Edge bonds

The incidence matrix is an n A m matrix where the nodes (atoms) define the columns (n) and the edges (bonds) correspond to the rows [m). An entry obtains the value of 1 if the corresponding edge ends in this particular node (Figure 2-16),... 

Other expansion reactions between diborane and borane anions with a B—B edge bond have been reported (79), for example... 

Figure 1.19 The structure and bond angles of ethene. The plane of the atoms is perpendicular to the paper. The dashed edge bonds project behind the plane of the paper, and the solid wedge bonds project in front of the paper.

Above 1 mM, C-H activation occurs to form a chemisorbed layer of edge-bonded (2,3-i)2) hydroquinone analogous to o-benzyne organometallic compounds formed with Pt and Os clusters (2) ... 

Two types of complex are formed on reaction of benzene with Cu montmorillonite. In the Type 1 species the benzene retains Its aromaticity and is considered to be edge bonded to the Cu(II), whereas in the Type 2 complex there is an absence of aromaticity (85,86). ESR spectra of the Type 2 complex consist of a narrow peak close to the free spin g-value and this result can be explained in terras of electron donation from the organic molecule to the Cu(II), to produce a complex of Cu(I) and an organic radical cation. Similar types of reaction occur with other aromatic molecules. However with phenol and alkyl-substituted benzenes only Type 1 complexes were observed (87), although both types of complex were seen on the adsorption of arene molecules on to Cu(II) montmorillonites (88) and anisole and some related aromatic ethers on to Cu(II) hectorite... 

The average edge bond order for a particular closo species can be calculated by dividing the total number of skeletal bond pairs ( 4- 1) by the number of edges, which, for exclusively triangular-faced poly-hedra with n vertices, is (3 — 6). This leads directly to the formal boron-boron bond order for those borane anions (ITU) and... 

Skeletal (Polyhedron-Edge) Bond Orders for Anions BnHn ... 

Structure X-N8 differs from V-N8 by only one high-coordination edge bond and the presence or absence of such a bond would not affect the coordination numbers of either carbon. There is no precedent to indicate that the more desirable 55-bridge hydrogens in V-X8, as opposed to the 65-bridge hydrogens in X-N8, would constitute a sufficient... 

Sample Edge Bond Observed Pt core Random... 

The mechanisms of these reactions are not completely understood, although relief of strain undoubtedly supplies the driving force. The reactions are thermally forbidden by the orbital-symmetry rules, and the role of the catalyst is to provide low-energy pathways so that the reactions can take place. The type 1 reactions are the reverse of the catalyzed 2 + 2 ring closures discussed at 5-49, The following mechanism, in which Ag attacks one of the edge bonds, has been suggested for the conversion of 141 to 142.587... 

Simpler bicyclobutanes can also be converted to dienes, but in this case the products usually result from cleavage of the central bond and one of the edge bonds.588 For example, treatment of 144 with AgBF,t,589 (Cy Cu, 590 or [(Tr-allylJPdClJi591 gives a mixture of the... 

Exposure of the (cycloalkenyl)methyl carbamates 304 to iodosylbenzene in the presence or absence of Rh2(OAc)4 gives the tricyclic aziridines 305 (Scheme 88) (02OL2137). Reactions of 305 with nucleophiles, facilitated with tosic acid or lithium perchlorate, proceed with cleavage of the C-N edge bond and afford the tf 7 z-spirooxazolidinones 306. Intramolecular aziridination of the indolyl carbamate 307 with DAIB, on the other hand, requires Rh(II)-catalysis and leads directly to the acetoxy-substituted YDi-spirooxazolidinone 308 (Scheme 88) (02OL2137). When iodosylbenzene is used instead of DAIB and alcohols are available in the reaction medium, alkoxy-substituted syn-spirooxazolidinones 309 are obtained. Whereas the conversion of 304 to 305 appears to proceed by direct cyclization of intermediate iminoiodanes, the production of 308 from 307 was attributed to the intervention of a rhodium nitrene, which collapses to 308 through zwitterionic intermediates (02OL2137). 

A mathematical model for molecular complexity, such as the one developed by Bertz [21], has merit in helping to organize those properties which contribute to a heuristic idea of this subject. Using the language of graph theory [22] such a model will include a hierarchy of types of nodes (atoms) and of types of edges (bonds), as well as various other concepts such... 

The addition of acetic acid to [3.3.1]propellane at somewhat elevated temperatures results in approximately equal levels of central and edge bond cleavage to give... 

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