Other Metal Complexes

Antibacterial complexes such as silver sulfadiazene and some mercurials also manifest antiviral activity [51, 52]. Mersalyl, a diuretic (Chapter 12), has some in vivo action when mice treated with lethal doses of coxsackie virus are then administered the mercury complex [53]. The levels needed for 100% inactivation in vitro by mercurials is dependent on the virus, and thiols reverse the antiviral effect [54]. Conformational changes and breakdown into subunits have also been observed after mercury treatment [51], 

Silver sulfadiazene inhibited the infectivity of both types of HSV Herpesvirus hominis) rapidly in vitro and much more effectively than did AgN03 [55]. Application in vivo was effective against development of herpetic keratoconjunctivitis, which leads to encephalitis [56]. A silver metachloridine complex has been claimed to have similar properties to that of the sulfadiazene [57]. Miscellaneous species whose antiviral effects have been reported include the Rh(I) organometallic complex, [Rh(acac)(COD)] [58] and Mn(II) Schiff base complexes [59]. 

Finally, the unusual mineral condensed ions (MCIs) certainly qualify as inorganic salts, and these polyanions formed from tungstate or molybdate (as MO4 ) and central ions such as silicon and antimony are being studied 

Meridional forms of the N3S quadridentate complexes of the type (18) with R = Me and NH2 are readily prepared from [Co(en)2(S(R)CH2CH2NH2)] (with R = CH2COCH3 and CH2CN, respectively) in basic solution. X-ray crystallography of the complex with R = NH2 (monohydrate of the triflate salt) establishes the configuration of the quadridentate. 

The effect of different counteranions, X, on the rate of racemization of [Ni(phen)3] + ion has been investigated in H20-Bu 0H mixtures. When the mole fraction of Bu OH is greater than 0.5, X ions accelerate the racemization rate in the order CIO 1 Br Cl . Attack by X at the metal ion rather than the 2- or 4-positions of phen (analogous to the Gillard mechanism) is postulated to be involved, primarily because Cl ion is a better accelerating anion than I ion and the reverse behaviour would be expected if attack at the aromatic ring were involved.  

Rate data from H n.m.r. investigations of the intramolecular rearrangement processes involving a number of jff-diketonate complexes of V are collected in Table 4. An unambiguous distinction between twist and bond-rupture mechanisms could not be established. The V complexes rearrange significantly faster than the analogous Al species and at rates comparable to those of Mn and Ga.  

Two groups report n.m.r. studies of configurational rearrangements of cis-and rranj-[Ti (LL)2X2]. When LL=2,4-dimethylpentane-2,4-diolate or 

Yamamoto, T. Fujiwara, and Y. Yamamoto, Inorg. Nucl. Chem. Lett., 1979, 15, 37. 

A manganese(ii) porphyrin complex, Mn (TPP), has been shown to react reversibly with 02 in the presence of pyridine at - 79 °C in toluene solutions. Qualitatively the affinity for O2 of the [M(TPP)py] complexes increases in the order Co Fe Mn and may reflect the ease of oxidation of the analogous metalloporphyrins. E.s.r. evidence is interpreted in terms of the metal(iv) oxidation state in the manganese oxygen complex. A similar oxidation state has been postulated in the reactions of manganese- 

Chromium(ii) is rapidly oxidized by molecular oxygen to yield the [Cr(OH)2Cr] + dimer as product. Pulse-radiolysis studies have been made of the reaction, the initial step, 

The oxidation of uranium(iv) by O2 in toluene and in trioctylamine has been shown to be second-order in 

A very different set of interesting d niobium and tantalum hydride catalysts containing bulky aryloxide ligands recently reported by Rothwell [52-54] appear very promising. For instance, naphthalene and anthracene are reduced at 80 C and 3-100 atm Hj by [Ta(OC H3(C H,)2-2,6 2(H)j(PMc,Ph)] to produce mainly tetralin or 1,2,3,4-tetrahydroanthracene, respectively. 

