Cluster hypho

Nido-cluster (a nest) a deltahedral structure with one missing vertex. Arachno-cluster (a spider-web) a deltahedral structure with two missing vertices. Hypho-cluster (a net) a deltahedral structure with three missing vertices. 

Molecular structures of some hypho cluster systems (a) B5H9(PMe3)2 (b) (NCCH2)C3B6Hj 2 (c) [/u,2- C(CN)2 2]C2B7H12. In carboranes (b) and (c), for clarity only bridging and extra H atoms are included, and all exo H atoms attached to the vertices are omitted. 

The removal of one or more vertices from a closo polyhedral system leaves the number of skeletal bonding MOs unchanged thus, a 6-vertex closo cluster (octahedral, as in Fig. 5-5), a 5-vertex nido cluster (square pyramidal), and a 4-vertex arachno cluster (butterfly or square planar, depending on whether adjacent or nonadjacent vertices are removed from the octahedron) all have 6 bonding MOs and hence require 7 bonding electron pairs. Expressed in terms of the number of vertices n, this equals n+1, n+2, n+3, and n+4 pairs for closo, nido, arachno, and hypho clusters, respectively. 

The chemistry and formation of a variety of substitution patterns of the cluster (NHR)B8FIn(NH2R) was studied extensively in the last 10 years.83,91-94 Furthermore, the electron count was discussed hypho-nine-vertex cluster, zzrar 0-eight-vertex versus -eight-vertex cluster.95,96 The formation mechanism of this azaborane and espe-... 

Derivatives of the trishomotriborirane dianion P are formed when alkali metals react in donor solvents with 1,3,5-triboracyclohexane derivatives. The dianion [(CHMe)3(MeB)3]2 has 20 SE and according to the cluster rules classifies as 2,4,6-tricarba-hypho-hexaborane-diid. However, the compounds exist as contact ion pairs, and are therefore regarded as heterocarboranes (see Section 3.2.8). 

Insertion of a third methylene bridge into M leads to hypho P with 20 SE. The tetrameric species [Li(thp)2Li87]4 and Li([12]cr-4)2 4(Li87)4 suggest that one Li+ has to be assigned to each [(MeCH)3BMe]32 arachno cluster. The former is coordinated by two C-B bonds of the neighboring cluster [103]. This increases the total... 

A large number of borane clusters of the hypho-type are known that contain bridging groups such as CH2, NH, S, etc. Formally, these groups could be considered to... 

The hypho-electron count of the 9-vertex clusters (NHR)B8Hn(NH2R ) R/R = Et/Et, Pr /Pr1, Pr /Bu (Figure 3.4-23) and (NEt2)B8Hn(NHEt2) [295] results from... 

Closo, nido, arachno, hypho deltahedral clusters based on n main group vertex atoms are characterized by An + 2, An + 4, An + 6 and An + 8 total valence electrons respectively. The corresponding optimum VEC for closo and nido deltahedra... 

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