31781-57-4Relevant articles and documents
Slow exchange of bidentate ligands between rhodium(I) complexes: Evidence of both neutral and anionic ligand exchange
Chen, Si,Manoury, Eric,Poli, Rinaldo
supporting information, p. 5820 - 5826 (2015/02/19)
The phosphine double exchange process involving [RhCl(COD)(TPP)] and [Rh(acac)(CO)(TMOPP)] (TPP = PPh3, TMOPP = P(C6H4-4-OMe)3) to yield [RhCl(COD)(TMOPP)] and [Rh(acac)(CO)(TPP)] is very rapid but is followed by a much slower process where the bidentate ligands are exchanged to yield [Rh(acac)(COD)] and a mixture of [RhCl(CO)(TPP)2], [RhCl(CO)(TMOPP)2], and [RhCl(CO)(TPP)(TMOPP)]. The exchange involving [RhCl(COD)(L)] and [Rh(acac)(CO)(L)] yields [Rh(acac)(COD)] and [RhCl(CO)(L)2], where the reaction is much faster when L = TPP than when L = TMOPP. The mixed-metal system comprising [IrCl(COD)(TPP)] and [Rh(acac)(CO)(TPP)] yields all four complexes [M(acac)(COD)] and [MCl(CO)(TPP)2], where M = Rh and Ir. This illustrates that both a neutral ligand exchange and an anionic ligand exchange occur. Possible pathways for these processes are discussed.
Exploring rhodium(I) complexes [RhCl(COD)(PR3)] (COD = 1,5-cyclooctadiene) as catalysts for nitrile hydration reactions in water: The aminophosphines make the difference
Tomas-Mendivil, Eder,Garcia-Alvarez, Rocio,Vidal, Cristian,Crochet, Pascale,Cadierno, Victorio
, p. 1901 - 1910 (2014/06/24)
Several rhodium(I) complexes, [RhCl(COD)(PR3)], containing potentially cooperative phosphine ligands, have been synthesized and evaluated as catalysts for the selective hydration of organonitriles into amides in water. Among the different phosphines screened, those of general composition P(NR 2)3 led to the best results. In particular, complex [RhCl(COD){P(NMe2)3}] was able to promote the selective hydration of a large range of nitriles in water without the assistance of any additive, showing a particularly high activity with heteroaromatic and heteroaliphatic substrates. Employing this catalyst, the antiepileptic drug rufinamide was synthesized in high yield by hydration of 4-cyano-1-(2,6- difluorobenzyl)-1H-1,2,3-triazole. For this particular transformation, complex [RhCl(COD){P(NMe2)3}] resulted more effective than related ruthenium catalysts.
Cooperative double deprotonation of bis(2-picolyl)amine leading to unexpected bimetallic mixed valence (M-I, MI) rhodium and iridium complexes
Tejel, Cristina,Del Rio, M. Pilar,Asensio, Laura,Van Den Bruele, Fieke J.,Ciriano, Miguel A.,Tsichlis I Spithas, Nearchos,Hetterscheid, Dennis G. H.,De Bruin, Bas
, p. 7524 - 7534 (2011/10/03)
Cooperative reductive double deprotonation of the complex [Rh I(bpa)(cod)]+ ([4]+, bpa = PyCH 2NHCH2Py) with one molar equivalent of base produces the bimetallic species [(cod)Rh(bpa-2H)Rh(cod)] (7), which displays a large Rh -I,RhI contribution to its electronic structure. The doubly deprotonated ligand in 7 hosts the two "Rh(cod)" fragments in two distinct compartments: a "square planar compartment" consisting of one of the Py donors and the central nitrogen donor and a "tetrahedral π-imine compartment" consisting of the other pyridine and an "imine C=N" donor. The formation of an "imine donor" in this process is the result of substantial electron transfer from the {bpa-2H}2- ligand to one of the rhodium centers to form the neutral imine ligand bpi (bpi = PyCH2N=CHPy). Hence, deprotonation of [RhI(bpa)(cod)] + represents a reductive process, effectively leading to a reduction of the metal oxidation state from RhI to Rh-I. The dinuclear iridium counterpart, complex 8, can also be prepared, but it is unstable in the presence of 1 mol equiv of the free bpa ligand, leading to quantitative formation of the neutral amido mononuclear compound [Ir I(bpa-H)(cod)] (2). All attempts to prepare the rhodium analog of 2 failed and led to the spontaneous formation of 7. The thermodynamic differences are readily explained by a lower stability of the M-I oxidation state for iridium as compared to rhodium. The observed reductive double deprotonation leads to the formation of unusual structures and unexpected reactivity, which underlines the general importance of "redox noninnocent ligands" and their substantial effect on the electronic structure of transition metals.
