One-pot synthesis of an ionic half-sandwich complex of neodymium. Application to isoprene polymerisation catalysis

Abstract

The reaction of one equivalent of Nd(BH 4 ) 3 (THF) 3 with an half equivalent of dialkylmagnesium in the presence of a stoichiometric amount of pentamethylcyclopentadiene cleanly affords a new kind of half-sandwich of neodymium that is stable toward comproportionation. This strategy can be advantageously applied to generate in situ catalysts allowing the controlled polymerisation of isoprene. To cite this article: M. Visseaux et al., C. R. Chimie 10 (2007). Ó 2007 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved. RésuméLa réaction d'un équivalent de Nd(BH 4 ) 3 (THF) 3 avec un demi-équivalent de dialkylmagnesium en présence d'une quantité stoechiométrique de pentamethylcyclopentadiène conduit de façon univoque à un hémimétallocène de néodyme d'un nouveau type, stable vis-à-vis de la comproportionation. Cette statégie peut être appliquée de façon avantageuse pour générer in situ des catalyseurs permettant la polymérisation contrôlée de l'isoprène. Pour citer cet article : M. Visseaux et al., C. R. Chimie 10 (2007).

Borane and Borohydride Complexes of the Rare‐Earth Elements: Synthesis, Structures, and Butadiene Polymerization Catalysis

“…To the best of our knowledge, the BH 4 À groups react like pseudohalides in all of these metathetical reactions. [10,[19][20][21][22][23][24][25][26][27][28][29][30][31] Thus, no redox reactions of the BH 4 À anions were observed. In contrast, in salt metathesis the BH 4 À groups act like innocent leaving groups forming MBH 4 (M = Li, Na, K) as by-products.…”

“…Keywords: boron · chelates · N ligands · polymerization · rare earths tential. Thus, the reaction of [LnA C H T U N G T R E N N U N G (BH 4 ) 3 A C H T U N G T R E N N U N G (thf) n ] with alkalimetal cyclopentadienyl derivatives resulted in different monocyclopentadienyl complexes [10,[19][20][21][22] such as [Ln-A C H T U N G T R E N N U N G (BH 4 ) 2 (h 5 -C 5 HiPr 4 )A C H T U N G T R E N N U N G (thf)] (Ln = Sm, Nd) [23] and metallocenes such as [LnA C H T U N G T R E N N U N G (BH 4 )A C H T U N G T R E N N U N G (h 5 -C 5 Me 5 ) 2 ]. [24,25] Post-metallocene complexes such as alkoxides, [19,26,27] guanidinates, [28][29][30] and cyclooctaA C H T U N G T R E N N U N G tetA C H T U N G T R E N N U N G raene [22,31] derivatives could also be obtained by salt metathesis.…”

Precisely Controlled Polymerization of Styrene and Conjugated Dienes by Group 3 Single‐Site Catalysts

“…Visseaux reported an elegant alternative method of “borohydride/alkyl (B/A) route” for preparing half‐sandwich based early lanthanide catalysts, which showed similar efficiencies as their neutral homologues . Two anionic (Cp′)Nd(BH 4 ) 3 species and one cationic Mg(THF) 6 (Cp′=C 5 Me 5 , 85 ; Cp′=C 5 H 5 , 86 ; Cp′=C 5 H 2 Ph 3 , 87 ) were synthesized, with high trans ‐1,4‐regularity (98.2 %), and controllable polymerization capability.…”

Bis(phosphinimino)methanide borohydride complexes of neodymium and scandium

“…If the BH 4 À groups are considered as monodentate and the {CH(PPh 2 NSiMe 3 ) 2 } À ligand as tridentate the structure of compound 1 reveals a six-fold coordination sphere of the ligands around the metal atom resulting in a distorted octahedral coordination polyhedron (e.g. B1eNdeB2 100.15 (11) and B1eNdeC1 152.47 (9) [35]. Single crystals of compound 2 were obtained as colorless plates from hot toluene.…”

“…In most of these metathetical reactions the BH 4 À groups reacted like a pseudohalide [9,11,13,15,16,19,20,22,33e38]. By using this approach, borohydride derivatives of the rare earth elements, such as mono cyclopentadienyl complexes, [11,13,15,16,34,35] metallocenes, [9,22] alkoxides, [16,19,36] guanidinates [20,33,37] and cyclooctatetraene complexes [34,38] have been prepared. Although BH 4 À is isosteric with Cl À , it is a much more electrondonating ligand [39], therefore allowing the isolation of otherwise unsaturated and inaccessible metallic species.…”