Silyl complexes synthesis

Basically the same methods known from the synthesis of classical metal-silyl complexes can also be applied to the preparation of low valent Si compounds. The procedures given here are summarized with the focus on silylene complexes These are a) reactions of appropriate metal anions with halosilanes, which are the most important methods for the formation of M-Si bonds. Alternatively, silyl... 

This synthetic approach is known from the synthesis of L M(alkene)H compounds from LnM(CO)alkane precursors and can easily be applied to the analogous silyl complexes. The Si—H bond even shows an increased activity for oxidative addition reactions [42, 43]. 

A zirconium-silene complex was obtained during the course of our study on the synthesis of a zirconium-silyl complex. The zirconium-silene complex is formed from disilylzirconocene 2a, generated from Cp2ZrCl2 and 2 equivalents of Me2PhSiLi 8b. Zirconium-silene complex 3 should be in a state of equilibrium with zirconacyclopropane 3. The insertion of diaryl alkyne 14 or vinyl alkyne... 

Synthesis and Reaction Chemistry of a,p-Unsaturated Acyl Complexes Derived from (2). Two methods for the preparation of optically active ( )- and (Z)-a,p-unsaturated iron acyls from (2) have been reported." One method involves aldol condensation of (2) with aldehydes followed by 0-methylation to produce diastereomeric acyls (18). This mixture (18) is then treated with Sodium Hydride to produce predominantly ( )-a,p-unsaturated acyl complexes (19) (eq 13). Alternatively, (2) can be depro-tonated and treated with Chlorotrimethylsilane to produce the C-silylated complex which is subsequently deprotonated and treated with an aldehyde. This Peterson alkenation produced mixtures... 

In 1998, Mitchell and Tilley described the synthesis of a new rhodium silyl complex <19980M2912>. Reaction of (Me3P)3RhCl with (THF)2LiSiHMes2 (Mes = 2,4,6-trimethylphenyl) in toluene resulted in formation of a light yellow solution, from which colorless crystals of compound 5 were isolated after work-up. The presence of both Rh-H (5 =—9.90) and Si-H (5 = 5.76) resonances in the NMR spectrum and five separate methyl signals suggested the structure 5 shown in Equation (31). 

Eq.3. Synthesis of hafnium and zirconium trichlorotris(tiimethylsilyl)silyl complexes (3,4). 

Hydrido-disilanyl complexes L M(H)(SiR2-SiR2H) are interesting because H2 elimination could support a possible 3-Si-H elimination and result in disilene complexes or products derived thereof Analogous to the synthesis of the well-known hydrido-silyl complexes... 

A related area of this chemistry is the selective reactivity of Si-Si bonds [78]. The use of disilanes in organic synthesis for the creation of new (and reactive) Si-C bonds is an area of current interest and application [79-81]. This work has stemmed from earlier studies which have demonstrated that disilanes readily oxidatively add to a variety of metal centres [82] to produce transition metal silyl complexes [83]. The investigation of this area will be detailed by Prof. M. Sugi-mone and Prof. Y. Ito (Activation of Si-Si Bonds Stoichiometric and Catalytic Reactions). 

The synthesis of an enantiomerically enriched chromium complex via asymmetric lithiation of a prochiral tricarbonyl(ri -arene)chromium complex using a chiral lithium amide base was first demonstrated in 1994 by Simpkins [88]. Arene complex 44 was treated with C2-symmetric chiral base ent-39 in the presence of TMSCl as an internal quench and silylated complex 45 was obtained in 84% ee (Scheme 24). 

Transition-metal-silyl complexes are also formed by the reactions of metal-alkyl complexes with silanes to form free alkane and a metal-silyl complex. Two examples are shown in Equations 4.114 and 4.115. ° The synthesis of silyl complexes by this method has been accomplished with both early and late transition metal complexes. The formation of metal-silyl complexes from late-metal-alkyl complexes resembles the hydrogenolysis of metal-alkyl complexes to form metal hydrides and an alkane. The mechanisms of these reactions are discussed in Chapter 6. In brief, these reactions with late transition metal complexes to form silyl complexes typically occur by a sequence of oxidative addition of the silane, followed by reductive elimination of alkane. An example of this is shown in the coupling of 1,2-bis-dimethylsilyl benzene with a dimethyl platinum(II) complex (Equation 4.114). Similar reactions occur with d° early metal complexes by a a-bond metathesis process that avoids these redox events. For example, the reaction of Cp ScPh with MesSiH, has been shown to proceed through this pathway (Equation 4.115). ... 

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