Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Kolkata-700 032, India E-mail : icac@iacs.res.in Manuscript received 16 June 2014, accepted 19 June 2014 A selection of Rây's main contributions to... more
Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Kolkata-700 032, India E-mail : icac@iacs.res.in Manuscript received 16 June 2014, accepted 19 June 2014 A selection of Rây's main contributions to nitrite chemistry is chronicled in this article which also presents significant supportive findings of later workers, specially those of the structural type that were not accessible during Rây's time. The following activities are scrutinized in some detail: discovery and authentication of mercurous nitrite, synthesis and coordination chemistry of mercuric nitrite with nitrogen-donor (nitrite, ammonia, mono- and di-amines and certain alkaloids like nicotine) and sulfur-donor (thiols) ligands, sublimation and vapor density of ammonium nitrite, synthesis and properties of a large family of alkylammonium nitrites and finally dissociation constant and decomposition kinetics of nitrous acid.
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The redox activity of four oximato-bridged strongly exchange-coupled copper(II) dimers is examined using cyclic voltammetry and coulometry in acetonitrile solution. A well-defined quasi-reversible couple corresponding to the process Cu2... more
The redox activity of four oximato-bridged strongly exchange-coupled copper(II) dimers is examined using cyclic voltammetry and coulometry in acetonitrile solution. A well-defined quasi-reversible couple corresponding to the process Cu2 II + e⇌ CuIICuI is observed in all cases. The couple corresponding to the next stage of reduction CuII CuII + e ⇌Cu2 I is identified in two complexes. TheE 298
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One mol and 0.5 mol of peracid are consumed for oxo transfer to PPh3 and oxidation of metal, respectively, in the reaction of [Ru(PPh3)3Cl2] with m-ClC6H4CO3H. The active oxo-transfer agent is metal-bound peracid. After oxo transfer the... more
One mol and 0.5 mol of peracid are consumed for oxo transfer to PPh3 and oxidation of metal, respectively, in the reaction of [Ru(PPh3)3Cl2] with m-ClC6H4CO3H. The active oxo-transfer agent is metal-bound peracid. After oxo transfer the carboxylate residue remains chelated to the metal centre as shown by an X-ray structure determination of the product [Ru(PPh3)2(m-ClC6H4CO2)Cl2](1). The trans, cis, cis-RuP2O2Cl2 co-ordination sphere has two-fold symmetry. Its e.s.r. and near-i.r. spectra are in agreement with the energy order dxy > dxz′, dyz. The complex undergoes one-electron quasi-reversible reduction but only at low potentials (E298°–0.40 V vs. saturated calomel electrode).
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The reaction of azooximes RC(NOH)NNPh (R = Me HL1, Ph HL2, or C6H4Me-p HL3) with RhCl3·3H2O afforded red trans-cis-cis(tcc)-[RhCl2L(HL)] 1 which was converted into green [NEt3H][tcc-RhCl2L2] 2 upon treatment with Et3N; 2 isomerises to... more
The reaction of azooximes RC(NOH)NNPh (R = Me HL1, Ph HL2, or C6H4Me-p HL3) with RhCl3·3H2O afforded red trans-cis-cis(tcc)-[RhCl2L(HL)] 1 which was converted into green [NEt3H][tcc-RhCl2L2] 2 upon treatment with Et3N; 2 isomerises to pink [NEt3H][cct-RhCl2L2] 3 spontaneously in boiling benzene–toluene. The distorted octahedral co-ordination spheres are of type RhCl2No2Na2 (No = oximato N, Na = azo N) with the relative arrangement of donor atom pairs as stated (e.g.tcc = trans-Cl2-cis-No2-cis-Na2). The crystal structures of tcc-[RhCl2L2(HL2)] 1b, [NEt3H][tcc-RhCl2L22] 2b and [NEt3H][cct-RhCl2L32] 3c were determined. In 1b unsymmetrical hydrogen bonding is present, the O· · ·O distance being 2.515(5) A. Upon deprotonation to 2b the distance increases to 2.833(8) A. In 3c the distance is 4.207(10) A. The NEt3H+ cations in 2b and 3c are associated with oximato oxygen and cis-RhCl2 chloride respectively. The isomerisation of 2b to 3b in hot toluene is characterised by a high enthalpy and entropy of activation.
