Activation and Functionalization of Vinylic C−F Bonds by Transition Metal Compounds: The Factors Determining Reactions between Nucleophiles and a (Perfluorovinyl)diiron(I) Complex; Syntheses of Diiron Derivatives Containing New C−N, C−S, C−H and C−O Bonds

Abstract

The reactions between alcohols ROH (R = Me, Et) and RR(OH)2 (RR = CH2−CH2) and the [perfluoro(sulfanyl)vinyl]diiron complex [{Fe(CO)3}2{µ‐C(SMe)(CF3)CβCαF2}] (1) in THF at room temperature involve substitution at the Cα atom to give new (alkoxymethylene)thiaferracyclobutadiene compounds [{Fe(CO)3}2{µ‐S(Me)C(CF3)CβCα(OR)2}] [R = Me (2a), Et (2b); RR = CH2CH2 (2c)]. Treatment of 1 with aniline and (methoxycarbonyl)hydrazine, bases of intermediate strength according to Pearson, produces α,β‐substituted thiaferracyclopentadiene [{Fe(CO)3}2{µ‐S(Me)C(CF3)Cβ(NHR)Cα(NHR)}] [R = Ph (5a), NHC(O)OMe (5b)] complexes. It is suggested that these compounds form through initial nucleophilic attack at Cα to give the zwitterionic intermediate [{Fe(CO)3}2{µ‐S(Me)C(CF3)CC(NRH)2}] (f). Thermally induced C−F bond activation is a feature of these reactions. When 1 reacts with thioamides containing three “hard” competitive primary and secondary amine functions and one “soft” thione function, the nucleophile first attacks at Cα through a secondary amine and, in a second step, at Cβ through the thiol function to give α,β adducts [{Fe(CO)3}2{µ‐S(Me)C(CF3)CβSC(=NR2)N(R1)Cα(Cβ−Cα)] [R1 = NH2, R2 = CH3 (6a); R1 = CH3, R2 = H (6b); R1 = R2 = CH3 (6c)] possessing novel iminothiazolidine systems fused to the five‐membered metallacyclic ring. Treatment of 1 with acetylhydrazine, which has three “hard” nucleophilic functions, results in the formation of the compound [{Fe(CO)3}2{µ‐S(Me)C(CF3)C(H)C(10)NNC(Me)O(C(10)−O)}] (7a), in which an oxadiazole function is fused to the thiaazaferracyclohexene ring. The position of the fluorine substituent on the CαCβCγ(CF3)S(Me) ring of ferracyclopentadiene complexes has been found to be the essential factor determining the specific activation of the C−F bond. A single fluoro substituent attached to the β‐carbon atom of the chain can be activated by nucleophiles to give α,β adducts [{Fe(CO)3}2{µ‐S(Me)C(CF3)Cβ(X)Cα(NRR′)}] [X = OR′′, R = R′ = R′′ = Me (3a); X = OR′′, R = R′′ = Me, R′′ = C(O)NMe2 (3b); X = SR′′ (4)]. In contrast, complexes in which a single fluorine atom is linked to the α‐carbon atom do not undergo C−F bond cleavage reactions. X‐ray structures of compounds 2a, 3b, 5a, 5b, 6a and 7a are reported.

DFT Studies on the Mechanism of Palladium(IV)-Mediated C–H Activation Reactions: Oxidant Effect and Regioselectivity

“…1 Numerous works in the literature focused on the construction of carbon−carbon 2 or carbon−heteroatom bonds (e.g., C−N, 3 C−O, 4 and C−S 5 ) via direct C−H activation, employing nucleophiles, such as organometallics, 6 alcohols, 7 carboxylates, 8 hydrazoates, 9 and amides, 10 as coupling partners.…”

“…As environmental and atom-economical advantages, transitionmetal-catalyzed C−H activation has been widely used as a versatile synthetic methodology, with important applications to functionalizing hydrocarbons. 1 Numerous works in the literature focused on the construction of carbon−carbon 2 or carbon−heteroatom bonds (e.g., C−N, 3 C−O, 4 and C−S 5 ) via direct C−H activation, employing nucleophiles, such as organometallics, 6 alcohols, 7 carboxylates, 8 hydrazoates, 9 and amides, 10 as coupling partners.…”

Imine-assisted C–F bond activation by electron-rich iron complexes supported by trimethylphosphine

“…3). The trans-influence of imine N atom (N1) leads to shortening of Fe-P3 bond length (2.2279( 10 3 The molecular structure of 10 with 30% probability ellipsoids (all of the hydrogen atoms are omitted for clarity), selected bond distances (A ˚) and angles (deg): Fe-N1 1.970(3), Fe-C1 2.007(4), Fe-C16 2.031(4), Fe-P3 2.2279 (10), Fe-P2 2.2427 (11), Fe-P1 2.2465 (11), N1-C7 1.303(5), C7-C6 1.415(5); N1-Fe-C1 80.56(13), N1-Fe-C16 81.35(13), C1-Fe-C16 161.91 (15), N1-Fe-P3 174.17 (9), C1-Fe-P3 93.61 (11), C16-Fe-P3 104.48 (11), C16-Fe-P2 85.32 (10), C1-Fe-P1 93.39 (10), C16-Fe-P1 86.39 (10) (C24-N2 = 1.362(4) A ˚) and C13-N1 = 1.360(4) A ˚) in complex 11 are even longer than the aforementioned C N distances as a result of p-coodination of the C N bond, which significantly weakens the C N bond. Complex 11 has a C2 symmetry axis through the central iron atom.…”

“…14 It has been confirmed that the perfluorovinyldiiron complex reacts readily with nucleophiles to give novel organometallic complexes through an unusual C-F bond cleavage process. 15 Holland reported the synthesis and reactivity of low-coordinate iron(II) fluoride with diketiminate iron(II) ligands. 16 It was found that direct reaction of fluorinated aromatics with iron(II) hydride complexes did not occur, but C-F bond activation became feasible in the presence of silane as a fluoride trap.…”

Carbon–fluorine bond activation—looking at and learning from unsolvated systems

“…However, recent studies since the reviews mentioned above should not be ignored. They focused on metal complexes of, e.g., Ti, 9 Zr, [10][11][12] Fe, 13 Ni, 14,15 Ru, 16,17 Rh, [18][19][20][21][22] Re, 23 Os, 24 Ir, 25,26 and Yb. 27 While not directly connected to carbon-fluorine bond activation, it appears that enzymes can be employed to form such bonds.…”