Monometallic complexes

Accordingly, TEM investigations confirmed the NPs formation in Pt-catalysed hydrosilylation from a solution of [PtCl2(cod)]. The particles formed in situ showed a mean size of 2.3 nm. Moreover, XPS (X-ray Photoemission Spectrometry) analysis confirmed that the colloid characteristics are distinct from bulk metal and monometallic complex (binding energy for Pt bulk metal is 71.0 eV for [PtCl2(cod)], 72.45 eV and for Pt colloid, 72.24eV) [12]. 

Scheme 14.7 gives the detailed energetics for M = Ti, Zr and L = H of all the possible reaction steps starting from the monometallic complexes 5 and 7. The order... 

A key property of these polymetallic complexes is geometrical structure, more variable and diverse than the coordination stereochemistries of monometallic complexes or the symmetrical lattices of non-molecular compounds. The following well-defined aggregation modes illustrate the geometrical scope of the field. 

The ligand/metal (L/M) ratios of clusters and cages are intermediate between the low values of non-molecular compounds (I) and the high values of monometallic complexes (III) ... 

Non molecular compounds -- Clusters and cages — Monometallic complexes... 

Anionic clusters are good nucleophiles (see Section III,A) and are often easy to make. On the other hand, the electrophilic nature of most monometallic complexes is obvious from ligand substitutions. The combination of these properties makes a strategy for cluster expansion. This strategy was used for the first time by Hieber (130) in making Fe4(CO)fc from Fe3(CO),7 and Fe(CO)s. It is probably active in many syntheses of large metal carbonyl clusters because the Re, Os, Rh, Ir, Ni, and Pt clusters involved are almost always anionic. However, simple stoichiometries can rarely be written for such reactions (122). This route makes mixed metal clusters accessible, e.g.,... 

A. Monometallic Complexes with Identical Carborane Ligands 155... 

B. Monometallic Complexes with Different Carborane Ligands 161... 

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. 

These ten-vertex monometallic complexes exhibit thermal polyhedral rearrangements similar to those mentioned previously. In fact, they were... 

Substituted allenes undergo polymerisation to linear polymers in the presence of both Ziegler-Natta catalysts, e.g. VOCl3 Al(i-Bu)3 [440], and monometallic complexes such as Ni complexes [442], Amorphous polymers consisting of 1,2-linked monomeric units (predominant) and 2,3-linked monomeric units have been obtained from 1,2-butadiene (H2C=C=CHCH3) ... 

Peris and coworkers have also disclosed Ir and Rh complexes 33 and 34 which can catalyze the hydrosilylation of alkynes [77]. Again, poor selectivity was observed as mixtures of the -trans, [ -cis, and a addition products were obtained. Generally speaking, it was found that Rh catalysts were more reactive than the Ir catalyst and the dimetallic complexes were much more active than their monometallic counterparts. It is believed that the difference in reactivity between the dimetallic and monometallic complexes arises from the dimetallic species ability to oxidize to the corresponding M(III) species, thus preventing oxidative addition of the silane. 

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