The kinetics and mechanism of the reaction of [Cu(bipy)2]+ with O2 have been investigated using the stopped-flow method. At pH 3 a scheme consistent with the data may be written as 

Yonderschmitt, K. Kernauer, and S. Fallab, Helv. Chim. Acta, 1965, 48, 951. 

Reaction with O2 (and CO) is shown to be reversible in the solid state although in solution (MeNOz) oxygenation of the bimetallic complex is more complicated. A report on the reaction of blue oxidases with Og indicates that the optical and e.p.r. absorptions correlate well. The reaction time with fully reduced fungal laccase is 1 s and for the Rhus enzyme it is 10 s. Since only one line of the e.p.r. spectrum may be observed because of overlapping copper signals, identification of the oxygen species involved is diflBcult but the most likely candidate at present is the ion 0.  

The oxidation of copper(i)-olefin complexes by O2 has been reported. The copper complexes were prepared pulse-radiolytically by rapid reduction of Cu in the presence of ethylene or allyl alcohol. The irradiated solution was then mixed with oxygenated water in a stopped-flow apparatus. For the two complexes described the rate laws differ only slightly. In the reaction with the ethylene (L) species the rate law obtained is 

The product hydrogen peroxide was observed for both systems but only to the extent of 60—70 % of that expected in the reaction 

The oxidation of copper(i) by oxygen in the presence of chloride ions has been studied potentiometrically, the rate being a function of hydrogen-, copper(i)-, and chloride-ion concentrations. In HCl-LiCl media the data are consistent with the reaction scheme 

The kinetics and mechanism of the metal-chelate-catalysed oxidation of pyrocatechols to quinones have been investigated. Comparisons have been made of the base- and Mn ion-catalysed auto-oxidations of 3,5-di-t-butylpyrocatechol (3,5-DTBP) to the corresponding o-quinone (3,5-DTBQ) with the rates when manganese(ii)-4-nitrocatechol, manganese(n)-tetra-bromocatechol and cobalt(n)-4-nitrocatechol (Co -4NQ were present as catalysts. The rates are dependent on hydrogen-ion concentration, and the stoicheiometry and products depend on the nature of the catalytic reagent, viz. 

The co-ordination of the two ligands in the plane of the metal ion would then permit a r-bonded interaction of the oxygen molecule with the metal centre. 

Stereoselective auto-oxidations have also been described in the reactions of dimeric vanadium(iv)-tartrate complexes. The rate of uptake of Oa in the presence of these complexes is dependent on the isomeric form (d, l, or meso) of the ligand, the influence of pH being observed to be important. The overall stoicheiometry conforms to the equation 

The mechanism of oxidation of cerium(m) and silver(i) ions by ozone has been reported, The reaction is second-order overall in aqueous nitric acid and proceeds via a free-radical mechanism. 

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The advantages of titanium complexes over other metallic complexes is high selectivity, which can be readily adjusted by proper selection of ligands. Moreover, they are relative iaert to redox processes. The most common synthesis of chiral titanium complexes iavolves displacement of chloride or alkoxide groups on titanium with a chiral ligand, L ... 

While on the subject of reviews, attention should also be directed to a very recent collection of articles on isocyanide chemistry edited by Ugi 156). This volume is oriented somewhat toward the organic chemistry of isocyanides, but not with the complete exclusion of metal complexes of these species one is directed in particular to the chapters by Vogler (Chapter 10) on coordinated isocyanides and by Saegusa and Ito (Chapter 4) on a-additions to isocyanides. These latter reactions are often catalyzed by copper(I) compounds and occasionally by other metal complexes as well, and it is believed that this catalysis is accomplished by intermediate formation of metal isocyanide complexes. 

