Controlled trans‐stereospecific polymerization of isoprene with lanthanide(III) borohydride/dialkylmagnesium systems: The improvement of the activity and selectivity, kinetic studies, and mechanistic aspects

Abstract

Neodymium trisborohydride, associated with MgR2 alkylating agents, affords an efficient initiator for the stereospecific polymerization of isoprene. This system presents good activity (150 kg of polyisoprene/mol of Nd/h; 95% yield in 2 h) and is trans‐stereospecific (up to 97.7%), and its polymerization shows a quasi‐living character. The molecular weights are controlled by the [Isoprene]/[Nd] ratio, with a polydispersity index lower than 1.6. A full study is presented here, including the influence of the nature of the alkylating reagent (MgR2), the solvent, the reaction temperature, the [MgR2]/[Nd] ratio, and the replacement of neodymium by other lanthanides. This work also includes a kinetic study of the system and a detailed NMR study of the microstructure of the trans‐polyisoprene obtained, providing mechanistic insights about the polymerization reaction. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2400–2409, 2007

Lanthanide Metal‐Organic Frameworks as Ziegler–Natta Catalysts for the Selective Polymerization of Isoprene

“…As already reported with that kind of co-catalyst, [19,28] the selectivity is clearly shifted to 1,4-trans.…”

“…The selectivity was determined by 1 H NMR as previously described in ref. [19] and was further confirmed by 13 C NMR quantitative sequence using the zg-ig Bruker program with delay D1 ¼ 5 s. Size exclusion chromatography (SEC) was performed in tetrahydrofuran (THF) as eluent at 20 8C using a Waters 410 refractometer, and a Waters Styragel column (HR2, HR3, HR4, HR5E) calibrated with polystyrene standards. Infrared (IR) characterizations were performed using a PerkinElmer Spectrum One FT-IR Spectrometer equipped with an MIR TGS detector.…”

Bis(phosphinimino)methanide Borohydride Complexes of the Rare‐Earth Elements as Initiators for the Ring‐Opening Polymerization of ε‐Caprolactone: Combined Experimental and Computational Investigations

“…[22][23][24] Later on, greater value was given to these original species in the promotion of rare-earth borohydride organometallic chemistry [25][26][27][28] and in their use as efficient catalysts for the (co)polymerization of ethylene, [29][30][31] isoprene, [31][32][33][34][35] styrene, [34,36] and some polar monomers such as lactide, [37][38][39][40][41][42] e-caprolactone, [37][38][39][43][44][45][46][47][48][49][50][51][52] trimethylene carbonate, [52] and methyl methacrylate. [53][54][55][56][57] Also, some rare-earthmetal borohydride derivatives such as metallocenes, [31,46] mono-cyclopentadienyl complexes, [25,33,[35][36]…”

Mixed borohydride-chloride complexes of the rare earth elements

“…Also the derivatives of [Ln(BH 4 ) 3 (THF) 3 ] such as mono cyclopentadienyl complexes [3,5,[13][14][15][16], metallocenes [17,18], alkoxides [13,19,20], guanidinates [21][22][23] and cyclooctatetraene [15,24] have been used to prepare a large number of lanthanide borohydride derivatives, which also have a high catalytic potential. To obtain these derivatives, [Ln(BH 4 ) 3 (THF) 3 ] were reacted in a salt metathesis reaction with alkali metal reagents. Beside their catalytic application, borohydride compounds of various metals have also been investigated in general as potential hydrogen storage material [25].…”

“…Besides their synthetic potential, lanthanide trisborohydrides [Ln(BH 4 ) 3 (THF) 3 ] [1] are used today as efficient catalysts for the polymerization of isoprene [2][3][4][5], styrene [4,6] and some polar monomers such as e-caprolactone [7][8][9], methyl metacrylate [10,11], and trimethylene carbonate [12]. Also the derivatives of [Ln(BH 4 ) 3 (THF) 3 ] such as mono cyclopentadienyl complexes [3,5,[13][14][15][16], metallocenes [17,18], alkoxides [13,19,20], guanidinates [21][22][23] and cyclooctatetraene [15,24] have been used to prepare a large number of lanthanide borohydride derivatives, which also have a high catalytic potential.…”