Natural bond orbital analysis and density functional study of linear and bent oxo-bridged dimers of rhenium(V)

Abstract

The calculations using the density functional theory (DFT) method were done on two diamagnetic oxo-bridged dinuclear rhenium complexes: [{Re(O)Br 2(3,5-Me 2pzH) 2} 2(μ-O)] ( 1) with a linear O Re–O–Re O core and [{Re(O)Br(3,5-Me 2pzH)} 2(μ-O)(μ-3,5-Me 2pz) 2] ( 2) with a bent Re 2O 3 unit (pzH monodentate N-pyrazole and pz bidentate N, N′-pyrazole ligand). The optimized geometries of 1 and 2 agree with the X-ray structures. The MO sequence is almost the same for 1 with a linear O Re–O–Re O core and 2 with a bent Re 2O 3 unit. The bending of Re 2O 3 unit in 2 is a consequence of steric congestion introduced by two coordinated 3,5-dimethylopyrazole bridging ligands. Additional information about binding in the complexes 1 and 2 was obtained by NBO analysis.