Complexes of Various Metals

Mo(NO)2L2Cl2, from isocyanide ligand addition to [Mo(NO)2Cl2]. These complexes are, in general, analogous to many known complexes of these metals with other ligands. 

The observation has been made (22) that CjHjMo(CO)2(CNC6H,)I, formed from CjH5Mo(CO)3l and CNCgH, exists as two isomers. These can be separated the cis isomer is pink, m.p. 78° C the trans is a peach color, m.p. 103° C. In solution at room temperature one isomer rapidly interconverts to the other, to give an equilibrium mixture with 60% cis and 40% trans species. 

Aumann and Fischer (7), as part of a larger project on carbene-metal complexes, have investigated the reaction of Cr(CO)5C(OCHj)CH3 and cyclohexyl isocyanide. They describe an initial 1 1 adduct of these reagents, to which they ascribe structure (XX) it is interesting to note that neither 

Several papers have appeared recently comparing various properties of carbonyl metal complexes substituted by various phosphines or phosphite ligands or isocyanides. Angelici and Ingemanson (4) studied the equilibrium 

Innorta, Distefano et al. 53, 72) have reported first ionization potentials for a series of M(CO)jL complexes (L = various phosphines and RNC) and find a linear correlation between these values and the ligand ionization potentials and they report calculations of these ionization potentials using an equivalent orbital method. 

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The formation of complexes of various metal ions with oxine (5) and some of its derivatives, their extraction into CHCI3 and their Xmax and e values have been reviewed. Purpurin (LH3, 17) forms with Mg(II) colored complexes of varied composition. However, at pH 9.5 the complex MgLH is formed and can be measured at 540 nm (e =... 

Polymer films can also be electropolymerized directly onto the electrode surface. For example, Abruna et al. have shown that vinylpyridine and vinyl-bipyridine complexes of various metal ions can be electropolymerized to yield polymer films on the electrode surface that contain the electroactive metal complex (see Table 13.2) [27]. The electronically conductive polymers (Table 13.2) can also be electrosynthesized from the corresponding monomer. Again, a polymer film that coats the electrode surface is obtained [25]. Electropolymerized films have also been obtained from styrenic, phenolic, and vinyl monomers. 

The same synthetic approach was used in classic syntheses of r (ji)-complexes of various metals [11]. Such syntheses are carried out in two steps preparation, for example, of cyclopentadienyl derivatives of alkali metals with their further application in the syntheses (3.148), (3.149) of sandwich ri5-complexes of mainly transition metals ... 

Just what does the typical chemist imply when she/he uses the terms hard and soft To few if any does it correspond to Pearson s quantitative scale derived from gas-phase parameters and where hardness is the reciprocal of softness. More likely it expresses features of stabilities where, for example, though Cu + binds NH3 more avidly than Mg +, the latter metal ion interacts more strongly with F than does Cu +. Comparisons of this kind and the stability orders of halide complexes of various metal ions mentioned at the beginning are equivalent to describing the extent of substitution reactions. If M and N are two different metal ions and X and Y two different ligands, we may compare the hardness of a metal ion by considering the substitution on the metal ion of one ligand by another... 

The (Pi)d values as estimated for the complexes of various metal ions with CM-Sephadex C-25 and C-50 gels at a = 1 are listed in Tables 1 and 2. It is apparent that the (Pj)q values of respective metal complexes determined for both gel systems are, within experimental error, in agreement with each other. This documents the validity of the Gibbs-Donnan model for interpretation of the electrostatic effect encountered in the cross-linked polyion systems. 

Complexes of various metal salts and chiral hw-oxazolines have also been examined as catalysts for allylations of aldehydes (Eq. 21) [38], The most effective salts were ZnCl2, ZnBr2, Znl2, Sn(OTf)2, and InCl3. Octanal and cyclohexanecarboxaldehyde afford adducts of 40 5% ee with complexes of zinc salts. 

Fonnation of metal-EDTA complexes The formation constants of EDTA complexes of various metals are listed in Table 11-2. Written as concentration constants, they involve reactions of the type... 

This route shows a possible intermediate from which the allylic product is obtained by reductive elimination. Also, for the formation of allyl acetate in the palladium-catalyzed gas-phase oxidation of propene, a r-allylic species on the catalyst surface has been proposed [35]. /r-Allyl complexes of various metals have been synthesized in recent years. For many catalytic reactions they are assumed to be intermediates [50-53]. 

Lu atom (Lu-N 2.352(4) A). The formation of the dianion complex apparently proceeds by nucleophilic addition of the imido unit to the C N group of benzoni-trile, which demonstrates that a lanthanide-imido bond, even in a bridging form, is very reactive. This is in contrast with what was observed previously for bonds between transition metals and bridging imido ligands, which are usually robust and unreactive. Moreover, the resultant product represented the first metal complex of an amidinate dianion, in contrast to the well-known complexes of various metals with amidinate monoanions [RNC(R0NR] as ligands [6,7]. The dianion complex and related complexes derived from imido lanthanide species react with excess of benzonitrile under selective formation of the cyclotrimerization product 2,4,6-triphenyl-1,3,5-triazine [72]... 

Cyclization of metal alkyls with an acceptor group in the y-position affords cyclopropanes. Complexes of various metals can be used and there are many different methods of generating the acceptor group. 

