Hydrogen storage: beyond conventional methods.

The efficient storage of hydrogen is one of three major hurdles towards a potential hydrogen economy. This report begins with conventional storage methods for hydrogen and broadly covers new technology, ranging from physical media involving solid adsorbents, to chemical materials including metal hydrides, ammonia borane and liquid precursors such as alcohols and formic acid.

Selective palladation of a large (32 ring atom) macrocyclic ligand at a bis(N-heterocyclic carbene) coordination pocket through transmetallation of the corresponding mercury(II) derivative.

Treatment of N(2),N(6)-bis(6-acrylamidopyridin-2-yl)pyridine-2,6-dicarboxamide with benzimidazole gives the acyclic aza-Michael addition product N(2),N(6)-bis(6-(3-(1H-benzo[d]imidazol-1-yl)propanamido)pyridin-2-yl)pyridine-2,6-dicarboxamide (2). The macrocycle N(1),N(7)-pyridine-2,6-dimethyl-N(2),N(6)-bis(6-(3-(1H-benzo[d]imidazol-1-yl)propanamido)pyridin-2-yl)pyridine-2,6-dicarboxamide dibromide ([H(2)L(2)]Br(2)) is formed through the double alkylation of 2 with 2,6-bis(bromomethyl)pyridine. The imidazole analogues of 2 and [H(2)L(2)]Br(2) (1 and [H(2)L(1)]Br(2), respectively) have also been prepared. Mercuration of the two benzimidazolium groups in [H(2)L(2)]Br(2) with mercury(II) acetate in the presence of [N(CH(3))(4)](2)[HgBr(4)] proceeds to give [HgL(2)][HgBr(4)] in good yield. The ability of [HgL(2)][HgBr(4)] to readily partake in transmetallation reactions is demonstrated by the reaction that occurs with PdCl(2)(COD) to form [PdClL(2)][PF(6)]. The structures of 2, [HgL(2)][HgBr(4)] and [PdClL(2)][PF(6)] have been determined.