Synthesis, hydrosilylation reactivity and catalytic properties of group 4 ansa-metallocene complexes

Abstract

The following ansa-ligand precursors, Et(H)Si(C 5H 5) 2 ( 1), Et(H)Si(C 5HMe 4)Cl ( 2), Et(H)Si(C 5HMe 4)(C 5H 5) ( 3), Ph(H)Si(C 5HMe 4)Cl ( 4), Ph(H)Si(C 5HMe 4)(C 5H 5) ( 5), Ph(H)Si(C 5HMe 4) 2 ( 6), CH 2 CHCH 2(H)Si(C 5HMe 4)Cl ( 7), CH 2 CHCH 2(H)Si(C 5HMe 4)(C 5H 5) ( 8), CH 2 CHCH 2(H)Si(C 5HMe 4) 2 ( 9), and their lithium derivatives, Li 2{Et(H)Si(C 5H 4) 2} ( 10), Li 2{Et(H)Si(C 5Me 4)(C 5H 4)} ( 11), Li 2{Ph(H)Si(C 5Me 4)(C 5H 4)} ( 12), Li 2{Ph(H)Si(C 5Me 4) 2} ( 13), Li 2{CH 2 CHCH 2(H)Si(C 5Me 4)(C 5H 4)} ( 14) and Li 2{CH 2 CHCH 2(H)Si(C 5Me 4) 2} ( 15) have been prepared. The group 4 metal complexes, [M{Et(H)Si(η 5-C 5H 4) 2}Cl 2] (M = Ti ( 16a), Zr ( 16b), Hf ( 16c)), [M{Et(H)Si(η 5-C 5Me 4)(η 5-C 5H 4)}Cl 2] (M = Ti ( 17a), Zr ( 17b), Hf ( 17c)), [M{Ph(H)Si(η 5-C 5Me 4)(η 5-C 5H 4)}Cl 2] (M = Ti ( 18a), Zr ( 18b), Hf ( 18c)), [M{Ph(H)Si(η 5-C 5Me 4) 2}Cl 2] (M = Ti( 19a), Zr ( 19b), Hf ( 19c)), M{CH 2 CHCH 2(H)Si(η 5-C 5Me 4)(η 5-C 5H 4)}Cl 2] (M = Ti ( 20a), Zr ( 20b)) and [M{CH 2 CHCH 2(H)Si(η 5-C 5Me 4) 2}Cl 2] (M = Ti ( 21a), Zr ( 21b), Hf ( 21c)) were synthesized from the reaction of the lithium ansa-derivatives and the tetrachloride salts of the transition metal. The reactivity of the group 4 metal complexes in hydrosilylation processes has been studied. The reaction of 16b, 17a and 17b with tetravinylsilane gave [Zr{(CH 2 CH) 3SiCH 2CH 2(Et)Si(η 5-C 5H 4) 2}Cl 2] ( 22b) and [M{(CH 2 CH) 3SiCH 2CH 2(Et)Si(η 5-C 5Me 4)(η 5-C 5H 4)}Cl 2] (M = Ti ( 23a), Zr ( 23b)), respectively. The reaction of 17a and 17b with dimethyldivinylsilane yielded the hydrosilylation products [M{(CH 2 CH)Me 2SiCH 2CH 2(Et)Si(η 5-C 5Me 4)(η 5-C 5H 4)}Cl 2] (M = Ti ( 24a), Zr ( 24b)), respectively. 23b and 24b reacted with the silane reagent HSiEt 3 to form, via hydrosilylation, [Zr{(Et 3SiCH 2CH 2) 3SiCH 2CH 2(Et)Si(η 5-C 5Me 4)(η 5-C 5H 4)}Cl 2] ( 25b) and [Zr{(Et 3SiCH 2CH 2)Me 2SiCH 2CH 2(Et)Si(η 5-C 5Me 4)(η 5-C 5H 4)}Cl 2] ( 26b), respectively. The previously synthesized compounds, [M{CH 2 CH(Me)Si(η 5-C 5Me 4) 2}Cl 2] (M = Ti ( 27a), Zr ( 27b)) and [Zr{CH 2 CHCH 2(Me)Si(η 5-C 5Me 4) 2}Cl 2] ( 28b), have also been tested in reactions of hydrosilylation with SiHMeCl 2 to give [M{Cl 2MeSiCH 2CH 2(Me)Si(η 5- C 5Me 4) 2}Cl 2] (M = Ti ( 29a), Zr ( 29b)) and [Zr{Cl 2MeSiCH 2CH 2CH 2(Me)Si(η 5-C 5Me 4) 2}Cl 2] ( 30b). All the zirconocene compounds are active to varying degrees as catalysts in the polymerization of ethylene. The molecular structures of 21b and 21c have been determined by single crystal X-ray diffraction studies.