Introduction of DMPS

DMPS is registered in Germany with the BGA (their FDA) for the treatment of mercury poisoning but is still an investigational drug in the United States.

DMPS is an acid-molecule with two free sulfhydryl groups that forms complexes with heavy metals such as zinc, copper, arsenic, mercury, cadmium, lead, silver, and tin. DMPS was developed in the 1950s in the former Soviet Union and has been used to effectively treat metal intoxication since the 1960s there. It is a water-soluble complexing agent.

Although it had potential use as an antidote for the chemical warfare agent, Lewisite, it was not available outside of the Soviet Union until 1978, at which time Heyl, a small pharmaceutical company in Berlin, Germany started to produce it. It has an abundance of international research data and an excellent safety record in removing mercury from the body and has been used safely in Europe as Dimaval for many years.

Source : Mercury Toxicity and Systemic Elimination Agents

1. What is the coordination number of complex formed with DMPS bond with Mercury?

Coordination number is the number of donor atom surrounding the central metal atom in a complex ion.

In the figure below, the 4 sulphur atom donate 4 atom to Mercury atom, the central metal atom.

Hence, the coordination number for Hg2+ DMPS complex is 4.

2. Can you predict the complex's geometrical shape?

There are 4 possible geometrical shape of Hg2 DMPS complexes:

1.cis-Hg DMPS complexes

2. trans-Hg DMPS complexes



3. bis- Hg DMPS complexes


4. tetrakis-Hg DMPS complex

Shape 1 and 2 shows two of the four possible isomers for linear Hg coordination, shape 3 shows the true double chelate (one Hg, two DMPS), and shape 4 shows the 4:1 complex.

From the 4 possible geometrical shape of Hg2+ DMPS complexes, the exact geometrical shape of Hg2+ DMPS complexes is the bis-Hg2+ DMPS complex. This is because it is a very stable form than the 3 other possible geometrical shapes. The bond bind more stronger and makes it not easily to react with the other substances.

Besides that, the coordination number of a metal ion is often influenced by the relative sizes of the metal ion and the surrounding ligands. As the ligands gets larger, fewer ligands can coordinate to the metal ions. Hence, the geometrical shape of shape 4 is not present.

Four coordinate complexes shown above have common geometries - tetrahedral and square planar. According to figure above, the complex's geometrical shape is square planar because square planar is for transition metal ions while tetrahedral is mostly for nontransition metal. Since Hg is a transition metal, therefore the most accurate geometry is square planar.

Below is a video about predicting Molecular and Electronic Geometries using VSEPR model. Please do watch for more understanding.

3. What is the systemic name of DMPS?

The systemic name of DMPS is 2,3-Dimercapto-1-propanesulfonate (Dimaval)

4. Give the systemic name for the complex when DMPS bond with Mercury?

When DMPS bond with Mercury, the Hg2+ complex is formed and the structure formula is as follow:


Rules of nomenclature for coordination compound ( complex ion) :

1. Within a complex ion, the ligands are named before the metal. Ligands are listed in alphabetical order, regardless of charge on the ligand. Prefixes that give the number of ligands are not considered part of the ligand name in determining the alphabetical order.

2. Greek prefixed (di-, tri-,tetra-,penta-, and hexa-,) are used to indicate the number of each kind of ligand when more than one is present. If the ligand itself contains a prefix of its kind, or is a polydentate, alternative prefixes are used instead such as bis-, tris- , tetrakis-, pentakis-, and hexakis-.

3. Thus, in the [HgC3H6O3S3)2]4+ ion, we name the 2,3- Dimercapto-1-propanesulfonate ligands first, then the mercury. Hence, the systemic name for the complex is bis-(2,3-Dimercaptop-1-propanesulfonate)Mercury (IV).