Wai Yip Fan

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Organization: National University of Singapore , Singapore

Department: Department of Chemistry

Title: (PhD)

TOPICS

Organic Chemistry

Chemicals
References

A Robust Pentacoordinated Iron(II) Proton Reduction Catalyst Stabilized by a Tripodal Phosphine

Co-reporter:Chew Pheng Yap, Kaipeng Hou, Ashfaq A. Bengali, and Wai Yip Fan

Inorganic Chemistry September 18, 2017 Volume 56(Issue 18) pp:10926-10926

Publication Date(Web):August 28, 2017

DOI:10.1021/acs.inorgchem.7b01079

A pentacoordinated triphosphine benzenedithiolatoiron(II) complex containing a vacant site for binding has been prepared and characterized. The complex is found to be a robust proton reduction catalyst with an overpotential of 0.56 V and a turnover frequency of 2900 s–1 with respect to 0.28 M acetic acid as the proton source. A mechanism describing the electroproton reduction process has been proposed.

Highly-phosphorescent tungsten(0) carbonyl pyridyl-imidazole complexes as photosensitisers

Co-reporter:Jia Jin Lee;Chew Pheng Yap;Tsz Sian Chwee

Dalton Transactions 2017 vol. 46(Issue 33) pp:11008-11012

Publication Date(Web):2017/08/22

DOI:10.1039/C7DT02397A

Photoluminescence data are reported for two W(CO)4L complexes (L = 2-(1H-imidazol-2-yl)pyridine and 2-(2′-pyridyl)benzimidazole) in room-temperature solutions. The bidentate ligands consist of a pyridine and an imidazole moiety connected by a C–C bond. The complexes have been found to exhibit enhanced phosphorescence from the metal-to-ligand charge transfer (MLCT) excited state with quantum yields in the order of 10−3, almost two orders of magnitude higher than those reported for W(CO)4(diimine) complexes. One of the complexes W(CO)4(2-(2′-pyridyl)benzimidazole) can serve as an efficient visible-light photosensitiser for the isomerisation of aromatic alkenes with efficiency comparable to and even exceeding that of the well-studied ruthenium tris-bipyridine complex, Ru(bpy)Cl2.

Cyclopentadienyl iron dicarbonyl (CpFe(CO)2) derivatives as apoptosis-inducing agents

Co-reporter:H. T. Poh, P. C. Ho and W. Y. Fan

RSC Advances 2016 vol. 6(Issue 23) pp:18814-18823

Publication Date(Web):09 Feb 2016

DOI:10.1039/C5RA23891A

Iron has been found to serve multiple purposes besides being an oxygen carrier. Of particular note is the generation of deleterious free radicals which can lead to the formation of tumours. However, in this work, we have found that cyclopentadienyl iron carbonyl complexes CpFe(CO)2X (X = halide, NCS, BF4− and CpFe(CO)2) can induce apoptosis in breast cancer and HeLa cell lines. Normal cells are however unaffected. A detailed study on CpFe(CO)2I shows that the complex is metabolic-stable and easily permeable across a lipid barrier. Preliminary investigations into the mode of action suggest that a Fenton-type reaction caused by CpFe(CO)2 complexes may be related to cell death.

Metal-free catalytic hydrogen production from a polymethylhydrosilane–water mixture

Co-reporter:Chew Pheng Yap, Hwa Tiong Poh and Wai Yip Fan

RSC Advances 2016 vol. 6(Issue 7) pp:5903-5906

Publication Date(Web):08 Jan 2016

DOI:10.1039/C5RA23887K

Hydrogen gas is the most promising carbon-free energy carrier although its on-demand generation remains a formidable challenge. One of the potential pathways for generating hydrogen is through hydrolytic oxidation of organosilanes. Here, we demonstrate that the hydroxide ion OH− serves as a potent room-temperature metal-free catalyst in the hydrolytic oxidation of polymethylhydrosilane, PMHS to hydrogen gas and the corresponding silanol with a turnover number and turnover frequency in excess of 200 and 8 min−1 respectively. Kinetic studies suggest the hydrogen generation rate is first order with respect to PMHS and OH− but zero order with respect to water. The first step of the reaction, where the Si center of PMHS is attacked by the OH− ion, is believed to be the rate-determining step.

