Rhodium phosphorus containing

The hydrogenation reaction is carried out with a substituted cinnamic acid. The acetamido group is of particular importance because it functions as a secondary complexation function in addition to the alkene functionality. In the first step the alkene co-ordinates to the cationic rhodium species (containing an enantiopure phosphine DIPAMP in Figures 4.4 and 4.5 with the chirality at phosphorus carrying three different substituents, Ph, o-An, CH2) for which there are several diasteromeric structures due to ... 

Scheme 6.1 Actual rhodium catalysts containing various phosphorus and carbonyl ligands.

Phosphorus-Containing Ring Systems. - The chiral a-diazophosphonic acid derivatives (289), (290) and (291) have been prepared from (-) ephedrine and (S,S)-N,N -dimethyl-l,2-diaminocyclohexane. Preliminary experiments suggest that the new chiral auxiliaries investigated exert little influence over the subsequent reactions of the derived rhodium (II) acetate-catalysed O-H and N-H insertion reactions. ... 

In continuous operation consecutive phosphorus-containing products are formed which also influence the activity of the rhodium center and thus contribute to the catalyst deactivation. One of the main degradation products from TPPTS is the sodium salt of m-formylbenzenesulfonic acid, which indicates the insertion of the rhodium atom into the P—C bond. The arylrhodium species in which rhodium has replaced one phosphorus atom presumably exists as a phosphido-bridged dimer which is inactive. This compound may subsequently be converted to a series of consecutive products, e.g., alkyl-diarylphosphines, which act as catalyst poisons. 

The enantioselective hydrosilylation reaction has been extended from 1-phcnylethanone to other alkyl aryl and alkyl alkyl ketones. With rhodium catalysts containing phosphorus-based ligands results similar to those from 1-phenylethanone have been obtained3-3. 

Alkyl alkyl ketones have also been enantioselectively hydrosilylated with rhodium catalysts containing phosphorus-based ligands. The results were similar to those from the reactions of 1-phenylethanone3-5. The highest value was 72% ee for the hydrosilylation of 3,3-dimethyl-2-butanone to (S)-3,3-dimethyl-2-butanol with diphenylsilane using a rhodium/Amphos system, based on the optically active aminophosphane ligand Amphos22. 

Chiral P,N-bidentate ligands in coordination chemistry and organic catalysis with participation of rhodium and palladium (P,N-bidentate phosphorus containing 4,5-dihydrooxazoles as ligands) 00UK721. 

Systems that reduce unsaturated groupings in addition to C=C or C=C, e.g., >C=0, —N=N—, —CH=N—, —N02, are [RhH2(PMe3)2L2]+, where L=solvent, and the complex RhCl3py3 in dimethylformamide solution in the presence of sodium borohydride.57 A phosphorus-containing polystyrene polymer forms a complex with rhodium on treatment with RhCl(PPh3)3 and can act as an efficient heterogeneous catalyst.58... 

We have prepared a variety of metalladendrimers from the reaction of phosphorus-containing dendrimers with various transition metal complexes. Dendritic complexes incorporating metals such as gold [28a, 57], iron [57,58,59], tungsten [58,59], rhodium [59, 60], platinum [60], palladium [61], ruthenium [62], or zirconium [63] were prepared. 

The second generation of hydroformylation catalysts consists of rhodium complexes containing phosphorus ligands, and these catalysts were developed by researchers at Celanese Corporation and then Union Carbide Corporation in the 1970s. These reactions occurred with lower pressures of CO and this class of hydroformylation was called the "low-pressure 0x0" process. This process has been industrially attractive because the lower pressure of CO reduces capital and operating costs, and tihe presence of phosphorus ligands on rhodium has allowed for the fine-tuning of rates and selectivities. 

The low-energy tum-stile rearrangement postulated by Meakin et al. [22, 23] for monophosphites has been proposed to explain the fluxional behavior of these complexes containing flexible diphosphite. It is beheved that the phosphorus atoms can easily exchange without changing the phosphorus-rhodium-phosphorus bite angle appreciably. 

Enantioseiective Reduction (Section 6.7) The most useful chiral hydrogenation catalysts involve a chiral phosphorus-containing ligand complexed with either ruthenium or rhodium. 

Phosphorus and rhodium are unusual among the elements in that they consist of atoms that naturally contain only one ratio of protons to neutrons and therefore have only one mass 31 (15 protons plus 16 neutrons) for phosphorus and 103 (45 protons and 58 neutrons) for rhodium. Such elements are called monoisotopic — each of their atoms has one (and only one) mass in each case. 

Cases of the S-coordinated rhodium and iridium are quite scarce. To complete the picture, we next consider the possibilities of S-coordination using complicated derivatives of thiophene. 2,5-[Bis(2-diphenylphosphino)ethyl]thiophene is known to contain three potential donor sites, two phosphorus atoms and the sulfur heteroatom, the latter being a rather nucleophilic center (93IC5652). A more typical situation is coordination via the phosphorus sites. It is also observed in the product of the reaction of 2,5-bis[3-(diphenylphosphino)propyl]thiophene (L) with the species obtained after treatment of [(cod)Rh(acac)] with perchloric acid (95IC365). Carbonylation of [Rh(cod)L][C104]) thus prepared yields 237. Decarbonylation of 237 gives a mixture of 238 and the S-coordinated species 239. Complete decarbonylation gives 240, where the heterocycle is -coordinated. The cycle of carbonylation decarbonylation is reversible. 

The complex ion (Figure 2.32) contains Rh2 bound cis to two phosphorus atoms (2.216 A) and more distantly to four oxygens (2.201—2.398 A), exhibiting a distortion ascribed to the Jahn-Teller effect it is paramagnetic (fi = 1.80 fiB) and exhibits an ESR spectrum (Figure 2.33) showing rhodium hyperfine coupling as the doublet for g. ... 

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