Platinum complexes carbonyl addition reactions

Attempts have been made to mimic proposed steps in catalysis at a platinum metal surface using well-characterized binuclear platinum complexes. A series of such complexes, stabilized by bridging bis(diphenyl-phosphino)methane ligands, has been prepared and structurally characterized. Included are diplati-num(I) complexes with Pt-Pt bonds, complexes with bridging hydride, carbonyl or methylene groups, and binuclear methylplatinum complexes. Reactions of these complexes have been studied and new binuclear oxidative addition and reductive elimination reactions, and a new catalyst for the water gas shift reaction have been discovered. 

One or two minor points may be added to Table 8 above the adducts of aldehydes and ketones to palladium and platinum complexes react with SO2, CO2 and NO2 with displacement of the organic moiety to give the products expected for addition of these molecules to a dioxygen complex diphenylacetylene displaces both the carbonyl and the dloxygen ligand Adducts of CS2 and thiourea have also been reported The products obtained with NO2 depend on the reaction conditions, especially the solvent reaction of NO2 with (r-BuNC)2M02 gives a trans dinitrate for M = Ni and a cis dinitrate for M = Pd ). 

Extensive mechanistic studies have been performed on reactions catalyzed by rhodium and platinum complexes containing enantiopure C2-symmetric diphosphine ligands.As discussed above, (1) the formation of the Tr-olefin-Rh(H) complex 19, (2) stereospecific cis addition of the hydridorhodium to the coordinated olefin to form the alkyl-Rh complex 20 (and then 2, and (3) the migratory insertion of a carbonyl ligand giving the acyl-Rh complex 17 with retention of configuration, have been established in the hydroformylation of 1-alkenes or substituted ethenes. Thus, it is reasonable to assume that the enantioselectivity of the reaction giving a branched aldehyde is determined at the diastereomeric (1) TT-olefin-Rh complex 19 formation step, (2) alkyl-Rh complex 20 formation step, or (3) acyl-Rh complex 17 formation step. 

An attempt was also made to produce 0-iodo acyl iodides by the reaction of iodine, carbon monoxide and olefins in the presence of palladium or platinum chloride. This is, in effect, an attempt to make Dr. Tsuji s reaction catalytic rather than stoichiometric. No carbonyl insertion occurred at 1 atm. of carbon monoxide. However, it was found that iodination of the olefin was catalyzed by platinum olefin complexes and that an additional increase in catalytic activity accompanied the presence of carbon monoxide. There has been much speculation at this conference concerning the possibility of affecting catalytic activity by changing the ligands in the coordination sphere of the catalyst. This would appear to be such a case. 

Carbonyl halide complexes of platinum(IV) are less common. The reaction of [Pt(CO)2]s with chloride ion in an aqueous solution of iron(HI) ions gives Pt(CO)H2Cl2, which adds chloride to give Pt(CO)H2ClJ.313,314 Addition of chlorine to a thionyl chloride solution of Pt(CO)2Cl2 at room temperature results in the rapid formation of Pt(CO)Cl (equation 106), which shows a carbonyl stretch at 2191 cm-1. The yellow-orange compound is stable toward Cl- but reacts with water to form C02.315... 

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