Highly Branched Polyisobutylene by Radical Polymerization under Li[CB₁₁(CH₃)₁₂] Catalysis

In the presence of a nonoxidizing radical initiator, azo-<i>tert</i>-butane, and a high concentration of LiCB₁₁(CH₃)₁₂, isobutylene undergoes thermal or light-induced radical polymerization to <i>b</i>-PIB, a highly branched polymer of modest molecular weight (mostly a few thousand and up to ∼25 000 g/mol based on GPC with polystyrene standards). The structure of <i>b</i>-PIB was elucidated by NMR spectroscopy of a low-molecular-weight fraction. The polymer is branched on every carbon atom of the main chain; one chain end carries an isobutenyl group, and the other carries a tert-butyl group originating in the initiator. The branches are short segments of <i>l</i>-PIB (linear polyisobutylene), on the average composed of five IB units. A mechanism of formation if this dendrimer-like structure is proposed

Oligomerization of α-olefins by the dimeric nickel bisamido complex [Ni{1-N(PMes 2 -N(μ-PMes 2 )C 6 H 4 -κ 3 N , N' , P ,-κ 1 P' }] 2 activated by methylalumoxane (MAO)

The reaction of Li2[1,2-{N(PMes2)}2C6H4], formed in situ from n-BuLi and the corresponding amines, with 1 equiv. of [NiBr2(DME)] gives [Ni{1-N(PMes2)-2-N(μ-PMes2)C6H4-κ3N,N′,P-κ1P′}]2 (1). After activation by methylalumoxane (MAO), 1 is a highly a

Synthesis, hydrosilylation reactivity and catalytic properties of group 4 ansa-metallocene complexes HMe 4 )Cl (2), Et(H)Si(C 5 HMe 4 )(C 5 H 5 ) (3), Ph(H)Si(C 5 H- Me 4 )Cl (4), Ph(H)Si(C 5 HMe 4 )(C 5 H 5 ) (5), Ph(H)Si(C 5 HMe 4 ) 2 (6), CH 2 @CHCH 2

Abstract The following ansa-ligand precursors, Et(H)Si (C 5