View source for Zinc dithiophosphate

[[Image:Zn(dtp)2.png|thumb|right|250px|Structure of a monomeric zinc dialkyldithiophosphate]]
'''Zinc dialkyldithiophosphates''' (often referred to as ZDDP) are a family of [[coordination compound]]s that feature [[zinc]] bound to the anion of dithiophosphoric acid.   These uncharged compounds are not salts.  They are soluble in nonpolar solvents, and the longer chain derivatives easily dissolve in [[mineral oil|mineral]] and [[synthetic oil]]s used as [[lubricant]]s. They come under [[CAS number]] {{CASREF|CAS=68649-42-3}}. In aftermarket oil additives, the percentage of ZDDP ranges approximately between 2-15%<!-- check this value? -->.<ref>Allyson M. Barnes, Keith D. Bartle and Vincent R. A. Thibo “A review of zinc dialkyldithiophosphates (ZDDPS): characterisation and role in the lubricating oil” Tribology International 2001, Pages 389-395. {{DOI|10.1016/S0301-679X(01)00028-7}}.</ref>

The alkyl groups can be branched and linear alkanes between 1-14 carbons length, 2-butyl, pentyl, hexyl, 1,3-dimethylbutyl, heptyl, octyl, isooctyl (2-ethylhexyl), 6-methylheptyl, 1-methylpropyl, dodecylphenyl, and others.  A mix of zinc dialkyl(C3-C6)dithiophosphates come under CAS number {{CASREF|CAS=84605-29-8}}. List of other examples with their CAS numbers is [http://apps.kemi.se/flodessok/floden/kemamne_eng/zinkdialkyl_eng.htm here].

==Coordination chemistry==
These species are produced in a two steps.  First [[phosphorus pentasulfide]] is treated with suitable [[alcohol]]s to give the dithiophosphoric acid. A wide variety of alcohols can be employed, which allows the lipophilicity of the final zinc product to be fine-tuned.  The resulting dithiophosphate is then neutralized by adding [[zinc oxide]]:
:2 (RO)<sub>2</sub>PS<sub>2</sub>H  +  ZnO   →  Zn[(S<sub>2</sub>P(OR)<sub>2</sub>]<sub>2</sub>  +  H<sub>2</sub>O

In Zn[(S<sub>2</sub>P(OR)<sub>2</sub>]<sub>2</sub>, the zinc is tetrahedral.  This monomeric compound also exists in equilibrium with dimers and [[oligomer]]s caused by opening of the four-membered ZnS<sub>2</sub>P ring.  Partial hydrolysis gives the cluster Zn<sub>4</sub>O[(S<sub>2</sub>P(OR)<sub>2</sub>]<sub>6</sub>, which adopts the structure seen for [[zinc acetate|basic zinc acetate]].

Zinc diethyldithiophosphate, Zn[(S<sub>2</sub>P(OEt)<sub>2</sub>]<sub>2</sub>, is a polymeric solid, consisting of infinite linear chains.<ref>{{ cite journal | journal = Acta Cryst. | year = 1969 | volume = B25 | pages = 2303–2309 | title = The crystal structure of metal diethyldithiophosphates. I. Zinc diethyldithiophosphate | author = T. Ito, T. Igarashi, H. Hagihara | doi = 10.1107/S0567740869005619 }}</ref>

:[[File:Zinc-diethyldithiophosphate-chain-from-xtal-3D-balls.png|400px|Ball-and-stick model of part of a chain in the crystal structure of zinc diethyldithiophosphate]]

==Applications==
The main use of ZDDP is in [[AW additive|anti-wear additives]] to [[lubricant]]s such as [[grease (lubricant)|grease]]s, [[gear oil]]s, and [[motor oil]]s, which contain about 1%.  For applications in oils for gasoline engines, zinc and phosphorus emissions could damage [[catalytic converter]]s and have had their quantity reduced in standard formulations.<ref>{{cite web|title=ZDDP Engine Oil - The Zinc Factor|url=http://www.mustangmonthly.com/techarticles/mump_0907_zddp_zinc_additive_engine_oil/index.html|publisher=Mustang Monthly|accessdate=2009-09-19}}</ref> Aftermarket additives are available.
The same compounds serve also as [[corrosion inhibitor]]s and [[antioxidant]]s.

==Naming==
These compounds are widely used and correspondingly have numerous names, including ZDDP, ZnDTP, and ZDP.

==References==
<references/>

==External links==
* {{HPD|1236}}
* [http://www.baileycar.com/oil_additives_html.htm Oil additives]

[[Category:Zinc compounds]]
[[Category:Sulfur compounds]]
[[Category:Organophosphates]]
[[Category:Lubricants]]
[[Category:Corrosion inhibitors]]

[[nl:Zinkdithiofosfaten]]
[[Category:2Fix]]