Palladium ammine coordination

Louis-Nicolas Vauquelin (1763-1829) discovered the pink compound tetraamminepalladium(II) tetrachloropalladate(II), [Pd(NH3)4][PdCl4].14 This compound, which contains coordinated palladium in both the cation and the anion, is still known as Vauquelin s Salt after its discoverer. The corresponding platinum compound, [Pt(NH3)4][PtCl4], was discovered by Heinrich Gustav Magnus (1802—1870).15 It constitutes the first discovered platinum ammine and is known as Magnus ... 

Coordination Compounds. Palladium forms numerous complexes with ammonia and with simple amines. Examples are [Pd(NH3)4]2+ [15974-14-8], [PdCl(dien)]+ [17549-31-4], cis-[PdCL (NH3)2] [15684-18-1], and trans-[PdC (NH3)2] [13782-33-7]. Monoammine complexes such as [PdCl3 (NH3)] [15691-32-4] are stable but less common. Examples of aromatic amine complexes include trans- [PdCf (pyr)2] [14052-12-1], [PdCl2(bipy)] [14871-92-2], and nucleosides such as [PdCl(dien)(guanosine)]+ [73601-42-0] (193). Complexes of Pd(IV) such as [PdCl2(NH3)4]2+ [70491-81-5] and [PdCl4(bipy)] [57209-01-5] may be prepared by chlorine oxidation of the corresponding Pd(2+). The aromatic amine Pd(IV) complexes are more stable than ammine and aliphatic amine species, which are reduced to Pd(II) in water or thermally (194). 

Here, there is no evidence that masking interferes in any way with these reactions. When the complexes of palladium (II) were examined for a similar reactivity, no complexes containing coordinated chloramines could be isolated (43, 44)- The reaction of ammines of platinum (IV) with bromine can be used to introduce bromoamine in the coordination sphere, but the products are somewhat less stable than those obtained with chlorine. The general nature of the processes is similar. One example of a bromination reaction established by Kukushkin is ... 

Palladium(II) normally coordinates to the N3 atoms of the cytosine base forming a square planar geometry. " An unexpected isomerization from trans- to cA-coordination of ammine ligands about Pd" occurs when tr<2 x-[Pd (NH3)2(H20)2] is added to the mononuclear trans-Pd"(NH3)2(1-methyl cytosine)2(N03)2. The resulting bridged dinuclear Pd" complex has two cis-[Pd (NH3)2] units bridged by cytosines through their to both N3 and deprotonated N4... 

The most straightforward case of electrostatic adsorption occurs with the most stable metal complexes such as platinum or palladium tetraammines, [(NH3)4Pt]+ and [(NH3)4Pd]+ or PTA and PdTAs, respectively. Over the wide pH and concentration ranges that can be employed during syntheses from the lab to the industrial scale, the relatively strongly bound ammine ligands of these coordination complexes remain intact. This has been most directly confirmed in the case of Pt by extended X-ray absorption fine structure (EXAFS) analysis of PTA solutions and adsorbed species [23], and for PdTAs less directly by XPS [24]. 

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