The novel complex cis-[(ITMe)2Pd(SiMe3)2 (ITMe=1,3,4,5-tetramethylimidazol-2-ylidene) has been synthesized by mild oxidative cleavage of Me3SiSiMe3 using [(ITMe)2Pd0]. The use of this complex as precatalyst for the cis-bis(silyl)ation of alkynes using unactivated disilanes is reported.

Abstract:The novel complex cis-[(ITMe) 2 Pd(SiMe 3 ) 2 (ITMe = 1,3,4,5-tetramethylimidazol-2-ylidene) has been synthesized by mild oxidative cleavage of Me 3 SiSiMe 3 using [(ITMe) 2 Pd 0 ]. The use of this complex as precatalyst for the cis-bis(silyl)ation of alkynes using unactivated disilanes is reported.The transition metal catalyzed activation of disilanes for the synthesis of high-value organosilicon compounds has received a significant amount of attention from industry and academia. Applications encompass the formation of silanes, [1] bis-(silyl)ation of unsaturated compounds, [2] aryl/acyl silane synthesis, [3,4] and protection of alcohols. [5] Since the oxidative cleavage of the SiÀSi bond by a low-valent platinum-group transition-metal center is proposed as a vital step for some of these processes, [6] the isolation of the resulting bis(silyl) transition-metal complexes is of great interest for elucidating reaction mechanisms. Unfortunately, the synthesis of such complexes has been largely limited to the oxidative addition of strained or activated disilanes. [7] The cleavage of non-activated hexamethyldisilane is particularly challenging. Examples of the resulting bis(trimethylsilyl) platinum-group metal complexes are rare: only two have been described in the literature, and they bear either phosphine or isocyanide ligands. Braun and co-workers reported that [Pt(PEt 3 ) 3 ] reacted with a large excess of hexamethyldisilane to yield cis-[Pt(PEt 3 ) 2 (SiMe 3 ) 2 ] at ambient temperature, but it only went to 50 % completion after three weeks.[8] Earlier, Ito and co-workers synthesized cis-[Pt(CNAd) 2 (SiMe 3 ) 2 ] (CNAd = 1-adamantyl isocyanide) from [Pt 3 (CNAd) 6 ] using 30 equivalents of hexamethyldisilane at 80 8C. [9] It is well documented that N-heterocyclic carbenes (NHCs) have equivalent or better s-donor character than the most common phosphines and that NHC/M complexes (M = metal) are less prone to decomposition by cleavage of the (NHC)-M bond. [10,11] As part of our ongoing studies of NHC/palladium-catalyzed reactions, we decided to explore their potential to activate hexamethyldisilane since there are no examples in the literature of palladium complexes capable of this reaction. Herein we report on the synthesis of the novel complex cis-[Pd(ITMe) 2 (SiMe 3 ) 2 ] from [(ITMe) 2 Pd 0 ] and its inclusion in a catalytic cycle leading to the cis-bis(silyl)ation of alkynes.While very recent literature on NHC/Pd complexes features the use of large NHCs as a common denominator, [12] we decided to start our studies with one of the smallest NHCs available, that is, 1,3,4,5-tetramethylimidazol-2-ylidene (ITMe; 1), which exhibits a very small percent buried volume and a high s-donor character.[13] The conventional synthetic route to 1 was established by Kuhn and co-workers. [14] It involves the formation of the corresponding thione by a ring-forming double condensation of N,N'-dimethylthiourea and acetoin, and subsequent reductive desulfurization of the thione using potassium metal, with an overall yield ...

The novel complex cis‐[(ITMe)2Pd(SiMe3)2 (ITMe=1,3,4,5‐tetramethylimidazol‐2‐ylidene) has been synthesized by mild oxidative cleavage of Me3SiSiMe3 using [(ITMe)2Pd0]. The use of this complex as precatalyst for the cis‐bis(silyl)ation of alkynes using unactivated disilanes is reported.

cis‐Disilylations In their Communication on O. Navarro, J. Spencer et al. present the oxidative cleavage of Me3SiSiMe3. This reaction generates a precatalyst for the cis‐disilylation of internal alkynes with nonactivated disilanes.

cis‐Disilylierungen. In der Zuschrift auf präsentieren O. Navarro, J. Spencer et al. die oxidative Spaltung von Me3SiSiMe3, die einen Präkatalysator für die cis‐Disilylierung interner Alkine mit nichtaktivierten Disilanen liefert.