Amido silylated

Two further higher-order potassium magnesiates have been reported, both containing a bulky bis(amido)silyl ligand [ (THF)2K Mg(N... 

Cross-coupling to form carbon heteroatom bonds occurs by oxidative addition of an organic halide, generation of an aryl- or vinylpalladium amido, alkoxo, tholato, phosphido, silyl, stannyl, germyl, or boryl complex, and reductive elimination (Scheme 2). The relative rates and thermodynamics of the individual steps and the precise structure of the intermediates depend on the substrate and catalyst. A full discussion of the mechanism for each type of substrate and each catalyst is beyond the scope of this review. However, a series of reviews and primary literature has begun to provide information on the overall catalytic process.18,19,22,23,77,186... 

Coverage is 3.0 timol on 200 m g silica (12% C). The phase is endcapped with a small silylating reagent in the conventional way. Ascentis RP-amide columns are the latest version of the Supelco amido column bonded on higher surface area 450 m g pure silica (25% C). A polymeric bonding is used to increase the stability and reduce bleed, especially for MS work. 

Scheme 12.4 pfQ criterion (measure of surface reactivity) and the thermal pretreatment of the support (here silica) govern the surface reactivity L= monovalent alkoxo, (silyl)amido or alkyl ligand. 

The dependence of the E-E bond lengths on the nature of the substituents has been explained merely by steric effects. However, it seems more likely that a balanced interaction of steric effects, charge separation, electrostatic repulsion, rehybridization etc., causes the observed variation. In contrast to the amido compounds discussed above, a specific correlation between the E-E bond lengths and the bond angles (C-E-C or Si-E-Si) does not exist. The different influence of alkyl and silyl substituents was investigated by quantum-chemical calculations.91... 

Some of the novel systems are known only with silyl, germyl or other inorganometallic substituents, but not with simple organyl substituents. Since no principal differences from the related organyl derivatives are expected, these compounds are also included in the present discussions. Excluded are compounds in which the tetrel exclusively bears halido, amido and alkoxo substituents or other hetero-element atoms with lone-pairs. 

Both amido and pinacol derivatives of B-Si compounds 125 and 126 added to terminal and internal alkynes in the presence of a palladium244-246 or platinum(O) catalyst247 by a mechanism involving an oxidative addition-insertion process (Equation (39)).248 On the other hand, phosphine-free nickel(O) catalyst resulted in the dimerization of alkynes giving a Z,Z-isomer of l-silyl-4-borylbutadiene derivatives.249 Since the palladium-catalyzed cross-coupling at the C-B bond is faster than the G-Si bond of 137, a silylboration-cross-coupling sequence provided a method for the synthesis of 1-alkenylsilanes.246... 

Reactions of [Ti( -C5Me4SiMeXCl)Cl3] with two equiv. of LiNH-r-Bu afforded the ania-silyl-jj-amido compounds (j7 j7 -C5Me4SiMeX-N-r-Bu)TiCl2 (X = H,C1). Methylation of (j7 j7 -C5Me4SiMeX-N-r-Bu)TiCl2 with MgClMe gives... 

Alkyl, aryl, silyl and amido substituents are all amenable to the in situ reduction protocol and similar RM compounds may also be made from univalent hahdes. The structures of the compounds produced in such reactions are dependent on the nature of the substituent for most substituents, oligomeric polyhedral clusters are obtained. The use of sterically... 

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