Kuppukkannu Ramalingam

Structural and electronic effects of alkyl substituents on the main group dithiocarbamato complexes: crystal and molecular structures of tris(N,N′-iminodiethanoldithiocarbamato)metal(III) complexes (M As, Sb and Bi) and cyclic voltammetric studies on substituted dithiocarbamates

Abstract Various dithiocarbamates of AsIII, SbIII and BiIII with diethyldithiocarbamic acid (dedtc), N-methylaminoethanoldithiocarbamic acid (nmedtc) and N,N′-iminodiethanoldithiocarbamic acid were subjected to cyclic voltammetric reduction studies with a glassy carbon working electrode. One-electron reduction processes occurs around −1.0 V for As and Sb complexes and around −0.5 V for Bi complexes which are completely irreversible. Attachment of the polar ends of the molecule is indicated by the pre- and post-reduction adsorption processes. As the number of −CH2CH2OH groups increases, the peak currents increase. In the case of Bi complexes, the reduction process tends to become reversible. In addition, the larger peak current associated with the third response indicates the possible reduction of Bi(dtc)2(DMF)n. In all the complexes the dtc− ion was lost from M(dtc)3− species, with oxidation around +0.6 V in the reverse scans. The crystal structures of As(deadtc)3 (1), Sb(deadtc)3 (2) and Bi(deadtc)3 (3) were determined by single crystal X-ray analysis. The coordination polyhedron in As(deadtc)3 is a distorted trigonal antiprism, with three strong (2.33–2.35 A) and three weak (2.82–2.86 A) AsS bonds. Sb(deadtc)3 has a coordination polyhedron which can be described as a distorted pentagonal pyramid. One of the SbS bonds is very short (2.46 A) and differences between others are not significant owing to the larger size of antimony compared with arsenic. The stereochemical requirement of the lone pair on Sb has a more pronounced effect in disturbing the neighbouring atoms than that observed in the corresponding As compounds. The binuclear Bi2(deadtc)6 complex is centrosymmetric, two bidentate ligands being bridged in such a way that each sulfur atom is simultaneously bonded to both metal ions. The resulting coordination polyhedron can be described as a distorted square antiprism. The asymmetry in the MS (M  As, Sb, Bi) bonds is a consequence of the stereochemical requirement for the ligand and the lone pair of electrons on the metals. This is supported by the valence bond sums (VBS) calculated for the complexes.

Mixed ligand complexes involving aminoacid dithiocarbamates, substituted phosphines and nickel(II)

Mixed ligand complexes involving four aminoacid dithiocarbamates (RR′dtc = glydtc− (R = H; R′ = H), methdtc− (R = H; R′ = C3H7S), sardtc− (R = Me; R′ = H), trydtc− (R = H; R′ = C9H8N), substituted phosphines [PPh3, Ph2PCH2CH2PPh2(dppe)] and nickel(II) are reported. All are diamagnetic. Thermal analyses of the complexes are in keeping with the proposed formulae. Thermal decomposition of the dithiocarbamate moiety proceeds through the formation of Ni(SCN)2. PPh3 and dppe are lost in the initial decomposition stages.

Synthesis, spectral and cyclic voltammetric studies on (4,4′-bipyridyl)bis(di(2-hydroxyethyl)dithiocarbamato)zinc(II) and (4,4′-bipyridyl)bis(bis(N-methyl, N-ethanoldithiocarbamato)zinc(II) and their X-ray crystal structures

