Chiral self-assembly of methyltin(IV)-naproxenates: Combining dative Sn–O bonds, secondary Sn⋯O interactions and C–H⋯O hydrogen bonding to make an inter-helical meander-shaped network and a cross-linked Z-shaped ribbon

Abstract

Three new chiral organotin(IV) carboxylates, Me 2Sn(nap) 2 ( 1), {[Me 2Sn(nap)] 2O} 2 ( 2) and Me 3Sn(nap) ( 3) (nap = ( S)-(+)-6-methoxy-α-methyl-2-naphthaleneaceto anion) have been synthesized. All of them have been characterized by elemental analysis, multinuclear ( 1H, 13C and 119Sn) NMR and IR spectroscopy. The crystal structures of 1 and 2 have been determined by X-ray diffraction analysis. The bicapped tetrahedral molecules of 1 are linked by C–H⋯O hydrogen bonds into homochiral helices, which are also interconnected by C–H⋯O interactions to form an inter-helical meander-shaped network. The molecule of 2 is a parallel double helix incorporating four chiral tin centers in a Sn 4O 10C 4 ladder type molecular skeleton. The C–H⋯O interactions translate the molecular chirality of 2 throughout the crystal via formation of infinite ribbons. These ribbons in their turn are further cross-linked by C–H⋯O hydrogen bonds. The structural characterization of the complexes 1– 3 in solution has been performed by routine multinuclear 1H, 13C and 119Sn NMR as well as specialized multidimensional ( 1H– 119Sn-gHMQC and 1H-DOSY) experiments. The relevant 2 J 1 H – 119 Sn and 1 J 13 C – 119 Sn coupling constants have been extracted and related to molecular geometries on the basis of the literature data. The measurement of the translational diffusion constants using diffusion ordered spectroscopy allowed the estimation of the spherical hydrodynamic radii of the newly prepared structures.