- Sterically demanding, sulfonated, triarylphosphines: Application to palladium-catalyzed cross-coupling, steric and electronic properties, and coordination chemistry
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Tri(2,4-dimethyl-5-sulfonatophenyl)phosphine trisodium (TXPTS ·Na3) and tri(4-methoxy-2-methyl5-sulfonatophenyl)phosphine trisodium (TMAPTS·Na3) both provide more active catalysts for Suzuki and Sonogashira couplings of aryl bromides in aqueous solvents than tri(3-sulfonatophenyl)phosphine trisodium (TPPTS ·Na3). In the Heck coupling, TXPTS ·Na3 provides the most effective catalyst system. Cone angles determined from DFT-optimized structures show that both TXPTS·Na3 (206°) and TMAPTS·Na3 (208°) are significantly larger than TPPTS·Na3 (165°). The identity of the counterion had a significant effect on the calculated cone angles for these ligands. The electronic properties of these ligands determined by the CO stretching frequencies of trans-RhL2(Cl)CO complexes were identical, although calculated electronic parameters suggest subtle differences between these ligands. Similar to TPPTS·Na3, both TXPTS·Na3 and TMAPTS·Na3 react with Pd(OAc)2 in aqueous solvents to give LnPd0 complexes and the corresponding phosphine oxide. The reduction of palladium(II) by TXPTS·Na3 is significantly slower than is seen with TMAPTS·Na3 or TPPTS·Na3 at room temperature. Evidence of palladacycle complexes derived from TXPTS·Na3 and TMAPTS·Na3 by activation of an ortho-methyl substituent was also observed in ligand coordination studies and under catalytic reaction conditions.
- Moore, Lucas R.,Western, Elizabeth C.,Craciun, Raluca,Spruell, Jason M.,Dixon, David A.,O'Halloran, Kevin P.,Shaughnessy, Kevin H.
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- Carbene Complexes. Part 18. Synthetic Routes to Electron-rich Olefin-derived Monocarbenerhodium(I) Neutral and Cationic Complexes and their Chemical and Physical Properties
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Electron-rich olefins of general type C(NR)CH2CH2NR>2 (LR2; R=Me, Et, Ph, 4-MeC6H4. 4-MeOC6H4, or 2-MeOC6H4) undergo reaction with a variety of rhodium(I) precursors via ligand displacement or chloride-bridge cleavage to afford monocarbenerhodium(I) complexes, such as R)(PPh3)2>, R)>, or R)(PPh3)>>LR= =C(NR)CH2CH2NR, cod=cyclo-octa-1,5-diene>; complexes Me)(PPh3)X> Me= =CN(Me)CH2CH2CH2NMe, X= CO or PPh3> have similarly,been obtained from the olefin L'Me2.From these, further complexes may be obtained by ligand (neutral or anionic) exchange processes : trans-R(PPh3)2>, trans-R)(PPh3)2>X (X=Br, Cl, ClO4, or I), R)(PPh3)> (X=BH4 or ClO4), cis-R)> (X=Cl or NO3), R)> (X= CH2SiMe3, ClO4, or NO3), cis-R)(PPh3)>, and R)>.In many of the reactions some of these ligand displacements at RhI proceed without retention of stereochemistry and it is likely that the observed product is the thermodinamically preferred isomer.Other chemical properties of the monocarbenerhodium(I) complexes relate to (i) rare examples of the displacement of LR from Rh by PPh3 or Ph2PCH2CH2PPh2 under rather forcing conditions, and (ii) oxidative addition (not particularly facile) of HCl, Cl, or C2(CN)4.The 45 new complexes heva been characterised by analysis and spectroscopy (i.r. and 1H and 31P n.m.r.) and, where appropriate, relative molecular mass determination , and electrical conductivity.From J(31P-103Rh) coupling constants it is concluded that LR has a greater trans influence than PPh3 but a lower cis influence.
- Doyle, Michael J.,Lappert, Michael F.,Pye, Peter L.,Terreros, Pilar
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- Photochemical Behavior of Chlorocarbonylbis(triphenylphosphine)rhodium(I), ClRh(CO)P2 (P = PPh3). Laser Flash Photolysis with Infrared Detection
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Laser flash photolysis of ClRh(CO)P2 with monitoring infrared region gave definite evidence of photoelimination of CO, rather than P.ClRhP2 generated reacts with the remaining ClRh(CO)P2 to give a transient binuclear rhodium carbonyl, which regenerates ClRh(CO)P2 via the reaction with CO.
- Oishi, Shigero,Kawashima, Takeshi
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- PHOSPHINERHODIUM COMPLEXES AS HOMOGENEOUS CATALYSTS XI. DECARBONYLATION OF PRIMARY ALCOHOLS USED AS SOLVENTS UNDER CONDITIONS OF OLEFIN HYDROGENATION; A SIDE REACTION LEADING TO CATALYST DEACTIVATION
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In the hydrogenation of olefins in alcoholic solvents catalysed by phosphinerhodium complexes a hydrogen transfer reaction from the alcohols to the olefins takes place alongside the main reaction.With primary alcohols the aldehydes formed are decarbonylated and the in situ catalysts formed from 2 and phosphines are partially converted into Rh(CO)(PR3)2Cl type complexes and thereby deactivated.
- Kollar, Laszlo,Toeroes, Szilard,Heil, Balint,Marko, Laszlo
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- Remarks on the process of homogeneous carbonylation of rhodium compounds by N,N-dimethylformamide
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Reductive carbonylation of rhodium(III) chloride complexes, commercial RhCl3 · nH2O neutralized with BaCO3, (Me2NH2)2[RhCl5(DMF)], (PPh4)[RhCl4(H2/sub
- Varshavsky, Yuri S.,Cherkasova, Tatiana G.
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- Carbonylation reactions of Rh(PPh3)3Cl and Ru(PPh3)3Cl2 in the solid state
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The carbonylation reactions of Rh(PPh3)3Cl (1) and Ru(PPh3)3Cl2 (2) in the solid state with carbon monoxide at atmospheric pressure were studied; the known complexes Rh(PPh3)2(CO
- Porta, Francesca,Tollari, Stefano,Bianchi, Claudia,Recchia, Sandro
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- THE CATALYTIC SUBSTITUTION OF METAL CARBONYL AND SUBSTITUTED METAL CARBONYLS BY ISONITRILES IN THE PRESENCE OF RHODIUM(I) AND POLYMER-SUPPORTED RHODIUM(I) COMPLEXES
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Metal carbonyls and substituted metal carbonyls, under relatively mild reaction conditions, in the presence of isonitriles, undergo catalytic CO substitution by rhodium(I) and polymer-supported rhodium(I) complexes.The reaction provides a facile route to te synthesis of transition metal isonitrile complexes.
- Albers, Michel O.,Coville, Neil J.,Nicolaides, Christakis P.,Webber, Ronald A.
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- π-Coordination vs ring-opening isomerization of 2-phenyl-1-methylenecyclopropane upon the reaction with RhCl(PPh3)3
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The reactions of 2-phenyl-1-methylenecyclopropane with RhCl(PPh3)3 for 16 h at 50°C and at 0°C gave RhCl(η4-CH2=CPhCH=CH2)(PPh 3)2 (1) and RhCl-(η2-CH2=CCH2HPh)(PPh3) 2 (2) as respective isolated products. Heating of a benzene solution of 2 at 50°C turned it into 1 in a low yield (3)3 and with 2 at the same temperature afforded 1 (10%) and 2-phenyl-1,3-butadiene (14%).
