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Abstract: Structure and bonding analyses of the complexes [(PNP)Ir(NX)]+ (X=O, S, Se; PNP=N(CHCHPMe2)2) were investigated at the DFT, DFT-D3 and DFT-D3(BJ) levels using BP86, BLYP, PBE, revPBE and TPSS functionals. The Ir–NX bond in the thionitrosyl complex is longer than that in the nitrosyl and selenonitrosyl complexes, which is consistent with the observed trend for their experimental values. The Ir–NX bond has essentially Ir NX double bond character, which supports the σ-donor and π-acceptor abilities of the [NX]+ ligands. The non-covalent P–NX distances decrease in the order DFT>DFT-D3>DFT-D3(BJ). The Ir–NX bond has a larger covalent character (85.7, 75.9 and 74.6%). Dispersion interactions between the metal and [NX]+ fragments are in the range 3.2–5.5kcal/mol (BP86), 3.2–5.4kcal/mol (BLYP), 1.9–3.1kcal/mol (PBE), 3.5–5.5kcal/mol (revPBE) and 2.6–3.8kcal/mol (TPSS), which are smaller than the corresponding DFT-D3(BJ) dispersion corrections 4.9–8.6kcal/mol (BP86), 5.2–7.9kcal/mol (BLYP), 2.7–4.0kcal/mol (PBE), 5.3–7.6kcal/mol (revPBE) and 2.7–5.2kcal/mol (TPSS). The dispersion corrected DFT (DFT-D3 and DFT-D3(BJ)) methods provide quite an accurate estimate of the dispersion energy, which can be judged by the observation that the experimental and optimized Ir–NX bond distances are consistent with the most accurate dispersion corrected DFT-D3(BJ) bond dissociation energy of Ir–NX bonds. [Copyright &y& Elsevier]

Abstract: Quantum-chemical calculations were used to investigate the molecular and electronic structures as well as bonding energies of the molybdenum–ylidyne complexes trans-[X(PMe3)4MoX=F, Cl, Br, I; E=Si, Ge, Sn, Pb) at the BP86/TZ2P/ZORA level of theory. The calculated geometrical results are in excellent agreement with the available experimental results. The Mostances are significantly short, and the calculated Pauling Mo–E bond orders are ∼2.40–2.65. The electronic structures of the Mohow the presence of genuine triple bond containing an σ-bond and two π-bonds in all studied complexes. The Mo-bonds are polarized towards the heavier group 14 elements while the π-bonds are polarized towards the molybdenum metal. The partial charges on the [EMes]+ fragments (0.67–0.93) indicate that the overall charges flow from the metal fragments to the [EMes]+ fragments. The nature of Molso investigated by means of energy decomposition analysis which reveals that the metal–ligand π-orbital interactions between [X(PMe3)4Mo]− and [EMes]+ fragments are the most dominant interactions, contributing (80–85%) to the total ΔE orb terms. The strength of Moainly depends on the π-acceptor ability of [EMes]+ group. It decreases when 14 group element becomes heavier in the trend Si>Ge>Sn>Pb and in the order F>Cl>Br>I. [Copyright &y& Elsevier]

Abstract: Density functional theory (DFT) calculations have been performed to investigate the nature of the M–Bi bonds in dihalobismuth complexes of iron, ruthenium and osmium, [(η5-C5H5)(CO)2M(BiX2)] (M=Fe, Ru, Os; X=Cl, Br, I) and [(η5-C5H5)(PMe3)2Fe(BiX2)] (X=Cl, Br, I), at the BP86/TZ2P/ZORA level of theory. Pauling and Mayer bond orders of the optimized structures show that the M-Bi bonds in these complexes are nearly M–Bi single bonds. The π bonding contribution is, in all complexes, significantly smaller than the corresponding σ bonding contribution, representing only 5–14% of the total orbital interaction. Thus, in these complexes, [BiX2] behaves predominantly as σ donor. The values of the Mayer bond order of the M–Bi bonds in dihalobismuth complexes suggest a significant covalent contribution to the M–Bi bonds. These observations are supported by the greater contributions of the covalent interaction energy ΔE orb than the electrostatic interactions ΔE elstat in all the dihalobismuth complexes. The absolute values of the ΔE int, ΔE orb and ΔE elstat contributions to the M–Bi bonds decrease according to X=Cl>Br>I, while the values of these energy terms increases in all four sets of complexes in the order Fe