Wade s rule

Hoffmann DK, Ruedenberg K, Verkade JG (1977) Molecuar Orbital Bonding Concepts in Polyatomic Molecules - A Novel Pictorial Approach. 33 57-96 Hogenkamp HPC, Sando GN (1974) The Enzymatic Reduction of Ribonucleotides. 20 23-58 Housecroft CE (1997) Clusters with Interstitial Atoms from the p-Block How Do Wade s Rules Handle Them 87 137-156 Huber R, see Romao MJ (1998) 90 69-96... 

The octahedron is classified into the c/o o-structure by Wade [3,4]. Closo-structures with n skeletal atoms are stable when they have 4n-i- 2 valence electrons. Wade s rules predict that the 26 (= 4 x 6 + 2) valence electrons could stabilize the regular octahedrons since n is 6 for the octahedron. This prediction is contained in our 6N + 14 (N= 2) valence electron rule. Our rule also predicts the stability of octahedral metal clusters with the other numbers (14 and 20) of valence electrons. 

In contrast to the polyhedral boranes B H +m there exist a number of neutral boron duster molecules B X (X = Cl, Br, I, NR2, R) all of them having closed deltahedral structures in spite of the fact that the number of bonding electron pairs is only n. For this reason these homonudear cluster compounds of boron are called hypercloso polyboranes. However, there also exist anions of type B X 2 which fit Wade s rules. 

Figure 4.26. Optimum values, in accordance with Wade s rules and as summarized by Miller et al. (2002), of the valence electron concentration VEC (total number of electrons divided by the cluster atom number) as a function of the number of cluster atoms for closo and nido deltahedra. On the left the values computed for the main group elements and on the right those relevant to the transition metals.

Ralph Rudolph made major contributions to our understanding of the structure and bonding of polyhedral cluster compounds and he had an abiding interest in developing a rationale which would enable the structure of individual compounds to be systematized and related to each other. He independently arrived at a method of counting skeletal electrons which is now generally referred to as Wade s Rules, and this has had a decisive influence on our general perceptions of polyhedral cluster compounds. Related to this was his preoccupation with the problem of heteroatoms such as sulfur, and the number of electrons which such atoms contribute to the heteroborane clusters. 

According to Wade s rules, one non-bonding electron pair is allocated to each metal atom in polyionic metal clusters of the p-block elements. Thus the planar five-membered M5 anions are 16-electron species comprised of two valence electrons contributed by each metal atom and the 6- charge. Since there are eight electron pairs for bonding five cluster atoms, Wade s rules predict an arachno structure ( + 3 electron pairs for n cluster atoms), i.e. a pentagonal bipyramid with two vacant sites. 

In Chapter 15 we observed that I he l electron rule was adequate For predicting stabilities of small organometallic clusters. In this chapter we have seen that Wade s rules allow us Lo make predictions about borune structures based on the number of framework electrons. These rules ulso are adequate for most curboranes. metallacar-boranes, and other heteroboranes. i1" Furthermore, organometallic clusters that are not derived from boranes can be dealt with in a similar fashion. More sophisticated extensions are required for complex larger clusters.139... 

Wacker process, 714-715 Wade s rules, 798, 805 Walden inversion, 243 Walsh diagrams, 218 Water, physical properties of. 360... 

There are exceptions to Wade s rules, even among modest-sized clusters (see Footnote 135). In some cases large transition metals cause geometrical distortion. In others, a kinetically Favored structure may not be able to rearrange to a more thermodynamically favored one. in still other instances the assumption that transition metal atoms will use twelve electrons for external ligands is not valid As with most rules, one should not expect predictions to be foolproof. 

Since these ho mo polyatomic Ziml) anions and cations are devoid of ligands, they are sometimes referred to as "naked" dusters. In general there is a good correlation between electronic structure and geometry as predicted by Wade s rules for these dusters, though some exceptions are known. Thus whereas Sn and Bi are isoelec Ironic, they have different structures, the latter violating the rules. Only a small distortion of the bismuth canon, however, would convert it to the geometry observed for the tin duster. 

Which of the follow mg do you think would be most likely in view of tsolobal considerations and Wade s rules tSee Lillie. J. L. Whitesdl. M. A. Kester. J. C. Foiling. K. Todd. L. J. Inorg. Chem. 196V.. >6. WH-W8.)... 

A Comparison of the Noble Gas Rule with Wade s Rules for High Nuclearity Metal Carbonyl Clusters... 

Historically, a scheme of skeletal electron-counting was developed to rationalize the structures of boranes and their derivatives, to which the following Wade s rules are applicable. 

For Rh, the size match with P is better and square antiprismatic cavities are seen for [Rh9(CO)2ip]2" and [Rhi0(CO)22P]3 . Both of these clusters possess 11 skeletal pairs of electrons and obey Wade s rule for nido- and c/oso-clusters, respectively. Arsenic analogues of these compounds are known. 

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