Trimetalated compounds

Finally, trimetallic compounds have been developed to enhance the electroactivity of Pt-based catalysts, for either methanol or ethanol electro-oxidation. A long time ago, it was reported that adsorption of molybdates (Na2Mo04) at a Pt black electrode... 

Fig. 9. The use of diols in forming Type Cl structures (a) and (b), and a general depiction of the resulting trimetallic compounds (c)...

The compound is very soluble in chloroform and dichloromethane and insoluble in benzene, diethyl ether, and ligroin. The H NMR spectrum shows a resonance for the methoxy groups at r 6.905 (3JpoCH = 12 Hz) with additional resonances from o-phenylenebis(dimethylarsine) centered at r 8.70 and 2.90. The complex forms the trimetallic compounds [ Pt[OP(OCH3)2] 2 [o-C6H4[As(CH3)2] 2 2M] (C104)2 [M = Cu, Co] on treatment with the appropriate metal perchlorate salt. 

Loss of carbonyl groups does not occur in a stepwise manner as usually observed, but three carbonyl groups are eliminated in one step, and for the trimetallic compounds even the remaining three carbonyl groups are eliminated in one step. This suggested pattern is supported by the presence of the appropriate metastable peaks in all the spectra. 

Our approach to the subject has been to divide the metallocarboranes according to the size of the polyhedron. Starting with twelve-vertex compounds, which constitute the majority of the effort, we proceed to the larger polyhedra, so far unknown in the B H 2 and C2B 2H series, and then to the lower polyhedra. Further subdivisions within each polyhedral size include synthesis, structures, and properties of monometallic complexes, reactions of monometal lies, bimetallic preparations and reactions, and, in two instances, trimetallic compounds. 

The clusters Co3(CO)9E (E = P, As) are an interesting example showing the basicity of the main group element. For these molecules the discrete trimetallic compound is only observed for E = As, and then it is only short-lived. These molecules undergo a spontaneous trimerization to give [Co3(CO)8E]3 in which three clusters each have an E atom donating to a... 

Bimetallic and trimetallic compounds with bridging ligands encompass a general theme in chemistry, which is far too wide to be justifiably dealt with in a single article. The range of complexes, which qualifies for inclusions, is very diverse and often unrelated. For this reason we have decided to limit artificially the scope of the article by excluding certain areas which have been reviewed extensively. Therefore, the following selection criteria were enforced when material was collected. 

First, only transition metal complexes are considered, thereby excluding bimetallic and trimetallic compounds with a- or 7r-bonded main group metals, for example, (t7 -C5H4ER3)M(CO) X (M = Fe, Mo E = Ge, Sn, Pb X = Me) (30), as well as lanthanides and actinides (3)). 

Complexes where two Fc substituents are tr-bonded to a central transition metal fragment form part of a general class of trimetallic compounds E. On the other hand, two metal fragments, one on each of the cyclopen-tadienyl rings of ferrocene, represent another type of arrangement (F) of metal fragments in trimetallic complexes. The ferrocenyl compounds... 

The coordination chemistry of compounds containing phosphorus-carbon multiple bonds, such as phosphaalkynes, phosphaalkenes, phos-phaallenes, phosphaalkenyls, and phosphaallyls, has been studied extensively (349,350). The chemistry is dominated by the donor properties of the phosphorus atom, and, as far as we are aware, no examples of bimetallic or trimetallic compounds with bridging ligands which link metal centers by a carbon cr bond and a C=P or C P n bond have been recorded. Once the lone pair on the phosphorus atom is involved in bonding, the unsaturated bond becomes a possible site for further coordination. 

Like the preceding linear trimetallic compounds, these platinum clusters seem unable to add/lose electrons without molecular destruction in fact, in a series of related species (see Table 3), the only redox change is the irreversible one-electron reduction [24, 25] ... 

The palladation of the neopenthyl group of dimethylneopenthylamine also leads to a trimetallic compound ... 

The latter trimetallic compounds, moreover, lead to an unusual tetrametallic species via reaction with a cationic Pd derivative ... 

Interestingly these compounds can complex a copper anion to lead to trimetallic compounds, 66, with a high temperature nematic phase. In these series the ferrocene moiety is at the end of the molecule rather than being incorporated into the core. 

The coordination of tris(pyrazolyl)amine and bis(pyrazolyl)amine ligands toward [Rh(/r-Cl)(cod)]2 was studied and the crystal structure of the trimetallic compound Rh3Cl3(cod)3(tdma) was reported. Trispyrazolylborate ligands also provided a series of complexes of the type TpRh(LL) (LL = nbd or cod), whose NMR spectroscopic properties and structural features were studied. The fluxional behavior of complexes of formula Tp Rh(LL) (LL = nbd, 2CO, cod R = H, Me, Ph, Br) was studied by means of NMR spectroscopy. Two K -square-planar isomers and one re -pentacoordinated complex were observed. The structure of the complex K -Tp Rh(nbd) was confirmed by X-ray diffraction. The hapticity of the Tp ligand was also studied on the basis of the i B-H) obtained by IR spectroscopy. Reactions of [Rh(/r-Cl)(nbd)]2 with a series of bis- and tris(azolyl) methanes 388, 389, 390, 391, and 392 were also reported. ... 

Very recently, a Cr(I) aminopyridinate species containing a Cr-Cr quintuple bond was reported to react with AlMc3 via insertion of the Cr-Cr quintuple bond into the Al-Me bond (carbalumination) to form the trimetallic compound LCr ()i-CH3)( i-AlMe2)]CrL (L = (2,6-diisopropylphenyl)-[6-(2,6-dimethylphenyl)-... 

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