Hydrosilylation and Hydrogermylation

The reaction of norbornene with A -methylallylnickel bromide or iodide gives linear polymers of the alkene via cw-insertion. Evidence for the stereochemistry of insertion is provided by the reaction of norbornene with h -methylallylnickel chloride, which gives the alkene complex (6). Various types of reaction of (6) then result in cis-insertion of the norbornene into the nickel-allyl bond. Thus treatment of (6) with sodium acetate gives (7), which is shown by A -ray studies to be formed by an ejcu-c/s-insertion of the alkene. A similar cw-insertion occurs with the corresponding palladium complex.  

Insertion of an alkyne into a metal-hydrogen or metal-carbon bond is usually thought to occur via prior co-ordination of the alkyne into a vacant co-ordination site on the metal. Thus the reaction of hexafluorobut-2-yne with complexes of the type / -[PtClMeLa] (L = tertiary phosphine or arsine) can lead to insertion products, e.g. (8), and complexes which may be intermediates in the insertion, e.g. (9), can be isolated and characterized. Similarly, the reaction of dicyanoacetylene with [IrH(CO)2(PPh3)2] gives (10), which is 

Chloroform solutions of (11) on addition of a radical Initiator, e.g. PhC0020CPh, or on u.v. irradiation in the absence of the acetylene undergo a free-radical reaction to form [PtClaMegLJ (14) and [PtClgLa]. In the presence of the acetylene the formation of (14) follows the rate law 

It is suggested that the radical PtMeL2 plays a key role in the insertion reaction and reacts with (12) according to the equation 

PtMeLa -I- [PtClMeLa(acetylene)] — PtMeL2(acetylene) + [PtClMeLa] 

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There has also been a recent report of hydrosilylation and hydrogermylation of phenylacetylene catalyzed by the rhodium complexes [(rj -C5Me5)RhCl2]2 74 and (r] -C5Me5)Rh(BINAP)SbF6 75. The former catalyst promotes the unusual cfs-addition whereas the latter promotes trans-Siddition [37]. 

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