- Osakada, Kohtaro,Takimoto, Hisami,Yamamoto, Takakazu
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- Insertion Reactions of the Fragment into a Phosphirene Ring, and Carbonylation of the resulting Rhodium(III) Complex. Crystal and Molecular Structures of Ph(PPh3)2>, O(PPh3)2> and the Novel Dimeric Complex O(PPh3)>2>
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The first example of insertion of the d8Rh(I) fragment into a phosphirene ring system results in a five-coordinate Rh(III) complex, which undergoes insertion of carbon monoxide to give either monomeric O(PPh3)2> or dimeric O(PPh3)>2>, the structures of which have been elucidated by NMR spectroscopy and single-crystal X-ray diffraction studies.
- Ajulu, Florence A.,Carmichael, Duncan,Hitchcock, Peter B.,Mathey, Francois,Meidine, Mohamed F.,et al.
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- Peripheral SH-functionalisation of carbosilane dendrimers including the synthesis of the model compound dimethylbis(propanethiol)silane and their interaction with rhodium complexes
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Treatment of the allyl-containing compounds Me2Si(CH 2CH=CH2)2 and MeSi(CH2CH=CH 2)3 with thioacetic acid in the presence of AIBN gave Me2Si[(CH2)3SC(O)CH3]2 and MeSi[(CH2)3SC(O)CH3]3, respectively, which were reduced with LiAlH4 to the dithiols Me 2Si[(CH2)3SH]2 (3) and MeSi[(CH 2)3SH]3 (4). This protocol was applied to the first and second generations of the doubly and triply-branched carbosilane allyl dendrimers, Si[(CH2)3SiMe(CH2-CH=CH 2)2]4 (G(1)allyl-8), Si[(CH 2)3SiMe{(CH2)3SiMe(CH 2CH=CH2)2}2]4 (G(2) ally-16), Si[(CH2)3Si(CH2CH=CH 2)3]4 (G(1)allyl-12), and Si[(CH2)3Si{(CH2)3Si(CH 2CH=CH2)3}3]4 (G(2) allyl-36) to give the corresponding SH functionalised surface dendrimers Si[(CH2)3SiMe(CH2CH 2CH2SH)2]4 (G(1)SH-8), G(2)SH-16, G(1)SH-12, and G(2)SH-36. Reactions of 3 with [M(acac)(diolefin)] (M = Rh, Ir; diolefin = 1,5-cyclooctadiene, 2,5-norbornadiene) gave the compounds of the type [M2(μ-Me 2Si[(CH2)3S]2)(diolefin) 2]n. These diolefin complexes are octanuclear (n = 4) in solution while the complex [Rh2(μ-Me2Si[(CH 2)3S]2)(cod)2]n (5) is tetranuclear in the solid state. The structure of 5, solved by X-ray diffraction methods, consists of a 20-membered metallomacrocycle formed by two dimethylbis(propylthiolate)silane moieties bridging four fragments Rh(cod) in a μ2 fashion through the sulfur atoms. Treatment of [Rh(acac)(CO)2] with 3 gave [Rh2(μ-Me 2Si[(CH2)3S]2)(CO)4] n, which is a mixture of tetra (n = 2) and octanuclear (n = 4) complexes in a 2: 1 ratio in solution, while the related complex [Rh 2(μ-Me2Si[(CH2)3S] 2)(CO)2(PPh3)2]2 is tetranuclear. Reactions of [Rh(acac)(L-L)] (L-L = cod, (CO)2, (CO)(PPh3)) with 4 and the dendrimers G(1)SH-8, G(2) SH-16, and G(1)SH-12, gave microcrystalline solids of formulae [Rh3(MeSi[(CH2)3S] 3)(L-L)3]n, [Si[(CH2) 3SiMe{(CH2)3SRh(cod)}2] 4]n ([G(1)Rh(cod)-8]n), [Si[(CH 2)3Si{(CH2)3SRh(cod)} 3]4]n ([G(1)Rh(cod)-12] n), etc., which presumably are tridimensional coordination polymers. The Royal Society of Chemistry 2005.
- Camerano, Jose A.,Casado, Miguel A.,Ciriano, Miguel A.,Tejel, Cristina,Oro, Luis A.
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- Chain initiation efficiency in cobalt- and nickel-mediated polypeptide synthesis
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In the presence of certain ligands and solvents, nickel- and cobalt- mediated living polymerizations of α-amino acid-N-carboxyanhydrides (NCAs) produce polymers with molecular weights several times greater than predicted by initial molar ratios of monomer to initiator. Such molecular weight inflation could result either from competitive formation of catalytic intermediates of reduced activity or from incomplete formation of a single catalytically active species. Evidence is presented here supporting the latter possibility. Specifically, evidence is given that the concentration of the key amido - amidate metallacyclic active species is reduced in situ by (1) complexation of metal(0) preinitiator by CO liberated upon addition of an NCA monomer to another molecule of preinitiator, (2) incomplete ring contraction of a six-membered amido - alkylmetallacyclic intermediate due to inefficient proton migration, and (3) dimerization of the amido - amidate active species to give catalytically inactive complexes.
- Deming, Timothy J.,Curtin, Scott A.
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- SYNTHESES AND 31P NMR STUDIES OF SOME CHLOROCARBONYLRHODIUM(I) COMPLEXES CONTAINING 1,3-DI-t-BUTYL-2,4-DIHALOGENOCYCLODIPHOSPHAZANES (PXNt-Bu)2(X=Cl, F) AND RELATED LIGANDS
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Syntheses of the chlorocarbonylrhodium complexes 2(PFNt-Bu)2>, trans-, x, 2 and trans- are described together with the structurally related x,
- Laurent, James C.T.R. Burckett St.,Sinclair, James,Nixon, John F.
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- 1H-Pyrrolopyridine (HL) Ligands in Rhodium(I) and Iridium(I) Chemistry. Crystal and Molecular Strucures of Rh2(μ-L)2(nbd)2> and
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Reactions of 1H-pyrrolopyridine (HL) with or compounds give molecular complexes respectively.The latter react with KOH to form binuclear complexes.Carbonylation reactions of the above compounds afford , , or . some related iridium(I) complexes are also reported.Redistribution reactions take place between and yielding complexes. the tetranuclear complex has been isolated by several routes starting from the above mono- or bi-nuclear neutral rhodium complexes.The structures of the complexes and (nbd = norborna-2,5-diene) have been determined by X-ray methods.The former crystallize in the monoclinic space group C2/c with a=16.272(4), b=7.932(2), c=19.198(5) Angstroem, β=112.07(2) deg, and Z=4.Crystals of the latter are monoclinic, space group P21/n with Z=2 and a unit cell of dimensions a=11.091(3), b=16.615(6), c=8.531(4) Angstroem, and β=91.63(3) deg.Both structures were solved by Patterson and Fourier methods and refined by fullmatrix least squares to R values of 0.072 and 0.041 respectively.The structure of the binuclear complex consists of two Rh atoms bridged by two anions L co-ordinated through the two N-atoms.Each Rh atom interacts also with the olefinic bonds of a nbd molecule.The ligand L is diordered and distributed in two positions.The structure of the tetranuclear complex consists of two binuclear units joined together through a double chlorine bridge, forming a planar Rh4Cl2 ring.In each binuclear unit a bidentate anion L and a carbonyl group bridge the two Rh atoms, which are directly bonded .
- Oro, Luis A.,Ciriano, Miguel A.,Villarroya, B. Eva,Tiripicchio, Antonio,Lahoz, Fernando J.
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- Rhodium-Complex-Catalyzed Hydroformylation of Olefins with CO2and Hydrosilane
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A rhodium-catalyzed one-pot hydroformylation of olefins with CO2, hydrosilane, and H2has been developed that affords the aldehydes in good chemoselectivities at low catalyst loading. Mechanistic studies indicate that the transformation is likely to proceed through a tandem sequence of poly(methylhydrosiloxane) (PMHS) mediated CO2reduction to CO and a conventional rhodium-catalyzed hydroformylation with CO/H2. The hydrosilylane-mediated reduction of CO2in preference to aldehydes was found to be crucial for the selective formation of aldehydes under the reaction conditions.
