Ditolyldithiophosphato derivatives of phosphorus(III) and phosphorus(V)

O,O′-Ditolylphosphorodithioates of phosphorus(III), [(o-, m-, or p-CH₃C₆H₄O)₂PS₂] _n PCl_3−n , and phosphorus(V), [(o-, m-, or p-CH₃C₆H₄O)₂-PS₂] _n POCl_3−n , (n = 1, 2, and 3) were isolated as colorless viscous liquids by the reaction of PCl₃ and POCl₃ with sodium ditolylphosphorodithioate, (o-, m-, or p-CH₃C₆H₄O)₂PS₂Na, in 1:1, 1:2, and 1:3 molar ratios in toluene. These compounds were characterized by elemental analyses, molecular weight measurements, IR, and NMR (¹H, ³¹P, and ¹³C) spectroscopic studies, which indicated a less common monodentate linkage of dithiophosphate moieties in both phosphorus(III) and phosphorus(V) derivatives leading to a tetrahedral geometry around the phosphorus atom.     

Ditolyldithiophosphato derivatives of phosphorus(III) and phosphorus(V)

O,O′-Ditolylphosphorodithioates of phosphorus(III), [(o-, m-, or p-CH₃C₆H₄O)₂PS₂] _n PCl_3−n , and phosphorus(V), [(o-, m-, or p-CH₃C₆H₄O)₂-PS₂] _n POCl_3−n , (n = 1, 2, and 3) were isolated as colorless viscous liquids by the reaction of PCl₃ and POCl₃ with sodium ditolylphosphorodithioate, (o-, m-, or p-CH₃C₆H₄O)₂PS₂Na, in 1:1, 1:2, and 1:3 molar ratios in toluene. These compounds were characterized by elemental analyses, molecular weight measurements, IR, and NMR (¹H, ³¹P, and ¹³C) spectroscopic studies, which indicated a less common monodentate linkage of dithiophosphate moieties in both phosphorus(III) and phosphorus(V) derivatives leading to a tetrahedral geometry around the phosphorus atom. Correspondence: Sushil K. Pandey, Department of Chemistry, University of Jammu, Baba Saheb Ambedkar Road, Jammu 180 006 (J & K), India.     

Reactivity of diacetylplatinum(II) complexes: oxidative addition of alkyl halides and crystal structures of acetyl platinum(IV) complexes

Diacetylplatinum(II) complexes [Pt(COMe)₂(N^N)] (N^N = bpy, 3a; 4,4′-t-Bu₂-bpy, 3b) were found to undergo oxidative addition reactions with organyl halides. The reaction of 3a with methyl iodide and propargyl bromide led to the formation of the cis addition products (OC-6-34)-[Pt(COMe)₂(R)X(bpy)] (R = Me, X = I, 4a; CH₂C≡CH, X = Br, 4k). Analogous reactions of 3a with ethyl iodide, benzyl bromide, and substituted benzyl bromides, 3-(bromomethyl)pyridine, 2-(bromomethyl)thiophene, allyl bromide, and cyclohex-2-enyl bromide led to exclusive formation of the trans addition products (OC-6-43)-[Pt(COMe)₂(R)X(bpy)] (X = I, R = Et, 4b; X = Br, R = CH₂C₆H₅, 4c; CH₂C₆H₄(o-Br), 4d; CH₂C₆H₄(p-COOH), 4e; CH₂-3-py (3-pyridylmethyl), 4f; CH₂-2-tp (2-thiophenylmethyl), 4g; CH₂CH=CH₂, 4h; c-hex-2-enyl (cyclohex-2-enyl), 4i). All complexes 4 were characterized by microanalysis, ¹H and ¹³C NMR and IR spectroscopy. Additionally, complexes 4a, 4f, and 4g were characterized by single-crystal X-ray diffraction analyses. Reactions of 3a and 3b with o-, m- and p-bis(bromomethyl)benzene, respectively, led to the formation of dinuclear platinum(IV) complexes [{Pt(COMe)₂Br(N^N)}₂-{μ-(CH₂)₂C₆H₄}] (5). These complexes were characterized by microanalysis, IR spectroscopy, and depending on their solubility by ¹H and ¹³C NMR spectroscopy, too. A single-crystal X-ray diffraction analysis of complex [{Pt(COMe)₂Br(bpy)}₂{μ-m-(CH₂)₂C₆H₄}] (5b) confirmed its dinuclear composition. The solid-state structures of 4a, 4f, 4g, and 5b are discussed in terms of C–H···O and O–H···O hydrogen bonds as well as π–π stacking between aromatic rings.     

