Low-valent ansa-dimethylsilylene-, dimethylmethylene-bis(cyclopentadienyl) titanium compounds and ansa-titanium–magnesium complexes

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61388955%3A_____%2F19%3A00503734" target="_blank" >RIV/61388955:_____/19:00503734 - isvavai.cz</a>

Nalezeny alternativní kódy

RIV/00216208:11310/19:10394012

Výsledek na webu

<a href="http://hdl.handle.net/11104/0295525" target="_blank" >http://hdl.handle.net/11104/0295525</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.jorganchem.2019.03.003" target="_blank" >10.1016/j.jorganchem.2019.03.003</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Low-valent ansa-dimethylsilylene-, dimethylmethylene-bis(cyclopentadienyl) titanium compounds and ansa-titanium–magnesium complexes

Popis výsledku v původním jazyce

Reduction of ansa-titanocene dichlorides [X(eta(5)-C5H4)(2)TiCl2] (X = SiMe2 (1) and CMe2 (2)) in tetrahydrofuran (THF) by preactivated magnesium in the presence of bis(trimethylsilyl) acetylene (BTMSA) yielded complexes [X(eta(5)-C5H4)(2)Ti(eta(2)-BTMSA)] (X = SiMe2 (3) and CMe2 (4)). The prolonged action of excess magnesium and BTMSA resulted in the formation of ansa-titanium-magnesium complexes [m-X {(eta(5)-C5H4) Ti(eta(2)-SiMe3C CSiMe3)(2)}{(eta(5)-C5H4)Mg(THF)}] (X = SiMe2 (5) and CMe2 (6)), which had their metals bounded via the ansa-ligand and ionic bonding between magnesium and the BTMSA ligands. Compounds 5 and 6 easily isomerized to 5a and 6a through rotation of their {(C5H4) Mg(THF)} moiety around the ansa- X-C bond. This rotation canceled the interaction of magnesium with the BTMSA ligands, which resulted in a large high-field shift of acetylenic carbon resonances. The geometry of both structures optimized by Density Functional Theory (DFT) computations together with the good correlation of computed magnetic shieldings and experimental C-13 NMR shifts of 5 and its isomer 5a approved the above isomerization. The simultaneous ionic bonding of Mg2+ to the cyclopentadienyl ligand, which is eta(5)-coordinated to the {Ti(eta(2)-BTMSA)(2)} moiety in 5a got also confirmed by computational results. Reduction by magnesium was used to obtain Ti(III) dimers of ansa-titanocene acetylides [{X(eta(5)-C5H4)(2)Ti (mu-eta(1): eta(2)-C CSiMe3)}(2)] (X = SiMe2 (7) and X = CMe2 (8)) via redox splitting of 1,4-bis(trimethylsilyl) buta-1,3-diyne (BSD) by transient Ti(II) titanocene. The thermally stable Ti(II) compounds 3 and 4 were also shown to react with BSD yielding respectively 7 and 8. The reduction of 1 and 2 with magnesium in THF afforded Ti(III) monochloride dimers [{ansa-X(eta(5)-C5H4)(2)Ti(mu-Cl)}(2)] (X = SiMe2 (10), CMe2 (11)), which in contrast to the non-ansa dimer [(eta(5)-C5H5)(2)Ti(mu-Cl)}(2)] were silent in toluene glass EPR spectra. No evidence of obtaining quadruply bridged dititanium complexes capped with the ansa-ligands was encountered among crystal structures of 7-11, even though the total energy of optimized molecules 7 and 10 and their capped congeners differed by more than 45 kJ/mol, favouring the capped isomers in both cases.

Název v anglickém jazyce

Low-valent ansa-dimethylsilylene-, dimethylmethylene-bis(cyclopentadienyl) titanium compounds and ansa-titanium–magnesium complexes

Popis výsledku anglicky

Reduction of ansa-titanocene dichlorides [X(eta(5)-C5H4)(2)TiCl2] (X = SiMe2 (1) and CMe2 (2)) in tetrahydrofuran (THF) by preactivated magnesium in the presence of bis(trimethylsilyl) acetylene (BTMSA) yielded complexes [X(eta(5)-C5H4)(2)Ti(eta(2)-BTMSA)] (X = SiMe2 (3) and CMe2 (4)). The prolonged action of excess magnesium and BTMSA resulted in the formation of ansa-titanium-magnesium complexes [m-X {(eta(5)-C5H4) Ti(eta(2)-SiMe3C CSiMe3)(2)}{(eta(5)-C5H4)Mg(THF)}] (X = SiMe2 (5) and CMe2 (6)), which had their metals bounded via the ansa-ligand and ionic bonding between magnesium and the BTMSA ligands. Compounds 5 and 6 easily isomerized to 5a and 6a through rotation of their {(C5H4) Mg(THF)} moiety around the ansa- X-C bond. This rotation canceled the interaction of magnesium with the BTMSA ligands, which resulted in a large high-field shift of acetylenic carbon resonances. The geometry of both structures optimized by Density Functional Theory (DFT) computations together with the good correlation of computed magnetic shieldings and experimental C-13 NMR shifts of 5 and its isomer 5a approved the above isomerization. The simultaneous ionic bonding of Mg2+ to the cyclopentadienyl ligand, which is eta(5)-coordinated to the {Ti(eta(2)-BTMSA)(2)} moiety in 5a got also confirmed by computational results. Reduction by magnesium was used to obtain Ti(III) dimers of ansa-titanocene acetylides [{X(eta(5)-C5H4)(2)Ti (mu-eta(1): eta(2)-C CSiMe3)}(2)] (X = SiMe2 (7) and X = CMe2 (8)) via redox splitting of 1,4-bis(trimethylsilyl) buta-1,3-diyne (BSD) by transient Ti(II) titanocene. The thermally stable Ti(II) compounds 3 and 4 were also shown to react with BSD yielding respectively 7 and 8. The reduction of 1 and 2 with magnesium in THF afforded Ti(III) monochloride dimers [{ansa-X(eta(5)-C5H4)(2)Ti(mu-Cl)}(2)] (X = SiMe2 (10), CMe2 (11)), which in contrast to the non-ansa dimer [(eta(5)-C5H5)(2)Ti(mu-Cl)}(2)] were silent in toluene glass EPR spectra. No evidence of obtaining quadruply bridged dititanium complexes capped with the ansa-ligands was encountered among crystal structures of 7-11, even though the total energy of optimized molecules 7 and 10 and their capped congeners differed by more than 45 kJ/mol, favouring the capped isomers in both cases.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10403 - Physical chemistry

Projekt

<a href="/cs/project/GA17-13778S" target="_blank" >GA17-13778S: Hliník neobsahující katalytický systém využívající hydrosilan-B(C6F5)3 adukty jako aktivátory přechodných kovů při polymeraci ethylenu</a><br>

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2019

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Journal of Organometallic Chemistry

ISSN

0022-328X

e-ISSN

—

Svazek periodika

889

Číslo periodika v rámci svazku

JUL 2019

Stát vydavatele periodika

CH - Švýcarská konfederace

Počet stran výsledku

12

Strana od-do

15-26

Kód UT WoS článku

000464547800003

EID výsledku v databázi Scopus

2-s2.0-85063368918