Diorganotin-based coordination polymers derived from sulfonate/phosphonate/phosphonocarboxylate ligands

The reactions of diorganotin precursors [R2Sn(OR1)(OSO2R1)](n)[R = R-1 = Me (1); R = Me, R-1 = Et (2)] with an equimolar amount of t-butylphosphonic acid (AT, 8-10 h) in methanol result in the formation of identical products, of composition [(Me2Sn)(3)(O3PBut)(2)(O2P(OH)Bu-t)(2)](n) (3). On the other hand, a similar reaction of 2, when carried out in dichloromethane, affords [(Me2Sn)(3)(O3PBut)(2)(OSO2Et)(2)center dot 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, R-1 = Me (6); R = Bu-n, R-1 = 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 mu(2)-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.