Theoretical Study of the Structures,Properties and Spectroscopies on Fullerene Hydrides C<Subscript>26</Subscript>H<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> (<Emphasis Type="Italic">n</Emphasis> = 2, 4, 6, 8)

The structures, stability patterns of C₂₆H _n (n = 2) formed from the initial D _3h C₂₆ fullerene were investigated by use of second-order-Moller–Plesset perturbation theory. The study of the stability patterns of hydrogenation reaction on C₂₆ cage revealed that type (β) carbons were the active site and the analyses of π-orbital axis vector indicated that the reactivity of C₂₆ was the result of the high strain and the hydrogenation reaction on C₂₆ cage was highly exothermic. The calculated ¹³C NMR spectra of C₂₆H _n (n = 2) predicted that the two sp ³ hybridization carbons in C₂₆H _n (n = 2) obviously moved to high field compare with that in D _3h C₂₆. Hence, the C₂₆H₂ should be obtained and detected experimentally. Similarly, the structures and reaction energies of C₂₆H _n (n = 4, 6, 8) were further studied at HF/6-31G*, B3LPY/6-31G* and MP2/6-31G* level. The results suggested the hydrogenation products of C₂₆, C₂₆H _n (n = 4, 6, 8), were more stable than the C₂₆ cage.     

Synthesis and Anticancer Activity of Long-Chain Isonicotinic Ester Ligand-Containing Arene Ruthenium Complexes and Nanoparticles

Arene ruthenium complexes containing long-chain N-ligands L¹ = NC₅H₄–4-COO–C₆H₄–4-O–(CH₂)₉–CH₃ or L² = NC₅H₄–4-COO–(CH₂)₁₀–O–C₆H₄–4-COO–C₆H₄–4-C₆H₄–4-CN derived from isonicotinic acid, of the type [(arene)Ru(L)Cl₂] (arene = C₆H₆, L = L¹: 1; arene = p-MeC₆H₄Pr ⁱ , L = L¹: 2; arene = C₆Me₆, L = L¹: 3; arene = C₆H₆, L = L²: 4; arene = p-MeC₆H₄Pr ⁱ , L = L²: 5; arene = C₆Me₆, L = L²: 6) have been synthesized from the corresponding [(arene)RuCl₂]₂ precursor with the long-chain N-ligand L in dichloromethane. Ruthenium nanoparticles stabilized by L¹ have been prepared by the solvent-free reduction of 1 with hydrogen or by reducing [(arene)Ru(H₂O)₃]SO₄ in ethanol in the presence of L¹ with hydrogen. These complexes and nanoparticles show a high anticancer activity towards human ovarian cell lines, the highest cytotoxicity being obtained for complex 2 (IC₅₀ = 2 μM for A2780 and 7 μM for A2780cisR).     

