Apparent H Abstraction

Caspar and coworkers have studied the reactions of recoil Si atoms in a PH3-SiH4 mixture where the PH3 is required to function as a phosphorus atom source for the nuclear transmutation. They observed SiH3SiH3 as a 

Si-H bonds may give rise to excited adducts which subsequently decompose to give SiH. The same insertion-decomposition cycle may be repeated to yield SiHj, which eventually inserts into the Si-H bond of SiH4 to give SiHjSiHj as the final product. At present, there is no evidence favoring one of these two mechanisms over the other. If the direct H-abstraction process does prevail, there is also no guarantee that the H abstraction is a consecutive instead of a simultaneous process. 

---