C–F Bond Activation of P(C₆F₅)₃by Ruthenium Dihydride Complexes: Isolation and Reactivity of the “Missing” Ru(PPh₃)₃H(halide) Complex, Ru(PPh₃)₃HF

Abstract

The major product of the reaction between Ru­(IMe4)2(PPh3)2H2 (1; IMe4 = 1,3,4,5-tetramethylimidazol-2-ylidene) and P­(C6F5)3 (PCF) is the five-coordinate complex Ru­(IMe4)2(PF2{C6F5})­(C6F5)H (2), which is formed via a complex series of C–F/P–C bond cleavage and P–F bond formation steps. In contrast, hydrodefluorination of all six ortho C–F bonds in PCF occurs with Ru­(PPh3)4H2 to afford Ru­(PPh3)3HF (3). NaBArF 4 abstracted the fluoride ligand in 3 to give [Ru­({η6-C6H5}­PPh2)­(PPh3)2H]­[BArF 4], while B2pin2 reacted with 3 in C6D6 to yield a mixture of [Ru­({η6-C6D6)­(PPh3)2H]+ and Ru­(PPh3)4H2. The treatment of 3 with HBpin (5 equiv) and HSiR3 (R = Et, Ph; 2 equiv) afforded Ru­(PPh3)3(σ-HBpin)­H2 and Ru­(PPh3)3(SiR3)3H3, respectively. No stable substitution products were generated when 3 was reacted with Me3SiX (X = CF3, C6F5).

An Iridium-Stabilized Borenium Intermediate

“…Free HB Pin that was formally released from 7 (and substituted by THF) could not be detected, suggesting that it was transformed into one or several products through an unknown process. Again, these observations support the electrophilic character of the B Pin group, with formation of the resulting product [F 2 B Pin ] − being most likely due to the remaining Lewis acidity of transient FB Pin . On the other hand, the reaction of 7 with excess Et 3 N in CD 2 Cl 2 was incomplete after stirring the mixture for 15 h at room temperature (see the Supporting Information).…”

Ruthenium-Catalyzed Hydrodefluorination with Silane as the Directing and Reducing Group

“…A plausible catalytic cycle consistent with the experimental observations was proposed for the HDF reaction (Scheme ). The (pincer)­Ru­(II) hydride complex ( A ) initiates this process via oxidative addition of the Si–H bond to form a Ru­(IV) intermediate ( B ) . The concerted process involving the migration of the ortho -F to Si and the cleavage of the C­(sp 2 )–Si bond would generate a Ru­(IV)–aryne intermediate ( C ). , Following migratory insertion of the aryne into the Ru–H bond, the resulting aryl Ru­(IV) species ( D ) is subject to C­(sp 2 )–Si bond reductive elimination to form the HDF product and regenerate A .…”

Palladium-Catalyzed Difluoromethylation of Aryl Chlorides and Bromides with TMSCF2H

“…The methylated product of this reaction ( 22 ) could be formed via the palladium-catalyzed reaction of the aryl chloride substrate with either TMSCF 2 H or TMSF (the product generated after transmetalation) . To distinguish these possibilities, we conducted the reaction of 21 with TMSF (formed in situ from a prestirred solution of TMSCl/CsF, 1:2, 2 equiv) with each catalyst system. Product 22 was not detected with either catalyst.…”