What polyatomic substances have the lowest known freezing points at standard pressure?

At standard pressure, helium never freezes, so that's clearly *the* coldest liquid—but it's also a monatomic substance.


Diatomic hydrogen freezes at 13 K.


Neon freezes at 24 K.


And then the next coldest liquid I can find documented is $\ce{OF2},$ which is liquid between 49 K and 128 K (which I only know because Robert Forward references it in the science fiction novel *Camelot 30K*).


Are there any other known compounds which have freezing/melting points between 0 K and 50 K?


