Two reliable and efficient routes to bis(pentafluorophenyl)borane, 1, are described. A three-step procedure uses the −C6F5 transfer agent Me2Sn(C6F5)2 to produce the chloroborane ClB(C6F5)2, which is subsequently converted to 1 by treatment with a silane, and proceeds with an overall yield of 62%. Alternatively, 1 can be made in 69% yield from B(C6F5)3 and Et3SiH by heating the two reagents at 60 °C for 3 days in benzene. Borane 1 is dimeric in the solid state, as determined by X-ray crystallographic analysis. However, in aromatic solvents, detectable amounts of monomeric borane are present (ratio of dimer:monomer ≈4.5:1). The ease of dimer dissociation to monomer coupled with the high electrophilicity of the borane makes 1 a very reactive hydroboration reagent in aromatic solvents. Hydroborations do not proceed in donor solvents such as tetrahydrofuran. A survey of a variety of olefin and alkyne substrates shows that 1 hydroborates with comparable regio- and chemoselectivities to commonly used reagents such as 9-BBN, but at a much faster rate. A second unique feature of the reagent is the facility with which boryl migration takes place in the products of olefin hydroboration. This property can be used to access thermodynamic products of hydroboration where other reagents give diastereomeric kinetic products. Alkynes can be selectively monohydroborated; terminal alkyne substrates will react with a second equivalent of 1, while internal alkynes are immune to further hydroboration. Two procedures for the oxidation of the products of hydroboration were developed. Since the organobis(pentafluorphenyl)boranes are susceptible to protonolyis, oxidation must be carried out in a two-phase system using highly alkaline hydrogen peroxide or with a nonaqueous procedure using Me3NO as the oxidant. Hydroboration/oxidation can be carried out rapidly in a one-pot procedure which gives alcohol or carbonyl products in good to excellent yields.

Described is a scalable procedure for driving photochemical sytheses of trans-cyclooctene derivatives through metal complexation. During photoirradiation, reaction mixtures are continuously pumped through a column of a AgNO3-impregnated silica gel. The trans-cyclooctene derivative is selectively retained by the AgNO3-impregnated silica, but the cis-isomer elutes from the column back to the reaction flask, where it is photoisomerized and recirculated through the column. The method provides access to a range of usefully functionalized derivatives of trans-cyclooctene, including a derivative of 5-aza-trans-cyclooctene that underwent transannular cyclization upon treatment with bromine. The alkene stereochemistry is transferred with high fidelity to the hexahydropyrrolizine framework in the transannular cyclization.

Reaction of {2,6-bis[2,6-(i-Pr)2PhNC(Me)]2(C5H3N)}VCl3·1.3(CH2Cl2) (1) with stoichiometric amount of methyl alumoxane (PMAO) in toluene resulted in the methylation of the pyridine ring ortho position affording {2,6-bis[2,6-(i-Pr)2PhNC(Me)]2(2-MeC5H3N)}VCl2·0.5 (toluene) (2). In the process the ligand became an anionic amide, one chlorine atom was eliminated by the metal center, and the vanadium coordination number decreased by one unit. This new trivalent compound is a potent ethylene polymerization precatalyst, and polymers produced by the complex activated with PMAO showed a bimodal character in the GPC. Its bimodality is tentatively explained with the existence of two catalytically active species (mono and dialkylation of the vanadium center). Further attack of a strong alkylating agent such as MeLi occurs at the pyridine ring to either remove the methyl group, or to place an additional methyl group on the ring meta position. Both processes imply two-electron reduction of the metal center and formation of the corresponding V(I) derivatives {2,6-bis[2,6-(i-Pr)2PhNC (Me)]2(C5H3N)}V(CH3)(μ-CH3)Li(Et2O)3 (3) and the ionic [{2,6-bis[2,6-(i-Pr)2PhNC(Me)]2 (2,3-Me2C5H3N)}V(CH3)2][Li(THF)2(TMEDA)2]·0.5(Et2O) (4) which were isolated in crystalline form. Crystal data are as follows. 1:  monoclinic, space group P2 1 /n, a = 18.267(5) Å, b = 16.643(4) Å, c = 38.195(9) Å, β = 96.061(5)°, Z = 12; 2:  monoclinic, space group P2 1 /c, a = 15.741(2) Å, b = 16.565(2) Å, c = 15.849(2) Å, β = 100.316(3)°, Z = 4; 3:  orthorhombic space group Pnma, a = 19.724(6) Å, b = 22.001(7) Å, c = 11.035(3) Å, Z = 4; 4:  monoclinic space group P2 1 /n, a = 11.932(3) Å, b = 25.363(6) Å, c = 18.957(4) Å, β = 96.587(4)°, Z = 4.