Polystannanes with azobenzene moieties designed to protect the Sn-Sn backbone from light- and moisture-induced degradation are described. The azo-stannyl precursor 3 (70 %) is converted in good yields (88-91 %) to the mono- (4), and dichlorostannanes (5), by sequential chlorination, followed by further reduction of 5 to the dihydride (6) using NaBH (78 %). All stannanes were characterised by NMR ( H, C, Sn) spectroscopy and HRMS; in addition, 3, 4 and 5 were structurally elucidated using X-ray diffraction analysis. Metal-free dehydrocoupling of 6 at RT leads exclusively to homopolymer (7-i) displaying an initial solution Sn NMR signal (δ=-196 ppm) that migrates to -235 ppm after 10 days (7-f). In contrast, metal-catalyzed dehydrocoupling of 6 in toluene at RT leads directly 7-f. Random co-polymers formed from 6 and (nBu) SnH at 4:1 (8 a) and 1:1 (8 b) ratios were compared to the alternating polystannane (9) prepared by the reaction of 6 with (nBu) Sn(NEt ) . DFT calculations of 3-6 indicate that hypercoordination at Sn is influenced by substituents and by solvation. Homopolymer 7 was found to have unprecedented moisture and light stability in the solid state for >6 months.

The synthesis and solid‐state molecular structures of two dichlorido(aryl)(alkyl) tin compounds, 5 and 8, both key intermediates to tunable polystannane architectures, are reported. The materials were further investigated by single‐crystal XRD and a DFT analysis of their preferential “open and closed” geometries. Conversion of said compounds to their dihydride analogues was undertaken, followed by their application as monomers for polystannane polymer synthesis. The properties of two asymmetrical polystannanes prepared by transition‐metal‐catalyzed dehydropolymerization of dihydrido(aryl)alkylstannanes (6 and 9) were investigated. The first product was the structurally simple, modest molecular weight, semi‐crystalline light‐ and moisture‐stable polystannane 10 with NMR (119Sn) evidence of prominent Sn←O hypercoordination along the polymer backbone. The second was the lower molecular weight, tosylated four‐coordinate polystannane 11 with no evidence of hypercoordination. Differential scanning calorimetry (DSC) of polymer 10 revealed a reversible semi‐crystalline nature, whereas an amorphous character was detected for polymer 11. Polystannane 10 was also found to be exceptionally stable to both moisture and light (>6 months) and a promising candidate for the design of readily modified (i.e., tunable) polystannane materials.

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A structure–property study using a new approach to electronically desymmetrize the BODIFY core.

<p>Theoretical calculations of polystannanes in an all trans-configuration possess a relatively small band gap (~2.8 eV). This is due to the extensive σ-σ overlap of the diffuse 5sp3 orbitals of Sn atoms in the conjugated Sn-Sn polymer backbone, which leads to a visible σ-σ* transition by UV-vis spectroscopy. The electronic properties of polystannanes suggests that these materials are candidates for semi-conducting intrinsic polymers. However, due to the weak bonding between Sn-Sn atoms and the Lewis acidic nature of Sn centers, polystannanes readily degrade with exposure to daylight and moist atmospheres. This project demonstrates clear synthetic pathways and designs to stabilize the Sn-Sn backbone. This was accomplished by incorporating functional ligands with Lewis basic heteroatoms such as oxygen or nitrogen moieties which can form a hypercoordinate interaction with the Sn center. Two major types of asymmetrical polystannane systems were investigated: 1) a flexible system where Sn centers are attached to a propyl chain containing either a bulky or small functional donor ligand and 2) a rigid system where the Sn center contain either a hypercoordinate benzyl methoxy ether (C,O) or benzyl dimethyl amine (C,N) ligand prepared using a direct approach. This thesis is broken into three different chapters. Chapter 1 and 3 include all synthetic pathways, characterization and stability testing of both flexible and rigid polystannanes. Chapter 2 describes a high molecular weight (Mw = 60 kDa) film forming, semi-crystalline (Tg = 49.3 °C and Tm = 110.1 °C) flexible asymmetrical polystannane containing a propylhydroxy ligand that displays exceptional stability to light and moisture (> 9 months). In addition, a tosyl containing polystannane that could function as a macromolecular intermediate was prepared. Substitution of model tosyl stannanes was demonstrated, and substitutions of the tosyl polystannane are ongoing.</p> <p><br></p>