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Showing papers in "Inorganic Chemistry in 1991"





Journal ArticleDOI
TL;DR: The solution thermodynamics of the siderophore enterobactin, a powerful iron chelator, and of the synthetic analogue MECAM (N,N',N)-tris(2,3-dihydroxybenzoyl)-1,3,5-tris (aminomethyl)benzene) have been studied by UV spectrophotometry.
Abstract: The solution thermodynamics of the siderophore enterobactin, a powerful iron chelator, and of the synthetic analogue MECAM (N,N',N″-tris(2,3-dihydroxybenzoyl)-1,3,5-tris(aminomethyl)benzene) have been studied by UV spectrophotometry. Spectra were taken at high dilution by using a fully automatic, microcomputer-controlled spectrophotometer

278 citations


Journal ArticleDOI
TL;DR: In this article, the effect of electronegative bromine substituents at the peripheral positions of the porphyrin has been quantitatively analyzed by using the four-orbital approach of Gouterman.
Abstract: The free-base octabromotetraphenylporphyrin (H2OBP) has been prepared by a novel bromination reaction of (meso-tetraphenylporphyrinato)copper(II). The metal [V(IV)O, Co(II), Ni(II), Cu(II), Zn(II), Pd(II), Ag(II), Pt(II)] derivatives exhibit interesting electronic spectral features and electrochemical redox properties. The electron-withdrawing bromine substituents at the pyrrole carbons in H2OBP and M(OBP) derivatives produce remarkable red shifts in the Soret (50 nm) and visible bands (100 nm) of the porphyrin. The low magnitude of protonation constants (pK3 = 2.6 and pK4 = 1.75) and the large red-shifted Soret and visible absorption bands make the octabromoporphyrin unique. The effect of electronegative bromine substituents at the peripheral positions of the porphyrin has been quantitatively analyzed by using the four-orbital approach of Gouterman. A comparison of MO parameters of MOBP derivatives with those of the meso-substituted tetraphenylporphyrin (M(TPP)) and unsubstituted porphine (M(P)) derivatives provides an explanation for the unusual spectral features. The configuration interaction matrix element of the M(OBP) derivatives is found to be the lowest among the known substituted porphyrins, indicating delocalization of ring charge caused by the increase in conjugation of p orbitals of the bromine onto the ring orbitals. The electron-transfer reactivities of the porphyrins have been dramatically altered by the peripheral bromine substituents, producing large anodic shifts in the ring and metal-centered redox potentials. The increase in anodic shift in the reduction potential of M(OBP)s relative to M(TPP)s is found to be large (550 mV) compared to the shift in the oxidation potential (300 mV). These shifts are interpreted in terms of the resonance and inductive interactions of the bromine substituents.

277 citations


Journal ArticleDOI
TL;DR: In this article, the transmetalation reaction in common organic solvents is performed in 1,2-dimethoxyethane, and an ether adduct with two DME molecules is formed for each metal.
Abstract: Alkaline-earth-metal bis[bis(trimethylsilyl)amides] of magnesium, calcium, strontium, and barium have been isolated in high yield from bis[bis(trimethylsilyl)amido] tin (II) by utilizing the transmetalation reaction in common organic solvents. When this reaction is performed in 1,2-dimethoxyethane, an ether adduct with two DME molecules is formed for each metal. The alkaline-earth-metal diamides without complexating reagents appear to be dimeric in benzene and toluene

276 citations






Journal ArticleDOI
TL;DR: In a continuing study of Ni II,III complexes with low redox potentials that are of possible relevance to the nickel site in [NiFe]-hydrogenases, Ni II complexes of the tetraanions of the amide-thiol ligands N, N'-ethylenebis (2-mercaptoacetamide) N,N'-1,2-phenylenebis (1, 2)-phenylene bis (2mercaptoisobutyramide) have been prepared.
Abstract: In a continuing study of Ni II,III complexes with low redox potentials that are of possible relevance to the nickel site in [NiFe]-hydrogenases, Ni II complexes of the tetraanions of the amide-thiol ligands N,N'-ethylenebis (2-mercaptoacetamide) N,N'-1,2-phenylenebis (2-mercaptoacetamide), and N,N'-ethylenebis(2-mercaptoisobutyramide) have been prepared



