Structural characterization of the anions [Rh6(CO)15X]− [X = COEt and CO(OMe)]

doi:10.1016/S0022-328X(00)82966-6

Journal of Organometallic Chemistry

Volume 213, Issue 2, 23 June 1981, Pages C37-C40

https://doi.org/10.1016/S0022-328X(00)82966-6 Get rights and content

Abstract

The anions [Rh₆(CO)₁₅X]⁻, with X = COEt and CO(OMe), have been studied by single-crystal X-ray diffraction. They contain octahedral rhodium clusters, with mean metalmetal distances of 2.779 and 2.765 », respectively. The carbonyl stereochemistry in the two anions is similar to that of Rh₆(CO)₁₆, with one terminal CO group replaced by the X ligand. The RhC(carbomethoxy) bond distance (1.96(2) ») is significantly shorter than the RhC(acyl) distance (2.06(2) »).

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Complexes containing bridging tin- and germanium-substituted metallocarboxylate ligands from the reactions of Ph<inf>3</inf>SnOH and Ph <inf>3</inf>GeOH with Os<inf>3</inf>(CO)<inf>12</inf> in the presence of base
2011, Journal of Organometallic Chemistry
Citation Excerpt :
An empirical absorption correction based on the multiple measurement of equivalent reflections was applied by using the program SADABS. All structures were solved by a combination of direct methods and difference Fourier syntheses, and refined by full-matrix least-squares on F2, using the SHELXTL software package [16]. All non-hydrogen atoms were refined with anisotropic displacement parameters.
The first examples of bridging tin- and germanium-substituted metallocarboxylate ligands have been obtained from the reactions of Ph₃SnOH and Ph₃GeOH with Os₃(CO)₁₂ under basic conditions. Two products: Os₃(CO)₁₀(μ-η²-O=COSnPh₃)(μ-OMe), 1 (18% yield) and Os₃(CO)₁₀(μ-OMe)(μ-OH), 2 (6.9% yield) were obtained from the reaction of Ph₃SnOH with Os₃(CO)₁₂ in the presence of [Bu₄N]OH in methanol solvent. The compound Os₃(CO)₁₀(μ-η²-O=COGePh₃)(μ-OMe), 3 (7.3% yield) was prepared similarly by using Ph₃GeOH in place of Ph₃SnOH. Each of the products 1–3 were characterized structurally by single-crystal X-ray diffraction analysis. Compounds 1 and 3 each contain an μ-η²-O=COMPh₃, M = Sn or Ge ligand bridging a pair of osmium atoms in a triosmium carbonyl cluster complex.
Energy-dependent electrospray ionization mass spectrometric studies of mononuclear metal carbonyls
2005, Inorganica Chimica Acta
Energy-dependent electrospray ionization mass spectrometry (EDESI-MS) technique has been used for investigating the fragmentation of monomeric metal carbonyl complexes of general formula [M(CO)_x(COOMe)]⁻ (M = Cr, Fe, Mo, and W). The results show that in addition to the loss of CO, formaldehyde loss provides a pathway of fragmentation. Of all complexes investigated, the chromium complex exhibits the cleanest fragmentation. At very high voltages, the metal ions is either associated with a hydride or a methoxide ions.
Multinuclear NMR studies on substituted derivatives of Rh<inf>6</inf>(CO)<inf>16</inf> in solution
1998, Journal of Organometallic Chemistry
Multinuclear NMR data (¹³C, ³¹P, ¹³C–{³¹P}, ¹³C–{¹⁰³Rh} and ³¹P–{¹⁰³Rh}) for a series of mono- and di-substituted derivatives of Rh₆(CO)₁₆ containing neutral two electron donor ligands [Rh₆(CO)₁₅L, (L=NCMe, py, cyclooctene, PPh₃, P(OPh)₃,1/2(μ₂,η¹:η¹-dppe)); Rh₆(CO)₁₄(LL), (LL=cis-CH₂CMe-CMeCH₂, dppm, dppe, (P(OPh)₃)₂)] are reported; these data show that the solid state structure is maintained in solution. Detailed assignments of the ¹³CO NMR spectra of Rh₆(CO)₁₅(PPh₃) and Rh₆(CO)₁₄(dppm) clusters have been made on the basis ¹³C–{¹⁰³Rh} double resonance measurements and the specific stereochemical features of the observed long range couplings in these clusters have been studied. The stereochemical dependence of ³J(P–C) for terminal carbonyl ligands is discussed and the values of ³J(P–C) are found to be mainly dependent on the bond angles in the P–Rh–Rh–C fragment; these data enable the fine structure of the complex multiplets in the ¹³C–{¹H} and ³¹P–{¹H} NMR spectra of Rh₆(CO)₁₄ (dppm) to be simulated. Variable temperature ¹³C–{¹H} NMR measurements on Rh₆(CO)₁₅(PPh₃) reveal the carbonyl ligands in this complex to be fluxional. The fluxional process involves exchange of all the CO ligands except the two terminal CO's associated with the rhodium trans to the substituted rhodium and can be explained by a simple oscillation of the PPh₃ on the substituted rhodium atom aided by concomitant exchange of the unique terminal CO on this rhodium with adjacent μ₃-CO's.
Hydroformylation of 2,4,4-trimethyl-1-pentene catalyzed by the high nuclearity carbonyl cluster [Rh<inf>12</inf>(CO)<inf>30</inf>]<sup>2-</sup>
1997, Journal of Molecular Catalysis A: Chemical