Inside Cover: Shape-Controlled Preparation of Basic Bismuth Nitrate Crystals with High Iodide-Removal Capacities (ChemNanoMat 2/2016)

Co-reporter:Choon Hwee Bernard Ng ; Wai Yip Fan

ChemNanoMat 2016 Volume 2( Issue 2) pp:

Publication Date(Web):

DOI:10.1002/cnma.201600011

Shape-Controlled Preparation of Basic Bismuth Nitrate Crystals with High Iodide-Removal Capacities

Co-reporter:Choon Hwee Bernard Ng ; Wai Yip Fan

ChemNanoMat 2016 Volume 2( Issue 2) pp:133-139

Publication Date(Web):

DOI:10.1002/cnma.201500179

Abstract

Bismuth compounds have generated much interest as agents for the removal of radioactive iodine. In this work, we present the shape-controlled preparation of basic bismuth nitrate crystals (BBN) in the form of Reuleaux triangles, hexagons, and deformed hexagon disks. Shape control was achieved through modulation of the effect of the shape-directing agent 2,3-bis(2-pyridyl)pyrazine (dpp). The crystals were shown to be capable of iodide removal through reaction with I⁻ to form BiOI. Depending on the degree of saturation, the resultant solids can exhibit colors ranging from yellow (unsaturated) to orange (saturated). Sedimentation of the products facilitates its removal after use. While the removal capacities did not depend on the crystal morphology, the Reuleaux triangle disks exhibited faster reaction rates than the other two shapes. With improved removal capacities of up to 3.6 mmol g⁻¹, fast removal kinetics, good selectivity, and capture irreversibility, the BBN crystals show good potential as agents for radioactive iodine removal.

Uncovering Metastable α-Ag2MoO4 Phase Under Ambient Conditions. Overcoming High Pressures by 2,3-Bis(2-pyridyl)pyrazine Doping

Co-reporter:Choon Hwee Bernard Ng and Wai Yip Fan

Crystal Growth & Design 2015 Volume 15(Issue 6) pp:3032

Publication Date(Web):May 4, 2015

DOI:10.1021/acs.cgd.5b00455

The study of metastable phases has been elusive due to their propensity to convert to the stable phase. In this work, 3-bis(2-pyridyl)pyrazine (dpp)-doping was successfully used to relieve the high pressures required for the formation of metastable α-Ag2MoO4. α-Ag2MoO4 spheres were prepared via solution-phase precipitation under ambient conditions with the addition of dpp. While the properties of β-Ag2MoO4 have been well-studied, the difficulty in preparing the α-phase has limited its investigations to theoretical calculations. The overdue synthesis of α-Ag2MoO4 allowed empirical snapshots of its electronic and optical properties. The spheres show absorption in the visible/near-IR regions, and the band gap was determined to be 1.26 eV. Unlike β-Ag2MoO4, which is known to decay into Ag filaments on electron irradiation, the α-Ag2MoO4 spheres maintain their structural and electronic integrity. The inclusion of dpp into the crystal lattice is used to explain the experimental observations.

Stable manganese carbonyl radicals as a rapid colorimetric thiol and hydrazine sensor

Co-reporter:Hwa Tiong Poh, Tsz Sian Chwee and Wai Yip Fan

RSC Advances 2015 vol. 5(Issue 20) pp:15159-15163

Publication Date(Web):27 Jan 2015

DOI:10.1039/C4RA16483K

Blue cyclopentadienyl manganese dicarbonyl anilinyl radical complexes have been developed as a rapid and sensitive colorimetric thiol and hydrazine sensor with sensitivity limits approaching 3 ppm.

Group VI transition metal carbonyl hydrosulfides Na[M(CO)5(SH)] (M = Cr, Mo, W) as water-soluble H2S-releasing agents

Co-reporter:Hwa Tiong Poh, Ashfaq A. Bengali and Wai Yip Fan

RSC Advances 2015 vol. 5(Issue 14) pp:10703-10706

Publication Date(Web):07 Jan 2015

DOI:10.1039/C4RA14924F

A class of water-soluble Group 6 transition metal carbonyl complexes carrying the SH− ligand Na[M(CO)5(SH)] (M = Cr, Mo, W) is prepared and shown to release H2S under mild conditions with no decarbonylation. Preliminary studies on mammary epithelial cells have shown that both Na[Mo(CO)5SH] reactant and Mo(CO)5(solvent) product are non-cytotoxic.

