Thermal Decomposition of Fluoroalkyl Pentacarbonylmanganese(I) Derivatives by α-Fluorine Elimination

Fluoroalkyl Pentacarbonylmanganese(I) Complexes as Initiators for the Radical (co)Polymerization of Fluoromonomers

The use of [Mn(RF)(CO)5] (RF = CF3, CHF2, CH2CF3, COCF2CH3) to initiate the radical polymerization of vinylidene fluoride (F2C=CH2, VDF) and the radical alternating copolymerization of vinyl acetate (CH2=CHOOCCH3, VAc) with tert-butyl 2-(trifluoromethyl)acrylate (MAF-TBE) by generating primary RF• radicals is presented. Three different initiating methods with [Mn(CF3)(CO)5] (thermal at ca. 100 °C, visible light and UV irradiations) are described and compared. Fair (60%) to satisfactory (74%) polyvinylidene fluoride (PVDF) yields were obtained from the visible light and UV activations, respectively. Molar masses of PVDF reaching 53,000 g·mol-1 were produced from the visible light initiation after 4 h. However, the use of [Mn(CHF2)(CO)5] and [Mn(CH2CF3)(CO)5] as radical initiators produced PVDF in a very low yield (0 to 7%) by both thermal and photochemical initiations, while [Mn(COCF2CH3)(CO)5] led to the formation of PVDF in a moderate yield (7% to 23%). Nevertheless, complexes [Mn(CH2CF3)(CO)5] and [Mn(COCHF2)(CO)5] efficiently initiated the alternating VAc/MAF-TBE copolymerization. All synthesized polymers were characterized by 1H and 19F NMR spectroscopy, which proves the formation of the expected PVDF or poly(VAc-alt-MAF-TBE) and showing the chaining defects and the end-groups in the case of PVDF. The kinetics of VDF homopolymerization showed a linear ln[M]0/[M] versus time relationship, but a decrease of molar masses vs. VDF conversion was noted in all cases, which shows the absence of control. These PVDFs were rather thermally stable in air (up to 410 °C), especially for those having the highest molar masses. The melting points ranged from 164 to 175 °C while the degree of crystallinity varied from 44% to 53%.

Nickel-Catalyzed Reductive Coupling for Transforming Unactivated Aryl Electrophiles into β-Fluoroethylarenes

We report herein a facile synthetic method for converting unactivated (hetero)aryl electrophiles into β-fluoroethylated (hetero)arenes via nickel-catalyzed reductive cross-couplings. This coupling reaction features the involvement of FCH₂ CH₂ radical intermediate rather than β-fluoroethyl manganese species which provides effective solutions to the problematic β-fluoride side eliminations. The practical value of this protocol is further demonstrated by the late-stage modification of several complex ArCl or ArOH-derived bioactive molecules.

Crystal structure of penta-carbon-yl(2,2-di-fluoro-propane-thio-ato-κS)manganese(I)

The synthesis and crystal structure of an unexpected CH₃CF₂C(O)SMn(CO)₅ compound are described.

The title compound, [Mn{SC(O)CF₂CH₃}(CO)₅], has been isolated as a by-product during the reaction of K[Mn(CO)₅] with CH₃CF₂COCl. It is built up from a di­fluoro­methyl­propane­thio­ate bonded to an Mn(CO)₅ moiety through the S atom. The Mn atom has an almost perfect octa­hedral coordination sphere. It is one of the rare examples of compounds containing the (CO)₅MnS—C fragment. In the crystal, the methyl group occupies a pocket surrounded by the O atoms of three carbonyl groups of the Mn(CO)₅ moiety; however, the H⋯O distances are rather long. These inter­actions lead to the formation of layers lying parallel to (101), which enclose R₄⁴(15) and R₄⁴(16) ring motifs. The CF₂ group is disordered over two sets of sites with occupancies of 0.849 (3) and 0.151 (3).