Synthesis, reactivity and catalytic properties of rhodium complexes of (R,R)-1-benzyl-3,4-dithioetherpyrrolidines (original) (raw)
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Journal of Molecular Catalysis A: Chemical, 2009
The products resulting from the progressive addition of pyridine (py) to a solution of [Rh 2 (µ-Cl) 2 (CO) 4 ] 1 have been found to depend both upon the solvent and the atmosphere (CO or N 2 ). In CH 2 Cl 2 under N 2 , cis-[Rh(CO) 2 Cl(py)] 2, [Rh(CO) 2 Cl(py) 2 ] 3 and [Rh 2 (µ-CO) 3 Cl 2 (py) 4 ] 4 were obtained successively; under CO, 4 was converted into 3 and under N 2 disproportionation of 4 slowly occurred to give 3 and trans-[Rh(CO)Cl(py) 2 ] 5 which reacted with CO to give 3. In more polar solvents (thf or MeOH), 1 reacted under N 2 to give the lightly solvent-stabilised complex [Rh(CO) 2 Cl(solv)] 6 (solv = thf a or MeOH b) and, in the presence of AgClO 4 , cis-[Rh(CO) 2 (solv) 2 ] ϩ 7 (solv = thf a or MeOH b); additionally, when solv = MeOH there was spectroscopic evidence for the formation of [Rh 2 (µ-CO) x (MeOH) y ] 2ϩ 8 (x = 2, y = 4 or x = 3, y = 6) which reacted with CO to give [Rh(CO) 2 (MeOH) 2 ] ϩ . Complex 7 reacted with py to give successively cis-[Rh(CO) 2 (py) 2 ] ϩ 9 and [Rh(CO)(py) 3 ] ϩ 10; under CO 10 was converted into 9. The stereochemistry of all the above complexes has been established through a combination of IR and multinuclear ( 13 C, 15 N, 103 Rh) NMR measurements and X-ray crystallography for 2 and 4. Analogous reactions have been carried out using trans-
Dalton Transactions, 2013
The synthesis, structure determination and oxidative stability of novel Rh-NHC complexes which feature pyridine-derived ligands have been described. All complexes described herein were synthesized from common dinuclear precursors of general structure [Rh(NHC)(L)Cl] 2 , where L is a monodentate olefin. We demonstrate that the use of these precursors is critical for the formation of all complexes since related cyclooctadiene containing precursors ([Rh(NHC)(COD)Cl]) were completely unreactive under identical conditions. We further demonstrate that complexes with the general formula [Rh(NHC)(olefin)(Py)Cl] or ([Rh(NHC)(BiPy/Phen)Cl]) are extremely sensitive to oxygen, reacting initially to give an adduct with dioxygen, and then decomposing further. The series of compounds and their oxidation products gave a remarkable range of colours which may be useful in the preparation of colourometric oxygen sensors. † Electronic supplementary information (ESI) available. CCDC 886710-886713 and 886734. For ESI and crystallographic data in CIF or other electronic format see CH 3 ). Calc m/z for C 34 H 45 N 3 Rh (M − Cl): 598.26, found: 597.86. Preparation of [Rh(IPr)(Bpy)Cl] (5) Procedure (a) from [Rh(IPr)(C 2 H 4 )Cl] 2 . A solution of 2,2′bipyridine (BiPy) (7.08 mg, 0.045 mmol) in 2 mL of THF was added dropwise to a stirring solution of [Rh(IPr)(C 2 H 4 )Cl] 2 (1) (25.0 mg, 0.023 mmol) in 3 mL of THF. The reaction mixture immediately turned a deep dark green-blue colour. The
2007
The thiols,1-phenylethanothiol 1 and 2,4-pentanodithiol 2 were synthesised and used to prepare binuclear rhodium species 3, 4 of the type [Rh 2 (μ−L) n (cod) 2 ] (L = 1, n = 2; L = 2, n = 1; cod = 1,5cyclooctadiene). NMR and FAB + mass spectrometry data are consistent with a binuclear structure for the species. These complexes, plus PPh 3 or diphosphines (dppp, dppb), were used as catalytic precursors for the hydroformylation of styrene under mild conditions. Fairly good activities and regioselectivities were achieved for catalytic system 3/ PPh 3.
Journal of Organometallic Chemistry, 2006
A series of [Rh(COD)(X 2-bipy)]BF 4 complexes (COD = 1,5-cyclooctadiene; X 2-bipy = 4,4 0-disubstituted 2,2 0-bipyridines; X = OCH 3 , CH 3 , H, Cl or NO 2) has been prepared from [Rh(COD)Cl] 2. The complexes for X = OCH 3 , Cl and NO 2 have not been described previously in the literature. All complexes have been characterised by elemental analysis, IR, 1 H NMR and UV-Vis spectrometry. This series of complexes presents a wide variation on electron density over the metal centre with virtually no variation on its steric environment which discloses interesting possibilities for catalytic and electro-catalytic studies. A preliminary evaluation of these complexes on the hydroformylation of camphene and b-pinene showed that under the rather drastic conditions employed the complexes acted as a precursor for [Rh(CO) 3 H], which accounts for most of the catalytic activity.
