Polystannanes preparation

Highly coordinated tin enolates, reactivity, 9, 362 High-molecular weight polystannanes, preparation and properties, 12, 381... 

The Sn-NMR chemical shifts of the poly(alkyl-) and poly(arylstannanes), surprisingly, are quite similar the cyclic products have up field chemical shifts (Table 8.1). In contrast to the fairly linear polystannanes prepared by the catalytic action of zirconocene catalysts, branched polymers are obtained in the reaction of Bu2SnH2 with the rho-... 

Catenation is well established in organotin chemistry and distannane derivatives can be prepared by standard methods (see Ge, p. 396). The compounds are more reactive than organodiger-manes e.g. Sn2Meg (mp 23°) inflames in air at its bp (182°) and absorbs oxygen slowly at room temperature to give (Me2Sn)20. Typical routes to higher polystannanes are ... 

Most of the reactions that can be used to prepare distannanes can be extended to the preparation of oligo- and polystannanes, which have attracted interest for potential use in electronic and optical devices.455 The structures of the products are not necessarily those of completely linear catenanes, (R2Sn) , and different degrees of branching confer different properties. The formation of polymers is also frequently accompanied by the formation of cyclic pentamers or hexamers, and samples prepared by different methods may show substantially different properties. 

This review will focus on the NMR properties of Zintl ion complexes, namely the solution properties of the ions where E = Si, Ge, Sn, Pb, and the products derived from those clusters. Closely related clusters prepared by other means, such as the recent, elegant organo polystannane work of Schnepf, Power, Huttner, and Fischer, are briefly mentioned but are not the focus of this review. Related overviews of dynamic organometallic complexes [1,2] and the stmcture and bonding of Zintl ions [3-5] can be found in previous reviews and in other chapters of this book. 

In recent years, dehydrocoupling reactions catalysed by early transition metal complexes have become an increasingly important method for generating catenated species of the p-block elements. In addition to producing cyclic oligomers, this approach is used to prepare linear oligomers and polymers such as polysilanes and polystannanes of the type H(MR2) H (M = Si, Sn) (see Section 10.1.4). ... 

Polystannanes have been shown to display very interesting properties. They are highly photosensitive and exhibit photobleaching behaviour and on UV irradiation depolymerise to yield cyclic oligomers. The materials are thermally stable to 200-270 °C in air and at more elevated temperatures function as precursors to Sn02. " By using rhodium catalysts, branched polystannanes have been prepared. 

As described in Section II.E, polystannanes, which can be prepared by the Wurtz coupling of chlorostannanes with alkali metals and by the dehydrocoupling of hydrostannanes, exhibit intriguing physical properties. The Sita group reported a peculiar polymerization of -Bu2SnH2 with a RhH(CO)(PPh3)3 catalyst [Eqs. (21a) and (21b)].63... 

In this section we give a comparative overview on the recent developments in the preparation of polystannanes and discuss their properties. 

To circumvent the problem of polystannane degradation by sodium-induced Sn—Sn bond cleavage, a new synthetic procedure for the preparation of polystannanes under... 

The preparation of these higher molecular weight polystannanes, and the demonstration that they possess a chemical and mechanical integrity similar to that of the polysilanes (they are, however, much more photosensitive than polysilanes), will no doubt stimulate the further study of their properties and methods for their synthesis. 

Thermogravimetric analyses (TGA) of poly(dialkyl)stannanes under nitrogen showed onset temperatures for thermal decomposition in the temperature range of 250-280 °C, which is close to the values for related polydialkylsilanes. The TGA analyses of poly(diaryl)stannanes ° show onset temperatures for the decomposition in the range of 203-327 °C. Thermal decomposition of polystannanes leads to tin and tin oxide, and thus application of these materials for the preparation of conductors or coatings in semiconductors may be envisaged. It is worth noting that electronic conductivities of about 0.01 -0.3 S cm were observed for thin films of the polystannanes after exposure to SbFs vapor as an oxidant . ... 

Poly(dialkylstannanes), (Bu2Sn) and (Oct2Sn) , with Mw up to ca. 10,000,71 and the corresponding Bu2Sn/Bu2Si and BioSn/BioGe copolymers,72 have been prepared by electrolysis of the appropriate dichlorides in DME in a one-compartment cell fitted with a Pt cathode and Ag anode. The polystannanes appear to be stable to oxygen, but sensitive to moisture in the air, and the sensitivity of the Sn/Si or Sn/Ge copolymers increases with increase in the content of tin. 

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