Paradigm Shift from Alkaline (Earth) Metals to Early Transition Metals in Fluoroorganometal Chemistry: Perfluoroalkyl Titanocene(III) Reagents Prepared via Not Titanocene(II) but Titanocene(III) Species

2014 ◽  
Vol 20 (8) ◽  
pp. 2382-2386 ◽  
Author(s):  
Motohiro Fujiu ◽  
Ryota Hashimoto ◽  
Yuzo Nakamura ◽  
Kohsuke Aikawa ◽  
Shigekazu Ito ◽  
...  
Keyword(s):  
Transition Metals ◽  
Paradigm Shift ◽  
Alkaline Earth ◽  
Alkaline Earth Metals ◽  
Early Transition

scholarly journals Molecular Orbital Calculation of Lead-Free Perovskite Compounds for Efficient Use of Alkaline and Alkaline Earth Metals

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 956
Author(s):  
Naohisa Takesue ◽  
Jun-ichi Saito
Keyword(s):  
Transition Metals ◽  
Molecular Orbital ◽  
Alkali Metals ◽  
Alkaline Earth ◽  
Molecular Orbital Calculation ◽  
The Body ◽  
Alkaline Earth Metals ◽  
Lead Free ◽  
Covalent Bonds ◽  
Alkaline Earth Metal Ions

The effective ionic charges of lead-free perovskite dielectric complex compounds were investigated with molecular orbital calculation. The base model was a double perovskite cluster that consisted of octahedral oxygen cages with a transition metal ion of titanium, niobium, or zirconium located at each of their centers, and alkali and/or alkaline earth metal ions located at the body center, corners, edge centers, or face centers of the cluster. The results showed significant covalent bonds between the transition metals and the oxygens, and the alkali metals, especially sodium and oxygen. On the other hand, the alkaline earth metals have weak covalency. Calculation was also performed with the replacement of some of the oxygens with chlorine or fluorine; such replacement enhances the covalency of the transition metals. These trends provide good guidelines for the design properties of lead-free perovskite piezoelectrics based on ubiquitous sodium use.

scholarly journals The effect of metal ions on the reaction of hydrogen peroxide with Kraft lignin model compounds

1999 ◽  
Vol 77 (5-6) ◽  
pp. 667-675 ◽  
Author(s):  
Yujun Sun ◽  
Michael Fenster ◽  
Annie Yu ◽  
Richard M Berry ◽  
Dimitris S Argyropoulos
Keyword(s):  
Hydrogen Peroxide ◽  
Transition Metals ◽  
Oxalic Acid ◽  
Alkaline Earth ◽  
Alkaline Earth Metals ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Peroxide Bleaching ◽  
Radical Coupling ◽  
Lignin Model

Peroxide bleaching is significantly affected by transition and alkaline earth metals. Isolating the effects of different transition and alkaline earth metals on the reactions of peroxide with different representative lignin structures allows the separation of the positive from the negative contributions of these metal ions. In this work, five monomeric or dimeric phenolic lignin model compounds were treated with alkaline hydrogen peroxide in the absence or presence of Mn2+, Cu2+, Fe3+, and Mg2+. We followed the disappearance of the starting material and the progress of demethylation, radical coupling and oxalic acid formation were followed. Transition metals increased the reactivities of all the lignin model compounds with hydrogen peroxide in the order Mn2+ > Cu2+ > Fe3+, which is the same as the order of activity toward peroxide decomposition while Mg2+ stabilized the system. Demethylation, radical coupling, and oxalic acid formation were all increased by the presence of transition metals in the system and decreased by the addition of Mg2+. The acceleration of the total degree of reaction and of the demethoxylation reactions improves peroxide bleaching, but the increase in the radical coupling reactions can affect the further bleachability of pulp while the increase in the formation of oxalic acid could lead to a greater probability of scaling.Key words: lignins, hydrogen peroxide, peroxide bleaching, reactivity, chemical pulps, metal compounds, alkali treatment, transition metals, delignification.

The activities of evaporated metal films in gas chemisorption

1953 ◽  
Vol 218 (1135) ◽  
pp. 566-577 ◽  
Keyword(s):  
Transition Metals ◽  
Alkaline Earth ◽  
Metal Films ◽  
Alkaline Earth Metals ◽  
Light Metals ◽  
Covalent Bonds ◽  
Catalytic Systems ◽  
Single Exception ◽  
Electron Donation

The interaction of N 2 , H 2 , CO, C 2 H 4 , C 2 H 2 and O 2 with clean evaporated films of some twenty metals has been investigated between 0 and – 183° C. The results are expressed as gas chemisorbed or gas not chemisorbed. O 2 chemisorption is universal among all the metals studied, with the single exception of Au. Chemisorption of N 2 and H 2 is limited to transition metals and alkaline earth metals, and chemisorption of CO, C 2 H 4 and C 2 H 2 to these and to Al, Cu and Au. O 2 chemisorption is believed to take place with formation of O 2- ions at the surface, with electron donation from the s and p bands of the metals. The inactivity of Au towards O 2 is, however, only partly understandable in terms of this mechanism . The remaining five gases are believed to form covalent bonds with the metal d bands in chemisorption; with Cu and Au it is suggested that d – s promotion takes place in the act of chemisorption to allow such covalence. Al is exceptional, and with the light metals, s and p band electrons may be active in chemisorption: a further exception is the interaction of K with C 2 H 2 . Some applications of these results to catalytic systems are discussed.

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