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The structure of the long-known protonated iron(II) bis(dicarbollide) assigned to a staggered isomer with a cisoid conformation of the carborane ligands is studied. It is suggested that suitable control of protonation/deprotonation equilibria can induce rotary motion at the molecular level.

The gas-phase structure of 6,9-CS[B.sub.8][H.sub.12] and 6,9-CN[B.sub.8][H.sub.13] were configured by electron diffraction and ab initio calculations. Results show that the position of the sulfur atom is very close to that of the boron atom occupying the equivalent position in the parent molecule [[B.sub.10][H.sub.14].sup.2-]], reflecting the similarity of sizes of sulfur and boron atoms.

The syntheses, properties, and synthetic applications of 13-vertex closo- and nido-carboranes are reported in detail. The results show that the capitation reactions of CAd 12-vertex nido-carborane dianionic salts with dihaloboranes are generally a good method for the preparation of 13-vertex carboranes.

Selective deboronation of the B6 vertex could be achieved by functionalizing the B3 vertex and the study conducted shows that same results are achieved by sterically masking the B3 vertex from the nucleophile. The compounds provide useful symmetrical intermediates for use as carboracycle and supramolecular precursors.

Density functional theory (DFT) at the hybrid B3LYP level is applied to the polyhedral boranes BnH(sub n)(super z) (n=8 and 11, z=-2, -4, and -6) for comparison with isoelectronic germanium clusters Ge(sub n)(super z). The energy differences between the global minima and other higher energy borane structures are much larger relative to the case of the corresponding bare germanium clusters.

Immense efforts are made to develop various criteria of aromaticity and these criteria are used not only to explain the available experimental observations but also to design novel aromatics. Extending the aromaticity concept from the classical two dimensional annulenes to spherical species opens a new exciting research area with particular emphasis on fullerenes and closo-boranes.

The incorporation of multiple p-carborane cages within an aliphatic polyester dendrimer was accomplished through the preparation of a bifuntional carborane synthon. A p-carbonate derivative having an acid and protected alcohol functionality was found to efficiently couple to peripheral hydroxyl groups of low-generation dendrimers under standard esterification conditions.

Using ab initio calculations at the MP2/6-311++g* level, gas phase reactions of silane (SiH4) and diborane (B2H6) were investigated. Under thermal activation, the two molecules could overcome an energy barrier of 33.87 Kcal/mol to associate into a complex SiH4-BH3-BH3 with a hydrogen-bridged Si-H-B bond.

The syntheses and structural characterization of a wide variety of new types of metallaphosphamonocarbaborane complexes formally derived from anions in which metals adopt an unprecedented array of coordination geometrics is described. The 10 vertex phosphamonocarbaborane anions are unique in their abilities to stabilize transition metals in a variety of environments because of their unusual range of readily accessible formal charges and coordination geometrics.

The titanium-catalyzed hydroboration reactions of decaborane are carried out with variety of terminal olefins. The composition of all products was established by elemental analysis and exact mass determinations.

The Bcl-X(sub L)/BH3 domain interactions are considered to explore the possibility that unnatural oligomers with discrete folding properties might provide a general basis for development of molecules that block protein-protein interactions. The path from beta-to alpha/beta- to (alpha/beta+alpha)- peptide ligands leads to conclude that foldamer-based strategies for disrupting protein-protein interactions would grow in efficacy as number of foldamer scaffolds with distinct shapes is increased.

A versatile new method for the preparation of NHC boranes starting from two stable, readily available reactants, a heterocyclic salt and an amine or phosphine-borane, is reported. The method uses a Lewis base exchange at boron and provides easy access to new NHC boranes, in particular B-substituted borane ones.

A study was conducted to gain insight into variety of insertion reactions on treatment of Piers' borane, HB[([C.sub.6][F.sub.5]).sub.2] with either tert-butyl or isopropyl carbodiimide which yield the boron amidinates HC[(RN).sub.2]B[([C.sub.6][F.sub.5]).sub.2] [where R = iPr, tBu]. The data obtained for the isolated product of thermolysis of iPr species provide further support for the concept of existence of the transient 'open-chain' form of these amidinates in solution.

