• Source: Transition metal dithiocarbamate complexes

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.




Ligand characteristics



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:

R2NH + CS2 + NaOH → R2NCS2−Na+ + H2O
A wide variety of secondary amines give the corresponding dtc ligand. Popular amines include dimethylamine (Me2NH), diethylamine (Et2NH), and pyrrolidine ((CH2)4NH).

Related ligands
Dithiocarbamates are classified as derivatives of dithiocarbamic acid. Their properties as ligands resemble the conjugate bases of many related "1,1-dithioacids":

Xanthates, ROCS2−
Dithiophosphates, (RO)2PS2−
Dithiocarboxylates, RCS2−




Synthetic methods


Commonly, metal dithiocarbamates are prepared by salt metathesis reactions using alkali metal dithiocarbamates:

NiCl2 + 2 NaS2CNMe2 → Ni(S2CNMe2)2 + 2 NaCl
In some cases, the dithiocarbamate serves as a reductant, followed by its complexation.
A complementary method entails oxidative addition of thiuram disulfides to low-valent metal complexes:

Mo(CO)6 + 2 [S2CNMe2]2 → Mo(S2CNMe2)4 + 6 CO
Metal amido complexes, such as tetrakis(dimethylamido)titanium, react with carbon disulfide:

Ti(NMe2)4 + 4 CS2 → Ti(S2CNMe2)4




Homoleptic complexes



Bis complexes
nickel bis(dimethyldithiocarbamate), palladium bis(dimethyldithiocarbamate), platinum bis(dimethyldithiocarbamate), all square-planar complexes
copper bis(diethyldithiocarbamate), a square-planar complex
Tris complexes
vanadium tris(diethyldithiocarbamate), an octahedral complex
chromium tris(diethylditiocarbamate), an octahedral complex
manganese tris(dimthylthtiocarbamate), an octahedral complex
iron tris(diethyldithiocarbamate), ruthenium tris(diethyldithiocarbamate), osmium tris(diethyldithiocarbamate), all octahedral complexes
cobalt tris(diethyldithiocarbamate), rhodium tris(diethyldithiocarbamate), iridium tris(diethyldithiocarbamate), all octahedral complexes
Tetrakis complexes
titanium tetrakis(dimethyldithiocarbamate)
molybdenum tetrakis(diethyldithiocarbamate)
Dimetallic complexes
iron bis(diethyldithiocarbamate), pentacoordinate Fe dimer
zinc bis(dimethyldithiocarbamate), pentacoordinate Zn dimer
dicobalt pentakis(diethyldithiocarbamate) cation, with a pair of octahedral Co(III) centers
diruthenium pentakis(diethyldithiocarbamate) cation, with a pair of octahedral Ru(III) centers, two isomers




Reactions


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):

Fe(S2CNEt2)3 + 0.5 I2 → Fe(S2CNEt2)2I + 0.5 (S2CNEt2)2
They degrade to metal sulfides upon heating.




Applications


Dtc complexes find several applications:

herbicides in the form of the iron and zinc derivatives Ferbam and Zineb, respectively
vulcanization accelerators, zinc bis(dimethyldithiocarbamate).
medicine, iron tris(dimethyldithiocarbamate) as a nitric oxide scavenger.
lubricants. Metal thiocarbamates are also used in metal-to-metal lubrication proposes, mainly as an anti-oxidation or anti-extreme pressure (EP) additive. 1-2% of such compounds can be added to internal combustion engine lubricant to increase extreme pressure performance in high operational temperatures.




References

Kata Kunci Pencarian:

• Transition metal dithiocarbamate complexes
• Dithiocarbamate
• Sodium diethyldithiocarbamate
• Pyrrolidine dithiocarbamate
• Iron tris(dimethyldithiocarbamate)
• Nickel bis(dimethyldithiocarbamate)
• Metal sulfur dioxide complex
• Nitric oxide
• Iron tris(diethyldithiocarbamate)
• Carbon compounds