Tetracyanoplatinate Complexes

The most extensively studied one-dimensional inorganic system in terms of the chemical and physical properties is that based on tetracyanoplatinate ions. A variety of complexes have been prepared to aid in the interpretation via comparative studies of various physical properties. Since several of these substances can be easily obtained in the form of large high purity single crystals, they have been the principle choice as a material for intensive study. 

The attempted preparations of partially oxidized complexes, 4, for X = F (246), I (246,262) or CN (337) were not successful nor have partially oxidized nickel and palladium analogues been reported. 

Recent work has suggested a trace of bromide (arising from impurities in the starting materials) to be associated with a cation-deficient species (310), that is, Ki.78Pt(CN)4Bro.o34(H20)2. Further work is necessary to establish the relationship between Ki.74Pt(CN)4(H20)i.8 and K1.78 Pt(CN)4Bro.o34(H20)2 especially since recent powder x-ray data indicate that these complexes are not equivalent (310). 

In 1967, Piccinin and Toussaint (337) reported the nitric acid oxidation of platinum metal, presumably in the presence of cyanide ions, yielding crystals of an unusual platinum(III) complex, K2Pt(CN)5(H20)3. Only the crystallographic and chemical analysis have been reported for this complex. Recent x-ray powder data has shown K2Pt(CN)s(H20)3 to be 4b (515). Cocrystallization of K2Pt(CN)4 and K2Pt(CN)e (571) is reported not to give evidence of the formation of a partially oxidized phase (337). 

Dissolution of the bronze colored crystals of 4 (X = Cl, Br) in water yields a mixture of the diamagnetic platinum(II) and platinum(IV) materials outlined in Eq. 42. Recent data (559) suggest a more complex equilibrium is present than in Eq. 42. Preliminary evidence suggests that the rra s-Pt(CN)4X(OH)2- ion is formed upon dissolution of 4, Fig. 22 (364a, 559). This is consistent with the formation of this hydroxo complex in the aquation and subsequent hydrolysis reaction of I/ a j-Pt(CN)4X2 (X = Cl, Br) (86) and the note that Pt(II) complexes catalyze the substitution reactions of formally inert Pt(IV) complexes (34). Addition of 0.1 Af KX suppresses these interfering reactions. Fig. 22. 

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The cesium [hydrogen bis(sulfate)] tetracyanoplatinate complex exhibits a room-temperature electrical conductivity (four probe technique) of approximately 113 ohms 1 cm 1, while that of the Rb analog (Pt—Pt - 2.83 A) is 1500-2000 ohms"1 cm 1. 

Caution must be exercised in interpretation of the physical data for the tetracyanoplatinate complexes (as well as all other one-dimensional systems) because purity and morphology are extremely critical for one-dimensional systems. For example, a 1.00 x 0.01 x 0.01 mm perfect needle crystal of K2Pt(CN)4Xo.3 would contain — lx 10 parallel strands each of 3.5 x 10 collinear platinum atoms. Thus, purity (foreign impurities, end groups, and/or crystalline defects) levels of one part per million indicate that each strand averages more than three defects, which may drastically alter some (and in particular transport) measurements. Besides the intrinsic purity problem of one-dimensional systems, the physical properties of K2Pt(CN)4-Xo.3(H20)a are a strong function of hydration. Dehydration alters the crystal structure and thus properties of the complexes (78). Care must be maintained to ensure that dehydration is not caused by the measurement technique. For... 

All of the aforementioned tetracyanoplatinate complexes. Table IV, form columnar structures in the solid. The partially oxidized complexes exhibit short uniform metal-metal spacings and the physical properties characteristic of metallic systems. The K2Pt(CN)4Xo.3(HaO)a complexes, due to the ease of growing large defect-free crystals, have been the most extensively studied inorganic one-dimensional systems. In addition, the ability to carve these crystals with a sharp knife (364a) is an aid in performing some physical measurements. 

ONE-DIMENSIONAL TETRACYANOPLATINATE COMPLEXES CONTAINING PLATINUM-ATOM CHAINS... 

One-Dimensional Tetracyanoplatinate Complexes 149 E. CESIUM TETRACYANOPLATINATE AZIDE (2i Q.2S) HYDRATE,... 

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