Different orientations of C=O versus P=O in P(O)NHC(O) skeleton: the first study on an aliphatic diazaphosphorinane with a gauche orientation

Different orientations of P(O) versus C(O) in P(O)NHC(O) skeleton have been discussed in two new phosphorus(V)-nitrogen compounds with formula XP(O)Y and XP(O)Z₂ where X = NHC(O)C₆H₄(4-F) and Y = NHCH₂C(CH₃)₂CH₂NH (1), Z = NHC₆H₄(4-CH₃) (2). Compound 1 is the first example of an aliphatic diazaphosphorinane with a gauche orientation which has been studied by X-ray crystallography; the P=O bond is in the equatorial position of the ring. Both compounds show ⁿ J(F,C) and ^m J(F,H) coupling constants (n = 1, 2, 3 and 4; m = 3 and 4) and ³ J(P,C) > ² J(P,C). Quantum chemical calculations were performed with HF and Density Functional Theory (DFT) methods using 6−31+G(d,p) basis set. A tentative assignment of the observed vibrational bands for these molecules is discussed. Compound 1 shows a deshielded C atom of the carbonyl moiety (in ¹³C NMR spectrum) relative to that of 2, which is supported by IR spectroscopy in which the considerably lower C=O frequency is observed for 1. Comparing the X-ray crystallography and IR spectra of 1 and 2 shows that the acyclic compound 2, containing P=O and C=O bonds in an anti position, are involving in a stronger N–H···O=P hydrogen bond in crystal network. This leads to a weaker P=O and N_C(O)NHP(O)–H bonds and stronger N···O interaction. The N_amide–H is involved in an intramolecular N–H···O hydrogen bond.     

Organische Phosphorverbindungen XXX. Herstellung und Eigenschaften aromatisch substituierter Cyclopolyphosphine [1]

The interaction of ClC₆H₄PCl₂ or o-CH₃C₆H₄PCl₂ with the corresponding primary phosphines has been studied under a variety of conditions.     

Formal chromium–chromium triple bonds and bent rings in the binuclear cycloheptatrienylchromium carbonyls (C7H7)2Cr2(CO)n (n = 6, 5, 4, 3, 2, 1, 0): A density functional theory study

Binuclear cycloheptatrienylchromium carbonyls of the type (C₇H₇)₂Cr₂(CO)_n (n = 6, 5, 4, 3, 2, 1, 0) have been investigated by density functional theory. Energetically competitive structures with fully bonded heptahapto η⁷-C₇H₇ rings are not found for (C₇H₇)₂Cr₂(CO)_n structures having two or more carbonyl groups. This result stands in contrast to the related (C_nH_n)₂M₂(CO)_n (M = Mn, n = 6; M = Fe, n = 5; M = Co, n = 4) systems. Most of the predicted (C₇H₇)₂Cr₂(CO)_n structures have bent trihapto or pentahapto C₇H₇ rings and CrCr distances in the range 2.4–2.5 Å suggesting formal triple bonds. In some cases rearrangement of the heptagonal C₇H₇ ring to a tridentate cyclopropyldivinyl or tridentate bis(carbene)alkyl ligand is observed. In addition structures with CO insertion into the C₇H₇–Cr bond are predicted for (C₇H₇)₂Cr₂(CO)_n (n = 6, 4, 2). The global minima found for the (C₇H₇)₂Cr₂(CO)_n derivatives for n = 6, 5, and 4 are (η⁵-C₇H₇)(OC)₂CrCr(CO)₄(η¹-C₇H₇), (η³-C₇H₇)(OC)₂CrCr(CO)₃(η^2,1- C₇H₇), and (η⁵-C₇H₇)₂Cr₂(CO)₄, respectively. The global minima for (C₇H₇)₂Cr₂(CO)_n (n = 3, 2) have rearranged C₇H₇ groups. Singlet and triplet structures with heptahapto η⁷-C₇H₇ rings are found for the dimetallocenes (η⁷-C₇H₇)₂Cr₂(CO) and (η⁷-C₇H₇)₂Cr₂, with the singlet structures being of much lower energies in both cases.     

