Hydrogen storage for transportation applications requires high volumetric and gravimetric storage capacity. B-N compounds are well suited as storage materials due to their light weight and propensity for bearing multiple protic (N-H) and hydridic (B-H) hydrogens. This critical review briefly covers the various methods of hydrogen storage, and then concentrates on chemical hydrogen storage using B-N compounds. The simplest B-N compound, ammonia borane (H3NBH3), which has a potential 19.6 wt% hydrogen storage capacity, will be emphasised (127 references).

Ammonia-borane (NH(3)BH(3), AB) has garnered interest as a hydrogen storage material due to its high weight percent hydrogen content and ease of H(2) release relative to metal hydrides. As a consequence of dehydrogenation, B-N-containing oligomeric/polymeric materials are formed. The ability to control this process and dictate the identity of the generated polymer opens up the possibility of the targeted synthesis of new materials. While precious metals have been used in this regard, the ability to construct such materials using earth-abundant metals such as Fe presents a more economical approach. Four Fe complexes containing amido and phosphine supporting ligands were synthesized, and their reactivity with AB was examined. Three-coordinate Fe(PCy(3))[N(SiMe(3))(2)](2) (1) and four-coordinate Fe(DEPE)[N(SiMe(3))(2)](2) (2) yield a mixture of (NH(2)BH(2))(n) and (NHBH)(n) products with up to 1.7 equiv of H(2) released per AB but cannot be recycled (DEPE = 1,2-bis(diethylphosphino)ethane). In contrast, Fe supported by a bidentate P-N ligand (4) can be used in a second cycle to afford a similar product mixture. Intriguingly, the symmetric analogue of 4 (Fe(N-N)(P-P), 3), only generates (NH(2)BH(2))(n) and does so in minutes at room temperature. This marked difference in reactivity may be the result of the chemistry of Fe(II) vs Fe(0).

New 1,10-phenanthroline ligands have been synthesized with C6F5- or 2,4,6-(CF3)3C6H2- groups in the 2- and 9-positions; a cationic copper(I) complex of the latter catalyses nitrene transfer to the C-H bonds of electron-rich arenes.

NotesVol. 70 enediamine |di hydrochloride was found to be 0.86 c./m./ mg. This indicates that 2.6% of the succinic acid radioactivity was in the methylene carbon atoms.Oxidation of Malic Acid.-To a solution of 109.7 mg. of C14-labeled malic acid (275 c./m./mg. or 30,100 c./m. total.) in 10 ml. of 1.0 N sulfuric acid in a 100-ml. flask equipped with nitrogen inlet bubbler, reflux condenser and dropping funnel was added 20 ml. of 0.15 M chromic acid solution during two hours on the steam-bath.The carbon dioxide evolved was collected in carbonatefree sodium hydroxide solution and precipitated with barium chloride to give 326 mg. (101%) of barium carbonate.The specific activity was found to be 81.5 c./m./mg. or 26,600 c./m. total. Acetic acid was obtained from the residual solution upon steam distillation. It was converted to barium acetate (80% yield based on titer of steam distillate) which was recrystallized from water. From the specific activity (2.0 c./m./mg.) and the theoretical yield (112 mg.), the activity in the a and /3 carbon atoms of the malic acid, 224 c./m., can be determined accurately without interference from carboxyl activity. Incomplete recovery of the carbon dioxide and overoxidation of the malic acid is assumed to have caused the loss of carboxyl activity.

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DISCLAIMERPortions of this document may be illegible in electronic image products. Images are produced from the best available original document. IntroductionIn an e a r l i e r one of us repofled obssrrations of the maxirnu.u.OH aonuentration developed at the end of t h e induction period i n the shock wave wmbuetfon of s t o i c h i m e t r i c an8 nearly s t o i c h i o w e t r i c hydrogenoxygen mfiotuma d i l u t e i n argon. A t temperatures between about 1000° and 260O0#, t h e m c o n c~t~a t f o n s ' e x c e e d their ultimate e q u i l f b r f m values by large faatorsS ernd t h i s "overshootM was accounted POP approximately by t h e notion that the aanditbons in t h e reaction mixture at t h e t i m e , of t h e OWcmcentratitm tm%fBfm 6 0 m~w n d d to a state of paaytfal equilibrium among the three independent maatPass of t h e branching chain mechanism, which was achieved promptly a t the and of the inductfon'porfod, before t h e reambfnatbon reactions had prapiasssd apgmciably. It was.suggested, Isoreover, that t h e p a r t f a l equilibrium values represented p r a c t i c a l upper limits to the martiarum e o n c e n t m t i~n s reached by O H a d the other reactionWe regam here a more thorough hvecstfgtstfon o f the course of t h e hydrogen -oxygen r e a c t i o n a t t h e end o f t h e indua. r CE-G-~-LN-O-T-I-CE----' -\ apparatus, method, or process disclosed in this report. used in tho above, "person a c m g an behalf of the C o~m i e s i a n " includes any employee o r contractor of the C6mmisslon, o r employee of such contractor, to e e extent that such employae or contractor nf lbe Commission, o r employee of such contractor prepares.dfsaeminates, o r provldes access to. any information pursualrl lo Ma employment o r contract with the Commlsslon, o r his employment "Ith such Contractor.

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