| 1. |
- Ghosh, Shishir, et al.
(författare)
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Activation of tri(2-furyl)phosphine at a dirhenium centre: Formation of phosphido-bridged dirhenium complexes
- 2009
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Ingår i: Journal of Organometallic Chemistry. - : Elsevier BV. - 0022-328X. ; 694:18, s. 2941-2948
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Tidskriftsartikel (refereegranskat)abstract
- Reaction of tri(2-furyl) phosphine (PFu(3)) with [Re-2(CO)(10) (n)(NCMe)(n)] (n = 1, 2) at 40 degrees C gave the substituted complexes [Re-2(CO)(10) (n)(PFu(3))(n)] (1 and 2), the phosphines occupying axial position in all cases. Heating [Re-2(CO)(10)] and PFu(3) in refluxing xylene also gives 1 and 2 together with four phosphido-bridged complexes; [Re-2(CO)(8) (n)(PFu(3))(n)(mu-PFu(2))(mu-H)] (n = 0, 1, 2) (3-5) and [Re-2(CO)(6)(PFu(3))(2)(mu-PFu(2))(mu-Cl)] (6) resulting from phosphorus-carbon bond cleavage. A series of separate thermolysis experiments has allowed a detailed reaction pathway to be unambiguously established. A similar reaction between [Re-2(CO)(10)] and PFu(3) in refluxing chlorobenzene furnishes four complexes which include 1, 2, 6 and the new binuclear complex [Re-2(CO)(6)(eta(1)-C4H3O)(2)(mu-PFu(2))(2)] (7). All new complexes have been characterized by a combination of spectroscopic data and single crystal X-ray diffraction studies. (C) 2009 Published by Elsevier B.V.
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| 2. |
- Ghosh, Shishir, et al.
(författare)
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Carbon-hydrogen bond activation of phenyldi(2-thienyl)phosphine at a triosmium cluster centre
- 2010
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Ingår i: Inorganica Chimica Acta. - : Elsevier BV. - 0020-1693. ; 363:7, s. 1611-1614
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Tidskriftsartikel (refereegranskat)abstract
- The phenyldi(2-thienyl)phosphine (PhPTh2) complexes [Os-3(CO)(12-n)(PhPTh2)(n)] (n = 1-3) (1-3) have been prepared. Thermolysis of 1 and either 2 or 3 in octane affords carbon-hydrogen bond activation products [Os-3(CO)(9){mu(3)-PPhTh(C4H2S)}(mu-H)] (4) and [Os-3(CO)(8)(PPhTh2){mu(3)-PPhTh(C4H2S)}(mu-H)] (5), respectively. Both exist as isomeric mixtures differing in the relative positions of phenyl and thienyl substituents with respect to the triosmium centre. The nature of the process has been confirmed by a single crystal X-ray diffraction analysis of 4. (C) 2010 Elsevier B.V. All rights reserved.
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| 3. |
- Ghosh, Shishir, et al.
(författare)
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Electrocatalytic proton reduction by thiolate-capped triiron clusters [Fe3(CO)9(μ3-SR)(μ-H)] (R = iPr, tBu)
- 2018
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Ingår i: Inorganica Chimica Acta. - : Elsevier BV. - 0020-1693. ; 480, s. 47-53
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Tidskriftsartikel (refereegranskat)abstract
- The redox behaviour and electrocatalytic proton reduction ability of the thiolate-capped triiron clusters [Fe3(CO)9(μ3-SR)(μ-H)] (1, R = iPr; 2, R = tBu) have been investigated. In CH2Cl2, both show a quasi-reversible reduction and an irreversible oxidation. The thiol substituent has a significant influence on their reduction potentials (E1/2 = −1.24 V for 1 and E1/2 = −1.40 V for 2 vs. Fc+/Fc) but less impact on oxidation potentials (E1/2 = 0.99 V for 1 and E1/2 = 0.93 V for 2 vs. Fc+/Fc). Reduction is quasi-reversible and DFT studies reveal that this is due to scission of an iron-iron bond. While the clusters are not protonated by CF3CO2H or HBF4·Et2O, they can catalyse proton reduction of these acids at their corresponding reduction potentials following an ECEC mechanism.
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| 4. |
- Ghosh, Shishir, et al.