Proton reduction using cobalt glyoximes with isothiocyanate and aniline axial ligands

Co-reporter:Wai Yip Fan, Zi Bin Tan, Jingzhi Iris Koh

Polyhedron 2015 Volume 96() pp:38-43

Publication Date(Web):16 August 2015

DOI:10.1016/j.poly.2015.04.030

Cobaloxime model complexes containing aniline derivatives and isothiocyanate as the axial ligands Co(dmgH)2XY (dmgH = dimethylglyoxime, X = NCS, Cl and Y = aniline, pyridine) have been synthesized and used as proton reduction catalysts. Using acetic acid as the proton source in acetonitrile, cyclic voltammetry studies have shown that these complexes are comparable to the well-known Co(dmgH)2(pyridine)Cl complex as a potent catalyst in terms of the overpotential and catalytic efficiency of proton reduction. In particular, we have shown that aniline derivatives can be used as possible pyridine alternatives in cobaloximes in our continuing search for an even more efficient proton reduction catalyst.Cobalt diglyoxime complexes bearing aniline and isothiocyanate axial ligands are efficient proton reduction catalysts.

Reuleaux Triangle Disks: New Shape on the Block

Co-reporter:Choon Hwee Bernard Ng

Journal of the American Chemical Society 2014 Volume 136(Issue 37) pp:12840-12843

Publication Date(Web):July 29, 2014

DOI:10.1021/ja506625y

We report here the unprecedented preparation of Reuleaux triangle disks. The hydrolysis and precipitation of bismuth nitrate in an ethanol–water system with 2,3-bis(2-pyridyl)pyrazine yielded basic bismuth nitrate Reuleaux triangle disks. Analysis of the intermediates provided insights into the mystery behind the formation of the Reuleaux triangle disk, revealing a unique growth process. The report of a facile method to prepare crystals of a novel shape in high yield, with good homogeneity, and with excellent reproducibility is expected to unlock new research directions in multiple disciplines.

Electrocatalytic hydrogen generation by a trithiolato-bridged dimanganese hexacarbonyl anion with a turnover frequency exceeding 40000 s−1

Co-reporter:Kaipeng Hou, Hwa Tiong Poh and Wai Yip Fan

Chemical Communications 2014 vol. 50(Issue 50) pp:6630-6632

Publication Date(Web):02 May 2014

DOI:10.1039/C4CC02016B

An unusual ionic manganese model complex [Mn(bpy)3]+[(CO)3Mn(μ-SPh)3Mn(CO)3]−(bpy: 2,2′-bipyridine) has been synthesized, which bears some structural resemblance to the active site of [FeFe] hydrogenase. An overpotential of 0.61 V has been determined for the electrocatalytic proton reduction using this complex in CH3CN with CF3COOH as the proton source. A turnover frequency of 44600 s−1 is achieved at high scan rates and in the presence of a large amount of acid.

Electrocatalytic proton reduction catalyzed by a dimanganese disulfide carbonyl complex containing a redox-active internal disulfide bond

Co-reporter:Kaipeng Hou and Wai Yip Fan

Dalton Transactions 2014 vol. 43(Issue 45) pp:16977-16980

Publication Date(Web):25 Sep 2014

DOI:10.1039/C4DT02361G

A dimanganese hexacarbonyl complex [(Mn(CO)3)2(μ-SC6H4-o-S-S-C6H4-o-μ-S-)] containing an elongated disulfide bond electrocatalyses proton reduction at moderate overpotentials of 0.55 to 0.65 V. Cyclic voltammetric, infrared spectroscopy and computational studies suggest that the redox-active sulfur atoms of the disulfide bond serve as the initial reduction site.

Preparation of Ag Stellar Dendrites: Modeling the Growth of Stellar Snowflakes

Co-reporter:Choon Hwee Bernard Ng and Wai Yip Fan

Crystal Growth & Design 2014 Volume 14(Issue 11) pp:6067-6072

Publication Date(Web):September 17, 2014

DOI:10.1021/cg5012204

The synthesis of Ag stellar dendrites was achieved using a solution-phase method by modeling the growth of stellar snowflakes. In the synthesis, 2,3-bis(2-pyridyl)pyrazine (dpp) acted as the growth-directing agent, forming hexagonal structures that served as the nuclei for the growth of stellar dendrites. Coupled with the careful control of experimental parameters to achieve a balance between reaction and diffusion rates, uniform and directional growth ensued, yielding symmetrical stellar dendrites represented by {111} facets. The influences of experimental conditions were investigated by analyzing the products formed under varied reaction and diffusion rates. The results were organized into an empirical chart that can serve as a visual reference to determine the experimental modifications required to prepare stellar dendrites. Time-dependence studies were carried out to elucidate the mechanism of growth into the unique dendritic patterns. SEM and HRTEM imaging of the intermediate structures revealed that the growth had occurred via oriented attachment of ∼10 nm Ag grains.