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Reaction of Na[S2CNEt2] with [Ru(PPh3)3Cl2] afforded cis-[RuL2(PPh3)2](L = S2CNEt2), which upon oxidation by cerium(IV) furnished trans-[RuL2(PPh3)2]+, isolated as its PF6– salt. Both complexes are obtained in nearly quantitative yields.... more
Reaction of Na[S2CNEt2] with [Ru(PPh3)3Cl2] afforded cis-[RuL2(PPh3)2](L = S2CNEt2), which upon oxidation by cerium(IV) furnished trans-[RuL2(PPh3)2]+, isolated as its PF6– salt. Both complexes are obtained in nearly quantitative yields. The trivalent complex displays one-electron paramagnetism and a rhombic frozen-solution EPR spectrum which has been analysed affording axial and rhombic distortion parameters of ≈ 8000 and ≈ 1700 cm–1 respectively. A ligand-field transition within the Kramers doublets is observed at 6450 cm–1, the predicted value being ≈ 7000 cm–1. Variable-temperature (253–303 K) voltammetric studies have revealed that electrode reactions proceed in a stereoretentive fashion [E½(cis), 0.23 and E½(trans), –0.09 V vs. saturated calomel electrode (SCE)] but the species cis-[RuL2(PPh3)2]+ and trans-[RuL2(PPh3)2] are unstable and spontaneously isomerise affording the stable trans-trivalent and cis-bivalent complexes respectively, the equilibrium concentration of the unstable isomers being very small. The rates and activation parameters of these isomerisation reactions presumably proceeding by the twist mechanism (ΔS‡ highly negative) have been determined. The factors controlling geometrical preference of oxidation states viz., metal–phosphorus back-bonding and PPh3⋯ PPh3 steric repulsion are considered in relation to the osmium analogues reported previously.
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Complexes of types [Os(RSCS2)2(PPh3)2]z(cis-OsII, z= 0, 1; cis-OsIII, z=+, 1+; trans-OsII, z= 0, 2; and trans-OsIII, z=+, 2+) have been prepared, but 1+ is observable only in solution. The 2+ salts are paramagnetic (S=½) and display... more
Complexes of types [Os(RSCS2)2(PPh3)2]z(cis-OsII, z= 0, 1; cis-OsIII, z=+, 1+; trans-OsII, z= 0, 2; and trans-OsIII, z=+, 2+) have been prepared, but 1+ is observable only in solution. The 2+ salts are paramagnetic (S=½) and display rhombic EPR spectra which have been analysed; a relatively weak electronic transition observed in NIR region is assigned to excitation from one Kramers doublet to another. Electrochemical and spectral data have been used to characterise the coupled redox and isomerisation processes interlinking 1, 1+, 2 and 2+. Upon oxidation 1 affords 1+ which isomerises to 2+ relatively rapidly. On the other hand, 2+ can be reduced to 2 which slowly but spontaneously isomerises to 1. Rate and equilibrium data are reported. The electronic and steric factors controlling isomer preference [cis for osmium(II) and trans for osmium(III)] are noted. Compared to the present complexes, the ruthenium congeners isomerise more rapidly and more completely.
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The reaction of bis(acetylacetonato)oxovanadium(lv) with a mixture of a tridentate ONO-co-ordinating hydrazone H,L'-H2L4 (general abbreviation H,L; condensates of benzoylhydrazine with benzoylacetone, salicylaldehyde, 2-hydroxy-1... more
The reaction of bis(acetylacetonato)oxovanadium(lv) with a mixture of a tridentate ONO-co-ordinating hydrazone H,L'-H2L4 (general abbreviation H,L; condensates of benzoylhydrazine with benzoylacetone, salicylaldehyde, 2-hydroxy-1 -naphthaldehyde and 2-...