(författare)
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Hydrogenase biomimetics with redox-active ligands : Electrocatalytic proton reduction by [Fe2(CO)4(κ2-diamine)(μ-edt)] (diamine = 2,2′-bipy, 1,10-phen)
- 2016
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Ingår i: Polyhedron. - : Elsevier BV. - 0277-5387. ; 116, s. 127-135
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Tidskriftsartikel (refereegranskat)abstract
- Diiron complexes bearing redox active diamine ligands have been studied as models of the active site of [FeFe]-hydrogenases. Heating [Fe2(CO)6(μ-edt)] (edt = 1,2-ethanedithiolate) with 2,2′-bipyridine (2,2′-bipy) or 1,10-phenanthroline (1,10-phen) in MeCN in the presence of Me3NO leads to the formation of [Fe2(CO)4(κ2-2,2′-bipy)(μ-edt)] (1-edt) and [Fe2(CO)4(κ2-1,10-phen)(μ-edt)] (2-edt), respectively, in moderate yields. In the solid state the diamine resides in dibasal sites, while both dibasal and apical–basal isomers are present in solution. Both stereoisomers protonate readily upon addition of strong acids. Cyclic voltammetry in MeCN shows that both complexes undergo irreversible oxidation and reduction, proposed to be a one- and two-electron process, respectively. The structures of neutral 2-edt and its corresponding one- and two-electron reduced species have been investigated by DFT calculations. In 2-edt−the added electron occupies a predominantly ligand-based orbital, and the iron–iron bond is maintained, being only slightly elongated. Addition of the second electron affords an open-shell triplet dianion where the second electron populates an Fe–Fe σ*antibonding orbital, resulting in effective scission of the iron–iron bond. The triplet state lies 4.2 kcal mol−1lower in energy than the closed-shell singlet dianion whose HOMO correlates nicely with the LUMO of the neutral species 2-edt. Electrocatalytic proton reduction by both complexes has been studied in MeCN using CF3CO2H as the proton source. These catalysis studies reveal that while at high acid concentrations the active catalytic species is [Fe2(CO)4(μ-H)(κ2-diamine)(μ-edt)]+, at low acid concentrations the two complexes follow different catalytic mechanisms being associated with differences in their relative rates of protonation.
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| 5. |
- Ghosh, Shishir, et al.
(författare)
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Reactivity of phenyldi(2-thienyl) phosphine towards group 7 metal carbonyls: Carbon-phosphorus bond activation
- 2009
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Ingår i: Inorganica Chimica Acta. - : Elsevier BV. - 0020-1693. ; 362:15, s. 5175-5182
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Tidskriftsartikel (refereegranskat)abstract
- Addition of phenyldi(2-thienyl) phosphine (PPhTh2) to [Re-2(CO)(10-n)(NCMe)(n)] (n = 1, 2) affords the substitution products [Re-2(CO)(10-n)(PhPTh2)(n)] (1, 2) together with small amounts of fac-[ClRe(CO)(3)(PPhTh2)(2)] (3) (n = 2). Reaction of [Re-2(CO)(10)] with PPhTh2 in refluxing xylene affords a mixture which includes 2, [Re-2(CO)(7)(PPhTh2)(mu-PPhTh)(mu-H)] (4), [Re-2(CO)(7)(PPhTh2)(mu-PPhTh)(mu-eta(1), kappa(1)(S)-C4H3S)] (5) and mer[HRe(CO)(3)(PPhTh2)(2)] (6). Phosphido-bridged 4 and 5 are formed by the carbon-phosphorus bond cleavage of the coordinated PPhTh2 ligand, the cleaved thienyl group being retained in the latter. Reaction of [Mn-2(CO)(10)] with PPhTh2 in refluxing toluene affords [Mn-2(CO)(9)(PPhTh2)] (7) and the carbon-phosphorus bond cleavage products [Mn-2(CO)(6)(mu-PPhTh)(mu-eta(1),eta(5)-C4H3S)] (8) and [Mn-2(CO)(5)(PPhTh2)(mu-PPhTh)(mu-eta(1),eta(5)-C4H3S)] (9). Both 8 and 9 contain a bridging thienyl ligand which is bonded to one manganese atom in a eta(5)-fashion. (C) 2009 Elsevier B. V. All rights reserved.
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| 6. |
- Ghosh, Shishir, et al.
