Here is a picture of an interesting molecule, methyl-imidodiphosphate. It's related to a molecule we use in the Webb lab at The University of Texas at Austin, GDPNP, and I'm using it to get molecular mechanics parameters so we can run calculations on the proteins we study, which have GDPNP bound to them. GDPNP is related to a biologically important molecule called GTP which is involved in almost every signalling process in every living cell.

Notice the two phosphorus atoms (bronze) bound to the nitrogen atom (blue)? The hydrogen (white) seems to lie almost in the same plane as the phosphoruses and the nitrogen. Naive molecular mechanics force fields (and chemical bond theories like VSEPR) can get this geometry wrong.