Metals mixed-metal trinuclear complexe

Cold(l) and Silver(l) Mixed-Metal Trinuclear Complexes 33... 

Reaction of the Ru=Ru double bonded complexes [Cp2Ru2(M.-CO)(p,-C2R2)]. (R = Ph, CF3), with [Fe2(CO)9] afforded the new mixed metal trinuclear complexes [Cp2Ru2Fe(CO)3(p-CO)(p3-CO)( l3-C2R2)]. which was structurally characterised for R = Ph. Reactions of the products were reported. 

In further work, the mixed-metal trinuclear complex, [WFe2(p -S)2(CO)g (S2CNEt2)] (197), has been prepared from [W(CO)4(S2CNEt2)] and [Fe2(p-S2)(CO)6]. It has been crystallographically characterized and shows no direct metal-metal interactions (952). 

Fig.10. Schematic view of the zero-order (dotted curves) and first order (continuous curves) states for a symmetrical mixed-valence trinuclear complex of the type Ru(ll)-Ru(lll)-Ru(ll), assuming electronic couplings of 2000 and 1000 cm between adjacent and remote metal centers, respectively.

Based on the fact that pi-acids interact with the trinuclear gold] I) pi-bases, TR(carb) and TR(bzim), the trinuclear 3,5-diphenylpyrazolate silver(I) complex was reacted with each. Mixing [Au3(carb)3] or [Au3(bzim)3] with [Ag3(p,-3,5-Ph2pz)3] in CH2CI2 in stoichiometric ratios of 1 2 and 2 1 produced the mixed metal/mixed ligand complexes in the same gold-silver ratios. The crystalline products were not the expected acid-base adducts. It is suspected that the lability of the M-N bond (M=Au, Ag) in these complexes results in the subsequent cleavage of the cyclic complexes to produce the products statistically expected from the stoichiometry of materials used [74]. As a result of the lability of Au-N and Ag-N bonds, and the stability of... 

Au-C bonds, mixed metal gold-silver dimers of planar, trinuclear complexes are readily formed by mixing gold(I) carbeniates and gold(I) benzylimidazolates with silver(I) pyrazolates in stoichiometric ratios. The complexes retain the ligands associated with the metal atoms of the starting materials. 

Other first-generation dendrimers built around multichelating ligands are the trinuclear complexes 29 - 38 [50-52] and several hexanuclear complexes (for representative examples, see 39 and 40) [53]. In all of these compounds, the photophysical properties are equivalent to those of their building blocks. In the mixed-metal complexes 31 and 34 [50b] the Ru(II)- and Os(II)-based chromo-phores are only weakly-coupled and a dual luminescence is observed. 

The mechanisms of these reactions are probably complex but radical processes seem likely. The final products of insertion into the metal metal bond are actually trinuclear species. Insertion into terminal metal hydride or metal alkyl bonds could, in principle, generate mixed-metal dimers. In practice, aside from insertion into the metal halogen bond, such as that shown in equation (65), few such reactions have been reported. 

Trinuclear complexes can be made if bis(amido) chelate ligands are used in place of the tripod ligands. The addition of two CpM (CO)2 units (M = Fe, Ru) can be carried out sequentially. However, mixed trinuclear complexes possessing Zr-Ru-Fe metal centers cannot be prepared this way (Scheme 7). ... 

The lacunary polyanions can act as ligands with numerous metal cations, leading to mono-, di-, or trinuclear complexes according to the number of vacant sites. These complexes are the earliest model materials of mixed oxides, and they are important for catalytic purposes, particularly for the oxidation of organic substrates. 

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