In[IO3](OH)2 – New member of hydrous and anhydrous iodate family with indium

A new indium iodate hydrate In[IO₃](OH)₂ was synthesized by the hydrothermal methods. Single crystal X-ray diffraction revealed centrosymmetric Pnma space group. [IO₃]-groups have typical umbrella-like configuration: iodine atom and three oxygens with I–O distances ∼1.8 Å. In-octahedra have 4 equatorial OH-groups and 2 apical O-atoms of 2 [IO₃]-groups and are connected into the layers via OH-groups. It is found that indium iodate family without any other metals is a regular row of compounds: anhydrous In[IO₃]₃, one hydrated In[IO₃]₂(OH)·H₂O, new two hydrated In[IO₃](OH)₂ and “end member” represented by three hydrated hydroxide In(OH)₃. Chemical relations are parallel to the structural: In-octahedral framework in In-hydroxide, In-octahedral layer as a fragment of the framework, In-octahedral chain as a fragment of the layer, isolated In-octahedra as a fragment of the chain with no In-octahedral condensation via vertices but only via [IO₃]-groups in anhydrous In-iodate. If alkali metals are introduced in anhydrous In-iodates, their influence is different. Large metals as K, Rb, Cs hinder condensation of {In[IO₃]₆}³⁻ blocks which are isolated in the structures whereas smaller Li, Na metals allows condensation up to bands {In[IO₃]₄}¹⁻_∞. Octahedral chains selected in hydrated In-iodates are similar to chains in nonlinear optical compound TiO[IO₃]₂. The reasons of polarity or non-polarity and possible elements substitutions promising for properties are discussed.     

Bi2(IO3)(IO6): First combination of [IO3]− and [IO6]5− anions in three-dimensional framework

A new bismuth (III) iodate periodate, Bi₂(IO₃)(IO₆) was obtained from hydrothermal reactions using Bi(NO₃)₃·5H₂O, and H₅IO₆ as starting materials. Bi₂(IO₃)(IO₆) crystallizes in the monoclinic space group P2₁/c (No. 14) with lattice parameters ɑ = 8.1119(6), b = 5.4746(4), c = 16.357(1) Å, β = 99.187(2)°, V = 717.07(9) ų, Z = 4. The structure of Bi₂(IO₃)(IO₆) features a three-dimensional framework which is a combination of [Bi(1)O₅] tetragonal pyramids, [Bi(2)O₈] bicapped trigonal prisms and [IO₃]⁻ and [IO₆]⁵⁻ anions. Thermal analysis shows that the compound is thermally stable up to about 350 °C. The solid state UV-vis-NIR diffuse reflectance spectrum indicates that Bi₂(IO₃)(IO₆) is a semiconductor with a band gap of 2.76 eV.     

X‐Ray Crystal Structures of Hexa‐oxotellurate Complexes of Ruthenium(VI) and Silver(III): Na6[RuO2{TeO4(OH)2}2]·16H2O and Na5[Ag{TeO4(OH)2}2]·16H2O

X‐ray crystal structures are reported for Na₆[RuO₂{TeO₄(OH)₂}₂]·16H₂O and Na₅[Ag{TeO₄(OH)₂}₂]·16H₂O which contain respectively Ru^VI and Ag^III coordinated to chelating bidentate tellurate ([TeO₄(OH)₂]⁴⁻) groups. Na₆[RuO₂{TeO₄(OH)₂}₂]·16H₂O: Space group P1¯, Z = 2, lattice dimensions at 120 K; a = 6.9865(1), b = 8.7196(2), c = 11.7395(2)Å, α = 74.008(1), β = 79.954(1), γ = 88.514(1)°; R1 = 0.025. Na₅[Ag{TeO₄(OH)₂}₂]·16H₂O: Space group P1¯, Z = 2, lattice dimensions at 120 K; a = 5.888(1), b = 8.932(1), c = 12.561(2)Å, α = 98.219(6), β = 97.964(9), γ = 93.238(14)°; R1 = 0.047.     

