Transition metal ions structure

Perovskite-related oxides of the K2MF4 (A2BO4+J B-transition metal ion) structure (Figure 16) have been investigated by several groups as alternative mixed conductors for SOFC. 

The specific feature of polymerization as a catalytic reaction is that the composition and structure of the polymer molecule formed show traces of the mechanism of the processes proceeding in the coordination sphere of the transition metal ion to which a growing polymer chain is bound. It offers additional possibilities for studying the intimate mechanism of this heterogeneous catalytic reaction. 

The determination of structural properties of dimeric transition metal ion complexes from e.p.r. spectra. T. D. Smith and J. R. Pilbrow, Coord. Chem. Rev., 1974, 13,173-278 (186). 

Some similar bimetallic acylamino complexes are also known with transition metal ions, e.g., with vanadium(II) [67], palladium(II) [68], and especially platinum(II) [69]. In the Cambridge Structural Database [39] only one trimetallic structure is found in which three iron(II) ions are bridged by a total number of six acylamino ligands [70]. 

Dioximes are widely used bidentate ligands for the complexation of transition metal ions with the characteristic property to form complexes with a pseudo-macrocyclic structure if two or more of these ligands are chelating the same metal ion (119, Fig. 31) [163]. 

Besides supported (transition) metal catalysts, structure sensitivity can also be observed with bare (oxidic) support materials, too. In 2003, Hinrichsen et al. [39] investigated methanol synthesis at 30 bar and 300 °C over differently prepared zinc oxides, namely by precipitation, coprecipitation with alumina, and thermolysis of zinc siloxide precursor. Particle sizes, as determined by N2 physisorpt-ion and XRD, varied from 261 nm for a commercial material to 7.0 nm for the thermolytically obtained material. Plotting the areal rates against BET surface areas (Figure 3) reveals enhanced activity for the low surface area zinc... 

Most complexes showing spin-state transitions are in fact of low symmetry. In order to describe their electronic structure it is convenient to employ term symbols appropriate to cubic symmetry and this practice will be followed below. The most common transition-metal ions for which spin-state transitions have been observed are Fe " (3d ), Fe " (3d ) and Co (3d ), a minor role being played by Co " (3d ), Mn " (3d ), as well as Cr " and Mn " (3d ). The relevant ground states for an octahedral disposition of the ligands are LS Ui,(t ,) and HS r2,(t ,e ) for iron(II), LS and HS Ai,(t, e ) for... 

Bond length differences between HS and LS isomers have been determined for a number of iron(II), iron(III) and cobalt(II) complexes on the basis of multiple temperature X-ray diffraction structure studies [6]. The available results have been collected in Table 17. Average values for the bond length changes characteristic for a particular transition-metal ion have been extracted from these data and are obtained as AR 0.17 A for iron(II) complexes, AR 0.13 A for iron(III) complexes, and AR = 0.06 A for cobalt(II) complexes. These values may be compared with the differences of ionic radii between the HS and LS forms of iron(II), iron(III) and cobalt(II) which were estimated some time ago [184] as 0.16, 0.095, and 0.085 A, respectively. 

Macrocycles attached to redox responsive groups such as ferrocene (78) can give selective transition metal ion receptors. The X-ray structure reveals a five-coordinate zinc with distorted square-pyramidal geometry bound to the four macrocycle nitrogens and an iodide. In the solid state the two ferrocenyl groups are positioned on the same side of the ligand with distances to the metal center of 5.347(7) and 6.120(8) A and these distances can be related to the redox behavior.689... 

Electron dot structures are not usually written for transition metal or inner transition metal atoms. They do lose electrons, forming ions. If you are asked to draw an electron dot diagram for a compound containing a monatomic transition metal ion, show the ion with no outermost electrons. 

Molecular hydrogen is rather unreactive at ambient conditions, but many transition and lanthanide metal ions are able to bind and therefore activate H2, which results in transformation into H (hydride) 11 (hydrogen radical) or H+ (proton), and subsequent transfer of these forms of hydrogen to the substrate.7,8 In this context, not only metal hydride but also dihydrogen complexes of transition metal ions, play a key role,9 10 especially since the first structural characterization of one of these species in 1984 by Kubas.11... 

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