Catalytic hydrogen evolution from hydrolytic oxidation of organosilanes with silver nitrate catalyst

Co-reporter:Alan Kay Liang Teo and Wai Yip Fan

RSC Advances 2014 vol. 4(Issue 71) pp:37645-37648

Publication Date(Web):13 Aug 2014

DOI:10.1039/C4RA05669H

In the light of uncertainty over the amount of recoverable fossil fuel reserves, hydrogen is touted to be a promising energy carrier in the future. Nevertheless, hydrogen storage remains a daunting challenge but a potential reaction for the generation of hydrogen on demand is the hydrolytic oxidation of organosilanes. Here, we demonstrate that silver nitrate, a readily available ionic salt, can catalyze the hydrolysis of organosilanes to produce hydrogen and organosilanols. In particular, turnover numbers and turnover frequencies in excess of 5 × 103 and 102 min−1 respectively are obtainable for the hydrolysis of triethylsilane at room temperature. This proposed silver nitrate mediated system is, by far, the simplest and cheapest catalytic hydrolysis of organosilanes. Results from the kinetic studies suggested a mechanistic scenario in which the hydrolysis of organosilanes is third order overall and first order in organosilane, water, and catalyst. The high hydrogen yield observed makes the silver nitrate catalyst an attractive material for hydrogen evolution.

A persistent manganese carbonyl radical with infrared absorption and fluorescence modality

Co-reporter:Hwa Tiong Poh, Jun Wei Kee, Tsz Sian Chwee, Wai Yip Fan

Journal of Organometallic Chemistry 2014 Volume 759() pp:11-14

Publication Date(Web):1 June 2014

DOI:10.1016/j.jorganchem.2014.02.015

•A fluorescent manganese carbonyl radical complex.•High fluorescent quantum yield of 0.6.•Long-lived radical with life time of more than a week.A manganese carbonyl radical complex, Cp∗Mn(CO)2(2-aminoanthracenyl) was prepared and characterised using IR, ESR and UV–visible absorption and emission spectroscopic methods. The radical persists in solution for more than one week and its ESR spectrum shows a sextet of lines which is consistent with a metal-centred radical complex. Two broad intense electronic absorption bands were observed, corresponding to the 2-aminoanthracene ligand-to-ligand transition (300–420 nm) and a ligand-to-metal charge transfer (LCMT) transition centred at 685 nm. Cp∗Mn(CO)2(2-aminoanthracenyl) exhibits fluorescence with a quantum yield of 0.6 and halflife of 6.4 ns upon excitation at 350 nm.A long-lived fluorescent Cp∗Mn(CO)2(2-aminoanthracenyl) radical has been prepared and characterized.

Colloidal Beading: Sonication-Induced Stringing of Selenium Particles

Co-reporter:Choon Hwee Bernard Ng and Wai Yip Fan

Langmuir 2014 Volume 30(Issue 25) pp:7313-7318

Publication Date(Web):2017-2-22

DOI:10.1021/la5012617

We report the preparation of monodispersed Se colloidal aggregates (dimers and trimers) via sonication-induced aggregation of spherical monomers. Control over the size and morphology of the products was achieved by changing the aging and sonication times, respectively. The possible mechanisms for the formation of colloidal aggregates were discussed. This method can provide a simple and versatile approach to the production of colloidal molecules of particles composed of different materials, which will be useful for fundamental studies related to colloidal systems.

