Chemical dynamics of the formation of the ethynylsilylidyne radical (SiCCH(X Π2)) in the crossed beam reaction of ground state silicon atoms (Si(P3)) with acetylene (C2H2(X ∑g+1))

The reaction dynamics of ground state silicon atoms (Si(P3)) with the acetylene molecule (C2H2(X ∑g+1)) were investigated at a collision energy of 101.6±1.6 kJ mol−1 under single collision conditions in a crossed molecular beam machine. We found that the reaction dynamics proceeded via an addition of the silicon atom to the π-electrons of the acetylene molecule at a single carbon atom forming a Cs symmetric SiC2H2(X A3″) intermediate. The latter either emitted a hydrogen atom leading to the linear SiCCH(X Π2) product or underwent a hydrogen migration to the SiCCH2(X A32) isomer prior to the decomposition of the latter to SiCCH(X Π2) plus atomic hydrogen. The overall reaction to form the SiCCH(X Π2) plus atomic hydrogen products was determined to be highly endoergic by 84±6 kJ mol−1. No evidence of a molecular hydrogen elimination channel was found at this collision energy. Our study predicts that this endoergic neutral-neutral reaction can lead to the formation of an organosilicon transient species, i.e.,...