. Chem. Phys. 50,1262-1275. Bal s, N. (1967). Formation of stable molecules within the statistical theory of atoms. Phys. Rev. 156,42 7. 

In CrOl, esters (ROCrO ), and metal complexes [Fe—OCrO ], tetrahedral coordination dominates. Octahedral activated states for reduction of Cr(VI) to Cr(IV) or Cr(III) and containing cis-dioxo ligands are postulated by analogy to stable complexes of cis-MoO (see Section VI.A.l.b). Mechanisms for substitution reactions on chromium(VI) postulate five-coordinate activated states. The potential for Cr(VI) to accept electrons increases as the number of electrons increases from one to three (Fig. 2). 

J. Ridley and M. Zerner, Theoret. Chim. Acta, 32, 111 (1973). An Intermediate Neglect of Differential Overlap Technique for Spectroscopy Pyrrole and the Azines A. D. Bacon and M. C. Zerner, Theoret. Chim. Acta, S3,21 (1979). An Intermediate Neglect of Differential Overlap Theory for Transition Metal Complexes Fe, Co, and Cu Chlorides W. D. Edwards and M. C. Zerner, Theoret. Chim. Acta, 72, 347 (1987). A Generalized Restricted Open-Shell Fock Operator. 

Aminoboranes have been used as ligands in complexes with transition metals (66) in one instance giving a rare example of two-coordinate, non-t/ transition-metal complexes. The molecular stmcture of the iron complex Fe[N(Mes)B(Mes)2]2 where Mes = is shown in Figure 1. The... 

Among the J ,J -DBFOX/Ph-transition(II) metal complex catalysts examined in nitrone cydoadditions, the anhydrous J ,J -DBFOX/Ph complex catalyst prepared from Ni(C104)2 or Fe(C104)2 provided equally excellent results. For example, in the presence of 10 mol% of the anhydrous nickel(II) complex catalyst R,R-DBFOX/Ph-Ni(C104)2, which was prepared in-situ from J ,J -DBFOX/Ph ligand, NiBr2, and 2 equimolar amounts of AgC104 in dichloromethane, the reaction of 3-crotonoyl-2-oxazolidinone with N-benzylidenemethylamine N-oxide at room temperature produced the 3,4-trans-isoxazolidine (63% yield) in near perfect endo selectivity (endo/exo=99 l) and enantioselectivity in favor for the 3S,4J ,5S enantiomer (>99% ee for the endo isomer. Scheme 7.21). The copper(II) perchlorate complex showed no catalytic activity, however, whereas the ytterbium(III) triflate complex led to the formation of racemic cycloadducts. 

Fe+ + has been deprotonated, but the reaction is complicated by further nucleophilic attack of the methylene unit with the starting material [17]. Enhanced acidity of the ring hydrogens in arene-metal complexes is shown [21] by the formation of complexes of alkyllithium by proton abstraction. 

On the basis of these results it seems to the present author that inner and outer complexes can reasonably be assumed for the electron transfer to the diazonium ion, but that an outer-sphere mechanism is more likely for metal complexes with a completely saturated coordination sphere of relatively high stability, such as Fe(CN) (Bagal et al., 1974) or ferrocene (Doyle et al., 1987 a). Romming and Waerstad (1965) isolated the complex obtained from a Sandmeyer reaction of benzenediazonium ions and [Cu B ]- ions. The X-ray structural data for this complex also indicate an outer-sphere complex. 

The Lewis bases attached to the central metal atom or ion in a d-metal complex are known as ligands they can be either ions or molecules. An example of an ionic ligand is the cyanide ion. In the hexacyanoferrate(II) ion, [Fe(CN)6]4, the CN- ions provide the electron pairs that form bonds to the Lewis acid Fe2+. In the neutral complex Ni(CO)4, the Ni atom acts as the Lewis acid and the ligands are the CO molecules. 

Name each of the following complex ions and determine the oxidation number of the metal (a) [Fe(CN)J4 ... 

Note Many of the (substituted hydrazino)quinoxalines covered in this section have been converted into metal complexes, randomly exemplified here. 2-(Pyridin-2-ylhydrazonomethyl)quinoxaline (246) Fe(ll), Ni(ll), and Cu(ll)... 

The iron complex Fe[P(OC8H5)3]2[(CgH40)P(OC6H5)2]2 has been synthesized by metal-atom evaporation-techniques (190). The complex is, formally, the result of two ortho-oxidative, C-H additions, accompanied by loss of a molecule of H2. 

The use of metal-complex initiating systems proved to be especially promising in carrying out the reactions with acrylic monomers which can be easily polymerized, when the common initiators of radical reactions are excepted. The use of Fe(CO)s -I- DMFA system allows us to perform homolytical addition of bromoform to acrylic monomers selectively at C-Br bond with no essential polymerization (ref. 10). 

Thus, this first example of stereoselective radical reaction, initiated with the system based on Fe(CO)5, shows opportunities and prospects of using the metal complex initiators for obtaining the stereomerically pure adducts of bromine-containing compounds to vinyl monomers with chiral substituents. 

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