Hydrodefluorination Research Articles

Room Temperature Regioselective Catalytic Hydrodefluorination of Fluoroarenes with trans-[Ru(NHC)4 H2 ] through a Concerted Nucleophilic Ru-H Attack Pathway.

The efficient and highly selective room temperature hydrodefluorination (HDF) of fluoroarenes by the trans-[Ru(IMe4 )4 H2 ] catalyst, 3, is reported. Mechanistic studies show 3 acts directly in catalysis without any ligand dissociation and DFT calculations indicate a concerted nucleophilic attack mechanism. The calculations fully account for the observed selectivities which corroborate earlier predictions regarding the selectivity of HDF.

Room Temperature Regioselective Catalytic Hydrodefluorination of Fluoroarenes with trans‐[Ru(NHC)4H2] through a Concerted Nucleophilic Ru−H Attack Pathway

AbstractThe efficient and highly selective room temperature hydrodefluorination (HDF) of fluoroarenes by the trans‐[Ru(IMe4)4H2] catalyst, 3, is reported. Mechanistic studies show 3 acts directly in catalysis without any ligand dissociation and DFT calculations indicate a concerted nucleophilic attack mechanism. The calculations fully account for the observed selectivities which corroborate earlier predictions regarding the selectivity of HDF.

“π-Hole−π” Interaction Promoted Photocatalytic Hydrodefluorination via Inner-Sphere Electron Transfer

We describe a metal-free, photocatalytic hydrodefluorination (HDF) of polyfluoroarenes (FA) using pyrene-based photocatalysts (Py). The weak "π-hole-π" interaction between Py and FA promotes the electron transfer against unfavorable energetics (ΔGET up to 0.63 eV) and initiates the subsequent HDF. The steric hindrance of Py and FA largely dictates the HDF reaction rate, pointing to an inner-sphere electron transfer pathway. This work highlights the importance of the size and shape of the photocatalyst and the substrate in controlling the electron transfer mechanism and rates as well as the overall photocatalytic processes.

How a Thermally Unstable Metal Hydrido Complex Can Yield High Catalytic Activity Even at Elevated Temperatures.

Despite their instability in ethereal solvents, organotitanium hydride catalysts are successfully employed in catalysis at moderate to high temperatures (110 °C), even in the presence of alcohols. It is shown computationally (bond dissociation energy (BDE) analysis and energetic profile for regeneration) and experimentally (EPR studies and kinetic studies), with the specific example of hydrodefluorination (HDF), that despite the long standing belief, regeneration of Ti-H bonds from Ti-F bonds using silanes is endergonic. The resulting low concentration of Ti-H species is crucial for the catalytic stability of those systems. The resting state in the catalysis is a Ti-F species. The most promising silanes for regeneration are not the ones that have the strongest Si-F bond, but the ones that show the largest difference in Si-F and Si-H BDEs.

Rhodium-catalyzed electrochemical hydrodefluorination: A mild approach for the degradation of fluoroaromatic pollutants

Many fluoroorganic compounds are toxic and persistent, and achieving their efficient degradation under mild conditions is currently a challenge. Herein, we developed a new electrochemical hydrodefluorination (HDF) system based on rhodium electrocatalyst for the degradation of fluoroaromatic (FA) pollutants. The HDF system realized the rapid degradation of 18 representative FAs to form nonfluorinated organics and F− under mild conditions (room temperature and pressure, water medium, air atmosphere, without the use of hazardous reagents). This study may provide a new promising alternative for the practical treatment of waste water containing FA pollutants.

Mechanistic Study of Ru-NHC-Catalyzed Hydrodefluorination of Fluoropyridines: The Influence of the NHC on the Regioselectivity of C–F Activation and Chemoselectivity of C–F versus C–H Bond Cleavage

