Activation of Metallacyclopropenes, five‐membered Metallacyclocumulenes and Metallacyclopentynes of Zirconium with ⁱBu₂AlH

Abstract

The recently described reaction products of zirconacyclopropenes Cp′2Zr(η2‐Me3SiC2SiMe3) and five‐membered zirconacyclocumulenes (zirconacyclopenta‐2,3,4‐trienes) Cp*2Zr(η4‐1,2,3,4‐RC4R), Cp* = η5‐pentamethylcyclopentadienyl, R = Me, Me3Si and Ph, with i‐Bu2AlH are active catalysts in the polymerization of ethylene and in the ring opening polymerization of ε‐caprolactone. Here we describe the different activity of these complexes after thermal activation or if additional i‐Bu2AlH together with water are added. These results are compared to those which were obtained with the complexes Cp2Zr(η4‐1,2,3,4‐H2C4H2), rac‐(EBTHI)ZrF2, rac‐(EBTHI)ZrCl2, [rac‐(EBTHI)Zr(H)(µ‐H)]2 and rac (EBTHI)Zr(F)CH2‐CH2(2‐Py) after activation with i‐Bu2AlH together with water.

Reactions of Five-Membered Metallacyclocumulenes Cp2M(η4-t-Bu-C4-t-Bu) (M = Ti, Zr) with Diisobutylaluminum Hydride

“…For the corresponding complexes with pentamethylcyclopentadienyl ligands and different substituents at the C 4 chain Cp* 2 Zr(η 4 -R-C 4 -R) (R = Me 3 Si, Me, Ph) the reactivity toward the Lewis acids B(C 6 F 5 ) 3 6 and i-Bu 2 AlH 7 and the catalytic activity in the polymerization of ethylene and ε-caprolactone was investigated in detail. 8 In this case a very strong influence of the substituents at the metallacyclic system on the nature of the reaction products was found. Very recently we described reactions of Cp 2 M(η 4 -t-Bu-C 4 -t-Bu) (M = Ti, Hf) with B(C 6 F 5 ) 3 or i-Bu 2 AlH 9 (Scheme 1).…”

Peculiarities of Vibrational Spectra and Electronic Structure of the Five‐Membered Metallacyclocumulenes of the Group 4 Metals

“…[1][2][3] These complexes are of great interest, not only theoretically as aromatic organometallic compounds, but also practically, because some of their derivatives are active catalysts in the polymerization of olefins and ε-caprolactone. [4] The three complexes are isostructural and display bent metallocene structures that contain a planar five-membered metallacycle (Figure 1). The synthesis and X-ray structures of related substituted Zr complexes, Cp* 2 Zr(η 4 -RC 4 R) (R = Me, Ph, SiMe 3 ) and Cp* 2 Zr(η 4 -tBuC 4 -CϵCtBu) (4), have also been reported, [5] and their structural features are close to those of 2.…”

“…[4] The three complexes are isostructural and display bent metallocene structures that contain a planar five-membered metallacycle (Figure 1). The synthesis and X-ray structures of related substituted Zr complexes, Cp* 2 Zr(η 4 -RC 4 R) (R = Me, Ph, SiMe 3 ) and Cp* 2 Zr(η 4 -tBuC 4 -CϵCtBu) (4), have also been reported, [5] and their structural features are close to those of 2.…”

“…A family of novel-type compounds, namely, the smallest metallacyclic cumulenes of the type Cp 2 M(η 4 -tBuC 4 tBu) [M = Ti (1), Zr (2), Hf (3)] has been synthesized and characterized by XRD and NMR spectroscopy. [1][2][3] These complexes are of great interest, not only theoretically as aromatic organometallic compounds, but also practically, because some of their derivatives are active catalysts in the polymerization of olefins and ε-caprolactone.…”

Synthesis and crystal structure of the first five-membered ansa-metallacyclocumulene rac-(ebthi)Zr(η4-t-Bu-C4-t-Bu)

“…Metallacyclocumulene complexes with pentamethylcyclopentadienyl ligands and different substituents except tbutyl at the C 4 chain Cp* 2 M(η 4 -R-C 4 -R) (M = Zr, R = SiMe 3 , Me, Ph) were also synthesised and characterised [7]. In the reactivity of these complexes towards the Lewis Acids B(C 6 F 5 ) 3 [8] and i-Bu 2 AlH [9] as well as in the catalytic activities in the polymerization of ethylene [10] and ε-caprolactone [9] a very strong influence of the substituents at the metallacyclic system on the nature of the reaction products was found. Therefore we were interested in the synthesis and structural characterisation of metallacyclocumulenes Cp 2 M(η 4 -t-Bu-C 4 -t-Bu) with different substituents at the cyclopentadienylringsystem.…”