Synthesis and characterization of cationic rhodium(I) dicarbonyl complexes
Inorganica Chimica Acta, 2011
This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright
Inorganica Chimica Acta, 2011
This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright
Inorganic Chemistry, 1996
Tetranuclear diolefin complexes of the general formula [M 4 (µ 4 -PyS 2 ) 2 (diolefin) 4 ] [M ) Rh, diolefin ) 1,5-cyclooctadiene (cod) (1), 2,5-norbornadiene (nbd) (2), tetrafluorobenzobarrelene (tfbb) (3); M ) Ir, diolefin ) cod (4), PyS 2 ) 2,6-pyridinedithiolate) are prepared in high yield by reaction of the appropriate complex [{M(µ-Cl)(diolefin)} 2 ] with the salt Li 2 PyS 2 generated "in situ". This method is also used to prepare [Pd 4 (µ-PyS 2 ) 2 (allyl) 4 ] (5). Alternative syntheses for these complexes are also described. The structure of 1 was conclusively determined by a single-crystal X-ray analysis. Complex 1 crystallizes in the monoclinic system, space group C2/c, with a ) 10.252(1) Å, b ) 17.023(2) Å, c ) 23.114(3) Å, ) 99.50(1)°, and Z ) 4. Refinement by full matrix least-squares gave final R ) 0.028 and R w ) 0.024. Complex 1 is tetranuclear with two S,N,Stridentate 2,6-dimercaptopyridine ligands bridging all of the four metallic centers and presents a crystallographically imposed C 2 symmetry relating two "Rh 2 (µ 4 -PyS 2 )(cod) 2 " moieties. The two S atoms of each bridging ligand exhibit different coordination modes; while one is bonded to one metal, the second one is coordinated to two different rhodium centers. The shortest Rh‚‚‚Rh separation is 3.1435(5) Å. Carbonylation of the rhodium diolefin complexes under atmospheric pressure gives [Rh 4 (µ 4 -PyS 2 ) 2 (CO) 8 ] (6) which maintains the molecular framework of 1. Further reaction of the carbonyl complex with PPh 3 gives [Rh 4 (µ-PyS 2 ) 2 (CO) 4 (PPh 3 ) 4 ] (7), but this complex is prepared more conveniently by reaction of Li 2 PyS 2 with [{Rh(µ-Cl)(CO)(PPh 3 )} 2 ]. The replacement of CO by PPh 3 is not selective, and this complex exists in solution as a mixture of three isomers due to the relative position of the PPh 3 groups. The diolefinic and carbonyl complexes are fluxional. Variable temperature 1 H and 13 C{ 1 H} spectra associated with H,H-COSY experiments led to the assignment of the olefinic resonances and the conclusion that the two diolefins at the inner part of the complexes are rigid, while the two external ones undergo the fluxional behavior due to an inversion at the terminal sulfur donor atoms. This is also the origin of the fluxionality of the carbonyl complex. Deprotonation of Py(SH) 2 with [Rh(acac)(cod)] (acac ) acetylacetonate) can be carried out stepwise, giving the dinuclear complex [Rh 2 (µ-PyS 2 H) 2 (cod) 2 ] (8), and later the tetranuclear complex 1. This method to synthesize heterotetranuclear complexes by the addition of either [Ir(acac)(cod)] or [{Ir(µ-OMe)-(cod)} 2 ] to the isolated dinuclear rhodium complex (8) has been shown to be nonselective, giving a mixture of tetranuclear complexes with the [Rh 3 Ir] 4+ , [Rh 2 Ir 2 ] 4+ , and [RhIr 3 ] 4+ cores. The rhodium complexes undergo two reversible one-electron oxidations at a platinum bead electrode in dichloromethane separated by approximately 0.4 V at potentials E°in the ranges 0.0-0.4 and 0.4-0.8 V. The electrochemical behavior of the iridium complex is more complicated, undergoing two similar one-electron oxidations followed by a chemical reaction.
