Solvent and intermolecular nitrogen coordination dictated formation of self-assembled organostannane-macrocycles based on monomers and coordination polymers with unsymmetrical 5-[(E)-2-(4-pyridyl)-1-diazenyl]-2-hydroxybenzoate ligand: Structural topologies and dimensionality

Abstract

A series of six new organotin(IV) compounds, namely, [nPr3Sn(HL)(MeOH)] 1, [nBu3Sn(HL)]n2, [Bz3Sn(HL)]n3, [Ph3Sn(HL)]n⋅nC6H64, [Ph3Sn(HL)(EtOH)] 5 and [nBu2Sn(L)]n6 were synthesized by reacting appropriate tri- and di-organotin(IV) precursors with the flexible pro-ligand 5-[(E)-2-(4-pyridyl)-1-diazenyl]-2-hydroxybenzoic acid. Their solid-state structures were deduced from single crystal X-ray diffraction data and, in the case of compound 6, also by solid-state 13C and 119Sn NMR spectroscopy. Compounds 1 and 5 are mononuclear as a consequence of methanol/ethanol coordination preventing the propagation of the polymers. The monodentate oxygen atom from the carboxylate group of HL− and the tin-coordinated oxygen atom of alcohol are situated at the axial positions, while Sn-R substituents are at the equatorial sites, defining the distorted trigonal-bipyramidal coordination polyhedron. Both 1 and 5 form one-dimensional (1D) chains created by virtue of O−Hsolv⋯Npy hydrogen bonding interactions, and antiparallel running chains in 1 furnish 34-membered dinuclear macrocyclic rings occupied by SnPr3 groups. Compounds 2–4 feature a one-dimensional coordination polymer facilitated by intermolecular N→Sn bond formation with the pyridyl substituent of LH−. The axially located OOCO and Npy donor atoms and equatorial Sn-R groups give rise to a trigonal-bipyramidal geometry. While similar coordination geometries are observed for 2–4, the tri-n-butyl derivative 2 generates 60-membered macrocyclic rings where four n-butyl groups from two neighboring molecules occupy the cavities. The triphenyltin analogue 4 forms two-dimensional layers with voids filled by benzene solvate molecules, and the sterically demanding tribenzyltin groups in compound 3 result in only relatively weak C−H⋯π, C−H⋯N and van der Waals contacts. On the other hand, compound 6 is a two-dimensional (2D) coordination polymer displaying a distorted pentagonal-bipyramidal geometry around the tin atom where four oxygen atoms of two ligand molecules and the nitrogen atom of a ligand constitute the equatorial plane, while the carbon atoms of the n-butyl groups complete the axial positions. The molecules of 6 self assembled to an interesting dimeric tecton based on a four-membered Sn2O2 ring, generating large 48-membered hexanuclear macrocycles, where the cavities are filled by four di-n-butyl groups from two neighboring molecules. The solution behaviors of compounds 1–5 were judged from the results of the 119Sn NMR spectroscopic characterization.