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ABSTRACT The sugars, methyl 4,6-di-O-methyl-α-D-mannopyranoside (H2m) and methyl 5-O-methyl-β-D-ribofuranoside (H2r) have been synthesized. These react smoothly with [VIVO(L)(H2O)] in methanol in air affording the dark coloured vanadates... more
ABSTRACT The sugars, methyl 4,6-di-O-methyl-α-D-mannopyranoside (H2m) and methyl 5-O-methyl-β-D-ribofuranoside (H2r) have been synthesized. These react smoothly with [VIVO(L)(H2O)] in methanol in air affording the dark coloured vanadates [VVO(Hm)(L)] and [VVO(Hr)(L)] in excellent yields (L2– = N-salicylideneglycinate). The crystal structure determination of [VVO(Hm)(L)] revealed five-membered chelation of VO3+ by the alcoholic and alkoxide oxygen atoms of the monoionised carbohydrate. The two atoms lie respectively trans to the oxo oxygen and aldimine nitrogen atoms. The five V–O bonds are unequal and span the range 1.57–2.37 Å. The asymmetric unit of the complex consists of two metrically similar molecules locked in carboxylate–alcohol O· · ·O hydrogen bonding generating a macrocyclic cavity. In solution each ester displays a single 51V resonance near δ –544. The 1H NMR parameters of the alkoxidic and alcoholic CH protons and of OMe protons are consistent with the O,O-chelation mode for both the vanadates.
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The azopyrimidine and azoimidazole ligands (general abbreviations, RL) used in the present work are 2-(p-R-C6H4NN)C4H3N2, RLpm (R=H, Cl) and 2-(p-R-C6H4NN)-1-(Me)C3H2N2, RLim (R=Me, Cl), respectively. The reaction of Re(CO)5Cl with a... more
The azopyrimidine and azoimidazole ligands (general abbreviations, RL) used in the present work are 2-(p-R-C6H4NN)C4H3N2, RLpm (R=H, Cl) and 2-(p-R-C6H4NN)-1-(Me)C3H2N2, RLim (R=Me, Cl), respectively. The reaction of Re(CO)5Cl with a slight excess of RL in boiling benzene has furnished blue–violet complexes of type Re(CO)3Cl(RL) which have been spectrally characterized. In Re(CO)3Cl(HLpm) and Re(CO)3Cl(ClLim) the Re–Nh, Re–Na distances are 2.173(6), 2.136(6)
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Paramagnetic nickel(II) complexes derived from potentially tridentate triazene 1-oxide ligands show pmr contact shifts. The pmr spectra can be assigned unambiguously. When two triazene 1-oxide complexes are mixed together in solution,... more
Paramagnetic nickel(II) complexes derived from potentially tridentate triazene 1-oxide ligands show pmr contact shifts. The pmr spectra can be assigned unambiguously. When two triazene 1-oxide complexes are mixed together in solution, ligand exchange occurs and the mixed complex contributes to solution composition. This is neatly demonstrated by pmr spectra. Using intensity data of pmr signals equilibrium constants for several equilibria are determined. Only when the ligands are very similar are their redistribution statistical. The structures of the mixed-ligand complexes are discussed.
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... Martin, RL and Stewart, IM, Nature 210, p. 522. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (4). Gerlach, DH and Holm, RH, Inorg. Chem. ... Gibson, JF, Ingram, DJE and Sochonland, D., Discuss. Faraday Soc. 26,... more
... Martin, RL and Stewart, IM, Nature 210, p. 522. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (4). Gerlach, DH and Holm, RH, Inorg. Chem. ... Gibson, JF, Ingram, DJE and Sochonland, D., Discuss. Faraday Soc. 26, p. 79. Assour, JM and Kahn, WK, J. Am. ...
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Page 1. Vol. 9, No. 5, May 1970 NICKEL(II) CHELATES 1153 no doubt, reflects the absence of a free acetate gro p in these complexes. An upper limit ca.n be placed on this rate. Since separate peaks separated by -10 ppm are ...
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Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Calcutta 700 032, India ... Reaction of manganese(I1) acetate tetrahydrate withdithiaalkyl-substituted triazene 1-oxides, [RN(O)NNHC&S]2-(CH&... more
Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Calcutta 700 032, India ... Reaction of manganese(I1) acetate tetrahydrate withdithiaalkyl-substituted triazene 1-oxides, [RN(O)NNHC&S]2-(CH& (H2RrL; R = Me, Ph; x = 2,3), have afforded ...
