Why does silicon tetrafluoride have a higher melting point than sulfur tetrafluoride?
High symmetry molecules fit into crystal lattices especially well (higher m.p.), but are volatile for having fewer van der Waals interactions (lower b.p.).

$$\begin{array}{lrr}
\hline
\text{Compound} &amp; \text{m.p.}/\pu{°C} &amp; \text{b.p.}/\pu{°C} \\
\hline
\text{pentane} &amp; −130 &amp; 36.1 \\  
\text{isopentane} &amp; −160 &amp; 27.2 \\ 
\text{neopentane} &amp; −18 &amp; 9.5 \\
\hline
\text{octane} &amp; −57 &amp; 125 \\  
\text{2-methylheptane} &amp; −110 &amp; 117 \\  
\text{2,2,4-trimethylpentane} &amp; −107 &amp; 99 \\ 
\text{2,2,3,3-tetramethylbutane} &amp; 101 &amp; 107 \\  
\text{cubane} &amp; 131 &amp; 133 \\
  &amp; &amp; \text{(sub. at r.t.)*} \\
\hline
\text{decane} &amp; −30  &amp; 174 \\  
\text{isodecane} &amp; −75 &amp; 167 \\  
\text{adamantane} &amp; 270 &amp; \text{sub.} \\
\hline
\end{array}
$$

* sub. — sublimes; r.t. — room temperature.