The salt Na₂[Rh₁₂(CO)₃₀] was used for the hydroformylation of 2,4,4-trimethyl-1-pentene in tetrahydrofuran under high pressures of $CO H_{2}$ (20–120 atm) in the temperature range 300–400 K. The reaction is highly chemioselective, approaching 100% selectivity to 3,5,5-trimethylhexanal, and only traces of 2,4,4-trimethylpentane and 3,5,5-trimethyl-1-hexanol are produced. Typical turnover numbers are 100–1000 mol olefin/mol cluster. The cluster precursor was transformed into derivatives of lower nuclearity, [Rh₆(RCO)(CO)₁₅]⁻ (R = (CH₃)₃CCH₂CH(CH₃)CH₂) or [Rh₅(CO)₁₅]⁻, as shown by infrared spectroscopy. The turnover numbers increase on lowering the catalyst to olefin ratio, and the order of the reaction with CO is positive. The dependencies of the rates versus CO and catalyst concentrations suggest that, irrespective of the actual species present in solution, all the clusters behave in the same way, probably through a CO-driven equilibrium of fragmentation.
Organometallic chemistry of hexanuclear carbonyl clusters
1993, Coordination Chemistry Reviews
Aspects of the synthesis, structures, and reactivity of hexanuclear metal carbonyl clusters that contain hydrocarbyl fragments as ligands are reviewed. The synthesis of these compounds includes a wide range of techniques, but most rely on the production of reactive metal fragments which then aggregate into larger clusters. Typical methods include the treatment of metal carbonyls with a base, with heat, or both. These methods tend to lead to a range of product nuclearities, although in many cases the conditions can be optimized for a particular cluster. More rational syntheses, by ligand mediation in the coupling of smaller clusters or by capping reactions, are rarer, and they rely on the availability of suitable precursor compounds. The structures of most hexanuclear metal complexes can be predicted by electron counting and application of the Wade-Mingos rules for cluster bonding. The commonest structures are the regular octahedron, the bicapped tetrahedron, and the trigonal prism, though less symmetrical and more open clusters are also known. The reactivity of these clusters with organic fragments is reviewed according to the transition element. Specific reactions with alkenes, alkynes, and aromatic compounds are described and compared where possible. The most abundant information is available for ruthenium and osmium clusters. Ruthenium compounds tend to give products which retain the cluster geometry and have less bond activation in the ligands. Osmium compounds, in contrast, tend to lead to products with open geometries and a high degree of bond activation. The hexanuclear clusters of other transition elements are rarer, but examples involving rhodium, iridium, and rhenium are all described. The few compounds reported, however, allow no general conclusions to be drawn. A growing area of interest has been heterometallic cluster compounds, and a variety of systems are described, including molybdenum-, cobalt-, and platinum-ruthenium, and osmium-platinum systems.
Promoting effects of Se on Rh/ZrO<inf>2</inf> catalysis for ethene hydroformylation
1991, Journal of Catalysis
The positive effects of Se added to Rh/ZrO₂ catalysts in ethene hydroformylation were studied from the viewpoints of promoter effects of electronegative atoms usually regarded as poisoning atoms as well as electronic interactions with both substrate metal and adsorbed species. Se-modified Rh/ZrO₂ catalysts prepared by the reactive deposition of (CH₃)₂Se or coimpregnation method using SeO₂ were found to be active and selective for ethene hydroformylation. The Se addition promoted the formation of propanol rather than propanal, the propanol formation being increased more than 70 times at an optimumSe/Rh ratio. The propanoyl intermediates were observed at ca. 1770 cm⁻¹ converted reversibly to propionate species (bridge and bidentate) observed at 1425–1575 cm⁻¹. The ensemble of Se²⁻/Rh was suggested to promote CO adsorption and the insertion of CO to ethyl species, where there is an electronic interaction between Se²⁻ and CO or propanoyl species. The isotope effects of D2 and ¹³C¹⁸O showed the switchover of the rate-determining step for hydroformylation from the CO insertion on the Rh/ZrO₂ catalysts to the dissociative adsorption of H₂ on the SeRh/ZrO₂ catalysts. The role of Se is discussed in relation with the reaction mechanism.

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Preliminary communicationStructural characterization of the anions [Rh6(CO)15X]− [X = COEt and CO(OMe)]

Abstract

J. Organometal. Chem.

J. Organometal. Chem.

J. Chem. Soc. Chem. Commun.

Gazz. Chim. Ital.

J. Chem. Soc. (A)

Preliminary communication
Structural characterization of the anions [Rh₆(CO)₁₅X]⁻ [X = COEt and CO(OMe)]