Butadiene complexes with platinum

Some [MX]+ ions enter into reactions in which the ligand X and the reacting molecule become chemically bonded. Polymerization processes have been observed involving the [MC4H4]+ ions (147). The butadiene complex ions [MC4H4]+ of Co and Ni are unreactive to ethyne but the Fe, Ru, and Rh ions react to yield benzene and the bare metal ion. The [MC4H4]+ complex ions of Os+, Ir+, and Pt+ react with ethyne to form the MC4I I4 + ions that probably correspond to the benzyne complexes previously observed for platinum (126). 

When polyolefins react with platinum(II) three types of reaction may occur (i) platinum or some other decomposition products may be produced as with hexa-2,4-diene or divinyl ether 124), (ii) the diene may act as a bridging group joining two platinum atoms to give binuclear complex salts, as do butadiene 67, 138) and hexa-1,5-diene 124) or (iii) the olefin may chelate to one platinum atom. 

Diaza-l,3-butadienes niobium complexes, 5, 89 with platinum(II), 8, 463... 

Protonation of the dimethylplatinum complex having a 1,4-diaza-l,3-butadiene ligand by HBF4 in MeCN produces a mixture of the cationic hydrido(dimethyl)platinum(iv) 918 and methylplatinum(ii) complex 919, depending on the amount of MeCN used (Equation (172))/ The results indicate that protonation occurs at the Pt center rather than the Me ligand. Distribution of the product of the protonation by HOTf is consistent with a mechanism involving an equilibrium between the cationic hydrido(dimethyl)platinum(iv) intermediate and the cationic methylplatinum(ii) complex with a coordinated methane molecule (Equation (173)). ... 

With the exception of the pentacoordinate -butadiene complexes PtClR( -C4H6)(dmphen), which have been previously mentioned (Section 9.2.1.2), the complexes reported in this section feature -cyclic-poly-alkene, although if-.rf (or rf) 1,3-diene-platinum species will be considered in Section 9.5 (complexes with... 

Platinum complexes Pt(PPh3)4 and PtCl2(PPh3)2, either alone or in combination with CP3CO2H, catalyze the selective monohydroamination of 1,3-butadiene with BnNH2 or PhNH2 (Eq. 4.49) in moderate yields [185]. Pd(0Ac)2/CF3C02H is also an efficient but less active catalytic system for this reaction [185]. 

The products of electrochemical oxidation of conjugated dienes are considerably affected by the reaction conditions such as the material of the electrode, the supporting electrolyte and the solvent. The oxidation of butadiene with a graphite or carbon-cloth anode in 0.5 M methanolic solution of NaClCU mainly yields dimerized products along with small amounts of monomeric and trimeric compounds (equation 5)1. The use of platinum or glassy carbon mainly gives monomeric products. Other dienes such as isoprene, 1,3-cyclohexadiene, 2,4-hexadiene, 1,3-pentadiene and 2,3-dimethyl-l,3-butadiene yield complex mixtures of isomers of monomeric, dimeric and trimeric compounds, in which the dimeric products are the main products. 

Butadienes give a complex mixture of methoxylated products by electrochemical oxidation in methanol with sodium perchlorate as supporting electrolyte [44]. Dimethoxybutenes are formed together with dimers from reaction of medioxybu-tenyl radicals. A platinum anode gives the highest yields of monomeric products while graphite anodes yield only dimeric products. This is a distinction from the... 

Platinous compounds [see specific compounds under Platinum (II)] Platinum (II) chloride, 5 208 6 209 analysis of, 5 209 Platinum (IV) chloride, 2 253 Platinum (II) complex compounds, anions, with 1,4-butadiene, K2[Cl3PtC4H6PtCI3], 6 216 anions, with ethylene, [Pt(C2H4)-CU]K, 5 211, 214... 

The reactivity of platinum silylenoid 27 was explored with traditional silylene trapping reagents. While the silylenoid did not react with triethylsilane or 2,3-dimethyl-1,3-butadiene, phenylacetylene was a viable substrate, providing the me-tallocyclohexadiene 29 (Scheme 7.4).54 The formation of platinum complex 29 was hypothesized to occur via platinum cyclobutene intermediate 28, which formed on insertion of the acetylene into the platinum-silicon bond. A second molecule of phenylacetylene was then inserted into the remaining platinum-silicon bond to provide the observed product. 

Reaction of hydroxylic compounds with butadiene has been studied with palladium compounds. A common feature is the dimerization of butadiene with incorporation of functional groups from alcohols (270). l-Methoxyoctadiene-2,7 was obtained from butadiene and methanol in the presence of Pd(maleic anhydride)(PPh3)2 (273). Complex Pt(PPh3)4 has also been used, although platinum compounds were less effective. Octadienyl esters were obtained from butadiene and acetic acid in the presence of Pd(acac)2 and either PPh3 or P(OPh)3 (294). Palladium complexes were effective for the synthesis of jS,y-unsaturated esters from butadiene, methanol, and CO. The favored mechanism involved addition of a hydropalladium complex to butadiene to give an allylpalladium intermediate (46). 

The less reactive platinum complex LV reacts with butadiene similarly at RT to give the 7i-allyl complex LVI . ... 

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