The nature of M-PNR2 bonds in the electrophilic phosphinidene complexes [(L)(CO)3M{PNR2}]+ (L = PMe3, PPh3; M = Co, Rh, Ir; R = Me, iPr): Structure, bonding and 31P NMR study

Abstract

Theoretical insights into the structure and the nature of M-PNR2 bonding in the cationic electrophilic phosphinidene complexes [(L)(CO)3M{PNR2}]+ (M = Co, Rh, Ir; R = iPr, Me; L = PMe3, PPh3) have been investigated at DFT level with emphasis on the density functional BP86, PBE, PW91 and TPSS and dispersion interactions, DFT-D3(BJ). Dispersion corrected functional yields accurate geometries. The geometry optimized with PBE-D3(BJ) functional is in excellent agreement with the experimental geometry of structurally characterized cobalt phosphinidene complex [(PPh3)(CO)3Co{PNiPr2}]+ (IV). The effects of metal atom, trans-influence of phosphine ligands (PMe3, PPh3) and substituent at nitrogen atom of PNR2 ligand on the M-PNR2 bond distances and M-P-N bond angles have been studied. The lengthening of M-PNR2 bonds trans to PMe3 ligand than those trans to PPh3 are due greater trans-influence of the PMe3 ligand. The 31P NMR chemical shifts of phosphinidene and phosphine ligands phosphorus in the complexes I-XII have been calculated out at PBE-D3(BJ)/TZ2P/ZORA with scalar (SC) and spin orbit (SO) relativistic level of theory in solvent chloroform. The computed values of 31P NMR chemical shifts are within the range of experimental values. The Mulliken charge analysis shows that the overall charge flows from phosphinidene ligand to metal fragment. The energy decomposition analysis divulged that the contribution of the electrostatic interaction ΔEelstat in all studied complexes is larger (54.5%–61.3%) than the orbital interactions ΔEorb. The π-bonding contribution is much smaller than the σ-bonding (85.4%–87.0%).