Pressure Induced Alteration and Stabilization of Intermolecular Stacking in Square-planar Osmium tetracarbonyl.

Osmium carbonyls are well known to form stable 18-electron complexes like Os(CO) , Os (CO) and Os (CO) having both bridging and terminal carbonyls. For osmium tetra-carbonyl, Os(CO) solid-state packing significantly alters the ground-state structure. The gas-phase stable see-saw geometry converts to a square-planar structure in solid state.

London Dispersion Interactions Imitate Pressure for Molecular Crystals.

The packing of molecular crystals, in which the constituent molecular units have no directional forces, is primarily controlled by weak London dispersion (LD) forces. These forces assist in stabilizing the system by bringing the molecular units into the proximity of each other. In this paper, the same effect is shown to be externally induced by pressure.

[(Flu)-(CH)-(NHC)-CH-(NHC)-(CH)-(Flu)]: an 'all-organic' hybrid and flexible ligand that enwraps a Ca pseudo-tetrahedrally.

A conformationally flexible ligand, [(Flu)-(CH)-(NHC)-CH-(NHC)-(CH)-(Flu)] (L), that offers four sequential organic donor modules and enwraps a Ca pseudo-tetrahedrally in a twisted 'S'-shape is devised. The [(L)Ca] synthesis is intriguingly stepwise involving the intermediate [(LH)Ca(HMDS)], whereas [(LH)Li(HMDS)] shows the potential for bimetallic chemistry. The bonding is illustrated by energy decomposition analyses.

Compression Produces a Square-Planar Iron Tetracarbonyl.

Iron carbonyls are known to form 18-electron complexes like Fe(CO), Fe(CO), and Fe(CO) having terminal or bridged Fe-CO bonding. Based on genetic algorithm-assisted density functional theory (DFT) calculations, it is predicted that at pressures above 2 GPa, iron tetracarbonyl, Fe(CO), attains a square-planar geometry with a 16-electron count. Compression overcomes the [Ar]4s3d ( = 2) → [Ar]4s3d ( = 0) excitation energy to stabilize a closed-shell Fe(CO) with a d-configuration.