Tri-metallic species

The ZnCl2 system has probably been studied in the most detail. Fast atom bombardment mass spectrometry (FAB MS) has been used to identify the species present. It was found that ZnCl3, Zn2Cl5 and Zn3Cl7 species are all present in the liquids. The relative proportions of anionic species depend on the ionic liquid composition. Lecocq et al. [108] used electrospray ionization to look at the various species present and found that in Lewis basic liquids x(ZnCl2) <0.5 ZnC -whereas the di- and tri-metallate species were more prevalent in Lewis acidic liquids. 

Our bi- and tri-metallic species are derived from precursor molecules that can be denuded (chemically) to expose only the mixed-metal constituent atoms. The nanoalloys that almost all others prepare are generally formed by methods that rely on sequential addition of separate solutions such as HAuCl and PdCl [35] to form Au-Pd nanoalloys. Moreover, such nanoalloys (like the metallic nanoparticles now in extensive use [45]) are utilized in their passivated form, which means that they have surfactant species such as poly(vinyl pyrrolidone), PVP, or poly-diaUyl dimethyl ammonium chloride (PDDA) covering their surfaces (The molecular weight of which may be as large as 450 kDa). Our nanoparticles are free from such surfactants or any other stabilizing molecular entity. 

Series of soluble bi- and tri-metallic species such as M [M(OR)6]n have been reported from reactions between the metal alkoxides or halides in alcohol solutions (e.g., see 284, 285 and refs, therein Section 4.5.2.4.4 below). They are of interest as precursors for sol-gel procedures. A number of oxo clusters have been described, apparently products of hydrolysis or oxidation. Pbn6Nb404(0Et)24 features an octahedral cluster [Pb6(//3-0)4(p3-0Et)4] whose faces are capped by the bridging ligands. The oxo ligands are also coordinated to Nb(OEt)5 groups.286... 

A number of thermal polyhedral rearrangements of 10-, 11-, and 12-vertex bimetallic cobaltocarbaboranes, Cp2Co2C2B H +2, have been studied. The rearrangements involved migration of Co, C, and B atoms on the polyhedral surface, and some new bi- and tri-metallic species were obtained. In addition, improved preparative routes to previously known systems were found. A typical rearrangement process is illustrated in Figure 20. 

Polynuclear compounds are obtained by reacting Pd(8-mq) compounds with carbonylmetallate anions. Depending upon the starting material used hetero di- or tri-metallic species are formed. 

Electron-rich olefins such as 36 have been used by Lappert in the synthesis of a great number of mono-, bis-, tris-, and tetrakiscarbene complexes from various transition metal species (62). Ru, Os, and Ir carbene complexes have been prepared from reactions with these olefins, e.g.,... 

Triorganovinylsilanes can be used as silylating reagents. In this case, the vinyl moiety functions as a hydrogen acceptor. The Ru3(CO)i2-catalyzed reaction of 3-acetylthiophene with trimethylvinylsilane affords 3-acetyl-2-(tri-methylsilyl)thiophene in 64% yield, as shown in Scheme 15.148 This reaction involves a /3-silyl elimination, yielding a metal species. 

An extensive range of compounds with homonuclear or heteronuclear single or double bonds between As, Sb, or Bi is known. They include the simple tetraorganodimetallic species, R2MMR2, double bonded species RM=MR, linear tri- and tetra-metallated species, and mono- or polycyclic compounds. In addition, adducts with coordinative metal-metal bonds are known.44-46 463 Examples for cationic species with Sb-Sb bonds are Me2SbSbMe2+ and... 

As with the corresponding silica supported species, hydrogen treatment at 150 °C for 15 h of (=SiO)Ta(CH2CMe3)2(=CHCMe3) furnishes [(=SiO)2TaHx] as a mixture of mono- and tris-hydride species (Scheme 2.16). Alternatively, a surface reorganization around the metal affords the second Ta-O bond and a =Si-H surface species. 

Lithium metal or alkyllithium derivatives react with dihalocyclopropanes to provide the corresponding lithiohalocyclopropanes I which are stable at temperatures around —100 °C. These metalated species are easily trapped with electrophiles (R—X) like methyl or ethyl iodide, trimethylstannyl chloride, tri-methylsilyl chloride etc. In the case of the unsaturated bicyclic substrate II a double bond migration is observed, which in the presence of excess starting bromide is accompanied by isomerization of the axo-lithio intermediate III to its endo-isomer IV [58],... 

Table II indicates the stoichiometry of the reaction of metal hydro-carbyls with the surface of silicas and aluminas dried at various temperatures. The results indicate that at lower drying temperatures approximately 2 moles of hydrocarbon are liberated per mole of hydrocarbyl compound. Subsequent reaction with the proton source, n-butyl alcohol, generates 1 or 2 moles of hydrocarbon, depending on whether a tris- or tetrahydrocarbyl compound is used. The formation of 2 moles of hydrocarbon can arise as a fortuitous combination of metal species singly, doubly, and triply bonded to the support surface.

These unique eight-coordinate complexes of the first-row transition metal ions maintain the four-membered chelate ring even in solution, where they dissociate into the tris-complex species.94 97... 

All the mononuclear species effect V(Co)6 in the above table satisfy the 18-electron rule. The bi and tri-nuclear species do also if (i) the two electrons in a metal-metal bond are counted as contributing to the valence shells of both metal atoms concerned, and (ii) a bridging CO contributes one electron to each metal. Monomeric Mn and Co carbonyls would have an odd number of electrons and dimerise in consequence. V(CO)6 is exceptional as a stable radical with 17 valence-shell electrons, presumably because it is satirically impossible for it to dimerise without losing one CO ligand. It does, however, readily form the 18-electron anion [V(CO)6]-. 

Ligand — An electron-pair donor species, commonly an anion or a neutral molecule that can form one or several bonds, involving highly covalent character, with metal species. A ligand with a single donor group is usually called unidentate, whereas the terms bidentate, tri-dentate, tetradentate, pentadentate, and hexadentate are commonly used to indicate the number of bonds that... 

As a result of the high ionic charge to radius ratio of titanium(IV), normal salts of titanium(IV) are difficult to prepare from aqueous solutions these often yield basic, hydrolyzed species. A tris-catechol species, [Ti(cat)3], prepared by Raymond etal. is one exception it is stable in aqueous solution up to pH 12. The catechol ligand is so stabilizing to Ti that the Ti ATi reduction potential is shifted from the value of -1-0.1V cited as the standard potential in acid in Scheme 1 to a value for [Ti(cat)3] of -1.14 V vs. NHE, affording a powerful example of ligand tuning of metal redox potential. 

Benzylic and allylic halides dimerize (homo-couple) readily in the presence of a number of metal species. Synthetically useful yields of homo-coupled products have been obtained using chlorotris(tri-phenylphosphine)cobalt(I), nickel(O) complexes generated in situ, ° Te " species, VCb/LAH, CrCh/LAH and TiCb or TiCl4/LAH. Representative examples are given in equations (37) and (38). Treatment of 8-bromocrotonates with zinc(O) in DMSO leads to dimerization. ... 

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