Triruthenium carbonyl complexes containing bidentate pyridine–alkoxide ligands for highly efficient oxidation of primary and secondary alcohols

Reactions of substituted pyridylalkanol 6-CH₃PyCH₂CH(OH)R (R = Ph (L¹H), R = 4-CH₃C₆H₄ (L²H), R = 4-OCH₃C₆H₄ (L³H), R = 4-ClC₆H₄ (L⁴H), R = 4-BrC₆H₄ (L⁵H), R = 4-CF₃C₆H₄ (L⁶H)) with Ru₃(CO)₁₂ in refluxing tetrahydrofuran afforded the corresponding ruthenium carbonyl complexes [6-CH₃PyCH₂CHRO]₂Ru₃(CO)₈ (R = Ph ( 1a ), R = 4-CH₃C₆H₄ ( 1b ), R = 4-OCH₃C₆H₄ ( 1c ), R = 4-ClC₆H₄ ( 1d ), R = 4-BrC₆H₄ ( 1e ), R = 4-CF₃C₆H₄ ( 1f )) in good yields. These ruthenium complexes were well characterized using elemental analysis and Fourier transform infrared and NMR spectroscopies. Furthermore, their crystal structures were determined using single-crystal X-ray diffraction analysis. Complexes 1a – 1f were found to be highly active toward oxidation of a wide range of primary and secondary alcohols to corresponding aldehydes and ketones within 5 minutes in the presence of N-methylmorpholine-N-oxide as oxidant.     

(Imido)vanadium Complexes as Efficient Catalyst Precursors for Olefin Polymerization/Oligomerization

(Arylimido)vanadium(V) complexes containing anionic ancillary donor ligands of type, V(NAr)Cl₂(L) (Ar = 2,6-Me₂C₆H₃, L = aryloxo, ketimide phenoxyimine, etc.) exhibited high catalytic activities for ethylene polymerization in the presence of Al cocatalyst; V(NAr)Cl₂(O-2,6-Me₂C₆H₃) showed the exceptionally high activities in the presence of halogenated Al alkyls such as Et₂AlCl, EtAlCl₂, etc. (Arylimido)vanadium(V)-alkylidene complexes, V(CHSiMe₃)(NAr)(L′) (L′ = N=C ^t Bu₂, O-2,6- ⁱ Pr₂C₆H₃) exhibited the remarkable catalytic activities for ring-opening metathesis polymerization of norbornene. (Imido)vanadium(V) complexes containing the (2-anilidomethyl)pyridine ligand, V(NR)Cl₂[2-Ar′NCH₂(C₅H₄N)] (R = 1-adamantyl, cyclohexyl, phenyl, Ar′ = 2,6-Me₂C₆H₃, 2,6- ⁱ Pr₂C₆H₃), exhibit the remarkable activities for ethylene dimerization in the presence of MAO, affording 1-butene exclusively (selectivity 90.4 to >99%). The steric bulk of the imido ligand plays an important role in the selectivity, and the electronic nature directly affects the activity.     