Abstract Synthesis, spectral and cyclic voltammetric characterization of [Zn2(deadtc)4(4,4′-bipy)] (1) (deadtc=di(2-hydroxyethyl)dithiocarbamate anion) and [Zn2(nmedtc)4(4,4′-bipy)] (2) (nmedtc=N-methyl, N-ethanoldithiocarbamate anion) are reported. The single crystal X-ray structures of the adducts have also been determined. IR spectra of complexes 1 and 2 show the thioureide ν(CN) bands at 1480 and 1489 cm−1, respectively which are lower than the values observed for the parent dithiocarbamates. A reduction in the thioureide stretching frequency is due to the increase in coordination around the zinc ion and the resultant increase in electron density. The charge transfer transitions are observed in the region 260–320 nm. The X-ray crystal structures show that the two adducts are dimeric in nature. The zinc ions are five coordinated with the ZnS4N coordination environment in both complexes. Both adducts have two short ZnS bonds which are close to those observed in the respective parent dithiocarbamate. The asymmetry introduced in ZnS bond lengths in both adducts is due to the coordination of nitrogen from the 4,4′-bipyridine moiety. The ZnN distances are 2.072(4) and 2.054(8) A for compounds 1 and 2, respectively. In complex 1, two sets of thioureide CN distances are observed; one set averages to 1.328(5) A and the other which is longer, averages to 1.346(6) A. In complex 2 the thioureide CN distance (mean of C(6)N(7) and C(12)N(13)) is 1.339(48) A) indicates the partial double bond nature. However, a longer CN distance (C(6)N(7)′:1.374(75) A) is also observed due to the disorder associated with the aliphatic chain of the ethanolic group on dithiocarbamate. All the CS distances are symmetric in both complexes. Two of the CS distances, namely S(3)C(6) (1.702(5) A) in complex 1 and S(2)C(6) (1.706(11) A) in 2, are different. The cyclic voltammetric studies show clearly the presence of excess electron density on the zinc ions in both adducts compared to the parent dithiocarbamates.

X-ray photoelectron spectral study of the planar NiS4, NiS2PCl and NiS2P2 chromophores and X-ray crystal structure of piperidinedithiocarbamatobis(triphenylphosphine) nickel(II) perchlorate triphenylphosphine monohydrate

Abstract An X-ray photoelectron spectral study on the complexes bis(diethyldithiocarbamato) nickel(II), Ni(dedtc) 2 ( 1 ), bis(diethanoldithiocarbamato) nickel(II), Ni(deadtc) 2 ( 2 ), chlorodiethyldithiocarbamatotriphenylphosphine nickel(II), Ni(dedtc)Cl (PPh 3 ) ( 3 ) and diethyldithiocarbamatobis(triphenylphosphine) nickel(II) perchlorate, [Ni(dedtc)(PPh 3 ) 2 ]ClO 4 ( 4 ) with NiS 4 , NiS 4 (electron-withdrawing alkyl substituent) NiS 2 PCl and NiS 2 P 2 chromophores, respectively was made. All the chromophores except NiS 2 P 2 showed similarity in binding energy values with respect to various core level electrons. The nickel 2p 3 2 binding energy value for the NiS 2 P 2 chromophore was significantly different (854.1 eV), indicating an excessive positive charge on the nickel ion. This observation is in line with solution studies by cyclic voltammetry. A one-electron reduction potential was observed to be the minimum for the NiS 2 P 2 chromophore compared to the others. Alkyl substitution does not alter the binding energy values of the nickel 2p 3 2 level as observed earlier. Highly significant negative ΔE values for sulfur 2 p electron binding energies indicate the localization of electronic charge on sulfur. Also, the crystal structure of the complex [Ni(pipdtc)(PPh 3 ) 2 ]ClO 4 (PPh 3 ) ∗d H 2 O (pipdtc = piperidine dithiocarbamate) prepared by the reaction between Ni(pipdtc) 2 and PPh 3 in CH 2 Cl 2 CH 3 OH was determined.

Synthesis and single-crystal structure determination of bis(triphenylphosphine) (diisopropyldithiocarbamato)nickel(II) perchlorate chloroform solvate and [1,2-bis(diphenylphosphino-k.P,P′)ethane] (diisopropyldithiocarbamato)nickel(II) perchlorate chloroform solvate: Steric effect of bulky alkyl substituents on the dithiocarbamate, free and chelating phosphines on the NiS2P2 chromophore

Abstract The complexes [Ni(dipdtc)(PPh 3 ) 2 ]ClO 4 ∗d CHCl 3 ( 1 ) [Ni(dipdtc)dppe]ClO 4 ∗d CHCl 3 ( 2 ) (dipdtc = diisopropyldithiocarbamate, dppe = 1,2-bis(diphenylphosphino)ethane) have been prepared from the reaction between Ni(dipdtc) 2 ( 3 ) and phosphines (PPh 3 and dppe) in CHCl 3 CH 3 OH. The crystal structures of 1 and 2 have been determined, showing that both complexes have planar NiS 2 P 2 chromophores. Increased bulkiness of the alkyl substituent on the dithiocarbamate increases the span volume of the molecule and forces the lengthening of the CN distance due to its puckering. Chelating dppe in complex 2 forces a lower PNiP angle and increased SNiS angle compared to complex 1 .