- Ren, Xinyi,Zheng, Zhiyao,Zhang, Lei,Wang, Zheng,Xia, Chungu,Ding, Kuiling
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supporting information
p. 310 - 313
(2016/12/30)
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- Mixed anhydride complexes of rhodium(i) and ruthenium(ii)-their synthesis and ligand rearrangements
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The coordination chemistry and solution behaviour of Rh(i) and Ru(ii) complexes derived from mixed anhydride ligands of carboxylic acids and phosphorus acids were explored. Similar to the free ligand systems, mixed anhydride complexes rearranged in solution via a number of pathways, with the pathway of choice dependent on the mixed anhydride employed, the auxiliary ligands present as well as the nature of the metal centre. Plausible mechanisms for some of the routes of rearrangement and by-product formation are proposed. Where stability allowed, new complexes were fully characterised, including solid state structures for four of the unrearranged mixed anhydride complexes and two of the interesting rearrangement products.
- Coetzee, Jacorien,Eastham, Graham R.,Slawin, Alexandra M. Z.,Cole-Hamilton, David J.
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p. 3479 - 3491
(2014/03/21)
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- Slow exchange of bidentate ligands between rhodium(I) complexes: Evidence of both neutral and anionic ligand exchange
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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.
- Chen, Si,Manoury, Eric,Poli, Rinaldo
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p. 5820 - 5826
(2015/02/19)
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- Modification of Wilkinson's catalyst with triphenyl phosphite: Synthesis, structure, 31P NMR and DFT study of trans-[RhCl(P(OPh) 3)(PPh3)2]
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The complex trans-[RhCl(P(OPh)3)(PPh3)2] (1) has been prepared and characterized by 31P NMR spectroscopy and single crystal X-ray crystallography. It was found that in the solid state there are two forms of complex 1 in the unit cell forming a cocrystal. DFT theoretical computations have confirmed the existence of the two forms and have provided evidence for the greater stability of 1 compared with Wilkinson's catalyst, [RhCl(PPh3)3] (2), in terms of the dissociation energy of the Rh-P(PPh3) bonds. On the basis of the phosphorus chemical shifts, δ P(PPh3), and the results of the theoretical computations, it is suggested that the Rh-P(PPh3) bonding interactions are slightly enhanced in 1 compared with 2. A distinct difference between complexes 1 and 2, was found to be the catalytic activity of 1 in the alkylation of allyl acetate with sodium diethylmalonate, while 2 is almost catalytically inefficient.
- Choinopoulos, Ioannis,Papageorgiou, Ioannis,Coco, Silverio,Simandiras, Emmanuel,Koinis, Spyros
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p. 255 - 261
(2013/01/13)
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- Rhodium-catalyzed cross-coupling reactions of carboxylate and organoboron compounds via chelation-assisted C-C bond activation
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A new rhodium-catalyzed decarbonylated coupling reaction of ethyl benzo[h]quinoline-10-carboxylate and organoboron compounds that occurs through chelation-assisted sp2 C-COOEt bond activation was described. In this system CuCl played a very important role, and a five-membered rhodacycle was also involved as a key intermediate. Various functionalities were compatible in the reaction, and the desired products were obtained in good to excellent yields. DFT calculations on the mechanisms of this reaction using a Rh(I) model catalyst have also been carried out.
- Wang, Jingjing,Liu, Bowen,Zhao, Haitao,Wang, Jianhui
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p. 8598 - 8607
(2013/02/23)
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- Efficient bulky phosphines for the selective telomerization of 1,3-butadiene with methanol
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A series of bulky phosphines containing substituted biphenyl, 2-methylnaphthyl, or 2,7-di-tert-butyl-9,9-dimethylxanthene moiety were prepared. They were used in the preparation of new monophosphine-palladium(0)- dvds complexes, which were employed as catalysts for the selective telomerization of 1,3-butadiene with methanol to obtain 1-methoxyocta-2,7-diene (1-MOD), the key intermediate in the Dow 1-octene process. Several ligands showed improved selectivity and yield compared to that of the benchmark ligand PPh3. Especially 2,7-di-tert-butyl-9,9-dimethylxanthen-4-yl- diphenylphosphine (4, mono-xantphos ) stands out as an excellent ligand in terms of yield, selectivity, and stability.
- Tschan, Mathieu J.-L.,Garcia-Suarez, Eduardo J.,Freixa, Zoraida,Launay, Helene,Hagen, Henk,Benet-Buchholz, Jordi,Van Leeuwen, Piet W.N.M.
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p. 6463 - 6473
(2010/07/04)
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- Synthesis of [RhCl(CO)(cyclopentadienone)]2 from [RhCl(cod)]2 and a 1,6-diyne under CO: Application to Rh(i)-catalyzed tandem [2+2+1] carbonylative cycloaddition of diynes and Claisen rearrangement
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Although Rh(i)Cl(CO)(cpd) (cpd = cyclopentadienone) complexes were identified more than 40 years ago, their exact structures have not been determined because of the polymeric nature of these complexes. We determined the structure of [Rh(i)Cl(CO)(cpd)]2, which was formed by the reaction of [Rh(cod)Cl]2 with a 1,6-diyne under CO. In addition, based on determination of the structure of the [Rh(i)Cl(CO)(cpd)]2 complex, we identified a new catalytic tandem reaction - the Rh-catalyzed [2+2+1] carbonylative cycloaddition of phenoxide-substituted diynes and Claisen rearrangement.
- Lee, Sang Ick,Fukumoto, Yoshiya,Chatani, Naoto
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p. 3345 - 3347
(2010/07/20)
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- 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
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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).
- Lorenzini, Fabio,Patrick, Brian O.,James, Brian R.
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p. 8998 - 9002
(2008/10/09)
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- Rh(I) carbonyl carboxylato complexes: Spectral and structural characteristics. Some reactions of coordinated formate group
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Complexes [Rh(μ-RCOO)(CO2)]2, where R = H, CH 3, CF3 (I, II, III, respectively) are synthesized by reacting anhydrous carboxylic acids with Rh(Acac)(CO2) crystals. In compounds I, II, III, and trans-Rh(RCOO)(PPh3)2(CO), where R = H, CH3, CF3 (IV, V, VI, respectively), ν(CO) and 1J(CRh) increase and δ13C decreases with the increasing electronegativity of R (CH3 3). In the case complexes IV, V, and VI, the values of δ31P and 1J(PRh) decrease in the same order. Complexes I and V are studied by X-ray diffraction analysis. Intramolecular (2.946 A) and intermolecular (3.127 A) Rh-Rh distances in a columnar structure I are close, i.e., the structure contains infinite chains of metal atoms. Interaction of IV with chlorinated solvents results in trans-RhCl(PPh3)2(CO). When heated with an excess of PPh3 in propanol-2, compound IV transforms to HRh(PPh3)3(CO). The latter reaction was suggested as a basis of a new method that can be used to obtain HRh(PPh 3)3(CO).
