Institution: | a Departamento Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, ITQB, Av. da República, EAN, Apt 127, 2781-901, Oeiras, Portugal b Dep. Química e Bioguímica, Faculdade de Ciências, Universidade de Lisboa, 1749-016, Lisboa, Portugal c Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, Av. Rovisco Pais, 1, 1049-001, Lisboa, Portugal |
Abstract: | A search of bis(indenyl) derivatives available in the Cambridge Crystallographic Data Centre was performed and the two main families, MInd2 and MInd2Ln (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 MInd2 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 η3 is induced by extra electrons, but a perfect η3 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 MInd2L2 family is the largest one and examples of η3 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. |