A literature review of modern transition-metal nanoclusters, with an emphasis on those nanoclusters which are catalytically active, is presented in two parts. Part One presents background information on transition-metal nanoclusters, including an overview of common synthetic routes, a description of how nanoclusters are stabilized, and a brief summary of the multiple characterization techniques used (and the type of information that they can provide). In Part Two, five specific nanocluster case studies are presented, case studies which compare and contrast the syntheses, characterization approaches, and catalytic applications of transition-metal nanoclusters.

A review of modern transition-metal nanoclusters: their synthesis, characterization, and applications in catalysis

Mono- and bimetallic colloidal particles have gained increasing attention in science and application throughout the last several years. In this contribution, we present a synopsis of the wet chemical syntheses of these materials and survey potential applications in catalysis and materials science. Methods for the characterization of these particles and their surfaces are not reviewed here.

Nanoscopic Metal Particles − Synthetic Methods and Potential Applications

This communication describes the Pd(OAc)2-catalyzed intermolecular amidation reactions of unactivated sp2 and sp3 C−H bonds using primary amides and potassium persulfate. The substrates containing a pendent oxime or pyridine group were amidated with excellent chemo- and regioselectivities. It is noteworthy that reactive C−X bonds were well-tolerated and a variety of primary amides can be effective nucleophiles for the Pd-catalyzed C−H amidation reactions. For the reaction of unactivated sp3 C−H bonds, β-amidation of 1° sp3 C−H bonds versus 2° C−H bonds is preferred. The catalytic reaction is initiated by chelation-assisted cyclopalladation involving C−H bond activation. Preliminary mechanistic study suggested that the persulfate oxidation of primary amides should generate reactive nitrene species, which then reacted with the cyclopalladated complex.

Intermolecular Amidation of Unactivated sp2 and sp3 C−H Bonds via Palladium-Catalyzed Cascade C−H Activation/Nitrene Insertion

This chapter offers a general review of selective methods for the oxidative conversion of C-H to C-N bonds Special focus has been given to the many disparate catalyst types that are capable of promoting this unique transformation

Metal-Catalyzed Oxidations of C–H to C–N Bonds

Compounds that contain a late transition metal-nitrogen multiple bond represent important reactive intermediate species in many useful organic and inorganic transformations. In order to understand the role that these intermediates play in reactions, it is important to have a full understanding of their electronic structure. This paper reviews the known structural motifs that occur in late transition metal nitrido and imido compounds, and provides a correlation between geometric structure and electronic structure. Also, intermediate species that have been postulated but not yet isolated are discussed, as these compounds represent exciting targets for further efforts in synthetic inorganic chemistry.

Terminal nitrido and imido complexes of the late transition metals

Giant palladium-561 clusters were found to be effective in catalysis of the oxidative carbonylation of phenol to diphenyl carbonate, conjugated with the reductive carbonylation and reduction of nitrobenzene under CO pressure.

Catalysis with a palladium giant cluster: phenol oxidative carbonylation to diphenyl carbonate conjugated with reductive nitrobenzene conversion

Giant cluster catalysis: possible intermediacy of nitrene and carbene species

most ways to compactly represent an audio signal use a frequency domain transition. When a complex representation of the evaluation coefficients using, it becomes necessary to determine the necessary accuracy of the formation of the phase assessment. It is believed that your fear is deaf to the phase. This is true when perceiving sounds with different initial phases. When evaluating the sound of the consonance, a multicomponent signal, a change in the relative phase positions of the spectral components is noticed by listeners. The results of the study will allow us to determine the necessary accuracy of estimating the phase of the spectral component in consonance, both during its evaluation and during processing, transmission and recording.

Noticeability of Phase Distortions in Consonanse

The main way to represent an audio signal in the frequency domain is the fast Fourier transform (FFT). When analyzing short signal sequences, the FFT often cannot provide the necessary resolution and accuracy in the formation of estimates of the amplitude and phase of the coefficients. The discrete cosine transform (DCT) is known and widely used, the coefficients of which are placed twice as often on the frequency scale. The disadvantage of DCT is the dependence of the estimate on the initial phase position of the signal; nevertheless, DCT is widely used to eliminate the statistical redundancy of signals. An algorithm for complex DCT is proposed that provides an increase in the resolution and accuracy of the estimate.

Algorithm for the Complex Discrete Cosine Transform

When eliminating the statistical and psychophysical redundancy of the sound signal presented in the frequency domain, the question about the expedient duration of the analyzed signal arises. Usually, a compromise is sought between the resolution and accuracy of spectral analysis, on the one hand, and the permissible duration of the analyzed discrete segment of the audio signal, on the other hand. It can be assumed that with the maximum elimination of redundancy, the signal will be reduced to one spectral component. In this case, the maximum duration of discrete segments of the signal will be determined by the appearance of a noticeable change in amplitude and frequency.

Tatiana V. Chernysheva

Papers

Catalysis with a palladium giant cluster: phenol oxidative carbonylation to diphenyl carbonate conjugated with reductive nitrobenzene conversion

Giant cluster catalysis: possible intermediacy of nitrene and carbene species

Noticeability of Phase Distortions in Consonanse

Algorithm for the Complex Discrete Cosine Transform

Recognizability of the Substitution of a Continuous Sound Signal by a Discretely Changing Sound Signal