Reaction of titanocene allyls

Highly Active Titanocene Catalysts for Epoxide Hydrosilylation: Synthesis, Theory, Kinetics, EPR Spectroscopy

“…[Cp 2 TiR] complexes are attractive in this context because of the weak Ti À Cbond. [5] We studied s-bond metathesis of these complexes with PhSiH 3 and (EtO) 3 SiH computationally ( Figure 1). [6] DG 298 values for the s-bond metathesis indicate that [Cp 2 TiH] formation is favorable for R = Me,t hermoneutral for R = Allyl, and endergonic for R = Ph with PhSiH 3 .…”

“…(EtO) 3 SiH was predicted to be inferior.I np ractice, [Cp 2 TiAllyl] is especially attractive since it can be prepared in situ by stirring Cp 2 TiCl 2 (1 equiv) and AllylMgBr (2.2 equiv) in THF (1-10 min, purple reaction mixture). [5] After the addition of PhSiH 3 (1.5 equiv with respect to the epoxide), the generation of [Cp 2 TiH] (the "allyl activation") is complete in 1-10 min (green reaction mixture).…”

“…Initial experiments were designed to examine the stability of the catalyst under synthetically relevant conditions. [9,10] The conversion of 4 into 5 in the presence of 10 mol %catalyst was monitored by following [5]a nd subsequently plotting [4]a s af unction of time ( Figure 3). Ah igher catalyst loading was employed to ensure reproducible detection of the titanocene species and to obtain fast turnover.…”

Hochaktive Titanocen‐Katalysatoren für Epoxid‐Hydrosilylierungen – Synthese, Theorie, Kinetik, EPR‐Spektroskopie

“…[Cp 2 TiR]-Verbindungen sind hierfür wegen der schwachen Ti-C-Bindung besonders attraktiv. [5] Abbildung 1z eigt be-rechnete Freie Enthalpien für die s-Bindungsmetathese mit PhSiH 3 und (EtO) 3 SiH. [6] Die DG 298 -Werte der Metathese zeigen, dass die Bildung von [Cp 2 TiH] mit PhSiH 3 für R = Me exergonisch, thermoneutral für R = Allyl und endergonisch für R = Ph ist.…”

“…) in THF (1-10 min, violette Lçsung) gebildet werden kann. [5] Nach Zugabe von PhSiH 3 (1.5 ¾quiv.b zgl. Epoxid) entsteht [Cp 2 TiH] ("Allylaktivierung") in 1-10 min (grüne Lçsung).…”