An alternative copper halide-free route to obtain highly reactive trifluoromethylcopper species has been developed via the reaction of silver fluoride and trimethyl(trifluoromethyl)silane followed by a redox transmetallation with elemental copper. The composition of the reactive intermediate was investigated by means of UV/Vis/NIR, ESR, 19F NMR spectroscopy and ESI mass spectrometry. “Trifluoromethylcopper” prepared by the oxidative transmetallation route exhibits excellent reactivity and selectivity in substitutions of iodine or bromine bond to aromatic or heterocyclic compounds for trifluoromethyl groups without any additional catalyst.Graphical abstractHighlights► Convenient halide-free synthesis of trifluoromethyl silver–copper couples. ► Involvement of CuI, CuII and CuIII species. ► Efficient reagents for the introduction of trifluoromethyl groups. ► Effective C–C couplings with aromatics and activated sp3 carbons.

Se(C5F4N)2 and Te(C5F4N)2 were prepared via redox transmetalations of AgC5F4N and the corresponding elements in good yields. The crystal structures of both derivatives exhibit infinite chains caused by a weak intermolecular contact between the chalcogen and one nitrogen atom with a T-shaped (ψ-pentagonal-bipyramidal) ligand arrangement. Crystallization of both reagents from dimethylsulfoxide gave single crystals of the corresponding 1:1 adducts that crystallize in infinite chains best expressed by the formula [E(C5F4N)2·(μ-DMSO)]∞ (E = Se, Te). In these cases, the coordination spheres of selenium and tellurium are square-planar (ψ-octahedral). Similar effects are found in the molecular structures of [Te(C5F4N)2·TMTU]∞ and [Te(C6F5)2·TMTU]∞ (TMTU = tetramethylthiourea). Differences in the Te–S interatomic distances clearly indicate the C5F4N ligand being significantly more electron-withdrawing in comparison with the C6F5 group; that is, Te(C5F4N)2 is the stronger Lewis acid.

Trifluoromethylcopper and pentafluoroethylcopper are prepared conveniently via the reaction of the solid complex Zn(CF3)Br·2DMF with copper(I) bromide in N,N-dimethylformamide. The reactions of both copper species with 2,4-dinitrochlorobenzene, 4-iodonitrobenzene, 4-nitrobenzyl iodide, 4-bromobenzoic acid ethyl ester, 4-iodobenzoic acid ethyl ester, 2-iodopyridine and 2-iodopyrimidine have been studied. The structure of 2,4-dinitrotrifluoromethylbenzene has been elucidated.

[NMe4][RfTe(SC(S)NR2)2] derivatives are selectively formed by the oxidation of [NMe4]TeRf (Rf = CF3, C2F5) with [R2NC(S)S]2 (NR2 = NEt2, NBz2, N(CH2)4) in almost quantitative yields. An alternative route to obtain the dithiocarbamato complex anions offer reactions of Te[SC(S)NR2]2 (NR2 = NEt2, NBz2) with equimolar amounts of Me3SiRf and [NMe4]F. Some of the derivatives were recrystallized with bulky cations in order to determine the crystal structures. Structural elucidation by diffraction methods exhibit the structural feature of a distorted pentagonal planar environment (resembling “butterflies”) around the tellurium centres. The carbamato tellurates can be transferred easily into the neutral derivatives, RfTeSC(S)NR2, upon treatment with Ag[BF4]. In solution they equilibrate with Te2(Rf)2 and [R2NC(S)S]2 and finally are transformed into Te(Rf)2, Te[SC(S)NR2]2, and Te[SC(S)NR2]4, respectively. All compounds are fully characterized by NMR spectroscopic methods (1H, 13C, 19F, 125Te). Additionally, synthesis and characterization of the hitherto unknown derivative [NMe4]TeC2F5 are described.

Trifluoromethylketones of aromatics, heteroaromatics and olefins are formed selectively from reactions of trifluoromethylsilver and the corresponding carboxylic acid chlorides in moderate to excellent yields. The conditions chosen are dependent on the nature of the acyl chloride. Attempts to prepare alkyl(trifluoromethyl)ketones yielded product mixtures of the corresponding acyl fluorides, trifluoromethyl-, pentafluoroethyl- and n-heptafluoropropyl ketones.Trifluoromethylketones of aromatics, heteroaromatics and olefins are formed selectively from reactions of trifluoromethylsilver and the corresponding carboxylic acid chlorides in moderate to excellent yields.

A temperature range of −18 °C to room temperature was found to be effective for selective fluoride-mediated cross-coupling reactions of trimethyl(perfluoroalkyl)silanes, Me3SiCF3 and Me3SiC2F5, and alkyl halides, RX (X = Br, I) in the absence of any catalyst.CnH2n+1X1+Me3SiCF3+[Cat]F⟶−18 °C to r.t.DMECnH2n+1CF32+Me3SiF+[Cat]X, X=Br,I;   Cat=NMe4,S(NMe2)3,Cs(15-Crown-5)2;  CnH2n+1I1+Me3SiC2F5+[Cs(15-Crown-5)2]F⟶−18 °C to r.t.DMECnH2n+1C2F53+Me3SiF+[Cs(15-Crown-5)2]I.

2,3,4,5,6-Pentafluorophenones are formed selectively from the reactions of pentafluorophenylsilver and carboxylic acid chlorides in moderate to excellent yields.R = 4-NO2C6H4, 2-FC6H4, 4-FC6H4, 4-CIC6H4, 4-BrC6H4, C6F5, 2-furyl, 2-thienyl, trans-styryl, pyridine-2,6-diyl.

