Propene complexes

In other examples, also involving propargyl carbonates, the parent derivative 86 was first coupled with 87 - obtained by reaction of 5-octyne with the titanium diiso-propoxide - propene complex at -50 °C, providing the titanated vinylallene 88, which on hydrolysis furnished the vinylallenes 89 in good yield [29]. Carbonate 90 in the presence of a Pd° catalyst readily decarboxylated and yielded the allenylpalladium intermediate 91, which could be coupled with various vinyl derivatives to afford the vinylallenes 92. Since X represents a functional group (ester, acetyl), functionalized vinylallenes are available by this route [30]. 

In 1961, Green and Nagy (40) reported that treatment with HCl of a <7-allyl group coordinated to iron gave a w-propene complex cation ... 

The protonation of a a-allyltungsten complex to the cationic w-propene complex and the NaBH4 reduction of this to the isopropyl complex in complete analogy to the corresponding iron compounds has been demonstrated by Green and Stear (4S) ... 

The structure and properties of the initial nickel atom-propene complex has received detailed attention by Skell. The use of isotopically labeled propenes demonstrated that exchange occurs between the 1- and 3-positions but not between either the 1- and 2- or 2- and 3-positions (10) ... 

Similarly, condensation of a mixture of CsHe and C3D6 with nickel vapor resulted in isotopic scrambling. The intraligand isomerizations may be explained in terms of a 1,3-hydrogen shift via a nf-allyl nickel hydride complex in equilibrium with a ir-propene complex, e.g.,... 

In homogeneous systems, a- and > 3-alkylallyl complexes, as well as alkylallyl carbanions, have been prepared. Furthermore, a reversible interconversion of the /3-allyl complex to the corresponding olefin complex was demonstrated by using NMR spectroscopy. Equation (9) shows an equilibration between the /3-allylhydridotrifluorophosphinenickel complex and n-bonded propene complex (20). Brennemann affirmed also that the >/3-allyldeuterio nickel complex changes exclusively to propene-l-d, or propene-3-rf, by the reversible operation of Eq. (9). 

Methyl-1-pentyne, silylformylation, 11, 507 Methyl(propene) complexes, with platinum(II), 8, 462... 

Metallacyclobutane complexes can undergo net reductive rearrangement to form alkene complexes or undergo decomposition with the liberation of free alkene. The rhodacyclobutane complex 112, for example, rearranges thermally to give propene complex 113 (Equation 33) <19980M4484>. 

Complex formation between olefins and Lewis acids has been demonstrated in a number of cases, e.g., isobutene and titanium tetrachloride (66), butene-2 and boron trifluoride (67—69), propylene and aluminum bromide (70), stflbene and various Lewis acids (71), styrene and stannic chloride (72), and in similar systems (73). Monomer-catalyst Ji-complex formation occurs during the polymerization of styrene or a-methyl styrene with chloroacetic acids (74,75). All these complexes are usually very weak and only stable at low temperatures. Evans contends (76) that isobutene and boron trifluoride do not interact because no polymerization occurs in the absence of moisture and therefore he postulates that BF3 HaO is the primary species. This does not rule out the possibility of a weak interaction between isobutene and the Lewis acid. Indeed, Nakana et al. (77) found direct evidence for the existence of boron trifluoride-propene complexes at low temperatures. 

The propene complex is the most stable and of special interest is the failure to observe any evidence for metal hydride formation prior to thermal decomposition. This contrasts markedly with the temperature-dependent equilibrium between metal-propene and metal-allyl-hydride first observed by Bonnemann (42) for the related complex [Ni(C3H6)(PF3)J and studied by variable-temperature NMR spectroscopy. 

A single barrier is often reported for propene complexes however, since the free energy of the endo isomer is usually less than that of the exo isomer, the direction of the path should be stipulated, that is, exo to endo, because the endo to exo barrier usually differs by 2 to 12kJmol . Secondly, there are two routes by which one can proceed from exo to... 

Although the analogous w-propyl and isopropyl complexes both give the 77-propene complex cation, reversal of the reaction produces only the isopropyl species. 

Many carbanions react with [Fp(olefin)] complexes to form relatively stable / -alkyliron complexes. Stabilized enolates derived from cyanoacetates, ma-lonates, acetoacetates and nitromethane react with the [Fp(styrene)]" complex almost exclusively at the benzylic carbon but react with [Fp(propene)] complexes with low regioselectivity ... 

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