Various a-addition reactions are observed to be metal- or acid-catalyzed, or to be uncatalyzed. In this review only the metal-catalyzed reactions will be discussed, since it is generally assumed that metal isocyanide complexes are involved in these systems. A number of metal-catalyzed a-addition reactions have been mentioned recently. Copper(I) oxide seems to be the most commonly used catalyst, although other metal complexes sometimes are satisfactory. Table III presents a partial survey of this work. 

Although 4-methyl-5-amino-1-formylisoquinoline thiosemicarbazone, 22, also forms [Ni(22)Cl2] with chemical properties similar to [Ni(21)Cl2], it, along with other metal complexes of 22, showed no activity against P388 lymphocytic leukemia test system in mice [202]. 

Other metal complexes containing Pd, Ru, Co, or Pt have also been used.176 The hydroformylation reaction can also be performed by using methyl formate instead of carbon monoxide and hydrogen.177... 

Blue luminescence of zinc complexes of pyridyl-containing complexes is an area of current interest.277 Design of blue luminescent materials is of relevance to display applications, as blue-light-emitting diodes, and to this end Che examined solution luminescence of zinc pyridylamine complexes.73,278 Che and co-workers studied the complex Zn40(7-azaindoyl)6 which has a blue emission at 433 nm in the solid state.279,280 In an attempt to improve on stability Wang et al. examined compounds with neutral 7-azaindole and an A-functionalized pyridyl derivative.281 In contrast with other metal complexes of the neutral 7-azaindole (32), Zn(7-azaindole)2(OAc)2 is a blue luminescent compound and a A-(2-pyridyl) 2-azaindole (33) and its complexes were also... 

The closely related dichloroethylenediamine platinum(II) was found to be slightly better than PtCll- as a heavy atom. A platinum-sulphur bond to methionine 29 is formed according to current analysis (now confirmed). The platinum cannot be removed by washing the crystal in sharp contrast to the reversible binding of other metal complexes. ... 

This and the nickel analogue are shock-sensitive and violently explosive. Other metal complexes (except cobalt) decompose slowly liberating the dimethyldiphos-phane which tends to ignite when old sample bottles are opened. 

Other metal complexes containing several types of unsaturated compounds as ligands can be prepared by similar reactions. 

CL reaction can be catalyzed by enzymes other than HRP (e.g., microperoxidase and catalase) and by other substances [hemoglobin, cytochrome c, Fe(III), and other metal complexes]. The presence of suitable molecules such as phenols (p-iodophenol), naphthols (l-bromo-2-naphthol), or amines (p-anisidine) increases the light production deriving from the HRP-catalyzed oxidation of luminol and produces glow-type kinetics [6, 7], The use of other enzymes, such as glucose-6-phosphate dehydrogenase [38-41], P-galactosidase [42], and xanthine oxidase [43-46], as CL labels has been reported. 

Other metal complexes such as titanium or ruthenium complexes can also be used to catalyze the olefin hydrosilylation reactions. Further information is provided elsewhere.30... 

Pardey and coworkers have also reported activity for the iridium complexes, including c/s-[Ir(CO)2(py)2](PF6)135 and more recently,168 Ir4(CO)12, which was prepared earlier by Della Pergola et al.102 The conditions used were Pco = 1.9 atm T = 100 °C [Ir] = 10 x 10 3 mol/L. Again, the pressure of Pco was higher relative to the studies with Rh complexes. The data are reported in Table 42. As observed with other metal complexes, electronic and steric effects are apparent. The Ir4(CO)12 complex was also tested in 4-picoline and displayed a similar turnover rate of 12 mol PI2/mol [Ir] per day. 

Other metal complexes such as those of Boron shown in Scheme 3.47 (148) have also been reported to be viable green emitters. 

Other metal complexes also have promising anticancer activity. Two Ti(IV) complexes are on clinical trial, an acetylacetonate derivative (budotitane) and titanocene dichloride, and the antimetastic activity of octahedral Ru(III) complexes is attracting attention, one of which is now on clinical trial. Ru(III), like several other metal ions, can be delivered to cells via the iron transport protein transferrin. 

