The widespread adoption of hydrogen as an energy carrier could bring significant benefits, but only if a number of currently intractable problems can be overcome. Not the least of these is the problem of storage, particularly when aimed at use onboard light-vehicles. The aim of this overview is to look in depth at a number of areas linked by the recently concluded HYDROGEN research network, representing an intentionally multi-faceted selection with the goal of advancing the field on a number of fronts simultaneously. For the general reader we provide a concise outline of the main approaches to storing hydrogen before moving on to detailed reviews of recent research in the solid chemical storage of hydrogen, and so provide an entry point for the interested reader on these diverse topics. The subjects covered include: the mechanisms of Ti catalysis in alanates; the kinetics of the borohydrides and the resulting limitations; novel transition metal catalysts for use with complex hydrides; less common borohydrides; protic-hydridic stores; metal ammines and novel approaches to nano-confined metal hydrides.
The molecular crystal [Ni(12aneS(4))](BF(4))(2) (12aneS(4) = 1,4,7,10-tetrathiacyclododecane) displays the uncommon ability to retain its crystallinity on facile reversible hydration/dehydration without requiring polymeric bonding and despite the significant structural changes required. The flexibility of the 12aneS(4) ring facilitates rearrangement of the complex in the solid state upon absorption of two equivalents of water, with the crystal structures showing a clear topotactic relationship. The well defined chromatic, structural and magnetic changes that are both highly sensitive and easily reversed makes this complex of interest as an environmentally responsive material and as a contrasting example to the commonly reported coordination polymers.
The title compound, [Ni(H(2)O)(6)][Ni(SO(4))(2)(C(10)H(24)N(4))].2H(2)O, is an unusual compound in that it is composed of a hexaaqua complex, formally a dication, and a mixed-donor complex (four N and two O atoms), formally a dianion, with substantial charge separation between the two nickel centres (6.536 A). The homoleptic dication complex consists of the weaker-field ligands, whilst the dianion retains the coordination of all the higher-field donors. Both nickel ions are located at centres of symmetry. This rare compound is placed in the context of previously reported structures which emphasizes its peculiarity.
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