Zeise s dimer

Treatment of the olefin 49 with Zeise s dimer leads to the chloroplatination complex 50 [26], The addition adduct 50 is hydrogenated stereospecifically to the trans-disubstituted chlorocyclohexane 51. The insertion of carbon monoxide into 50, in the presence of methanol, yields the ester 52 stereoselectively. 

The products of these [4 + 2 + 2]-reactions have a high level of molecular complexity, which has been used to advantage in exploring the conversion of the [4 + 2 + 2]-cycloadducts into commonly encountered ring systems. Zeise s dimer, for example, has been employed to carry out a skeletal rearrangement, as illustrated in Scheme 61, producing fused and bridged bicyclic systems found in several natural product families. 

To 0.315 g (0.536 mmol) of [(C2H4)2PtCl2]2 (Zeise s dimer) dissolved in 25 mL of diethyl ether and 5mL of toluene was added 0.219 g (1.073 mmol) of 9,10-dihydro-9,10-etheneoanthracene. The solution was stirred vigorously under N2 for 6 hr. Upon concentration of the resulting solution, a bright orange solid was produced. Filtration yielded 0.46 g of the desired product with 0.5 equiv. of toluene cocrystallized for an 85% yield. 

Zeise s dimer can catalyze a rearrangement of the fused cyclopropane 217 to afford the 3,4-dihydropyran 218 in moderate yield (Equation 101) <2003T2765>. 

Cyclic seven-membered vinyl silanes 161 were obtained by regio- and stereoselective hydrosilylation of internal alkynes catalyzed by the ruthenium complex [Cp Ru(MeCN)3]PF6, as shown in Equation (33) <2005JA10028>. Hydrosilylation of 2,2-divinyladamantane with bis(hydrosilane) species 162 in the presence of Zeise s dimer [Pt2Cl4(CH2CH2)2] gave the disilacyclic 163 in high yields (Equation 34) <19980M4267>. 

Although a variety of platinum(II)-ethylene complexes have been described (268), those most frequently encountered are Zeise s salt, K[(C2H4)PtCls] H20, and Zeise s dimer, [(C2H4)PtCl2]2- These have been employed for preparation of many other platinum(II)-olefin complexes and have been the subject of much research. 

Broad line NMR studies of Zeise s salt crystals (397) indicate that the ethylene molecule experiences large-amplitude rotational oscillations about both the double bond axis and the metal-olefin axis with relatively little distortion of the molecule being apparent. An analogous study of Zeise s dimer (497) shows similar oscillations with some moleular distortion evident. 

Both cis, trans, trans- and aii-iraws-l,5,9-cyclododecatriene yield upon reaction with Zeise s dimer in acetone, the compounds bis(olefin)-yellow-orange plates melting at about 130°C (456). Dissolution of the all-trans product in an organic solvent results in loss of olefin to produce the polymeric species (Ci2Hi8)4(PtCl2)6 (456). An attempted preparation of the platinum(II) complex of cis,[Pg.320]

C NMR, 4, 578 Spiroacefals polymers, 1, 292 Spiro[2.n]alkanes reaction with Zeise s dimer, 1, 666 Spiro-2H-1 -benzopyranindolines synthesis, 3, 750 Spirobenzopyrans reactions with acids, 3, 668 2,2 -Spirobichroman in photography, 3, 880 2,2 -Spirobichroman, 6,6, 8,8 -tetramethyl-synthesis, 3, 734 Spirobichromans synthesis, 3, 786 Spirobi(2H-chromenes)... 

Reaction of the platinum complex known as Zeise s dimer with bicyclo[l. 1.0] butane, which contains a highly strained bridging bond, gives the corresponding platinabicyclo[l.l.l]pentane (7) (equation 7.38) as a stable, crystalline solid.81... 

Another example of this type starts from exo,< xo-tetracyclo[3.3.1.0. 0 ]nonane, which reacted with Zeise s dimer, [(C2H4)PtCl2]2, to form an insoluble platinum complex. This product is solubilized with pyridine and was shown to be a metallacyclobutane complex 4. Synthesis of cxo-tricyclo[3.3.1.0 ]non-6-ene was achieved in 45-55% yield if 4 was treated with dimethyl sulfoxide. ... 

Interestingly, conversion of racemic treatment with chiral diphosphanes regenerates the cyclopropane with up to 31% ee. ... 

As a representative example, treatment of bicyclo[1.1.0]butane (1) with Zeise s dimer in acetone at 23°C for 20 minutes gives butadiene in quantitative yield. At — 45°C (48 hours) a 1 1 complex is formed in 97% yield, which upon further treatment with pyridine gives 2-[bis(pyridine)dichloroplatina]bicyclo[l.l.l]pentane (2) in 94% yield. Thermal decomposition of this complex 2 unselectively leads to a mixture of the starting hydrocarbon 1, cyclobutene (3), butadiene (4), 2-methylcyclopropene (5) and methylene cyclopropane (6). Reduction of the metallacyclic intermediate 2 with lithium aluminum deuteride leads to a bisdeuterated methylcyclopropane 7 accompanied by a bisdeuterated cyclobutane 8 and the starting material 1. ... 

Furthermore, reaction of l-/er/-butyldimethylsiloxy-l-phenylcyclopropane with Zeise s dimer takes place readily to give a high yield of the ethene complex of the /i-platinum(II) ketone 10 (R = Ph), as a chlorine-bridged dimer, based on the crystal structure. 

Reaction of alkoxycyclopropane 11, which contains an alkene moiety, with Zeise s dimer, followed by treatment with pyridine, results in a pyridine complex of the ) -platinum(II) ketone. 

Siloxycyclopropanes are also opened by platinum(II) complexes such as Zeise s dimer. - While 1-aryl-1-siloxycyclopropanes are transformed into P-platinum ketone complexes, 2-alkyl-substituted siloxycyclopropanes are isomerized cleanly to allyl silyl ethers in good yields. The reaction is quite general and proceeds with catalytic amounts of Zeise s dimer (2-10mol%) in many different suitable solvents (chloroform, dichloromethane, ethyl acetate, ethers, benzene) at ambient temperature with 100% inversion of configuration at the siloxy carbon and provides only silyl ethers of 2-methylene alkanols without contamination of doublebond isomers. ... 

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