Accurate theoretical description of the MePNR 2 bonds in phosphinidene complexes of manganese and rhenium [(CO) 5 MePNR 2 ] þ (R ¼ Me, i Pr, t Bu) and [(PMe 3 )(CO) 4 MePN i Pr 2 ] þ : A DFT-D3 study Krishna K. Pandey * , Pradeep Tiwari, Pankaj Patidar, Sunil K. Patidar, Ravi Vishwakarma, Pankaj K. Bariya School of Chemical Sciences, Devi Ahilya University Indore, Khandwa Road Campus, Indore 452001, India article info Article history: Received 31 May 2013 Received in revised form 9 July 2013 Accepted 9 July 2013 Keywords: DFT DFT-D3 Phosphinidene Electrophilic Manganese Rhenium abstract Geometry and bond energy analysis of MeP bonds in the terminal phosphinidene complexes of manganese and rhenium [(CO) 5 MePNR 2 ] þ (R ¼ Me, i Pr, t Bu) and [(PMe 3 )(CO) 4 MePN i Pr 2 ] þ were investigated at the DFT, DFT-D3 and DFT-D3(BJ) methods using functionals (BP86, revPBE, PW91 and TPSS). In all studied complexes, the p-bonding contributions to the total MeP bonds are significantly smaller (12.4e16.0%) than the s-bonding components. The phosphinidene (PNR 2 ) ligands are pre- dominantly s-donors. The electrostatic interaction DE elstat , in all complexes IeVIII, are larger than the orbital energies DE orb , which means, the MePNR 2 bonds in these complexes have greater degree of ionic characters (more than 50%). The DFT-D3 method provide quite accurate estimate of the dispersion energy for the studied complexes. The contribution of dispersion interactions is large in computing accurate bond dissociation energies between the interacting fragments. The BDEs are largest for the functional PW91 and smallest for the functional revPBE. The dispersion corrections are in the range 6.4 e11.1 kcal/mol (BP86), 7.2e8.6 kcal/mol (revPBE) and 5.7e8.6 kcal/mol (TPSS), which are smaller than the corresponding DFT-D3(BJ) dispersion corrections 7.6e11.8 kcal/mol (BP86), 8.7e12.8 kcal/mol (revPBE) and 5.8e9.0 kcal/mol (TPSS). The dispersion corrections calculated by DFT-D3 scheme increase on going from M ¼ Mn to M ¼ Re and smallest for the complexes [(PMe 3 )(CO) 4 M(PN i Pr 2 )] þ . Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction During the last decade, there has been a considerable interest in the development of approximate density functional theory (DFT) methods, which couple the computational efficiency of DFT with an improved description of dispersion interactions [1e9]. Dispersion interactions are empirically defined as the attractive part of the van der Waals-type interaction between the atoms and molecules that are not directly bonded to each other. Grimme and coworkers have developed efficient methods, DFT-D3 with zero-damping [10] and DFT-D3(BJ) [11] with Becke and Johnson (BJ) damping [12] for the computation of the dispersion interactions in molecules. Disper- sion effects are important not only for an adequate description of noncovalent interactions, but also for obtaining accurate bonding energies [8,9]. Transition metal phosphinidene complexes L n M ¼ PR have attracted a great attention as a powerful PR delivery reagents in organophosphorus chemistry [13e39]. Like metal carbene com- plexes, transition metal phosphinidene complexes show electro- philic (Fischer type) or nucleophilic (Schrock type) nature. In 1987, Lappert and coworkers reported representative examples of structurally characterized transition metal nucleophilic phosphi- nidene complexes [13]. For a long time the terminal electrophilic phosphinidenes were known as transient species generated and trapped in situ [28e39]. The synthesis and structural character- ization of terminal electrophilic phosphinidene complexes [(h 5 - C 5 Me 5 )(CO) 3 M{PN i Pr 2 }][AlCl 4 ] (M ¼ Mo, W) have been reported for the first time by Carty and coworkers in 2001 [40]. Since then, a number of terminal electrophilic phosphinidene complexes have been isolated and structurally characterized [41e61]. All structur- ally characterized electrophilic phosphinidene complexes and their important geometrical parameters are summarized in Chart 1 . Beside the remarkable synthetic development, several theoret- ical studies on transition metal phosphinidene complexes have * Corresponding author. E-mail addresses: kkpandey.schem@dauniv.ac.in, k_k_pandey3@rediffmail.com (K.K. Pandey). Contents lists available at ScienceDirect Journal of Organometallic Chemistry journal homepage: www.elsevier.com/locate/jorganchem 0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jorganchem.2013.07.029 Journal of Organometallic Chemistry 751 (2014) 781e787