Ligand Reduction and Displacement from Organometallics

Hydrogenation of olefinic ligands in zerovalent complexes is a fadle method for the synthesis of metal organosols. Hydrogenation of (cydooctadiene)(cydo-octatriene)ruthenium, Ru(COD)(COT), yidds metaUic ruthenium, and, in the presence of polymers such as PVP, ceUulose nitrate, and cellulose acetate, ruthenium sols form. [23, 113] For the PVP stalnlized sol, the partide rize is very small (ca. 1 nm). Similar reactions of Ni(COD)2, Pt(COD)Q2, or mixtures of the two have been used to prepare PVP stabilized mono- and tnmetallic organosols of these metals. [114] 

Colloidal copper has been prepared by an organometallic route through the reaction of (cydopentadienyl)(tert-BuNQCu with carbon monoxide in the presence of either PVP in methylene chloride or poly(dimethylphenylene oxide), PPO, in anisole. The PPO stabilized sol contains zerovalent copper particles of 4.0 nm diameter, while the PVP stabilized colloid contains larger particles with a relatively broad size distribution. [115] 

Modern versions of this method employ more versatile metal evaporation techniques (e. g. multiple metal sources) and allow for better control of such experimental parameters as evaporation rate and pressure. The procedures reported take one of two forms. In the first, which is essentially a preparative scale matrix 

A variation on these techniques involves the generation of the metal vapor in an inert gas at moderate pressures, instead of at the highest possible vaccum. 

The condensation of vapors of palladium, platinum, copper, or nickel into methycyclohexane solutions of o-butylaluminoxane, (uo-BuA10) in a rotating reactor was used to prepare small ( 2 nm) colloidal metal partides. [133] These sols were notable in that stabilization of the metal partides was achieved in a nonpolar hydrocarbon with only Lewis add spedes stabilizers, instead of the usud polar donor polymers such as PVP, etc. [142] Tri-iso-butylaluminum itself was also effective in stabilizing the colloidal metals and gave pdladium particles with diameters less than 1.0 nm. [113] 

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