We describe a combined experimental and computational study into the scope, regioselectivity, and mechanism of the catalytic hydrodefluorination (HDF) of fluoropyridines, C5F5–xHxN (x = 0–2), at two Ru(NHC)(PPh3)2(CO)H2 catalysts (NHC = IPr, 1, and IMes, 2). The regioselectivity and extent of HDF is significantly dependent on the nature of the NHC: with 1 HDF of C5F5N is favored at the ortho-position and gives 2,3,4,5-C5F4HN as the major product. This reacts on to 3,4,5-C5F3H2N and 2,3,5-C5F3H2N, and the latter can also undergo further HDF to 3,5-C5F2H3N and 2,5-C5F2H3N. para-HDF of C5F5N is also seen and gives 2,3,5,6-C5F4HN as a minor product, which is then inert to further reaction. In contrast, with 2, para-HDF of C5F5N is preferred, and moreover, the 2,3,5,6-C5F4HN regioisomer undergoes C–H bond activation to form the catalytically inactive 16e Ru-fluoropyridyl complex Ru(IMes)(PPh3)(CO)(4-C5F4N)H, 3. Density functional theory calculations rationalize the different regioselectivity of HDF of C5F5N at 1 and 2 in terms of a change in the pathway that is operating with these two catalysts. With 1, a stepwise mechanism is favored in which a N → Ru σ-interaction stabilizes the key C–F bond cleavage along the ortho-HDF pathway. With 2, a concerted pathway favoring para-HDF is more accessible. The calculations show the barriers increase for the subsequent HDF of the lower fluorinated substrates, and they also correctly identify the most reactive C–F bonds. A mechanism for the formation of 3 is also defined, but the competition between C–H bond activation and HDF of 2,3,5,6-C5F4HN at 2 (which favors C–H activation experimentally) is not reproduced. In general, the calculations appear to overestimate the HDF reactivity of 2,3,5,6-C5F4HN at both catalysts 1 and 2.

Mechanistic Studies of the Rhodium NHC Catalyzed Hydrodefluorination of Polyfluorotoluenes

The six-membered-ring NHC complexes Rh(6-NHC)(PPh3)2H (6-NHC = 6-iPr (1), 6-Et (2), 6-Me (3)) have been employed in the catalytic hydrodefluorination (HDF) of C6F5CF3 and 2-C6F4HCF3. Stoichiometric studies showed that 1 reacted with C6F5CF3 at room temperature to afford cis- and trans-phosphine isomers of Rh(6-iPr)(PPh3)2F (4), which re-form 1 upon heating with Et3SiH. Although up to three consecutive HDF steps prove possible with C6F5CF3, the ultimate effectiveness of the catalysts is limited by their propensity to undergo C–H activation of partially fluorinated toluenes to give, for example, Rh(6-iPr)(PPh3)2(C6F4CF3) (7), which was isolated and structurally characterized.

Influence of the Diphosphine Coordinated to Molybdenum and Tungsten Triangular M3S4 Cluster Hydrides in the Catalytic Hydrodefluorination of Pentafluoropyridine

Hydrido molybdenum and tungsten(IV) cluster cations of formula [M3S4H3(dppe)3]+ (dppe = 1,2-(bis)dimethylphosphinoethane), [Mo-1]+ (M = Mo) and [W-1]+ (M = W), have been isolated by reacting their halide precursors with borohydride. Synthetic procedures have been optimized by appropriate choice of the solvent. Furthermore, [M3S4F3(dppe)3]+ fluorido cluster complexes, [Mo-2]+ (M = Mo) and [W-2]+ (M = W) have been prepared through halogen substitution reactions using an excess of cesium fluoride. The structures of [Mo-1]+ and [Mo-2]+ have been determined by single crystal X-ray diffraction experiments. These [M-1]+ hydrido and [M-2]+ fluorido clusters have been used as catalysts and precatalysts, respectively, in the catalytic hydrodefluorination (HDF) of pentafluoropyridine using HSiMe2Ph as hydrogen source. The reaction proceeds under microwave and reflux conditions to selectively afford 2,3,5,6-tetrafluoropyridine. The [W-1]+ hydrido cluster is the most efficient catalyst with turnover numbers of 124, while the [Mo-1]+ hydrido cluster reacts faster. Fluorido [Mo-2]+ and [W-2]+ complexes provide lower yields and turnover numbers. In general, the molybdenum and tungsten [M-1]+ and [M-2]+ diphosphino complexes are more efficient than their dmpe (1,2-(bis)dimethylphosphinoethano) analogues and activate pentafluoropyridine under softer conditions.

