The structure of N,NA,NB-tris(2-methoxyethyl)benzene-1,3,5-tricarboxamide consists of aryl rings self-assembled using a novel conjunction of organizational motifs into a pstack surrounded by a triple helical network of hydrogen bonds, in a manner suggestive of a new mode of organization for some columnar liquid crystals.

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The compound pictured, an arene-soluble potassium salt of a sterically demanding diazapentadienyl ligand, is accessible in two short steps from commercially available, inexpensive regents. The anion may compete with amidinate or Cp* ligands in solubilizing and controlling the environment of metal ions; it effectively engulfs the potassium ion while appearing to be merely bidentate. Only weak single η5 contacts to substituted phenyl groups link the monomers.

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BCl3 cyclizes diazadiene (2,6-Pr(i)2C6H3NCH)2 1 through a dichloroborated intermediate [(2,6-Pr(i)2C6H3NCHCl)2BCl] to give, in polar aprotic solvents, a spontaneously dehyrochlorinated C-chloro diazaborole 4. In contrast, reaction of AlCl3 with 1 forms only acyclic mono- or di-adducts 5a/b and 6. Alkali metal reductions of gave mixtures of 4 and diazaborole [(2,6-Pr(i)2C6H3NCH)2BCl] 7. Pd(0) reduction cleanly gave diazaborole 7. Reduction of 6 gave a low yield of the closed shell C-C coupled dimer 8 of the putative diazadiene radical anion 1.AlCl2 complex monomer. An alternative synthesis for diazadiene (2,6-Pr(i)2C6H4NCPh)2, 2, is reported. Reduction of 2/BCl3, in which additional phenyl groups on the diazadiene C-2 and C-3 atoms hinder the radical coupling observed in , gave predominantly diazaborole .BCl, (9a) contaminated with .BCl2, (9b) the first such stable radical diazadiene complex of boron. All compounds 2-9 were characterized by X-ray diffraction and NMR spectroscopy. Stable radical was additionally characterized by EPR spectroscopy and density functional computation.

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Reaction of (R,RЈ)-or (S,SЈ)-bis(1-phenylethyl)amine with n BuLi in hexane solution gave the chiral amide [{PhC(H)Me} 2 NLi] 1. Complex 1 crystallises with approximate D 3 symmetry as a ring trimer (1 3 ) from hexane solution, as determined by X-ray crystallography. In direct contrast to the crystal structure of the related compound dibenzylamidolithium, [{(PhCH 2 ) 2 NLi} 3 ], no significant agostic Li ؒ ؒ ؒ C(H) contacts are present in 1 3 . Solution 1 H and 7 Li NMR spectra of 1 in d 8 -toluene show the presence of two distinct aggregated species which have been assigned as a trimer and a monomer. The complex [PhCH 2 {PhC(H)Me}NLiؒTHF] 2ؒTHF, was prepared by reaction of n BuLi with (R)-N-benzyl-α-methylbenzylamine in a hexane-THF solution and has been determined by X-ray crystallography to adopt a dimeric structure (2 2 ؒ2THF) in the solid state with C 1 symmetry. As in 1 3 , no short Li ؒ ؒ ؒ C(H) contacts are present in 2 2 ؒ2THF. The lack of Li ؒ ؒ ؒ C(H) interactions in both 1 3 and 2 2 ؒ2THF suggests that the rotameric conformations adopted for the benzyl groups in the complexes are governed mainly by steric effects. Using ab initio molecular orbital calculations (HF/6-31G*), the minimum energy structure for unsolvated monomeric 1 1 was determined to be a C 2 symmetric molecule, I, where the faces of both phenyl groups are directed towards the metal, maximising the Li-aromatic π interactions. The related C 2 symmetric molecule with both methyl groups directed towards the metal is 8.68 kcal mol Ϫ1 less stable than I. Therefore, in the absence of aggregation and external solvation, significant stabilisation is achieved through Li ؒ ؒ ؒ C(H) benzyl interactions. The energy barrier to rotation for one benzyl sidearm for geometry I is 4.76 kcal mol Ϫ1 , representing a significant lifetime for this conformer.

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