@article { ISI:000231556400005, title = {2,5-dioxido-1,4-benzoquinonediimine (H2L2-), a hydrogen-bonding noninnocent bridging ligand related to aminated topaquinone: different oxidation state distributions in complexes [{(bpy)(2)Ru}(2)(mu-H2L)](n) (n=0,+,2+,3+,4+) and [{(acac)(2)Ru}(2)(mu-H2L)]}, journal = {Chemistry - a European Journal}, volume = {11}, number = {17}, year = {2005}, month = {AUG}, pages = {4901-4911}, publisher = {WILEY-V C H VERLAG GMBH}, type = {Article}, address = {PO BOX 10 11 61, D-69451 WEINHEIM, GERMANY}, abstract = {

{The symmetrically dinuclear title compounds were isolated as diamagnetic [(bpy)(2)Ru(mu-H2L)Ru(bpy)(2)]- (ClO4)(2) (1-(ClO4)(2)) and as paramagnetic [(acac)(2)Ru(mu-H2L)Ru(acac)(2)] (2) complexes (bpy = 2,2{\textquoteright}-bipyridine; acac(-) -

}, keywords = {bridging ligands, Density functional calculations, EPR spectroscopy, N, O ligands, ruthenium}, issn = {0947-6539}, doi = {10.1002/chem.2005.00202}, author = {Kar, S. and Sarkar, B. and Ghumaan, Sandeep and Janardanan, D. and van Slageren, J. and Fiedler, Jan and Puranik, Vedavati G. and Sunoj, R. B. and Kaim, Wolfgang and Lahiri, Goutam Kumar} } @article { ISI:000229127000022, title = {Effect of 2-(2-pyridyl)azole-based ancillary ligands (L1-4) on the electrophilicity of the nitrosyl function in [Ru-II(trpy)(L1-4)(NO)](3+) [trpy=2,2 {\textquoteleft}: 6 {\textquoteleft},2 {\textquoteleft}{\textquoteright}-terpyridine]. synthesis, structures, and spectroscopic, electrochemical, and kinetic aspects}, journal = {Inorganic Chemistry}, volume = {44}, number = {10}, year = {2005}, month = {MAY}, pages = {3499-3511}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Ruthenium nitrosyl complexes [Ru(trpy)(L1-4)(NO)](3+) (13-16) [trpy = 2,2{\textquoteright}:6{\textquoteright},2"-terpyridine, L-1 = 2-(2-pyridyl)-benzoxazole, L-2 = 2-(2-pyridyl)benzthiazole, L-3 = 2-(2-pyridyl)benzimidazole, L-4 = 1-methyl-2-(2-pyridyl)-1H-benzimidazole] were obtained in a stepwise manner starting from [Ru-II(trpy)(L1-4) (Cl)]ClO4 (1-4) \→ [Ru-II(trpy)(L1-4) (H2O)](ClO4)(2) (5-8) \→ [Ru-II(trpy)(L1-4) (NO2)ClO4 (9-12) \→ [Ru-II(trpy)(L-1,L-2,L-4) (NO)](ClO4)(3) (13, 14, 16)/[Ru-II(trpy)(L-3) (NO)](Cl)(4))(2)(NO3) (15). Crystal structures of 1, 2, 4, 9, 12, 13, 15, and 16 established the stereoretentive nature of the transformation processes. Though the complexes of L1, L3, and L 4 were isolated in the isomeric form A (π-acceptor trpy and azole ring in the equatorial plane and the pyridine and chloride donors in the axial positions), complexes of L 2 preferentially stabilized in form B (trpy and pyridine in the equatorial plane and the azole ring and chloride donors in the axial positions). The v(NO) stretching frequency varied in the range of 1957-1932 cm(-1), 13 \&MGT; 14 \&MGT; 15 \> 16, primarily depending on the electronic aspects of L as well as the isomeric structural forms. The coordinated nitrosyl function underwent successive reductions of [Ru-II-NO+](3+) \→ [Ru-II-NO\•](2+) and [Ru-II-NO\•](2+) - [Ru-II-NO-](+), and the first reduction potential follows the order 14 \> 13 \&MGT; 15 \≈ 16. The nearly axial EPR spectra having nitrogen hyperfine splittings (A \≈ 26 G) at 77 K of 13(-)-16(-) with (g) \≈ 2.0 established that the reduction process is largely centered around the nitrosyl function. Despite an appreciably high v(NO), the complexes were found to be unusually stable even in the aqueous medium. They transformed slowly and only partially into the corresponding nitro derivatives in H2O (k \≈ 10(-4) s(-1) and K = 0.4-3.8). The chloro (1-4), aqua (5-8), and nitro (9-12) derivatives displayed reasonably strong emissions near 700 nm at 77 K (φ = 10(-1)-10(-2)). The aqua derivative 7 was found to interact with the calf thymus and the circular form of p-Bluescript SK DNA.

