Showing papers on "Reactivity (chemistry) published in 1983"

Cp 2 TiCH 2 complexes in synthetic applications

Abstract: The reactive 16e- species Cp_2Ti=CH_2 can be generated in situ from either its aluminum alkyl adducts or olefin adducts (metallacyclobutanes). This complex reacts with a wide variety of unsaturated functionalities including c=O, c=C,-c≡c- and –C≡N. In most instances the c:O groups are methylenated. Key to the utility of these complexes is their lack of basic properties in contrast with phosphorous ylides; all of the normal "Wittig" side reactions are eliminated using these reagents. Acid chlorides and anhydrides are converted into enolate complexes, which can be used in aldol type chemistry. The combination of the reactivity toward C=O and C=C results in an efficient method for the conversion of unhindered carbonyl centers into quarternary carbon centers.

The Activation of Carbon Dioxide by Metai Complexes

Abstract: Publisher Summary Chemistry of one-carbon-atom molecules (C 1 chemistry) is an important area of research for the organometallic chemist. The motivation for these efforts stems from the belief that the raw material base for commercial organic chemicals will shift from oil to coal, owing to both economic reasons and declining petroleum reserves. Prior to a discussion of CO 2 insertion reactions into M–H and M–C bonds, it is useful to review some of the known coordination chemistry of carbon dioxide, because the activation of CO 2 by metal centers is assumed to be of significance in most of these processes. In principle, the insertion of CO 2 into a transition-metal hydrogen bond can result in either M–O or M–C bond formation––that is, production of metalloformate or metallocarboxylic acid derivatives. Some very interesting work on the reversible insertion of carbon dioxide into palladium–carbon bonds has been reported recently by Braunstein and coworkers. The reactions of CO 2 , with metal –hydroxides, –alkoxides, and –amides to provide metallobicarbonates, –alkyl carbonates, and –carbarnates in general do not involve activation of carbon dioxide by prior coordination to the metal center. The use of carbon dioxide as an industrial source of chemical carbon has been limited mainly to the production of organic carbonates, carboxylic acids, and ureas. The chapter discusses recent literature relevant to the coordination chemistry of carbon dioxide and its use as a source of chemical carbon.

The mechanism and kinetics of hydride formation in Mg-10wt.%Ni and CeMg12

Abstract: The proposition that the apparent differences between the reactivities of magnesium and hydrogen are partially due to a lack of appreciation of the effects of various parameters on the kinetics is developed. The results of investigations of the formation-decomposition kinetics and morphology of CeMg12 and Mg-10wt.%Ni alloys performed at pressures and temperatures where only the formation of the MgH2 hydride is reversible support the hypothesis that the high reactivity of such alloys with hydrogen is due, at least partially, to the effects of morphological parameters such as mechanical stresses and strains and incoherent grain boundaries which increase hydrogen diffusion and hydride nucleation and which are produced by the formation of finely divided precipitates of CeH3 or Mg2Ni. The decrease in the hydrogen capacity on cycling is interpreted as a consequence of the removal of defects.

Synthesis, structure, and reactivity of monomeric two-coordinate copper(I) complexes

Abstract: Preparation et reactions de CuL 2 BF 4 avec L=emidazoles, pyrazoles et pyridines. Etude RX de Cu(MePz) 2 BF 4 et Cu(Me 3 Py) 2 BF 4

Mixtures of aromatic-aliphatic ketones as photoinitiators and photopolymerizable systems containing them

Abstract: Mixtures containing at least one hydroxyalkylphenone of the formula ##STR1## wherein R1 is H, alkyl of 1-4 C atoms or chlorine, R2 is H or methyl, R3 is H or methyl, R4 is alkyl of 1-6 C atoms and R5 is alkyl of 1-6 C atoms, and at least one 2-alkylthioxanthone of the formula ##STR2## wherein R6 is alkyl of 1-8 C atoms, have a considerably increased reactivity in initiating the photopolymerization of ethylenically unsaturated compounds. The polymers fully hardened using these initiator mixtures suffer only little yellowing.