Carbonylated platinum colloid

The linear CO stretching frequency for the carbonylated platinum colloid while lower than that found for surface bound CO, is in the range reported for the platinum carbonyl clusters [Pt 3 (CO) 6 ] n / sind we find that the carbonylated colloid is easily transformed into the molecular cluster [Pt 12 (CO) 24 ] (10) reaction with water. The cluster was isolated in 50 yield based on platinum content of the precipitate by extraction with tetraethylammonium bromide in methanol from the aluminum hydroxide precipitated when water is added to the aluminoxane solution. The isolation of the platinum carbonyl cluster reveals nothing about the size or structure of the colloidal platinum particles, but merely emphasizes the high reactivity of metals in this highly dispersed state. The cluster isolated is presumably more a reflection of the stability of the [Pt3(CO)6]n family of clusters than a clue to the nuclearity of the colloidal metal particles - in a similar series of experiments with colloidal cobalt with a mean particle size of 20A carbonylation results in the direct formation of Co2(CO)8. 

The infrared spectrum of CO adsorbed on a vapor derived < 1.0 nm platinum colloid stabilized by iro-butylaluminoxane in methylqrclohexane showed only a linear CO stretch at 2035 cm. This particle size is witliin the range for the larger molecular platinum carbonyl duster anions, and the colloidal platinum can in fact be hydrolysed to mixtures of [Pt9(CO)ig] and [Pti2(CO)24] after CO adsorption. [229]... 

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