Effect of additives on the reaction of monomeric silicon difluoride with 1,3-butadiene

Abstract

Recoil 31Si atom reactions with PF3 resulted in the formation of both singlet and triplet 31SiF2 in the ratio of 1.0:3.3. Singlet 3'SiFz reacted with 1,3-butadiene to give difl~orosilacyclopent-3-ene-~~Si, but triplet 31SiFz only gave this product in the presence of paramagnetic molecules such as NO, NO2, or 0 2 .The nuclear recoil technique1-* and the thermal vaporization method9-lS account for all the silicon atom reactions studied to date. Both processes have also been proven to be very effective in generating silicon analogues of carbenes. Using the nuclear recoil method of formation, silylene, SiH2, has been shown to undergo Si-H2-6 and possibly Si-Si bond i n s e r t i~n .~ Both singlet and triplet SiHz also add to 1,3-butadiene, giving s i I a~y c I o p e n t -3 -e n e .~~~ On the other hand, silicon difluoride, the best characterized carbene analogue, has been extensively studied by Margrave and co-workers employing the thermal vaporization method through the following formation I Si + SiF, -2SiFi(1) Spectroscopic evidence indicates that SiF2 possesses a singlet ground electronic stateI2 with a bond angle of 100' 59'.13 It is extraordinarily stable having a half-life a t 0.1 Torr of 150 s. Even in the presence of 1 Torr of oxygen, its half-life is still 6 s.I4 However, in the majority of cocondensation studies where the SiFz thus formed is allowed to react with other substrates, the products always contained a dimeric unit of SiF2, indicating that dimerization predominates whenever SiF2 is in high concent ration.ZSiF, -(SiFJ2Accordingly, in the study of SiF2 reactions with 1,3-butadiene, Thompson and Margravels have found that the major product formed was 1, I ,2,2-tetrafluorodisilacyclohex-4-ene.Using the nuclear recoil method by employing the transmutation, 3'P(n,p))'Si, we have found that energetic 3iSi abstracts fluorine atoms from PF3 yielding 31SiF2. Due to its extremely low concentration, the 31SiF2 thus formed reacts with 1,3-butadiene in its monomeric form to give difluorosila~yclopent-3-ene-~~Si (DFSCP*).' (4)In the present work, we have studied the effect of seven inorganic and organic additives on the yield of DFSCP* from eq 4. From these studies, the possible existence of the previously unknown triplet 31SiF2 has been deduced.lb Such experiments also reveal certain interesting chemical properties of both singlet and triplet silicon difluoride. Experimental SectionGeneral Procedure. The general procedure used in this study was the same as that used in other typical nuclear recoil experiments.I6 Phosphorus trifluoride and 1,3-butadiene along with other desired additives were sealed in Pyrex bulbs using high vacuum techniques. Sample analysis was performed using standard radio-gas chromatography.I6Silicon-31 from the 3'P(n,p)31Si nuclear transmutation3 was formed using fast neutrons from twodifferent sources. ( 1 ) A 16-or 20-MeV deuteron beam from the Texas A&M University cyclotron was focused on a beryllium target initiating the nuclear transformation, gBe(d,n)loB. (2) Fast neutrons from a Tri...

The Reaction of Recoil 35S Atoms with Organic Compounds

“…Further, in a neon-moderated system the yield of hydrogen-t is gradually decreased by the addition of sulfur dioxide but sharply decreased with oxygen [6]. ZECK and his coworkers [7] have also observed a difference in scavenging power between nitrogen monoxide and oxygen in the reaction of 31 Si atoms with 1,3-buta-diene to form difluorosilacyclopent-3-ene-31 Si (DFSCP). The yield of DFSCP decreases sharply with oxygen but increases with nitrogen monoxide at the same low concentration range.…”

Reactions of monomeric silicon difluoride and silylene with conjugated pentadienes

“…This observation is again similar to that which has been observed in the butadiene system. 27 It can be explained by the supposition that the 31SiF2-02 complex being formed by triplet 31SiF2 undergoes further reaction very favorably with 02 molecules to give unobservable products. As a result, as the concentration of 02 increases in the system, it competes with the conjugated dienes for the 31SiF2-02 complex, and finally when the concentration of 02 is high enough, it eliminates essentially all of the complexes from reaction with the conjugated dienes.…”

“…An alternate mechanism involving collisional quenching has been considered in our earlier work. 27 It is possible that parmagnetic molecules would effect a spin-conversion process changing triplet 31SiF2 into its singlet form which then could add to the dienes to give the observed products. However, it is very difficult for this mechanism to account for the detailed variations in the 02 systems.…”

“…The general procedure used in this study was essentially identical with those described in our earlier publications. 25,27 Phosphorus trifluoride (or phosphine) and the conjugated dienes along with other desired additives were sealed in Pyrex bulbs using high-vacuum techniques. Sample analyses were performed using standard radio-gas chromatography.…”

Rediscovery of the gas-phase chemistry of difluorosilylene generated by thermal reduction

“…P. C.; Needham, T. E.; Matwiyoff, N. A. Biochemistry 1974, 13, 2650-2655. (4) [5',5'-2H2]Adenosylcobalamin was synthesized by exchanging the C-5' protons of adenosylcobalamln in D20 In the presence of ribonucleotide reductase (5) Parry, R. J. J. Chem. Soc.…”