Trick to Find STYX Number of Boranes

How to calculate STYX Number of Boranes easily?

STYX number is used to understand the types of bonds in boranes.
S = Three center-two electrons B-H-B bond
T = Closed and/or open three center-two electrons B-B-B bond
Y = Two center-two electrons B-B bond
X = Two center-two electrons B-H terminal bond
You can easily find out the STYX number of Boranes without knowing the structure by using this trick.

Step-1:
Subtract the number of B from number of H atom. The number obtained is now divided into two parts in the following way-
A. If number of B and H are even then divided into two even numbers such as 1st number must be greater than the 2nd number.
B. If no. of B and H are odd then divided into two equal parts.
C. If given Boranes are nido then do not divided and write for S, and for X write zero.
Now the two numbers obtained by the above process is write first number for S and the second number for X.
For nido Boranes, the number is for S.

Step-2:
The number of S is subtracted from the number of B. The number obtained is for T.

Step-3:
The average of given Borane is equal to the sum of the STYX number. So, the number for Y is
Y = average of Borane – sum of the numbers of S, T and X.

Examples-

1. B₅H₉
Step-1:
Value for S:
9 - 5 = 4
This Borane is NIDO so we can not divide this number.
So the number for S is 4 and for X is 0
Step-2:
Value for T:
5 - 4 = 1
Step-3:
Value for Y:
(5 + 9)/2 = S + T + Y + X = 4 + 1 + Y + 0
7 = 5 + Y
or Y = 2
so the STYX number for B₅H₉ is 4120.

2. B₄H₁₀   CSIR-NET/JRF: Dec. 2011
Value for S:
10 -4 = 6
Since this is not nido Boran and the no. of B and H are even so it is divided into two even no as 1st is greater than 2nd. So we get 4 and 2, 4 for S and 2 for X.
Value for T:
4 – 4 = 0
Value for Y:
(4 + 10)/2 = 4 + 0 + Y + 2
Y= 1
Now we have STYX no. for B₄H₁₀ is 4012.

3. B₅H₁₁
Value for S:
11 - 5 = 6
Since this is not nido Boran and the no. of B and H are odd so it is divided into two equal numbers. So we get 3 and 3, So, both S and X have the same value 3.
Value for T:
3 – 3 = 2
Value for Y:
(5 + 11)/2 = 3 + 2 + Y + 3
Y= 0
Now we have STYX no. for B₅H₁₁ is 3203.

STYX Number for Other Boranes:
B₂H₆------ 2002
B₅H₁₁------ 3203
B₆H₁₀----- 4220
B₉H₁₅-------3603
B₁₀H₁₄----- 4620

 Share