Compounds with Composition

The bicyclic molecule (2) has unexpectedly been produced from the reaction of 1,2-di-tbutyl-l,2-dichlorodiborane(4) and 3,3-dimethylallenyllithium (2) has been characterised by X-ray difhTu tion. Above 20 C, (2) rearranges to the nido-carbaborane (3). 

A series of l,2,3-ms(diisopropylamino)triborolanes has been reported One compound, (4), has been derived from 2,5-norbomadiene. This is relatively unstable and gives closo-C2H2B3 N(CHMe2)2 3. the stracture of which has been established pertinent distances are B-N = 1.379 (6) A and equatorial B-B = 1.965 (8) A. The B-B separations are quite long and this feature leads to an ambiguity in the bonding description is the compound a bicyclic system or a carbaboiane cluster  

A series of n(do-2,3,4,5-tetracarbaboranes has been prepared via the rearrangement (at temperatures between -30 C to +25 C) of tlie cyclic system (3), the preparation of which has been reported. The carbaborane cages have been characterised by multinuclear NMR spectroscopy and a discussion regarding the specific arrangement of the substituents in the cages is presented.  

A new type of linked metallacarbaborane has been established CH2(c/o5o-1-(T -CsH4) Co-2,3-Et2C2B4H4)2. The compound has been synthesised by the reaction of [nido-2,3-Et2C2B4H5]- with C0CI2 and [CH2(C5H4)2]2- and has been structurally characterised. 

The fluoride catalysed C-Si cleavage of compound (6) allows access to (7) which may then be used as a precursor for a variety of functionalised molecules via the reaction of (7) with BuLi and RX or R X ( R and R a alkyl and aryl groups). 17 

Treatment of Na+(THF)Li+[2,3-(SiMe3)2-C2B4H4]2- with Me2CHInl2 in THF leads to a dimeric complex (39% yield) which has been structurally characterised. The C2B4-cage of the precursor is capped by an InCHMe2-unit to give a c/oso-species. As anticipated, the In atom is 

Theoretical studies (MNDO-SCF) of commo-silicarbaboranes including commo- A -Si( 1,2,3-SiC2B4H6)2 have been carried out. The stabilities and structures of the commo-clusters are discussed in terms of the interactions of the silicon atomic orbitals with molecular orbitals of ic-symmctry of the open face of the carbaborane.25 

---

Uranium dioxide, UQ2, can be further oxidized to give a nonstoichiometric compound U024v, where 0 < x < 0.25. See Exercise 5.77 for a description of nonstoichiometric compounds, (a) What is the average oxidation state of uranium in a compound with composition UO,j-> (b) If we assume that the uranium exists in either the +4 or the +5 oxidation state, what is the fraction of uranium ions in each ... 

The carbides and nitrides of the elements Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Th, and U are considered to be typical interstitial compounds. Their compositions frequently correspond to one of the approximate formulas M2X or MX. As a rule, they are nonstoichiometric compounds with compositions ranging within certain limits. This fact, the limitation to a... 

Poly(carbon monofluoride) is a white compound, often reported to be explosive and unstable but found in our research results to be stable in air at temperatures up to at least 600°C. In fact, poly(carbon monofluoride) is the most thermally stable fluoropolymer known. It decomposes upon heating at 800°C or under a high vacuum at 580°C to form a series of polyolefinic fluorocarbons. 19 The compounds with compositions in the range of CFo s to CFos are nearly black. The CFos to CF0.95 compounds become gray and the CF095 to CFuj... 

It is of interest to compare this figure with the heat of immersion of aluminum-rich faujasite. For a compound with composition NaggAlggSij 20384 one calculates -122.5 kJ/mol (4), which is mainly hydration energy of intra-channel sodium ions. 

Solid-state centered-Zr cluster compounds with compositions MI1[Zr6(Z)Cli2]Cl are known. For n < 6 the structures exhibit inter-cluster bridging by shared Cl atoms... 

The appearance of the emission spectrum of UFs, which is isoelectronic with the UOg group, is strikingly different from the emission spectrum of compounds with compositions A2BWO6—U. The emission spectrum of 5% UFg/WFs crystals at 1.6K is quite complicated. The appearance of progression in the internal mode of the... 

Almost three-quarters of a century later, this substance was rediscovered by Mock and coworkers [26], With the help of modem instruments they finally characterized it as a hexameric macropolycyclic compound with composition of C36H36N24O12. The X-ray crystal stmcture (Figure 10) of this compound [26] reveals an internal cavity of 5.5 A diameter which is accessible from the exterior by two carbonyl-laced portals of 4A diameter. The cavity of cucurbituril has dimensions equivalent to that of a-CD ( 5.7A). Similar to cyclodextrins the interior of cucurbituril is hydrophobic and therefore, provides a potential site for inclusion of hydrocarbon molecules. Mock et al. proposed a trivial name cucurbituril for this compound because of its resemblance to a pumpkin which belongs to the botanical family Cucurbitaceae. 

Copper(I) thiolate complexes show remarkable diversity of structure, and the most common structural unit in the known thiolate is a three-coordinate copper atom bonded to /u.2-bridging thiolates (15). Parish has recently reported a novel compound in which the thiolate sulfur atom involves unusual four-way bridging (255). The compound with composition [Cui3C1i3(SR)8] H20 (R = CH2CH2NH3) was obtained by reaction of CuCl and cysteamine hydrochloride in an aqueous solu-... 

The moisture-sensitive compounds are made from sodium azide and the respective chlorides at moderate or low temperatures and are obtained as oily liquids of extreme sensitivity. Examples are, triphosphonitrile azide (a), cyanogen azide (b), and chromyl azide (c). Saltlike compounds with composite cations, such as ammonium and hydrazine azides, are not considered hetero azides, but normal azides. 

One might say that chemistry rules the first category and physics the second. We say this because cluster compounds are just that, true compounds, with composition and size determined by the chemical reactivities and propensities of the constituent atoms. On the other hand, if the nanoparticles of the second category are to be viewed as molecular analogues, the first requirement is near stoichiometry, which is achieved by the narrow distributions of sizes. This in turn is achieved physically by one of three methods ... 

Let us assume a compound with composition CcMn A A a where ... 

---