Hydrothermal syntheses of materials constructed from vanadium oxide and secondary metal-tetrapyridylpyrazine subunits. Structural consequences of the identity of the secondary metal

Hydrothermal reactions of V₂O₅, tetra-2-pyridylpyrazine (tpyprz) and an appropriate M(II) starting material yield a series of oxides of general composition [{M_x(tpyprz)}_yV₄O₁₂] [x=1, y=2, M=Co(II), Ni(II); x=2, y=2, M=Cu(I); x=2, y=1, M=Zn(II)]. The Co(II) and Ni(II) analogues (1 and 2) are isostructural and consist of one-dimensional ribbons constructed from {V₄O₁₂}⁴⁻ clusters linked through {M(tpyprz)}₂⁴⁺ binuclear units of edge sharing {MO₃N₃} octahedra. In contrast, the structure of [{Cu₂(tpyprz)}₂V₄O₁₂] (3) is two-dimensional and constructed of {Cu₂(tpyprz)}_n²ⁿ⁺ chains linked in the second dimension through the {V₄O₁₂}⁴⁻ clusters. The structure of [{Zn₂(tpyprz)V₄O₁₂] (4) is also two-dimensional but may be described as {Zn₂V₄O₁₂} chains interconnected through the binucleating tpyprz ligands. The roles of the coordination preferences of the secondary metal cations as well as the nature of the organic components are discussed.     

Untersuchungen zur Darstellung von [CpxSb{M(CO)5}2] (Cpx = Cp,Cp*; M = Cr,W)

Investigations of the Synthesis of [Cp^xSb{M(CO)₅}₂] (Cp^x = Cp, Cp*; M = Cr, W) The reaction of CpSbCl₂ with [Na₂{Cr₂(CO)₁₀}] leads to the chlorostibinidene complex [ClSb{Cr(CO)₅}₂(thf)] ( 1 ), whereas the reaction of CpSbCl₂ with [Na₂{W₂(CO)₁₀}] results in the formation of the complexes [ClSb{W(CO)₅}₃] ( 2 ), [Na(thf)][Cl₂Sb{W(CO)₅}₂] ( 3 ), [ClSb{W(CO)₅}₂(thf)] ( 4 ) and [Sb₂{W(CO)₅}₃] ( 5 ). The stibinidene complex [CpSb{Cr(CO)₅}₂] ( 6 ) is obtained by the reaction of [ClSb{Cr(CO)₅}₂] with NaCp, while its Cp* analogue [Cp*Sb{Cr(CO)₅}₂] ( 7 ) is formed via the metathesis of Cp*SbCl₂ with [Na₂{Cr₂(CO)₁₀}]. The products 2 , 3 , 4 and 7 are additionally characterised by X‐ray structure analyses.     

