Direct location of the interstitial hydride ligand in [HRu6(CO)18]? by both X-ray and neutron analyses of [Ph4As][HRu6(CO)18]

Abstract

The proposed interstitial location of the hydride ligand in [HRu,(CO),,]-has been established by X-ray and neutron analyses of [Ph,As] [HRu,(C0),,] ALTHOUGH the interstitial nature of hydrogen in binary metal hydrides is well established,l the anion [HRu,(CO),,]-(1) was the first polynuclear carbonyl in which an interstitial hydrogen atom was detected.2 For this compound

Gas-Phase Synthesis and Structure of Wade-Type Ruthenium Carbonyl and Hydrido Carbonyl Clusters

“…In the condensed phase, the hydrido carbonyl cluster HRu 6 (CO) 18 – has been synthesized, and X-ray diffraction as well as infrared spectroscopic experiments revealed an octahedral metal core structure with an interstitial H atom. − As discussed above, the positive charge of Ru 6 (CO) 18 + leads to a VE count that corresponds to a bicapped tetrahedral Wade motif of the cluster core geometry instead of an octahedral. The bicapped tetrahedral Wade structure is preserved upon CO to D 2 exchange because the number of electrons does not change.…”

Syntheses, Structures, FAB Mass Spectra, and Magnetic Properties of Chromium Chalcogenide Cluster Complexes [Cr6Se8(PEt3)6], [Cr6Se8(H)(PEt3)6], and [Cr6S8(H)(PEt3)6]

“…These lengths are slightly longer than those of [Cr 2 (CO) 10 ( μ -H)] - (1.73 Å (average)) and [Cp‘ ‘ 4 Cr 4 ( μ -H) 5 ( μ 3 -H) 2 ] (where Cp‘ ‘ = η 5 -tetramethyl-ethyl-cyclopentadienyl) (1.79 Å ( average)) . There have been several precedent examples of the interstitial hydride in the octahedral metal clusters. − The existence of an interstitial hydrogen atom in the Cr 6 octahedron is supported also by its reactivity (vide infra).…”

High Hydride Count Rhodium Octahedra, [Rh6(PR3)6H12][BArF4]2: Synthesis, Structures, and Reversible Hydrogen Uptake under Mild Conditions

“…DFT calculations (vide infra) also suggest a mixture of bridging and semi-bridging hydrides, with four octahedral edges bridged symmetrically and the remaining eight bridged unsymmetrically, supporting such a structural assignment. Of course, a neutron diffraction study would help pin down the positioning of the hydrides, as it has for cluster hydride ligands previously, − and attempts are currently underway to produce crystals of a size suitable for such an experiment.

2 Solid-state structure of cationic cluster 1a showing the cluster core (phosphine alkyl groups have been omitted for clarity).

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“…To our minds, the only plausible structure that accounts for this observation is one that invokes an interstitial hydride with 15 hydride ligands decorating the outside of the Rh 6 octahedron. Interstitial hydrides are well-known in transition metal clusters and have been characterized by NMR spectroscopy and, in some cases, neutron diffraction techniques. ,, The chemical shift of interstitial hydrides can vary over a considerable range, for example δ +16.4 ppm for [HRu 6 (CO) 18 ] - 68 to δ −26.9 ppm for [HNi 12 (CO) 21 ] - , and it has been suggested that hydrides that are located in the center of a regular octahedron show the lowest-field chemical shifts, while those more asymmetrically orientated have high-field chemical shifts . For 2b , an X-ray study (vide infra) shows a rather distorted octahedron, and thus a chemical shift observed for the unique hydride around δ −29 ppm is not unreasonable.…”