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.