(författare)
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Reactivity of the triruthenium ortho-metalated cluster [Ru-3(CO)(9){mu(3)- eta(1), kappa(1),kappa(2)-PhP( C6H4) CH2PPh}] with tri(2-thienyl) phosphine and tri( 2-furyl) phosphine: Formation of 1,3-diphenyl-2,3-dihydro-1H-1,3-benzodiphosphine complexes via phosphorus-carbon bond formation
- 2009
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Ingår i: Journal of Organometallic Chemistry. - : Elsevier BV. - 0022-328X. ; 694:20, s. 3312-3319
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Tidskriftsartikel (refereegranskat)abstract
- Reaction of [Ru(CO)(9){mu(3-)eta(1),kappa(1),kappa(2)-PhP(C6H4)CH2PPh}] (1) with tri(2-thienyl) phosphine (PTh3) in refluxing THF afforded [Ru-3(CO)(9)(PTh3)(mu-dpbm)] (3){dpbm = PhP(C6H4)(CH2)PPh} and [Ru-3(CO)(6)(mu-CO)(2){mu-kappa(1),eta(1)-PTh2(C4H2S)}{mu(3)-kappa(1),ka ppa(2)-Ph2PCH2PPh}] (5) in 18% and 12% yields, respectively, while a similar reaction with tri(2-furyl)phosphine (PFu(3)) gave [Ru-3(CO)(9)(PFu(3))(mu-dpbm)] (4) and [Ru-3(CO)(7)(mu-eta(1),eta(2)-C4H3O)(mu-PFu(2)){mu(3)-eta(1),kappa(1),ka ppa(2)-PhP(C6H4)CH2PPh}] (6) in 24% and 27% yields, respectively. Compounds 2 and 4 are phosphine adducts of 1 in which the diphosphine ligand is transformed into 1,3-diphenyl-2,3-dihydro-1H-1,3-benzodiphosphine(dpbm) via phosphorus-carbon bond formation. Cluster 5 results from metalation of a thienyl ring, the cleved proton being transfoerred to the diphosphine.Carbon-phosphorus bond clevarge of a PFu(3) ligand is observed in 6 to afford a phosphido-bridge and furyl fragment, the latter bridging in a sigma,pi-vinyl fashion. The molecular strucutres of 3,5 and 6 have been determined by X-ray diffraction studies. (C) 2009 Published by Elsevier B.V.
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| 7. |
- Ghosh, Shishir, et al.
(författare)
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Unsymmetrical alkyne binding to a triruthenium centre: Oxidative-addition of diphenyl ditelluride to the furyne cluster [Ru-3(CO)(7)(mu-H)(mu(3)-eta(2)-C4H2O){mu-P(C4H3O)(2)}(mu-dppm)]
- 2011
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Ingår i: Journal of Organometallic Chemistry. - : Elsevier BV. - 0022-328X. ; 696:10, s. 1982-1989
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Tidskriftsartikel (refereegranskat)abstract
- Oxidative-addition of PhTe2Ph to the furyne cluster [Ru-3(CO)(7)(mu-H)(mu(3)-eta(2)-C4H2O){mu-P(C4H3O)(2)}(mu-dppm)] (1) results in the isolation of four complexes; (i) the previously reported 54-electron cluster [Ru-3(CO)(6)(mu(3)-Te)(2)(mu-TePh)(2)(mu-dppm)] (5) which results from elimination of trifuryl phosphine, (ii) the furenyl cluster [Ru-3(CO)(5)(mu-eta(2)-C4H3O){mu-P(C4H3O)(2)}(mu-TePh)(2)(mu-dppm)] (6) which results from carbon-hydrogen bond formation and (iii) two new 50-electron complexes [Ru-3(CO)(5)(mu-H)(mu(3)-eta(2)-C4H2O){mu-P(C4H3O)(2)}(mu-TePh)(2)(kappa (2)-dppm)] (7) and [Ru-3(CO)(4)(mu-H){P(C4H3O)(3)}(mu(3)-eta(2)-C4H2O){mu-P(C4H3O)(2)}(mu-T ePh)(2)(kappa(2)-dppm)] (8) both containing unsymmetrical furyne ligands. The structures of all the new compounds have been unambiguously established by single crystal X-ray crystallography. Further reactivity studies have provided a clear understanding of the relative sequence of the key oxidative-addition and reductive-elimination processes, showing that 6 is an intermediate in the formation of 7. DFT calculations have been used to shed light on the unsymmetrical binding of the furyne ligand in 7 and also to show that the adopted position of the heteroatom within the furyne ring can vary within complexes of this type. (C) 2010 Elsevier B.V. All rights reserved.
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| 8. |
- Hossain, Kamal, et al.
