Bimetallic Titanocene or Zirconocene/Aluminium Complexes as Active Catalysts in Lactone Polymerization Reactions

Abstract

The metallocene alkyne complexes [Cp 2 M(L)(η 2 -Me 3 SiC 2 R)] react with diisobutylaluminium hydride at room temp. by addition of HAl(iBu) 2 to yield the heterobimetallic complexes [{Cp 2 M}(µ-η 1 :η 2 -RCCSiMe 3 )(µ-H){Al(iBu) 2 }] [{Cp 2 M}: (η 5 -C 5 H 5 ) 2 Ti, R = Ph 1, R = SiMe 3 2; {Cp 2 M}: (η 5 -C 5 H 5 ) 2 Zr, R = SiMe 3 3; {Cp 2 M}: (ebthi)Zr, R = SiMe 3 4] {ebthi: rac-[1,2-ethylene-1,1Ј-bis(η 5 -tetrahydroindenyl)]}. Complexes 1−4

A Recoverable, Metal-Free Catalyst for the Green Polymerization of ε-Caprolactone

“…Previous examples of metal complexes used as catalysts include tin, 2,6,[15][16][17][18][19][20][21] aluminum, 6,10,18,19,[22][23][24][25][26][27] iron, 6,18 scandium, 1,12,28 yttrium, 14,18,[29][30][31][32][33][34][35] zinc, [36][37][38][39] and other metals. 1,14,18,19,24,25,[30][31][32][33][34][40][41][42][43] Although in a few of these systems the metal com...…”

Dinuclear dialkoxo-bridged cyclopentadienylsiloxo titanium complexes

“…Similar behaviour was described for a titanium-aluminium dinuclear compound. 43 Activation of e-CL with complexes 4 and E proceeded in both cases by cleavage of the acyl-oxygen bond, confirmed by 1…”

“…Similar behaviour was described for a titanium-aluminium dinuclear compound. 43 Activation of e-CL with complexes 4 and E proceeded in both cases by cleavage of the acyl-oxygen bond, confirmed by 1 The reactivity of the chloro derivatives 1a and 1b toward Al(C 6 F 5 ) 3 depends on the type of bridging dialkoxo ligand, the ethyleneglycolate bridge is totally transferred to aluminium whereas substitution of one chloro ligand is preferred for the catecholate-bridged compound 1b. This difference is attributed to the lesser accessibility of the p electrons of the oxygen atoms in this last type of bridging group, due to higher arene ring acidity, which should hinder the interaction with the Lewis acid.…”

Synthesis and crystallographic characterization of [2,2-bis(η5-pentamethylcyclopentadienyl)-3,4-bis(trimethylsilyl)-2-zirconafuran-5-one-κO5]triisobutylaluminium

“…Reactions of group 4 metallocene complexes with Lewis acids such as HAl(i-Bu) 2 , Al(i-Bu) 3 and also B(C 6 F 5 ) 3 are therefore of great interest and have been studied intensively (Brintzinger et al, 1995). It has been reported previously that titanaand zirconacycles react readily with Al(i-Bu) 3 /HAl(i-Bu) 2 to give either heterobimetallic complexes with interesting structural features (Erker et al, 1992;Arndt et al, 2001) or zwitterionic binuclear compounds (Erker et al, 1992;Burlakov et al, 2004Burlakov et al, , 2006Burlakov et al, , 2011. The latter demonstrated remarkable catalytic activity in the ROP of "-caprolactone (Arndt et al, 1996;Arndt et al, 1997).…”