Molecular Nitrides with Titanium and Group 13–15 Elements

Several heterometallic nitrido complexes were prepared by reaction of the imido–nitrido titanium complex [{Ti(η⁵‐C₅Me₅)(μ‐NH)}₃(μ₃‐N)] ( 1 ) with amido derivatives of Group 13–15 elements. Treatment of 1 with bis(trimethylsilyl)amido [M{N(SiMe₃)₂}₃] derivatives of aluminum, gallium, or indium in toluene at 150–190 °C affords the single‐cube amidoaluminum complex [{(Me₃Si)₂N}Al{(μ₃‐N)₂(μ₃‐NH)Ti₃(η⁵‐C₅Me₅)₃(μ₃‐N)}] ( 2 ) or the corner‐shared double‐cube compounds [M(μ₃‐N)₃(μ₃‐NH)₃{Ti₃(η⁵‐C₅Me₅)₃(μ₃‐N)}₂] [M=Ga ( 3 ), In ( 4 )]. Complexes 3 and 4 were also obtained by treatment of 1 with the trialkyl derivatives [M(CH₂SiMe₃)₃] (M=Ga, In) at high temperatures. The analogous reaction of 1 with [{Ga(NMe₂)₃}₂] at 110 °C leads to [{Ga(μ₃‐N)₂(μ₃‐NH)Ti₃(η⁵‐C₅Me₅)₃(μ₃‐N)}₂] ( 5 ), in which two [GaTi₃N₄] cube‐type moieties are linked through a gallium–gallium bond. Complex 1 reacts with one equivalent of germanium, tin, or lead bis(trimethylsilyl)amido derivatives [M{N(SiMe₃)₂}₂] in toluene at room temperature to give cube‐type complexes [M{(μ₃‐N)₂(μ₃‐NH)Ti₃(η⁵‐C₅Me₅)₃(μ₃‐N)}] [M=Ge ( 6 ), Sn ( 7 ), Pb ( 8 )]. Monitoring the reaction of 1 with [Sn{N(SiMe₃)₂}₂] and [Sn(C₅H₅)₂] by NMR spectroscopy allows the identification of intermediates [RSn{(μ₃‐N)(μ₃‐NH)₂Ti₃(η⁵‐C₅Me₅)₃(μ₃‐N)}] [R=N(SiMe₃)₂ ( 9 ), C₅H₅ ( 10 )] in the formation of 7 . Addition of one equivalent of the metalloligand 1 to a solution of lead derivative 8 or the treatment of 1 with a half equivalent of [Pb{N(SiMe₃)₂}₂] afford the corner‐shared double‐cube compound [Pb(μ₃‐N)₂(μ₃‐NH)₄{Ti₃(η⁵‐C₅Me₅)₃(μ₃‐N)}₂] ( 11 ). Analogous antimony and bismuth derivatives [M(μ₃‐N)₃(μ₃‐NH)₃{Ti₃(η⁵‐C₅Me₅)₃(μ₃‐N)}₂] [M=Sb ( 12 ), Bi ( 13 )] were obtained through the reaction of 1 with the tris(dimethylamido) reagents [M(NMe₂)₃]. Treatment of 1 with [AlCl₂{N(SiMe₃)₂}(OEt₂)] affords the precipitation of the singular aluminum–titanium square‐pyramidal aggregate [{{(Me₃Si)₂N}Cl₃Al₂}(μ₃‐N)(μ₃‐NH)₂{Ti₃(η⁵‐C₅Me₅)₃(μ‐Cl)(μ₃‐N)}] ( 14 ). The X‐ray crystal structures of 5 , 11 , 13 , 14 , and [AlCl{N(SiMe₃)₂}₂] were determined.     

Polyoxotungstate Archetype {P4W27} and its 3d Derivatives

The propensity of the new, phenylphosphonate-stabilized polyoxotungstate [(C₆H₅P^VO)₂P₄W₂₄O₉₂]¹⁶⁻ to act as a precursor for new 3d metal-functionalized polyanions has been investigated. Reactions with Mn^II and Cu^II induce the formation of the previously unknown polyoxotungstate archetype {P₄W₂₇}, isolated as salts of the polyanions [Na⊂{Mn^II(H₂O)}{WO(H₂O)}P₄W₂₆O₉₈]¹³⁻ ( 1 ) and [K⊂{Cu^II(H₂O)}{W(OH)(H₂O)}P₄W₂₇O₉₉]¹⁴⁻ ( 2 ), which were characterized in the solid state (single-crystal X-ray diffraction, elemental and TG analyses, IR spectroscopy, SQUID magnetometry) and in aqueous solution (UV/Vis spectroscopy, cyclic voltammetry).     

dl-Serine covalently modified multinuclear lanthanide-implanted arsenotungstates with fast photochromism

A series of dl-serine covalently modified multinuclear lanthanide implanted arsenotungstates K₂[{Ln(H₂O)₇}₂{As₄W₄₄O₁₃₇(OH)₁₈(H₂O)₂(dl-Ser)₂}{Ln₂(H₂O)₅(dl-Ser)}₂]·65H₂O (dl-Ser = dl-serine, Ln = La (1), Ce (2), Pr (3)) are obtained. Crystal structure analysis shows that these compounds are isomorphic and contain the basic [{As₄W₄₄O₁₃₇(OH)₁₈(H₂O)₂(dl-Ser)₂}{Ln₂(H₂O)₅(dl-Ser)}₂]^8– polyoxoanion constituted by two {As₂W₁₉O₅₉(OH)₈(H₂O)}^6? subunits, a [W₆O₂₃(OH)₂(dl-Ser)₂]^14? fragment, and two embedded [Ln₂(H₂O)₅(dl-Ser)]⁵⁺ groups, which further build into one dimensional linear chainlike structure via two peripheral Ln³⁺ ions. Most remarkably, these compounds exhibit rapid photochromic behaviors, which changed color quickly from white (1), yellow (2), green (3) to blue (1), brown (2) and glaucous (3) in ten minutes under UV irradiation, and that the colors gradually recovered in the dark for approximately 22 h.     

