Styx code

The number (x) of such end groups (or extra B—H bonds) can be combined with the numbers (s) of Tbhb bonds and (/) of tbbb bonds, as well as the number (y) of singly bridged B—B pairs, to give the well-known styx code ... 

These constraints lead to the standard styx codes shown in Table 3.39. 

Table 3.39. Standard allowed styx codes for some boron hydrides B/(H(/ (see Fig. 3.103)...

Table 3.41. NBO/NRT descriptors for B4H10 (see Fig. 3.103(a)), showing (a) alternative styx codes (with specific bond types) and associated non-Lewis density error (b) NHO hu and percentage polarization for NBOs of the...

Non-standard styx code pentacoordinate B(5). Non-standard styx code tricoordinate B(l). ... 

As shown in Table 3.39, three standard styx codes (4120, 3211, and 2302) are possible for B5H9. Table 3.42(a) specifies representatives of each of these structures, including two distinct structures (labeled 4120 and 4120 ) corresponding to the 4120 motif. In addition, one may consider various non-standard styx motifs such as the structures labeled 4210 and 4200 in Table 3.42(a), which correspond to one or more B atoms lacking the usual tetracoordinate pattern. Table 3.42(a) summarizes the NBO pnl density errors associated with the six listed structures, showing that the 4120 structure (3.250) has the smallest pnl value and is indeed the best single NBO structure. 

What can be considered to be the best localized structural representation of B5H11 is shown in (3.253), corresponding to styx code 4112... 

The molecular structural formulas of some boranes and their styx codes are shown in Fig. 13.4.4. 

Molecular structural formulas and styx codes of some boranes. 

From the geometrical structures of cfosoboranes, s and x of the styx code are both equal to 0. Each 3c-2e BBB bond has a bond valence value of 2. Thus,... 

Using the styx code and bond valence to describe the structures of wtfo-boranes or carboranes, the bond valence b is equal to... 

Table 13.4.3 lists the styx code and bond valence of some m tfo-boranes, and Fig. 13.4.8 shows the chemical bonding in their skeletons. 

For the arachno-boranes, B H +6, the relations between styx code and n are as follows ... 

From the equations of balance it could be derived that s = (ql2)+y, which indicates that s > (q/2), as y > 0. The maximum value of x is q, which is the case when all the extra hydrogen atoms are used for 3c-2e B-H-B bond. Thus, the values of s can range from q/2 to q. In case of more than one styx codes for the same borane, that which is most symmetric and sticks to the topological rules mentioned previously is selected. 

Styx formalism can be applied to charged structures as well, by hydrogenating them to get the neutral borane and then treating each B-H-B (s) as protonated B-B(y). For example, could be treated as B5H7. The styx code could be... 

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