Reactions of nucleophiles with cyclopentadienyliron complexed halotoluenes

η⁶-o-Chlorotoluene-η⁵-cyclopentadienyliron hexafluorophosphate undergoes nucleophilic substitution of the chlorine atom with anions generated (K₂CO₃/DMF) from methyl thioglycolate, diethyl malonate, dimethyl malonate, methyl acetoacetate and 2,4-pentanedione. The compounds prepared were o-CH₃C₆H₄SCH₂CO₂CH₃FeCp⁺PF₆⁻, o-CH₃C₆H₄CH(CO₂C₂H₅)₂FeCp⁺PF₆⁻, o-CH₃C₆H₄CH(CO₂CH₃)₂FeCp⁺PF₆⁻, o-CH₃C₆H₄CH(COCH₃)CO₂CH₃FeCp⁺PF₆⁻ and o-CH₃C₆H₄CH₂COCH₃FeCp⁺PF₆ . Similarly, the reaction of diethyl malonate, dimethyl malonate, methyl acetoacetate anions and methylamine with η⁶-2,6-dichlorotoluene-η⁵-cyclopentadienyliron hexafluorophosphate yielded monosubstitution of one of the chloro groups. The complexes prepared in this study were η⁶-diethyl(3-chloro-2-methyl) phenylmalonate- η⁵-cyclopentadienyliron hexafluorophosphate, η⁶-dimethyl(3-chloro-2-methyl)phenylmalonate-η⁵-cyclopentadienyliron hexafluorophosphate, η⁶-methyl(3-chloro-2-methyl)phenylacetoacetate-η⁵-cyclopentadienyliron hexafluorophosphate and η⁶-3-chloro(2-methyl-N-methyl)aniline-η⁵-cyclopentadienyliron hexafluorophosphate. Reaction of η⁶-2,6-dichlorotoluene-η⁵-cyclopentadienyliron hexafluorophosphate with excess methanol as well as methyl thioglycolate in the presence of K₂CO₃ resulted in disubstitution of both chloro groups to yield new complexes, η⁶-2,6-dimethoxytoluene-η⁵-cyclopentadienyliron hexafluorophosphate and η⁶-methyl[(2-methylphenyl)1,3-dithio] diacetate-η⁵5-cyclopentadienyliron hexafluorophosphate, respectively. Complexes o-CH₃C₆H₄CH(CO₂C₂H₅)₂FeCp⁺PF₆⁻, o-CH₃C₆H₄CH(CO₂CH₃)₂FeCp⁺PF₆⁻ and o-CH₃C₆H₄CH₂ COCH₃FeCp⁺ PF₆⁻ react with excess K₂CO₃ and benzyl bromide in refluxing methylene chloride to give 80–90% yields of complexes o-CH₃C₆H₄C(CH₂C₆H₅)(CO₂C₂H₅)₂FeCp⁺PF₆⁻, o-CH₃C₆H₄C(CH₂C₆H₅)(CO₂CH₃)₂FeCp⁺PF₆⁻ and o-CH₃C₆H₄CH(CH₂C₆H₅)COCH₃FeCp⁺PF₆⁻, respectively. Reaction of complex, o-CH₃C₆H₄C(CH₂C₆H₅)(CO₂C₂H₅)₂FeCp⁺PF₆⁻ with one molar equivalent of t-BuOK followed by acidic work-up gives o-(C₂H₅CO₂CH₂)C₆H₄CH(CO₂C₂H₅)CH₂C₆H₅FeCp⁺PF₆⁻. Similarly, reactions of complexes o-CH₃C₆H₄C(CH₂C₆H₅)(CO₂C₂H₅)₂FeCp⁺PF₆⁻ and o-CH₃C₆H₄C(CH₂C₆H₅)(CO₂CH₃)₂FeCp⁺PF₆⁻ with t-BuOK in THF followed by alkylation with methyl iodide gave the new complexes, o-(C₂H₅O₂C(CH₃)CH)C₆H₄CH(CH₂C₆H₅)CO₂C₂H₅FeCp⁺PF₆⁻ and o-(CH₃O₂C(CH₃)CH)C₆H₄CH(CH₂C₆H₅)CO₂CH₃FeCp⁺PF₆⁻, respectively. Vacuum sublimation of the new complexes, o-CH₃C₆H₄C(CH₂C₆H₅)(CO₂C₂H₅)₂FeCp⁺PF₆⁻ and o-(C₂H₅O₂CCH₂)C₆H₄CH(CH₂C₆H₅)CO₂C₂H₅FeCp⁺PF₆⁻ gives o-CH₃C₆H₄C(CH₂C₆H₅)(CO₂C₂H₅)₂ and O-(C₂H₅O₂CCH₂)C₆H₄CH(CH₂C₆H₅)CO₂C₂H₅, respectively.     

