Transition metal dithiocarbamate complexes are coordination complexes containing one or more dithiocarbamate ligand, which are typically abbreviated R2dtc−. Many complexes are known. Several homoleptic derivatives have the formula M(R2dtc)n where n = 2 and 3.[1]
Dithiocarbamates are anions. Because of the pi-donor properties of the amino substituent, the two sulfur centers show enhanced basicity. This situation is represented by the zwitterionic resonance structure that depicts a positive charge on N and negative charges on both sulfurs. This N to C pi-bonding results in partial double bond character. Consequently, barriers to rotational about this bond are elevated. Another consequence of their high basicity, dithiocarbamates often stabilize complexes in uncharacteristically high oxidation state (e.g., Fe(IV), Co(IV), Ni(III), Cu(III)).
Dithiocarbamate salts are easily synthesized. Many primary and secondary amines react with carbon disulfide and sodium hydroxide to form dithiocarbamate salts:[2]
A wide variety of secondary amines give the corresponding dtc ligand. Popular amines include dimethylamine (Me2NH), diethylamine (Et2NH), and pyrrolidine ((CH2)4NH).
Dithiocarbamates are classified as derivatives of dithiocarbamic acid. Their properties as ligands resemble the conjugate bases of many related "1,1-dithioacids":
Commonly, metal dithiocarbamates are prepared by salt metathesis reactions using alkali metal dithiocarbamates:
A complementary method entails oxidative addition of thiuram disulfides to low-valent metal complexes:
Metal amido complexes, such as tetrakis(dimethylamido)titanium, react with carbon disulfide:
Dithiocarbamate complexes do not undergo characteristic reactions. They can be removed from complexes by oxidation, as illustrated by the iodination of the iron tris(diethyldithiocarbamate):
They degrade to metal sulfides upon heating.[11]
Dtc complexes find several applications: