Platinum carbonyl cluster, isolation

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. 

Cluster Compounds.—An interesting new series of platinum carbonyl dianions of formula [Pt3(CO)3(p2-CO)3]2 n = 2—5) have been synthesized by reduction of [PtClg]2" with CO and methanolic NaOH.107 Species with decreasing n were isolated with increasing concentration of reducing agent (equation 18). The X-ray... 

Trinuclear clusters of platinum carbonyls are more common. These have been prepared by the reaction of [Pt(CO)2L with phosphine ligands the reduction of PtHXL2 with hydrazine in the presence of CO, and the reductive elimination of hydrogen from fra s-PtH2(PCy3)2 in the presence of The initially formed Pt3(CO)4L4 has been isolated for L = PPh3,... 

Work with the platinum triangle 20 pioneered by Puddephatt and co-workers has continued." Isocyanide ligands have been used to displace carbonyl ligands, and complex 21 is the first Pt3 cluster to have been isolated without a bridging atom (Scheme 4). Aspects of the structures of the isocyanide compounds are discussed in Section 8.07.2.6. 

---