Related Experiment Video
Updated: Jan 29, 2026

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes
Published on: November 21, 2017
Stereospecific polymerization of conjugated dienes using neodymium alkylborohydride complexes
Ryo Tanaka1, Yuto Shinto, Ryusei Matsuzaki
1Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima, 739-8527, Japan. rytanaka@hiroshima-u.ac.jp.
Abstract:
Two neodymium alkylborohydride complexes that differ with respect to the number of hydrides on the boron center were synthesized and characterized. The μ2-ligated complex exhibits Nd-B bond lengths that are approximately 10% longer than those in previously reported μ3-ligated borohydride complexes. For the μ3-alkylborohydride complex, the Nd-H-B stretching bands observed by IR spectroscopy suggested stronger borohydride coordination than that of [BH4]-, which is probably due to the electron donation of the alkyl groups. These newly prepared complexes successfully promoted trans-1,4 specific polymerization of conjugate dienes upon activation by Bu2Mg, whereas activation of these complexes by Bu2Mg/MMAO gave cis-1,4 regular polymer. The trans-1,4 defect of the polyisoprene obtained from the Nd μ2-alkylborohydride complex/Bu2Mg/MMAO system (<2%) was much lower than that obtained from previously reported μ3-BH4-ligated neodymium complex (11%). Moreover, μ2-alkylborohydride complex was a good initiator for the polymerization of MMA, probably because of its anionic nature.
Related Concept Videos
Structure of Conjugated Dienes
Conjugated dienes are compounds characterized by the presence of alternating double and single bonds. In a conjugated system like 1,3-butadiene, the unhybridized 2p orbital on each carbon overlaps continuously, allowing the π electrons to be delocalized across the entire molecule. In contrast, this type of overlap does not occur in cumulated and isolated dienes, such as 2,3-pentadiene and 1,4-pentadiene, respectively. Instead, the π electrons remain localized between the double...
Stability of Conjugated Dienes
A comparison of the enthalpies of hydrogenation of dienes reveals that conjugated dienes release less heat on hydrogenation, rendering them more stable than their nonconjugated analogs.
Olefin Metathesis Polymerization: Acyclic Diene Metathesis (ADMET)
Similar to cross-metathesis, ADMET also involves the formation of metallacyclobutane intermediate by [2+2] cycloaddition of one of the double bonds of a terminal diene with...
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
Polymer Classification: Stereospecificity
Conjugated Proteins
Nucleoproteins are protein complexes that contain nucleic acids, categorized as deoxyribonucleoproteins (DNPs) or ribonucleoproteins (RNPs) respectively. The nucleosome is a typical example of a DNP where nuclear DNA is associated with histone proteins. The major antigen for the Covid-19 virus SARS-CoV is an RNP that is critical...

