B Bridging

Figure 8.16 shows the B l spectmm of the B5FI9 molecule. The boron atoms are situated at the comers of a square pyramid. There are four B-FI-B bridging hydrogen atoms and... 

Rhodacarborane catalysts have been immobilized by attachment to polystyrene beads with appreciable retention of catalytic activity (227). A 13-vertex /oj iJ-hydridorhodacarborane has also been synthesized and demonstrated to possess catalytic activity similar to that of the icosahedral species (228). Ak-oxidation of closo- >(2- P((Z [) 2 - i- > l[l-Bih(Z, results in a brilliant purple dimer. This compound contains two formal Rh " centers linked by a sigma bond and a pak of Rh—H—B bridge bonds. A number of similar dimer complexes have been characterized and the mechanism of dimer formation in these rhodacarborane clusters have been studied in detail (229). 

Fig. 5.11. Contrasting potential energy diagrams for stable and unstable bridged norbomyl cation. (A) Bridged ion is a transition state for rearrangement between classical structures. (B) Bridged ion is an intermediate in rearrangement of one classical structure to the other. (C) Bridged nonclassical ion is the only stable structure.

Suggest a Lewis structure for B4H 0 and deduce the formal charges on the atoms. Hint There are four B—H—B bridges. 

Figure 5.3 Metal polyacrylate molecular structures (a) purely ionic, (b) bridging bidentate, (c) chelating bidentate, (d) asymmetric unidentate, (e) chelate bidentate.

Figure 3.46. Representation of various modes of chemisorbed CO on a metallic surface a. linear or terminal, b. bridged, c. bridged, d. valley or triple and e. dissociative adsorption.

Figure 12.3 Schematic diagram showing a cross-section through a feed hopper a) full hopperand b) bridge preventing materia feed...

Stronger distortion in compound 81 results from the formation of an electron deficient Si-H-B bridge <2003CEJ4732, 2006AOM443>. 

In each of the B-H-B bridges, only two electrons bond the three atoms together by having the orbitals on the boron atoms simultaneously overlap the hydrogen Is orbital. A bond of this type is known as a two-electron three-center bond. In terms of molecular orbitals, the bonding can be described as the combination of two boron orbitals and one hydrogen orbital to produce three molecular orbitals, of which only the one of lowest energy is populated ... 

The mechanistic implications of these facile formal cluster oxidations arachno nido closo by nett loss of Hp at moderate temperatures are considerable. The processes are accompanied by, and presumably assisted by a flexibility of coordination geometry about the Ir atom and also by its ready oxidation. The metal atom can be seen as a potential source of electrons for cluster bonding either by involving its lone pairs of electrons or by switching between Ir-H-B bridging and Ir-H terminal bonding... 

Figure 20 (a) Bridging Sej chains in [Ph4P]4[In2S27] 110 (b) bridging Te24 chains in... 

Scheme 34. Bishomotriborirane Anions with a B—H—B Bridge As Formulated in Ref 90...

You will recall that boranes are now classified into various series as summarized in Table I. The formulae and structures can be rationalized on the basis of the number of skeletal electrons available for bonding and each B atom is considered to contribute 2 electrons in addition to the one used to form a terminal B-Hj-bond. Supernumerary H atoms form B-H j-B bridges or comprise the endo-li atom in a 6H2 group they occur in the "open... 

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