Boranes metal silyls

By no means do all metallocarboranes have the metal atoms occupying vertices of the basic polyhedra. Apart from many derivatives in which o-bonded metal residues occupy exo sites attached to particular skeletal atoms, several metalloboranes and -carboranes are known in which the metal occupies an edge-bridging site, effectively replacing a bridging hydrogen atom of the parent borane. Many are nido species related to BeHio, for example, the /x-silyl and /i-germyl carboranes. 

Tris(pentafluorophenyl)borane (35) is a powerful Lewis acid with a hard boron center. It interacts strongly with hard Lewis basic centers and abstracts hard anion such as methyl anion and hydride to initiate selective reactions that are otherwise difficult to achieve. The B(CgF5)3-promoted early transition-metal-catalyzed olefin polymerizations are typical reactions [16]. The B(C6F5)3-Ph3SiH system is useful for hydro-silylation of the carbonyl group, in which the boron of 35 activates the Si—H bond rather than the carbonyl group (see 40 in Scheme 3.39) and reduces even the ester carbonyl group effectively [17]. A number... 

Borane Silyl-alkali metal T (°C) Time (h) Product Yield (%) Ref. 

Chlorosilanes are also very reactive towards the a-metallated phosphine boranes leading to a-silylated phosphine boranes (Scheme 4.38). 

Reagents obtained by lithiation of ort/io-haloarylphosphines have been used in routes to new substituted arylphosphines, e.g., (69), (70), and (71). C-lithiated phosphinocyclopentadienides, e.g., (72), have been used in routes to dissymmetric heteroannular-functionalised ferrocenylpolyphosphines, e.g., (73). The reagent PhP(CH2CH2SLi)2 has been applied in a route to new phosphathiamacrocycles, e.g., (74). Apart from their applications in synthesis, interest has also continued in the preparation and structural characterisation of various C-metallated complexes of borane-protected alkyl- and silylated alkyl-phosphines, ° C-metallated potassium-and lanthanum-complexes of l,2-bis(diphenylphosphino)methane, and also of alkaline earth and rare earth N-metallated complexes of a variety of phosphino-amides. ... 

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