Hydrosilylation

Hydrosilylation refers to the syn-selective anti-Markovnikov addition of a silane across a double bond. Was discovered by the reaction of Speier in the 1950s. Unlike, for example, the hydroboration reaction does not proceed without a catalyst.

Catalysts

Platinum catalysts are often used, in which the active species is always present as the platinum (0). As precatalyst Hexachloridoplatinsäure can serve in isopropanol ( Speier 's catalyst). If this catalyst system such as 1,1,3,3 - tetramethyl-1 ,3- implemented divinyldisiloxane with additives, then one speaks of the Karstedt catalyst. In mixtures of this type, both dinuclear platinum (0) - alkene and colloidal platinum was detected.

Mechanism

The mechanism of the hydrosilylation consists of oxidative addition of the silane to the Pt ( 0) species, olefin coordination with the substitution of a ligand, olefin insertion, and reductive elimination.

Asymmetric hydrosilylation

The hydrosilylation can be performed asymmetrically with palladium catalysts. This can be used, for example, the chiral ligand 2 -diphenylphosphino -2'- methoxy-1, 1'- binaphthyl ( " MeO -MOP " ) which can be synthesized from BINOL

Hydrosilylation of alkynes

In the hydrosilylation of alkynes I.A. no high regio - and stereoselectivity generated, but the vinyl silanes as accessible in subsequent reactions can be used such as the Hiyama coupling.