The Dithiolate-Bridged Diiron Hexacarbonyl Complex Na2[(μ-SCH2CH2COO)Fe(CO)3]2 as a Water-Soluble PhotoCORM

Co-reporter:Hwa Tiong Poh, Bai Ting Sim, Tsz Sian Chwee, Weng Kee Leong, and Wai Yip Fan

Organometallics 2014 Volume 33(Issue 4) pp:959-963

Publication Date(Web):February 3, 2014

DOI:10.1021/om401013a

The water-soluble dimercaptopropanoate-bridged diiron hexacarbonyl complex Na2[(μ-SCH2CH2COO)Fe(CO)3]2 has been prepared, and the X-ray crystal structure and infrared, UV–visible, and ESI spectra of the complex have been obtained. The complex is shown to behave as a photoCORM, whereby all six CO ligands are released within 30 min of visible-light irradiation. Gas-phase FTIR spectroscopy has been used to quantify the release of CO into the headspace above the aqueous solution. The resulting product, tentatively assigned to an iron thiolate salt, is also water-soluble. Cell viability studies show that Na2[(μ-SCH2CH2COO)Fe(CO)3]2 is not cytotoxic toward normal epithelial cells.

Infrared studies of halide binding with CpMn(CO)2X complexes where X = ligands bearing the O–H or N–H group

Co-reporter:Jun Wei Kee, Wai Yip Fan

Journal of Organometallic Chemistry 2013 729() pp: 14-19

Publication Date(Web):

DOI:10.1016/j.jorganchem.2013.01.019

Stoichiometric H2 production from H2O upon Mn2(CO)10 photolysis

Co-reporter:Jun Wei Kee, Che Chang Chong, Chun Keong Toh, Yuan Yi Chong, Wai Yip Fan

Journal of Organometallic Chemistry 2013 724() pp: 1-6

Publication Date(Web):

DOI:10.1016/j.jorganchem.2012.10.034

Significant O–H Bond Weakening in CpMn(CO)2(CH3OH): Evidence for the Generation of the CpMn(CO)2(CH3O) Radical upon H Atom Abstraction by O2

Co-reporter:Jun Wei Kee, Tsz Sian Chwee, Xiang Yeow Tan, Richard D. Webster, and Wai Yip Fan

Organometallics 2013 Volume 32(Issue 15) pp:4359-4365

Publication Date(Web):July 23, 2013

DOI:10.1021/om400504c

The UV–visible photolysis of CpMn(CO)3 in methanol generates CpMn(CO)2(CH3OH), which upon H atom abstraction using either O2, dpph, or H2O2 gives the CpMn(CO)2(CH3O) radical complex. The radical with a lifetime of 10 to 20 min has been mainly characterized using FTIR and ESR spectroscopy and chemical oxidation studies. Together with density functional theory calculations, it is shown that the O–H bond is significantly weakened in the CpMn(CO)2(CH3OH) complex compared to free methanol. NBO spin density analysis suggests that the bond cleavage is facilitated by the formation of the CpMn(CO)2(CH3O) radical in which the electron spin is localized at the metal center rather than at the oxygen atom.

Ruthenium carbonyl-catalysed Si–heteroatom X coupling (X = S, O, N)

Co-reporter:Chun Keong Toh, Hwa Tiong Poh, Ching Si Lim, Wai Yip Fan

Journal of Organometallic Chemistry 2012 717() pp: 9-13

Publication Date(Web):

DOI:10.1016/j.jorganchem.2012.07.024

Addition of pyrroles onto terminal alkynes catalyzed by a dinuclear ruthenium (II) complex

Co-reporter:Sze Tat Tan, Yew Chin Teo, Wai Yip Fan

Journal of Organometallic Chemistry 2012 s 708–709() pp: 58-64

Publication Date(Web):

DOI:10.1016/j.jorganchem.2012.02.017

Catalytic Hydrosilylation of Carbonyls via Re(CO)5Cl Photolysis

Co-reporter:Chun Keong Toh, Yin Ngai Sum, Wai Kit Fong, Siau Gek Ang, and Wai Yip Fan

Organometallics 2012 Volume 31(Issue 10) pp:3880-3887

Publication Date(Web):May 16, 2012

DOI:10.1021/om2012634

The hydrosilylation reaction between silanes and various carbonyl substrates such as aldehyde, ketone, ester, and carbonate has been catalyzed by Re(CO)5Cl UV photolysis. Kinetic studies have shown that the reaction is favored for the least sterically hindered silanes with aldehydes followed by aliphatic ketones. The IR spectrum of the rhenium carbonyl dimer HRe2(CO)9(SiR3) has been recorded in the reaction mixture. This complex is believed to be the resting state of the active catalyst Re(CO)4SiR3, which could be released upon photactivation. A catalytic mechanism involving this species has been proposed and shown to be thermodynamically feasible using computational studies. In addition, the relative hydrosilylation rates among the various carbonyl substrates can be explained using the same mechanism.