}, issn = {0020-1669}, doi = {10.1021/ic048184w}, author = {Chanda, N. and Paul, D. and Kar, S. and Mobin, Shaikh M. and Datta, Anindya and Puranik, Vedavati G. and Rao, K. K. and Lahiri, Goutam Kumar} } @article { ISI:000227146700004, title = {MCM-41-supported platinum carbonyl cluster-derived asymmetric hydrogenation catalyst}, journal = {Journal of Catalysis}, volume = {229}, number = {2}, year = {2005}, month = {JAN}, pages = {298-302}, publisher = {ACADEMIC PRESS INC ELSEVIER SCIENCE}, type = {Article}, address = {525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA}, abstract = {

Anionic platinum carbonyl cluster has been ion paired with cinchonidium groups that are chemically bound to the surface of MCM-41 and fumed silica. In the hydrogenation of methyl pyruvate or acetophenone the fumed silica-based catalyst gives zero enantioselectivity, but under optimum conditions enantiomeric excesses of \>90 and similar to40\%, respectively, are obtained with the MCM-41-based catalyst. (C) 2004 Elsevier Inc. All rights reserved.

}, keywords = {asymmetric catalysis, functionalized inorganic oxides, hydrogenation catalysts, platinum carbonyl cluster}, issn = {0021-9517}, doi = {10.1016/j.jcat.2004.11.010}, author = {Basu, Susmit and Paul, Himadri and Gopinath, Chinnakonda S. and Bhaduri, Sumit and Lahiri, Goutam Kumar} } @article { ISI:000227107500022, title = {Synthesis, structure, electrochemistry and ROMP-activity of new ferrocenyl analog of Grubbs{\textquoteright} metathesis catalyst}, journal = {Journal of Organometallic Chemistry}, volume = {690}, number = {4}, year = {2005}, month = {FEB}, pages = {1018-1027}, publisher = {ELSEVIER SCIENCE SA}, address = {PO BOX 564, 1001 LAUSANNE, SWITZERLAND}, abstract = {

Treatment of [(PCy3)(2)Cl2Ru=CH-Ph] (1) with vinylferrocene 1 and 1-ferrocenyl-1,3-butadiene 2 yielded solid products. These new complexes were characterized by H-1 NMR, P-31 NMR and C-13 NMR spectroscopy. X-ray crystal structures of both the complexes have been solved. The crystal structure of II confirmed the assigned structure and revealed existence of two sets of intermolecular C-H-Cl(M) type interactions, viz. (Ru)Cl-H-C(ferrocene) and (Ru)Cl-H-CHCl2. The air-stable, dark solid II is all efficient catalyst for ring-opening metathesis polymerization (ROMP) of cyclopentene, norbornene and cycloocta-1,5-diene. Electrochemical behavior of the complexes clearly reflects electronic communication between two metal centers. (C) 2004 Elsevier B.V. All rights reserved.

}, keywords = {Electrochemistry, ferrocene, Metathesis, non-covalent interactions, ring-opening metathesis polymerization, ruthenium carbene}, issn = {0022-328X}, doi = {10.1016/j.jorganchem.2004.11.012}, author = {Maishal, T. K. and Mondal, Biplab and Puranik, Vedavati G. and Wadgaonkar, P. P. and Lahiri, Goutam Kumar and Sarkar, A.} } @article { ISI:000226847200018, title = {Tetrazine derived mononuclear Ru-II(acac)(2)(L)(1), [Ru-II(bpy)(2)(L)](ClO4)(2)(2) and [Ru-II(bpy)(L)(2)](ClO4)(2)(3) (L=3-amino-6-(3,5-dimethylpyrazol-1-yl)-1,2,4,5-tetrazine, acac = acetylacetonate, bpy=2,2 {\textquoteright}-bipyridine): syntheses, structures, spectra}, journal = {Polyhedron}, volume = {24}, number = {2}, year = {2005}, month = {JAN}, pages = {333-342}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, type = {Article}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

Mononuclear ruthenium complexes of tetrazine derived L, Ru-II(acac)(2)(L) (1), [Ru-II(bpy)(2)(L)](ClO4)(2) (2) and [Ru-II(bpy)(L)(2)](ClO4)2 (3) (L = 3-amino-6-(3,5-dimethylpyrazol-1-yl)-1,2,4,5-tetrazine, acac = acetylacetonate and bpy = 2,2{\textquoteright}-bipyridine) were prepared. The free L exists as a dimeric entity in the solid state via hydrogen bonding interactions involving L and water molecules present in the crystal lattice. 1 exhibits unusually strong bonds from Ru-II to coordinating pyrazolyl-N (2.040(2) Angstrom) and especially to tetrazine-N (1.913(2) Angstrom). The Ru-III/Ru-II couples of 1-3 appeared at 0.28, 1.34 and 1.50 V versus SCE, respectively. The tetrazine and bpy-based reductions were observed at -1.33 (1); -0.55 and -1.55/-1.75/-1.98 (2); -0.47/-0.78 and -1.80/-2.02 V (3), respectively. 1, 2 and 3 displayed two MLCT bands each, corresponding to dpi(Ru-II) --\> pi* (L, tetrazine) and dpi(Ru-II) --\> pi* (acac or bpy or L) transitions. 1(+) and 2(+) showed rhombic EPR spectra at 110 and 4 K, respectively and 1(-), 2(-) and 3(-) exhibited multiple line EPR spectra at 300 K. 1-3 exhibited moderately strong emission spectra in EtOH-MeOH glass at 77 K. (C) 2004 Elsevier Ltd. All rights reserved.

