Bis oxalato platinates

In addition to the partially oxidized tetracyanoplatinates, bis(oxalato)platinate-(II) can be nonstoichiometrically oxidized by chemical oxidants13 to form highly lustrous needlelike crystals containing platinum in the 2.36 oxidation state. These complexes have not been characterized to the extent of the tetracyano-platinate complexes however, the oxalato complexes are reported to be highly conducting.13 The starting material is bis(oxalato)platinate(II), which can be prepared in 30% yields from hexachloroplatinate(lV) and potassium oxalate.9... 

Potassium Bis(oxalato)platinate(II) (2 1) Dihydrate, K2Pt(C204)2-2H20... 

Preparation of PVP-stabilized Ag/Pt bimetallic nanoparticles by borohydride reduction from silver(I) bis(oxalato)platinate(I) was also proposed (46). 

Table 2 Partially Oxidized Bis(oxalato)platinate Salts...

The partially oxidized bis(oxalato)platinate salts of monovalent cations are often characterized by the existence of several crystalline phases each with very similar stoichiometry. This is particularly true for the potassium salts. Four crystalline phases of stoichiometry Kt6i0.04[Pt(C2O4)2]-xH2O (a-, P-, 5- and e-KOP) are known plus K] sitPt O J HjO (y-KOP).63... 

A large number of partially oxidized divalent cation salts of the bis(oxalato)platinates have been reported (see Table 2).63 Only the series Mx[Pt(C204)]-6H20 (MOP where M = Fe, Co, Ni, Zn, Mg and 0.80 < x < 0.85) has been extensively studied.68 83 For most of these salts detailed studies have been made of their crystal structures and optical reflectivity at room temperature, and the variation of superlattice reflections, diffuse X-ray scattering, thermopower and DC electrical conductivity with temperature. 

Both CoOP and MgOP exist in the same orthorhombic structure with space group Cccm at an appropriately high temperature with little variation in unit cell dimensions.68,73 This structure for CoOP is shown in Figure 5 and contains linear chains of [Pt(C204)2]x units with dPt Pt of 2.85 A in the Mg2+ and 2.841 A in the Co2+ salts.73 The divalent metal ions are located between the planes containing the bis(oxalato)platinate ions and are coordinated to six water molecules with... 

A characteristic feature of these partially oxidized bis(oxalato)platinate salts of divalent cations is the coexistence of two modulations of the lattice over a wide temperature range (a) a one-dimensional modulation, as detected by the appearance of diffuse lines on X-ray films, perpendicular to the [Pt(C204)2] anion stacking direction and surrounding the even Bragg reflection layer lines of non-zero order (b) a three-dimensional modulation which gives rise to a complicated pattern of fine satellite spots in the neighbourhood of every reciprocal layer line. 

Figure 6 Variation of electrical conductivity with inverse temperature for a series of bis(oxalato)platinate salts...

Krogmann and Geserich showed these compounds to be linear metal atom chain compounds with short intrachain Ir—Ir separations of 2.86 A, and that they have related structures to the cation-deficient bis(oxalato)platinates.87 A detailed study of these compounds showed that the... 

The electrical conductivity of several of these compounds has been reported.88 Compressed pellet four-probe measurements at room temperature are usually in the range 10 2-5 fl I cm-1 although a value of 150-500 has been reported for orientated polycrystals. Most of the compounds show semiconductor behaviour with activation energies of about 35 meV. Ko.6o[Ir(CO)2Cl2]-0.5H20 shows evidence of a transition to more metal-like behaviour near room temperature,88 It seems very likely that if good quality single crystals of these compounds could be obtained then they would exhibit conduction properties similar to those of the cation-deficient tetracyanoplatinates or bis(oxalato)platinates. 

Most metal chain complexes involve divalent and partially oxidized square-planar complexes of Ni, Pd, and Pth Examples include the tetracyanoplatinates , bis(oxalato)platinates , bisglyoximato and several complexes containing chelating 7t-conjugated ligands . Nonstoichiometric triplatinum tetraoxides are discussed independently. 

Compounds Containing Nickei, Palladium, and Piatinum Chains 9.2.12.1.2. Bis(oxalato)platinates. 

Unlike the tetracyanoplatinates, the bis(oxalato)platinates, with the exception of the red form of the calcium salt, do not form metal chain structures unless they are partially oxidized. Metal chain substances containing nonstoichiometric mono- (e.g., HsO, Li, Na, K, Rb, NH4) or divalent (e.g., Mg, Ca, Si, Br, Mn, Co, Ni, Cu, Zn " ) cations are prepared with the nominal chain repeat unit being the [Pt(02C202)2] z = 1.6- to 1.7-) moiety. ... 

Solubility plays an important role in the preparation of this class of materials. The bis(oxalato)platinates are less soluble than the tetracyanoplatinates, and special procedures must be developed for crystal growth. 

The bis(oxalato)platinate(II) complexes based on [Pt(C204)2] , forms another family of linear chain systems, and the partially oxidised complex series, Cx[Pt(C204)2]-n(H20) (C = K, Rb, Mg " ", Co, Ni, Zn ), was reported.According to elemental analysis and X-ray diffuse scattering measurements, the formal oxidation state of platinum in this series is estimated in the range of -1-2.19 to -f2.38. The average Pt-Pt distance is 2.84-2.89 A and the conductivity at room temperature is 10 -10 S cm , depending on the associated cation. 

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