Structure and Bonding Analysis of the Cationic Electrophilic Phosphinidene Complexes of Iron, Ruthenium, and Osmium [(η5-C5Me5)(CO)2M{PNiPr2}]+, [(η5-C5H5)(CO)2M{PNR2}]+ (R = Me, iPr), and [(η5-C5H5)(PMe3)2M{PNMe2}]+ (M = Fe, Ru, Os)

Quantum-chemical DFT calculations for the electronic, molecular structure and M-PNR2 bonding analyses of the experimentally known cationic electrophilic phosphinidene complexes [(eta(5)-C5Me5)(CO)(2)M{(PNPr2)-Pr-i}](+) and of the model complexes [(eta(5)-C5H5)(CO)(2)M{PNR2}](+) (R = Pr-i, Me) and [(eta(5)-C5H5)(PMe3)(2)M{PNMe2}](+) were carried out using BP86/TZ2P/ZORA level of theory. The calculated geometrical parameters of the studied complexes are in good agreement with the reported experimental values. The short M-P bond distances and calculated Pauling bond orders (range of 1.23-1.68), suggest the presence of M-P multiple bond characters. The Hirshfeld charge analysis shows that the overall charge flows from phosphinidene ligand to metal fragment. The M-P sigma-bonding orbitals are well-occupied (>1.80e). The energy decomposition analysis revealed that the contribution of the electrostatic interaction Delta E-elstat is, in all studied complexes, significantly larger (55.2-62.6%) than the orbital interactions Delta E-orb. The orbital interactions between metal and PNR2 in [(eta(5)-C5H5)(L)(2)M{PNR2}](+) arise mainly from M <- PNR2 sigma-donation. The pi-bonding contribution (19-36%) is much smaller than the sigma-bonding. The interaction energies, as well as bond dissociation energies, depend on the auxiliary ligand framework around the metal and decrease in the order (eta(5)-C5H5) > (eta(5)-C5Me5) and CO > PMe3. Upon substitution of R = Pr-i with smaller group R = Me, the M-PNR2 bond strength slightly decreases.