}, keywords = {Electrochemistry, redox, ruthenium-tetrazine, spectra, structure, synthesis}, issn = {0277-5387}, doi = {10.1016/j.poly.2004.11.019}, author = {Nayak, A. and Patra, S. and Sarkar, B. and Ghumaan, Sandeep and Puranik, Vedavati G. and Kaim, Wolfgang and Lahiri, Goutam Kumar} } @article { ISI:000227346300059, title = {Unusual monodentate binding mode of 2,2 {\textquoteleft}-dipyridylamine (L) in isomeric trans(acac)(2)Ru-II(L)2, trans-[(acac)(2)Ru-III(L)(2)]ClO4, and cis-(acac)(2)Ru-II(L)(2) (acac = acetylacetonate). Synthesis, structures, and spectroscopic, electrochemical, and magn}, journal = {Inorganic Chemistry}, volume = {44}, number = {5}, year = {2005}, month = {MAR}, pages = {1571-1579}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

{The reaction of cis-Ru(acac)(2)(CH3CN)(2) (acac = acetylacetonate) with 2,2{\textquoteright}-dipyridylamine (L) in ethanolic medium resulted in facile one-pot synthesis of stable [(acac)(2)Ru-III(L)]ClO4 ([1]ClO4), trans-[(acac)(2)Ru-II(L)2] (2), trans[(acac)(2)Ru-III(L)(2)[ClO4 ([2]ClO4), and cis-[(acac)(2)Ru-II(L)(2)] (3). The bivalent congener 1 was generated via electrochemical reduction Of [1]ClO4. Although in [1](+) the dipyridylamine ligand (L) is bonded to the metal ion in usual bidentate fashion, in 2/[2](+) and 3, the unusual monodentate binding mode of L has been preferentially stabilized. Moreover, in 2/[2](+) and 3, two such monodentate L{\textquoteright}s have been oriented in the trans- and cis-configurations, respectively. The binding mode of L and the isomeric geometries of the complexes were established by their single-crystal X-ray structures. The redox stability of the Ru(II) state follows the order 1 \< 2 much less than 3. In contrast to the magnetic moment obtained for [1]ClO4

}, issn = {0020-1669}, doi = {10.1021/ic049219v}, author = {Kar, S. and Chanda, N. and Mobin, Shaikh M. and Urbanos, F. A. and Niemeyer, M. and Puranik, Vedavati G. and Jimenez-Aparicio, Reyes and Lahiri, Goutam Kumar} } @article { ISI:000236119700018, title = {2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz)-derived [Ru-II(tptz)(acac)(CH3CN)](+) and mixed-valent [(acac)(2)Ru-III{(mu-tptz-H+)(-)}Ru-II(acac)(CH3CN)](+)}, journal = {Inorganic Chemistry}, volume = {45}, number = {6}, year = {2006}, month = {MAR}, pages = {2413-2423}, type = {Article}, abstract = {