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ABSTRACT The aerial reaction of 2,2'-dihydroxyazobenzene (H2L) with bis(acetylacetonato)oxovanadium(IV) in methanol affords binuclear VV2O3L2. In the presence of KOH, KVVO2L.1.5H2O is isolated. Dilute acids convert VO2L- to V2O3L2... more
ABSTRACT The aerial reaction of 2,2'-dihydroxyazobenzene (H2L) with bis(acetylacetonato)oxovanadium(IV) in methanol affords binuclear VV2O3L2. In the presence of KOH, KVVO2L.1.5H2O is isolated. Dilute acids convert VO2L- to V2O3L2 via V(V)O(OH)L. The electronic and IR spectra of the complexes are described. In crystalline KVO2L.1.5H2O, the vanadium(V) atom has square pyramidal geometry. The base is formed by coordinated ONO atoms of L2- and an oxo oxygen atom. The metal atom is displaced by approximately 0.5 angstrom from the base toward the apical oxo oxygen atom. The O-V-O angle is > 107-degrees, which is a characteristic feature of VO2+ complexes with pentacoordinated vanadium. The VO2L- units are interlinked into an infinite network by K+ ions (bonded to water, oxo, and phenolic oxygen atoms). In crystalline V2O3L2, two VOL fragments are bridged by an oxygen atom lying on a 2-fold axis. The geometry of the pentacoordinated metal atom is similar to that in VO2L-, the bridging oxygen atom defining the shared comer of the bases of the two metal pyramids. The two terminal oxygen atoms are trans-directed lying on opposite sides of the VOV plane. The V-O(phenolic) length in V2O3L2 is shorter than that in KVO2L.1.5H2O by approximately 0.1 angstrom due to stronger metal-phenol pi-bonding in the former complex. Crystal data for KVO2L.1.5H2O: monoclinic; space group C2/c; a = 33.834(9) angstrom, b = 7.245(2) angstrom, c = 23.708(4) angstrom; beta = 103.56(2)degrees; V = 5649(2) angstrom3; Z = 16; R = 3.64%; R(w) = 4.07%. Crystal data for V2O3L2: orthorhombic; space group Pcnb; a = 7.392(2) angstrom, b = 12.868(2) angstrom, c = 24.371(7) angstrom; V = 2318(1) angstrom3; Z = 4; R = 3.84%, R(w) = 4.38%. In dichloromethane solution this complex displays a one-electron couple, V2O3L2-V2O3L2-, having an E1/2 value of 0.30 V vs SCE. The electrogenerated mixed-valence (V(V)(IV)) complex V2O3L2- shows intervalence bands at 760 and 980 run. At room temperature its solution (1.77 mu(B)) EPR spectrum consists of 15 lines (A = 49.9 G; g = 1.98) corresponding to the delocalization of the unpaired electron over the two equivalent metal atoms. In frozen glass (77 K) the electron is localized at one center (A(parallel-to) = 174.3 G, A(perpendicular-to) = 64.2 G; g(parallel-to) = 1.96; g(perpendicular-to) = 1.98). From variable-temperature EPR spectra the activation energy and rate constant (298 K) for the delocalization process are estimated to be 3.1 kcal mol-1 and 3.2 X 10(10) s-1, respectively.
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... The method of synthesis is stated in Scheme I. Ligand 1 is related to the oxime-imine-amine ligand 2 (ab-( I ) Ray, D.; Pal, S.; Chakravorty, A. Inorg. Chem. ... 1982, 21,4296-4300. (b) Martone, DP;Osvath, P.; Eigenbrot, C.;... more
... The method of synthesis is stated in Scheme I. Ligand 1 is related to the oxime-imine-amine ligand 2 (ab-( I ) Ray, D.; Pal, S.; Chakravorty, A. Inorg. Chem. ... 1982, 21,4296-4300. (b) Martone, DP;Osvath, P.; Eigenbrot, C.; Laran-jeira. MCM; Peacock, RD; Lappin, A. G. Inorg. ...
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Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Calcutta 700 032, India ... In the title families the ON 0 ligands are deprotonated forms of N-(2-hydroxyphenyl)salicylaldimine (H2amp),... more
Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Calcutta 700 032, India ... In the title families the ON 0 ligands are deprotonated forms of N-(2-hydroxyphenyl)salicylaldimine (H2amp), 2,2'-dihydroxyazobenzene (Hzazp), N-(2-...
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... Bis( arylazo-oximato) pal ladium( 11) ; Synthesis, Pal lad ium-N itrogen Bond Lability, and Redox Activity By Pinaki Bandyopadhyay, Pradip K. Mascharak, and Animesh Chakravorty,' Department of Inorganic Chemistry, Indian... more
... Bis( arylazo-oximato) pal ladium( 11) ; Synthesis, Pal lad ium-N itrogen Bond Lability, and Redox Activity By Pinaki Bandyopadhyay, Pradip K. Mascharak, and Animesh Chakravorty,' Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Calcutta ...
