Mechanistic investigation of vinylic carbon–fluorine bond activation of perfluorinated cycloalkenes using Cp*2ZrH2 and Cp*2ZrHF

Synthesis of Fluorinated Building Blocks by Transition‐Metal‐Mediated Hydrodefluorination Reactions

“…Quantum mechanical calculations revealed only a relatively small energetic difference between the insertion–elimination and σ‐bond metathesis pathways; again, it is not surprising that minor alterations in the reagent structure and the substrate have a strong impact on the favored mechanism. The carbocyclic moiety’s high steric demand in the insertion product 29 b makes the insertion–elimination mechanism unfavorable, this effect is particularly pronounced for [Cp* 2 Zr(H) 2 ] 11b. [Cp* 2 Zr(H)(F)] ( 6 ) was found to be incapable of olefin insertion, making σ‐bond metathesis the only feasible path 11b,c…”

“…The carbocyclic moiety’s high steric demand in the insertion product 29 b makes the insertion–elimination mechanism unfavorable, this effect is particularly pronounced for [Cp* 2 Zr(H) 2 ] 11b. [Cp* 2 Zr(H)(F)] ( 6 ) was found to be incapable of olefin insertion, making σ‐bond metathesis the only feasible path 11b,c…”

Catalytic Transformations of Fluorinated Olefins

“…Although stoichiometric, the hydrodefluorination of a variety of vinylic fluorides has also been achieved by using zirconium and hafnium hydride species [24][25][26][27]. Their mechanistic studies have also been discussed in the literature; two different mechanisms, the insertion/elimination mechanism [25,28] and the concerted σ-bond metathesis mechanism [24,27] C for 0.5 h, trimethylsilane was fully consumed, and the generation of ethylene as well as trimethylsilyl fluoride was detected by NMR analysis (Scheme 6).…”

“…Their mechanistic studies have also been discussed in the literature; two different mechanisms, the insertion/elimination mechanism [25,28] and the concerted σ-bond metathesis mechanism [24,27] C for 0.5 h, trimethylsilane was fully consumed, and the generation of ethylene as well as trimethylsilyl fluoride was detected by NMR analysis (Scheme 6). In this reaction mixture, the osmium complex was OsHF(CO) (η 2 -CH 2 ¼CHF)(P t Bu 2 Me 2 ) 2 .…”

Structural Assignment of Fluorocyclobutenes by 19F NMR Spectroscopy – Comparison of Calculated 19F NMR Shielding Constants with Experimental 19F NMR Shifts

“…Attempts to obtain 3a through the reduction of 1 with LiAlH 4 led to mixtures of pentafluorocyclobutenes ( 2 ), tetrafluorocyclobutenes ( 3 ), and trifluorocyclobutenes ( 4 ) depending on the reaction conditions, and the target 3a had to be isolated by preparative GC . Similarly, the reduction of 1 with Cp* 2 ZrH 2 (Cp* = pentamethylcyclopentadienyl) or titanocene hydrides formed in situ gave mixtures of fluorocyclobutenes 2 – 4 .…”