Journal ArticleDOI
TL;DR: In this paper, the synthesis, molecular structure and chemical behavior of two chloride-dimethyl sulfoxide-ruthenium (III) derivatives, namely [(DMSO] 2 H][trans-Ru(DMSOsO) 2 Cl 4 ] (1) and mer-Ru (DMSoSO) 3 Cl 3 (2), are reported.
Abstract: The synthesis, molecular structure and chemical behavior of two chloride-dimethyl sulfoxide-ruthenium (III) derivatives, namely [(DMSO) 2 H][trans-Ru(DMSO) 2 Cl 4 ] (1) and mer-Ru(DMSO) 3 Cl 3 (2), are reported. They represent the first examples of fully characterized halogen-dimethyl sulfoxide-ruthenium (III) complexes

Journal ArticleDOI
TL;DR: In this article, three redox series of complexes of the general formula Ru(II) (bpy) 2LL an Ru(2,2'-bipyridine) 4LL are reported, where LL are the ligands, 1,2-dihydroxybenzen, 2-aminophenol or 1, 2 -diaminobenzene.
Abstract: : Three redox series of complexes of the general formula Ru(II) (bpy) 2LL an Ru(II) (Py)4LL (bpy=2,2'-bipyridine) are reported, where LL are the ligands, 1,2-dihydroxybenzen, 2-aminophenol or 1,2-diaminobenzene. These ligands can exist in the fully reduced catechol form, or the one and two electron oxidized semiquinone and quinone forms. Electronic and electron spin resonance spectroscopic, and electrochemical data are discussed in terms of orbital mixing and electronic structure, and the number of oxygen or nitrogen atoms in the coordinating ligand.

Journal ArticleDOI
TL;DR: The X-ray structural characterization of the iron amides [Fe{N(SiMe 3 ) 2 } 2 ] 2 (1) and [Fe(NPh 2 ) 2 ]2 (2) and the Lewis base adduct Fe[N[NMe 3 ] 2 ] (THF) (3), as well as the syntheses of the last two compounds, is described in this article.
Abstract: The X-ray structural characterization of the iron (II) amides [Fe{N(SiMe 3 ) 2 } 2 ] 2 (1) and [Fe(NPh 2 ) 2 ] 2 (2) and the Lewis base adduct Fe[N(SiMe 3 ) 2 ] 2 (THF) (3), as well as the syntheses of the last two compounds, is described. These complexes are rare examples of the coordination number 3 for iron. Compounds 1 and 2 are both dimeric in the solid state, with each trigonal-planar ion bound to one terminal and two bridging amides. They closely resemble the corresponding Mn(II) and Co(II) compounds. Compound 3 is monomeric in the solid state, with one THF and two amides arranged in a trigonal-planar fashion

Journal ArticleDOI
TL;DR: The insoluble silver thiolate compounds AgS(CH 2 ) 2 CH 3 (1), CH 2 ) 3 CH 4 (2), CH 5 (3), CH 6 H 5 (5), AgSC 6 H 4 4 -4-F (6), AgS 6H 4 4 4-4-Cl (7), Ag SC 6 H 3 4 -5-Br (8), AgCS 6 H 2 4 -6-OCH 3 (9), and AgSC 4 4 −4-Br(10) have not yielded crystals suitable for full
Abstract: The insoluble silver thiolate compounds AgS(CH 2 ) 2 CH 3 (1), AgS(CH 2 ) 3 CH 3 (2), AgS(CH 2 ) 5 CH 3 (3), AgS(CH 2 ) 7 CH 3 (4), AgSC 6 H 5 (5), AgSC 6 H 4 -4-F (6), AgSC 6 H 4 -4-Cl (7), AgSC 6 H 4 -4-Br (8), AgSC 6 H 4 -4-CH 3 (9) and AgSC 6 H 4 -4-OCH 3 (10) have not yielded crystals suitable for full diffraction analysis, but do reveal the essential features of their two-dimensionally nonmolecular structure in their powder diffraction patterns

Journal ArticleDOI
TL;DR: In this article, the six-coordinate diamagnetic osmium(IV) complexes OsH 2 Cl 2 (PR 3 ) 2 [PR 3 =P-i-Pr 3 (2), PMe-t-Bu (3)] are prepared from OsCl 3 •xH 2 O and PR 3 in boiling 2-propanol in 80% yield.
Abstract: The six-coordinate diamagnetic osmium(IV) complexes OsH 2 Cl 2 (PR 3 ) 2 [PR 3 =P-i-Pr 3 (2), PMe-t-Bu (3)] are prepared from OsCl 3 •xH 2 O and PR 3 in boiling 2-propanol in 80% yield. Treatment of 3 with CO leads to reductive elimination of H 2 and formation of all,trans-OsCl 2 (CO) 2 ((PMe-t-Bu 2 ) 2 . Likewise, 3 reacts with excess PMe 3 to give cis-Os-Cl 2 (PMe 3 ) 4 . The crystal and molecular structure of 2 has been determined. Crystal data for 2: monoclinic, P2 1 /c