Hydrogen Generation from Water upon CpMn(CO)3 Irradiation in a Hexane/Water Biphasic System

Co-reporter:Jun Wei Kee, Yong Yao Tan, Bert H. G. Swennenhuis, Ashfaq A. Bengali, and Wai Yip Fan

Organometallics 2011 Volume 30(Issue 8) pp:2154-2159

Publication Date(Web):March 23, 2011

DOI:10.1021/om1010403

Photolysis of CpMn(CO)3 in a hexane/water biphasic system has been shown to generate hydrogen peroxide and hydrogen in 40−50% yield. Photolysis of the title compound results in loss of a CO ligand followed by coordination of a water molecule. The initially formed CpMn(CO)2(H2O) intermediate was detected using time-resolved IR spectroscopy. The cyclopentadiene (CpH) monomer is generated as the major product, formed by the transfer of an H atom from the coordinated H2O solvent to the Cp ring. A simple mechanism for H2 generation is proposed on the basis of deuteration studies which demonstrate the production of D2 and CpD upon photolysis of CpMn(CO)3 in a hexane/D2O biphasic system.

Photocatalytic Transformation of Organic and Water-Soluble Thiols into Disulfides and Hydrogen under Aerobic Conditions Using Mn(CO)5Br

Co-reporter:Kheng Yee Desmond Tan, Guan Foo Teng, and Wai Yip Fan

Organometallics 2011 Volume 30(Issue 15) pp:4136-4143

Publication Date(Web):July 5, 2011

DOI:10.1021/om200461j

The photolysis of Mn(CO)5Br with thiols under aerobic conditions at room temperature produces the corresponding disulfides in high yields, accompanied by the evolution of hydrogen as the only other product. This transformation is a greener route toward the synthesis of disulfides and exhibits 100% atom economy. The catalytic system possesses high chemoselectivity, as evidenced by high disulfide yields even in the presence of numerous functional groups. A mechanism has been proposed to involve free radical species and is based on fac-Mn(CO)3(RSH)2Br being an important catalytic intermediate. Mn(CO)5Br is also able to catalyze the conversion of naturally occurring water-soluble thiols such as cysteine and glutathione. Coupled with suitable enzymes that regenerate thiols from disulfides using proton sources, it is possible to envisage a combined catalytic cycle that is able to reduce protons to hydrogen efficiently.

Catalytic Hydrogen Generation from the Hydrolysis of Silanes by Ruthenium Complexes

Co-reporter:Sze Tat Tan, Jun Wei Kee, and Wai Yip Fan

Organometallics 2011 Volume 30(Issue 15) pp:4008-4013

Publication Date(Web):July 7, 2011

DOI:10.1021/om200256h

Dimeric Ru(II) complexes Ru2(CO)4L2X4 (L = CO or PPh3; X = Cl or Br) have been found to catalyze the hydrolysis of silanes to produce hydrogen gas and silanols with turnover numbers in excess of 104 at room temperature. Deuteration and mass spectrometric studies have established that the hydrogen gas originates from one hydrogen atom from water and the other from silane. Ruthenium hydride intermediates have been detected in the NMR spectrum during the early stage of the reaction, while the FTIR spectra of more stable complexes such as Ru(CO)2(PPh3)(THF)Br2 and Ru(CO)2(PPh3)2(H)Br have been recorded upon completion of catalysis. A mechanism has been proposed to account for the ruthenium-catalyzed silane hydrolysis based on the experimental data.

Catalytic rate enhancement observed for alkyne hydrocarboxylation using ruthenium carbonyl-capped nanostructures

Co-reporter:Yuan Yi Chong, Wei Bin Goh, Sze Tat Tan, Wai Yip Fan

Journal of Colloid and Interface Science 2010 Volume 348(Issue 2) pp:559-564

Publication Date(Web):15 August 2010

DOI:10.1016/j.jcis.2010.04.077

Surface functionalization of Ag nanocubes and nanoparticles with catalytically active ruthenium carbonyl oligomers has been carried out successfully. These functionalized nanostructures catalyze hydrocarboxylation onto terminal alkynes at significantly enhanced rates (33 times) compare to those observed for free ruthenium oligomers. The rate enhancement is facilitated by adsorption of substrates on the surface of the nanoparticles, thus bringing them into close proximity with the catalyst. The size and shape of the Ag nanostructures were retained, indicating that the metallic cores act mainly as a docking site.[Ru2(MPA)4(CO)4]n oligomers-capped Ag nanocubes and nanoparticles show significant catalytic rate enhancement for alkyne hydrocarboxylation as compared to free ruthenium oligomers.

