Copper clusters, polynuclear

Amino acid is one of the most important biological ligands. Researches on the coordination of metal-amino acid complexes will help us better understand the complicated behavior of the active site in a metal enzyme. Up to now many Ln-amino acid complexes [50] and 1 1 or 1 2 transition metal-amino acid complexes [51] with the structural motifs of mononuclear entity or chain have been synthesized. Recently, a series of polynuclear lanthanide clusters with amino acid as a ligand were reported (most of them display a Ln404-cubane structural motif) [52]. It is also well known that amino acids are useful ligands for the construction of polynuclear copper clusters [53-56], Several studies on polynuclear transition metal clusters with amino acids as ligands, such as [C03] [57,58], [Co2Pt2] [59], [Zn6] [60], and [Fe ] [61] were also reported. 

In the extreme class III behaviour,360-362 two types of structures were envisaged clusters and infinite lattices (Table 17). The latter, class IIIB behaviour, has been known for a number of years in the nonstoichiometric sulfides of copper (see ref. 10, p. 1142), and particularly in the double layer structure of K[Cu4S3],382 which exhibits the electrical conductivity and the reflectivity typical of a metal. The former, class IIIA behaviour, was looked for in the polynuclear clusters of copper(I) Cu gX, species, especially where X = sulfur, but no mixed valence copper(I)/(II) clusters with class IIIA behaviour have been identified to date. Mixed valence copper(I)/(II) complexes of class II behaviour (Table 17) have properties intermediate between those of class I and class III. The local copper(I)/(II) stereochemistry is well defined and the same for all Cu atoms present, and the single odd electron is associated with both Cu atoms, i.e. delocalized between them, but will have a normal spin-only magnetic moment. The complexes will be semiconductors and the d-d spectra of the odd electron will involve a near normal copper(II)-type spectrum (see Section 53.4.4.5), but in addition a unique band may be observed associated with an intervalence CuVCu11 charge transfer band (IVTC) (Table 19). While these requirements are fairly clear,360,362 their realization for specific systems is not so clearly established. 

Cluster Compounds Inorganometalhc Compounds Containing Transition Metal Main Group Elements Copper Inorganic Coordination Chemistry DinuclearOrganometal-lic Cluster Complexes Polynuclear Organometalhc Cluster Complexes Silver Inorganic Coordination Chemistry. 

Thiometallates (8) and Ta6Sn " serve as synthons, for instance, for the preparation of mixed-metal clusters involving iron or copper and silver, respectively. The discrete polynuclear TasSi/" and Nb4Se22 anions, prepared by traditional solid-state routes, have a structure related to that of polynuclear Mo oxysulfide anions. Nb-Cu chalcogenido clusters stabilized by phosphines could be prepared directly from NbCls (equation 8). The anion (9), for instance, is based on two CusNbSsCl heterocubane units linked by three /u.3-chlorine. ... 

Chalcogenides Solid-state Chemistry Copper Enzymes in Denitrification Copper Hemocyanin/Tyrosinase Models Copper Proteins Oxidases Copper Proteins with Dinuclear Active Sites Copper Proteins with Type 1 Sites Copper Proteins with Type 2 Sites Iron Sulfitf Models of Protein Active Sites Iron-Snlfiir Proteins Nickel Enzymes Cofactors Nickel Models of Protein Active Sites Polynuclear Organometallic Cluster Complexes. 

This topic has been reviewed by Ingledew (55). The major components of the respiratory chain for T. ferrooxidans are a cytochrome oxidase of the Ci type, cytochromes c, and the blue copper protein rusticyanin. Initial electron transfer from Fe(II) to a cellular component takes place at the outer surface of the plasma membrane in the periplasmic space. The rate of electron transfer from Fe(II) to rusticyanin is too slow for rusticyanin to serve as the initial electron acceptor. Several proposals have been made for the primary site of iron oxidation. Ingledew (56) has suggested that the Fe(II) is oxidized by Fe(III) boimd to the cell wall the electron then moves rapidly through the polynuclear Fe(III) complex to rusticyanin or an alternative electron acceptor. Other proposals for the initial electron acceptor include a three-iron-sulfur cluster present in a membrane-bound Fe(II) oxidoreductase (39, 88), a 63,000 molecular weight Fe(II)-oxidizing enzyme isolated from T. ferrooxidans (40), and an acid-stable cytochrome c present in crude extracts of T. ferrooxidans (14). 

No structurally characterized discrete Cu complexes are known. A few species have been observed in the gas phase, or at very low temperatures using matrix-isolation techniques, including polynuclear copper species such as Cu2 and Cu3 and several copper-carbon monoxide and copper-ethylene species. There have also been reports of reactive species thought to contain zerovalent copper, and several clusters or other species where, arguably, some of the Cu is present in the Cu oxidation state. ... 

While discrete two- and three-coordinate Cu(I) compounds have been reported, the favored coordination number of the metal is four. Quite frequently, two or more copper atoms will share ligands, resulting in the formation of polynuclear clusters. Complexes of stoichiometry CU4X4L4 (X = Cl, Br, I L = PR3, ASR3) for example, exist as tetrameric units whose structure depends upon the steric demands of X and R. In... 

This approach of using a combination of RSe-TMS and Se(TMS)2 for cluster synthesis should allow for the tailored functionalization of semiconductor nanoparticles. Recently, the ability to functionalize the surface of Cu2Se clusters has been demonstrated. The synthesis of l,l -bis(trimethyl-silyl)ferrocene, and its consequent reaction with CuOAc and excess phosphine has produced the polynuclear copper selenide cluster [Cug Fe(77 -C5H4Se)2 4(PPh2Et)4] (51) with surface redox-active ferrocene units that are intimately coupled to the cluster core (Figure 34). ... 

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