Modulation of Zn–C Bond Lengths Induced by Ligand Architecture in Zinc Carbatrane Compounds

Bond lengths between pairs of atoms in covalent molecules are generally predicted well by the sum of their respective covalent radii, such that there are usually only small variations in related compounds. It is, therefore, significant that we have demonstrated that the incorporation of appropriately sized linkers between carbon and a metal center provides a means to modulate the length and nature of a metal–carbon interaction. Specifically, X-ray diffraction studies on a series of tris(1-methylimidazol-2-ylthio)methyl zinc complexes, [TitmMe]ZnX, demonstrate how the Zn–C bond lengths are highly variable (2.17–2.68 Å) and are up to 0.67 Å longer than the average value listed in the Cambridge Structural Database (2.01 Å). Furthermore, density functional theory calculations on [TitmMe]ZnCl demonstrate that the interaction is very flexible, such that either increasing or decreasing the Zn–C length from that in the equilibrium structure is associated with little energy change in comparison to that for other compounds with Zn–C bonds.