Facile Carbon–Fluorine Bond Activation and Subsequent Functionalisation of 1,1‐Difluoroethylene and Tetrafluoroethylene Promoted by Adjacent Metal Centres

Abstract

The bridging fluoroolefin ligands in the complexes [Ir(2)(CH(3))(CO)(2)(μ-olefin)(dppm)(2)][OTf] (olefin = tetrafluoroethylene, 1,1-difluoroethylene; dppm = μ-Ph(2)PCH(2)PPh(2); OTf(-) = CF(3)SO(3)(-)) are susceptible to facile fluoride ion abstraction. Both fluoroolefin complexes react with trimethylsilyltriflate (Me(3)SiOTf) to give the corresponding fluorovinyl products by abstraction of a single fluoride ion. Although the trifluorovinyl ligand is bound to one metal, the monofluorovinyl group is bridging, bound to one metal through carbon and to the other metal through a dative bond from fluorine. Addition of two equivalents of Me(3)SiOTf to the tetrafluoroethylene-bridged species gives the difluorovinylidene-bridged product [Ir(2)(CH(3))(OTf)(CO)(2)(μ-OTf)(μ-C=CF(2))(dppm)(2)][OTf]. The 1,1-difluoroethylene species is exceedingly reactive, reacting with water to give 2-fluoropropene and [Ir(2)(CO)(2)(μ-OH)(dppm)(2)][OTf] and with carbon monoxide to give [Ir(2)(CO)(3)(μ-κ(1):η(2)-C≡CCH(3))(dppm)(2)][OTf] together with two equivalents of HF. The trifluorovinyl product [Ir(2)(κ(1)-C(2)F(3))(OTf)(CO)(2)(μ-H)(μ-CH(2))(dppm)(2)][OTf], obtained through single C-F bond activation of the tetrafluoroethylene-bridged complex, reacts with H(2) to form trifluoroethylene, allowing the facile replacement of one fluorine in C(2)F(4) with hydrogen.

Reactivity of platinum alkyne complexes towards N-fluorobenzenesulfonimide: formation of platinum compounds bearing a β-fluorovinyl ligand

“…Note that fluorinated vinyl entities can be rather stable at transition metal centres. 43,[131][132][133][134][135][136][137][138][139][140] However, a reaction of 8 with dihydrogen resulted in the formation of [Pt{N(SO 2 Ph) 2 }(H){κ 2 -(P,N)-iPr 2 PC 2 H 4 NMe 2 }] (12) and the fluorinated organic product (Z)-(1-fluoroethene-1,2-diyl)dibenzene.…”

Catalytic Transformations of Fluorinated Olefins

“…The reaction employing (dppp)NiCl 2 in place of (dppp) PdCl 2 as a catalyst in the presence of an excess amount of ( p-tol)MgBr affords the bis-substituted product as a major product. Our group has achieved the first catalytic transformation of tetrafluoroethylene (TFE; CF 2 ¼CF 2 ) [60], whereas C-F bond activation of TFE was accomplished in a few stoichiometric reactions [61][62][63][64][65]. In the presence of lithium iodide and a catalytic amount of Pd 2 (dba) 3 , the Negishi-type cross-coupling reaction of TFE with a variety of diarylzinc reagents proceeds in THF at 40 C, yielding the corresponding α,β,β-trifluorostyrene derivatives (Scheme 20).…”

Tandem C–F and C–H Bond Activation in Fluoroolefins Promoted by a Bis(diethylphosphino)methane-Bridged Diiridium Complex: Role of Water in the Activation Processes

“…First, a comparison of [Ir 2 (CO) 3 (μ-H)(depm) 2 ] + (1) and its dppm analogue has shown that, while the latter is unreactive to all fluoroolefins studied in this report, the depm compound (1) reacts readily with all of them. Second, although we had observed water-promoted C−F activation in some of the previous dppm chemistry, 68,69 this involvement was not nearly as extensive as it has proven to be in the current depm system, as will be discussed. Furthermore, in much of the chemistry reported herein, the smaller size of depm (and possibly its greater basicity) has allowed the incorporation of two fluoroolefin-derived fragments, whereas with dppm, only a single fluorocarbyl unit was incorporated.…”

“…The acetylide-bridged product (4) is highly reminiscent of the propynyl-bridged analogue, observed in the activation of 1,1-difluoroethylene by a dppm-bridged methyl complex. 69 Complex 4 displays a broad singlet in the 31 P{ 1 H} NMR spectrum, which changes little upon cooling to −80 °C, while the quintet at δ 181.6 ( 2 J CP = 5.6 Hz) in the 13 C{ 1 H} NMR spectrum of a 13 CO-enriched sample broadens slightly upon cooling. The static structure proposed should display two 31 P resonances, owing to the chemical inequivalence of both metals, and should also display three carbonyl resonances.…”

“…69 Following C−F bond activation in these fluoroolefins, a series of C−C and C−H bond-forming reactions have allowed the conversion of tetrafluoroethylene to trifluoroethylene; the conversion of trifluoroethylene into cisdifluoroethylene, 1,2-difluoropropene, 2,3-difluoropropene, and 1,1,1-trifluoroethane; and the conversion of 1,1-difluoroethylene to 2-fluoropropene. 68,69 In an attempt to extend the scope of cooperative C−F activation by binuclear complexes, we have made two key modifications. First, we have replaced the bridging dppm groups by the smaller, more basic depm (bis-(diethylphosphino)methane, Et 2 PCH 2 PEt 2 ), in order to improve access of the fluoroolefins to the metals and to utilize the ligand basicity as an aid in stabilizing the cationic products of fluoride-ion removal.…”