Theoretical study of group 6 metallacyclic complexes with planar tetracoordinate carbon

The structures, stability, chemical bonding, aromaticity and first vertical electron transition energies of the group 6 metallacyclic complexes of M(OMe)3η3-R (M = Cr, Mo, and W; R = C3H3, C5H5, C7H5, C9H7, C11H7, C13H9, C13H7 and C15H9) have been investigated using density functional theory (DFT). Calculated results show that the radicals and group 6 metals can form stable metallacyclic complexes containing planar tetracoordinate carbon (ptC). According to [2 + 2]cycloaddition reactions, we have predicted the variation of the energies and free energies of the reactions to give the stable M(OMe)3η3-R complexes, which indicated that M(OMe)3η3-R (M = Cr and Mo; R = C7H5, C11H7, C13H7 and C15H9) and W(OMe)3η3-R (R = C3H3, C5H5, C7H5, C9H7, C11H7, C13H9, C13H7 and C15H9) are thermodynamically favorable. The first vertical transition energies of M(OMe)3η3-R (M = Cr, Mo and W) are in the range of 492–1020 nm, 490–741 nm and 401–624 nm, respectively.