Zinc(II) (o-hydroxybenzaldoximates) Complexes with Mono- and Bidentate Ligands

New complexes:Zn(Hsalox)(ox), Zn(Hsalox)(NHPh), Zn(Hsalox)(Hsal) and Zn(Hsalox)₂(1,2-diMeim) have been synthesised as a result of a reaction of Zn(salox) and Zn(Hsalox)₂ (where: salox ^2–=OC₆H₄CHNO^2–, Hsalox ^–=OC₆H₄CHNOH^–) with 8-hydroxyquinoline (Hox), o-aminophenol (NH₂Ph), o-hydroxybenzoic acid (H₂Sal) and 1,2-dimethylimidazole (1,2-diMeim). Chemical, X-ray and thermal analyses of the complexes and their sinters have been carried out. Thermal decomposition pathways have been postulated for the complexes. The mixtures about not definite composition have been obtained as a result of a reaction of zinc(o-hydroxybenzaldoximates) with imidazole(Him) and 4-methylimidazole (4-MeHim). This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis and structures of nickel(II) trimethylacetate dimers with coordinated diamines

Thermal decomposition of the tetranuclear nickel(II) complex Ni₄lη²-o-(NH₂)(NHPh)C₆H₄|₂(MeCN)₂(μ-OOCCMe₃)₄(η²-OOCCMe₃)₂ (I) under an inert atmosphere (o-xylene, 140 °C) was investigated. Under these conditions, the asymmetric binuclear complex Ni|η²-o-(NH₂)(NHPh)C₆H₄‖(η¹-o-(NH₂))(NHPh)C₆H₄|(η²,η-O,O-OOCCMe₃)(η²-OOCCMe₃) (2) was formed at the first stage. Complex2 was converted into the symmetric dimer Ni|η¹-o-(NH₂)(NHPh)C₆H₄|(μ-OOCCMe₃)₄ (3) upon recrystallization from benzene. The structures of complexes2 and3 were established by X-ray diffraction analysis. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1915–1918, November, 2000.     

4-Chloro-2-methoxybenzoates of heavy lanthanides(III) and yttrium(III)

4-Chloro-2-methoxybenzoates of heavy lanthanides(III) and yttrium(III) were obtained as mono-, di-, tri-or tetrahydrates with metal to ligand ratio of 1:3 and general formula Ln(C₈H₆ClO₃)₃·nH₂O, where n=1 for Ln=Er, n=2 for Ln=Tb, Dy, Tm, Y, n=3 for Ln=Ho and n=4 for Yb and Lu. The complexes were characterized by elemental analysis, FTIR spectra, TG, DTA and DSC curves, X-ray diffraction and magnetic measurements. The carboxylate group appears to be a symmetrical bidentate chelating ligand. All complexes are polycrystalline compounds. The values of enthalpy, ΔH, of the dehydration process for analysed complexes were also determined. The solubilities of heavy lanthanide(III) 4-chloro-2-methoxybenzoates in water at 293 K are of the order of 10⁻⁴ mol dm⁻³. The magnetic moments were determined over the range of 76–303 K. The results indicate that there is no influence of the ligand field of 4f electrons on lanthanide ions and the metal ligand bonding is mainly electrostatic in nature.     

Phenylimino-phosphorsäure-(diäthylamid)-chloride

Zusammenfassung Monomere Phosphinimine der allgemeinen Formel C₆H₅N= =PCl _n (NEt₂)_3-n (n=0,1,2) lassen sich (I) aus dimerem Phenylimino-phosphorsäure-trichlorid und Diäthylamin in Gegenwart eines Chlorwasserstoffakzeptors und (II) durch Reaktion der Phosphine PCl _n (NEt₂)_3-n mit Phenylazid darstellen. Die Phosphorane Et₂NPCl₄, (Et₂N)₂PCl₃ und (Et₂N)₃PBr₂ reagieren mit Anilin nicht zu Phenylimino-Verbindungen. Durch alkalische Hydrolyse von C₆H₅N=PCl(NEt₂)₂ entsteht das Phosphorsäure-bis[diäthylamino]-anilid. Die IR- und¹H- und³¹P-NMR-Spektren der Verbindungen werden mitgeteilt.

