Mixed Bent Sandwich Titanium Complexes with the [2‐(Diisopropylamino)ethyl]cyclopentadienyl Ligand — Catalysts for the Polymerization of Ethylene and the Dehydrocoupling of Phenylsilane

Abstract

Dehydrocupling of phenylsilane

Synthesis, Structures, and Catalytic Reactions of Ring-Substituted Titanium(IV) Complexes

“…Mixed-ring titanocene dichloride complexes (η 5 -C 5 H 4 CH 2 CH 2 NMe 2 )(η 5 -C 5 H 5 )TiCl 2 (10), 56 (η 5 -C 5 Me 4 -CH 2 CH 2 NMe 2 )(η 5 -C 5 H 5 )TiCl 2 (11), 58 (η 5 -C 5 Me 4 CH 2 -CH 2 NMe 2 )(η 5 -C 5 Me 5 )TiCl 2 (12), 58 and (η 5 -C 5 H 4 CH 2 -CH 2 N i Pr 2 )(η 5 -C 5 H 4 SiMe 3 )TiCl 2 (13) 59 have been syn- Rausch et al 60 reported a different route to the synthesis of (η 5 -C 5 H 4 CH 2 CH 2 NMe 2 )(η 5 -C 5 H 5 )TiCl 2 (10) via metathesis of the corresponding [CpCH 2 CH 2 N-(Me) 2 ]TiCl 3 (14) (see Table 16) with CpTl in boiling toluene to yield a garnet red microcystalline solid after recrystallization from CH 2 Cl 2 (Scheme 8). The compound was exceedingly moisture sensitive, a stark contrast to the stability of Cp 2 TiCl 2 .…”

Efficient Recycling of a Versatile Titanocene Precatalyst: Significance of Side-Chain Functionalization

“…We recently introduced the [2-(diisopropylamino)ethyl]cyclopentadienyl ligand (Cp N ⋮ C 5 H 4 CH 2 CH 2 N i Pr 2 ) into the chemistry of titanium by synthesizing bent sandwich complexes of the type Cp N 2 TiR 2 and Cp N 2 TiCl 2 ·2HCl as well as mixed bent sandwich complexes of the type Cp N Cp S TiR 2 and Cp N Cp S TiCl 2 ·HCl (Cp S = C 5 H 4 SiMe 3 ). Some of the chemical and physical properties of these complexes are surprising, especially in comparison with those of the nonfunctionalized compounds:…”

“…(I) The titanocene dichloride Cp N Cp S TiCl 2 (1) reacts with 1 equiv of methanolic hydrogen chloride resulting in protonation of the amino group to give the hydrochloride Cp N Cp S TiCl 2 ·HCl (2) in high yields . In contrast to 1 , which is extremely moisture-sensitive, 2 shows an excellent solubility and stability in polar protic solvents such as methanol or water and hydrolysis of the M−Cl bonds was not observed, even after exposure for several hours.…”

“…Both compounds, in combination with the cocatalyst MAO, catalyze the polymerization of ethylene, and therefore the easy handling of the hydrochloride 2 is particulary interesting. (II) The dimethyl derivative Cp N Cp S TiMe 2 (3) , which catalyzes the dehydrogenative coupling of phenylsilane furnishing oligosilanes in excellent yields, is obtained in nearly quantitative yield by the reaction of 2 with 3 equiv of methyllithium in diethyl ether and exhibits remarkable thermal stability . In contrast to the temperature- and light-sensitive complex Cp 2 TiMe 2 , for which an autocatalytic, “catastrophic” decomposition is reported, 3 is stable for several days under inert gas atmosphere at room temperature, presumably due to a weak intramolecular coordination of the N i Pr 2 group to the titanium center, thus prohibiting an α-elimination decomposition.…”

“…By the addition of methanolic HCl, the hydrochloride 2 can be recycled in a fashion similar to that described above (Scheme ); it is separated from the Florisil material by extraction with dichloromethane. In a second step complex 2 can be converted into the oligomerization catalyst 3 in nearly quantitative yield by the reaction with 3 equiv of methyllithium . In all procedures so far published in the literature, the catalytic species or its decomposition products remain absorbed on the Florisil material.…”