Journal of Molecular Catalysis, 1992
A series of homogeneous R-C(COCH 3)zRh(CO)z complexes (where R = H, n-C 3H7 , (CH3)3Si(CHzh and (CZH50)3Si(CHzh) was prepared. The immobilized analogues were synthesized using (CZH50)3Si(CHz)3CH(COCH3)z in the following ways: (i) by reaction of the complex (CzH50)3Si(CHz)3C(COCH3)zRh(CO)z with untreated silica; (ii) by reaction of Rhz(CO)4Clz with silica functionalized by (CZH50)3Si(CHz)3CH(COCH3)2; (iii) by treatment of Rhz(CO)4Clz with a polycondensate prepared by hydrolysis and condensation of (CZH50)3Si(CHz)3CH(COCH3)Z and tetraethoxysilane; (iv) by sol-gel processing of (CzH50)3Si(CHz)3C(COCH3)zRh(CO)z and tetraethoxysilane. The homogeneous complexes and their immobilized analogues are efficient catalysts for hydrogenation and hydrosilylation of alkenes. Their activities are discussed in relation to their structures and method of preparation.
European Journal of Inorganic Chemistry, 2007
The direct protonation of the bridging hydroxo ligands in [Rh(µ-OH)(cod)] 2 by 1,1dimercaptocyclohexane, Chxn(SH) 2 , yields the gem-dithiolato-bridged compound [Rh 2 (µ-S 2 Chxn)(cod) 2 ] (1). The dinuclear framework in 1 is supported by a 1,1-cyclohexanedithiolato ligand exhibiting a 1:2κ 2 S, 1:2κ 2 S' coordination mode. Compound 1 in the presence of P-donor ligands is an active catalyst precursor for the hydroformylation of oct-1-ene under mild conditions of pressure and temperature (100 PSI, 353 K). Best results have been obtained using phosphite ligands as modifying ligands. Selectivity in aldehydes of 97%, 81% of regioselectivity towards linear aldehyde and turnover frequencies up to 198 h-1 have been obtained using the catalytic system 1/P(OMe) 3. The dinuclear compound [Rh 2 (µ-S 2 Chxn)(CO) 2 (PPh 3) 2 ] (2) has been isolated from the catalytic solutions resulting from the system 1/PPh 3 and characterized by spectroscopic means and a X-ray diffraction study as the trans isomer. The mixed-ligand dinuclear complexes 2 and [Rh 2 (µ-S 2 Chxn)(CO) 2 (PCy 3) 2 ] (3) (Cy = cyclohexyl) have been independently prepared by reaction of Chxn(SH) 2 with the mononuclear complexes [Rh(acac)(CO)(PR 3)] in the appropriate molar ratio.
Journal of Organometallic Chemistry, 1992
The reaction of 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz) with RhCl 3 ‚3H 2 O has been studied under different experimental conditions. This reaction in ethanol resulted in the formation of [Rh(tptz)Cl 3 ]‚2H 2 O (1), whereas the bis-chelate complex [Rh(tptz) 2 ][ClO 4 ] 3 ‚2H 2 O (2) was obtained in a two-step reaction in acetone; the chlorides from RhCl 3 were removed in the first step using AgClO 4 , and the ligand tptz was added in the second step. Complexes 1 and 2, when refluxed in ethanol-water (1:1), resulted in metal-promoted hydrolysis of tptz to bis-(2-pyridylcarbonyl)amide anion (bpca) and 2-picolinamide (pa), yielding the complexes [Rh(bpca)(pa)Cl][PF 6 ]‚ H 2 O (3) and [Rh(bpca) 2 ][ClO 4 ] (6), respectively. A mixed-ligand complex, [Rh(bpca)(tpy)][PF 6 ] 2 ‚CH 3 CN (4), was obtained by the reaction of either 1 with tpy or [Rh(tpy)Cl 3 ] (5) with tptz in ethanol-water medium. The crystal structures of complexes 1 and 4 have been determined. Crystal data: complex 1, monoclinic, P2 1 /c, a) 11.642(2) Å, b) 7.302(2) Å, c) 24.332(3) Å,) 96.420(10)°, Z) 4, R) 0.040, and wR2) 0.117; complex 4, triclinic, P1 h, a) 9.581(1) Å, b) 12.933(2) Å, c) 14.493(2) Å, R) 82.480(10)°,) 71.810(10)°, γ) 75.100(10)°, Z) 2, R) 0.030, and wR2) 0.082. The two water molecules of complex 1 make short contacts with the carbon atoms adjacent to the metal-bound nitrogen atom of the triazine ring; this observation provides some insight about the "intermediate" of the hydrolysis. X-ray and NMR data suggest that the electron-withdrawing effect of the metal ion is the major responsible factor for the hydrolysis of tptz. The cyclic voltammograms of the complexes exhibit a metal-based 2e reduction (Rh(III) f Rh(I)) at the potential range-0.42 to-0.98 V vs SCE, followed by ligand-based redox couple(s). These novel complexes show effective catalytic properties for the electrocatalytic reduction of carbon dioxide in the potential range-1.26 to-1.44 V.