Tuneable, Protected and Processable Polystannanes from a Pincer Platform

我们最近展示了一种成功的策略，使用了超坐标(5坐标)锡中心，这导致了第一批光和湿度稳定的锡聚合物的例子。这是通过以下方式实现的：加入具有悬挂官能团的配体作为额外的2E-施主；增加锡的配位数并提供结构屏蔽以防止亲核攻击，缓和金属的Lewis酸性，并通过在相邻锡中心之间共享额外的电子密度来加强sigma-sigma键。在几种情况下，这些稳定的聚合物是半结晶的，一旦提纯就很难加工。为了加强整体设计，提出了一种钳形配体结构，该结构可能与TiN中心进行三个子午线相互作用，并用增溶基团进行修饰。该配体的6E给体性质为锡主链提供了理想的结构保护和电子可用性。为了制备聚合物，锡(IV)二卤化物(BR，I)中间体将从SnII钳形物种的氧化加成中获得，或者直接从锂钳形配体与RSnCl3(R=烷基，芳基)的易金属反应中获得，或者从含锡(IV)钳形小分子和SnCl4的三苯基的重分配反应中获得。小分子和低聚物夹钳物种的密度泛函理论(DFT)模型将用于将结构拟合与X射线数据进行比较，探测锡-锡键，并预测119锡核磁共振的化学共振。通过锡二氢化合物的脱氢偶联，将制备含有聚锡烷的新钳子，并对其进行评价。含有聚锡的钳子独特的成键安排提供了许多接入点，以调节这些本征导电材料的带隙，增加成膜性能，并通过溶解长链烷基或烷氧基部分确保加工性。这些湿气和光稳定的钳形聚锡烷的性能将被评估为在基于分子的电子设备中作为3D可打印聚合线的潜在用途。

We have recently demonstrated a successful strategy employing hyper-coordinate (5-coordinate) tin centers that have led to the first examples of light and moisture stable tin polymers. This was achieved by incorporating ligands with pendant functionalities that serve as additional 2e- donors; increasing the coordination number at tin and providing a structural shield to nucleophilic attack, moderating the Lewis acidity at the metal and strengthening the sigma-sigma bonds with additional electron density sharing between adjacent tin centers. In several instances, these stable polymers are semi-crystalline and become difficult to process once purified. To enhance the overall design, a pincer ligand architecture with the potential to make three meridional interactions with the tin center and modified with solubilizing groups, is proposed. The 6e- donor nature of this ligand provides ideal structural protection and electron availability to the tin backbone. To prepare polymers, Sn(IV) dihalide (Br, I) intermediates will be accessed from oxidative addition of Sn(II) pincer species, or directly from transmetallation reactions of lithiated pincer ligands with RSnCl3 (R = alkyl, aryl), or alternatively from redistribution reactions of triphenyl containing Sn(IV) pincer small molecules and SnCl4. Density functional theory (DFT) modelling of the small molecule and oligomer pincer species will be used to compare structural fits to X-ray data, probe Sn-Sn bonding, and predict 119Sn NMR chemical resonances. New Pincer containing polystannanes will be prepared from the dehydrogenative coupling of the tin dihydrido species and evaluated. The unique bonding arrangement of pincer containing polystannanes provides numerous access points to tune the band gap of these intrinsic conducting materials, increase film-forming properties and ensure processability via solubilizing long chain alkyl or alkoxy moieties. The performance of these moisture and light stable pincer polystannanes will be evaluated for potential uses as 3D-printable polymeric wires in molecular based electronics.