- Varshavskii,Cherkasova,Podkorytov,Korlyukov,Khrustalev,Nikol'skii
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p. 121 - 131
(2008/10/09)
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- Unexpected formation of a weak metal-metal bond: Synthesis, electronic properties, and second-order NLO responses of push-pull late-early heteronuclear bimetallic complexes with W(CO)3(1,10-phenanthroline) acting as a donor ligand
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In attempts to bridge the complex [W(CO)3(phen)(pyz)] (phen = 1,10-phenanthroline; pyz = pyrazine) to acceptor centers, either soft centers such as cis-M(CO)2CL (M = Rh(I), Ir(I)) and fac-M(CO)3Cl2 (M = Ru(II), Os(II)) or hard centers such as BF3, the pyrazine ligand is lost, while the fragment W(CO)3(phen) behaves as a σ-donor base with the unexpected formation of heteronuclear early-late bimetallic compounds with a weak metal-metal bond, as confirmed by the easy substitution of W(CO)3(phen) by soft ligands (PPh3, CO, pyridine). The X-ray structures of [(CO)3(phen)W-cis-Ir(CO)2Cl] and [(CO)3(phen)W-fac-Os(CO)3Cl2] confirm a single metal-metal bond with an halogen bridging asymmetrically the two metallic moieties and with the tungsten atom achieving a distorted (6 + 1) octahedral coordination. All the heteronuclear bimetallic complexes investigated show in their electronic spectra a new solvatochromic absorption band at around 385-450 nm in addition to the MLCT (W→π*phen) absorption band typical of [W(CO)3(phen)L] complexes (L = CO, pyz, CH3CN) and an increased, in comparison to [W(CO)4(phen)], negative nonlinear (NLO) second-order emission working with the EFISH technique with an incident wavelength of 1.907 μm. The increase is due to an additional negative contribution of the new absorption band at around 385-450 nm, as shown by a solvatochromic investigation.
- Pizzotti, Maddalena,Ugo, Renato,Dragonetti, Claudia,Annoni, Elisabetta,Demartin,Mussini
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p. 4001 - 4011
(2008/10/08)
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- Carbonyl rhodium(I) complexes containing a hydrazonic tridentate HNN′O ligand. Synthesis, X-ray structure and reactivity toward methyl iodide
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The ligand (2-pyridinecarboxaldehyde) benzoylhydrazone (HNN′O) has been reacted with [Rh2(μ-Cl)2(CO)4] in diethyl ether, isolating the carbonyl complex [Rh(κ2-HNN′)(CO)Cl] (1), where the neutral ligand coordinates the metal through the nitrogen atoms, the amidic oxygen been excluded by the coordination sphere. Repeated attempts aimed to force the ligand to an anionic tridentate coordination, both by prior deprotonation of the free ligand or deprotonation of 1, have resulted in extensive deposition of metallic rhodium. The reaction between HNN′O and [Rh2(μ-Cl)2(CO)4] in basic media and in the presence of PPh3, has led to the isolation of the complex [Rh(κ2-N′O)(PPh3)(CO)]·1/2CH 2Cl2 (2), where the anionic ligand is N′O bidentate. Compound 1 has been reacted with an excess of MeI in CH2Cl2 or THF, isolating [Rh(κ2-HNN′)(CH3CO)ClI] (4) and [Rh(κ2-HNN′)(CH3CO)(THF)ClI] (5), respectively. Although the oxidative addition step is practically instantaneous in both cases, the migratory insertion step results faster in THF, as established by liquid film IR spectroscopy. Compound 2 has been reacted with MeI in THF isolating the complex [Rh(κ2-N′O)(PPh3)(CO)(Me)I] (6), which, however, does not transform into the corresponding acyl complex. The crystal structure of complex 2·1/4CH2Cl2 has been solved.
- Pelagatti, Paolo,Vergnani, Alberto,Carcelli, Mauro,Costa, Mirco,Rogolino, Dominga,Bacchi, Alessia,Pelizzi, Corrado
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p. 235 - 241
(2008/10/08)
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- Rhodium complexes containing the hybrid P, O ligand PPh2NHC(O)Me or its anion, [PPh2N...C(...O)Me]-
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The coordination behaviour of the heterofunctional phosphine ligand PPh2NHC(O)Me towards Rh(I) is reported and examples of neutral and cationic complexes containing mono- or bi-dentate modes of coordination are found. The X-ray structure of [Rh{PPh2NHC(O)Me}(CO)Cl]·CH 2Cl2 (1·CH2Cl2) shows that the P,O-chelate is almost planar and coplanar with the Rh(I) square-plane. An unusual example of coordination is found in the dimmer [Rh{μ-PPh 2Ni...C(...O)Me}(CO)]2 (2), which contains the bidentate, anionic ligand that bridges two rhodium atoms via the oxygen; it is probable that the neutral ligand can form similar complexes, such as 11 and 12. Displacement of the P,O ligand by CO or RNC ligands occurs in 1 but not in 2.
- Braunstein, Pierre,Heaton, Brian T.,Jacob, Chacko,Manzi, Lucia,Morise, Xavier
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p. 1396 - 1401
(2007/10/03)
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- Rhodium complexes of diphenylphosphino(ethylthio)ethane
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The dimeric complex, [(OC)2Rh(μ-Cl)2Rh(CO)2], undergoes bridge splitting reaction with Ph2PCH2CH2SEt (P-S) to produce the chelated complex, [Rh(CO)Cl(P∩S)](1) (P∩S = η2- coordinated P-S), which on oxidative addition with MeI and I2 yields [Rh(COMe)ICI(P∩S)](2) and [Rh(CO)I2Cl(P∩S)](3) respectively. On the other hand, the bridge splitting reaction of the dimeric complex, [(COD)Rh(μ-Cl)2Rh(COD)] (COD = 1,5-cyclooctadiene), with P-S produces a non-chelated complex, [Rh(COD)Cl(P～S)](4) (P～S = η1- coordinated P-S). All the complexes have been characterized by elemental analyses, IR, 1H and 31P{1H} NMR spectroscopy. The catalytic activity of the complexes 1 and 4 for carbonylation of methanol is found to be higher than that of the well known species, [Rh(CO)2I2].
- Das,Konwar,Dutta
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p. 626 - 629
(2007/10/03)
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- A facile route to carbonylhalogenometal complexes (M = Rh, Ir, Ru, Pt) by dimethylformamide decarbonylation
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Dimethyl formamide (DMF) can be a convenient source of the carbonyl ligand in the coordination chemistry of rhodium, ruthenium, iridium, and platinum. We have undertaken a thorough study concerning the course of this reaction. In a first step, DMF-containing complexes are produced, which is usually accompanied by chloride redistribution. Then, upon refluxing, carbonyl species in the same oxidation state are obtained, presumably as a result of HCl-mediated DMF decomposition. Provided that water levels are kept low, reduction can occur to provide the complexes [NH2(CH3)2][RhCl2(CO) 2], [NH2(CH3)2][RuCl3(CO) 2(DMF)], [RuCl2(CO)2(DMF)2], and [NH2(CH3)2][IrCl2(CO) 2]. In the case of platinum, reduction is not effective and [NH2(CH3)2][PtCl3(CO)] is obtained. No carbonylpalladium species can be synthesized in this way, the reaction producing copious amounts of colloidal metal. Adding phosphanes to these chlorocarbonyl-containing solutions allows easy, one-step syntheses of a variety of complexes.
- Serp, Philippe,Hernandez, Marc,Richard, Brigitte,Kalck, Philippe
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p. 2327 - 2336
(2007/10/03)
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- P-N bond formation as a route to highly electron rich phosphine ligands
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Phosphines containing two N-bound pyrrolidine groups and one alkyl or aryl group are unusually electron rich σ-donor ligands when compared to either tris(N-pyrrolidinyl)phosphine or trialkyl- and triaryl-phosphines.
