In which of the following pairs, both the species are not isostructural?

1. \(\mathrm{SiCl}_4, \mathrm{PCl}_4^{+}\)
2. Diamond, silicon carbide
3. \(\mathrm{NH}_3, \mathrm{PH}_3\)
4. \(\mathrm{XeF}_4, \mathrm{XeO}_4\)
 

A compound among the following having a similar structure to graphite is:

1. B
2. B₄C
3. B₂H₆
4. BN