Facile Synthesis of Novel Two- And Three-Dimensional Coordination Polymers Containing Dialkyltin Phosphonate-Based Tri/Tetra-Nuclear Clusters with Appended Sulfonate Groups

The coordination-driven self-assemblies of mixed-ligand dialkyltin derivatives, [(Et2Sn)4 (O2P(OH)Me)2(O3PMe)2(OSO2Et)2·2H2O]n 1, [(Et2Sn)3(O3PMe)2(OSO2Me)2·CHCl3]n 2, and [(Me2Sn)3(O3PBut)2(OSO2Me)2·2CHCl3]n 3 have been achieved by reacting the tin precursors, [R2Sn(OR1)(OSO2R1)]n (R = Et, R1 = Et (1a), Me (2a); R = Me, R1 = Me (3a)) with an equimolar amount of methylphosphonic/t-butylphosphonic acid under mild conditions (rt, 8 h, CH2Cl2). These have been characterized by IR and multinuclear (1H, 13C, 31P, and 119Sn) NMR spectroscopy as well as single crystal X-ray diffraction. The asymmetric unit of 1 is composed of a tetranuclear, Sn4(μ2-PO2)2(μ3-PO3)2 core bearing an appended ethanesulfonate group on each terminal tin (Sn2) atom and two P(OH)···O hydrogen bonded water molecules. The ladder-like structural motif thus formed is extended into one-dimensional polymeric chains by virtue of bridging bidentate mode of the sulfonate groups. These chains are linked by O−H···O(S) hydrogen bonds involving H2O molecules and oxygen atoms of the sulfonate groups. The asymmetric units of 2 and 3 are composed of trinuclear tin clusters with a Sn3(μ3-PO3)2 core and two dangling methanesulfonate groups which are covalently bonded to the tin centers. The construction of three-dimensional self-assemblies is effected by variable bonding modes (μ2, μ3 in 2; μ2 in 3) of the methanesulfonate groups. Both the structural motifs possess five- and six-coordinated tin atoms and form rectangular channels which are occupied by CHCl3 molecules.