Brookhart's Ir(III) pincer complex Ir[H.sub.2]POCOP is used as catalyst to perform the catalytic dehydrocoupling/dehydrogenation of N-methylamine-borane, MeN[H.sub.2]*B[H.sub.3] and synthesize high molecular weight poly(N-methylaminoborane) [[MeNH-B[H.sub.2]].sub.n] ([M.sub.W] > 20 000). The synthetic strategy could be applied to obtain broad range of amine-borane precursors by using variety of catalysts to prepare polyaminoboranes and could find potential use for development of new class of inorganic polymers.

Aldehyde allylboration reactions of the double-chiral allylborane reagent was used to perform a highly enantioselective synthesis of (E)-[delta]-stannyl homoallylic alcohols. The reaction process involved generation of allylborane from the hydroboration of commercially available allenylstannane with [([super d]Ipc).sub.2]BH at -40 to -20 degree [Celsius] followed by a kinetically controlled and highly diastereoselective 1,3-boratropic shift in intermediate.

The dehydrogenative B-N covalent bond formation to produce aminoborane dimers through the photoirradiation of a solution of B[H.sub.3]*NH[R.sub.2] containing a catalytic amount of a group-6 metal carbonyl complex is described. The catalytic dehydrogenation reaction is observed to proceed via an intramolecular pathway in the presence of active catalyst [Cr[(CO).sub.4]].

The nature of a nanophase ammonia borane (AB) is examined by using atomic pair distribution function (PDF) analysis of synchrotron X-ray powder diffraction data to follow the structural evolution of AB embedded within MCM-41 at various temperatures. PDF analyses of composite materials composed of excess AB has shown that the excess AB has formed aggregates outside the mesoporous scaffold and that these aggregates have structural properties similar to neat AB.

The spectroscopic and crystallographic structural studies of the expected borane dithiocarbonate product and unexpected borane xanthate product isolated from the reduction of xanthates by N-heterocyclic carbene boranes (NHC-boranes) which occur via a radical chain mechanism involving unknown NHC-boryl radicals are reported. The ring opening of a substituted cyclobutylcarbinyl radical as a clock reaction provides insight into the first rate constants for H-atom transfer from an NHC borane complex and the B-H bond dissociation energy of the NHC-borane complex.

Borane-mediated reduction of aryl and alkyl ketones with [alpha]-aryl- and [alpha]-pyridyloxy groups has produced [beta]-hydroxy ethers in high enantiomeric purity by using catalyst spiroborate ester derived from (S)-diphenylprolinol. [beta]-Hydroxy ethers are converted to [beta]-amino ethers by phthalimide substitution under MitsunobuEs condition followed by hydrazinolysis to obtain primary amino ethers or by imide reduction with borane to produce [beta]-2,3-dihydro-1H-isoindol ethers.

A scale-up of diazaindoline is achieved in four stages and the key step has involved rapid reductive amination aldehyde with aniline by sodium triacetoxyborohydride (STAB-H) and TFA followed by ring closure of intermediate amine to diazaindoline in the same place. These reaction conditions are applied for facile reductive aminations with anilines and the spectra data have shown the tris(trifluoroacetoxy)borohydride anion as the active reducing agent.

The facile synthesis of the metallaheteroborane [8,8-[([PPh.sub.3]).sub.2]-nido-8,7-RhS[B.sub.9][H.sub.10]] is used for studying its reactivity. The reactivity of 11-vertex nido- and closo-rhodathiaboranes with alkenes and [H.sub.2] has disclosed new mechanisms for hydrogenation of olefins and activation of [H.sub.2] where the flexible structure of the metallaheteroborane cluster fully participates in the reactions.