Spectral, BVS, and Thermal Studies on Bisdithiocarbamates of Divalent Zn, Cd, and Their Adducts: Single Crystal X-Ray Structure Redetermination of (Diiodo) (Tetraethylthiuramdisulfide)mercury(II), [Hg(tetds)I2]

The current article describes the TG and DT analyses of divalent Zn, Cd, and Hg dithiocarbamato (dtc) complexes and their adducts (dchdtc = N,N-dicyclohexyldithiocarbamate anion, 4-mpzdtc = 4-methylpiperazinecarbodithioato anion, padtc = N,N′-(iminodiethylene)bisphthalimidedithiocarbamate anion, pipdtc = piperidinecarbodithioate anion, 1,10-phen = 1,10-phenanthroline, and 2,2′-bipy = 2,2′-bipyridine) along with the structural reinvestigation of [Hg(tetds)I 2 ], where tetds = tetraethylthiuramdisulfide. In the case of Zn(II) and Cd(II) dithiocarbamates and their nitrogenous adducts, thermal decomposition of the nitrogenous bases is followed by the decay of dithiocarbamate leading to the formation of ZnS or CdS as residue. The interaction of iodine with [Hg(dedtc) 2 ] in CHCl 3 results in the oxidation of diethyldithiocarbamate leading to the formation of [Hg(tetds)I 2 ], and the structure was redetermined because the earlier determination was by a Polaroid crystallographic technique with a higher R value. The S-Hg-I bond angles [105.09(3); 105.59(3); 109.26(3), and 100.99(3)°] indicate the near tetrahedral environment around the metal ion. 1 H and 13 C NMR spectra of the complex were analyzed. Whether the product formed upon oxidation is a disulfide or an iodo-substituted product, in the present investigation, is clearly decided by the bulkiness of the substituent attached to the nitrogen. Interestingly, the steric influence is a deciding factor only in the case of mercury compounds and the dithiocarbamates involving Zn, Cd forms of the disulfide complexes.

Synthesis and crystal structure of NiII complexes containing the NiS2P2 chromophore

Abstract The nickel(II) complexes [Ni(nmedtc)(PPh3)2]ClO4 (1) and [Ni(nmedtc)dppe]BPh4 · CH2Cl2 (2) [nmedtc = N-methyl,N-ethanoldithiocarbamate, dppe = 1,2-bis(diphenylphosphino)ethane] were prepared and characterized by electronic and IR spectra, and their structures determined by X-ray crystallography. In both complexes the NiS2P2 chromophore is planar and the thioureide CN has double bond character. Hydrogen bond interaction is observed in 1 between the ethanolic group and the perchlorate anion. Electronic and IR spectra confirm the planarity of the chromophores in both complexes and the contribution of the thioureide form in the molecular structure.

Steric and electronic effects of N -coordinated NC − and NCS− on NiS2PN: synthesis, spectral and single crystal X-ray structural studies on N , N ′-di- n -butyldithiocarbamate complexes of nickel(II) with phosphorus and nitrogen donor ligands

