Syndiotactic-Specific Polymerization of 4-Methyl-1,3-pentadiene:  Insertion on a Mt−CH₃ Bond

Polymerization of 4‐Methyl‐1,3‐pentadiene with Catalysts Based on Cyclopentadienyl Titanium Chlorides: Effect of anti/syn Isomerism of the Allylic Group on the Chemoselectivity and the Role of Backbiting Coordination in 1,3‐Diene Polymerization

“…This interpretation accounts well for the results reported in the literature [7] for the first insertion step of MP into the Ti-Me bond of the CpTiCl 3 -MAO system. anti-Allyl groups are predominantly formed on MP insertion into the Ti-Me bonds.…”

“…[7] chain ends (a) and (b) are formed in a ratio of about 3/7, which is in good agreement with the data obtained in this work with CpTiCl 3 -MAO.…”

“…However, backbiting coordination has recently received new attention, [7,8] and it has again been reported that it may affect polymerization chemoselectivity. The experimental basis for this new interest is as follows.…”

Copolymerization of styrene with(Z)-1,3-pentadiene in the presence of a syndiotactic-specific catalyst

“…The spectrum of the sample 2, prepared at /20ЊC, is similar to that of sample 10; in fact, in temperatures (/20 and 020ЊC) in the presence of the same catalyst (CpTiCl 3 -MAO) that promotes syndiotactic-specific homopolymerization of styrene at both temperatures, 8 but 1,2-syndiotacticspecific homopolymerization of (Z )-1,3-pentadiene only at 020ЊC while it promotes 1,4 cis homopolymerization at /20ЊC. The most intense 13 C resonances observed in the spectrum of the sample 10, prepared at 020ЊC, coincide with the ones observed in the spectra of the two 1,2-syndiotactic homopolymers, and, surprisingly, the fraction of the heterodiads is rather low, notwithstanding that the copolymer composition is close to equimolarity.…”

Role of back‐biting in the stereoselectivity of Ni(II)‐catalyzed butadiene polymerization

“…As a matter of fact, the organonickel compound (probably a cationic species), which promotes the polyinsertion, can exchange a hydrocarbyl group with Al( 13 CH 3 ) 3 via chain transfer to methylaluminum. 9,10 In Figure 1, the 13 C NMR spectra of a polybutadiene sample obtained at 20 8C in the presence of the already mentioned catalyst [sample 1, Fig, 1(B)] and a polybutadiene sample prepared with Al(CH 3 ) 3 , instead of Al( 13 CH 3 ) 3 [sample 2, Fig. 1(A)], are presented.…”