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Monomeric phosphinimines of the general formula C₆H₅N= =PCl _n (NEt₂)_3-n (n=0,1,2) are formed (I) from dimeric phenyliminophosphoricacid-trichloride and diethylamine in the presence of a HCl-acceptor and (II) by reacting the phosphines PCl _n (NEt₂)_3-n with phenylazide. The phosphoranes Et₂NPCl₄, (Et₂N)₂PCl₃ and (Et₂N)₃PBr₂ do not give the corresponding phenylimines with aniline. Alkaline hydrolysis of C₆H₅N= =PCl(NEt₂)₂ gives bis[diethylamino]-anilido-phosphinoxid. IR-,¹H- and³¹P-NMR-spectra are given.

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Mit 1 Abbildung     

Ruthenium-mediated Selective Aromatic Thiolation in the Complex [RuII{o-S—C6H4-(p-R-)—N=N—C3H2NN(1)—R′}2]. Synthesis, Spectroscopic, e.p.r., Electro-chemical Characterization and Spectro-electrochemical Correlation

The reaction of ctc-[Ru(RaaiR′)₂Cl₂] (3a–3i) [RaaiR′=1-alkyl-2-(arylazo)imidazole, p-R—C₆H₄—N=N— C₃H₂NN(1)—R′, R=H, OMe, NO₂, R′=Me, Et, Bz] with KS₂COR′′ (R′′=Me, Et, Pr, Bu or CH₂Ph) in boiling dimethylformamide afforded [Ru^II{o-S—C₆H₄(p-R-)—N=N—C₃H₂NN(1)—R′}₂] (4a–4i), where the ortho-carbon atom of the pendant phenyl ring of both ligands has been selectively and directedly thiolated. The newly formed tridentate thiolate ligands are bound in a meridional fashion. The solution electronic spectra exhibit a strong MLCT band near 700 nm and near 550 nm, respectively in DCM. The molecular geometry of the complexes in solution has been determined by H n.m.r. spectroscopy. Cyclic voltammograms show a Ru(II)/Ru(III) couple near 0.4 V and an irreversible oxidation response near 1.0 V due to oxidation of the coordinated thiol group, along with two successive reversible ligand reductions in the range −0.80–0.87 V (one electron), −1.38–1.42 V (one electron). Coulometric oxidation of the complexes at 0.6 V versus SCE in CH₂Cl₂ produced an unstable Ru(III) congener. When R=Me the presence of trivalent ruthenium was proved by a rhombic e.p.r. spectrum having g₁=2.349, g₂=2.310.     

Effect of ring substituents on crystal packing and H-bonding in a series of halobis(phen)copper(II) arylphosphonic acid complexes

The synthesis and crystal structures of five new analogues of the supramolecular copper(II) organophosphonate [Cu^II(phen)₂Cl][(C₆H₅PO(OH)₂)((OH)O₂PC₆H₅)] (1) are presented. The structures contain substituted phenylphosphonic acids, and are of the general formula [Cu^II(phen)₂Cl][(XPO(OH)₂)((OH)O₂PX)] · Z, where X = o-CH₃(C₆H₅) (2); X = p-CH₃(C₆H₅), Z = H₂O · 2CH₃CH₂OH (4); X = o-NO₂(C₆H₅), m-NO₂(C₆H₅) (5); X = m-NO₂(C₆H₅) (6); X = C₁₀H₇ (7).     