Direct in situ synthesis of cationic N-heterocyclic carbene iridium and rhodium complexes from neat ionic liquid: Application in catalytic dehydrogenation of cyclooctadiene
Hintermair, Ulrich,Gutel, Thibaut,Slawin, Alexandra M.Z.,Cole-Hamilton, David J.,Santini, Catherine C.,Chauvin, Yves
, p. 2407 - 2414 (2008/09/20)
A direct synthetic route to cationic N-heterocyclic carbene (NHC) complexes of rhodium and iridium from neat dialkyl-imidazolium ionic liquids (ILs) has been found. The method uses complexes bearing basic anionic ligands, [M(COD)(PPh3)X], X = OEt, MeCO2, which react with the inactivated imidazolium cation in the absence of external bases yielding one M-NHC moiety and the free protonated base. This new one-pot synthesis leaving pure, catalytically active IL solutions is faster, cleaner and more efficient than traditional syntheses of such NHC complexes. The observed reactivity also gives insight into NHC incorporation of rhodium and iridium catalyzed reactions performed in common dialkyl-imidazolium ILs. The complexes synthesised in this manner are compared with their bis-phosphine analogues in terms of activity for catalytic dehydrogenation of 1,5-cyclooctadiene and 1,3-cyclooctadiene in neat [BMIM][NTf2] as solvent. Even at high temperature, no ligand exchange reaction is observed with [(COD)M(PPh3)2] [NTf2] catalysts. As expected, the yields of all the reactions were low, iridium was much more active in C-H activation than rhodium and the NHC ligands were more stable than triphenylphosphine. For all catalysts, the isomerisation of 1,5-cyclooctadiene is the major reaction. However, the phosphine-NHC complex of iridium seems to be more selective for dehydrogenation than its bis-phosphine counterpart, which is more active in transfer-hydrogenation and less stable under the applied conditions. Different reaction conditions were tried in order to optimise selectivity for dehydrogenation over isomerisation and transfer-hydrogenation. Surprisingly, with 1,3-cyclooctadiene as substrate selectivity for dehydrogenation is much higher than with 1,5-cyclooctadiene for all catalysts.
Formation of a phosphine-phosphinite ligand in RhCl(PRR′2) [P,P-R′(R)POCH2P(CH2OH)2] and R′H from cis-RhCl(PRR′2)2[P(CH2OH) 3] via P-C bond cleavage
Lorenzini, Fabio,Patrick, Brian O.,James, Brian R.
, p. 8998 - 9002 (2008/10/09)
Reaction of RhCl(1,5-cod)(THP), where THP = P(CH2OH) 3, with several PRR′2 phosphines (R = or ≠ R′) generates, concomitantly with R′H, the derivatives RhCl(PRR′2)[P,P-R′(R)POCH2P(CH 2OH)2] in two isomeric forms. The hydrogen of the hydrocarbon co-product derives from a THP hydroxyl group which becomes an 'alkoxy' group at the residual PRR' moiety, this resulting in the P,P-chelated R′(R)POCH2P(CH2OH)2 ligand. One of the isomers of the PPh3 system, cis-RhCl(PPh3)[P, P-P(Ph) 2OCH2P(CH2OH)2], was structurally characterized (cis refers to the disposition of the P atoms with Ph substituents).
Electronic and steric effects of triarylphosphines on the synthesis, structure and spectroscopical properties of mononuclear rhodium(I)-chloride complexes
Tiburcio, Jorge,Bernès, Sylvain,Torrens, Hugo
, p. 1549 - 1554 (2008/10/09)
A systematic study of the reaction between the dinuclear complex [{Rh(μ-Cl)(η4-COD)}2], (COD = 1,5-cyclooctadiene) with 14 different triarylphosphines is presented. When two equivalents of the phosphine are employed, the main product is the mononuclear complex [RhCl(η4-COD)(PR3)], with R = 4-(OCH3)C6H4 (1), 4-(CH3)C6H4 (2), C6H5 (3), 4-FC6H4 (4), 4-(CF3)C6H4 (5), 4-ClC6H4 (6), 3-(OCH3)C6H4 (7), 3-(CH3)C6H4 (8), 3-ClC6H4 (9), 2-(OCH3)C6H4 (10), 2-(CH3)C6H4 (11) and R3 = (C6H5)2(C6F5) (12). No mononuclear complex could be isolated with the electron poor phosphines P(C6H5)(C6F5)2 and P(C6F5)3. A chemical equilibrium in solution was observed between the dinuclear and mononuclear species, with the formation of the mononuclear being disfavoured by the use of bulky and electron poor phosphines. The mononuclear complex 11, with the extremely bulky phosphine P(2-CH3C6H5)3, was undetected in solution by NMR, however could be crystallized and its molecular structure determined by X-ray diffraction and compared with the previously reported structures for 3 and 4. For complexes with isosteric phosphines (1-6), an inverse relationship between the coupling constant 1JRh-P and the electronic parameter (χ) of the phosphine was observed.