On the Catalytic Hydrodefluorination of Fluoroaromatics Using Nickel Complexes: The True Role of the Phosphine

Homogeneous catalytic hydrodefluorination (HDF) of fluoroaromatics under thermal conditions was achieved using nickel(0) compounds of the type [(dippe)Ni(η(2)-C6F6-nHn)] where n = 0-2, as the catalytic precursors. These complexes were prepared in situ by reacting the compound [(dippe)Ni(μ-H)]2 with the respective fluoroaromatic substrate. HDF seems to occur homogeneously, as tested by mercury drop experiments, producing the hydrodefluorinated products. However, despite previous findings by other groups, we found that these HDF reactions were actually the result of direct reaction of the alkylphosphine with the fluoroaromatic substrate. This metal- and silane-free system is the first reported example of a phosphine being able to hydrodefluorinate on its own.

Copper-Catalyzed Hydrodefluorination of Fluoroarenes

Copper-Catalyzed Hydrodefluorination of Fluoroarenes

Copper‐Catalyzed Hydrodefluorination of Fluoroarenes by Copper Hydride Intermediates

C F bond activation attracts much attention because of the rapid growth of fluorocarbons in pharmaceuticals, agrochemicals, and new materials. Such transformations not only provide new routes to the fluorinated organics, but also offer a fundamental understanding for C F bond cleavage and functionalization. Previous experimental and theoretical studies demonstrated the effectiveness of late transition metals (group 8–10) such as Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, and Pt for their electron-rich nature and the relatively weak M F bonds, which are important for catalytic functionality. Recently, we explored the reactivity of group 11 metal complexes and found that gold(I) complexes have good catalytic reactivity toward hydrodefluorination (HDF) of fluoroarenes. Despite the tremendous progress made, most catalytic systems suffered from either low catalyst turnovers, limited substrate scope, or harsh reaction conditions. For example, gold(I) complexes are reactive only for the substrates with strong electron-withdrawing substituents, and their efficiency was greatly dependent on the electronicdonating additives. To address these issues, we continued to explore the more-active group 11 metals such as copper, as we were inspired by the success of gold. In this context, we report herein the first example of a copper(I)-catalyzed HDF of fluoroarenes, and it features high reactivity, good regioselectivity, and a broad substrate scope. Since Subramanian and Manzer reported the CuF2mediated fluorination of aromatics, copper-catalyzed C F bond formation has been developed by the groups of Hartwig, Lectka, and others. In contrast, for catalytic C F bond activation, copper has been rarely studied. Ribas and coworkers recently showed that a Cu/Cu redox cycle activated C X bonds (X=halogens) using triazamacrocyclic ligand, thus indicating an oxidative addition mechanism. Herein, we found that for HDF reactions, copper hydrides exhibited an unprecedented reactivity toward C F bonds. Moreover, density functional theory (DFT) calculations suggest that C F bond activation by copper hydrides proceeds through a mechanism involving nucleophilic attack, and represents an alternative strategy for copper activating C F bonds. At the outset of our study, we searched for optimal HDF reaction conditions for perfluoronitrobenzene (PFNB). We first applied the our previous catalytic gold system but replaced gold(I) with [Cu(MeCN)4PF6]. Screening silanes (see Table S1 in the Supporting Information) such as HSi(OMe)3, HSiEt3, PMHS, H2SiPh2, and HSiMe2Ph, showed that HSiMe2Ph was the best hydrogen source (conv. 40%). Solvent screening resulted THF providing the highest yield (60%; see Table S2 in the Supporting Information). We then examined ligand effects and the results are listed in Table 1. In

Computational study of the hydrodefluorination of fluoroarenes at [Ru(NHC)(PR3)2(CO)(H)2]: predicted scope and regioselectivities