Synthesis,spectroscopic, thermal and biological aspect of mixed ligand copper(II) complexes

Derivative of 8-hydroxyquinoline i.e. Clioquinol is well known for its antibiotic properties, drug design and coordinating ability towards metal ion such as Copper(II). The structure of mixed ligand complexes has been investigated using spectral, elemental and thermal analysis. In vitro anti microbial activity against four bacterial species were performed i.e. Escherichia coli, Pseudomonas aeruginosa, Serratia marcescens, Bacillus substilis and found that synthesized complexes (15–37 mm) were found to be significant potent compared to standard drugs (clioquinol i.e. 10–26 mm), parental ligands and metal salts employed for complexation. The kinetic parameters such as order of reaction (n = 0.96–1.49), and the energy of activation (E _a = 3.065–142.9 kJ mol⁻¹), have been calculated using Freeman–Carroll method. The range found for the pre-exponential factor (A), the activation entropy (S* = −91.03 to−102.6 JK⁻¹ mol⁻¹), the activation enthalpy (H* = 0.380–135.15 kJ mol⁻¹), and the free energy (G* = 33.52–222.4 kJ mol⁻¹) of activation reveals that the complexes are more stable. Order of stability of complexes were found to be [Cu(A⁴)(CQ)OH] · 4H₂O > [Cu(A³)(CQ)OH] · 5H₂O > [Cu(A¹)(CQ)OH] · H₂O > [Cu(A²)(CQ)OH] · 3H₂O     

Synthesis of [Ni(η-CH2C6H4R-4){PPh(CH2CH2PPh2)2}] (R = H, Me or MeO) and protonation reactions with HCl

The complexes [Ni(η²-CH₂C₆H₄R-4)(triphos)]BPh₄ {R = H, Me or MeO; triphos = PhP(CH₂CH₂PPh₂)₂} have been prepared and characterised by spectroscopy and X-ray crystallography. In all cases the coordination geometry of the nickel is best described as square-planar with an η²-benzyl ligand occupying one of the positions. The orientation of the η²-benzyl ligand is dictated by the steric restrictions imposed by the phenyl groups on the triphos ligand, so that the phenyl group on the unique secondary phosphorus and the aromatic group of the benzyl ligand (which are trans to one another) are oriented in the same direction. [Ni(η²-CH₂C₆H₄R-4)(triphos)]⁺ react with an excess of anhydrous HCl in MeCN to form [NiCl(triphos)]⁺ (characterised as the [BPh₄]⁻ salt by X-ray crystallography) and the corresponding substituted toluene. The kinetics of the reaction of all [Ni(η²-CH₂C₆H₄R-4)(triphos)]⁺ and HCl in the presence of Cl⁻ have been determined using stopped-flow spectrophotometry. All reactions exhibit a first-order dependence on the concentration of complex and a first-order dependence on the ratio [HCl]/[Cl⁻]. Varying the 4-R-substituent on the benzyl ligand shows that electron-withdrawing substituents facilitate the rate of the reaction. It is proposed that the mechanism involves initial rapid protonation at the nickel to form [NiH(η²-CH₂C₆H₄R-4)(triphos)]²⁺, followed by intramolecular proton migration from nickel to carbon to yield the products.     

Determination of heat capacities of PbCrO4(s), Pb2CrO5(s), and Pb5CrO8(s)

Abstract  

Heat capacities of PbCrO₄(s), Pb₂CrO₅(s), and Pb₅CrO₈(s) were measured by differential scanning calorimetry. The measured heat capacities as a function of temperature are expressed as C _p <PbCrO₄> J K⁻¹ mol⁻¹ = 150.37 + 27.74 × 10⁻³ T − 2.80 × 10⁶ T ⁻² (T = 300–750 K), C _p <Pb₂CrO₅> J K⁻¹ mol⁻¹ = 194.55 + 76.09 × 10⁻³ T − 4.64 × 10⁶ T ⁻² (T = 300–700 K), and C _p  <Pb₅CrO₈> J K⁻¹ mol⁻¹ = 323.35 + 184.80 × 10⁻³ T − 5.48 × 10⁶ T ⁻² (T = 300–600 K). From the measured heat capacity data, thermodynamic functions such as enthalpy increments, entropies, and Gibbs energy functions were derived.