Pankaj Das

An alternative strategy to an electron rich phosphine based carbonylation catalystThis paper is dedicated to the memory of Prof. Noel McAuliffe in recognition of his contribution to phosphine chemistry and friendship.

The complexes [Rh(CO)Cl(2-Ph2PC6H4COOMe)], 1, and trans-[Rh(CO)Cl(2-Ph2PC6H4COOMe)2], 2, have been synthesized by the reaction of the dimer [Rh(CO)2Cl]2 with 2 and 4 molar equivalents of 2-(diphenylphosphino)methyl benzoate. The complexes 1 and 2 show terminal ν(CO) bands at 1979 and 1949 cm−1 respectively indicating high electron density at the metal centre. The molecular structure of the complex 2 has been determined by single crystal X-ray diffraction. The rhodium atom is in a square planar coordination environment with the two phosphorus atoms trans to each other; the ester carbonyl oxygen atom of the two phosphine ligands points towards the rhodium centre above and below the vacant axial sites of the planar complex. The rhodium–oxygen distances (Rh⋯O(49) 3.18 A; Rh⋯O(19) 3.08 A) and the angle O(19)⋯Rh⋯O(49) 179° indicate long range intramolecular secondary Rh⋯O interactions leading to a pseudo-hexacoordinated complex. The complexes 1 and 2 undergo oxidative addition (OA) reactions with CH3I to produce acyl complexes [Rh(COCH3)ClI(2-Ph2PC6H4COOMe)], 4, and trans-[Rh(COCH3)ClI(2-Ph2PC6H4COO-Me)(2-Ph2PC6H4COOMe)], 5, and the kinetics of the reactions reveal that the complex 1 undergoes faster OA reaction than that of the complex 2. The catalytic activity of the complexes 1 and 2 in the carbonylation of methanol were higher than that of the well known species [Rh(CO)2I2]− and the complex 1 shows higher activity than 2.

Catalytic activity of dicarbonylrhodium complexes of aminobenzoic acid ligands on carbonylation of alcohol

Abstract Rhodium(I) complexes of the type, [Rh(CO) 2 ClL] ( 1 ), where L=2-aminobenzoic acid ( a ), 3-aminobenzoic acid ( b ) and 4-aminobenzoic acid ( c ), have been synthesised. Oxidative addition (OA) of complexes 1 with electrophiles like RI (R=CH 3 , C 2 H 5 ) produce Rh(III) complexes of the type [Rh(CO)(COCH 3 )IClL] ( 2 ) and [Rh(CO)(COC 2 H 5 )IClL] ( 3 ). The OA reactions of complexes 1 with RI follow a two stage kinetics and the observed rate constants are in the order 1 b > 1 c > 1 a irrespective of stages. The complexes 1 show higher catalytic activity for carbonylation of methanol and ethanol than that of the well known species [Rh(CO) 2 I 2 ] − .

Rhodium(I) carbonyl complexes of triphenylphosphine chalcogenides and their catalytic activity

Rhodium(I) carbonyl complexes [Rh(CO)2ClL] where L = Ph3PO, Ph3PS and Ph3PSe, were synthesized and characterized by elemental analysis, i.r. and by 1H-, 13C- and 31P-n.m.r. spectroscopy. The vBD;(CO) band frequencies in the complexes follow the order: Ph3PO > Ph3PS > Ph3PSe, in keeping with the hard/soft nature of the interactions. The complexes undergo oxidative additions with electrophiles such as MeI, PhCH2Cl and I2 to give, e.g. [Rh(CO)(COMe)ClIL] which react with PPh3 to give trans-[Rh(CO)Cl(PPh3)2]. The catalytic activity of the [Rh(CO)2ClL] complexes in carbonylation of MeOH is higher than that of the well-known [Rh(CO)2I2]− species.

Phosphine-stabilized Pd nanoparticles supported on silica as a highly active catalyst for the Suzuki–Miyaura cross-coupling reaction

We have prepared a silica supported palladium nanocatalyst (PdNP@PPh2–SiO2) with high dispersion via a one-step reaction between commercially available 2-diphenylphosphinoethyl-functionalized silica gel (PPh2–SiO2) and PdCl2 without the assistance of an external reductant or stabilizer. The catalyst was well characterized by N2-adsorption, XRD, HRTEM, SEM-EDX and ICP analyses. The supported catalyst exhibited excellent activity for the Suzuki–Miyaura cross-coupling reactions of aryl halides (including aryl chlorides) with arylboronic acids. The facile synthesis of the catalyst combined with high product yields at relatively low catalyst loading (<0.5 mol%) represents one of the most efficient silica supported heterogeneous systems for the Suzuki coupling of aryl chlorides. The catalyst could be reused several times without compromising its activity.

Carbonyl complexes of ruthenium(II) with unsymmetrical phosphine–phosphinesulfide ligands of the type Ph2P(CH2)nP(S)Ph2, n=1–4

Reaction of [Ru(CO) 2Cl 2] n with ligands Ph 2P(CH 2)nP(S)Ph 2 (n0/1(a), 2(b), 3(c), 4(d)) in 1:1 molar ratio produces complex cis[Ru(CO) 2Cl 2(PS/S)](1a)(PS/S0/h 2-(P, S) coordinated) and cis-[Ru(CO)2Cl2(P/S)](1b/d)(P/S0/h 1-(P) coordinated), while 1:2 molar ratio yields complex of the type cis-[Ru(CO) 2Cl 2(P/S) 2](2a/d). The complex 2a undergoes partial decarbonylation reaction inCH 2Cl 2/hexanesolutiontogiveanewchelatedcomplex[Ru(CO)Cl(PS/S) 2]Cl(2a?).AbstractionofhalidewithAgClO 4fromthe non-chelated complexes 1b/d and 2a/d afford corresponding chelated complexes [Ru(CO) 2Cl(PS/S)](ClO 4)(3b/d) and [Ru(CO) 2(PS/S) 2](ClO 4)2(4a/d). The molecular structure of the complex 2a? has been determined by single crystal X-ray diffraction. The ruthenium atom is at the centre of slightly distorted octahedral structure having the two phosphorus atoms of the twochelatedP,Scoordinatedligandsattrans toeachother,oneCOgroupandClatomcompletingthecoordinationsphere.Other complexes have been characterized by elemental analysis, IR, 1H and 31P {H} NMR spectroscopy.

