Versatile Reaction Pathways of 1,1,3,3,3-Pentafluoropropene at Rh(I) Complexes [Rh(E)(PEt3 )3 ] (E=H, GePh3 , Si(OEt)3 , F, Cl): C-F versus C-H Bond Activation Steps.

The reaction of the rhodium(I) complexes [Rh(E)(PEt3 )3 ] (E=GePh3 (1), H (6), F (7)) with 1,1,3,3,3-pentafluoropropene afforded the defluorinative germylation products Z/E-2-(triphenylgermyl)-1,3,3,3-tetrafluoropropene and the fluorido complex [Rh(F)(CF3 CHCF2 )(PEt3 )2 ] (2) together with the fluorophosphorane E-(CF3 )CH=CF(PFEt3 ). For [Rh(Si(OEt)3 )(PEt3 )3 ] (4) the coordination of the fluoroolefin was found to give [Rh{Si(OEt)3 }(CF3 CHCF2 )(PEt3 )2 ] (5). Two equivalents of complex 2 reacted further by C-F bond oxidative addition to yield [Rh(CF=CHCF3 )(PEt3 )2 (µ-F)3 Rh(CF3 CHCF2 )(PEt3 )] (9). The role of the fluorido ligand on the reactivity of complex 2 was assessed by comparison with the analogous chlorido complex. The use of complexes 1, 4 and 6 as catalysts for the derivatization of 1,1,3,3,3-pentafluoropropene provided products, which were generated by hydrodefluorination, hydrometallation and germylation reactions.

Nickel-Catalyzed Reductive C-Ge Coupling of Aryl/Alkenyl Electrophiles with Chlorogermanes.

Cross-electrophile coupling has emerged as a promising tool for molecular synthesis; however, current studies have focused mainly on forging C-C bonds. We report a cross-electrophile C-Ge coupling reaction and thereby demonstrate the possibility of constructing organogermanes from carbon electrophiles and chlorogermanes. The reaction proceeds under mild conditions and offers access to both aryl and alkenyl germanes. Electron-rich, electron-poor, and ortho-/meta-/para-substituted (hetero)aryl electrophiles, as well as cyclic and acyclic alkenyl electrophiles, were coupled. Gram-scale reaction, incorporation of the -GeR3 moiety into complex biologically active molecules, and derivatization of formed organogermanes are demonstrated.

Rhodium-Catalyzed Silylative and Germylative Cyclization with Dehydrogenation Leading to 9-Sila- and 9-Germafluorenes: A Combined Experimental and Computational Mechanistic Study.

Stoichiometric amounts of oxidants are widely used as promoters (hydrogen acceptors) in dehydrogenative silylation of C-H bonds. However, the present study demonstrates that silylative and germylative cyclization with dehydrogenation can proceed efficiently, even without hydrogen acceptors. The combination of [RhCl(cod)]2 and PPh3 was effective for both transformations, and allowed a reduction in reaction temperature compared with our previous report. Monitoring of the reactions revealed that both transformations had an induction period for the early stage, and that the rate constant of dehydrogenative germylation was greater than that of dehydrogenative silylation. Competitive reactions in the presence of 3,3-dimethyl-1-butene indicated that the ratio of dehydrogenative metalation and hydrometalation was affected by reaction temperature when a hydrosilane or hydrogermane precursor was used. Further mechanistic insights of oxidant-free dehydrogenative silylation, including the origin of these unique reactivities, were obtained by density functional theory studies.

Functionalization of Endohedral Metallofullerenes with Reactive Silicon and Germanium Compounds.

Exohedral derivatization of endohedral metallofullerenes (EMFs) has been exploited as a useful method for characterizing the structural and chemical properties of EMFs, and for functionalizing them for potential applications. The introduction of heteroatoms, such as electropositive silicon atoms, to fullerene cages is a novel functionalization method that remarkably affects the electronic characteristics of fullerenes. This review comprehensively describes the results of the reactions of monometallofullerene, dimetallofullerene, and trimetallic nitride template EMFs with disilirane, silirane, silylene, and digermirane, which afforded the corresponding silylated and germylated fullerenes. Several examples emphasize that exohedral functionalization regulates the dynamic behaviors of the encapsulated metal atoms and clusters in the fullerene cages. The electronic effects of silyl and germyl groups are represented by comparing the redox properties of silylated and germylated EMFs with those of other EMFs derivatized with carbon-atom-based functional groups.