- Clarke,Cole-Hamilton,Slawin,Woollins
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p. 2065 - 2066
(2007/10/03)
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- A new family of acylrhodium organometallics
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The Schiff mono bases of 2,6-diformyl-4-methylphenol, 1, react with RhCl3·3H2O and PPh3 in ethanol, affording dichloro[4-methyl-6-((arylimino)methyl)phenolato-C 1,O]bis(triphenylphosphine)rhodium(III), Rh(XLsb)(PPh3)2Cl2 (5; X = H, Me, OMe, Cl). Organometallics of the type (carboxylato)[4-methyl-6-formylphenolato-C 1,O]bis(triphenylphosphine]rhodium(III), Rh(Lal)(PPh3)2(RCO2) (6; R = H, Me, Et, Ph), have been synthesized by oxidative addition of 1 to RhCl(PPh3)3 in the presence of dilute RCO2H in ethanol. Replacement of RCO2H by dilute HNO3 has afforded the nitrate analogue Rh(Lal)(PPh3)2(NO3) (7). Species of type 5 are susceptible to aldiminium → aldehyde hydrolysis in a dichloromethane-acetone-water mixture with concomitant chloride dissociation, furnishing Rh(Lal)(PPh3)2Cl (8a), from which the N-bonded nitrite Rh(Lal)(PPh3)2(NO2) (8b) has been generated metathetically. The four types of species 5-8 are interconvertible, and a possible reaction pathway involving pentacoordinate intermediates is proposed. The X-ray structures of Rh(MeLsb)(PPh3)2Cl2 (5b; bis(dichloromethane) adduct), Rh(Lal)(PPh3)2(MeCO2) (6b), Rh(Lal)(PPh3)2(NO3) (7), and Rh-(Lal)(PPh3)2(NO2) (8b) have been determined. Among these, 5b, 6b, and 7 are pseudooctahedral - the bonds trans to the acyl function being longer by 0.2-0.4 A? compared to those trans to phenolato oxygen. Complex 8b is square pyramidal, there being no ligand trans to the acyl function. In 5b iminium-phenolato (N?O, 2.66(1) A?) and in the remaining species aldehyde-phenolato (C?O, 2.86(1) A?) hydrogen bonding is present. Internal charge balance is crucial for the stability of the present organometallics.
- Pattanayak, Sujay,Chattopadhyay, Swarup,Ghosh, Kaushik,Ganguly, Sanjib,Ghosh, Prasanta,Chakravorty, Animesh
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p. 1486 - 1494
(2008/10/08)
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- [Rh(7-SPh-8-Me-7,8-C2B9H10)(PPh3)2]: A new rhodacarborane with enhanced activity in the hydrogenation of 1-alkenes
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Hydrogenation of 1-hexene is eight times faster with the rhodacarbonate complex 1 than with [RhCl(PPh3)3]. The sulfur atom bound to the open face factors the interaction of the rhodium center with the more active B-H vertices situated on this face.
- Teixidor,Flores,Vinas,Kivekas,Sillanpaa
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p. 2251 - 2253
(2008/10/09)
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- Binuclear complexes of rhodium or copper with pentamethylcyclopentadienyltricarbonyltungsten. Crystal structure of (η5-C5Me5)(CO)W(μ-CO)2Rh(PPh3)2
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The reaction of Li*> (Cp* = η5-C5Me5) with affords *(CO)W(μ-CO)2Rh(PPh3)2>, 3, which has been structurally characterised by an X-ray diffraction study, and shown to contain a short W-Rh bond of 2.5820(6) Angstroem and two semi-bridging CO ligands.Variable temperature 31P NMR spectra show that complex 3 is fluxional in solution and undergoes intramolecular interchange of inequivalent PPh3 with ΔG ca. 30 kJ mol-1 at -105 deg C.Reaction of Li*> with gives the mono-triphenylphosphine complex *W(CO)3Cu(PPh3)>, 4a, which has the same valence electron count as 3 and has been characterised analytically and by IR and NMR spectroscopy.Evidence for a related molybdenum-copper species, 4b, is also presented.The structural and spectroscopic properties of new products are discussed in relation to those of related heterobinuclear compounds.Keywords: Rhodium; Copper; Tungsten; Carbonyl; Pentamethylcyclopentadienyl; Fluxionality
- Lindsell, W. Edward,McCullough, Kevin J.,Plancq, Sabine
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p. 275 - 282
(2007/10/02)
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- Formation of anionic carbonylrhodium complexes from Wilkinson's complexes under conditions of hydroformylation of formaldehyde
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The compositions and the dynamics of transformations of carbonylrhodium complexes formed from Wilkinson's complexes, RhCl(PPh3)3, dissolved in mesitylene-N,N-dimethylacetamide (DMAA) mixtures in which the DMAA concentration varied from 0 to 100 percent, in an atmosphere of synthesis gas (pCO+H2 = 6 MPa, T = 373 K) were investigated in situ by IR spectroscopy.The anion complexes, - (x = 1, 2; y = 1, 0) and -, which are the centers of formaldehyde hydrofomylation, are produced in noticeable quantities when 100 percent DMAA is used as a solvent.Separate steps of the formation of anionic complexes from RhCl(PPh3)3 have been identified.Under the conditions of hydroformylation of formaldehyde, CH2O participates in the formation of the anionic complexes along with DMAA.
- Ezhova, N. N.,Korneeva, G. A.,Kurkin, V. I.,Filatova, M. P.,Slivinsky, E. V.
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p. 836 - 839
(2007/10/02)
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- 31P and 13C NMR investigation of the system tetracarbonyldi-μ-chlorodirhodium(I)-tertiary phosphine
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13C and 31P NMR data at low temperature prompted us to characterize cis- (3) (3a, PR3 = PPh3; 3b, PR3 = PMe2Ph), as surprisingly stable products of the reaction between 2> (1) and tertiary phosphines in toluene (P : Rh = 1).Every attempt to isolate solid 3a led to the cis- and trans- halide-bridged dimers 2> (5a) and 6a which are formed from 3a by slow decarbonylation, a process which is greatly accelerated by the evaporation of the solvent under vacuum.The analogous reaction of 1 with dimethylphenylphosphinefollows a similar pathway; in this case, however, low temperature NMR spectra allowed us to characterize the pentacoordinated dinuclear species 2> (2b) as the unstable intermediate of the bridge-splitting process.The reaction of 3 with a second equivalent of phosphine (P : Rh = 2) leads, at room temperature, to the well known product trans- (8) accompanied by evolution of CO; however our data show that when the reaction is performed at 200 K, decarbonylation is prevented and spectroscopic evidence of trigonal bipyramidal pentacoordinate (7), stable only at low temperature, can be obtained.
- Rotondo, Enrico,Battaglia, Giovanni,Giordano, Giuseppe,Cusmano, Francesca Priolo
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p. 245 - 252
(2007/10/02)
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- Synthesis and characterization of rhodium complexes (Az = 2,2-dimethyl-3-phenyl-3-allylaziridine; L = C2H4, CO, pr PPh3). Crystal and molecular structure of
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2,2-Dimethyl-3-phenyl-3-allylaziridine (Az) reacts with Cramer's complex 2> to give .This new complex is transformed by carbon monoxide into , which can be also prepared starting from 2>.The crystal and molecular structure of this carbonyl species has been fully solved by X-ray diffraction, providing the first example of a complex with bidentate aziridine.The ethylene complex reacts with one equivalent of triphenylphosphine to give .A second equivalent of phosphine does not create a monodentate aziridine, but displaces this ligand.Similar behaviour is observed with the carbonyl complex which gives free aziridine and trans-.
- Cheikh, Ridha Ben,Bonnet, Michel C.,Chaabouni, Refaat,Dahan, Francoise
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p. 217 - 228
(2007/10/02)
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- Ligand redistribution reactions of some organometallic rhodium and iridium complexes
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Ligand redistribution reactions of some organometallic rhodium and iridium complexes have been investigated and their possible reaction pathways have been discussed.
