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

Abstract

The diiridium complex [Ir2(CO)3(μ-H)(depm)2]+ (1) reacts with vinyl fluoride, 1,1-difluoroethylene, trifluoroethylene, and tetrafluoroethylene, undergoing C–F bond activation in all cases, in addition to C–H activation in the incompletely substituted fluoroolefins. Reaction of 1 with vinyl fluoride readily undergoes geminal C–F/C–H activation, resulting in the bridging vinylidene product, [Ir2(H)(CO)3(μ-CCH2)(depm)2]+ (2). Compound 1 reacts with 1,1-difluoroethylene at subambient temperature to give minor amounts of [Ir2(CO)3(κ1:η2-CCH)(depm)2]+ (4), resulting from the loss of 2 equiv of HF from the fluoroolefin complex, along with a mixture of two isomers of [Ir2(C(F)CH2)(CO)3(μ-CF2CH2)(depm)2]+ (5a/5b), in which 2 equiv of the olefin has been incorporated. Compound 1 also reacts with trifluoroethylene at −30 °C, giving a 1:1 mix of isomers of the trifluoroethylene-bridged species [Ir2(H)(CO)3(μ-CFHCF2)(depm)2]+ (7a/7b), and warming this mixture above −15 °C converts both isomers to two products, [Ir2(H)(CO)3(μ-CCF2)(depm)2]+ (8), in which the geminal C–F and C–H bonds in the fluoroolefin have been activated, and [Ir2(H)(CO)3(μ-CHCF3)(depm)2]+ (9), the result of a [1,2]-fluoride shift to give the bridging 2,2,2-trifluoroethylidene moiety. Compound 9 reacts further with a second equivalent of trifluoroethylene over 12 h to produce the 2,2,2-trifluoroethylidene/cis-difluorovinyl complex, [Ir2(C(F)CFH)(CO)3(μ-CHCF3)(depm)2]+ (10). Finally, tetrafluoroethylene reacts with 1 to produce the bridged adduct, [Ir2(H)(CO)3(μ-CF2CF2)(depm)2]+ (11), followed by a single C–F activation to give [Ir2(C(F)CF2)(CO)3(depm)2]+ (12). The roles of the hydride ligand and exogenous water in the C–F activation processes are discussed.

Selectivity of C–H Activation and Competition between C–H and C–F Bond Activation at Fluorocarbons

“…Catalytic dehalogenation (F/Cl) of fluorinated/chlorinated ethylene by (PPh 3 ) 3 RhCl in the presence of Et 3 SiH at 35 °C gives ethylene as the final product with the intermediate formation of monohalogenated (F/Cl) ethylene. 244Activation of both C-H and C-F bonds in partially fluorinated alkenes has been observed in )methane, -Et 2 PCH 2 PEt 2 ) 245. The reaction of the diiridium complex with vinyl fluoride at ambient temperature results in a product derived from C-H and C-F that dominates over the alternative where two C-H bonds have been activated (Scheme 37).…”

C−H and C−F Bond Activation Reactions of Fluorinated Propenes at Rhodium: Distinctive Reactivity of the Refrigerant HFO‐1234yf

“…One example by Cowie et al. demonstrates simultaneous C−F and C−H bond activations of various polyfluorinated ethylene derivatives using a diiridium hydrido carbonyl complex . Though C−H bond activations at rhodium are well‐known with fluoroaromatics and also occur at [Rh(E)(PEt 3 ) 3 ], they often compete with C−F bond activation reactions …”

“…Remarkably, at HFO‐1234yf, a C−H bond activation followed by a 1,2‐fluorine shift occur. While C−F bond activation and C−H bond activation are two well‐known reactions, the combination of both is scarce . The reported strategy might open new routes for the synthesis of fluorinated building blocks.…”

Synthesis and Characterization of RhIII–MII (M = Pt, Pd) Heterobimetallic Complexes Based on a Bisphosphine Ligand: Tandem Reactions Using Ethanol

“…Tandem catalysis refers to the combination of two steps in one, which makes the process shorter and saves energy, as the interim purification is avoided . Additionally, the usage of one-pot multistep reactions has been reported as an important and effective pathway for the construction of C–N , and C–C bonds , or activation of C–F, , and C–H bonds , in organic synthesis. Heterobimetallic compounds can be an option for tandem catalytic processes .…”