The catalytically active species formed in the reaction of the first row transition metal ions such as [Co.sup.2+], [Ni.sup.2+], and [Cu.sup.2+] with ammonia-borane hydrolyze ammonia-borane to generate hydrogen are described. The results obtained demonstrated the deployment of stable first row transition metal catalysts for the generation of [H.sub.2] from AB via hydrolysis.

The structure of (tBuPOCOP)Ir[H.sub.2](B[H.sub.3]) determined from neutron diffraction data has a B-H [sigma]-bond to iridium with an elongated B-H bond distance of 1.45(5) Angstrom. The structure of borane complex is determined by X-ray diffraction and consists of the (tBuPOCOP)Ir core with a [sigma]-bound pinacol borane ligand in an approximately square planar complex.

The studies of the complexes of N-heterocyclic carbenes and borane which have weak B-H bonds due to [pi]-conjugation and hence better hydrogen donors than amine and phosphine boranes are reported. The results showed that the B-H bond and the steric environment about the B-H bond could be enhanced by changing the N-heterocyclic carbene (NHC) ligand and the borane substituents.

A comparative study of the energetics of decomposition and ionic photofragmentation of several isomeric closo-carboranes is presented. The compounds are found to favor the lower energy decomposition processes.

The development of several mild and convenient methods for the in situ synthesis of various aliphatic aminoboranes in solution is reported. The report indicates that pyrazole-derived aminoborane forms a six-membered dimer through boron-nitrogen coordination, while pyrrolylborane forms a dimer through boron-hydrogen coordination.

The isolation of the first neutral representative of the azatricarbaborane series, 7-t-Bu-arachno-7,1,5,12-N[C.sub.3][B.sub.8][H.sub.12], and the formation of the first two parent members of the 10-vertex nido family of tricarbaboranes, -[[5,6,9-[C.sub.3][B.sub.7][H.sub.10]].sup.-] and -5,6,9-[C.sub.3][B.sub.7][H.sub.11], are described. The last two compounds are shown to be the first parent members of the 10-vertex nido family of tricarbaboranes.

The square-planar rhodium(I) complexes are used for controlling the reactivity of the new organometallic/thiaborane salts. The square-planar nbd-Rh(I) reagents have yielded faster reactions and higher selectivities than their cod-Rh congenes, which is a consequence of the higher kinetic lability of the kinetic ligand and its faster hydrogenation relative to the cod diene.

Methylpentanediolborane (MPBH) can be prepared easily by reaction of hexyleneglycol with B[H.sub.3]/DMS or [B.sub.2][H.sub.6] generated from NaB[H.sub.4] and [I.sub.2]. MPBH compares favorably with pinacolborane in terms of reactivity.

A simple and highly efficient synthetic method is described for the preparation of C-hydroxy-carboranes and C,C'-dihydroxycarboranes through a one-pot procedure which involves the reaction of carboranyl lithium and trimethylborate, followed by oxidation with hydrogen peroxide in the presence of acetic acid. The method afforded excellent yield for C-hydroxy-carboranes and C,C'-dihydroxycarboranes except for dihydroxy-o-carborane.

The facile heterolytic cleavage of [H.sub.2] can be achieved at room temperature by the cooperative action of Lewis acidic boranes and Lewis basic phosphines. The steric congestion has precluded quenching of the acid and base via adduct formation, allowing consecutive reactions of the Lewis acidic and Lewis basic centers with [H.sub.2].

The examples of active first row transition metal catalysts for the dehydrogenation of the adduct ammonia-borane ([H.sub.3]NB[H.sub.3], AB), which is considered to be a promising chemical hydrogen storage material, are presented. The Ni-N-heterocyclic carbene (NHC) system has displayed an unprecedented extent of dehydrogenation to a soluble cross-linked borazine structure.

Protonation of oxazaborolidine with triflic acid generates a chiral oxazaborolidinium cation, which is found to be an extraordinarily useful broad-spectrum catalyst for numerous Diels-Alder reactions. The reaction is applied to the synthesis of several complex molecules as oxazaborolidine is a weak base, whose protonation could only be achieved by using a very strong acid.