Ligand-Controlled Regio- and Stereoselective Addition of Carboxylic Acids Onto Terminal Alkynes Catalyzed by Carbonylruthenium(0) Complexes

Co-reporter:Sze Tat Tan

European Journal of Inorganic Chemistry 2010 Volume 2010( Issue 29) pp:4631-4635

Publication Date(Web):

DOI:10.1002/ejic.201000579

Abstract

The addition of carboxylic acids onto terminal alkynes was catalyzed by mononuclear ruthenium(0) complexes to give enol esters in high yields. By using ligands with different electronic properties, product selectivity was achieved. E-enol esters were preferentially produced when tricarbonyl(η⁴-diene)ruthenium complexes were used; while geminal enol esters were produced when tricarbonylbis(phosphane)ruthenium complexes were used.

CpMn(CO)3-Catalyzed Photoconversion of Thiols into Disulfides and Dihydrogen

Co-reporter:Kheng Yee Desmond Tan, Jun Wei Kee, and Wai Yip Fan

Organometallics 2010 Volume 29(Issue 20) pp:4459-4463

Publication Date(Web):September 7, 2010

DOI:10.1021/om1005947

The UV photolysis of CpMn(CO)3 with thiols at room temperature effected the following catalytic transformation: 2 RSH → R2S2 + H2. This reaction is a cleaner and greener way toward making disulfides, as it produces dihydrogen as the only side-product. The manganese system exhibits high chemoselectivity as the transformation proceeds efficiently even in the presence of numerous functional groups. A manganese dicarbonyl complex, CpMn(CO)2RSH, and cyclopentadiene have also been detected using FTIR and NMR spectroscopic techniques, respectively. Based on our experimental data, a mechanism has been proposed to account for the catalysis.

Alumina-Template Synthesis of Fluorescent RuO2 Nanotubes Derived from Ru3(CO)12 Clusters

Co-reporter:H. Tan;W. Y. Fan;E. Ye

Advanced Materials 2006 Volume 18(Issue 5) pp:619-623

Publication Date(Web):2 MAR 2006

DOI:10.1002/adma.200501356

RuO₂ nanotubes with diameters of 15–25 nm and up to 3 μm in length have been prepared by the thermal decomposition of Ru₃(CO)₁₂ inside alumina templates. The RuO₂ (110) planes grow along the long axis of the straight crystalline nanotubes. The growth of these fluorescent nanotubes appears to have proceeded via mononuclear ruthenium carbonyl intermediates (see Figure).

Self-Organization of Spherical, Core–Shell Palladium Aggregates by Laser-Induced and Thermal Decomposition of [Pd(PPh3)4]

Co-reporter:Enyi Ye;Hua Tan;Shuping Li Dr.

Angewandte Chemie 2006 Volume 118(Issue 7) pp:

Publication Date(Web):30 DEC 2005

DOI:10.1002/ange.200503408

Metall mittendrin: Kugelförmige Kern-Schale-Aggregate mit einheitlicher Größe ((100±20) nm; siehe Bild) entstehen durch Photozersetzung von [Pd(PPh₃)₄], die den Metallkern liefert. Um diesen Kern aggregieren kleinere Pd-Nanokristalle und Phosphane aus der thermischen Zersetzung von verbliebener Ausgangsverbindung. Längere Bestrahlung oder thermische Behandlung allein führen ausschließlich zu Kern- bzw. Schalenstrukturen, sodass die Nanopartikelstruktur gesteuert werden kann.

Self-Organization of Spherical, Core-Shell Palladium Aggregates by Laser-Induced and Thermal Decomposition of [Pd

Co-reporter:Enyi Ye, Hua Tan, Shuping Li,Wai Yip Fan

Angewandte Chemie International Edition 2006 45(7) pp:1120-1123

Publication Date(Web):

DOI:10.1002/anie.200503408

FTIR Studies of Iron–Carbonyl Intermediates in Allylic Alcohol Photoisomerization

Co-reporter:Thiam Seong Chong;Sze Tat Tan Dr.

