A study of sulphur substituted alkyl complexes of platinum and palladium
The preparations of [(PR'3)2M(C1I2SR)CR], it - Pd, Pt;-"R - t4'e, Ph, p-tolyl; PR's - PPH3, PMePh are described. Treatment of the complexes with metal salts resulted in metathetic replacement of Cl. The reactions of I(PR'3)2M(CH2SR)X], X -'Br, I, SCN, SnC13 and NO3 with halogens, alkyl halides, proton acids and sulphenyl chlorides were carried out and comparisons made with the corresponding reactions of simple alkyl-metal complexes. Reaction with halogens leads to rapid metal-carbon bond cleavage and formation of RC112SX, where X is either the ligand originally bound to the complex or the reacting halogen, a mixture of both sulphides often being obtained. In the reactions with alkyl halides, methyl iodide, ethyl iodide or ethyl bromide, exchange of X for I or Br is observed. Monitoring a series of reactions with alkyl halides by 1H NMR spectroscopy enabled some reactivity sequences to be established. It was found that reaction of palladium complexes was more rapid than that of the corresponding platinum complexes and the order of reactivity of the alkyl halides was Met > EtI > EtBr. The reactions with trifluoroacetic acid and hydrogen chloride were studied by 1H NMR spectroscopy. A low concentration of acid reversible protonation, probably of the sulphur atom was observed and at higher acid concentrations, metal-carbon bond cleavage was observed. The reactions with sulphenyl chlorides were not fully explained by carbon-metal bond cleavage did not occur. The behaviour of [(PPh3)2Pd(CH2SMe)C1(PPh3)2Pd(CH2SPh)Cl and [(PMePh2)2Pd(CH2SMe)Cl] in solution was studied by osmotic molecular weight and conducitivity. The isolation of the monophosphine complex (PPh3)Pd(CH2SMe)Cl is described. The behaviour of the bisphosphine and monophosphine complexes in solution in the presence of added ligandswas investigated by 1H NMR spectroscopy. The reaction of the monophosphine complex with alkyl halides and proton acids was examined. In the alkyl halide reactions exchange was very slow. Similarily the acid reactions were much slower than with the sulphide analogues but metal-carbon bond cleavage was again observed.The complexes [(PR'3)2Pd2CH2S(O)R]X, R - Me, Ph, p-tolyl: PR's - PPh3, PMePh2:X - Cl, Br, I were prepared. Reactions between [(PPh3)2Pd CH2S(O)Me]Br and methyl iodide, trifluoroacetic acid, thiols and sulphenyl chlorides were examined. Exchange of Br for I occurred with methyl iodide. Little change occurred with low concentrations of acid. In the thiol reactions reduction of the sulphoxide group occurred to give a palladium - sulphide complex. In the sulphenyl chloride reactions reduction of the sulphoxide group and metal - carbon bond cleavage occurred.The attempted preparations of (PR'3)2M[(CH2)nSR]X n - 2, 3 by oxidative additionof X(CH2)nSR to M(PR'3)a and by insertion of vinyl or alkyl sulphides into metalhydride bonds are described.