Polystannane

Structurally related but better characterized (and more useful) are the polysilanes (R2Si)n. Oligo- or polystannanes were first described by Löwig in 1852,[1] only 2 years after Edward Frankland's report on the isolation of the first organotin compounds.

[4] In 1917 Grüttner,[5] who reinvestigated results on hexaethyl-distannanes(H5C2)3Sn-Sn(C2H5)3 (reported by Ladenburg in 1870) confirmed the presence of Sn-Sn bonds and predicated for the first time that tin could form chain like compounds.

[8] The Wurtz reaction is still used for the preparation of poly(dialkylstannane)s. Treatment of dialkyltin dichlorides with sodium lead to polystannanes of high molar mass, however, in low yields and with formation of (cyclic) oligomers.

Determination of the molar mass at different degrees of conversion indicated that polymerization did not proceed according to a statistical condensation mechanism, but, likely, by growth onto the catalyst, e.g. by insertion of SnR2-like units.

Temperature-dependent, time-resolved pulse radiolysis microwave conductivity measurements of poly(dibutylstannane) yielded values of charge-carrier mobilities of 0.1 to 0.03 cm2 V−1 s−1, which are similar to those found for pi-bond-conjugated carbon-based polymers.

Repeating unit of polystannane.
Schematic representation of a linear polystannane macromolecule.
Three common synthesis routes used to prepare polystannanes: (1) polymerization of tin dichlorides by Wurtz or Wurtz-like reactions, (2) electrochemical reactions and (3) catalytic dehydropolymerization of tin dihydrides.
Synthesis of pure linear poly(dibutylstannane).
Optical micrographs (crossed polarizers) of an oriented film of poly(3-metylbutylstannane) produced by shearing the material at room temperature, top at 45° and bottom 90° in respect to the polarizers.