Theoretical Study for Stabilizing Group 14 Elements by Five Different Carbene Ligands as L-E-E-L Complexes

Background: The computational calculations have been employed as a great tool to understand the stabilization of main group species by carbene ligands, which have been recognized as excellent compounds for coordinating highly reactive main-group elements in their zero oxidation state. Objective: The most important results that have been published up to now shown that N-Heterocyclic carbene and Cyclic (Alkyl)(Amino)Carbene ligands can stabilize main group compounds as highly stable complexes. Methods: That led us to further theoretically investigate the possibility of expanding this feature with phosphorus carbenes which have more electron contributing ability. Results: The bonding condition of the E2L2 molecules (where E is group 14 main group elements and L is Carbene ligands) may be understood in depth due to the combination of two ligands with two groups of 14 elements. The combination provides a guideline for synthesizing molecules with novel bonding motifs. Two atoms of group 14 are stabilized by two donor ligands in this bonding picture. In contrast to the E=E bonds seen in nitrogen carbene complexes, all phosphorus carbene complexes exhibit the E=L double bond character notation L=EE=L. L acts as a strong donor ligand in this complex. Conclusions: the thermodynamic calculations and orbital analysis can predict that complexes of L=E−E=L are stable enough to become isolated in a condensed phase for all compounds.