Palladium dicyanide
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IUPAC name
Palladium(2+) dicyanide
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Identifiers | |
3D model (
JSmol ) |
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ChemSpider | |
ECHA InfoCard
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100.016.364 |
PubChem CID
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CompTox Dashboard (EPA)
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Properties | |
Pd(CN)2 | |
Molar mass | 158.455 g/mol |
Appearance | pale grey powder |
Density | 2.813 g/cm3 (He pycnometery) |
Melting point | decomposes above 400C, compleat by 460C under N2 |
Boiling point | N/A |
insoluble in water, forms [Pd(CN)4]2-(aq) in alkalimetal cyanide solutions | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Palladium(II) dicyanide is the inorganic compound with the formula Pd(CN)2. A grey solid, it is a coordination polymer. It was the first palladium compound isolated in pure form. In his attempts to produce pure platinum metal in 1804, W. H. Wollaston added mercuric cyanide to a solution prepared by dissolving impure platinum in aqua regia. This precipitated palladium cyanide which was then ignited to recover palladium metal—a new element.
Structure
It had long been suspected that the structure of palladium cyanide consists of
Properties and reactions
Palladium dicyanide is insoluble in water with a
The equilibrium constant for the competition reaction
- PdL2+ + 4 CN− ⇌ [Pd(CN)4]2− + L
In the above equation, L is 1,4,8,11-tetraazaundecane ("2,3,2-tet")[4] was found to have a value of log K = 14.5.[5] Combination with the formation of the palladium complex with the tetradentate ligand
- [Pd(H2O)4]2+ + L ⇌ PdL2+ + 4 H2O, log K = 47.9
gives
- [Pd(H2O)4]2+ + 4 CN− ⇌ [Pd(CN)4]2− + 4 H2O, log β4 = 62.3.
This appears to be the highest formation constant known for any metal ion.[5]
The affinity of Pd(II) for cyanide is so great that palladium metal is attacked by cyanide solutions:
- Pd(s) + 2 H+ + 4 CN− ⇌ [Pd(CN)4]2− + H2
This reaction is reminiscent of the "cyanide process" for the extraction of gold, although in the latter reaction O2 is proposed to be involved, to give H2O.[3]
Exchange of between free cyanide ion and [Pd(CN)4]2− has been evaluated by 13C
- rate = k2[M(CN)42−][CN−], where k2 120 M−1−s−1
The bimolecular kinetics implicate a so-called
Pd(CN)2 has few uses. It has been demonstrated to facilitate the synthesis of alkenyl nitriles from olefins.
See also
References
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- PMID 21117699.
- ^ .
- ^ The tetramine 2,3,2-tet, H2N(CH2)2NH(CH2)3NH(CH2)2NH2, is similar to triethylenetetramine (2,2,2-tet) but has an additional methylene group between the two central nitrogen atoms
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