Mononuclear [Ru-II(tptz)(acac:)(CH3CN)]ClO4 ((ClO4)-Cl-[1]) and mixed-valent dinuclear [(acac)(2)Ru-III{(mu-tptz-H+)(-)}Ru-II(acac)(CH3CN)]ClO4 ([5]ClO4; acac = acetylacetonate) complexes have been synthesized via the reactions of Ru-II(acac)2(CH3CN)(2) and 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz), in 1:1 and 2:1 molar ratios, respectively. In [1]ClO4, tptz binds with the Ru-II ion in a tridentate N,N,N mode (motif A), whereas in [5]ClO4, tptz: bridges the metal ions unsymmetrically via the tridentate neutral N,N,N mode with the Ru-II center and cyclometalated N,C- state with the Ru-III site (motif F). The activation of the coordinated nitrile function in [1]ClO4 and [5]ClO4 in the presence of ethanol and alkylamine leads to the formation of iminoester ([2]ClO4 and [7]ClO4) and amidine ([4]ClO4) derivatives, respectively. Crystal structure analysis of [2]ClO4 reveals the formation of a beautiful eight-membered water cluster having a chair conformation. The cluster is H-bonded to the pendant pyridyl ring N of tptz and also with the O atom of the perchlorate ion, which, in turn, makes short (C-H{\textendash}{\textendash}-O) contacts with the neighboring molecule, leading to a H-bonding network. The redox potentials corresponding to the (RuI)-I-I state in both the mononuclear {[(acac)(tptz)Ru-II-N=-C-CH3]ClO4 ([1]ClO4) \>\> [(acac)(tptz)Ru-II-NH=C(CH3)-OC2H5]ClO4 ([2]ClO4) \> [(acac)(tptz)(RuNH2)-N-II-C6H4(CH3)]ClO4 ([3]ClO4) \> [(acac)(tptz)Ru-II-NH=C(CH3)-NHC2H5]ClO4 ([4]ClO4)} and dinuclear {[(acac)(2)Ru-III-{mu-tptz-H+)(-)}Ru-II(acac)(N equivalent to C-CH3)]ClO4 {(mu-tptz-H+)(-)}Ru-II(acac)(N equivalent to C-CH3)]ClO4 ([5]ClO4), [(acac)(2)Ru-III[(mu-tptz-H+(N-O ([6]ClO4), [(acac)(2)Ru-III{(mu-tptz-H+)(-)}Ru-II(acac)(NH=C(CH3)-OC2H5)]ClO4( [7]ClO4), and [(acac)(2)Ru-III{(mu-tptz-H+)(-)}Ru-II(acac)(NC4H4N)]ClO4 ([8]ClO4), complexes vary systematically depending on the electronic nature of the coordinated sixth ligands. However, potentials involving the Ru-III center in the dinuclear complexes remain more or less invariant. The mixed-valent (RuRuIII)-Ru-II species ([5]ClO4-[8]ClO4) exhibits high comproportionation constant (K-c) values of 1.1 X 10(12)-2 x 109, with substantial contribution from the donor center asymmetry at the two metal sites. Complexes display Ru-II- and Ru-III-based metal-to-ligand and ligand-to-metal charge-transfer transitions, respectively, in the visible region and ligand-based transitions in the UV region. In spite of reasonably high K, values for [5]ClO4[8]ClO4, the expected intervalence charge-transfer transitions did not resolve in the tpical near-IR region up to 2000 nm. The paramagnetic (RuRuIII)-Ru-II species ([5]ClO4-[8]ClO4) displays rhombic electron paramagnetic resonance (EPR) spectra at 77 K (\< g \> similar to 2.15 and Delta g similar to 0.5), typical of a low-spin Ru-III ion in a distorted octahedral environment. The one-electron-reduced tptz complexes [RuII(tptz center dot-)(acac)(CH3CN)] (1) and [(acac)(2)Ru-III{mu-tptz-H+)(center dot 2-)}-Ru-II(acac)(CH3CN)] (5), however, show a free-radical-type EPR signal near g = 2.0 with partial metal contribution.

}, doi = {10.1021/ic0514288}, author = {Ghumaan, Sandeep and Kar, S. and Mobin, Shaikh M. and Harish, B. and Puranik, Vedavati G. and Lahiri, Goutam Kumar} } @article { ISI:000240781100009, title = {Effect of spacer groups on the performance of MCM-41-supported platinum cluster-derived hydrogenation catalysts}, journal = {Journal of Catalysis}, volume = {242}, number = {2}, year = {2006}, month = {SEP}, pages = {332-339}, publisher = {ACADEMIC PRESS INC ELSEVIER SCIENCE}, type = {Article}, address = {525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA}, abstract = {

MCM-41 was functionalized with (EtO)(3)SiCH2Cl, (MeO)(3)SiCH2CH2CH2Cl, and (CH3)Cl2SiCH2Cl. The functionalized materials were characterized by solid-state NMR (CPMAS, Si-29 and C-13) and XPS. The NMR data indicate that three new silicon environments were created by(EtO)(3)SiCH2Cl and (MeO)(3)SiCH2CH2CH2Cl, whereas with (CH3)Cl2SiCH2Cl, two new silicon environments were obtained. XPS results from Si 2p core level and the valence band from the material functionalized by (MeO)(3)Si(CH2)(3)Cl was found to be the same as that of the corresponding fresh catalyst (1a), in contrast to that of the materials functionalized by the other two silane reagents. After further functionalization with triethylamine, these materials were used as inorganic anion exchangers to support the cluster anion [Pt-12(CO)(24)](2-). Solid-state NMR (29Si, C-13, N-15) was used to establish the presence of the quaternary ammonium group in the cluster-supported species. Analogous materials were also created using fumed silica as the support, and all of the cluster-supported materials were tested as catalysts for the hydrogenation of methyl pyruvate, acetophenone, nitrobenzene, benzonitrile, ethylacetoacetate, 4-nitrotoluene, cyclohexanone, allyl alcohol, and styrene. The best activity was obtained for the catalyst that had MCM-41 as the support and chloropropyl as the spacer group. TEM showed that the supports and the spacer groups had observable effects on the platinum crystallite size of the catalysts. (c) 2006 Elsevier Inc. All rights reserved.

