Search results for "rhodium"
showing 10 items of 244 documents
Synthesis, structural and spectroscopic characterization of the α,ω-diammonioalkane hexabromorhodates(III) [H3N(CH2)xNH3]2[H 5O2][RhBr6]Br2 (x = 3, 4…
2002
The reaction of rhodium(III) chloride trihydrate with 1,3-diaminopropane and 1,4-diaminobutane in concentrated hydrobromic acid results in the formation of the bis(α,ω-diammonioalkane) diaquahydrogen(1+) hexabromorhodate(III) dibromides [H3N(CH2)xNH3]2[H5O2][RhBr6]Br2 (x = 3, 4). Dark red single crystals were obtained by diffusion-controlled crystallization at room temperature. Both compounds crystallize in space group type P1̄ and their structures are closely related. In view of crystal engineering they are inorganic-organic hybrid materials built up from octahedral [RhBr6]3−, simple Br− and flexible chain-like [H3N(CH2)xNH3]2+ ions with the [H5O2]+ and further Br− ions incorporated and th…
[Bis(dimethylsulphoxide) protium][trans-bisdimethylsulphoxidetetrachloroiridate(III)]
1988
Abstract [(DMSO)2H]trans-[IrCl4(DMSO)2] (DMSO = dimethylsulphoxide) has been structurally characterized. The hydrogen bonded cation [DMSOHDMSO]+ has a very short OHO bond distance (2.405 A) which compares well with that in the known rhodium analogue. The two DMSO ligands are trans on iridium and coordinate via the sulphur atoms. Earlier work had assigned the cis structure to the anion in this compound.
Hydrogen: a good partner for rhodium-catalyzed hydrosilylation
2014
The influence of hydrogen pressure on the hydrosilylation of ketones catalyzed by [((S)-SYNPHOS)Rh(nbd)]OTf has been studied. We have notably demonstrated that hydrogen significantly affected the outcome of the reaction while not being consumed as stoichiometric reducing agent. In THF, diethyl ether or toluene, the hydrogen pressure exceedingly accelerated the hydrosilylation reaction and preserved or even improved the enantioselectivity of the process. In CH2Cl2, the rhodium catalyst also showed generally higher catalytic activity under hydrogen pressure. Most serendipitously, several ketones were found to give products of absolute opposite configuration upon performing the hydrosilylation…
Synthesis, reactivity, crystal structures and catalytic activity of new chelating bisimidazolium-carbene complexes of Rh
2003
A series of new bridging, chelating and pincer N-heterocyclic carbenes of RhI and RhIII have been obtained under mild conditions. The compounds have been fully characterised and their crystal structures determined. The chelate-pincer coordination of the ligands means that the stability of these compounds is significantly greater than other carbene complexes of Rh. The compounds have been tested in catalytic reactions such as hydrogen transfer from alcohols to ketones, and hydrosilylation of terminal olefins and alkynes; they show a high activity for both processes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Analysis of the main structural trends for biscyclometalated dinuclear rhodium compounds of general formula Rh2(O2CR)2(PC)2·2H2O
2008
Abstract A new series of biscyclometalated dinuclear rhodium (II) compounds with the general formula Rh2(O2CR)2(PC)2 · 2H2O, being PC = (C6H4)P(C6H5)2, R = CH3 (1 · 2H2O), PC = [(p-CH3 OC6H3)P(p-CH3 OC6H4)2], R = CF3 (2 · 2H2O), PC = (C6H4)P[CH(CH3)2]2, R = CH3 (3 · 2H2O) and PC = (C6H4)P(C6H5)2, R = C6F5 (4 · 2H2O) has been obtained. The crystal structures for these compounds have been determined by X-ray diffraction and the main structural trends, bond lengths, bond angles and torsion angles have been analyzed, and have also been compared with the structural parameters for different analogous complexes described previously in the literature.