(författare)
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Synthesis of [Ru-3(CO)(9)(mu-dppf){P(C4H3E)(3)}] (E = O, S) and thermally induced cyclometalation to form [(mu-H)Ru-3(CO)(7)(mu-dppf){mu(3)-( C4H3E)(2)P(C4H2E)}] (dppf=1,1 '-bis(diphenylphosphino) ferrocene)
- 2014
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Ingår i: Journal of Organometallic Chemistry. - : Elsevier BV. - 0022-328X. ; 760, s. 231-239
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Tidskriftsartikel (refereegranskat)abstract
- The new clusters [Ru-3(CO)(9)(mu-dppf){P(C4H3E)(3)}] (1, E = O; 2, E = S) have been prepared from the Me3NO-induced decarbonylation of [Ru-3(CO)(10)(mu-dppf)] in the presence of PFu(3) (E = O) and PTh3 (E = S), respectively. Upon thermolysis in benzene, the major products are the cyclometalated clusters [(mu-H) Ru-3(CO)(7)(mu-dppf){mu(3)-(C4H3E)(2)P(C4H2E)}] (3, E - O; 4, E - S). This thermolytic behavior is in marked contrast to that previously noted for the analogous bis(diphenylphosphino) methane (dppm) complexes [Ru-3(CO)(9)(mu-dppm){P(C4H3E)(3)}], in which both carbon-hydrogen and carbon-phosphorus bond activation yields furyne- and thiophyne-capped clusters. The crystal structures of 1, 3 and 4 are presented and reveal that phosphine migration has occurred during the transformation of 1,2 into 3,4, respectively. The possible relation of the observed reactivity to the relative flexibilities of the diphosphine ligands is discussed. Density functional calculations have been performed on the model cluster [Ru-3(CO)(9)(mu-Me-4-dppf){ P(C4H3O)(3)]}], and these data are discussed relative to the ground-state energy differences extant between the different isomeric forms of this cluster. The dynamic NMR behavior displayed by the metalated thienyl ring in cluster 4 has also been investigated by computational methods, and the free energy of activation for the "windshield wiper" motion of the activated thienyl moiety determined. (C) 2013 Elsevier B.V. All rights reserved.
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| 9. |
- Kathiravan, Suppan, et al.
(författare)
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Copper catalysed amidation of aryl halides through chelation assistance
- 2015
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 51:23, s. 4834-4837
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Tidskriftsartikel (refereegranskat)abstract
- A copper mediated C-N bond formation for the amidation of aryl halides using 8-aminoquinoline has been developed. This strategy provides efficient access to amides bearing two contiguous heterocyclic moieties and does not require the presence of additional ligands.
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| 10. |
- Raha, Arun K., et al.
(författare)
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A comparative study of the reactivity of the lightly stabilized cluster [Os-3(CO)(8){mu(3)-Ph2PCH2P(Ph)C6H4}(mu-H)] towards tri(2-thienyl)-, tri(2-furyl)- and triphenyl-phosphine
- 2014
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Ingår i: Journal of Organometallic Chemistry. - : Elsevier BV. - 0022-328X. ; 751, s. 399-411
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Tidskriftsartikel (refereegranskat)abstract
- Reactions of the lightly stabilized triosmium cluster [Os-3(CO)(8){mu(3)-Ph2PCH2P(Ph)C6H4}(mu-H)] with tri(2-thienyl)phosphine (PTh3) and tri(2-furyl)phosphine (PFu(3)) are described and compared to analogous reactions with PPh3. At room temperature, a number of products are isolated: [Os-3(CO)(10)(mu-dppm)] from CO addition, [Os-3(CO)(8)(PR3){mu(3)-Ph2PCH2P(Ph)C6H4}(mu-H)] from phosphine addition, [Os-3(CO)(9)(PR3)(mu-dppm)] from phosphine and CO addition and [Os-3(CO)(8)(PR3)(2)(mu-dppm)] from addition of two equivalents of phosphine. The latter are shown by NMR and X-ray diffraction to exist as 1,2-isomers, whereby one phosphine is bound to the non-dppm-substituted center and the second shares an osmium atom with one end of the diphosphine. Heating 1,2-[Os-3(CO)(8)(PTh3)(2)(mu-dppm)] at 100 degrees C results in its clean isomerization to the 1,1-isomer in which both monodentate phosphines are located on the same osmium atom. Prolonged heating of [Os-3(CO)(8)(PR3)(2)(mu-dppm)] (R = Th, Ph) at 110 degrees C gives [Os-3(CO)(9)(PR3)(mu-dppm)] and the new lightly stabilized clusters [Os-3(CO)(7)(PR3){mu(3)-Ph2PCH2P(Ph)C6H4}(mu-H)], the latter being formed by loss of phosphine and CO with concurrent metalation of a phenyl ring. Heating [Os-3(CO)(8)(PFu(3))(2)(mu-dppm)] at 110 degrees C gives [Os-3(CO)(9)(PFu(3))(mu-dppm)] together with the carbon-phosphorus bond cleavage products [Os-3(CO)(7)(mu-PFu(2))(mu(3)-eta(2)-C4H2O)(mu-H)(mu-dppm)] and [Os-3(CO)(7)(mu-PFu(2))(mu(3)-eta(2)-C6H3CH3)(mu-H)(mu-dppm)]. All new compounds were characterized by analytical and spectroscopic techniques together with single crystal X-ray diffraction analysis of nine clusters. Density functional theory (DFT) calculations have been carried out on isomers of [Os-3(CO)(8)(PR3)(2)(mu-dppm)] in order to understand the observed isomer ratios. (C) 2013 Elsevier B.V. All rights reserved.
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