ABSTRACT
Experimental structural data for bis(terpyridine)iron(II) and a series of related iron(II) complexes, featuring either substituted terpyridine or tris-azinyl analogues of terpyridine, are presented and analyzed in terms of the Mean Absolute Deviation (MAD) from the average experimental data for each specific complex. The experimental structural data are then juxtaposed with density functional theory (DFT) calculated data obtained using various combinations of DFT functionals and basis sets, with and without the inclusion of Grimme D3 empirical dispersion correction. These diverse computational approaches yield optimized geometries that are subsequently compared against the available experimental structural data to assess their accuracy. The aim is to identify a reliable DFT method for determining the geometries of bis(terpyridine)iron(II) and its related complexes.
ABSTRACT
CONTEXT: The solvation of metal ions is crucial to understanding relevant properties in physics, chemistry, or biology. Therefore, we present solvation enthalpies and solvation free energies of the ferrous ion in water and ammonia. Our results agree well with the experimental reports for the hydration free energy and hydration enthalpy. We obtained [Formula: see text] kJ mol[Formula: see text] for the hydration free energy and [Formula: see text] kJ mol[Formula: see text] for the hydration enthalpy of ferrous ion in water at room temperature. At ambient temperature, we obtained [Formula: see text] kJ mol[Formula: see text] as the [Formula: see text] ammoniation free energy and [Formula: see text] kJ mol[Formula: see text] for the ammoniation enthalpy. In addition, the free energy of solvation is deeply affected when the temperature increases. This pattern can be attributed to the rise of entropy when the temperature rises. Besides, the temperature does not affect the ammoniation enthalpies and the hydration enthalpy of the [Formula: see text] ion. METHOD: All the geometry optimizations are performed at the MP2 methods associated with the 6-31++g(d,p) basis set of Pople. solvated phase structures of [Formula: see text] ion in water or in ammonia are performed using the PCM model. The [Formula: see text] program suite was used to perform all the calculations. The program TEMPO was also used to evaluate the temperature sensitivity of the different obtained geometries.
ABSTRACT
The oxidative addition of methyl iodide to [Rh(ß-diketonato)(CO)(PPh)3] complexes, as modal catalysts of the first step during the Monsanto process, are well-studied. The ß-diketonato ligand is a bidentate (BID) ligand that bonds, through two O donor atoms (O,O-BID ligand), to rhodium. Imino-ß-diketones are similar to ß-diketones, though the donor atoms are N and O, referred to as an N,O-BID ligand. In this study, the oxidative addition of methyl iodide to [Rh(imino-ß-diketonato)(CO)(PPh)3] complexes, as observed on UV-Vis spectrophotometry, IR spectrophotometry and NMR spectrometry, are presented. Experimentally, one isomer of [Rh(CH3COCHCNPhCH3)(CO)(PPh3)] and two isomers of [Rh(CH3COCHCNHCH3)(CO)(PPh3)] are observed-in agreement with density functional theory (DFT) calculations. Experimentally the [Rh(CH3COCHCNPhCH3)(CO)(PPh3)] + CH3I reaction proceeds through one reaction step, with a rhodium(III)-alkyl as the final reaction product. However, the [Rh(CH3COCHCNHCH3)(CO)(PPh3)] + CH3I reaction proceeds through two reaction steps, with a rhodium(III)-acyl as the final reaction product. DFT calculations of all the possible reaction products and transition states agree with experimental findings. Due to the smaller electronegativity of N, compared to O, the oxidative addition reaction rate of CH3I to the two [Rh(imino-ß-diketonato)(CO)(PPh)3] complexes of this study was 7-11 times faster than the oxidative addition reaction rate of CH3I to [Rh(CH3COCHCOCH3)(CO)(PPh3)].
ABSTRACT
[Rh((C4H3S)COCHCO(C4H3S))(CO)(PPh3)] crystals stack in one dimensional linear chains in the solid state, with slightly slipped π-stacking of the thienyl groups of one molecule and the ß-diketonato backbone of a neighbouring molecule. The observed stacking is possible due to the near planar orientation of the two aromatic thienyl groups and the ß-diketonato backbone. The experimentally observed stacking and close intermolecular contacts are in agreement with theoretical QTAIM calculated intermolecular bond paths and intermolecular hydrogen bonds between neighbouring molecules. NBO calculations revealed donor - acceptor NBO interactions between the lone pair on rhodium of one molecule and (i) the empty antibonding orbital on C-H of the nearest thienyl group of a neighbouring molecule, as well as with the (ii) the empty antibonding orbital on two carbons of the nearest thienyl group to rhodium on the neighbouring molecule.
Subject(s)
Density Functional Theory , Phosphines/chemistry , Quantitative Structure-Activity Relationship , Rhodium/chemistry , Hydrogen Bonding , Models, Molecular , Molecular Conformation , Phosphines/chemical synthesisABSTRACT
Amidato-N ligands are normally viewed as classic, strongly sigma-donating, innocent ligands. However, when coordinated to high-valent transition metal centers, tetraamidomacrocyclic ligands are often substantially non-innocent, i.e., exhibit radical character involving the amido pi-systems. Even the so-called MAC* ligand, generally considered to be an innocent ligand, is non-innocent in several of its known complexes.
