Diethylmercury

Diethylmercury is a flammable, colorless liquid, and one of the strongest known neurotoxins. This organomercury compound is described as having a slightly sweet smell, though inhaling enough fumes to notice this would be hazardous.
This chemical can cross the blood–brain barrier, causing permanent brain damage. It is, however, considerably less toxic than dimethylmercury.
Synthesis.
Diethylmercury can be obtained from the reaction between ethylmagnesium bromide and mercury(II) chloride.
Other methods are also known.