Mössbauer study of some Fe-containing M6 and M5 clusters

Isomer shift (δ) and quadrupole splitting (Δ) parameters have been assigned to the iron sites in [FeRh₅(CO)₁₆]⁻, trans- and cis-[Fe₂Rh₄(CO)₁₆]²⁻, [Fe₃-Rh₃(CO)₁₇]³⁻, [FeRh₄(CO)₁₅]²⁻, [Fe₃Pt₃(CO)₁₅]²⁻ and [Fe₄M(CO)₁₆]²⁻ (M = Pd or Pt) from ⁵⁷Fe Mössbauer spectra recorded at 78 K. The data for the closo compounds [FeRh₅(CO)₁₆]⁻ and [Fe₂Rh₄(CO)₁₆]²⁻ are compared with those for [Fe₆(CO)₁₆C]²⁻. In [Fe₃Rh₃(CO)₁₇]³⁻, the three major Fe sites were identified. For both [Fe₄M(CO)₁₆]²⁻ compounds two isomers were shown to be present in the solid state.     

Synthesis and chemical characterization of some InFe heteronuclear carbonyl compounds; crystal structure of [NMe3CH2Ph]3[In{Fe(CO)4}3] and [NEt4]2[In2Br4{η-Fe(CO)4}2]

The reaction in THF of Na₂[Fe(CO)₄·xTHF with InBr₃ in an approximate 3.5:1 molar ratio affords the new [In{Fe(CO)₄}₃]³⁻ trianion, which has been isolated as its trimethylbenzylammonium salt and structurally characterized by single-crystal X-ray diffraction studies. On oxidation with two equivalents of AgBF₄ it stepwise affords the anions [In₂Fe₆(CO)₂₄]^x− with x = 4 and 2, respectively. Its reaction with InBr₃ gives species of the composition [InBr_3−x{Fe(CO)_4x}]^x− (x = 1,2), and the anion with the composition [InBr₂{Fe(CO)₄}]⁻ has been structurally characterized as the dimeric species [InBr₂Br₄{η-Fe(CO)₄}₂]²⁻.     

Mono- and bis-alkoxides of tris(3,5-dimethylpyrazolyl)borato molybdenum and tungsten nitrosyls

The complexes [ML^*(NO)Cl(OR)] {L^* = HB(3,5-Me₂C₃HN₂)₃; M= Mo, R = CH₂CH₂X, X = Cl, OMe or OEt; (CH₂)_nOH, n = 2, 5, 6; M = W, R = CH₂CH₂X, X = Cl, OMe or OEt; (CH₂)_nOH, n = 2–6; CH₂(CF₂)₃CH₂OH; CHMeCH₂CMe₂OH} and [ML^*(NO)(OR)₂] {M = Mo, R = CH₂CH₂X, X = Cl, OMe or OEt; (CH₂)_nOH, n = 2–6; M = W,R = CH₂CH₂X, X= Cl, OMe or OEt; (CH₂)_nOH, n = 2,4–6; CH₂(CF₂)₃CH₂OH} have been prepared from [ML^*(NO)Cl₂] and the appropriate alcohol in the presence of NEt₃ or NaCO₃, and have been characterized by IR, ¹H NMR and mass spectroscopy.     

