Theoretical Investigations into Transition Metal−Group 13 Element Bonding:  Comparison between Ruthenium Porphyrin and Ruthenium Carbonyl Diyl Compounds

Abstract

Density functional calculations have been carried out to determine the structure and bonding for ruthenium porphyrin and carbonyl diyl complexes (CO) 4 Ru−EH eq ( 1a − e ), (CO) 4 Ru−EH ax ( 2a − e ), (Por)Ru−EH ( 3a − e ), and for (Por)Ru−E(trip) ( 4a − e, trip = 2,4,6-triisopropylphenyl) with E being a group 13 element (E = B−Tl). Subsequent natural bond orbital (NBO) analyses have been applied to examine in detail the Ru−E bonding situation and the influence of the porphyrin ligand. The calculations reveal high Ru−E (E = B−Tl) bond dissociation energies, especially for the ruthenium boron bonds in 3a and 4a . The NBO analyses show E−Ru π-back-bonding is most significant in the case of boron. The influence of the porphyrin ligand on this π-back-bonding interaction is similar to the one demonstrated for carbonyl ligands; however, the σ-donation from E to Ru is stronger in the case of the porphyrin ligand.