Platinum allyl halides

According to Bard and Merz [108], in MeCN containing TBAP, allyl bromide and allyl iodide interact chemically with a mercury electrode to form allylmercury halides. These allylmercury halides undergo reduction to yield diallylmercury, which is itself electroactive. Allyl bromide and allyl iodide are reduced at platinum in MeCN in a two-electron process to give the allyl anion, and the allyl radical is not involved as an intermediate. Reduction of allyl halides at platinum in DMF containing TEAOTs and in the presence of trimethylchlorosilane results in silylated compounds [100]. 

Murata, M., Watanabe, S., Masuda, Y. Regio- and stereoselective synthesis of allylboranes via platinum(0)-catalyzed borylation of allyl halides with pinacolborane. Tetrahedron Lett. 2000, 41, 5877-5880. 

The organometallic chemistry of pahadium(II) is similar to that of platinum(II) except that the palladium compounds are less stable. This lability permits a wide variety of useful catalytic reactions (e.g., palladium olefin complexes in the Wacker process). Prominent examples are the formation and reaction of r-allyl complexes. The r-allyl complexes can be formed from an olefin bound to palla-dium(II) on heating or by the reaction of an allyl halide... 

Palladium-catalyzed substitution of an allylic acetate such as 37 with diboronyl reagent 24 gives good yields of allylboronates in DMSO as solvent (Equation 21) [57]. This reaction is a steieoconvergent process the boron tends to add to the least substituted end of unsymmetrical allylic units, and both E and Z isomers of acetate 37 yield the E-isomer of 38. Another drawback to this process is that the product is often formed with variable yields of the allylic dimer (e.g., 39). Allylic halides were also employed as substrates with pinacolborane as the borylating agent and a platinum catalyst [58]. 

Recently, hydrosilanes are also employed for the silylation of aryl halides in the presence of a palladium,platinum, or rhodium catalyst. In view of atom efficiency, this procedure has an advantage. Palladium-catalyzed reactions are suitable for the silylation of electron-rich aryl halides, whereas rhodium-catalysis works well with a wide range of aryl halides (Scheme 3-17). Silylation of allyl halides with trichlorosilane proceeds in the presence of a copper catalyst. ... 

The electrolysis of alkyl halides on platinum cathode and tin anode has been mentioned above. A completely different mechanism is associated with alkylation on tin cathodes. Electroreduction of allyl bromide on tin electrodes yields tetraallylstannane (Ca 90%). This is done in acetonitrile solutions with LiClC>4, Et4NBr or BujNBr as electrolyte and followed by CV with Ag/AgBr reference. Yields decrease to 78% in DMF. The proposed mechanism67 in this case is ... 

Shortly after Trost s works, two investigations demonstrated the high reactivity of platinum halide salts for this type of reactions. Blum reported a PtCU-catalyzed rearrangement of allyl propargyl ethers to 3-oxabicyclo[4.1.0]-heptenes (Scheme 79).294 This series of reactions also represented the premiere entry into the versatile formation of cyclopropyl products based on skeletal rearrangements of enynes.295 This intriguing aspect is discussed further. 

Allyl Complexes. Allyl complexes of thorium have been known since the 1960s and are usually stabilized by cyclopentadienyl ligands. Allyl complexes can be accessed via the interaction of a thorium halide and an allyl grignard. This synthetic method was utilized to obtain a rare example of a naked allyl complex, Th(r 3-C3H5)4 [144564-74-9], which decomposes at 0°C. This complex, when supported on dehydroxylated y-alumina, is an outstanding heterogeneous catalyst for arene hydrogenation and rivals the most active platinum metal catalysts in activity (17,18). 

Cyclopentadienyl)( / -allyl)Ni and -Pt complexes are formed when NiClj and PtClj are treated sequentially or simultaneously with allylmagnesium halides and LiCp or NaCp. The voltatile complexes are isolated by distillation or sublimation from the reaction residue after evaporation of the solvent. Platinum(II) olefin complexes afford the same product when treated similarly ... 

Vinyl halides add to allylic amines in the presence of Ni(cod)2 where cod=l, 5-cyclooctodine, followed by reduction with sodium borohydride. Aryl iodides add to alkynes using a platinum complex in conjunction with a palladium catalyst. A palladium catalyst has been used alone for the same purpose, and the intramolecular addition of a arene to an aUcene was accomplished with a palladium or a GaCl3 catalyst, " AUcyl iodides add intramolecularly to aUcenes with a titanium catalyst, or to alkynes using indium metal and additives. The latter cyclization of aryl iodides to alkenes was accomplished with indium and iodine or with Sml2. " ... 

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