Bonding analysis of the neutral electrophilic phosphinidene complexes of vanadium and niobium [(η5-C5H5)(CO)3M(PNR2)] (R = Me, iPr, tBu): A DFT study

Density functional theory (DFT) calculations have been performed on the neutral electrophilic phosphinidene complexes [(eta(5)-C5H5)(CO)(3)M(PNR2)] (M = V, Nb; R = Me, Pr-i, Bu-t) at BP86/TZ2P/ZORA level of theory. The calculated geometry parameters of the complex [(eta(5)-C5H5)(CO)(3)V(PNR2)] are in good agreement with their available experimental values. On the basis of Mayer bond order analysis, the M-P bonds in all the studied complexes are found to be shorter than the M-P single bonds. On going from R = methyl to R = tertiary butyl, the optimized M-P bond distances increase. The observed geometry parameters are well supported by the results of energy decomposition analysis. The M-PNR2 bonds of the niobium complexes are slightly stronger than that of the vanadium complexes due to d-orbital extent. The orbital interactions between metal and PNR2 fragments in all complexes arise mainly from M <- PNR2 sigma-donation; however, the M -> PNR2 pi back-donation also contributes significantly (24.1% -28.5%) to the total orbital contribution. The pi back bonding contribution to the M-PNR2 bonds increases on going from M = V to M = Nb. The pi back bonding increases going from R = Me < iPr < tBu. The sigma-bonding orbitals in all studied complexes are well occupied. (C) 2013 Elsevier B. V. All rights reserved.