Multistep migration

Polymerization reaction of isocyanides RNC is catalyzed by [Fecp(CH2Ph)(CO)]. It proceeds as a result of multistep migration to coordinated ligands and is evidenced by the isolation and identification of the tris(imino) complex (9.164). " ... 

In Sections 7.3 and 7.4, the temperature dependence of radiationless transitions and the effect of deuteration on the lifetimes of excited electronic states are examined. In Section 7.5, a contribution to time-resolved spectroscopy is presented. In that section, we will discuss a problem dealing with transport phenomena of electronic excitations in doped molecular crystals. The theory of singlet excitation energy transfer uses an effective Hamiltonian to account for intramolecular excited-state depopulation and energy transfer by multistep migration among guest molecules. 

Figure 1. Schematic representation of the artificial photosynthetic reaction center by a monolayer assembly by A-S-D triad and antenna molecules for light harvesting (H), lateral energy migration and energy transfer, and charge separation across the membrane via multistep electron transfer (a) Side view of mono-layer assembly, (b) top view of a triad surrounded by H molecules, and (c) energy diagram for photo-electric conversion in a monolayer assembly.

In this proposed process, p-hydride elimination first yields a putative hydride olefin rc-complex. Rotation of the -coordinated olefin moiety about its co-ordination axis, followed by reinsertion produces a secondary carbon unit and therefore a branching point. Consecutive repetitions of this process allows the metal center to migrate down the polymer chain, thus producing longer chain branches. Chain termination occurs via monomer assisted p-hydrogen elimination, either in a fully concerted fashion as illustrated in Figure 2b or in a multistep associative mechanism as implicated by Johnson1 et al. 

Syntheses of simple diols are described first, followed by a multistep synthesis of ribose. These syntheses illustrate the compatibility of alkoxy substituents on boronic esters with their reaction with (dihalomethyl)lithium. The limitations of this compatibility, as well as failure of a (chloro-allyl)boronic ester to undergo substitution by alkoxides, are also noted. Retention of configuration of the migrating group is a consistent and repeated feature of these syntheses. 

A multistep pathway analogous to the mechanism of alkene hydrogenation has been shown to be operative in the rhodium-catalyzed hydroboration of alkenes.363 Deuterium labeling studies furnished evidence that the reversibility of the elementary steps is strongly substrate-dependent. The key step is hydride rather than boron migration to the rhodium-bound alkene. 

Impedance spectroscopy is a helpful means for studying both the bulk transport properties of a material and the electrochemical reactions on its surface. The importance of impedance spectroscopy arises from the efficacy of the methodology in separating individual reaction-migration paces into a multistep process, since each reaction or migration step has, ideally, a single time constant related with it consequently, each step can be separated in the frequency domain ... 

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