Philip C. Keller

Reactions of diborane with aromatic heterocycles—21 : Reactions with nitrogen-containing heterocycles related to pyridine

Abstract The reactions of solutions of B 2 H 6 in ethers with a variety of aromatic heterocycles containing one or more six-membered rings with only one nitrogen per ring have been examined. Quinoline and isoquinoline form monoborane adducts which hydroborate in the presence of an excess of B 2 H 6 . Protonolysis gives the 1,2,3,4-tetrahydro-compounds in both cases. N -Methylquinolinium and N -methylisoquinolinium iodides both hydroborate. Hydroboration and halogen loss occur with 2-, 3- or 4-haloquinolines (chlorine or bromine). Prior to hydroboration 8-hydroxyquinoline forms a borane adduct which rapidly eliminates one equivalent of hydrogen in a probable intramolecular ring closure. Sodium 8-hydroxyquinolinate combines with B 2 H 6 in an unsymmetrical cleavage reaction to form B 2 H 7 − or BH 4 − , and the same ring closed product formed by 8-hydroxyquinoline. Phenanthridine and N -methylphenanthridinium iodide both readily undergo hydroboration. The products formed by the latter with B 2 H 6 are 5-methyl-5,6-dihydrophenanthridine-borane and an iodoborane etherate. 1,8-Naphthyridine forms a transient borane complex which rapidly undergoes hydroboration; protonolysis gives 1,2,3,4-tetrahydro-l,8-naphthyridine. 2,2′-Bipyridyl undergoes a complex reaction with one equivalent of BH 3 giving a mixture of bpy·2BH 3 and hydroborated products, but 4,4′-bipyridyl does not appear to hydroborate. 1,10- and 1,7-Phenanthroline both hydroborate giving a mixture of reduced products on protonolysis. Pyridine-borane and 2-phenylpyridine-borane both decompose in refluxing diglyme, but protonolysis gives no reduced products in either case.

THE BEHAVIOR OF RIGID AND SEMI-RIGID BIDENTATE DONOR MOLECULES TOWARD SOME SIMPLE BORON ACCEPTORS

Abstract Synthesis of a series of complexes of the type LLBX2 + BX4 − where X = F− and CI− and LL = 1,10-phenanthroline, 2,2′-bipyridine and 1,8-bis(dimethylamino)naphthalene was achieved by the direct interaction of the ligand and BX3. No reaction was observed for X = CH3. The reactions provide a direct route for the preparation of tetra-coordinate boronium cations. The boron-11 nmr and infrared spectra of these complexes confirm the ionic nature of the compounds. 2,2′-Bipyridine functions as a chelating agent rather than as a bis-monodentate donor. 1,8-Bis(dimethylamino)naphthalene is found to be able to chelate cations much larger than protons. The steric implications of donor-acceptor interactions of boron with rigid and semi-rigid chelating donor molecules are discussed.

A Diborane-Free Synthesis of μ-Dimethylaminodiborane

Abstract Treatment of K(CH3) 2NBH3 in diglyme with a threefold excess of NaBH4 and one half mole of iodine produces a solution of Na(CH3)2N(BH3)2 which may be converted to μ-(CH3)2NB2H5 by addition of another half mole of iodine.

1 H nuclear magnetic resonance study of 1,10-phenanthroline in aqueous acid. Isolation of bis(phenanthroline)–perchloric acid

The 1H n.m.r. spectrum of 1,10-phenanthroline in aqueous acid has been examined as a function of acid concentration. Changes in the spectrum are consistent with the existence of three forms of protonated phenanthroline. At the highest acid concentrations (12M-HCl), diprotonated phenathroline (phenH22+) is the dominant species. When the formal concentration of acid equals that of phenanthroline, phenanthrolinium ion (phenH+) is present and can be precipitated with perchlorate ion. Further reduction of acidity gives phen2H+, which has been isolated as a perchlorate salt.

A simple apparatus to demonstrate differing gas diffusion rates (Graham's law)

The apparatus described in this note dramatically demonstrates relative diffusion rate effects for common gases like methane and carbon dioxide.

Who does what in freshman lab? A survey

During the Spring of 1986, the authors began an evaluation of the laboratory offered with the mainstream general chemistry lecture at the University of Arizona, and as a part of the evaluation undertook a survey to gather information about comparable courses at other institutions.

Reaction of diborane with benzoxazole and its sulphur and selenium analogues. A novel rearrangement to benzoxazaboroles, benzothiazaboroles, and benzoselenazaboroles

Reaction of B2H6 with the benzo-fused heteroaromatic compounds (1a–d) produces the boroles (2a–d)via a rearrangement in which BH3 adduct formation is the first step.