Dinuclear Dicyclopentadienyl Titanium Complexes with Bridging Cyclopentadienylsiloxo Ligands

Abstract

Addition of 1 equiv of TlCp to compound [(TiCl 2 ) 2 (μ-{(η 5 -C 5 Me 4 SiMeO) 2 (μ-O)})] (A) at 80 °C gave a mixture with different molar ratios of the two possible isomers of [(TiClCp)(TiCl 2 )(μ-{(η 5 -C 5 Me 4 SiMeO) 2 (μ-O)})] (1). Reaction of compound A with 2 equiv of TlCp at 80 °C afforded [(TiClCp) 2 (μ-{(η 5 -C 5 Me 4 SiMeO) 2 (μ-O)})] (2as) as the unique reaction product. Each Cp ligand of 2as is located in different positions anti and syn with respect to the Si-O-Si bridge. However, a mixture of two isomers of [(TiClCp) 2 (μ-{(η 5 -C 5 Me 4 SiMeO) 2 (μ-O)})], 2as (>95% by NMR) and 2aa (<5% by NMR), was obtained when the reaction was carried out at 60 °C; the two Cp ligands of 2aa were located at anti positions. Alkylation of isomer 2as with LiMe gave a mixture of the three possible isomers [(TiMeCp) 2 (μ-{(η 5 -C 5 Me 4 SiMeO) 2 (μ-O)})] (3as, 3aa, 3ss). The proportion of each was dependent on the reaction temperature. Isomer 2as reacted with Lewis acids E(C 6 F 5 ) 3 (E=B, Al) and with Li[B(C 6 F 5 ) 4 ] to give the chloro-bridged dititanium compounds [(TiCp) 5aC and 5sC; Q=B(C 6 F 5 ) 4 ), with the remaining methyl ligand located at anti or syn positions depending on the methyl group being abstracted. DFT studies were carried out to determine the stability of the isomers of 2 and 3, to determine which chlorine atom in compound 2as was more easily eliminated, and also to clarify the transformation of isomer 2as into the mixture of isomers 3as, 3aa, and 3ss during the alkylation reaction. Article

Synthetic Endeavors toward Titanium Based Frustrated Lewis Pairs with Controlled Electronic and Steric Properties

“…As it appeared that obtaining methyl-aryloxy complexes 3 ′ was going to be a challenging task, we wondered whether cationic aryloxy Ti complexes 4 could be obtained directly from 3 . Indeed B­(C 6 F 5 ) 3 and [Et 3 Si]­[B­(C 6 F 5 ] 4 have been used to abstract Cl from Ti complexes derived from titanocene, , and Wass recently showed that sequential reduction and oxidation of [Cp 2 TiClOAr] complexes afforded [Cp 2 TiOAr]­[B­(C 6 F 5 ) 4 ] species . When complexes 3a and 3c were mixed with B­(C 6 F 5 ) 3 in C 6 D 6 , the solutions immediately turned from red-orange to red-brown ( 3a , 3c ) or deep purple ( 3b ).…”

Taming the Cationic Beast: Novel Developments in the Synthesis and Application of Weakly Coordinating Anions

“…Since 2004, notable examples of this approach have been reported using the following Lewis acids B(C 6 F 5 ) 3 , [198,210] Al(C 6 F 5 ) 3 , [199,210] Al(OC(CF 3 ) 3 ) 3 , [144,145] Al(OC-(C 5 F 10 )C 6 F 5 ) 3 , [144] Ga(C 6 F 5 ) 3 , [155] and TMS-F-Al(OR F ) 3 (TMS = trimethylsilyl) [211] as well as the triarylboranes FcB-(o-tol) 2 ,F cB(o-Xyl) 2 ,F cBMes 2 , [212,213] PhBMes 2 , [214] or B(o-C 6 F 5 C 6 F 4 ) 3 [155] (where Fc = ferrocene; o-tol = 2-(CH 3 )C 6 H 5 ; oxyl = 2,6-(CH 3 ) 2 C 6 H 4 ;M es = 1,3,5-(CH 3 )C 6 H 4 ).…”