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The reaction of Schiff mono-bases, HRL (R = Me, Et), of 2,6-diformyl-4-methylphenol with K2[RuCl5(H2O)] has afforded has afforded Ru”‘(RL)2(PPh3)CI. The X-ray structure of the R = Et complex has revealed metalchelation at the... more
The reaction of Schiff mono-bases, HRL (R = Me, Et), of 2,6-diformyl-4-methylphenol with K2[RuCl5(H2O)] has afforded has afforded Ru”‘(RL)2(PPh3)CI. The X-ray structure of the R = Et complex has revealed metalchelation at the salicylaldimine segment of RL-, the two phenolic oxygen and azomethine nitrogen atoms lying in mutually trans and cis positions, respectively. The trivalent state of the metal is stabilized in Ru(RL),(PPh,) Cl, the ruthenium(III)/ruthenium(II) E,,, being -0.40 V US SCE. These distorted low-spin (t:) complexes display rhombic EPR spectra and are characterized by a pair of ligand field transitions (in the near-IR region) within the split t2 shell. The complexes provide a striking contrast with the ruthenium(I1) organometallics arising from the reaction of HRL with Ru”(PPh3)2Cl2.
ABSTRACT The reaction of [VIVO(L)(H2O)] with ethane-1,2-diol (H2ed) in methanol in air afforded complexes of type [VVO(L)(Hed)] in very good yields (H2L1=N-salicylideneglycine, H2L2=N-salicylidene-L-phenylalanine). The crystal structure... more
ABSTRACT The reaction of [VIVO(L)(H2O)] with ethane-1,2-diol (H2ed) in methanol in air afforded complexes of type [VVO(L)(Hed)] in very good yields (H2L1=N-salicylideneglycine, H2L2=N-salicylidene-L-phenylalanine). The crystal structure of [VO(L2)(Hed)] has revealed the presence of tridentate [L2]2– and bidentate Hed–. In the latter the alcoholic oxygen lies trans to the oxo atom. In the VO5N co-ordination sphere the five vanadium–oxygen lengths follow the order: oxo < alkoxidic < phenoxidic < carboxylic < alcoholic. The absolute configuration of the complex is CS. The lattice consists of hydrogen-bonded (between alcoholic and carboxylic oxygen atoms) dimers having two-fold symmetry. The CD spectrum of [VO(L2)(Hed)] has revealed the composite nature of the O(alkoxide)→ V charge-transfer band in the visible region. In the 1H NMR spectra of the complexes the four methylene protons of co-ordinated Hed– are inequivalent. The [VVO(L)(Hed)] complexes represent authentic examples of the very rare mononuclear oxovanadium species incorporating ethane-1,2-diol as a ligand.
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... 10 Q. Chen and J. Zubieta, Coord. Chem. Rev., 1992, 114, 107; IM Khan, Q. Chen, DP Goshorn, H. Hope, S. Parkin and J. Zubieta, J. Am. Chem. ... Soc. Jpn., 1979, 52, 452. 24 SP Rath, KK Rajak, S. Mondal and A. Chakravorty, unpublished... more
... 10 Q. Chen and J. Zubieta, Coord. Chem. Rev., 1992, 114, 107; IM Khan, Q. Chen, DP Goshorn, H. Hope, S. Parkin and J. Zubieta, J. Am. Chem. ... Soc. Jpn., 1979, 52, 452. 24 SP Rath, KK Rajak, S. Mondal and A. Chakravorty, unpublished work. 25 L. Sacconi, Z. Anorg. Allg. ...
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91 Journal of Organometafc Chemistry, 439 (1992) 9199 Elsevier Sequoia SA, Lausanne JOM 22834 Synthesis and structure of a thioazobenzene palladacycle: oxygen insertion into the PdC bond by mchloroperbenzoic acid Chandan Kumar Pal,... more
91 Journal of Organometafc Chemistry, 439 (1992) 9199 Elsevier Sequoia SA, Lausanne JOM 22834 Synthesis and structure of a thioazobenzene palladacycle: oxygen insertion into the PdC bond by mchloroperbenzoic acid Chandan Kumar Pal, Surajit Chattopadhyay, ...