}, keywords = {functionalized inorganic oxides, hydrogenation catalysts, MCM-41, platinum carbonyl cluster, Solid-state NMR, spacer groups, XPS}, issn = {0021-9517}, doi = {10.1016/j.jcat.2006.06.016}, author = {Maity, Niladri and Basu, Susmit and Mapa, Maitri and Rajamohanan, Pattuparambil R. and Ganapathy, Subramanian and Gopinath, Chinnakonda S. and Bhaduri, Sumit and Lahiri, Goutam Kumar} } @article { ISI:000236419800016, title = {MCM-41-supported platinum carbonyl cluster-derived catalysts for asymmetric and nonasymmetric hydrogenation reactions}, journal = {Journal of Catalysis}, volume = {239}, number = {1}, year = {2006}, month = {APR}, pages = {154-161}, publisher = {ACADEMIC PRESS INC ELSEVIER SCIENCE}, type = {Article}, address = {525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA}, abstract = {

Anionic platinum carbonyl Cluster ([Pt-12(CO)(24)](2-)) was ion-paired with the 3-chloropropyltrimethoxysilyl-ammonium group chemically bound to the surface of MCM-41. The materials undergo quick decarbonylation and have been characterized before decarbonylation by IR and UV-vis spectroscopy and after decarbonylation by XPS and TEM. They have been used as catalysts for the hydrogenations of methyl pyruvate, acetophenone, nitrobenzene, benzonitrile, and ethylacetoacetate. The support and the quaternary ammonium groups have significant effects on surface platinum concentration, crystallite size, and observed activity. In the hydrogenation of the prochiral substrates methyl pyruvate or acetophenone, the cinchonidine-based catalyst gives significant enantioselectivity under optimum conditions. A kinetic model that includes an enantioselective product-formation step and a hydrogen pressure-dependent step for the deactivation of the enantioselective sites gives reasonable agreement between predicted and observed enantioselectivity. The model is also in accordance with the XPS and TEM data. (c) 2006 Elsevier Inc. All rights reserved.

}, keywords = {asymmetric/non-asymmetric catalysis, Enantioselectivity, functionalized MCM-41, hydrogenation catalysts, platinum carbonyl cluster}, issn = {0021-9517}, doi = {10.1016/j.jcat.2006.01.032}, author = {Basu, Susmit and Mapa, Maitri and Gopinath, Chinnakonda S. and Doble, Mukesh and Bhaduri, Sumit and Lahiri, Goutam Kumar} } @article {31}, title = {Metal-induced reductive ring opening of 1,2,4,5-tetrazines: Three resulting coordination alternatives, including the new non-innocent 1,2-diiminohydrazido(2-) bridging ligand system}, journal = {Inorganic Chemistry}, volume = {45}, number = {3}, year = {2006}, month = {FEB }, pages = {1316-1325}, publisher = {WILEY-V C H VERLAG GMBH}, type = {Article}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

{Reaction of 3,6-diaryl-1,2,4,5-tetrazines (aryl = R = phenyl, 2-furyl or 2-thienyl) with 2 equiv of Ru(acac)(2)(CH3-CN)(2) results in reductive tetrazine ring opening to yield diruthenium complexes [

}, keywords = {crystal engineering, hydrogen bonds, molecular, recocynition, Self-assembly, supramolecular chemistry}, issn = {0947-6539}, doi = {10.1021/ic051532p}, author = {Maji, Somnath and Sarkar, B. and Patra, S. and Fiedler, Jan and Mobin, Shaikh M. and Puranik, Vedavati G. and Kaim, Wolfgang and Lahiri, Goutam Kumar} } @article { ISI:000256920000046, title = {MCM-41-supported organometallic-derived nanopalladium as a selective hydrogenation catalyst}, journal = {Journal of Physical Chemistry C}, volume = {112}, number = {25}, year = {2008}, month = {JUN}, pages = {9428-9433}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Palladium nanocatalysts have been prepared by anchoring (eta(3)-C(3)H(5))(2)Pd(2)Cl(2) onto dian-tine-functionalized MCM-41 supports followed by reaction with hydrogen under catalytic conditions. The catalyst precursor and used catalyst have been studied by solid-state NMR ((13)C, (29)Si), XPS, and TEM. The organometallic-derived catalyst exhibits the best performance (activity and selectivity) to date toward the selective hydrogenation of industrially relevant o- and m-chloronitrobenzene to the corresponding chloroaniline derivatives and is distinctly superior to 5\% Pd/C. Grazing angle XPS studies reveal that conversion of the tethered molecular species to the nanoparticles of palladium produces a core-shell nanostructure.

