Tri-nuclear

Coa(CO)8 decomposes in toluene to produce Co4(CO)ia and carbon monoxide. The reaction is reversible the rate-determining step in the Co2(CO)s to Co4(CO)ia direction is said to be dimerization of Coa(CO)6 fragments. Rus(CO)ia reacts with azulene to form Ru4(azulene)(CO)9, in which the azulene is bonded to one face of the tetrahedral Rui cluster. The mechanism is unknown, except that Ru8(azulene)(CO)7 is though to be an intermediate.  

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The synthesis and structural characterization of luminescent di- and tri-nuclear organopalla-dium complexes with rigid conjugated alkynyl-aryl bridges and preliminary experiments on the formation of the first generation metallodendrimer using the trinuclear complex as the backbone were reported.102... 

However, when osmium atoms are co-condensed with a mixture of benzene and 2-methylpropane only trace amounts of [Os (Tj -CgHg) (TjG-CgHg) ] can be detected in the reaction mixture. More importantly, the tri-nuclear compound [ Os (Tl -CgHg) 3 ( j2-H) 3 ( j3- (CH2) 3CH) ] can be isolated (5) (Figure 8) (29). Co-condensation of osmium... 

In this work we have studied the preparation of electrocatalysts on the graphite matrix using tri-nuclear complexes of 3d-metals with aminoalcohol ligands. Tri-nuclear complexes, 2[Co(Etm)3] Me(N03)2, where Etm = ethanolamine, Me = Zn2+, Cu2+, Ni2+, Co2+, were investigated. 

As it was shown in [15-18], such compounds, with bridging atoms of deprotonated amino alcohol, are formed when aminoalcoholate complexes of metal (III) react with bivalent 3d-metal ions. Many representatives of these compounds were synthesized in crystalline state the polynuclear compounds were also found to form in aqueous and methanol solutions. The structure of 2Co(III) - Ni(II) tri-nuclear complex, according to [17,18], is shown below in Figure 2. 

Syntheses of the tri-nuclear complexes were performed in water-methanol solution according to the reaction... 

As it is seen from the data of Figure 8, all modified materials have poor cycling performance their reversible capacities fade faster than the one of initial non-modified material, and become lower after the first 8-10 charge-discharge cycles. Thus, we can conclude that no positive effect is achieved by means of modification of the Carbon-Type material with bimetal tri-nuclear complex of Co(III)-Ni(II). 

Modification of carbon materials by tri-nuclear complexes of 3d-metals with ethanolamine ligands increases the catalytic activity with regard to the electrochemical reaction of oxygen reduction. The Co-Ni complex is most active in this reaction if pyrolyzed at 600°C. 

The unsymmetrical complexes LnPcPc can also be prepared in a stepwise manner (Scheme 8.1, D, upper part) [87, 112-114]. Treatment of phthalonitrile with excess of Lu(OAc)3- H2Oand DBU gives the half-sandwich compound LuPc(0Ac)(H20)2. The latter complex reacts with Na2Nc in 1-chloronaphthalene leading to the formation of LuPcNc [87]. Similarly, the template reaction of unsubstituted and crown-substituted phthalonitriles with lutetium acetate was carried out in boding w-hexanol in the presence of DBU [115-117]. Bi- and tri-nuclear [118] lutetium complexes could also be obtained following this approach [111, 119]. 

Professor Cotton s studies have considerably clarified our understanding of di- and tri-nuclear metal-metal bonded compounds. For higher nuclearity clusters, rationalisation of structures, bonding, reactivity etc., must be much more tenuous because of the increased number of variables (metal-metal, metal-ligand, steric effects) now present. However, I would briefly like to present a few trends which seem to be emerging in this area. 

The parent carbonyls, M COlu (M = Ru, Os), have not been isolated, but the related hydrides H2M4(CO)13 and HJVtjCCO) have been prepared for both ruthenium and osmium by direct reaction of the tri-nuclear carbonyl with hydrogen or water (see Section III,C) (82, 86). 

We consider, successively, the catalytic role of several classes of mononuclear Zn2+ enzymes and then discuss enzymes with di- and tri-nuclear cocatalytic zinc centres, some of which include a metal ion other than zinc. We conclude with a presentation of some of the zinc-based motifs found in proteins involved in the regulation of nucleic acid and protein synthesis. 

Ruthenium has a considerable propensity to form polynuclear complexes, particularly with carboxylate ligands which as bridging ligands span the Ru centres, sometimes accompanied by a bridging 0x0 ligand. Preparation and properties of bi- and tri-nuclear acetato complexes of Ru have been reviewed [552]. 

Figure 3 Incident photocurrent conversion efficiencies (IPCE) observed for the tri-nuclear complex ([fraw-(NC)Ru(py)4(CN)2]Ru(dcbH2))2 + on a 6-(im-thick Ti02 photoanode in the presence of 0.3 M I2 and 0.03 M Lil.

Many types of ligand have been designed or are known to favour the formation of di- and tri-nuclear nickel complexes. This field of coordination chemistry has recently been extensively reviewed.2590,2591 For a specific discussion of the magnetic properties of dinuclear nickel(II) complexes, see Section 50.5.10. 

Metal-oxygen and metal-metal distances have been established for many oxo- and hydroxo-bridged dimers and polynuclear cations, for example (57)220 and several of type (58).217 Early work was on solids, but recently X-ray diffraction studies have established the geometries of a few such species in solution. EXAFS has proved valuable in establishing the geometry of the various di- and tri-nuclear forms of the various oxidation states of molybdenum in aqueous solution.23... 

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