Reactivity of a Titanocene Pendant Si鈥揌 Group toward Alcohols. Unexpected Formation of Siloxanes from the Reaction of Hydrosilanes and Ph3COH Catalyzed by B(C6F5)

详细信息    查看全文

• 作者：Tom谩拧 Stra拧谩k ; Jan S媒kora ; Martin Lama膷 ; Ji艡铆 Kubi拧ta ; Michal Hor谩膷ek ; R贸bert Gyepes ; Ji艡铆 Pinkas
• 刊名：Organometallics
• 出版年：2013
• 出版时间：August 12, 2013
• 年：2013
• 卷：32
• 期：15
• 页码：4122-4129
• 全文大小：341K
• 年卷期：v.32,no.15(August 12, 2013)
• ISSN：1520-6041

文摘

The reaction of [Cp(畏<sup>5sup>-C<sub>5sub>H<sub>4sub>CH<sub>2sub>SiMe<sub>2sub>H)TiCl<sub>2sub>] (1; Cp = 畏<sup>5sup>-C<sub>5sub>H<sub>5sub>) and methanol in the presence of catalytic amounts of B(C<sub>6sub>F<sub>5sub>)<sub>3sub> afforded a complex with a pendant silyl ether group, [Cp(畏<sup>5sup>-C<sub>5sub>H<sub>4sub>CH<sub>2sub>SiMe<sub>2sub>OMe)TiCl<sub>2sub>] (2), in good yield. The analogous reaction of 1 and Ph<sub>3sub>COH resulted in the unexpected formation of [CpTiCl<sub>2sub>{渭-畏<sup>5sup>:畏<sup>5sup>-(C<sub>5sub>H<sub>4sub>)CH<sub>2sub>SiMe<sub>2sub>OSiMe<sub>2sub>CH<sub>2sub>(C<sub>5sub>H<sub>4sub>)}TiCl<sub>2sub>Cp] (4). The formation of siloxanes from the reaction of 2 equiv of hydrosilane with Ph<sub>3sub>COH mediated by B(C<sub>6sub>F<sub>5sub>)<sub>3sub> has a general applicability and proceeds in two consecutive steps: (i) transfer of the hydroxyl group from the trityl moiety to the silicon atom and (ii) silylation of the silanol formed in situ with the second equivalent of hydrosilane. The different hydrosilane reactivity toward Ph<sub>3sub>COH in comparison with other alcohols can be attributed to the easy generation of the borate salt [Ph<sub>3sub>C]<sup>+sup>[(C<sub>6sub>F<sub>5sub>)<sub>3sub>B(渭-OH)B(C<sub>6sub>F<sub>5sub>)<sub>3sub>]<sup>鈭?/sup> (5) under catalytic conditions. The intramolecular Si鈥揌 and Ti鈥揅l exchange in 1 is catalyzed by B(C<sub>6sub>F<sub>5sub>)<sub>3sub> in the presence of no alcohol. This process affords presumably a transient titanocene hydrido chloride, which is either chlorinated to give [Cp(畏<sup>5sup>-C<sub>5sub>H<sub>4sub>CH<sub>2sub>SiMe<sub>2sub>Cl)TiCl<sub>2sub>] (3) in CD<sub>2sub>Cl<sub>2sub> or decomposes into several paramagnetic Ti(III) species in toluene-d<sub>8sub>. Complex 3 was independently synthesized from 1 and Ph<sub>3sub>CCl in a good yield.