Synthesis and structure of novel coordination compounds based on [Re<Subscript>6</Subscript>Q<Subscript>8</Subscript>(CN)<Subscript>6</Subscript>]<Superscript>4–</Superscript> (Q = S,Se) and (SnMe<Subscript>3</Subscript>)<Superscript>+</Superscript>

The reactions of SnMe₃Cl with salts of the cluster anionic complexes [Re₆Q₈(CN)₆]^4? (Q = S, Se) gave novel complexes [{(SnMe₃)₂(OH)}₂{SnMe₃}₂{Re₆S₈(CN)₆}] (I), (Me₄N)₂[{SnMe₃(H₂O)}₂{Re₆Se₈(CN)₆}] (II), [{(SnMe₂)₄(μ₃-O)}₂{Re₆Se₈(CN)₆}] (III), and [(SnMe₂)₄(μ₃-O)₂(μ₂-OH)₂(H₂O)₂][{SnMe_{3 2}{Re₆Se₈(CN)₆}] (IV). The structures of I–IV were determined by X-ray diffraction. Compounds I, IV have the chain structures with the CN-SnMe₃-NC bridges between the cluster anions [Re₆Q₈(CN)₆]^4?. Compound II contains isolated fragments {SnMe₃(H₂O)}₂{Re₆Se₈(CN)₆}^2?. In the polymer framework of compound III, the cluster anionic complexes [Re₆Se₈(CN)₆]^4? are bound by the complex cations [(SnMe₂)₄(μ₃-O)₂]⁴⁺ formed due to the hydrolysis of the initial (SnMe₃)Cl.     

Supramolecular Frameworks Based on Rhenium Clusters Using the Synthons Approach

The reaction of the K₄[{Re₆Sⁱ₈}(OH)^a₆]·8H₂O rhenium cluster salt with pyrazine (Pz) in aqueous solutions of alkaline or alkaline earth salts at 4 °C or at room temperature leads to apical ligand exchange and to the formation of five new compounds: [trans-{Re₆Sⁱ₈}(Pz)^a₂(OH)^a₂(H₂O)^a₂] (1), [cis-{Re₆Sⁱ₈}(Pz)^a₂(OH)^a₂(H₂O)^a₂] (2), (NO₃)[cis-{Re₆Sⁱ₈}(Pz)^a₂(OH)^a(H₂O)^a₃](Pz)·3H₂O (3), [Mg(H₂O)₆]_0.5[cis-{Re₆Sⁱ₈}(Pz)^a₂(OH)^a₃(H₂O)^a]·8.5H₂O (4), and K[cis-{Re₆Sⁱ₈}(Pz)^a₂(OH)^a₃(H₂O)^a]·8H₂O (5). Their crystal structures are built up from trans- or cis-[{Re₆Sⁱ₈}(Pz)^a₂(OH)^a_4−x(H₂O)^a_x]^x−2 cluster units. The cohesions of the 3D supramolecular frameworks are based on stacking and H bonding, as well as on H₃O₂₋bridges in the cases of (1), (2), (4), and (5) compounds, while (3) is built from stacking and H bonding only. This evidences that the nature of the synthons governing the cluster unit assembly is dependent on the hydration rate of the unit.     

ABi2(IO3)2F5 (A=K,Rb, and Cs): A Combination of Halide and Oxide Anionic Units To Create a Large Second‐Harmonic Generation Response with a Wide Bandgap

A family of nonlinear optical materials that contain the halide, oxide, and oxyhalide polar units simultaneously in a single structure, namely ABi₂(IO₃)₂F₅ (A=K ( 1 ), Rb ( 2 ), and Cs ( 3 )), have been designed and synthesized. They crystallize in the same polar space group (P 2₁) with a two‐dimensional double‐layered framework constructed by [BiF₅]²⁻ and [BiO₂F₄]⁵⁻ units connected to each other by four F atoms, in which two [IO₃]⁻ groups are linked to [BiO₂F₄]⁵⁻ unit on the same side. A hanging Bi−F bond of [BiF₅]²⁻ unit is located on the other side via ionic interaction with the layer‐inserted alkali metal ions to form three‐dimensional structure. The well‐ordered alignments of these polar units lead to a very strong second‐harmonic generation response of 12 ( 1 ), 9.5 ( 2 ), and 7.5 ( 3 ) times larger than that of potassium dihydrogen phosphate under 1064 nm laser radiation. All of them exhibited a wide energy bandgap over 3.75 eV, suggesting that they will have a high laser damage threshold.     

