17680-01-2Relevant academic research and scientific papers
Heterobimetallic Rebound: A Mechanism for Diene-to-Alkyne Isomerization with M - -Zr Hydride Complexes (M = Al, Zn, and Mg)
Butler,White,Crimmin
, p. 949 - 956 (2018)
The reaction of a series of M·Zr heterobimetallic hydride complexes with dienes and alkynes has been investigated (M = Al, Zn, and Mg). Reaction of M·Zr with 1,5-cyclooctadiene led to diene isomerization to 1,3-cyclooctadiene, but for M = Zn also result in an on-metal diene-to-alkyne isomerization. The resulting cyclooctyne fragment is trapped between Zr and Zn metals in a heterobimetallic species that does not form for M = Mg or Al. The scope of diene isomerization and alkyne trapping has been explored leading to the isolation of three new heterobimetallic slipped metallocyclopropene complexes. The mechanism of diene-to-alkyne isomerization was investigated through kinetics. While the reaction is first-order in Zn·Zr at high diene concentration and proceeds with ΔH? = +33.6 ± 0.7 kcal mol-1, ΔS? = +23.2 ± 1.7 cal mol-1 K-1, and ΔG?298 K = +26.7 ± 1.2 kcal mol-1, the rate is dependent on the nature of the diene. The positive activation entropy is suggestive of involvement of a dissociative step. On the basis of DFT calculations, a heterobimetallic rebound mechanism for diene-to-alkyne isomerization has been proposed. This mechanism explains the origin of heterobimetallic control over selectivity: Mg - -Zr complexes are too strongly bound to generate reactive fragments, while Al - -Zr complexes are too weakly bound to compensate for the contrathermodynamic isomerization process. Zn - -Zr complexes have favorable energetics for both dissociation and trapping steps.
SYNTHESIS AND THERMAL REACTIONS OF 3-TRIMETHYLSILYL-1-PYRAZOLINE
Conlin, Robert T.,Kwak, Young-Woo
, p. 177 - 184 (2007/10/02)
The compound 3-trimethylsilyl-1-pyrazoline has been synthesized by addition of diazomethane to vinyltrimethylsilane at room temperature.In contrast, addition of trimethylsilyldiazomethane to ethylene at 55 deg C yields 1-trimethylsilyl-2-pyrazoline exclusively.The thermal isomerization of 3-trimethylsilyl-1-pyrazoline to 1-trimethylsilyl2-pyrazoline has been followed kinetically by proton NMR spectroscopy and the reverse reaction has been detected by gas phase pyrolysis.Thermal elimination of nitrogen from either pyrazoline leads to cyclopropyltrimethylsilane, allyltrimethylsilane and E- and Z-1-propenyltrimethylsilane.The relative rates of methylene-H migration to radical centers α and γ to silicon are approximately equal.
