Showing papers by "Louis J. Farrugia published in 2005"

Experimental X-ray Charge Density Studies on the Binary Carbonyls Cr(CO)6, Fe(CO)5, and Ni(CO)4

Abstract: The experimental charge densities in the binary carbonyls Cr(CO)6 (1), Fe(CO)5 (2), and Ni(CO)4 (3) have been investigated on the basis of high-resolution X-ray diffraction data collected at 100 K. The nature of the metal−ligand interactions has been studied by means of deformation densities and by topological analyses using the Atoms in Molecules (AIM) approach of Bader. A detailed comparison between the experimental results and theoretical results from previous work and from gas-phase and periodic DFT/B3LYP calculations shows excellent agreement, both on a qualitative and quantitative level. An examination of the kappa-restricted multipole model (KRMM) for Cr(CO)6, using theoretically derived structure factors, showed it to provide a somewhat worse fit than a model with freely refined κ‘ values. The experimental atomic graphs for the metal atoms in 2 and 3 were found to be dependent on the multipole model used for that atom. In the case of compound 2, restriction of the multipole populations according t...

Reactions of a {Mo16}-type polyoxometalate cluster with electrophiles: a synthetic, theoretical and magnetic investigation

Abstract: A medium-nuclearity mixed-valence polyoxomolybdate [H2Mo16O52]10− = {Mo16} (1a) was synthesized using an approach that employed protonated hexamethylenetetramine (HMTAH+) as counter ion and yielded (HMTAH)101a·34 H2O (1). The {Mo16} cluster anion exhibits significant nucleophilicity and traps electrophiles such as divalent transition metal ions, resulting in a family of isostructural compounds based on {Mo16M2}-type anions [M(H2O)8H2Mo16O52]6− (M = FeII (2), MnII (3), CoII (4)). The highly reactive nature of the {Mo16} system is also revealed by rearrangement and decomposition reactions of 1 to either slowly form a sodium-bridged heptamolybdate-based chain compound (5) when left in the reaction solution or, in the presence of very high concentrations of electrophiles, to heptamolybdate-based cluster compounds [M2(H2O)9Mo7O24]2− of the {M2Mo7}-type (M = FeII (6), MnII (7)). Compounds 1–7 were characterised by single crystal X-ray diffraction, elemental analysis, IR spectroscopy, magnetic susceptibility measurements, and density functional theory calculations.

Full paper / Mémoire Metal-metal bonding in bridged ligand systems: experimental and theoretical charge densities in Co 3 (µ 3 -CX)(CO) 9 (X =H , Cl)

Abstract: Experimental charge density studies on Co3(µ3-CX)(CO)9 (1a X=H ,1b X = Cl) have been undertaken at 100 and 115 K respectively, using Mo Ka X-radiation. The nature of the metal–metal and metal–ligand interactions have been studied by means of deformation densities and by topological analysis of the density using the atoms in molecules (AIM) approach. DFT (B3LYP/6311G**) calculations on 1a and 1b are in excellent agreement on a qualitative and quantitative level with the experimental conclusions. Within the conceptual framework of the AIM methodology, there is no direct bonding between the Co atoms, since no (3, –1) bond critical point in the density q is observed and hence no bond path exists between the metal atoms. The delocalisation indices d(Co, Co) obtained from the DFT wave-functions indicate however that there are significant indirect Co...Co interactions mediated through the bridging alkylidyne ligand. The charge concentrations on the alkylidyne C atoms in 1a and 1b are significantly different, and indicate that the bonding of this atom to the Co3 triangle is more localised in the case of1b.To cite