Conformational analysis of two new organotin(IV) structures completed with a CSD survey

Abstract

The conformational flexibilities are studied in two new organotin(IV) complexes, namely, trans-dichloridodimethylbis[N,N′,N′′-tris(2-chlorobenzyl)phosphoric triamide]tin(IV), [Sn(CH3)2(C21H21Cl3N3OP)2Cl2] or Sn(CH3)2Cl2{OP[NHCH2C6H4(2-Cl)]3}2, (I), and bis(dipropylammonium) tetrachloridodimethylstannate(IV), [(CH3CH2CH2)2NH2]2[Sn(CH3)2Cl4], (II), and their analogous structures from the Cambridge Structural Database (CSD). The conformations are considered based on the N—P=O—Sn torsion angles for (I) and the C—C—C—N, C—C—N—C, C—N—C—C and N—C—C—C torsion angles for the two symmetry-independent [CH3CH2CH2NH2CH2CH2CH3]+ cations in (II), and the ±ac±sp±ac (ac = anticlinal and sp = synperiplanar) and ±ap±ap±ap±ap (ap = antiperiplanar) conformations are observed, respectively. In both structures, the four atoms in the corners of the square-planar segment of the octahedral shape around the Sn atom participate in normal hydrogen-bonding interactions as acceptors, which include two O and two Cl atoms for (I), and four Cl atoms for (II). However, the phosphoric triamide ligands block the environment around the Sn atom and limit the hydrogen-bond pattern to form a supramolecular ribbon assembly, while in the presence of small organic cations in (II), a two-dimensional hydrogen-bonded architecture is achieved. The weak interactions π–π, C—H...π and C—Cl...π in (I), and C—H...Cl in (II) do not change the dimensionality of the hydrogen-bond pattern. The 62 CSD structures analogous to (I), i.e. with an SnOPN3 segment (including 83 entries) fall into four categories of conformations based on the N—P=O—Sn torsion angles. The 132 [(CH3CH2CH2)2NH2]+ cations from 85 CSD structures are classified into seven groups based on the torsion angles noted for (II). Most of the CSD structures adopt the same associated conformations noted for (I) and (II). 15 [Sn(CH3)2Cl4]2− anions extracted from the CSD are compared with the structure of (II).