The selectivity of spectrophotometric methods has been greatly increased by the development of derivative spectrophotometry (see Chapter 1.5). Derivative spectrophotometry enables one to single out, by means of various mathematical algorithms of data processing, a separate signal due to a selected component, from the sum of absorbances of the analysed mixture. This technique was successfully applied in determinations of a number of elements in mixtures such as Pd, Pt and Au [37], Pd and Pt in iodide solutions [38], Au, Pd and Pt in bromide solutions [39], Ru(IIl) and Rh(IIl) in the form of octadecyldithiocarbamate complexes [40], Ru and Os in chloride solutions [41], Cu, Hg and Pb as dithizonates [42], complexes of various metals with 4-(2-pyridylazo)resorcinol [43], Fe(IIl) with EDTA in the presence of Cr(III), A1 and Mn [44], Cr(III) and Cu(II) with EDTA [45], and Cu and Co in a flow system [46]. Derivative spectrophotometry was also used in the study of Sr- complexing reactions with various crown ethers [47]. 

The separation and quantification of cyano complexes of various metals have been successfully carried out by Hilton and Haddad [45]. Cyano complexes of Cu(I), Ag(I), Fe(II), Fe(III), Co(II), Au(I), Au(IlI), Pd(II), and Pt(II) were analyzed by ion-pairing chromatography. The methods can be extended to many speciation problems. 

Histidine and asparagine function as tridentate chelates. In the asparagine complexes, the mixed (dl) form is the more stable while the reverse is true of the histidine complexes. Potentiometric studies of the complexes of various metals (Nill, Cull, Coll, Znll) with a wide range of amino adds all of which function as bidentate chelates have failed to reveal any differences in the stability of Mdl and Mll forms. (Ritsma et al. 1965 Gillard et al. 1966). The reason why the chirodiastaltic interactions should be so much more marked with tridentate than bidentate chelates calls for investigation in terms of the intramolecular force system. 

Metal dioxides produced by sputtering techniques [371] in inert gas matrices take linear or bent O—M—O structures. Metal dinitrides produced by the same technique also take linear N—M—N (M = U [372] and Pu [373]) or bent N—M—N (M = Th [374]) structures. These structures are markedly different from those of molecular oxygen and nitrogen complexes of various metals produced by the conventional matrix cocondensation technique (Chapter 3 in Part B). 

A cornerstone for the development of such microheterogeneous systems is the choice of an optimal photosensitizer for the process. At present, a great many experimental data have been obtained on the properties of ordered microheterogeneous photocatalytic systems operating with molecular photosensitizers such as complexes of various metals [2,3]. However, some important photochemical properties of the designed systems (e.g., the quantum yields of the charge photoseparation or the rates of the vectorial transmembrane electron transfer) have not allowed, up to now, the design of composite photocatalytic... 

The structures of binuclear, diphosphine-bridged complexes of various metals, including rhodium, are discussed in more detail in Chapter 5. 

Much work has also been conducted on the hydrosilylation of ketones and imines (Equation 16.16). The products from these reactions are silyl ethers and sdylamines. These additions of silanes across C-X ir-bonds have been conducted predominantly for the purpose of generating optically active alcohols and amines after hydrolysis. Because the mechanism of these reactions is less defined than the mechanism of alkene hydrosilylation, and this chemistry lies outside the theme of this chapter, the hydrosilylation of ketones and imines is presented only briefly. Instead, this chapter provides an overview of the scope and motivation for the hydrosilylation of alkenes and alkynes and provides details on the mechanisms of these reactions catalyzed by complexes of various metals. Several comprehensive reviews of the scope of these reactions have been published. ... 

The history of coordination chemistry in Japan is briefly presented. Yuji Shibata, founder of coordination chemistry in Japan studied extensively the absorption spectra of complexes of various metals from 1915 to 1917 after returning from Europe. His researches also included the spectro-chemical detection of complex formation in solution, coagulation of arsenic sulfide sols by complex cations, and catalytic oxidation and reduction by metal complexes in solution. Ryutaro Tsuchida published the "spectrochemical series" in 1938 based on the results of his measurements of absorption spectra of cobalt complexes. One of the most remarkable results after World War II is the determination of absolute configurations of cobalt complexes using X-rays in 1954 by Y. Saito and his coworkers. 

Further synthetic studies have extended the availability of different cryp-tates, which are of considerable interest owing to the possible selectivity of association with different cations. The amine (77) by inversion is capable of atropoisomerization. Monoprotonation or diprotonation leads to salts which can only be deprotonated with great difficulty. This implies that in the ammonium salts the protons must be located inside the cavity. The extraordinary properties of (77) are demonstrated by the recovery of the diammonium salt unchanged after solution in 5N-potassium hydroxide at room temperature for 18 days. Cryptate complexes of various metal salts with (78) show the inclusion of the cation in the cavity, and further cryptates derived from (79) and related compounds are reported. ... 

Six-molar HCl can convert this to white [PtCl(NH3)5]Cl3. As with many other complexes of various metals, the coordinated Cl" can be replaced by (non-aqueous) Cp3S03" ( triflate ), which can then be replaced especially nicely by other ligands. Refluxing [PtCl(NH3)5]Cl3 with OH", followed by HCl, yields [Pt(NH3)5(H20)]CU. 

Polyazamacrocycles (or azacrown ethers) attract a thorough and constant interest of the researchers due to their imique ability of selective complexation of various metals, organic and inorganic anions, and some polar moleeules. During the last decades himdreds of such compounds were synthesized, whieh eontain nitrogen, oxygen, and sulfur atoms [1], Many polyazamacrocycles can serve as molecular sensors due to their photochemical or redox properties, they contain aromatic moieties which can be present as substituents at nitrogen atoms or can be incorporated in the cycle. 

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