Chemistry - A European Journal 2006 Volume 12(Issue 19) pp:

Publication Date(Web):27 APR 2006

DOI:10.1002/chem.200600053

The 532 or 355 nm laser-induced photoisomerization of allylic alcohols to aldehydes catalyzed by [Fe₃(CO)₁₂] or [Fe(CO)₄PPh₃] in hexane was investigated. The Fourier transform infrared (FTIR) absorption spectra of iron–carbonyl intermediate species such as [Fe(CO)₅], [Fe(CO)₄(R-C₃H₄OH)], and more importantly the π-allyl iron–carbonyl hydride species [FeH(CO)₃(R-C₃H₃OH)] (R=H, Me, Ph) were recorded during the catalytic process using [Fe₃(CO)₁₂] as the catalytic precursor. When [Fe(CO)₄PPh₃] was photolyzed with 355 nm, [FeH(CO)₃(R-C₃H₃OH)] was also generated indicating the common occurrence of the species in these two systems. The π-allyl hydride species is long believed to be a key intermediates and its detection here lends support to the π-allyl mechanism of the photoisomerization of allyl alcohols.

TR-FTIR absorption spectroscopy of transition metal carbonyl radicals generated by photodissociation of metal–metal bonds, by halogen abstraction or by radical ligand substitution

Co-reporter:Thiam Seong Chong, Peng Li, Weng Kee Leong, Wai Yip Fan

Journal of Organometallic Chemistry 2005 Volume 690(Issue 18) pp:4132-4138

Publication Date(Web):15 September 2005

DOI:10.1016/j.jorganchem.2005.06.015

Three methods of obtaining time-resolved Fourier-Transform infrared (TR-FTIR) absorption spectra of transition metal carbonyl radicals in hexane are reported here. For the first method, CpM(CO)2L and Cp*M(CO)2L (M = Mo, W; L = CO, PR3) radicals have been generated by photodissociation of the corresponding metal–metal bonded dimers. Radicals of formula M(CO)4L (M = Mn, Re; L = CO, PR3, AsPh3, SbPh3) and CpM(CO)n (M = Fe, Mo; n = 2, 3) have been produced via the second method which is halogen abstraction of the transition metal carbonyl halides using CpMo(CO)3 radical. For the third method, fast radical ligand substitution kinetics has been exploited to generate CpMo(CO)2PR3 radicals from CpMo(CO)3 in the presence of free phosphines. An assessment of the three methods with respect to TR-FTIR spectroscopic detection of radicals was also discussed.Time-resolved FTIR studies of reversible and irreversible processes involving transition metal carbonyl radicals.

Electrocatalytic hydrogen generation by a trithiolato-bridged dimanganese hexacarbonyl anion with a turnover frequency exceeding 40000 s−1

Co-reporter:Kaipeng Hou, Hwa Tiong Poh and Wai Yip Fan

Chemical Communications 2014 - vol. 50(Issue 50) pp:NaN6632-6632

Publication Date(Web):2014/05/02

DOI:10.1039/C4CC02016B

Electrocatalytic proton reduction catalyzed by a dimanganese disulfide carbonyl complex containing a redox-active internal disulfide bond

Co-reporter:Kaipeng Hou and Wai Yip Fan

Dalton Transactions 2014 - vol. 43(Issue 45) pp:NaN16980-16980

Publication Date(Web):2014/09/25

DOI:10.1039/C4DT02361G

A novel iron complex for highly efficient catalytic hydrogen generation from the hydrolysis of organosilanes

Co-reporter:Alan Kay Liang Teo and Wai Yip Fan

Chemical Communications 2014 - vol. 50(Issue 54) pp:NaN7194-7194

Publication Date(Web):2014/05/15

DOI:10.1039/C4CC02852J

Hydrolytic oxidation of organosilanes based on an iron catalyst is described for the first time. The novel iron complex, [Fe(C6H5N2O)(CO)(MeCN)3][PF6], exhibits excellent mediating power in the catalytic hydrolysis of organosilanes to produce dihydrogen and organosilanols with turnover numbers approaching 104 and turnover frequencies in excess of 102 min−1 under ambient conditions.