Heteropolynuclear complexes

Although the Ag- -Ag interactions are not very strong, there are many examples of complexes, which contain Ag-,M contacts. Silver forms very stable heteropolynuclear complexes with different structural motifs, among them it is worth mentioning the species where silver interacts with platinum, gold, iron, mercury, etc. 

The possibility of coordinating functionalized TTFs onto polynuclear core is a very stimulating issue because it is now well established that polynuclear cores, with some restrictions of course, can act as SMMs. We started a systematic investigation of polynuclear paramagnetic complexes with TTF CH=CH—py ligands to scan the possibility to access to bifunctional molecules which can act at the same time as SMM and single component metal. We succeeded in coordinating our modified TTFs to several homo- or heteropolynuclear complexes. This opens new perspectives in the field of multifunctional materials. The size of these molecules, which is of the order of 4 nm, is another important aspect in the field of molecular scale electronic. 

It is clear from the previous sections that the capacity of mesityl groups to act as bridges fosters the isolation of homo- or heteropolynuclear complexes. Thus, tetranuclear dicationic derivatives [ (Ph3As)Au(p-mes)Ag 2(p-dpam)](C104)2110 (dpam = Ph2 AsCH2AsPh2) and [(Ph3P)Au(p-mes)Ag(tht)]2(TfO)227 have been prepared by reaction... 

The kinetic inertness of [Fe(CN)6]4 is typified by the extremely slow thermal displacement of CN by a,a -diimines. Such reactions are however catalyzed270 by a variety of metal ions such as Hg2+ and the stability constants for some of the intermediate heteropolynuclear complexes have been determined.271... 

Balzani et al. (70) employed a strategy focusing on complexes as metals and as ligands (71,72), for developing a number of interesting supramolecular systems. Ditopic polypyridyl ligands, for example, 2,3- and 2,5-dipyridylpyrazine (2,3-dpp and 2,5-dpp), 2,2 -biquinoline (biq), tetrapyrido[3,2-fl 2, 3 -c 3",2"-/z 2", 3 "-/]-phenazine (73,74) (tppz), and 2,3,5,6-tetrakis(2-pyridyl)pyrazine (75-77) (tpypz), in combination with monotopic ligands (e.g., bpy and phen) were utilized in the preparation of a number of homo- and heteropolynuclear complexes of well-defined structures (Fig. 2). 

Stabilization and crystallization of [Cr f/x-OI 0/0112)J(3j y>+ cations have been achieved by exploiting the supramolecular interactions with large anionic assemblies initially with mesitylene-2-sulfonate or its adduct with 18-crown-6,837-839 and subsequently with the adducts of calixarene sulfonates with N- or O-macrocycles.840,841 This approach, illustrated in Scheme 27, allowed the crystal structures of di-, tri- and tetrameric Cr111 complexes, (165)-(167),837,839-841 as well as that of a heteropolynuclear complex, [(H20)4Rh(/i-0H)2Cr(0H2)4]4+,838 to be determined. 

FIGURE 4. Heteropolynuclear complexes with bridging alkynylphosphinegold(I) units... 

Although polynuclear alkyne completes are often prepared by reaction of the alkyne with a suitable metal cluster fragment, heteropolynuclear complexes 69 (Scheme 4-38) have been obtained also by isolobal metal fragment substitution, as noted previously [26]. Higher-nuclearity alkyne complexes also can be produced by the addition of various metal carbonyl fragments to a lower-nuclearity alkyne complex [119], A novel entry to heterobi- (and tri-)metallic neutral p-propargyl complexes (e.g., Fe/Mo) via protonation of trinuclear p-Ti, T1 -o-propargyl derivatives 70 was recently described by Wojcicki and coworkers [120,121]. 

Related heteropolynuclear complexes 27, based on a non-mesomorphic Fc enaminoketone ligand, were also prepared (27 M = Cu, pj) displayed only monotropic phases Cr 144 (N 122) I for the copper complex... 

Enantiotropic SmA mesophases were obtained in mixed heteropolynuclear complexes containing enaminoketone and or7, ti-palladated imine groups 28 transition temperatures and temperature ranges depended strongly on the nature of the enaminoketone derivative. The trinuclear bis(imine) and the tetranuclear chloro-bridged precursory complexes were also mesomorphic, showing an unidentified smectic phase (Cr 118 S 131 I) and a SmA phase (Cr 238 SmA 248 I) respectively. 

Studies involving heteropolynuclear complexes containing V have been discussed throughout this review. Magnetic interactions (VO -VO and VO -Cu " ) have been mentioned. A study comparing the interaction in Cu -Cu, and Cu -VO pairs through... 

In a balanced solution the concentrations of complex formations, which are secondary, may be associated with contents of uncomplexed cations and anions playing the role of basis species, using total equilibrium constants. To simplify this task, let us assume that ions do not form mixed and heteropolynuclear complex compormds. Then the reaction of their formation may look like ... 

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