Poly(diaryl)stannanes:  Influence of Substituents on the σ−σ* Transition Energy

Abstract

Poly(diaryl)stannanes were prepared by the dehydropolymerization of secondary hydrostannanes Ar2SnH2 with dimethylzirconocene catalyst. At room temperature, H(Ar2Sn)nH polystannanes (Ar ) p-t Bu-C6H4, p-n Hex-C6H4, o-Et-C6H4, o-Et-p-n BuO-C6H3, p-n BuO-C6H4, p-(Me3Si)2N-C6H4) exhibit λmax values attributed to σ f σ* transitions in the range 430-506 nm. These values vary according to the polymer molecular weights and are independent of temperature between -20 and 90 °C. A sample of poly[bis(o-ethyl-p-n butoxylphenyl)]stannane exhibits a strong UV-vis absorption at 506 nm (tailing to ca. 550 nm), which corresponds to the smallest band gap yet observed for a group 14, σ-conjugated polymer. The H(Ar2Sn)nH polystannanes undergo photodecomposition in solution to give a mixture of the cyclohexamer and the cyclo-pentamer. Thermal gravimetric analyses for the polymers suggest that H(Ar2-Sn)nH polystannanes are thermally stable and have onset temperatures for thermal decomposition in the range 180-320 °C, under both nitrogen and air. The H(Ar2Sn)nH polystannanes undergo clean thermal decompositions to elemental tin (under nitrogen) or tin oxide (under oxygen or air), as shown by bulk pyrolysis.

Organometallic Polymers of Germanium, Tin and Lead

“…In order to circumvent this problem, monomeric diarylstannanes Ar 2 SnH 2 with the solubilizing substituents Ar = p-t-BuC 6 H 4 , p-n-HexC 6 H 4 , o-EtC 6 H 4 , p-n-BuOC 6 H 4 , o-Et,p-t-BuC 6 H 3 and p-(Me 3 Si) 2 NC 6 H 4 were used in the Cp 2 ZrMe 2 -catalysed dehydropolymerization 97,100 .…”

“…It was concluded that polystannanes are stable towards oxygen but extremely reactive to moisture. In solution, poly(diaryl)stannanes as well as poly(dialkyl)stannanes photochemically degrade to give cyclic oligomers, predominantly the pentamer and the hexamer 82,90,100 . Exposure of H[(p-t-BuC 6 H 4 ) 2 Sn] n H in THF to light for 30 min resulted in complete degradation to give a mixture of cyclic oligomers 100 .…”

“…The TGA analyses of poly(diaryl)stannanes 100 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.…”

“…solid vs solution). For comparison, the λ max values for Et(SnEt 2 ) 6 Et (Sn 6 ) 30 , [EtO(CH 2 ) 2 n-Bu 2 Sn(nBu 2 Sn) 3 ] 2 Sn(Bu-t) 2 (Sn 9 ) 23 and [EtO(CH 2 ) 2 n-Bu 2 Sn(n-Bu 2 Sn) 6 ] 2 Sn(Bu-n) 2 (Sn 15 ) 22 97,100 . A significant σ → π interaction was suggested to occur in these polymers, which lowers the band gaps with respect to those for related poly(dialkyl)-stannanes.…”

From poly(dialkylstannane)s to poly(diarylstannane)s: comparison of synthesis methods and resulting polymers

“…[13,14] However, most of these reactions suffered from drawbacks such as pronounced formation of cyclic stannanes as byproducts, low yields, low molecular weights or poor reproducibility. In addition, while poly(dialkylstannane)s have been extensively studied, [1,3,6 -8,10 -12,15 -18] the synthesis of poly(diarylstannane)s has been little considered owing to the insolubility of typical representatives like poly(diphenylstannane), [19] and therefore the material properties of well-defined poly(diarylstannane)s have still been modestly explored.…”