Homogeneous nickel catalysis is used for the synthesis of pharmaceuticals, natural products, and polymers. These reactions generally proceed via intermediates in Ni(0), Ni(I), Ni(II), and/or Ni(III) oxidation states. In contrast, Ni(IV) are rarely accessible. We report herein design, synthesis, characterization a series organometallic complexes, accessed by reaction Ni(II) precursors with widely oxidant S-(trifluoromethyl)dibenzothiophenium triflate. complexes undergo highly selective...

Silver carboxylate salts are widely used as additives in palladium-catalyzed C–H functionalization reactions. However, the role of these silver is often not fully understood. This paper describes an investigation AgOPiv stoichiometric activation C6F5H at a well-defined PdII complex well PdII-catalyzed oxidative dimerization 2-alkylthiophenes. Both situ NMR spectroscopy and H/D exchange studies reactions implicate for cleavage event, generating Ag–C6F5 intermediate. The catalytic show similar...

This communication describes the synthesis and reactivity of Ni(IV)(aryl)(CF3)2 complexes supported by trispyrazolylborate 4,4'-di-tert-butylbipyridine ligands. We demonstrate that isolable Ni(IV) can be accessed under mild conditions via oxidation Ni(II) precursors with S-(trifluoromethyl)dibenzothiophenium triflate as well diaryliodonium aryl diazonium reagents. The intermediates undergo high yielding aryl-CF3 bond-forming reductive elimination. These studies support potential viability in...

This manuscript describes the design, synthesis, characterization, and reactivity studies of organometallic NiIII complexes general structure TpNiIII(R)(R1) (Tp = tris(pyrazolyl)borate). With appropriate selection R R1 ligands, are stable at room temperature can be characterized by cyclic voltammetry, EPR spectroscopy, X-ray crystallography. Upon heating, many these compounds undergo C(sp2)–C(sp2) or C(sp3)–C(sp2) bond-forming reactions that challenging lower oxidation states nickel.

This Article describes the development of a stable NiIV complex that mediates C(sp2)–H trifluoromethylation reactions. reactivity is first demonstrated stoichiometrically and then successfully translated to NiIV-catalyzed C–H electron-rich arene heteroarene substrates. Both experimental computational mechanistic studies support radical chain pathway involving NiIV, NiIII, NiII intermediates.

This article describes an investigation of C(sp3)–O bond-forming reductive elimination reactions from PdIV complexes. Phenoxide, acetate, difluoroacetate, dimethylphosphate, tosylate, and nitrate nucleophiles are shown to participate in this reaction. In all cases, bond formation occurs with high selectivity over potentially competing C(sp2)–O coupling. Additives have a profound impact on the chemoselectivity these reactions. An excess RO– was found limit C(sp3)–C(sp2) elimination, while...

In control: A chiral phosphoric acid catalyst significantly enhances or completely overrides the inherent regioselective acetalization profiles exhibited by monosaccharide-derived 1,2-diol substrates. This study represents first example of chiral-catalyst-directed regio- and enantioselective intermolecular acetalizations, which are complementary to existing methods for substrate-controlled functionalization polyols.

This article describes a detailed comparison of the organometallic chemistry high-valent nickel and palladium model complexes supported by tris(pyrazolyl)borate cycloneophyl ligands. The accessibility MIII MIV oxidation states with each metal is investigated through electrochemical chemical MII precursors. These studies show that NiII precursor readily undergoes both one- two-electron oxidations to generate stable NiIII NiIV products. In contrast, under conditions examined, PdII analogue...

This communication describes the synthesis of an organometallic NiIV complex bearing a labile trifluoroacetate (OTFA) ligand via oxidation NiII precursor with PhI(OTFA)2. Intramolecular C(sp2)–O bond-forming reductive elimination from this is relatively slow, requiring 6 h at 70 °C to reach completion. In contrast, transmetalation TMSCF3 occurs within just 1 room temperature generate NiIV–CF3 complex. These studies show that intermolecular reactions such as can be competitive intramolecular...

Described is a systematic comparison of factors impacting the relative rates and selectivities C(sp3 )-C )-O bond-forming reactions at high-valent Ni as function oxidation state. Two complexes are compared: cationic octahedral NiIV complex ligated by tris(pyrazolyl)borate NiIII tris(pyrazolyl)methane. Key features reactivity/selectivity revealed: 1) )-C(sp2 ) reductive elimination occurs from both centers, but reacts up to 300-fold faster than , depending on reaction conditions. The...

This report describes a computational study of C(sp³)–OR bond formation from Pd^IV complexes general structure Pd^IV(CH₂CMe₂-<italic>o</italic>-C₆H₄-<italic>C</italic>,<italic>C</italic>′)(F)(OR)(bpy-<italic>N</italic>,<italic>N</italic>′) (bpy = 2,2′-bipyridine).

Die inhärente Regioselektivät der Acetalisierung Monosaccharid-abgeleiteter 1,2-Diole kann durch einen chiralen Phosphorsäurekatalysator (siehe Schema) verstärkt oder vollständig aufgehoben werden. Diese ersten katalysatorgesteuerten regio- und enantioselektiven intermolekularen Acetalisierungen ergänzen bekannte Methoden zur substratgesteuerten Funktionalisierung von Polyolen.

Abstract Described is a systematic comparison of factors impacting the relative rates and selectivities C(sp 3 )−C )−O bond‐forming reactions at high‐valent Ni as function oxidation state. Two complexes are compared: cationic octahedral IV complex ligated by tris(pyrazolyl)borate III tris(pyrazolyl)methane. Key features reactivity/selectivity revealed: 1) )−C(sp 2 ) reductive elimination occurs from both centers, but reacts up to 300‐fold faster than , depending on reaction conditions. The...

Abstract The first example of a chiral‐catalyst‐controlled regioselective acetalization C2/C3‐OH carbohydrates such as (I) and (VIII) is described.