Density functional theory calculations have been employed to investigate the scope and selectivity of the hydrodefluorination (HDF) of fluoroarenes, C6F(6-n)H(n) (n = 0-5), at catalysts of the type [Ru(NHC)(PR3)2(CO)(H)2]. Based on our previous study (Angew. Chem., Int. Ed., 2011, 50, 2783) two mechanisms featuring the nucleophilic attack of a hydride ligand at a fluoroarene substrate were considered: (i) a concerted process with Ru-H/C-F exchange occurring in one step; and (ii) a stepwise pathway in which the rate-determining transition state involves formation of HF and a Ru-σ-fluoroaryl complex. The nature of the metal coordination environment and, in particular, the NHC ligand was found to play an important role in both promoting the HDF reaction and determining the regioselectivity of this process. Thus for the reaction of C6F5H, the full experimental system (NHC = IMes, R = Ph) promotes HDF through (i) more facile initial PR3/fluoroarene substitution and (ii) the ability of the NHC N-aryl substituents to stabilise the key C-F bond breaking transition state through F···HC interactions. This latter effect is maximised along the lower energy stepwise pathway when an ortho-H substituent is present and this accounts for the ortho-selectivity seen in the reaction of C6F5H to give 1,2,3,4-C6F4H2. Computed C-F bond dissociation energies (BDEs) for C6F(6-n)H(n) substrates show a general increase with larger n and are most sensitive to the number of ortho-F substituents present. However, HDF is always computed to remain significantly exothermic when a silane such as Me3SiH is included as terminal reductant. Computed barriers to HDF also generally increase with greater n, and for the concerted pathway a good correlation between C-F BDE and barrier height is seen. The two mechanisms were found to have complementary regioselectivities. For the concerted pathway the reaction is directed to sites with two ortho-F substituents, as these have the weakest C-F bonds. In contrast, reaction along the stepwise pathway is directed to sites with only one ortho-F substituent, due to difficulties in accommodating ortho-F substituents in the C-F bond cleavage transition state. Calculations predict that 1,2,3,5-C6F4H2 and 1,2,3,4-C6F4H2 are viable candidates for HDF at [Ru(IMes)(PPh3)2(CO)(H)2] and that this would proceed selectively to give 1,2,4-C6F3H3 and 1,2,3-C6F3H3, respectively.

π–π Interaction Assisted Hydrodefluorination of Perfluoroarenes by Gold Hydride: A Case of Synergistic Effect on C–F Bond Activation

"Synergistic effect" is prevalent in natural metalloenzymes in activating small molecules, and the success has inspired the development of artificial catalysts capable of unprecedented organic transformations. In this work, we found that the attractive π-π interaction between organic additives (as electron-donors) and the perfluorinated arenes (as electron acceptors) is effective in gold hydride catalyzed activation of C-F bonds, specifically hydrodefluorination (HDF) of perfluoroarenes catalyzed by the Sadighi's gold hydrides [(NHC)AuH] (NHC = N-heterocyclic carbene). Although a weak interaction between [(NHC)AuH] and perfluoroarenes was observed from (1)H NMR and UV-vis spectroscopies, low reactivity of [(NHC)AuH] toward HDF was found. In contrast, in the presence of p-N,N-dimethylaminopyridine (DMAP), the HDF of perfluoroarenes with silanes can be efficiently catalyzed by [(NHC)AuH], resulting in mainly the para-hydrodefluorinated products with up to 90% yield and 9 turnovers. The yield of the reaction increases with the more electron-withdrawing groups and degree of fluorination on the arenes, and the HDF reaction also tolerates different function groups (such as formyl, alkynyl, ketone, ester, and carboxylate groups), without reduction or hydrogenation of these function groups. To reveal the role of DMAP in the reactions, the possible π-π interaction between DMAP and perfluoroarenes was suggested by UV-vis spectral titrations, (1)H NMR spectroscopic studies, and DFT calculations. Moreover, (1)H and (19)F-NMR studies show that this π-π interaction promotes hydrogen transfer from [(NHC)AuH] to pyridyl N atom, resulting in C-F bond cleavage. The interpretation of π-π interaction assisted C-F activation is supported by the reduced activation barriers in the presence of DMAP (31.6 kcal/mol) than that in the absence of DMAP (40.8 kcal/mol) for this reaction. An analysis of the charge distribution and transition state geometries indicate that this HDF process is controlled by the π-π interaction between DMAP and perfluoroarenes, accompanied with the changes of partial atomic charges.

Titanium‐Catalyzed Vinylic and Allylic CF Bond Activation—Scope, Limitations and Mechanistic Insight

The hydrodefluorination (HDF) of fluoroalkenes in the presence of a variety of titanium catalysts was studied with respect to scope, selectivity, and mechanism. Optimization revealed that the catalyst requires low steric bulk and high electron density; secondary silanes serve as the preferred hydride source. A broad range of substrates yield partially fluorinated alkenes, such as previously unknown (Z)-1,2-(difluorovinyl)ferrocene. Mechanistic studies indicate a titanium(III) hydride as the active species, which forms a titanium(III) fluoride by H/F exchange with the substrate. The HDF step can follow both an insertion/elimination and a σ-bond metathesis mechanism; the E/Z selectivity is controlled by the substrate. The catalysts' ineffieciency towards fluoroallenes was rationalized by studying their reactivity towards Group 6 hydride complexes.

