Diorganotin-Based Coordination Polymers Derived from Sulfonate/Phosphonate/Phosphonocarboxylate Ligands

The reactions of diorganotin precursors [R2Sn(OR1)(OSO2R1)]n [R = R1 = Me (1); R = Me, R1 = Et (2)] with an equimolar amount of t-butylphosphonic acid (RT, 8−10 h) in methanol result in the formation of identical products, of composition [(Me2Sn)3(O3PBut)2(O2P(OH)But)2]n (3). On the other hand, a similar reaction of 2, when carried out in dichloromethane, affords [(Me2Sn)3(O3PBut)2(OSO2Et)2·MeOH]n (4). A plausible mechanism implicating the role of solvent in the formation of these compounds has been put forward. In addition, the synthesis of [(Me2Sn)3(O3PCH2CH2COOMe)2(OSO2Me)2]n (5) and [R2Sn(O2P(OH)CH2CH2COOMe)(OSO2R1)]n [R = Et, R1 = Me (6); R = nBu, R1 = Et (7)] has been achieved by reacting 1 and related diorganotin(alkoxy)alkanesulfonates with 3-phosphonopropionic acid in methanol. The formation of a methylpropionate functionality on the phosphorus center in these structural frameworks results from in situ esterification of the carboxylic group. X-ray crystallographic studies of 1−7 are presented. The structures of 1 and 2 represent one-dimensional (1D) coordination polymers composed of alternate [Sn−O]2 and [Sn−O−S−O]2 cyclic rings formed by μ2-alkoxo and sulfonate ligands, respectively. For 3−5 and 7, variable bonding modes of phosphonate and/or sulfonate ligands afford the construction of two- and three-dimensional self-assemblies that are comprised of trinuclear tin entities with an Sn3P2O6 core as well as [Sn−O−P-O]2 and/or [Sn−O−S−O]2 rings. The formation of a 1D coordination polymer in 6 is unique in terms of repeating eight-membered cyclic rings containing Sn, O, P, and S heteroatoms. The contribution from hydrogen-bonding interactions is also found to be significant in these structures.

二有机锡前驱体(diorganotin precursors) [R₂Sn(OR¹)(OSO₂R¹)]ₙ [其中R=R¹=甲基(Me，编号1)；R=甲基(Me)、R¹=乙基(Et)，编号2] 与等摩尔量的叔丁基膦酸(t-butylphosphonic acid, RT, 8~10 h)在甲醇中反应，得到组成相同的产物[(Me₂Sn)₃(O₃PBut)₂(O₂P(OH)But)₂]ₙ（编号3）。另一方面，以化合物2为反应物，在二氯甲烷(dichloromethane)中进行类似反应，则得到产物[(Me₂Sn)₃(O₃PBut)₂(OSO₂Et)₂·MeOH]ₙ（编号4）。本研究提出了一种涉及溶剂在这类化合物生成过程中作用的合理机理。此外，通过将化合物1与相关的二有机锡(烷氧基)烷基磺酸酯(diorganotin(alkoxy)alkanesulfonates)在甲醇中与3-膦酰丙酸(3-phosphonopropionic acid)反应，成功合成了[(Me₂Sn)₃(O₃PCH₂CH₂COOMe)₂(OSO₂Me)₂]ₙ（编号5）以及[R₂Sn(O₂P(OH)CH₂CH₂COOMe)(OSO₂R¹)]ₙ [其中R=乙基(Et)、R¹=甲基(Me)，编号6；R=正丁基(nBu)、R¹=乙基(Et)，编号7]。这些结构骨架中磷中心上的丙酸甲酯官能团，源自羧基的原位酯化(in situ esterification)反应。本文报道了化合物1~7的X射线晶体学(X-ray crystallographic)研究结果。化合物1和2的结构为一维(1D)配位聚合物(coordination polymers)，分别由μ₂-烷氧基(μ2-alkoxo)配体和磺酸根配体形成的交替[Sn-O]₂与[Sn-O-S-O]₂环状结构构成。对于化合物3~5和7，膦酸根(phosphonate)和/或磺酸根配体的多种成键模式，构建出了二维和三维自组装结构，这类结构由带有Sn₃P₂O₆核的三核锡单元以及[Sn-O-P-O]₂和/或[Sn-O-S-O]₂环组成。化合物6中形成的一维配位聚合物较为特殊，其结构由包含Sn、O、P和S杂原子的八元环状单元重复构成。此外，氢键相互作用(hydrogen-bonding interactions)对这些结构的稳定性也具有显著贡献。