Journal ArticleDOI
TL;DR: The trinuclear cluster Mn II 3 (CH 3 CO 2 ) 6 (bpy) 2 has been synthesized and its crystal structure was determined in this paper, and it crystallizes in the triclinic system, space group P1, with a=12.849, b=9.790, c=8.187, α=108.50, β=96.41, and V=912.5
Abstract: The new trinuclear cluster Mn II 3 (CH 3 CO 2 ) 6 (bpy) 2 has been synthesized, and its crystal structure was determined. It crystallizes in the triclinic system, space group P1, with a=12.849 (4) A, b=9.790 (3) A, c=8.187 (2) A, α=108.50 (2) o , β=96.69 (2) o , γ=106.41 (3) o , Z=1, and V=912.5 (5) A 3 . The structure was solved and refined by using 2071 reflections

Journal ArticleDOI
TL;DR: In this article, the structure of the tetranuclear anion [Mn4(p3-0),l8+ core with the four Mn atoms disposed in a "butterfly" arrangement and 0 atoms triply bridging each plane ('wing") was solved by direct methods and refined to values of conventional indices R (R), of 7.01% (6.90%) by using 5778 unique reflections with F > 349.
Abstract: structure was solved by direct methods (MULTAN) and refined to values of conventional indices R (R,) of 7.01% (6.90%) by using 5778 unique reflections with F > 349. The structure of the anion consists of an [Mn4(p3-0),l8+ core with the four Mn atoms disposed in a 'butterfly" arrangement and 0 atoms triply bridging each plane ('wing"). Peripheral ligation is provided by seven p-AcO- and two chelating pic- groups; the overall structure has idealized C, symmetry. The anion of 1 bears striking similarity to the cation [Mn402(02CMe)7(bpy)2]+ reported previously, showing little structural consequence of the pic-for-bpy substitution. Treatment of [Mn30(02CR),(py),](C104) (R = Me, Et) with Na(pic)-'/,HzO in MeCN leads to formation of sparingly soluble Na[ Mn402(02CR)7(pi~)2] providing an additional synthetic route to the tetranuclear anions. Complex 1 can be cleanly converted to 2 by treatment with excess PhCOOH in MeCN, demonstrating facile carboxylate exchange with more acidic acids. Variable-temperature, solid-state magnetic susceptibility studies have been performed on complex 1 in the range 5-300 K. The effective magnetic moment, pen/Mn4, decreases gradually from 7.98 pB at 300.0 K to 6.35 pB at 25.00 K and then decreases more rapidly to 3.28 pB at 5.00 K. The data were fit to a theoretical expression derived fromthe appfopriate spin Hamiltonian for a Mn4O2 core with C, symmetry which also included an axial zero-field splitting term [D(S: - 1/3ST2)] for the S = 3 ground state. The fitting parameters are Jwb = -5.3 cm-I, Jbb = -24.6 cm-l, g = 1.96, and D = 3.7 cm-l with TIP held constant at 200 X lod cgsu; Jbb refers to the interaction between the two-body bis(p-oxide)-bridged Mn"' atoms, and Jwb refers to the four mono(poxide)-bridged pairs of Mdl' atoms. The exchange parameters are very similar to those previously reported for (Mn402(02CMe)7(bpy)2](C104).3H,0 (Jwb = -7.8 cm-l, JN = -23.5 cm-I), consistent with the structural similarities between the two complexes. The spin frustration present in these [Mn4O2I8+ complexes is examined in detail. Depending on the magnitudes of Jwb and Jw, different ground states are found. The presence of p3-oxide-bridged Mn1114 units in these complexes causes frustration in the spin alignment at each Mn ion. The proton NMR spectral data are reported for complex 1 in CDCI,, CD3CN, and (CD3)*S0. The spectra in all three solvents are very similar, supporting retention of the solid-state structure of the anion of 1 in good donor solvents. The only major influence of the pic-for-bpy substitution is to be found in the redox properties investigated by cyclic voltammetry. Complexes 1 and 2 display a quasi-reversible oxidation in CH2C12 at +OS2 and +0.54 V vs ferrocene, respectively. The latter is to be contrasted with the value of +0.87 V found previously for [Mn402(02CPh)7(bpy)2](C104), showing that oxidation to the 3Mn'l',Mn'V oxidation level becomes easier when bpy is replaced by pic-.

