An examination of the influence of crystal structure on molecular structure. The crystal and molecular structures of some diorganotinchloro-(N,N-dialkyldithiocarbamate)s, R2Sn(S2CNR′2)Cl, R = Me, tBu, Ph, Cy; R′2 = (Et)2, (Et, Cy) and (Cy)2: a comparison between solid state and theoretical structures

Abstract

Abstract The crystal and molecular structures of five compounds of the general formula R2Sn(S2CNR′2)Cl have been determined at room temperature. The colorless crystals of [Me2Sn(S2CNEt2)Cl] are monoclinic, space group P21/c with unit cell dimensions a = 10.896(2) Å, b = 9.869(4) Å, c = 12.722(2) Å, β = 105.08(1)°, Z = 4 and D x = 1.672 Mg m−3. The colorless crystals of [Me2Sn(S2CNCy2)Cl] are monoclinic, space group P21/c with unit cell dimensions a = 6.758(6) Å, b = 19.046(3) Å, c = 15.190(5) Å, β = 98.09(4)°, Z = 4 and D x = 1.512 Mg m−3. Crystals of colorless [tBu2Sn(S2CN(Et)Cy)Cl] are monoclinic, space group P21/n with unit cell dimensions a = 13.481(5) Å, b = 11.466(5) Å, c = 15.351(8) Å, β = 107.51(4)°, Z = 4 and D x = 1.382 Mg m−3. The colorless crystals of [Cy2Sn(S2CNEt2)Cl] are monoclinic, space group P21/c with unit cell dimensions a = 17.107(6) Å, b = 11.134(2) Å, c = 11.953(6) Å, β = 104.00(3)°, Z = 4 and D x = 1.409 Mg m−3. The colorless crystals of [Cy2Sn(S2CNCy2)Cl] are monoclinic, space group P21/n with unit cell dimensions a = 11.411(7) Å, b = 16.942(5) Å, c = 14.712(5) Å, β = 100.45(3)°, Z = 4 and D x = 1.370 Mg m−3. The structures were solved by direct methods and each refined by a full-matrix least-squares procedure to final R = 0.039 using 1367 reflections for [Me2Sn(S2CNEt2)Cl]; to R = 0.038 using 1881 reflections for [Me2Sn(S2CNCy2)Cl]; to R = 0.049 using 2707 reflections for [tBu2Sn(S2CN(Et)Cy)Cl]; to final R = 0.042 for 1914 reflections for [Cy2Sn(S2CNEt2)Cl]; and to final R = 0.045 for 2550 reflections for [Cy2Sn(S2CNCy2)Cl]. The crystallographic study shows that the tin atom in the R2Sn(S2CNR′2)Cl compounds exists in a distorted trigonal bipyramidal geometry in which the equatorial plane is defined by the two carbon atoms of the tin-bound organic substituents as well as more tightly held sulfur atom derived from an asymmetrically chelating dithiocarbamate ligand; the axial positions are defined by the less tightly held sulfur atom as well as the chloride atom. Attempts to correlate the Sn-ligand parameters with systematic variations in the Lewis acidity of the tin center (i.e. by moderating R) and the Lewis basicity of the dithiocarbamate ligand (i.e. by moderating R′) were unsuccessful across the series. The compounds have been subjected to geometry optimisation calculations which revealed that more symmetric structures exist in the gas phase. Systematic variations in the Sn-ligand parameters for the gas phase structures could be correlated with the Lewis basicity of the dithiocarbamate ligands in contrast to the solid state structures. Also, trends were found as the Lewis acidity of the tin center was varied. These trends could not, however, be correlated with the electronic structures of the tin-bound substituents alone, indicating that the steric profiles of the substituents also play an important role in moderating the Lewis acidity of the tin center. The results of the combined crystallographic/theoretical investigation of the R2Sn(S2CNR′2)Cl structures indicate that intermolecular forces, i.e. crystal packing effects, do exert a significant influence on the molecular geometry in these systems.