Skeletal electron pairs

Polyhedral Skeletal Electron Pair Theory The Wade-Mingos Rules... 

The next important contribution in this area was made shortly thereafter by Wade [16], who recognized that this structural relationship could be related to the number of valence electrons associated with skeletal bonding in the boranes. Thus deprotonation of all of the bridging hydrogens from the related series of boranes B H 2T B iH(n 1)+4, and Bn 2H( 2)+6 gives the ions B H 2 , B H,- 4-, and B -2H 26-. All of these ions can readily be seen to have the same number of skeletal electron pairs, namely it +1, corresponding to 2it + 2 skeletal electrons. 

Balakrishnarajan and Jemmis [32, 33] have very recently extended the Wade-Mingos rules from isolated borane deltahedra to fused borane ("conjuncto ) delta -hedra. They arrive at the requirement of n I m skeletal electron pairs corresponding to 2n + 2m skeletal electrons for such fused deltahedra having n total vertices and m individual deltahedra. Note that for a single deltahedron (i.e., m = 1) the Jemmis 2n + 2m rule reduces to the Wade-Mingos 2n I 2 rule. 

The following optimum electron numbers have been defined on the basis of the so-called Polyhedral Skeletal Electron-Pair Theory (PSEPT) . 

The geometries of metal carbonyl and metallocarborane cluster compounds have been systematized recently by a set of simple rules described collectively as the polyhedral skeletal electron pair theory (153, 218, 232). This approach originated from a perceptive analogy between isostructural metal carbonyl and borane polyhedral cluster molecules (232), and its applications have been widely discussed and reviewed (147, 153, 210, 218, 233, 234, 235, 240). In this review,... 

BsC2H7 B4C2Hb(Co(T -CsHs)) BjCjHtlMnlOOy 8 Skeletal Electron Pairs... 

Of the clusters with more than six metal atoms, the structures [75] of Os2(CO)2j (757, 284) and Rh2(CO)igj2 (79) can be rationalized in terms of skeletal electron-pair counting. For the clusters with six 38), nine (57), and eleven (59) gold atoms the rules have to be modified in order to agree with the observed structures, the main assumption being that one orbital per gold atom remains empty (55). For clusters of 8 to 15 metal atoms there is no correlation between structures and electron counts yet. 

Gosed polyhedral structure with triangular faces only known only as with molecular formula (B HJ2- ( + I skeletal electron-pairs for polyhedron. 

Nest-like, nonclosed polyhedral structure molecular formula B H + 4 ( + 2) skeletal electron-pairs n vertices of the parent (n + l)-atom c/oro-polyhedron occupied. 

Polyhedral carboranes (continued) seven-vertex carboranes, 3, 58 six-vertex carboranes, 3, 56 small carborane syntheses, 3, 54 subicosahedral carborane geometrical patterns, 3, 50 subicosahedral and icosahedral, 3, 51 supraicosahedral, characteristics, 3, 96 ten-vertex carboranes, 3, 60 thirteen-vertex carboranes, 3, 100 tricarbaborane synthesis, 3, 54 twelve-vertex carboranes, 3, 98 Polyhedral skeletal electron pair theory, Ru and Os tetranuclear clusters, 6, 874-875 Poly(iV-heterocyclic carbene) ligands... 

B20H16 is composed of two polyhedra sharing four atoms. The (m + n) electron pair count is 2 + 20 = 22, which is appropriate for a closo stmcture stabilized by 22 skeletal electron pairs (16 from 16 BH groups and 6 from four B... 

A simplified model may be used to rationalize the bonding in the heteroatomic species [Zn ZnsBi4 Bi7]5. According to the electron counting theory proposed by Wade, the formation of a closo deltahedra of 12 vertices is stabilized by 13 skeletal electron pairs. The total of 26 electrons required for skeletal bonding may be considered to be provided as follows 2 from the interstitial Zn atom, (8x0 + 4x3 = 12) from the ZngBi4 icosahedral unit (each vertex atom carries an exo lone pair or bond pair), 7 from the capping Bi atoms, and 5 from... 

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