A novel iron(III)-based heterogeneous catalyst for aqueous oxidation of alcohols using molecular oxygen

A novel silica supported iron(III)-based heterogeneous catalyst (FeCl3-imine@SiO2) has been synthesized and characterized by several techniques, such as FTIR, nitrogen adsorption analysis (BET), SEM-EDX, XRD, EPR, AAS and XPS analyses. The catalyst showed excellent activity for selective oxidation of alcohols to corresponding carbonyl compounds in water under atmospheric pressure of oxygen without using any additive. Notably, the heterogeneous catalyst showed remarkable improvement over its homogeneous counterpart, which might be attributable to the synergic effect between the metal and the supported ligand. The catalyst could be easily recovered by simple filtration and reused several times without compromising its activity. A wide range of primary and secondary alcohols including heterocyclic alcohols are tolerated as substrates.

Biogenic synthesis of palladium nanoparticles and their applications as catalyst and antimicrobial agent

This paper describes a simple in-situ process of synthesizing highly dispersed palladium nanoparticles (PdNPs) using aqueous leaf extract of GarciniapedunculataRoxb as bio-reductant and starch (0.3%) as bio-stabilizer. The PdNPs are characterized by techniques like FTIR, TEM, SEM-EDX, XRD and XPS analysis. It is worthnoting thatwhen the synthesis of nanoparticles was carried out in absence of starch, agglomeration of particles has been noticed.The starch-assisted PdNPs showed excellent aqueous-phase catalytic activities for three important reactions: the Suzuki-Miyaura cross-coupling reactions of aryl halides (aryl bromides and iodides) with arylboronic acids; selective oxidations of alcohols to corresponding carbonyl compounds; and reduction of toxic Cr(VI) to nontoxic Cr(III). Our catalyst could be reused up to four cycles without much compromising with its activity. Furthermore, the material also demonstrated excellent antimicrobial and anti-biofilm activities against a novel multidrug resistant clinical bacterial isolate Cronobactersakazakii strain AMD04. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of PdNPswere found to be 0.06 and 0.12 mM respectively.

Green Nanosynthesis and Functionalization of Gold Nanoparticles as PTP 1B Inhibitors

Nanomedicine has emerged to become a frontier area of research. The interdisciplinary nature of nanoscale research inevitably leads to nanostructure fabrication and functionalization. Herein, we addressed on the potential of high therapeutic indexed Syzygium cumini seed to biofunctionalize gold nanoparticles. The aqueous seed extract of S. cumini acted as a reducing and capping agent in the formation of gold nanoparticles. Biofabricated gold nanoparticles was characterized using UV–vis spectrophotometry, TEM, SEM, EDAX, FTIR and XRD analysis. PTP 1B inhibitory activity of bioinspired gold nanoparticles was assessed using PTP 1B inhibition assay. Newly synthesized gold nanoparticles was found to possess high PTP 1B inhibitory potential. Furthermore, the newly synthesized nanoparticles not shown any genotoxicity during chromosomal studies indicates its high biocompatibility nature.

Synthesis of a rhodium(I) carbonyl complex with a chiral aminodiphosphine ligand and its immobilization onto aminopropyl functionalized silica gel

The reaction of [Rh(CO)2(µ-Cl)]2 with two molar equivalents of a chiral ligand, (R)-N,N-bis(2-diphenylphosphinoethyl)-1-phenylethylamine(PNP*) yield a mono-carbonyl complex, [Rh(CO)Cl(η2-P,P-PNP*)] (1), in which the potentially tridentate PNP* ligand coordinates in a bidentate fashion through P,P bonding. The complex was characterized by elemental analysis, FAB mass, IR, UV-Vis, 1H- and 31P{1H}-NMR spectroscopy. Variable temperature (223–298 K) 31P{1H}-,NMR spectra of 1 showed a mixture of cis and trans isomers in the solution with the trans predominating at room temperature and the cis at lower temperature. Complex 1 was immobilized on silica through axial coordination of amine from 3-aminopropyltriethoxysilane functionalized silica. The immobilized materials were characterized by elemental analysis (N2), FTIR, DTA–TGA, N2-adsorption, XRD, and SEM analysis.

ACTIVITY OF RHODIUM AND PALLADIUM CATALYSTS IMMOBILIZED ON FUNCTIONALIZED SILICA IN THE DECOMPOSITION AND CARBONYLATION OF METHANOL

Results are given for a study of the physicochemical characteristics (specific surface, phase composition, and surface morphology) of a series of silica supports functionalized by amino groups and of rhodium and palladium complexes [Rh(CO)Cl(η2-P,P-PNP*)] and [PdCl2(NH2(CH2)3)2] immobilized on such supports. The catalytic activity of these complexes was tested in a model methanol decomposition reaction as a stage of a combined carbonylation process to give acetic acid in comparison with the liquid-phase carbonylation of methanol in the presence of immobilized rhodium complexes.