Planar nickel(II) complexes involving N,N′-dibutyldithiocarbamate, such as [Ni(bu2dtc)(PPh3)(NC)] (1) and [Ni(bu2dtc)(PPh3)(NCS)] (2) (where bu2dtc = N,N′-dibutyldithiocarbamate anion) have been prepared, characterized by electronic, IR and NMR spectra and their structures determined by single crystal X-ray crystallography. Cyclic voltammetric characterizations of the complexes are also reported. IR spectra of the two complexes indicate the isobidentate coordination (νc-s ≃ 1095 cm−1 without splitting) of the dithiocarbamate moiety. The important stretching mode characteristic of the thioureide bond (νC–N) occurs at higher wave numbers compared to that of the parent dithiocarbamate complex [Ni(bu2dtc)2]. The electronic spectra of 1 and 2 show signature bands at 426 nm and 478 nm, respectively. NMR spectra show large 31P chemical shifts in both compounds and the most important N13CS2 chemical shift appears at 204.86 ppm and 203.23 ppm for 1 and 2, respectively. The CV studies clearly show the presence of reduced electron density on the nickel ions in mixed-ligand complexes 1 and 2 compared to the parent dithiocarbamate. Single crystal X-ray structure studies show that 2 crystallizes as a new triclinic polymorph, whose molecular structure closely resembles that of the previously reported monoclinic form. Both complexes contain a planar NiS2PN chromophore in keeping with the observed diamagnetism. In both complexes the Ni-S distances are significantly different. The thioureide C–N distances of the complexes are shorter than those observed in the parent [Ni(bu2dtc)2]. The two compounds allow comparison of the influence of NCS− in place of NC−.

Environmentally benign, recyclable nano hollandite and metal intercalated nano hollandites for hydrogen sulfide removal

Hollandite, a 2 × 2 tunnel structure, octahedral molecular sieve (OMS-2) with Ba2+ as counter cation was prepared and characterized by PXRD, IR, SEM, EDX, HRTEM, XPS and TG-DTA techniques. HRTEM of the hollandite showed the particles to be nanorods (<20 nm) and the SAED confirmed its crystalline nature. Seven metal intercalated hollandites were prepared by ion exchange process. Metal intercalated hollandites were analyzed by ICP-OES. The metal ion intercalation was in the range of 1.09 to 2.99% by weight. Order of increasing concentrations of divalent metal ions on intercalation is: Co < Zn < Ni < Cu < Cd < Pb. The observed order is an indication of the exchanging ability of the divalent ion with Ba2+ ion of the hollandite in aqueous medium. Thermal analysis of H2S passed hollandite showed the hollandite to be a superior scrubber over birnessite. Maximum scrubbing of H2S (27%) was observed for copper intercalated hollandite and a minimum (22%) for zinc intercalated hollandite. The involvement of copper in scrubbing is important because of the Cu2+⋯SHn, a typical soft–soft interaction. Overall H2S scrubbing ability followed the order: birnessite (18%) < hollandite (20%) < metal ion intercalated hollandite (27%) and the scrubbing efficiency is remarkable for a dry scrubber under laboratory conditions. Hydrogen sulfide scrubbed hollandite showed relatively poor recyclability compared to intercalated material. Intercalated metal ion increases structural integrity, stabilizes the active metal against reduction and increases the scrubbing ability. The scrubber is recyclable by a simple heating process. The scrubber is benign to nature as its a synthetic analogue of naturally occurring marine nodule type of material.

Synthesis, spectral and single crystal structure determination of [1,3-bis(diphenylphosphino-kP,P′)propane(4-morpholinecarbodithioato-S,S′) nickel(II) perchlorate and [1,4-bis(diphenylphosphino-kP,P′)butane (4-morpholinecarbodithioato-S,S′)nickel(II) perchlorate complexes

Abstract [Ni(mdtc)(1,3-dppp)]ClO4 (1), and [Ni(mdtc)(1,4-dppb))ClO4 (2) [(mdtc−=4-morpholinecarbodithioato anion, 1,3-dppp=1,3-bis(diphenylphosphino)propane, 1,4-dppb=1,4-bis(diphenylphosphino)butane)] have been prepared from their parent dithiocarbamate. The planar complexes were characterized by electronic and IR spectra. Single crystal X-ray structures of compounds 1 and 2 were determined. Both the complexes have planar NiS2P2 chromophores in keeping with the observed diamagnetism. In complexes 1 and 2 the NiS and NiP distances are symmetric. The thioureide CN distances of both the complexes show a decreasing trend compared to the CN distance in the parent Ni(mdtc)2. The resulting PNiP angles are higher in both the complexes (96.5(1)° in 1, 101.4(8)° in 2) due to puckering of propane and the butyl alkyl chain associated with 1,3-dppp and 1,4-dpppb.