Synthesis and reactivity of fluoro complexes. Part 1. Cyclooctadiene rhodium(I) complexes
Vicente,Gil-Rubio,Bautista
, p. 2636 - 2637 (2008/10/08)
The systhesis of [RhF(COD)]n and its triphenylphosphine adduct 2, and a preliminary study of the reactivity of 2 are reported. The reactivity of the Rh-F-bond is illustrated by the reactions that lead to compounds 5 and 6. Compound 5 is the first triflouromethyl Rh(1) complex characterized by monocrystal X-ray diffraction. Both compounds 2 and 6 are initiators of the polymerization of phenylacetylene.
Reactions of catecholborane with wilkinson's catalyst: Implications for transition metal-catalyzed hydroborations of alkenes
Burgess, Kevin,Van Der Donk, Wilfred A.,Westcott, Stephen A.,Marder, Todd B.,Baker, R. Thomas,Calabrese, Joseph C.
, p. 9350 - 9359 (2007/10/02)
Reactions of catecholborane (HBO2C6H4) with RhCl(PPh3)3 (1) yield a variety of products depending on the B/Rh ratio, solvent, and temperature. Of particular relevance to catalyzed alkene hydroboration is degradation of HBO2C6H4 to B2(O2C6H4)3/'BH 3' and the dihydride RhH2Cl(PPh3)3 (3). The molecular structure of 3, determined by X-ray diffraction, has meridional phosphine ligands and cis hydrides. Catalyst systems formed from in situ addition of PPh3 to [Rh(μ-Cl)(COD)]2 (COD = 1,5-cyclooctadiene) are fundamentally different from Wilkinson's catalyst; RhCl(COD)(PPh3) forms initially, but the reaction of this with PPh3 is slow. Monitoring catalyzed hydroborations using Wilkinson's catalyst and catecholborane by multinuclear NMR spectroscopy, prior to oxidative workup, showed that alkylboranes were formed with some sterically hindered alkenes. With 2-methylbut-2-ene (24), for example, we observed significant quantities of disiamylborane, (CHMeCHMe2)2, formed via addition of 'BH3' to 24. When excess PPh3 was added to the catalyst system, however, the desired alkylboronate ester was formed in high yield. Partial oxidation of RhCl(PPh3)3 had a significant effect on product (and D-label) distributions. Detailed investigations of catalyzed additions of DBO2C6H4 to allylic silyl ethers CH2=C(Me)CRR′(OSitBuMe2) (R, R′ = H, Me) demonstrated that deuterium incorporation at the carbon bonded to boron in the primary alcohol product occurs only with freshly prepared Wilkinson's catalyst or when excess PPh3 is added to the oxidized catalyst. With freshly prepared Wilkinson's catalyst, addition of H2 (or D2) to these substrates is a significant competing reaction and appreciable catalytic formation of vinylboronate esters is also observed. The latter presumably arise via insertion of alkene into a Rh-B bond, followed by β-hydride elimination. Subsequent in situ addition of H2 (DH or D2) to these vinylboronate esters provides an alternative explanation to α-deuterium incorporation into the resulting primary alcohols.
The Structure of Crystalline trans-Dichlorobis(triphenylphosphine)rhodium(II), a Square Planar Rhodium(II) Monomer: Isolation of the Proposed Paramagnetic Impurity in Wilkinson's Catalyst
Ogle, Craig A.,Masterman, T. Craig,Hubbard, John L.
, p. 1733 - 1734 (2007/10/02)
trans-Dichlorobis(triphenylphosphine)rhodium(II), a square planar rhodium(II) monomer, has been isolated and characterized spectroscopically and crystallographically.
CATALYSIS OF HYDROSILYLATION XI. RHODIUM(I)-SILOXYALKYLPHOSPHINE COMPLEXES; SYNTHESIS, CHARACTERISTICS AND CATALYTIC ACTIVITY
Duczmal, Wojciech,Urbaniak, Wlodzimierz,Marciniec, Bogdan
, p. 85 - 92 (2007/10/02)
Rhodium(I) complexes with 1,5-cycloocatdiene (COD) and disiloxydiphosphines 2 where n = 1-3; (B-1, B-2, B-3, respectively)> and/or with trisiloxytriphosphine Ph2P(CH2)3(CH3)Si2 (C-2) were synthesized.Their composition and structure were determined using elemental analysis, molecular weight measurements and spectroscopic (IR, 1H NMR and vis) methods, and were then compared with the corresponding data for RuCl(COD)PPh3 (A) and RhCl(COD)2 (D).The analyitical and physico-chemical data all confirm the square planar geometry of the rhodium siloxyphosphine (the same as for rhodium triphenylphosphine) complexes with the general formula mZ where m =2 and Z =(CH3)2SiOSi(CH3)2 or m = 3 and Z = (CH3)2SiOSi(CH3)OSi(CH3)2. The structure is independent of the type of phosphine ligand, and the molar ratio of Rh : P is always 1 : 1. Catalytic activity of the complexes prepared was tested in the hydrosilylation of 1-hexene by triethoxysilane which showed a slight decrease in turnover number (A-C) compared with Wilkinson's catalyst (E) but the activation energies for the rhodium-siloxyphosphine complexes (B and C) are higher than those for the rhodium phosphine complexes (A and E).