Tritopic NHC Precursors: Unusual Nickel Reactivity and Ethylene Insertion into a C(sp3)–H Bond

The imidazolium chloride [C₃H₃N(C₃H₆NMe₂)N{C(Me)(=NDipp)}]Cl ( 1 ; Dipp=2,6‐diisopropyl phenyl), a potential precursor to a tritopic N^imineC^NHCN^amine pincer‐type ligand, reacted with [Ni(cod)₂] to give the Ni^I‐Ni^I complex 2 , which contains a rare cod‐derived η³‐allyl‐type bridging ligand. The implied intermediate formation of a nickel hydride through oxidative addition of the imidazolium C−H bond did not occur with the symmetrical imidazolium chloride [C₃H₃N₂{C(Me)(=NDipp)}₂]Cl ( 3 ). Instead, a Ni−C(sp³) bond was formed, leading to the neutral N^imineCHN^imine pincer‐type complex Ni[C₃H₃N₂{C(Me)(=NDipp)}₂]Cl ( 4 ). Theoretical studies showed that this highly unusual feature in nickel NHC chemistry is due to steric constraints induced by the N substituents, which prevent Ni−H bond formation. Remarkably, ethylene inserted into the C(sp³)−H bond of 4 without nickel hydride formation, thus suggesting new pathways for the alkylation of non‐activated C−H bonds.     

ABi2(IO3)2F5 (A=K,Rb, and Cs): A Combination of Halide and Oxide Anionic Units To Create a Large Second‐Harmonic Generation Response with a Wide Bandgap

A family of nonlinear optical materials that contain the halide, oxide, and oxyhalide polar units simultaneously in a single structure, namely ABi₂(IO₃)₂F₅ (A=K ( 1 ), Rb ( 2 ), and Cs ( 3 )), have been designed and synthesized. They crystallize in the same polar space group (P 2₁) with a two‐dimensional double‐layered framework constructed by [BiF₅]²⁻ and [BiO₂F₄]⁵⁻ units connected to each other by four F atoms, in which two [IO₃]⁻ groups are linked to [BiO₂F₄]⁵⁻ unit on the same side. A hanging Bi−F bond of [BiF₅]²⁻ unit is located on the other side via ionic interaction with the layer‐inserted alkali metal ions to form three‐dimensional structure. The well‐ordered alignments of these polar units lead to a very strong second‐harmonic generation response of 12 ( 1 ), 9.5 ( 2 ), and 7.5 ( 3 ) times larger than that of potassium dihydrogen phosphate under 1064 nm laser radiation. All of them exhibited a wide energy bandgap over 3.75 eV, suggesting that they will have a high laser damage threshold.     

Coordination Properties of Perfluoroethyl‐ and Perfluorophenyl‐Substituted Phosphonous acids,RfP(OH)2

Phosphinic acids, R^fP(O)(OH)H (R^f=CF₃, C₂F₅, C₆F₅), turned out to be excellent preligands for the coordination of phosphonous acids, R^fP(OH)₂. Addition of C₂F₅P(O)(OH)H to solid PtCl₂ under different reaction conditions allows the isolation and full characterization of the mononuclear complexes [ClPt{P(C₂F₅)(OH)O}{P(C₂F₅)(OH)₂}₂] and [Pt{P(C₂F₅)(OH)O}₂{P(C₂F₅)(OH)₂}] containing hydrogen‐bridged [R^fP(OH)O]^? and R^fP(OH)₂ units. Further deprotonation of [Pt{P(C₂F₅)(OH)O}₂{P(C₂F₅)(OH)₂}₂] leads to the formation of the dianionic platinate, [Pt{P(C₂F₅)(OH)O}₄]^2?, revealing four intramolecular hydrogen bridges. With PdCl₂ the dinuclear complex [Pd₂(μ‐Cl)₂{[P(C₂F₅)(OH)O]₂H}₂] was isolated and characterized. The Cl^? free complex [Pd{P(C₂F₅)(OH)O}₂{P(C₂F₅)(OH)₂}₂] was also prepared and deprotonated to the dianionic palladate, [Pd{P(C₂F₅)(OH)O}₄]^2?. Both compounds were characterized by NMR spectroscopy, IR spectroscopy, and X‐ray analyses. In addition, the C₆F₅ derivatives [ClPt{P(C₆F₅)(OH)O}{P(C₆F₅)(OH)₂}₂] and [Pd₂(μ‐Cl)₂{[P(C₆F₅)(OH)O]₂H}₂] as well as the CF₃ derivative [Pd₂(μ‐Cl)₂{[P(CF₃)(OH)O]₂H}₂] were synthesized and fully characterized. Phosphonous acid complexes are inert towards air and moisture and can be stored for several months without decomposition. The catalytic activity of the palladium complexes in the Suzuki cross‐coupling reaction between 1‐bromo‐3‐fluorobenzene and phenyl boronic acid was demonstrated.     

