A DFT investigation of the structural and electronic properties ofCo(I) and Rh(I) half-sandwich complexes with heteroaromatic Pi ligands

Co(I) and Rh(I) half-sandwich complexes of the heteroaromatic 1,2-azaborolyl and 3a,7a-azaborindenyl anions with the ancillary ligand COD (1,5-cycloctadiene) are designed by using accurate state-of-the-art Density Functional Theory (DFT) calculations. Their structural and electronic properties are compared to those of the analogous compounds containing the classic hydrocarbon isoelectronic ligands, i.e. cyclopentadienyl and indenyl anions. A comparison is made between the catalytic ability of (η5-C5H5)-Co and (1,2-azaborolyl)-Co fragments toward alkyne [2+2+2] cyclizations, a class of reactions of paramount importance in industrial and pharmaceutical research for the synthesis of substituted benzenes, polycyclic and heterocyclic compounds, by theoretically addressing the fundamental mechanistic steps.