Use of crown ethers to isolate intermediates in ammonia-borane dehydrocoupling reactions.

The presence of 18-crown-6 in the Lewis acid-promoted dehydrocoupling reaction of ammonia borane permits isolation of [(THF)BH2NH3](+) and [BH2(NH3)2](+) cations. [(THF)BH2NH3](+) reacts with Lewis bases to give either boron adducts or by deprotonation at nitrogen to give borazine and ammonia-borane.

Reactivity and catalytic activity of tert-butoxy-aluminium hydride reagents.

The reactivity and catalytic activities of the tert-butoxy aluminium hydride reagents [((t)BuO)xAlH3-x] [x = 1 (1), 2 (2)] and (L)Li[((t)BuO)2AlH2] [L = THF (3), 1,4-dioxane (4)] are investigated. The structural characterisation of the novel compounds 3 and 4 shows that the nature of the hydridic species present is affected dramatically by the donor ligand coordinating the Li(+) cation. Stoichiometric reaction of 1 with pyridine gives [(1,4-H-pyrid-1-yl)4Al](-)[(pyridine)4AlH2](+) (5) while reaction with the amine-borane Me2NHBH3 in the presence of PMDETA [(Me2NCH2CH2)2NMe] affords [(PMDETA)AlH2](+)[(BH3)2NMe2](-) (6).

Stoichiometric and catalytic reactions of LiAlH4 with Me2NHBH3.

Structural and in situ NMR spectroscopic studies show that N-H deprotonation, B-N bond cleavage and B-N bond formation can occur in the stoichiometric and catalytic reactions of LiAlH4 with Me2NHBH3.

Main group pyridyl-based ligands; strategies to mixed metal complexes.

Tris-2-pyridyl ligands of the type [Y(2-py)(3)](n-) containing metallic or semi-metallic bridgehead atoms (Y) are a relatively new innovation in the area of main group coordination chemistry. This review highlights the major classes of ligands currently available, compares their coordination chemistry to their more well known non-metallic counterparts and explores the way in which they can be used to form heterometallic complexes in a targeted way.