}, issn = {1932-7447}, doi = {10.1021/jp8007656}, author = {Maity, Niladri and Rajamohanan, Pattuparambil R. and Ganapathy, Subramanian and Gopinath, Chinnakonda S. and Bhaduri, Sumit and Lahiri, Goutam Kumar} } @article { ISI:000257904900015, title = {MCM-41-supported ruthenium carbonyl cluster-derived catalysts for asymmetric hydrogenation reactions}, journal = {Applied Catalysis A-General}, volume = {344}, number = {1-2}, year = {2008}, month = {JUL}, pages = {124-130}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

{The anionic ruthenium carbonyl cluster [Ru-4(mu-H)(3)(CO)(12)](-) has been ion-paired with (3-chloropropyl)-trimethoxysilyl-cinchonidium or sparteinium groups chemically bound to the surfaces of MCM-41 [(MCM-41-)(-O)(3)SiCH2CH2CH2NR3+Cl-

}, keywords = {asymmetric catalysis, functionalized MCM-41, hydrogenation catalysts, nanocatalyst, ruthenium carbonyl cluster}, issn = {0926-860X}, doi = {10.1016/j.apcata.2008.04.009}, author = {Indra, Arindam and Basu, Susmit and Kulkarni, Dhanashree G. and Gopinath, Chinnakonda S. and Bhaduri, Sumit and Lahiri, Goutam Kumar} } @article { ISI:000261555200036, title = {Valence-state analysis through spectroelectrochemistry in a series of quinonoid-bridged diruthenium complexes [(acac)(2)Ru(mu-L)Ru(acac)(2)](n) (n =+2,+1, 0,-1,-2)}, journal = {Chemistry-A European Journal}, volume = {14}, number = {34}, year = {2008}, month = {OCT}, pages = {10816-10828}, publisher = {WILEY-BLACKWELL}, type = {Article}, address = {COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA}, abstract = {

The quinonoid ligand-bridged diruthenium compounds [(acac)(2)Ru(mu-L2-)Ru(acac)(2)] (acac(-) = acetylacetonato = 2,4-pentanedionato; L2- = 2,5-dioxido-1,4-benzoquinone, 1; 3,6-dichloro-2,5-dioxido-1,4-benzoquinone, 2; 5,8-dioxido-1,4-naphthoquinone, 3; 2-3-dichloro-5,8-dioxido-1,4-naphthoquinone, 4; 1,5-dioxido-9,10-anthraquinone, 5; and 1,5-diimido-9,10-anthraquinone, 6) were prepared and characterized analytically. The crystal structure analysis of 5 in the rac configuration reveals two tris(2,4-pentanedionato)ruthenium moieties with an extended anthracenedione-derived bis(ketoenolatee) pi-conjugated bridging ligand. The weakly antiferro-magnetically coupled {Ru-III(mu-L2-)Ru{\textendash}(III)} configuration in 1-6 exhibits complicated overall magnetic and EPR responses,. ne simultaneous presence of highly redox-active quinonoid-bridging ligands and of two ruthenium centers capable of adopting the oxidation states +2, +3, and +4 creates a large variety of possible oxidation state combinations. Accordingly. the complexes 1-6 exhibit two reversible one-electron oxidation steps and at least two reversible reduction processes. Shifts to positive potentials were observed on introduction of Cl substituents (1 -\> 2, 3 -\> 4) or through replacement of NH by O (6 -\> 5). The ligand-to-metal charge transfer (LMCT) absorptions in the visible region of the neutral molecules become more intense and shifted to lower energies on stepwise reduction with two electrons. On oxidation, the para-substituted systems 1-4 exhibit monocation intermediates with intervalence charge transfer (IVCT) transitions of (RuRuIV)-Ru-III mixed-valent species. In contrast, the differently substituted systems 5 and 6 show no such near infrared (NIR) absorption. While the first reduction steps are thus assigned to largely ligand-centered processes, the oxidation appears to involve metal-ligand delocalized molecular orbitals with variable degrees of mixing.

}, keywords = {magnetic properties, quinones, ruthenium, spectroelectrochemistry, structure elucidation, valence-state distributions}, issn = {0947-6539}, doi = {10.1002/chem.200800976}, author = {Ghumaan, Sandeep and Sarkar, Biprajit and Maji, Somnath and Puranik, Vedavati G. and Fiedler, Jan and Urbanos, Francisco A. and Jimenez-Aparicio, Reyes and Kaim, Wolfgang and Lahiri, Goutam Kumar} } @article { ISI:000264978500019, title = {Applications of a high performance platinum nanocatalyst for the oxidation of alcohols in water}, journal = {Green Chemistry}, volume = {11}, number = {4}, year = {2009}, month = {FEB}, pages = {554-561}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Nanoparticles of platinum (NP-Pt), have been synthesized by supporting high nuclearity anionic carbonyl cluster (Chini cluster) on a water soluble anion exchanger, and the performance of this material, 1, as an oxidation catalyst for alcohols in water has been studied. The E-factor for the synthesis of NP-Pt by this method has been calculated and compared with that of other NP-Pt recently reported in the literature. With 1 as a catalyst, oxidations of a variety of primary and secondary alcohols by dioxygen are achieved and high turnover numbers and selectivities are obtained. The performances of 1 in the oxidation of benzyl alcohol and 1-phenylethanol are compared with those of three other platinum catalysts. These are platinum nanoparticles 2 prepared by the hydrogen reduction of [PtCl6](2-) supported on the same water soluble polymer, 5\% Pt on carbon, and 5\% Pt on alumina, designated as 3 and 4, respectively. 1 has been found to be considerably more active than 2- 4 and also other reported water soluble platinum nanocatalysts. After many turnovers (similar to 1000 and similar to 165 for benzyl alcohol and 1-phenyl ethanol, respectively) partial deactivation (similar to 40\%) is observed, but the deactivated catalyst can be fully regenerated by treatment with dihydrogen. The TEM data of fresh, deactivated and regenerated 1 show a correlation between the particle size and activity. A mechanism consistent with this and other experimental observations including XPS data is proposed.

