Arsine with platinum

It was found that the platinum(II) complexes of these ligands were of two types. All isomers form compounds of the t)rpe PtBr2 (arsine) 2, some of which are illustrated in Fig. 5. In these compounds, coordination to the platinum is effected through the arsenic atom alone. In addition, the ortho isomers of both arsines form 1 1 complexes with platinum(II) bromide in which the ligand is bidentate. Both the arsenic atom and the double bond are coordinated to the platinum as shown in Fig. 6. 

These ligands all form 1 1 complexes with platinum(II) halides which are non-conductors, monomeric and, in the solid state, contain one coordinated and two free double bonds. Proton n.m.r. data indicate that all three double bonds are equivalent in solution due to a rapid equilibrium between bonded and non-bonded —CH=CH2 groups. The phosphine and arsine complexes PtBraL (L = tvpp, tvpa) react with two equivalents of bromine giving what are believed to be platinum(II) species containing one coordinated double bond and two —CHBr-CHaBr groups arising from the saturation by bromine of the two free double bonds. 

The masking of coordinated arsine toward the quaternization reaction with methyl iodide has been used to demonstrate the coordination of all of the arsenic atoms of the ligand tris(orthodiphenylarsinophenyl)arsine (QAS) in its complex with platinum (II) 9, 53). This reaction is found with uncoordinated arsines. 

The induction period can be explained as the result of reactions a or /3. The first, proposed by Heck 89), requires that tetracarbonylnickel have basic properties, but this could not be proved. In fact, the protonation reaction of carbonyls and carbonyl derivatives has been studied by Wilkinson and co-workers 64) Ni(CO)4 does react with acids but, contrary to Fe(CO)5, gives no NMR signal—indicating the formation of a hydride. However, the basic properties of some systems have been recently shown in complexes with phosphines and arsines. The platinum (0) 39, 40) derivatives yield stable hydrides according to the following equilibria ... 

J. C. Bailar, Jr., and Hiroshi Itatani, Homogeneous Catalysis in the Reactions of Olefinic Substances. VI. Selective Hydrogenation of Methyl Linoleate and Isomerization of Methyl Oleate by Homogeneous Catalysis with Platinum Complexes Containing Triphenylphosphine, Arsine or Stibine, J. Am. Chem. Soc. 89 1592 (1967). 

The cyclometallated palladium and platinum derivatives of trimesityl phosphine or arsine react with pyrazole or 3,5-dimethylpyrazole to form metal chelates 243 (E = P, As M = Pd, Pt R = H, Me) having the trans configuration (81TMC24). 

Complexes are similarly formed by polydentate phosphine and arsine ligands synthetic routes involve oxidation of the platinum(II) complex, either with the halogen or with nitric acid ... 

Platinum(IV) complexes of phosphine and arsine ligands formed by oxidation with chlorine or bromine are well known. Chloro complexes such as ci5-[PtCl2(PEt3)4]2+ can be generated by electrolysis of the platinum(II) complex c -[PtCl2(PEt3)2].433 Similar platinum(IV) complexes... 

PtBrs (arsine) 2, which are octahedral complexes of platinum(IV) in which the olefinic side chains of the ligands have been fully brominated. An alternative and more realistic formulation of these compounds is PtBr4 (arsine Bre) 2- These same compounds are formed by reaction of an excess (> 3 equivalents) of bromine with the original platinum(II) compounds. 

The platinum complex of (W fAo-aUylphenyldimethyl arsine, PtBrg (oA)2, has also been treated with bromine and the products reacted with alcohols (8, 10). Two differences in the reaction sequences are, however, observed ... 

Treatment of the chelate complexes with a large excess of bromine in hot benzene gives the same complexes PtBr4 (arsine), indicating the resistance of the metal carbon ff-bond to attack by bromine and also excluding ) their alternative formulation as dimeric platinum(II) complexes [PtBrg (arsine Br2)]2-... 

The behaviour of the phosphine complex PtBr2(ap)2 towards bromination is in marked contrast to that of PtBr2(oA)2 (the related arsine complex). Whilst the arsine complex gives platinum(IV) species on reaction with one equivalent of bromine, the phosphine complex gives the chelate compound PtBr2 (ap), and, presumably, CH2=CH CH2 ... 

Compounds of palladium and platinum in zero oxidation state are no longer rare, but there is little or no structural information available. The best ligands seem to be isonitriles, tertiary phosphines, and tertiary arsines (162-164) compounds of platinum(O) with ammonia and ethylenedi-... 

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