Kinetics and mechanism of the two electron oxidation of cis-CrIII(dipy)2(H2O)2]3+ (dipy = 2,2′-dipyridyl) by periodate ion to cis-[CrV(dipy)2(O)2]+ in aqueous acidic solutions

The kinetics of oxidation of cis-[Cr^III(dipy)₂(H₂O)₂]³⁺ (dipy = 2,2′-dipyridyl) by IO₄ ^? has been studied in aqueous acidic solutions. The initial oxidation product is certainly not Cr(VI). The isolated solid product is consistent with the formula cis-[Cr^V(dipy)₂(O)₂]IO₄. The Cr(V) product has been isolated and characterized by elemental analysis, IR and ESR spectroscopy. In the presence of a vast excess of [IO₄ ^?], the reaction is first order in the chromium(III) complex concentration. The pseudo-first-order rate constant, k _obs, showed a very small change with increasing [IO₄ ^?]. The dependence of k _obs on [IO₄ ^?] is consistent with Eq. (i). i $$ {\text{k}}_{\text{obs}} = {\text{a}}[{\text{IO}}_{4}^{\text{ - }} ]/({\text{b}} + {\text{c}}[{\text{IO}}_{4}^{\text{ - }} ]) $$ The pseudo-first-order rate constant, k _obs, increased with increasing pH, indicating that the hydroxo form of the chromium(III) complex is the reactive species. An inner-sphere mechanism has been proposed for the oxidation process. The thermodynamic activation parameters of the processes involved are also reported.     

Syntheses,solid state electronic and infrared spectra of the Ni(II), Pd(II) and Cu(II) complexes of N-(2-hydroxyethyl) and N-(3-hydroxypropyl) oxamide

The new complexes K₂[Ni(Hheo)₂], K₂[Cu(Hheo)₂]·H₂O, K₂[Ni(Hhpo)₂]·H₂O, K₂[M(Hhpo)₂]·0.5H₂O (M = Cu, Pd) and K₂[Cu₂(hpo)₂·0.5H₂O, where H₃heo = N-(2-hydroxyethyl)oxamide and H₃hpo = N-(3-hydroxypropyl)oxamide, have been prepared. Several synthetic routes were investigated and the complexes were characterized by analyses, conductivity measurements, thermogravimetry, magnetic susceptibility and spectroscopy (i.r. and far i.r., diffuse reflectance u.v.). Monomeric square planar structures are found for the [M(Hheo)₂]²⁻ and [M(Hhpo)₂]²⁻ complex anions, while the hpo³⁻ Cu(II) complex appears to be a square planar dimer. The doubly deprotonated Hheo²⁻ and Hhpo²⁻ ions exhibit a bidentate N(secondary amide), N′(tertiary amide)-coordination with the OH-group remaining uncoordinated, while the triply deprotonated hpo³⁻ ion behaves as a bridging N(secondary amide), N′(tertiary amide), O(deprotonated) ligand, while two Cu(II) centres are bridged by two alkoxide-O atoms. The vibrational analysis of the dehydrated complexes is carried out, using NH/ND, OH/OD, ⁵⁸Ni/⁶²Ni and ⁶³Cu/⁶⁵Cu substitutions.