- Stang, Peter J.,Huang, Yo-Hsin
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p. 185 - 192
(2007/10/02)
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- Substitution of CO by picolines and amines in RhCl(CO)(PR3)2. Synthesis and crystal structure of cis-RhCl(3-pic)2
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The title complex, cis-RhCl(3-pic)2 (3-pic = 3-picoline), has been prepared with two other isostructural rhodium complexes, respectively with 4-picoline and CH2=CH-CH2NH2.The RhCl(3-pic)2 compond crystallizes in space group P with a = 10.531(6), b = 12.025(9), c = 15.943(8) Angstroem, α = 83.01(5), β = 79.46(4), γ = 86.33(5) deg; Z = 2.The RhCl(amine)2 complexes were obtained in the reactions of 2, 2 (cod = cycloocta-1,5-diene) or RhCl(CO)2 with amines.CO substitution by amines in RhCl(CO)(PR3)2 complexes is limited by steric properties of amine and PR3 ligands. 3-Picoline substitutes CO only in complexes with PR3 ligands with cone angle Θ 140 deg.The rate of CO substitution by 2-picoline is less than half that by 3-picoline.
- Trzeciak, A. M.,Ziolkowski, J. J.,Lis, T.
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p. 391 - 398
(2007/10/02)
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- Migration of a hydride ligand to a difluorocarbene ligand bound to rhodium. The synthesis and crystal structure of RhCl2(CF2H)(PPh3)2
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Rh(CF3)(CO)(PPh3)2 has been made by treating RhH(CO)(PPh3)3 with Hg(CF3)2, and found to display reactivity consistent with a 16 e-, d8 complex, in that it undergoes addition of a number of small molecules, including O2, X2 (X = Cl, Br, I) and MeI.Treatment of Rh(CF3)(CO)(PPh3)2 with aqueous acids results in hydrolysis of the trifluoromethyl group to a carbonyl ligand.Confirmation that this reaction proceeds via a difluorocarbene intermediate came from the reaction with dry HCl, which gave RhCl2(CF2H)(CO)(PPh3)2.A study of this reaction, by multinuclear NMR spectroscopy and 2H-labelling experiments led to the proposal of a mechanism for the formation of RhCl2(CF2H)(CO)(PPh3)2 that involves hydride migration to a cationic difluorocarbene ligand bound to rhodium.Another difluoromethyl complex RhCl2(CF2H)(PPh3)2 is formed when RhHCl2(PPh3)3 is treated with Hg(CF3)2.The crystal structure of this complex has been determined, and displays square pyramidal geometry with the CF2H ligand occupying the apical position.
- Burrell, A. K.,Clark, G. R.,Jeffrey, J. G.,Rickard, C. E. F.,Roper, W. R.
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p. 391 - 408
(2007/10/02)
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- Carbon-oxygen bond formation on rhodium centers. Synthesis, characterization, crystal structure, and reactions of trans-PhORh(CO)(PPh3)2
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The synthesis of a rhodium phenoxide is reported. The complex trans-PhORh(CO)(PPh3)2 crystallizes in the centrosymmetric monoclinic space group P21/c with a = 15.794 (3) ?, b = 11.449 (2) ?, c = 20.025 (3) ?, β = 100.220 (13)°, V = 3562 (1) ?3, and Z = 4. Diffraction data (Mo Kα, 2θ = 4.5-50.0°) were collected with a Syntex P21 diffractometer, and the structure was refined to RF = 2.8% for 5293 reflections. The structure is isomorphous with the iridium analogue. Important dimensions include Rh-P = 2.337 (1)-2.357 (1) ?, Rh-CO = 1.801 (3) ?, Rh-OPh = 2.044 (2) ?, and Rh-O-C(phenoxide) = 125.52 (19)°. This complex reacts with Ph2CHC(O)Cl to give the ester Ph2CHC(O)OPh and with MeI to give anisole, PhOMe. The formation of anisole from the rhodium phenoxide is in contrast to the failure to eliminate ethers from similar iridium complexes and is consistent with the known preference for elimination from second-row (rather than third-row) transition-metal complexes.
- Bernard, Karen A.,Churchill, Melvyn Rowen,Janik, Thomas S.,Atwood, Jim D.
-
-
- Interaction of rhodium(I) with cyclopropenones: Decarbonylation and formation of 1-rhodacyclopentene-2,5-diones and cationic oxygen σ-bound cyclopropenone complexes. X-ray crystal structure of trans-carbonylbis(triphenylphosphine)(di-tert-butylcyclopropenone)rhodium trifluoromethanesulfonate
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Cyclopropenones 5a,b react with chlorotris(triphenylphosphine)rhodium to form trans-chlorocarbonylbis(triphenylphosphine)rhodium and acetylenes 7a,b. Reactions of 5a,b with trans-chlorocarbonylbis(triphenylphosphine)rhodium result in the formation of rhodacyclopentenediones 8a,b through the insertion of both the rhodium and the carbonyl into the three-membered ring. Di-tert-butylcyclopropenone, 5c, in contrast, does not react with chlorotris(triphenylphosphine)rhodium or trans-chlorocarbonylbis(triphenylphosphine)rhodium under similar reaction conditions. All three cyclopropenones 5a-c react with trans-carbonylbis(triphenylphosphine)rhodium trifluoromethanesulfonate (triflate) to give the cationic rhodium complexes 10a-c without ring opening. However, 5a,b yield the insertion products 12a,b when the reactions are done in benzene at ca. 60°C. The X-ray crystal structure of trans-carbonylbis(triphenylphosphine)(di-tert-butylcyclopropenone)rhodium triflate, 10c, is reported.
- Song, Linsheng,Arif, Atta M.,Stang, Peter J.
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p. 2792 - 2797
(2008/10/08)
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- Metal-mediated decarbonylation and dehydration of ketose sugars
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Ketose sugars can be decarbonylated and/or dehydrated by the action of certain metal complexes. Fructose reacts with 1 equiv of RhCl(PPh3)3 (1) in N-methyl-2-pyrrolidinone (NMP) at 130°C to give furfuryl alcohol, Rh(CO)Cl(PPh3)2 (2), and a small amount of 1-deoxyerythritol. 1,3-Dihydroxyacetone consumes 2 equiv of 1, giving methane and ca. 2 mol of 2. With manno-2-heptulose the primary product is 2,7-anhydromanno-2-heptulopyranose. The mechanisms of these unusual reactions have been studied by using 13C-labeling experiments and model reactions employing Pd(II) and HCl. Attempts to make the reactions catalytic using [Rh(Ph2PCH2CH2CH2PPh 2)2]+[BF4]- in place of 1 were not successful. The use of NMP as a solvent offers some advantages in the acid-catalyzed synthesis of certain carbohydrate dehydration products, as exemplified by the conversion of manno-2-heptulose to its 2,7-anhydride and of 2-deoxyglucose to 1-(2-furanyl)-1,2-ethanediol.
- Andrews, Mark A.
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p. 2703 - 2708
(2008/10/08)
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- REACTION OF FORMALDEHYDE WITH THE WILKINSON COMPLEX IN THE PRESENCE OF CARBOXYLIC ACID AMIDES
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N,N-Dimethylacetamide and N,N-dimethylformamide react with RhCl(PPh3)3 with displacement of PPh3 and the formation of a complex with the amide.Formamide and N-propylacetamide do not form similar complexes under similar conditions.In contrast to the reaction of RhCl(PPh3)3, which leads to the formation of RhCl(CO)(PPh3)2 due to decarbonylation of CH2O, stabilization of the η2-CH2O form of the CH2O coordinated with rhodium is likely in the reaction of formaldehyde with a rhodium complex containing an N-bonded amide.Under the conditions of hydroformylation of CH2O in a solution of the Wilkinson complex in an unsubstituted amide the dominating pathway of the transformation of formaldehyde is its reaction with the solvent or the ammonia formed via decarbonylation of the unsubstituted amide.
