Olefin insertions metal-boron bonds

Insertions of Olefins and Acetylenes into Metal-Silicon and Metal-Boron Bonds... 

The insertions of olefins into metal-silyl complexes is an important step in the hydrosi-lylation of olefins, and the insertions of olefins and alkynes into metal-boron bonds is likely to be part of the mechanism of the diborations and sUaborations of substrates containing C-C multiple bonds. Other reactions, such as the dehydrogenative sUylation of olefins can also involve this step. Several studies imply that the rhodium-catalyzed hydrosilylations of olefins occur by insertion of olefins into rhodium-silicon bonds, while side products from palladium- and platinum-catalyzed hydrosilylations are thought to form by insertion of olefins into the metal-sihcon bonds. In particular, vinylsilanes are thought to form by a sequence involving olefin insertion into the metal-silicon bond, followed by p-hydrogen elimination (Chapter 10) to form the metal-hydride and vinylsilane products. 

As noted in the introduction to this section, the insertions of alkynes and alkenes into metal-boron bonds appear to be involved in catalytic additions of borane reagents to alkenes and alkynes. One direct observation of the insertion of an alkyne into a metal-boron bond has been reported, and this reaction is shown in Equation 9.91. In another case, the reaction of an olefin with a metal-boryl complex generated products consistent with the... 

---