Catalytic C‐F Bond Activation of Perfluoroarenes by Tricoordinated Gold(I) Complexes

AbstractWe report the first example of gold catalyzing CF bond activation for perfluoroarenes in the presence of silanes. Tricoordinated gold(I) complexes supported by Xantphos‐type ligands, such as Xantphos and tBuXantphos ligands, exhibit efficacy in the hydrodefluorination (HDF) of various types of perfluoroarenes. For [tBuXantphosAu(AuCl2)], the highest turnover number is up to 1000 in the HDF of pentafluoronitrobenzene with diphenylsilane. An examination of functional group tolerance shows the orthogonality of this gold(I) catalytic protocol to ketone, ester, carboxylate, alkynyl, alkenyl and amide groups, suggesting its potential application in chemoselective CF activations. Mechanistic studies show that the equilibrium between tetracoordinated [L2Au]+ and [LAu]+ is important for the reactivity of gold catalysts, which is dependent on the sterically bulky group of Xantphos‐type ligands. Furthermore, computational studies for the possible reaction pathways suggest that direct oxidative addition of CF bonds by gold(I) cation might be the key step during these catalytic reactions.

Mechanism of the Catalytic Hydrodefluorination of Pentafluoropyridine by Group Six Triangular Cluster Hydrides Containing Phosphines: A Combined Experimental and Theoretical Study

The catalytic hydrodefluorination (HDF) of pentafluoropyridine in the presence of arylsilanes is catalyzed by the tungsten and molybdenum(IV) cluster hydrides of formula [M3S4H3(dmpe)3]+, W-1+ for M = W and Mo-1+ for M = Mo (dmpe = 1,2-(bis)dimethylphosphinoethane). The reaction proceeds regioselectively at the 4-position under microwave radiation to yield the 2,3,5,6-tetrafluoropyridine. Catalytic activity is higher for the tungsten complexes with turnover numbers close to 100, while reactions catalyzed by molybdenum compounds are faster. A mechanism for the HDF reaction has been proposed that explains these differences based on DFT calculations. The mechanism involves partial decoordination of the diphosphine ligand that generates an empty position in the metal coordination sphere. This position together with its neighbor M−H site are used to activate the C−F bond of the pentafluoropyridine through a M−H/C−F σ-bond metathesis mechanism involving a four-center transition state to give 2,3,5,6-tetrafluoro...

Catalytic Hydrodefluorination of Aromatic Fluorocarbons by Ruthenium N-Heterocyclic Carbene Complexes

The catalytic hydrodefluorination (HDF) of hexafluorobenzene, pentafluorobenzene, and pentafluoropyridine with alkylsilanes is catalyzed by the ruthenium N-heterocyclic carbene (NHC) complexes Ru(NHC)(PPh(3))(2)(CO)H(2) (NHC = SIMes (1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene) 13, SIPr (1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) 14, IPr (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) 15, IMes (1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene) 16). Catalytic activity follows the order 15 > 13 > 16 > 14, with 15 able to catalyze the HDF of C(6)F(5)H with Et(3)SiH with a turnover number of up to 200 and a turnover frequency of up to 0.86 h(-1). The catalytic reactions reveal (i) a novel selectivity for substitution at the 2-position in C(6)F(5)H and C(5)F(5)N, (ii) formation of deuterated fluoroarene products when reactions are performed in C(6)D(6) or C(6)D(5)CD(3), and (iii) a first-order dependence on [fluoroarene] and zero-order relationship with respect to [R(3)SiH]. Mechanisms are proposed for HDF of C(6)F(6) and C(6)F(5)H, the principal difference being that the latter occurs by initial C-H rather than C-F activation.