Diastereospecific control in the synthesis of enantiomerically pure bis-equatorial rhodium(II) catalysts by chiral phosphanes
2000
The reaction of Rh2(O2CR)4 [R = CH3, CF3] with the chiral phosphane (1S,2S,5R)-(2-hydroxy-5-isopropenyl-2-methylcyclohexyl)(diphenyl)phosphane, (+)PPh2(CH−R*−OH) or its enantiomer (1R,2R,5S)-(2-hydroxy-5-isopropenyl-2-methylcyclohexyl)(diphenyl)phosphane, (−)-PPh2(CH−R*−OH), results in the specific formation of the products (P)-Rh2(μ-O2CR)2(η1-O2CR)2{η2-(+)PPh2(CH−R*−OH)}2 [P(+)1, R = CH3; P(+)2 R = CF3] and (M)-Rh2(μ-O2CR)2(η1-O2CR)2{η2-(−)-PPh2(CH−R*−OH)}2 [M(−)1, R = CH3; M(−)2, R = CF3] in a high yield. Their synthesis, characterisation and catalytic behaviour in metal−carbenoid reactions are reported. X-ray analysis of P(+)2 and M(−)2 shows, in each case, a Rh24+ unit supported by two …
Hexaphosphine: A Multifaceted Ligand for Transition Metal Coordination
2011
We report the synthesis and characterization of the first ferrocenyl polyphosphane incorporating six phosphorus donor atoms. In this unique ligand, the cyclopentadienyl rings of the ferrocenyl backbone adopt a staggered position, which leads to a piano-stool arrangement for each of the two sets of three P atoms facing the same direction. As a consequence of its remarkable flexibility, this hexaphosphane displays versatile coordination behaviour towards metals, leading to unexpected structures of palladium and platinum bimetallic complexes. Analogous molybdenum and rhodium complexes are more classical.
Synthesis and X-ray structure of metalated Rhodium(II) catalysts with a chiral phospholane
2001
The reaction of Rh2(O2CR)4 (R = CH3, CF3) with the chiral phosphane (2S,5S)-2,5-dimethyl-1-phenylphospholane (PC*H), results in the formation of two diastereoisomers of Rh2(O2CCR)2(PC*)2, with (P) and (M) configuration. These can easily be isolated by chromatographic methods to obtain enantiomerically pure RhII compounds. Preliminary catalytic studies have shown that they induce moderate asymmetry in the cyclization of 5-aryl-1-diazo-2-pentanones and 1-diazo-5-hexen-2-one. X-ray analysis of the (M) diastereoisomer with formula Rh2(O2CCCH3)2(PC*)2 is reported. The crystallographic parameters are as follows: space group P21212 (orthorhombic) with a = 12.1347(11) A, b = 14.5870(13) A, c = 9.81…
Preparation and Oxidative Addition Reactions of 8-Oxyquinolate Rhodium(I) Complexes
1986
Abstract The preparation of new 8-oxyquinolate rhodium(I) complexes of the general formula Rh(Oq) (L) (L') is described. They undergo oxidative addition reactions with halogens and methyl iodide to give the corresponding rhodium(III) complexes. NMR measurements are used in the characterization of the compounds.
Synthesis of Cyclometalated Rhodium(III) Complexes. Study of the Carbonyl Insertion Reactions into the Rh-C Bond of the Metalocycle
1991
Abstract In this paper we report the preparation of new orthometalated rhodium(III) compounds of the formula Rh(oq)(AB)(PC), from Rh(oq)(Br)(PC)(H20), AB being a bidentade anionic ligand, oq= 8-oxyquinolate and PC = P(o-C6F4)Ph2. Their redox behaviour is also described. The reaction of Rh(Oq)(Br)(PC)(H20) [Oq = 5-Me-8-oxyquinolate (5-Meoq), 8-oxyquinolate] with carbon monoxide under pressure leads to expansion of the metalocycle ring by CO insertion into the Rh-C bond.