}, issn = {1463-9262}, doi = {10.1039/b815948c}, author = {Maity, Prasenjit and Gopinath, Chinnakonda S. and Bhaduri, Sumit and Lahiri, Goutam Kumar} } @article { ISI:000291421400015, title = {Selective hydrogenation of chloronitrobenzenes with an MCM-41 supported platinum allyl complex derived catalyst}, journal = {Applied Catalysis A-General}, volume = {399}, number = {1-2}, year = {2011}, month = {MAY}, pages = {117-125}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

A platinuin precatalyst (1) has been prepared by reacting [(eta(3)-C3H5)(4)Pt4Cl4] with surface functionalized MCM-41 with pendant -(CH2)(3)NH(CH2)(2)NH2 groups. For the hydrogenation of o-, m- and p-chloronitrobenzenes to the corresponding chloroanilines, 1 is found to be a highly active catalyst with good selectivities for them-and p-isomers. Its performance is superior to that of its palladium analogue and far superior to that of commercial (5\%) Pt/C or (5\%) Pt/Al2O3. Comparison of solid state and solution NMR data and other evidences indicate that on treatment with the functionalized MCM-41 support; [(eta(3)-C3H5)(4)Pt4Cl4] loses the ally! ligand. XPS data show that in the fresh catalyst Pt is present in the 2+ oxidation state. Based on these and analytical data, co-ordination by surface diamine and hydroxo groups to Pt2+ in 1 is suggested. In the used catalyst both Pt2+ and Pt are present but the amount of metallic platinum is similar to 16\% of the total. (C) 2011 Elsevier B.V. All rights reserved.

}, keywords = {Chloronitrobenzenes, Dehydrohalogenation, heterogeneous catalyst, MCM-41, Selective hydrogenation}, issn = {0926-860X}, doi = {10.1016/j.apcata.2011.03.044}, author = {Indra, Arindam and Rajamohanan, Pattuparambil R. and Gopinath, Chinnakonda S. and Bhaduri, Sumit and Lahiri, Goutam Kumar} } @article { ISI:000301955900026, title = {Selective recognition of fluoride and acetate by a newly designed ruthenium framework: experimental and theoretical investigations}, journal = {Dalton Transactions}, volume = {41}, number = {15}, year = {2012}, month = {FEB}, pages = {4484-4496}, type = {Article}, abstract = {

{An effective anion sensor, [Ru-II(bpy)(2)(H2L-)](+) (1(+)), based on a redox and photoactive {Ru-II(bpy)(2)} moiety and a new ligand (H3L = 5-(1H-benzo[d]imidazol-2-yl)-1H-imidazole-4-carboxylic acid), has been developed for selective recognition of fluoride (F-) and acetate (OAc-) ions. Crystal structures of the free ligand, H3L and [1](ClO4) reveal the existence of strong intramolecular and intermolecular hydrogen bonding interactions. The structure of [1](ClO4) shows that the benzimidazole N-H of H2L- is hydrogen bonded with the pendant carboxylate oxygen while the imidazole N-H remains free for possible hydrogen bonding interaction with the anions. The potential anion sensing features of 1(+) have been studied by different experimental and theoretical (DFT) investigations using a wide variety of anions, such as F-, Cl-, Br-, I-, HSO4-, H2PO4-, OAc- and SCN-. Cyclic voltammetry and differential pulse voltammetry established that 1(+) is an excellent electrochemical sensor for the selective recognition kof F- and OAc- anions. 1(+) is also found to be a selective colorimetric sensor for F- or OAc- anions where the MLCT band of the receptor at 498 nm is red shifted to 538 nm in the presence of one equivalent of F- or OAc- with a distinct change in colour from reddish-orange to pink. The binding constant between 1(+) and F- or OAc- has been determined to be logK = 7.61 or 7.88, respectively, based on spectrophotometric titration in CH3CN. The quenching of the emission band of 1(+) at 716 nm (lambda(ex) = 440 nm

