Theoretical Study On The Structures, Bonding Energies And Aromaticities For C₆F_mH_6-m And (C₆F_mH_6-m)₂ Cr (m=1-6)

Fluoro-compounds is a kind of important compounds. It is always one of the attractive research topics, because of its huge numbers and various kinds.With the developments of dyes, photographic materials, spaceflight technologies, polymer materials, pesticides and medicine, etc, fluorobenz-ene and other fluorinated benzenes as the basic raw materials of organic fluorine are widely used, so people are interested in the nature of the fluorine-containing compounds. However, the systemic study of C6FmH6-m and its sandwich complexes (C6FmH6-m)2Cr(m=1-6) are few.These are calculated for the geometries, frequencies, bonding energies and NICS of C6FmH6-m and (C6FmH6-m)2Cr (m=1-6). All calculations are performed with Gaussian 03 program using DFT/B3LYP method. The geometries and frequencies are calculated with 6-31 G(d,p) basis set.The NICS are calculated with 6-31 ++ G(d,p) basis set. In order to study the total NICS distribution in ligand plane and the various bond NICS contributions, the total NICS has been dissected into NICS contributions of various bonds, cores, and lone pair electronics by NBO.The results, calculated the eguilibrium geometries, frequencies, bonding energies and aromaticities of C6FmH6-m(m=1-6), indicate that all fluorinated benzenes are more aromatic than benzene, and the aromaticity increases with the number of F in C6FmH6-m(m=1-6). The various dissected bond NICSs reveal that the pz lone pair electrons of F atoms play a dominant role in the aromaticity of C6FmH6-m(m=1-6), and participate in formation ofπcurrent of the hexagon.The results, studied the eguilibrium geometries, frequencies, bonding energies and aromaticities of (η6-C6F6)Cr, (η6-1,4-C6F2H4)Cr, indicate that the ground states of them are C6v, C2v symmetries, respectively. The complexes have central, inner, outer aromaticities which are more aromatic than C6F6, 1,4-C6F2H4, respectively. There are three types of interactions asσ,πandδbetween the ligands and metal. The aromatic order of the half-sandwiches is (η6-C6F6)Cr< (η6-1,4-C6F2H4)Cr< (η6-C6H6)Cr.The results, analyzed the eguilibrium geometries, frequencies, bonding energies and aromaticities of sandwiches (η6-C6F6)2Cr, (η6-1,4-C6F2H4)2Cr, indicate that the ground states of them are D6d, D2 symmetries, respectively. The complexes have central, inner, outer aromaticities which are more aromatic than C6F6,1,4-C6F2H4 and less than (η6-C6F6)Cr, (η6-1,4-C6F2H4)Cr respectively. There are three types of interactions asσ,πandδbetween the ligands and metal. The aromatic order of the sandwiches is (η6-C6F6)2Cr (η6-1,4-C6F2H4)2Cr< (η6-C6H6)2Cr.The eguilibrium geometries, frequencies, bonding energies and aromaticities of sandwiches (η6-C6H6)Cr(η6-C6F6), (η6-C6H6)Cr(η6-1,4C6F2H4) and (η6-C6F6)Cr(η6-1,4-C6F2H4) are analyzed. The results indicate that the ground states of them are C6v(staggered), C1, C2v(staggered) symmetries, respectively. (η6-C6H6)Cr(η6-C6F6) C6v (staggered) is the most stable. The complexes have central, inner, outer aromaticities which are more aromatic than the responding ligand, and less aromatic than the responding half sandwich compound. The aromaticity increases due to three types of interactions asσ,πandδbetween the ligands and metal.