Platinum compounds sulfoxides

The reaction of alcohols with CO was catalyzed by Pd compounds, iodides and/or bromides, and amides (or thioamides). Thus, MeOH was carbonylated in the presence of Pd acetate, NiCl2, tV-methylpyrrolidone, Mel, and Lil to give HOAc. AcOH is prepared by the reaction of MeOH with CO in the presence of a catalyst system comprising a Pd compound, an ionic Br or I compound other than HBr or HI, a sulfone or sulfoxide, and, in some cases, a Ni compound and a phosphine oxide or a phosphinic acid.60 Palladium(II) salts catalyze the carbonylation of methyl iodide in methanol to methyl acetate in the presence of an excess of iodide, even without amine or phosphine co-ligands platinum(II) salts are less effective.61 A novel Pd11 complex (13) is a highly efficient catalyst for the carbonylation of organic alcohols and alkenes to carboxylic acids/esters.62... 

The redox characteristics, using linear sweep and cyclic voltammetry, of a series of (Z)-6-arylidene-2-phenyl-2,3-dihydrothiazolo[2,3-r][l,2,4]triazol-5(6//)-ones 155 (Figure 24) have been investigated in different dry solvents (acetonitrile, 1,2-dichloroethane, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO)) at platinum and gold electrodes. It was concluded that these compounds lose one electron forming the radical cation, which loses a proton to form the radical. The radical dimerizes to yield the bis-compound which is still electroactive and undergoes further oxidation in one irreversible two-electron process to form the diradical dication on the newly formed C-C bond <2001MI3>. 

Dichloro(l,5-cyclooctadiene)platinum(II) is a white, air-stable solid. The compound is slightly soluble in solvents such as chloroform, acetic acid, sulfolane (tetrahydrothiophene 1,1-dioxide), and nitromethane. It decomposes slowly upon dissolution in dimethyl sulfoxide. The p.m.r. spectrum of the compound in chloroform shows resonances at 4.38r, /pt H = 65 Hz., for the olefinic protons and 7.29-r for the methylene protons. The infrared spectrum in Nujol has strong absorption maxima at 1334, 1179, 1009, 871, 834, and 782 cm.-1. 

Although the platinum polymers share many properties with cis-DDP. one important difference between the two types of compounds has been uncovered and is indicated in Table 2. The biological activity of cis-DDP depends upon the age of the solution. A freshly prepared solution of cis-DDP in either dimethyl sulfoxide or cell culture medium is 100-fold more active than a solution which has been stored for several months. This loss of activity is presumably due to the reaction of cis-DDP... 

The inhibitors act as ligands, blocking the hydrosilylation reaction by coordination to the metal center, but vmder conditions employed for cure, they release the active catalyst. The numerous vmsaturated organic compounds, such as esters, alcohols, ketones, sulfoxides, phosphines, phosphites, nitriles, azodicarbonyl compounds, triazoline, dienes, amine N-oxides, hydroperoxides, and others, are known and have been reported as platinum catalyst inhibitors during the cure of silicon rubber through addition processes (3,4). The unsaturated diesters (e.g., maleates and fumarates) are the most important and commonly used platinum inhibitors in industrial curing processes and have been described in many articles and patents. 

There are many examples of the synthesis of homoleptic solvento-complexes by halide abstraction from compounds containing both coordinated halides and solvento-ligands. Palladium chloride is known to dissolve in nitriles, dimethylformamide, and dimethyl sulfoxide with the formation of complexes of the type [PdCl2(solv)2] which can be isolated as solids.3 The reaction of [PdCl2(RCN)2] with an excess of silver ions s is a convenient method for the synthesis of [Pd(RCN)4]2+. The tetra(acetonitrile)-platinum(II) and tetra(propionitrile)platinum(II) salts have been prepared in this way (Scheme 4.6). Wayland and Schramm have synthesized homoleptic palladium(II) complexes with DMSO, DMF, and DMAA in a similar manner. 

The antitumor activities of some sulfoxide complexes themselves, [PtCl(RR S0)(biL)]N03 (biL are diamines), have come under scrutiny, being the first active compounds of this sort with sulfur-bonded ligands. The nature (and, when appropriate, the chirality) of the sulfoxides has a marked effect on activity. The sulfoxides can be displaced by Cl or H2O, and the lability order is Ph2SO>PhMeSO>(tol)MeSO>(PhCH2)2SO> (PhCH2)MeSO>dmso. Initial loss of RR SO was precluded as the mechanism of the antitumor activity. Possibly RR SO is eliminated after the platinum has bound to DNA. 

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