Structural studies in main-group chemistry. Part XVI. Crystal and molecular structures of bis(N-acetylhydroxylamino)dimethyltin(IV) and its monohydrate

Abstract

The crystal structures of Me₂Sn(ONH·COMe)₂(I) and its monohydrate (II) have been determined from diffractometer data by Patterson and Fourier techniques and refined by least-squares techniques to final R values of 0.063 [(I), 1 342 independent non-zero observed reflections] and 0 048 [(II). 2 183 reflections], respectively. Crystals of (I) are monoclinic, space group C2/c, with a= 13.791 8(7). b= 8.680 3(5), c= 13.468 0(7)Å, β= 139.53(5)°; crystals of (II) are also monoclinic, space group P2₁/c, with a= 14.110 7(7), b= 20.014 6(11), c= 8.863 5(5)Å, β= 106.95(4)°. The asymmetric unit of (II) contains two crystallographically independent Me₂Sn(ONH·COMe)₂ molecules, which have almost identical geometries, but differ significantly from the geometry of the Me₂Sn(ONH· COMe)₂ molecule in the anhydrous material, in which the tin atom lies on a crystallographic two-fold axis of symmetry. In all three molecules, the tin atom is six-co-ordinared by two chelating N-acetylhydroxylamino-ligands and two methyl groups, but, whereas the two methyl groups in (II) occupy essentially cis-positions of a distorted octahedron about tin [C–Sn–C 109.1(4)°; Sn–C 2.144(6), Sn–O 2.106(4), Sn ⋯ O 2.228(4)Å], the two molecules of Me₂Sn(ONH·COMe)₂ in (II) have geometries intermediate between ideal cis- and trans-octahedral [C–Sn–C 156.8(7)° Sn–C 2.17(2), Sn–O 2.16(2), Sn ⋯ O 2.36(2), 2.45(2)Å]. In the crystal lattice of (I). neighbouring molecules are held together by two NH ⋯ OC hydrogen bonds connecting adjacent N-hydroxylaminogroups giving rise to infinite linear stacks, with no significant bonding interactions between neighbouring stacks. The crystal lattice of (II) is made up of alternate layers, each composed of the two crystallographically distinct Me₂Sn(ONH·COMe)₂ molecules and separated by ayers of water molecules, which connect the layers of Me₂Sn-(ONH·COMe)₂ molecules by a network of hydrogen bonds. Me₂Sn(ONH·COMe)₂ molecules within each layer are also held together by hydrogen bonds, although in this case between NH and an oxygen atom bonded directly to the tin atom of an adjacent molecule.