Structures and bonding in [L]M(μ-CCR)₂M[L] and [L]M(μ-RC₄R)M[L]: requirements for C-C coupling

A theoretical analysis of [L]M(μ-CCR)₂M[L] and [L]M(μ-RC₄R)M[L], where M represents the selected elements from the main group, transition metals, lanthanides and actinides, shows how the central (μ-CCR)₂ and (μ-RC₄R) units reorganize as M traverses across the periodic table. In this context transition metal and actinide complexes are similar in nature, while lanthanide and main group complexes show similarity. The ground state electronic configuration and thus the metal oxidation state control these striking differences. An effective way to stabilize the (iii) oxidation state of thorium in a metallacycle complex is shown for the first time. A strategy is proposed to make a cross-connection between the two sets. The approach used here lends itself to obvious extensions.