[NMe4]TeCF3 is obtained in 60% yield from Me3SiCF3, elemental tellurium and [NMe4]F in glyme as a pale yellow solid decomposing at 185 °C. Cation exchange with [PNP]Br ([PNP] = bis(triphenylphosphoranylidene)ammonium) and [(dibenzo-18-crown-6)K]Br occurs spontaneously. These low co-ordinating cations increase significantly the nucleophilicity of the anion.Graphic

Ligand exchange reactions of [NMe4]TeCF3 and CuBr, Ag[BF4] and AuCl have been studied in molar ratios of 2:1. While evidence is found for [Cu(TeCF3)2]− moieties by 19F-NMR spectroscopic and mass spectrometric means, [NMe4][Ag(TeCF3)2] and [NMe4][Au(TeCF3)2] were isolated. After cation exchange, the latter compounds were fully characterised as the [PNP] salts ([PNP] = bis(triphenylphosphoranylidene)ammonium). The single crystal structure of [PNP][Au(TeCF3)2] has been elucidated by XRD measurements (P21/a; a = 1765.6(1), b = 1126.0(1), c = 2055.2(1) pm; β = 111.98(1)°; Z = 4).

In(C6F5)Br2·2D (D=THF, pyridine) are selectively and almost quantitatively formed through oxidative addition of C6F5Br to InBr in THF solution or dichloromethane–pyridine mixtures. The constitution of In(C6F5)Br2·2THF is confirmed by a single crystal structure analysis (monoclinic, P21/c, Z=4, a=1694.3(2), b=1421.5(2), c=813.42(9) pm, β=100.3(1)°, Rall=0.1072). Reactions of In(C6F5)Br2·2THF and Mg(C6F5)Br in diethylether after addition of 4-dimethylaminopyridine (DMAP) yield In(C6F5)3·DMAP. In[SC(S)N(C2H5)2]3 is formed by treatment of In(C6F5)Br2·2THF with NaSC(S)N(C2H5)2 while acidic hydrolysis with aqueous HBr quantitatively gives InBr3·nH2O and C6F5H. Reactions of In(C6F5)Br2·2THF with an aqueous solution of pentane-2,4-dione (acetylacetone, Hacac) in THF quantitatively yield In(acac)Br2·2THF and C6F5H. The constitution of this compound is established by a single crystal structure analysis (orthorhombic, Pbcn, Z=4, a=1314.9(2), b=928.5(1), c=1468.4(2) pm, Rall=0.0347).The title compound is formed according to the above equation. Subsequent reactions gave compounds such as In(C6F5)3·DMAP and In(acac)Br2·2THF.

[NMe4]SCF3, CsSCF3 and [(B-15-C-5)2Cs]SCF3 (B-15-C-5: benzo-15-crown-5) are formed from reactions of the corresponding fluorides, trimethyl(trifluoromethyl)silane, Me3SiCF3, and elemental sulfur in glyme or THF. All compounds are colorless to pale ochre solids decomposing significantly above ambient temperature. Excellent agreement between experimental and theoretical vibrational frequencies, calculated at the B3PW91 level of theory, impressively confirms the salt-like nature of [NMe4]SCF3.The properties of the title compounds as nucleophilic SCF3 transfer reagents were checked with a variety of organic, organometallic and inorganic compounds.Graphic

[NMe4]SeCF3 is prepared in better than 65% yields from the reaction of [NMe4]F, red selenium and Me3SiCF3. The colorless solid decomposes at 215–217 °C and can be used as a versatile tool to prepare a variety of SeCF3 derivatives of different compositions. Colorless crystals were formed on cooling saturated MeCN solutions to −30 °C. Excellent agreement between experimental and theoretical vibrational frequencies, calculated at the B3PW91 level of theory, confirms the salt-like nature of [NMe4]SeCF3.Cation exchange of NMe4+ for P(Ph3)Me+, N(n-Bu)4+, [18-crown-6]K+ and [dibenzo-18-crown-6]K+ (A+) gave colorless or yellow crystalline materials of the general composition [A]SeCF3.Graphic

[NMe4][RfTe(SC(S)NR2)2] derivatives are selectively formed by the oxidation of [NMe4]TeRf (Rf = CF3, C2F5) with [R2NC(S)S]2 (NR2 = NEt2, NBz2, N(CH2)4) in almost quantitative yields. An alternative route to obtain the dithiocarbamato complex anions offer reactions of Te[SC(S)NR2]2 (NR2 = NEt2, NBz2) with equimolar amounts of Me3SiRf and [NMe4]F. Some of the derivatives were recrystallized with bulky cations in order to determine the crystal structures. Structural elucidation by diffraction methods exhibit the structural feature of a distorted pentagonal planar environment (resembling “butterflies”) around the tellurium centres. The carbamato tellurates can be transferred easily into the neutral derivatives, RfTeSC(S)NR2, upon treatment with Ag[BF4]. In solution they equilibrate with Te2(Rf)2 and [R2NC(S)S]2 and finally are transformed into Te(Rf)2, Te[SC(S)NR2]2, and Te[SC(S)NR2]4, respectively. All compounds are fully characterized by NMR spectroscopic methods (1H, 13C, 19F, 125Te). Additionally, synthesis and characterization of the hitherto unknown derivative [NMe4]TeC2F5 are described.