The Mitsunobu reaction is a modern SN2 reaction taking advantage of phosphorous chemistry. It is a way of converting alcohols into many other functional groups. The overall reaction is as follows.
In the animations below a smaller model of both triphenylphosphine and diethylazodicarboxylate (DEAD) have been used. These molecules being trimethylphosphine and the corresponding diformyl azo compound. .
The conversion of a primary alcohol to an ester has been chosen as an example of this mechanism however many other nucleophiles can be used instead of formic acid.
'Click' the different stages of the Mitsunobu reaction to view the 3D models of each stage: