2-(methylamido)pyridine–borane : a tripod κ3N,H,H-ligand in trigonal bipyramidal rhodium(I) and iridium(I) complexes with an asymmetric coordination of its BH3 group

The complexes [M(κ3N,H,H-mapyBH3)(cod)] (M = Rh, Ir; HmapyBH3 = 2-(methylamino)pyridine–borane; cod = 1,5-cyclooctadiene), which contain a novel anionic tripod ligand coordinated to the metal atom through the amido N atom and through two H atoms of the BH3 group, have been prepared by treating the corresponding [M2(μ-Cl)2(cod)2] (M = Rh, Ir) precursor with K[mapyBH3]. X-ray diffraction studies and a theoretical QTAIM analysis of their electron density have confirmed that the metal atoms of both complexes are in a very distorted trigonal bipyramidal coordination environment, in which two equatorial sites are asymmetrically spanned by the H–B–H fragment. While both 3c–2e BH–M interactions are more κ1H (terminal sigma coordination of the B–H bond) than κ2H,B (agostic-type coordination of the B–H bond), one BH–M interaction is more agostic than the other and this difference is more marked in the iridium complex than in the rhodium one. This asymmetry is not evident in solution, where the cod ligand and the BH3 group of these molecules participate in two concurrent dynamic processes of low activation energies (VT-NMR and DFT studies), namely, a rotation of the cod ligand that interchanges its two alkene fragments (through a square pyramidal transition state) and a rotation of the BH3 group about the B–N bond that equilibrates the three B–H bonds (through a square planar transition state). While the cod rotation has similar activation energy in 2 and 3, the barrier to the BH3 group rotation is higher in the iridium complex than in the rhodium one

Experimental and theoretical characterization of the Zn - Zn bond in [Zn2(η5-C5Me5)2]

The existence and characterization of a bond between the Zn atoms in the recently synthesized complex [Zn2(5-C5Me5)2], as well as between Zn and ligand C atoms is firmly based on neutron diffraction and low-temperature X-ray synchrotron diffraction experiments. The multipolar analysis of the experimental electron density and its topological analysis by means of the Atoms in Molecules (AIM) approach reveals details of the Zn - Zn bond, such as its open-shell intermediate character (the results are consistent with a typical metal-metal single bond), as well as many other topological properties of the compound. Experimental results are also compared with theoretical ab initio calculations of the DFT (density functional theory) and MP2 (Mller-Plesset perturbation theory) electron densities, giving a coherent view of the bonding in the complex. For instance, charges calculated from the AIM approach applied to the atomic basin of each Zn atom are, on average, +0.72 e from both the experimental and the theoretical electron density, showing a moderate charge transfer from the metal, confirmed by the calculated topological indexes.Ministerio de Educación y Ciencia MAT2006-0199

Topological analysis of the electron density in the carbonyl complexes M(CO)8 (M = Ca, Sr, Ba)

The quantum theory of atoms in molecules (QTAIM) has been applied to the recently synthesized alkaline-earth cubic Oh-symmetric complexes Ca(CO)8 (1), Sr(CO)8 (2), and Ba(CO)8 (3). Theoretical calculations reveal that M–CO interactions in these complexes can be properly described as highly polar bonds, showing some features traditionally associated with transition-metal bonding, although with noticeable differences, as well. In this sense, δ(M–C) and δ(M···O) delocalization indexes for bonding and nonbonding interactions, electron localization funcion (ELF) analyses, source function (SF) calculations, and the interacting quantum atoms (IQA) approach, among other methodologies, produce results consistent with interactions dominated by electrostatics between the CO ligands and alkaline-earth metals, with an increasing degree of covalency on going from 1 to 3 and without any significant π-back-donation.This work has been supported by the Spanish MINECO project MAT2016-78155-C2-1-R and the Principality of Asturias Grant No. GRUP-IN-14-060.Peer reviewe

Response to “comment on ‘topological analysis of the electron density in the carbonyl complexes M(CO)8 (M = Ca, Sr, Ba)’”

The Comment by Holzmann et al. does not properly reflect the conclusions of the original article, as shown in the current response. New calculations on the title compounds, as well as on M(CO)2 (M = Ca, Sr, Ba) complexes with both D∞h and C2v symmetry, included in the current response and based not only on the Quantum Theory of Atoms in Molecules but also on the Natural Bond Orbital approach, strengthen the arguments of the original article.This work has been supported by the Spanish MINECO project MAT2016-78155-C2-1-R and the Principality of Asturias grant GRUP-IN-14-060.Peer reviewe

Ag2O versus Cu2O in the Catalytic Isomerization of Coordinated Diaminocarbenes to Formamidines: A Theoretical Study

DFT theoretical calculations for the Ag2O-induced isomerization process of diaminocarbenes to formamidines, coordinated to Mn(I), have been carried out. The reaction mechanism found involves metalation of an N-H residue of the carbene ligand by the catalyst Ag2O and the formation of a key transition state showing a μ-η2:η2 coordination of the formamidinyl ligand between manganese and silver, which allows a translocation process of Mn(I) and silver(I) ions between the carbene carbon atom and the nitrogen atom, before the formation of the formamidine ligand is completed. Calculations carried out using Cu2O as a catalyst instead of Ag2O show a similar reaction mechanism that is thermodynamically possible, but highly unfavorable kinetically and very unlikely to be observed, which fully agrees with experimental results

Ag2O versus Cu2O in the catalytic isomerization of coordinated diaminocarbenes to formamidines: A theoretical study

DFT theoretical calculations for the Ag2O-induced isomerization process of diaminocarbenes to formamidines, coordinated to Mn(I), have been carried out. The reaction mechanism found involves metalation of an N-H residue of the carbene ligand by the catalyst Ag2O and the formation of a key transition state showing a μ-η2:η2 coordination of the formamidinyl ligand between manganese and silver, which allows a translocation process of Mn(I) and silver(I) ions between the carbene carbon atom and the nitrogen atom, before the formation of the formamidine ligand is completed. Calculations carried out using Cu2O as a catalyst instead of Ag2O show a similar reaction mechanism that is thermodynamically possible, but highly unfavorable kinetically and very unlikely to be observed, which fully agrees with experimental results.This work was supported by the Spanish Ministerio de Ciencia e Innovación (Projects PID2019-109975GB-100 and MAT2016-78155-C2-1-R)

Non-covalent interactions in carbonyl complexes of Mn: A theoretical QTAIM study

Trabajo presentado al American Chemical Society (ACS) Fall National Meeting and Exposition, celebrado en San Diego, California (USA) del 25 al 29 de agosto de 2019

QTAIM analysis of the bonding in Mo-Mo bonded dimolybdenum complexes

A number of local and integral topological parameters of the electron density of relevant bonding interactions in the binuclear molybdenum complexes [Mo 2Cl 8] 4-, [Mo 2(μ-CH 3CO 2) 4], [Mo 2(μ-CF 3CO 2) 4], [Mo 2(μ-CH 3CO 2) 4Br 2] 2-, [Mo 2(μ-CF 3CO 2) 4Br 2] 2-, [Mo 2(μ-CH 3CO 2) 2Cl 4] 2-, [Mo 2(μ-CH 3CO 2) 2(μ-Cl) 2Cl 4] 2-, and [Mo 2(μ-Cl) 3Cl 6] 3- have been calculated and interpreted under the perspective of the quantum theory of atoms in molecules (QTAIM). These data have allowed a comparison between related but different atom-atom interactions, such as different Mo-Mo formal bond orders, ligand-unbridged versus Cl-bridged, CH 3CO 2-bridged, and CF 3CO 2-bridged Mo-Mo interactions, and Mo-Cl terminal and Mo - Cl bridge versus Mo-Br and Mo-O interactions. Calculations carried out using nonrelativistic and relativistic approaches afforded similar results. © 2012 American Chemical Society.This work has been supported by the Spanish MICINN FEDER Projects CTQ2010-14933, MAT2010-15094, and CSD2006-00015.Peer Reviewe

A topological analysis of the bonding in [M2(CO)10] and [M3(μ-H)3(CO)12] complexes (M = Mn, Tc, Re)

The M–M, M–H, and M–CO bonding interactions existing in the group 7 transition metal carbonyl complexes [M(CO)] and [M(μ-H)(CO)] (M = Mn, Tc, Re) have been theoretically studied under the perspective of the Quantum Theory of Atoms in Molecules (QTAIM). Several local and integral topological properties of the electron density involved in these interactions, as well as the source function (SF) and the electron localization function, have been computed. The results confirm that the metal atoms in the binuclear [M(CO)] complexes are connected through a localized M–M bond that implicates little electron density (it increases from M = Mn to Tc and Re). On the other hand, such a bonding has not been found in the trinuclear [M(μ-H)(CO)] complexes, which, instead, contain a 6c–6e bonding interaction delocalized over their six-membered M(μ-H) ring, as revealed by the non-negligible non-bonding delocalization indexes. The existence of significant CO to M π-back-donation, slightly higher in the trinuclear clusters than in the binuclear complexes, is indicated by the M···O delocalization indexes and SF calculations.This work has been supported by MINECO-FEDER projects (MAT2013-40950-R and CTQ2013-40619-P) and Gobierno del Principado de Asturias grants (GRUPIN14-060 and GRUPIN14-009).Peer Reviewe