- Korneeva, G. A.,Ezhova, N. N.,Slivinskii, E. V.,Avakyan, V. G.,Loktev, S. M.
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p. 2444 - 2447
(2007/10/02)
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- Novel Halogen Exchange Reactions between Halosilanes and Rh(I) or Ir(I) Complexes
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Vaska-type complexes such as MCl(CO)L2 (M=Rh or Ir, L= tertiary phosphine) or the Wilkinson complex RhCl(PPh3)3 underwent halogen exchange reactions with halosilanes Me3SiX (X=Br, I) to give MX(CO)L2 or RhX(PPh3)3 respectively with the formation of Me3SiC
- Yamashita, Hiroshi,Kobayashi, Toshi-aki,Hayashi, Teruyuki,Tanaka, Masato
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p. 471 - 474
(2007/10/02)
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- Syntheses, characterizations, and interconversion reactions of cis- and trans-bis(2,4-pentanedionato)diaquachromium(III) complexes. Application to the cleavage reactions of the chromium-carbon bonds in trans-(dichloromethyl and chloromethyl)bis(2,4-pentanedionato)aquachromium(III) complexes in aqueous solutions
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The geometric isomer pair of bis(2,4-pentanedionato)diaquachromium(III) complexes, [Cr(acac)2(H2O)2]X (X = ClO4-, Cl-), were prepared and characterized by elemental analysis, electronic spectroscopy, pH titration, and optical resolution. Each isomer in an aqueous solution isomerizes to give an equilibrium mixture of cis- and trans-[Cr(acac)2(H2O)2]+. The equilibrium constants of the cis-trans isomerization at I = 0 M, K = [cis isomer]/[trans isomer], were determined to be 7.7 ± 0.5 at 35°C, 7.1 ± 0.4 at 45°C, and 6.7 ± 0.4 at 53°C. Kinetic measurements were made for the cis-trans isomerization reaction. The reaction followed the first-order rate law. The rate constants of the trans to cis and cis to trans isomerizations at I = 0 M were (1.8 ± 0.1) × 10-5 and (2.4 ± 0.3) × 10-6 s-1 at 35°C and (2.3 ± 0.1) × 10-4 and (3.4 ± 0.4) × 10-5 s-1 at 53°C, respectively. On the basis of these results, the cleavage reactions of the chromium-carbon bonds in trans-[CrR(acac)2(H2O)] complexes were investigated in aqueous solutions, where R denotes dichloromethyl and chloromethyl groups. trans-[CrR(acac)2(H2O)] complexes give trans-[Cr(acac)2(H2O)2]+ ions, which isomerize to give an equilibrium mixture of cis- and trans-[Cr(acac)2(H2O)2]+ ions. In addition to these reactions, formation of [Cr(acac)(H2O)4]2+ appears to contribute to the net reaction.
- Ogino, Hiroshi,Abe, Yoichi,Shoji, Masato
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p. 986 - 989
(2008/10/08)
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- Preparation of homo- and heterobimetallic μ-η2-(C,C)-ketene complexes, FpCH2COMLn, and transformation of the bridging ketene ligand into various C2 functional groups
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Eight examples of homo- and heterobimetallic μ-ketene complexes, FpCH2COMLn [3-7: Fp = (η5-C5H5)Fe(CO)2; M = Fe, Mo, Ni, Mn, Co; L = Cp, CO, PR3], are prepared by acylation of an iron-substituted acetyl chloride with various transition-metal anions. IR studies reveal the significant contribution of a π-complex Fp+[CH2=C(O-)Fp] (10) in addition to an oxycarbene structure FpCH2C(O-)=Fp+ (11) which is well-established for mononuclear acyl complexes. As a typical example, FpCH2COFp (3a) is subjected to chemical transformations relevant to catalytic CO hydrogenation. While 3a is not susceptible to carbonylation to lead to a μ-malonyl complex, decarbonylation results in quantitative liberation of ketene molecule or ligand substitution instead of formation of a μ-methylene complex. Reduction of 3a by LiAlH4 affords C3 products as major components. Reaction of 3a with electrophiles takes place at the acyl oxygen atom to give cationic binuclear oxycarbene complexes FpCH2C(OR)=Fp+TfO- (TfO = CF3SO3) (18-20) which exhibit bimodal reactivities toward both nucleophiles and electrophiles. Hard nucleophiles attack the most electrophilic carbene center, soft nucleophiles attack the alkyl side Fp group, and electrophilic reaction takes place at the methylene terminus.
- Akita, Munetaka,Kondoh, Atsuo,Kawahara, Takashi,Takagi, Takenobu,Moro-oka, Yoshihiko
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p. 366 - 374
(2008/10/08)
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- REACTIONS OF ESTERS WITH AMINES CATALYSED BY METAL CENTRES
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In the presence of metal catalysts such as AlCl3, SnCl2, FeCl3, CuCl2*2H2O, PhCl3*3H2O, "RuCl3*3H2O" and CuCl, the reaction of the ester RCO2Et (R = Me) with an aliphatic amine R1NH2 (R1 = nPr), at 65 deg C and under a dinitrogen atmosphere gives the corresponding amide, RCONHR1, and ethanol.The catalytic activity increases with increasing acidic nature of the metal centre.Similar results have been obtained with R1 = nBu and R = Me and Et, while no reaction was observed with R1 = Ph.A complex such as Rh(PPh3)3Cl has no catalytic activity in these reactions.From the attempted reaction of CH3CO2Et with nPrNH2 in the presence of Rh(PPh3)3Cl, a yellow complex of formula Rh(PPh3)2(nPrNH2)Cl has been isolated.Its reactivity towards CO, O2, and H2 has been also investigated.
- Porta, Francesca,Pizzotti, Maddalena,Crotti, Corrado,Cenini, Sergio
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p. 475 - 478
(2007/10/02)
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- LIGATING PROPERTIES OF THIONITROSOAMINES. III. CARBONYL COMPLEXES OF RHODIUM(I) AND RHODIUM(III) CONTAINING N-THIONITROSODIMETHYLAMINE
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Me2NNS reacts with 2 to produce the complex cis-Rh(SNNMe2)(CO)2Cl (1).The latter undergoes reversible CO substitution by Me2NNS to give the complex trans-Rh(SNNMe2)2(CO)Cl (2a).Complexes 1 and 2a, in solution lose CO and Me2NNS, respectively, to give the complex trans-(μ-Cl)22 (3).Complex 1 can also be prepared by dubbling CO through a CH2Cl2 solution of Rh(SNNMe2)(diene)Cl (diene=1,5-cyclooctadiene (4a), norbornadiene (4b)) obtained by a bridge-splitting reaction of Me2NNS with 2. 1 and 2a react with EPh3 (E=P, As, Sb) to give the complexes trans-Rh(EPh3)2(CO)Cl.The complexes trans-Rh(E'Ph3)2(CO)X (X=Cl, E'=As, Sb; X=Br, NCS, E'=As) undergo reversible E'Ph3 displacement upon treatment with Me2NNS to give the complexes trans-Rh(SNNMe2)2(CO)X (X=Cl (2a), Br(2b), NCS (2c)).Oxidative additions of Br2, I2, or HgCl2 to 2a produce stable adducts, while the reaction of 2a with CH3I gives an inseparable mixture of the adduct Rh(SNNMe2)2(CO)(CH3)ClI and the acetyl derivative Rh(SNNMe2)2(CH3CO)ClI.A mixture of the acetyl derivative (μ-Cl)22 and the adduct (μ-Cl)22 is obtained by treating 1 with CH3I.The IR spectra of all the compounds are consistent with S-coordination of Me2NNS.Because of the restriced rotation around the N-N bond, the 1H NMR spectra of the new compounds exhibit two quadruplets in the range 3.5-4.3δ when 4J(HH)=0.7-0.5 Hz.When 4J(HH)0.5 Hz, the perturbing effect of quadrupolar relaxation of the 14N nucleus obscures the spin-spin coupling and two broad signals are observed in the range 3.6-4δ.
