Bonding and structural preferences of indenyl complexes: (n = 0-3)

摘要

A search of bis(indenyl) derivatives available in the Cambridge Crystallographic Data Centre was performed and the two main families, MInd_2 and MInd2L_n (n = 1 -3), were structurally analyzed in detail. DFT calculations were performed for some relevant compounds in order to understand their electronic structure and interpret the experimental data. For MInd_2 complexes, the rotation angles between the rings show a wide range of values, depending both on the electron count and on the steric effects of the ring substituents. Hapticity change toward η~3 is induced by extra electrons, but a perfect η~3 coordination is never observed. For the electron deficient Cr(Ⅱ) complexes, two isomers having two and four unpaired electrons are known for different substituents, and the calculated energies in models are very close, as expected. The MInd_2L_2 family is the largest one and examples of η~3 coordination can be found. Both electronic and steric effects play a major role in determining the structural parameters of these species, but in the absence of bulky ring substituents, the rings are fluxional.