}, doi = {10.1039/c2dt12126c}, author = {Kundu, Tanaya and Chowdhury, Abhishek Dutta and De, Dipanwita and Mobin, Shaikh M. and Puranik, Vedavati G. and Datta, Anindya and Lahiri, Goutam Kumar} } @article { ISI:000309885500028, title = {Strong metal-metal coupling in mixed-valent intermediates [Cl(L)Ru(mu-tppz)Ru(L)Cl](+), L = beta-diketonato ligands, tppz=2,3,5,6-tetrakis(2-pyridyl)pyrazine}, journal = {Dalton Transactions}, volume = {41}, number = {43}, year = {2012}, month = {SEP}, pages = {13429-13440}, publisher = {ROYAL SOC CHEMISTRY}, type = {Article}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Five diruthenium(II) complexes [Cl(L)Ru(mu-tppz)Ru(L)Cl](1-5) containing differently substituted beta-diketonato derivatives (1: L = 2,4-pentanedionato; 2: L = 3,5-heptanedionato; 3: L = 2,2,6,6-tetramethyl-3,5-heptanedionato; 4: L = 3-methyl-2,4-pentanedionato; 5: L = 3-ethyl-2,4-pentanedionato) as ancillary ligands (L) were synthesized and studied by spectroelectrochemistry (UV-Vis-NIR, electron paramagnetic resonance (EPR)). X-ray structural characterisation revealed anti (1, 2, 5) or syn (3) configuration as well as non-planarity of the bis-tridentate tppz bridge and strong d pi(Ru-II) -\> pi*(pyrazine, tppz) back-bonding. The widely separated one-electron oxidation steps, (RuRuII)-Ru-II/(RuRuIII)-Ru-II and (RuRuIII)-Ru-II/(RuRuIII)-Ru-III, result in large comproportionation constants (K-c) of \>= 10(10) for the mixed-valent intermediates. The syn-configurated 3(n) exhibits a particularly high K-c of 10(12) for n = 1+, accompanied by density functional theory (DFT)-calculated minimum Ru-N bond lengths for this (RuRuIII)-Ru-II intermediate. The electrogenerated mixed-valent states 1(+)-5(+) exhibit anisotropic EPR spectra at 110 K with average values \< g \> of 2.304-2.234 and g anisotropies Delta g = g(1)-g(3) of 0.82-0.99. Metal-to-metal charge transfer (MMCT) absorptions occur for 1(+)-5(+) in the NIR region at 1660 nm-1750 nm (epsilon approximate to 2700 dm(3) mol(-1) cm(-1), Delta nu(1/2) approximate to 1800 cm(-1)). DFT calculations of 1(+) and 3(+) yield comparable Mulliken spin densities of about 0.60 for the metal ions, corresponding to valence-delocalised situations (Ru-2.5)(2). Rather large spin densities of about -0.4 were calculated for the tppz bridges in 1(+) and 3(+). The calculated electronic interaction values (V-AB) for 1(+)-5(+) are about 3000 cm(-1), comparable to that for the Creutz-Taube ion at 3185 cm(-1). The DFT calculations predict that the (RuRuIII)-Ru-III forms in 12(+)-52(+) prefer a triplet (S = 1) ground state with Delta E (S = 0 - S = 1) similar to 5000 cm(-1). One-electron reduction takes place at the tppz bridge which results in species [Cl(L)Ru-II(mu-tppz(.-)) Ru-II(L)Cl](-) (1(.-)-3(.-), 5(.-)) which exhibit free radical-type EPR signals and NIR transitions typical of the tppz radical anion. The system 4(n) is distinguished by lability of the Ru-Cl bonds.

}, issn = {1477-9226}, doi = {10.1039/c2dt31763j}, author = {Kundu, Tanaya and Schweinfurth, David and Sarkar, Biprajit and Mondal, Tapan Kumar and Fiedler, Jan and Mobin, Shaikh M. and Puranik, Vedavati G. and Kaim, Wolfgang and Lahiri, Goutam Kumar} } @article { ISI:000318939700024, title = {Hydroxyapatite supported palladium catalysts for suzuki-miyaura cross-coupling reaction in aqueous medium}, journal = {Catalysis Science \& Technology}, volume = {3}, number = {6}, year = {2013}, month = {MAR}, pages = {1625-1633}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Supported palladium catalyst 1 has been prepared by the immobilisation of [Pd(COD)Cl-2] (COD = 1,5-cyclooctadiene) on hydroxyapatite. Catalyst 2 has been prepared by subsequent reduction of catalyst 1 with sodium borohydride in ethanol. Under similar reaction conditions, catalyst 1 with Pd2+, is found to be almost five times more active than 2. Using 1 as the catalyst and water as the solvent, reaction conditions for Suzuki-Miyaura cross-coupling reactions have been optimised under aerobic conditions. The best catalytic activities are observed in the presence of potassium carbonate as the base and tetrabutylammonium bromide as a promoter. Catalyst 1 has been tested for catalytic cross-coupling reactions with sixteen different, electronically neutral, electron rich, electron poor and sterically hindered aryl boronic acids, and several different aryl halides including aryl chlorides. More than thousand turnovers and high selectivities to the hetero-coupled products have been observed in most cases. For many substrates the turnovers with 1 are notably more than what has been reported with other supported catalysts in water. The recyclability and scale-up potential of catalyst 1 have been tested and found to be satisfactory. A negligible drop in activity is observed over ten recycles with an accumulated turnover number of similar to 30000.

}, issn = {2044-4753}, doi = {10.1039/c3cy00160a}, author = {Indra, Arindam and Gopinath, Chinnakonda S. and Bhaduri, Sumit and Lahiri, Goutam Kumar} }