- Tresoldi, Giuseppe,Sergi, Sergio,Schiavo, Sandra Lo,Piraino, Pasquale
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p. 369 - 376
(2007/10/02)
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- Thermal and photolytic reactions of nitrosyl-carbonyl complexes of rhodium and iridium with triphenylphosphine
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The photolysis of [Rh(NO)(CO)(PPh3)2] in the presence of PPh3 in dichloromethane results in the expulsion of NO rather than CO and the formation of trans-[Rh(CO)Cl(PPh3)2]. The thermal reaction and photoreaction of [Ir(NO)(CO)Cl(PPh3)2]BF4 (1) with PPh3 lead to dissociation of NO and the formation of the Ir(II) radical [Ir(CO)Cl(PPh3)3]BF4 (2). The demonstration of the homolytic cleavage of the Ir-NO bond of 1 provides support for the proposal that the photodissociation of NO instead of CO in the compounds [M(NO)(CO)(PPh3)2] (where M is Rh or Ir) proceeds from a charge-transfer state that has a bent M-N-O bond.
- Kubota, Mitsuru,Chan, Michael K.,Boyd, David C.,Mann, Kent R.
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p. 3261 - 3264
(2008/10/08)
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- Synthesis and Chemistry of trans-2> (X = Anionic Ligand, L = Tertiary Phosphine)
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The novel preparation of a wide variety of trans-2> complexes (X = anionic ligand, L = tertiary phosphine) from , phosphine (L), and acid (HX) is described.A plausible formation pathway is proposed.The electron density on the phosphorous atom in trans-2> decreases and the length of the Rh-P bond increases with an increase in the electronegativity of the anionic ligand, X, in a cis position to the phosphine ligand.The rhodium complexes (X = arylcarboxylate) are reduced to afford rhodate anions such as - and - in hexamethylphosphoroamide solution under CO-H2.The rate of reduction increases with a decrease in the electron-withdrawing effect of the arylcarboxylate ligand.
- Ohgomori, Yuji,Yoshida, Shin-ichi,Watanabe, Yoshihisa
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p. 2969 - 2974
(2007/10/02)
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- ANIONIC AND NEUTRAL RHODIUM(I) COMPLEXES CONTAINING TRICHLOROSTANNATO LIGANDS
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The complexes Et4N (diolefin=COD or NBD) have been isolated and their reactions studied.Reaction with arylic tertiary phosphines led to SnCl3(1-) displacement and isolation of neutral pentacoordinated Rh(SnCl3)(diolefin)(PR3)2 c
- Garcia, V.,Garralda, M. A.,Zugasti, E.
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p. 249 - 256
(2007/10/02)
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- Reaction Dynamics of the Tricoordinate Intermediates MCl(PPh3)2 (M = Rh, or Ir) as Probed by the Flash Photolysis of the Carbonyls MCl(CO)(PPh3)2
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Reported is a kinetics flash photolysis investigation of the rhodium(I) complex RhCl(CO)(PPh3)2 in benzene solution.These results are interpreted in terms of the transient formation of the unsaturated species RhCl(PPh3)2 (A), an intermediate crucial to proposed mechanisms of Wilkinson's catalyst reactions such as olefin hydrogenation, but which has not been the subject of previous direct investigation.Kinetics of the dimerization of A and of the reactions of this transient with CO, C2H4, PPh3, and H2 are also described.The second-order rate constant for the reaction with H2 is 1.0E5/M.s in good agreement with the value >7E4/M.s estimatted by Halpern and Wong (J.Chem.Soc., Chem.Commun. 1973, 629) from kinetics investigations of the hydrogenation of RhCl(PPh3)3.Furthermore, the equilibrium constant for triphenylphosphine dissociation from RhCl(PPh3)3 can be calculated as 2.3E-7 M from the ratio of the first-order dissociation rate constant 0.68/s determined by those workers and the second-order rate constant 3.0E6/M.s for the back reaction determined here.Rates of the subsequent reactions of other adducts formed from A and various ligands with the CO liberated in the flash experiment were also determined.Flash photolysis studies of the iridium(I) analogue IrCl(CO)(PPh3)2 in benzene demonstrated CO photolabilization in this case as well.The back reaction of the resulting transient species IrCl(PPh3)2 with CO displayed second-order kinetics with the respective rate constant 2.7E8/M.s.These results are discussed in terms of the catalytic mechanisms involving such species.
- Wink, David A.,Ford, Peter C.
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p. 436 - 442
(2007/10/02)
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- Preparation and Properties of tetrahedro-Tetraphosphorus Complexes of Rhodium and Iridium. Molecular and Electronic Structure of 2-P4)(PPh3)2>
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White phosphorus dissolved in dichloromethane or diethyl ether at -78 deg C reacts with the Rh(I) or Ir(I) complexes (M = Rh, X = Cl, Br, I, L = PPh3; M = Rh, X = Cl, L = P(p-tol)3, P(m-tol)3, AsPh3; M = Ir, X = Cl, L = PPh3) to form yellow or orange tetrahedro-tetraphosphorus complexes . 31P NMR spectroscopy of in CD2Cl2 at low temperatures shows the P4 ligand to be η2-coordinated and deshielded by ca. 240 ppm relative to free P4.The P4 units act as A2B2 spin systems coupling to two 31P nuclei of PPh3 ligands (X2) and to 103Rh (I = 0.5) to give an overall A2B2MX2 spin system.The vibrational frequencies of the P4 molecule in the rhodium complexes have been identified by infrared and Raman spectroscopy and are found to be from 15 to 90 cm-1 lower in energy than the corresponding frequencies in free P4.An X-ray structure determination on *2CH2Cl2 at 185 K shows the crystals to be triclinic, space group P1, with a = 11.853(2) Angstroem, b = 12.568(8) Angstroem, c = 14.505(2) Angstroem, α = 104.41(4) degree, β = 103.42(13) degree, γ = 84.22(4) degree, V = 2033.5(19) Angstroem3, D0 = 1.58 g cm-3, Z = 2, and Dc = 1.562 g cm-3.The P4 molecule is η2-bonded to the rhodium atom (mean Rh-P = 2.293 Angstroem) with the metal-bonded P-P edge standing perpendicular to the remaining coordination plane of the metal.The phosphine ligands are bent away from the tetraphosphorus group toward the chlorine ( support the analogy between η2-bonded P4 and η2-bonded alkene or S2; the "back-bonding" component may be traced to a three-orbital-four-electron interaction between P4 and the RhCl(PH3)2 fragment.Xα calculations show that the most important contribution to the Rh-P4 covalent bond comes from an equatorial in-plane ? overlap of Rh4dyz with a P4 2P?* orbital.There is also a contribution from ? overlap of an Rh(4dz2, 4dx2-y2, 5s) hybrid orbital with a P4 2P(p?, ?, s?) hybrid.The calculated P-P bond order is 0.4 for the bonded edge and 1.0 for the opposite tetrahedral edge of the P4 ligand.In an EPA glass at liquid nitrogen temperature (X = Cl, Br) shows five absorptions in the 700-260-nm region.These are assigned to one-electron transitions, with good agreement between the obdserved and calculated energies.The absorptions owe most of their intensity to metal -> P4 and metal -> phosphine charge transfer.
- Ginsberg, Alvin P.,Lindsell, W. Edward,McCullough, Kevin J.,Sprinkle, Charles R.,Welch, Alan J.
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p. 403 - 416
(2007/10/02)
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