Hydrodefluorination of non-activated C–F bonds by diisobutyl-aluminiumhydride via the aluminium cation [ i-Bu 2Al] +

A novel system for the hydrodefluorination (HDF) of non-activated C–F bonds at room-temperature is described. The reaction of i-Bu 2AlH with [Ph 3C][B(C 6F 5) 4] ( 1), [Ph 3C][Al(C 6F 5) 4] ( 2) and [Ph 3C][Al{OC(CF 3) 3} 4] ( 3) as precatalysts leads under formation of triphenylmethane to the aluminium cation [ i-Bu 2Al] + and the non-coordinating anions [M(C 6F 5) 4] − (M = B, Al) and [Al{OC(CF 3) 3} 4] −. The formed aluminium cation is very reactive towards C–F bonds and easily forms i-Bu 2AlF releasing a carbocation that abstracts the hydride of excess i-Bu 2AlH and yields the corresponding hydrocarbon. Thereby, the active species [ i-Bu 2Al] + is regenerated and can realize a catalytic cycle. For 1-fluorohexane as an example including non-activated C–F bonds different activities were found (TON: 1: 20; 2: 12; 3: 30) in cyclohexane as solvent.

Room-temperature catalytic hydrodefluorination of pentafluoro-pyridine by zirconocene fluoro complexes and diisobutylaluminumhydride

Mixtures consisting of zirconocene difluorides C p ′ 2 Zr F 2 (Cp′ = substituted or nonsubstituted η 5-cyclopentadienyl) as pre-catalysts and diisobutylaluminumhydride i-Bu 2AlH as activator were found to be active catalysts in the room-temperature hydrodefluorination (HDF) of fluorinated pyridines. Evaluation of these systems established rac-(ebthi)ZrF 2 ( 1) and Cp 2ZrF 2 ( 3) together with i-Bu 2AlH as active catalysts in the room-temperature hydrodefluorination (HDF) of pentafluoro-pyridine. The active species for the conversion were the actually formed hydrides [ rac-(ebthi)ZrH(μ-H)] 2 ( 2) and [Cp 2ZrH(μ-H)] 2 ( 4). The results we obtained (rt, 24 h, turn over number 67) showed a significantly better performance compared to other investigations published before for this HDF reaction.

Synthesis and Reactivity of Low-Coordinate Iron(II) Fluoride Complexes and Their Use in the Catalytic Hydrodefluorination of Fluorocarbons

Transition metal fluoride complexes are of interest because they are potentially useful in a multitude of catalytic applications, including C-F bond activation and fluorocarbon functionalization. We report the first crystallographically characterized examples of molecular iron(II) fluorides: [L(Me)Fe(mu-F)]2 (1(2)) and L(tBu)FeF (2) (L = bulky beta-diketiminate). These complexes react with donor molecules (L'), yielding trigonal-pyramidal complexes L(R)FeF(L'). The fluoride ligand is activated by the Lewis acid Et2O.BF3, forming L(tBu)Fe(OEt2)(eta1-BF4) (3), and is also silaphilic, reacting with silyl compounds such as Me3SiSSiMe3, Me3SiCCSiMe3, and Et3SiH to give new thiolate L(tBu)FeSSiMe3 (4), acetylide L(tBu)FeCCSiMe3 (5), and hydride [L(Me)Fe(mu-H)]2 (6(2)) complexes. The hydrodefluorination (HDF) of perfluorinated aromatic compounds (hexafluorobenzene, pentafluoropyridine, and octafluorotoluene) with a silane R3SiH (R3 = (EtO)3, Et3, Ph3, (3,5-(CF3)2C6H3)Me2) is catalyzed by addition of an iron(II) fluoride complex, giving mainly the singly hydrodefluorinated products (pentafluorobenzene, 2,3,5,6-tetrafluoropyridine, and alpha,alpha,alpha,2,3,5,6-heptafluorotoluene, respectively) in up to five turnovers. These catalytic perfluoroarene HDF reactions proceed with activation of the C-F bond para to the most electron-withdrawing group and are dependent on the degree of fluorination and solvent polarity. Kinetic studies suggest that hydride generation is the rate-limiting step in the HDF of octafluorotoluene, but the active intermediate is unknown. Mechanistic considerations argue against oxidative addition and outer-sphere electron transfer pathways for perfluoroarene HDF. Fluorinated olefins are also hydrodefluorinated (up to 10 turnovers for hexafluoropropene), most likely through a hydride insertion/beta-fluoride elimination mechanism. Complexes 1(2) and 2 thus provide a rare example of a homogeneous system that activates C-F bonds without competitive C-H activation and use an inexpensive 3d transition metal.