Background: $\ce{OsO4}$ is a widely used staining agent used in transmission electron microscopy (TEM) to provide contrast to the image. In the staining of the plasma membrane, osmium(VIII) oxide binds phospholipid head regions, thus creating contrast with the neighbouring protoplasm (cytoplasm).The osmium tetroxide molecule is tetrahedral and therefore non-polar. This nonpolarity helps $\ce{OsO4}$ penetrate charged cell membranes.
Question:
What would be the product formed by reaction of $\ce{OsO4}$ with polar head of phospholipid of cell membrane?
My attempt , since $\ce{OsO4}$ is non-polar and phospholipid is polar, therefore it must be some sort of covalent interaction, I couldn't find any literature regarding further at wikipedia.