Rhodium tetracarbonyl

The spectroscopic and kinetic data from this reaction indicated the existence of a long sought catalytic reaction topology, bimetallic catalytic binuclear elimination. The kinetic data provided a linear-bilinear form in organometallics [95]. One term represented the classic unicyclic rhodium catalyzed hydroformylation and the other represented the attack of manganese hydride carbonyl on an acyl rhodium tetracarbonyl species. A representation of the interconnected topology is shown in Figure 4.12. 

Cl2NbC oH,o, Niobium(IV), dichlorobis(Ti -cyclopentadienyl)-, 28 267 Cl2Nd2Si4C44Hg4, Neodymium, tetrakis[Ti -l,3-bis(trimethylsilyl)cyclopenta-dienyl]di-p-chloro-di-, 27 171 CljNi, Nickel dichloride, 28 322 Cl204Rh2C4, Rhodium, tetracarbonyl-dichlorodi-, 28 84... 

Liu G, Volken R, Garland M (1999) Unmodified rhodium-catalyzed hydroformylation of alkenes using tetrarhodium dodecacarbonyl. The infrared characterization of 15 acyl rhodium tetracarbonyl intermediates. Organometallics 18(17) 3429-3436... 

High-pressure in situ ETIR and polymer matrix techniques were used to study the rhodium-catalyzed hydroformylation of 1-octene, 1-butene, propene, and ethene using Rh(acac)(CO)2 or Rh(acac)(CO)(PPh3) in a polyethylene matrix as the catalyst precursor. The acyl rhodium intermediates, RC(=0)Rh(C0)4 and RC(=0)Rh (CO)3(PPh3), were observed. It was found that the acyl rhodium tetracarbonyl intermediates easily react with ethene to form acyl rhodium tricarbonyl species RC(=0)Rh(C0)3(C2H4) [61]. Deuterioformylation of l-phenyl-l-(n-pyridyl)-ethenes in the presence of a phosphane-modified Rh4(CO)i2 as catalyst precursor was carried out at 100 bar of CO D2 = 1 1 and 80 °C at partial substrate conversion. On basis ofa direct NMR analysis of the crude reaction mixture, it was concluded that the branched alkyl rhodium intermediate is almost exclusively formed [62]. 

In contrast to triphenylphosphine-modified rhodium catalysis, a high aldehyde product isomer ratio via cobalt-catalyzed hydroformylation requires high CO partial pressures, eg, 9 MPa (1305 psi) and 110°C. Under such conditions alkyl isomerization is almost completely suppressed, and the 4.4 1 isomer ratio reflects the precursor mixture which contains principally the kinetically favored -butyryl to isobutyryl cobalt tetracarbonyl. At lower CO partial pressures, eg, 0.25 MPa (36.25 psi) and 110°C, the rate of isomerization of the -butyryl cobalt intermediate is competitive with butyryl reductive elimination to aldehyde. The product n/iso ratio of 1.6 1 obtained under these conditions reflects the equihbrium isomer ratio of the precursor butyryl cobalt tetracarbonyls (11). 

For tetranuclear cluster complexes, three stmcture types are observed tetrahedral open tetrahedral (butterfly) or square planar, for typical total valence electron counts of 60, 62, and 64, respectively. The earliest tetracarbonyl cluster complexes known were Co4(CO)22, and the rhodium and iridium analogues. The... 

OsN2WC,oH,o, Tungsten, tetracarbonyl[(di-ethylamino)methylidyne](isocy-anato)-, irons-, 26 42 05P2RhC45H7i, Rhodium(I), carbonyl(hy-drogen phthalato)bis(tricyclohexyl-phosphine)-, 27 291... 

Rhodium (I) carbonyl chloride (di- x-chloro-tetracarbonyl dirhodium I, [Rh (CO)2CI]2) [14532-22-9] M 388.8, m 121", 124-125". This catalyst is soluble in most organic solvents, but not pet ethers, and forms orange-red crystals from hexane. It sublimes at 80 /0.1mm to a red solid. It decomposes on exposure to air when in organic solvents but the solid is stable in dry air. It is moisture sensitive and should be stored in ampoules under N2 or Ar. It catalyses ring-opening silylformylation of olefins. [McCleverty Wilkinson Inorg Synth 8 211 1966, Dahl et al. J Am Chem Soc 83 1761 7967, Cramer Inorg Synth 15 14 1974, Fukumoto et al. J Org Chem 58 4187 1993, Colton et al. Aust J Chem 23 1351 1970.]... 

For the analogous carbonyl radicals M(CO) (M = Rh, Ir n = 1 —4), Zhou and Andrews found different symmetries for the tricarbonyls and tetracarbonyls species both with rhodium and iridium.164 Unlike Co(CO)3, which is a trigonal D3h structure, the Rh and Ir tricarbonyls have T-shaped structures with C2V symmetry. The tetracarbonyls of Rh and Ir also reveal a different order of thermodynamic stability. While for Co(CO)4, the C3v structure is the ground state and the D2d complex is higher in energy, for Rh and Ir, a reverse relationship was indicated. 

Table 9.8 gives economic data about Oxo synthesis on propylene for processes using cobalt tetracarbonyl hydride phosphine-modified cobalt and phosphine-modified rhodium catalysts. 

Rhodium carbonyl chloride Dirhodium tetracarbonyl dichloride C4Cl204Rh2 14623-22-9 388.768 red-oran cry 124 S OS... 

Br2MoC4, Molybdenum(ll), dibromo-tetracarbonyl-, 28 145 04CgH4, Phthalic acid, rhodium complex, 27 291... 

An interesting series of dicarbonyl complexes of rhodium(I) containing singly charged bidentate ligands like cupferron has been synthesized by three different routes, i.e. (i) from tetracarbonyl- i,/i -dichlorodirhodium(I), (ii) from solutions of rhodium chloride in DMF under reflux and (iii) from a carbonylated solution of rhodium chloride in boiling absolute alcohol. These dicarbonyls react with PPhj, AsPhj and SbPhj to yield monocarbonyl derivatives. 

Concerning pyrazoles, substitution of a in the 4-position by an (ethylamino)methyl or an (isopropylamino)methyl group provides the ligand and the bridged dirhodium complexes with a good solubility, presumably because the ammonium function introduced does not interact with the rhodium centers as represented for the tetracarbonyl complex (2) [17]. 

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