Several other metal complexes have promising photodynamic activity and are currently under development (248). Metalloporphyrins inhibit the enzyme heme oxygenase for example, chromium porphyrin and mesoporphyrin are potent inhibitors of heme oxygenase both in vitro and in vivo (249, 250) and are being used for the treatment of the neonatal jaundice. 

The effect of several metal ions on the anti-HIV activity of bi-cyclams has been reported (371). Zinc may facilitate the binding of bicyclams to the virus, and bis-Zn(II)-bicyclam complexes exhibit activity comparable to that of the parent bicyclam, but activity is reduced for other metal complexes such as Ni(II), Cu(II), Co(II), and Pd(II). 

There are other metal complexes, such as tin, aluminum, magnesium, iron, cobalt, titanium, and vanadium complexes, which are similarly useful in stabilizing a particular phthalocyanine modification. Moreover, carboxy, carbonamido, sulfo, or phosphono-copper phthalocyanine may be admixed during fine dispersion of the pigment. 

The general idea of this concept was first outlined by Nugent and Rajan-Babu [17-20] as shown in Scheme 3, and constitutes an analogue of the well-established opening of a cyclopropylcarbinyl radical [21,22]. Titanocenes have emerged as the most powerful reagents in these transformations. However, it is clearly attractive to find other metal complexes in order to develop novel reactivity patterns. 

Other metal complexes have also been found to emit in the green spectral region, for example, beryllium complexes [140]. 

The same type of coordinating ligands will be discussed for other metal complexes. 

While hydrosilylation of 1-alkenes and HSiCl3 with platinum catalysts provides linear products (1-trichlorosilylalkanes), palladium chloride modified with phosphines gives products carrying the trichlorosilyl group at the secondary carbon. This is highly remarkable because all other metal complexes studied so far lead to 1-substituted products. This regioselectivity leads to the possibility to carry out asymmetric hydrosilylation. 

Despite many studies having been reported regarding the reactivity of Ir—NHC complexes, it seems that the catalytic properties of these materials have not yet been fuUy explored. Studies on the reactivity, and the access to new molecular architectures in which the metal in highly electron-rich, envisage a wide set of appUcations in homogeneous catalysis. It is noteworthy to point out that Ir—NHcs offer a clear advantage over other metal complexes in processes implying C—H activations, as observed by the number of intramolecular versions of this process that have been reported and fully studied. 

In fact, a variety of hansihon metals have been used as efficient catalysts in a range of cycloaddihon reachons. Among these, the Co, Ni, Ru, Rh and Pd complexes have been the major players, whilst the Ir complexes have played only a minor role. Nonetheless, several Ir-catalyzed cycloadditions have been recently reported, which cannot be realized by other metal complexes. This chapter summarizes Ir complex-catalyzed cycloadditions, which include several types of cycloi-somerizahon and cycUzahon. 

Cloud point extraction of metal ions. The use of cloud point extraction as a separation technique was first introduced by Watanabe for the extraction of metal ions forming sparingly water soluble complexes [109], Since then, the technique has been applied successfully to the extraction of metal chelates for spectrophotometric, atomic absorption, or flow injection analysis of trace metals in a variety of samples [105-107,110]. Other metal complexes such as AUCI4 or thiocyanato-metal complexes can be extracted directly using nonionic surfactants such as polyoxyethylene... 

The clearance of DTPA metal complexes by the glomeruli is primarily dependent of the ligand. Thus, other metal complexes may also be useful for GFR measurements. For example, colored metal complexes that are exclusively excreted... 

The asymmetric catalytic Pauson-Khand reaction met success in the late 1990s. Not only the conventional Co catalyst but also other metal complexes, such as Ti, Rh, and Ir, are applicable to the reaction. Asymmetric hydrocyanation of vinylar-enes is accomplished using Ni complex of chiral diphosphite. Further studies on the scope and limitation are expected. 

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