Two coordination compounds of SnCl2 with 4-methyl-pyridine N-oxide.

Felix Henkel,Hans Reuter

doi:10.1107/s2056989021000025

Abstract

In the solid-state structures of catena-poly[[di-chlorido-tin(II)]-μ2-(4-methyl-pyridine N-oxide)-κ2 O:O], [SnCl2(C6H7NO)] n , 1, and di-chlorido-bis-(4-methyl-pyridine N-oxide-κO)tin(II), [SnCl2(C6H7NO)2], 2, the bivalent tin atoms reveal a seesaw coordination with both chlorine atoms in equatorial and the Lewis base mol-ecules in axial positions. While the Sn-Cl distances are almost identical, the Sn-O distances vary significantly as a result of the different bonding modes (μ2 for 1, μ1 for 2) of the 4-methyl-pyridin-N-oxide mol-ecules, giving rise to a one-dimensional coordination polymer for the 1:1 adduct, 1, and a mol-ecular structure for the 1:2 adduct, 2. The different coordination modes also influence the bonding parameters within the almost planar ligand mol-ecules, mostly expressed in N-O-bond lengthening and endocyclic bond-angle widening at the nitro-gen atoms. Additional supra-molecular features are found in the crystal structure of 2 as two adjacent mol-ecules form dimers via additional, weak O⋯Sn inter-actions.

Highlights

In the solid-state structures of catena-poly[[dichloridotin(II)]-2-(4-methylpyridine N-oxide)-2O:O], [SnCl2(C6H7NO)]n, 1, and dichloridobis(4-methylpyridine N-oxide-O)tin(II), [SnCl2(C6H7NO)2], 2, the bivalent tin atoms reveal a seesaw coordination with both chlorine atoms in equatorial and the Lewis base molecules in axial positions
The different coordination modes influence the bonding parameters within the almost planar ligand molecules, mostly expressed in N—O-bond lengthening and endocyclic bond-angle widening at the nitrogen atoms
Examples are known with Lewis base molecules bearing nitrogen [SnCl2ÁtBuNH2 (Veith et al, 1988)], phosphorus [SnCl2ÁPh3P (Lukic et al, 2019); SnHal2ÁEt3P (Arp et al, 2013)], or sulfur [SnCl2Áthiourea (Harrison et al, 1983)] atoms as possible donor atoms, but the most prominent ones are those with oxygen atoms

Summary

Chemical context

Tin(II) halides, SnHal, are nominally electron-deficient compounds and strong Lewis acids. In the case of 1:2 adducts [e.g. SnF2Á2DMSO (Gurnani et al, 2013); SnCl2Á2TPPO (Selvaraju et al, 1998); SnCl2Á2DMSO (Barbul et al, 2011); SnBr2Á2DMSO, SnBr2Á2THF, SnBr2Á2acetone (Schrenk et al, 2009)] the tin(II) atoms exceed the electron octet as a result of the two additional donor electrons Both 1:1 and 1:2 compositions of one and the same tin(II) halide with one and the same Lewis base molecule have been previously reported only for SnI2 with DMSO (Ozaki et al, 2017). Similar calculations for 2 result in a bond-valence sum of 2.00 v.u., fully consistent with the tin oxidation state of +II

Supramolecular features

Refinement