Copper mechanistic aspects

O Sullivan describes the fundamental theory, mechanistic aspects and practical issues associated with autocatalytic electroless metal deposition processes. Current approaches for gaining fundamental understanding of this complex process are described, along with results for copper, nickel and various alloys. Emphasis is placed on microelectronic applications that include formation of structures that are smaller than the diffusion layer thickness which influences structure formation. 

Structural and Mechanistic Aspects of Copper Catalyzed Atom Transfer Radical Polymerization... 

ATRP, other factors, such as solvent and temperature, must also be taken into consideration. Typical monomers and alkyl halide initiators that are used in ATRP are shown in Scheme 5 [47], The copper complex is perhaps the most important component of this catalytic system because it regulates the dynamic equilibrium between dormant and active species. In this article, structural and mechanistic aspects of copper-catalyzed ATRP are discussed. 

Mechanistic Aspects of the Electrochemical Reduction of Carbon Monoxide and Methanol to Methane at Ruthenium and Copper Electrodes... 

More than 60 years after its simultaneous discovery by Rochow and Muller, the direct reaction of copper-activated silicon with alkyl chlorides is arguably still the most important industrial process for the preparation of basic organosilanes. An inspiring historic account highlighting the significance of this seminal work has been given by Seyferth.12 A comprehensive review on the subject has been written by Jung and Yoo.13 The most recent work associated with the direct process is concerned with the role of metallic promoters, such as Zn and Cd, as well as mechanistic aspects.14... 

Fig. 5.53. Mechanistic aspects I of nucleophilic aromatic substitution reactions of aryldiazonium salts via radicals introduction of Nu=Cl, Br, CN or N02 according to Figure 5.52. Following step 2 there are two alternatives either the copper(II) salt is bound to the aryl radical (step 3) and the compound Ar-Cu(III)NuX decomposes to Cu(I)X and the substitution product Ar-Nu (step 4), or the aryl radical reacts with the cop-per(II) salt in a one-step radical substitution reaction yielding Cu(I)X and the substitution product Ar-Nu.

CopA of En. hirae could be expressed in Escherichia coli and purified to homogeneity by Ni-NTA affinity chromatography by means of an added histidine tag (Wunderh-Ye and Solioz, in press). Purified CopA has a pH optimum of 6.3 and a for ATP of 0.2 mM. The enzyme forms an acylphosphate intermediate, which is a hallmark of P- and CPx-type ATPases (Pedersen and Carafoh, 1987b). Purified CopA can now serve in the analysis of mechanistic aspects of copper transport and in the characterization of structure-function relationships. 

The results mentioned above prompted us to synthesize a more simplified catalyst, scandium tris(dodecyl sulfate) (Sc(DS)3) [23,24]. This new type of catalyst, Lewis acid-surfactant-combined catalyst (LASC) , was expected to act both as a Lewis acid to activate the substrate molecules and as a surfactant to form emulsions in water. Eng-berts and co-workers also reported a surfactant-type Lewis acid, copper bis(dodecyl sulfate) (Cu(DS)2) [25]. Although they studied detailed mechanistic aspects of Diels-Alder... 

Mechanistic aspects of the action of tyrosinase and the usual transduction schemes have been summarized on several occasions [166,170-173]. In short, this copper enzyme possesses two activities, mono- and di-phenolase. Due to the predominant presence of the mono phenolase inactive form (met-form), the enzyme is inherently inefficient for the catalysis of these monophenol derivatives. However, in the presence of a diphenol, the catalytic cycle is activated to produce quinones and the scheme results in an efficient biorecognition cascade. This activation is achieved more efficiently when combined with electrochemical detection through the reduction of the produced quinones [166], as illustrated in Fig. 10.5. Consequently, a change in the rate-hmiting step can be observed through kinetic to diffusion controlled sensors with a concomitant increase in stability and sensitivity, as depicted in Fig. 10.6. 

Mechanistic aspects of copper-catalyzed Grignard addition to a,/ -unsaturated carbonyl compounds have not attracted much attention, probably because of the complex nature of the reagent system [11], but it would resemble that of the 1,4-addition of stoichiometric or higher-order organocopper reagents that have been investigated extensively [15,18,223]. 

Since the area under review is large, we have not tried to cover catalysis by alloys or mixed oxides, neither have we attempted to review the extensive patent literature. Passing references have been made to industrial processes using copper and silver catalysts, but emphasis has been placed primarily on the scientific, and particularly the mechanistic, aspects of the systems involved. We have not hesitated to include non-catalytic work when we felt it contributed to the understanding of a particular catalytic phenomenon. 

In terms of kinetics and mechanisms, electroless deposition processes have many similarities. In an attempt to analyze the electroless deposition, several mechanisms such as atomic hydrogen, hydride ion, metal hydroxide, electrochemical, and universal have been proposed.1-3 It is important to note that these mechanisms were developed for cases of nickel and copper electroless deposition, which were the most widely studied metals in this respect. Based on the proposed mechanisms, most of the features of electroless deposition can be explained. However, there are some characteristics of electroless deposition, which cannot be explained using these mechanisms. The major problems arise when attempting to generalize the proposed models explaining the mechanistic aspects. 

Lei YB, Anson FC (1994) Mechanistic aspects of the electroreduction of as catalyzed by copper-phenanthroline complexes adsorbed on graphite-electrodes. Inorg Chem 33(22) 5003-5009... 

I 7 Mechanistic Aspects of Metai-Cataiyzecl C,C- and C,X-Bond Forming Reactions 1.1.3.8 Couplings Catalyzed by Copper and Cold... 

E. -i. Negishi, Selective Carbon-Carbon Bond Formation via Transition Metal Catalysis Is Nickel or Palladium Better Than Copper , in Aspects of Mechanistic and Organometallic Chemistry , ed. J. H. Brewster, Plenum Press, 1978, 285. 

Pintauer T, Matyjaszewski K. Structural and mechanistic aspects of copper catalyzed atom transfer radical polymerization. Top Oiganomet Chem 2009 26 221-251. 

Sambiagio C, Marsden SP, Blacker AJ, McGowan PC (2014) Copper catalysed Ullmann type chemistry from mechanistic aspects to modem development. Chem Soc Rev 43... 

The success of bis(oxazolines) (43) in the copper-catalyzed cyclopropanation reaction has prompted numerous researchers to modify these structures in an attempt to improve the catalysts. To date, none have approached the success and generality exhibited by /erf-butyl bis(oxazoline) (55c) although some afford improved selectivities in specific cases. As a corollary to its success in this reaction, the copper-catalyzed cyclopropanation has taken on the aspects of a testing ground for new bis(oxazoline)-based ligands. The plethora of publications in this area will be summarily condensed in the rest of this section, and emphasis will be placed only on those ligands that provide improvements over 55c and those publications that deal with structural or mechanistic advances. 

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