Journal ArticleDOI
TL;DR: In this paper, the observed rhenium potentials for Re IV/III, Re III/II, and Re II/I reversible couples, for mononuclear species, were analyzed in terms of the electrochemical parametrization scheme based upon Ru III/I couples.
Abstract: The observed rhenium potentials for Re IV/III , Re III/II , and Re II/I reversible couples, for mononuclear species, are analyzed in terms of the electrochemical parametrization scheme based upon the Ru III/II couples. Two independent sets of Re II/I potentials are observed, which, if extended, would cross the Re III/II correlation line. The possible significance of these sets is explored. The Re IV/II couple correlation is roughly parallel to one of the Re II/I correlation lines. The analysis leads to some interesting avenues for future synthetic studies

Journal ArticleDOI
TL;DR: In this paper, the formato complex cis-[Ru(bpy) 2 (CO)(OC(O)H)] 0 was shown to be a catalyst for the electrochemical reduction of CO 2 in CH 3 CN with added water.
Abstract: The complex cis-[Ru(bpy) 2 (CO)H] + was shown to be a catalyst for the electrochemical reduction of CO 2 in CH 3 CN with added water. One product of the reduction is the formate anion. It is formed in a catalytic cycle which involves one-electron, bpy-based reduction of cis-[Ru(bpy) 2 (CO)H] + , insertion of CO 2 into the Ru-H bond to give the once-reduced formato complex cis-[Ru(bpy) 2 (CO)(OC(O)H)] 0 , and a subsequent, one-electron reduction of this complex, which leads to the loss of formate anion

Journal ArticleDOI
TL;DR: In this paper, the authors reported another case of reactivity that involves addition to a C-C bond of a 6-6 ring fusion in the carbon cluster, where the platinum atom is bound to carbon atoms again at a 6 -6 ring junction.
Abstract: The recent discovery that C[sub 60] (buckminsterfullerene) can be isolated in macroscopic quantities has led to widespread interest in its chemical and physical properties. C[sub 60] has icosahedral D[sub 5h] symmetry with 20 six-membered rings that are interconnected with 12 five-membered rings. There are two types of C-C bonds within this cluster: one type occurs at the 6-6 ring fusions, while the other occurs at the 6-5 ring fusions. There are no 5-5 ring fusions. Two crystalline derivatives of C[sub 60] have been obtained by addition of transition-metal complexes to the cluster. Addition of osmium tetraoxide and tert-butylpyridine produces C[sub 60]O[sub 2]OsO[sub 2](NC[sub 5]H[sub 4]CMe[sub 3])[sub 2] in which an O[sub 2]Os unit has added across a 6-6 ring fusion in the carbon cluster. Addition of C[sub 60] to (Ph[sub 3]P)[sub 2]Pt(ethylene) results in displacement of ethylene and formation of ([eta][sup 2]-C[sub 60])Pt(PPh[sub 3])[sub 2]. In this complex, the platinum atom is bound to carbon atoms again at a 6-6 ring junction of the carbon cluster. Here the authors report another case of reactivity that involves addition to a C-C bond of a 6-6 ring fusion.

Journal ArticleDOI
TL;DR: In the space group Pmn2 1 as mentioned in this paper, layered metal phosphonates M(O 3 PCH 3 )•H 2 O (Mg, Zn, Co) occur topochemically to give anhydrous salts with similar unit cell dimensions.
Abstract: Dehydration of layered metal phosphonates M(O 3 PCH 3 )•H 2 O (M=Mg, Zn, Co) occurs topochemically to give anhydrous salts M(O 3 PCH 3 ) with similar unit cell dimensions in the space group Pmn2 1 . Mg(O 3 PCH 3 ) absorbs water rapidly from air, forming Mg(O 3 PCH 3 )•H 2 O; Co(O 3 PCH 3 ) does so less readily, and Zn(O 3 PCH 3 ) is unreactive even with liquid water. Anhydrous Co and Zn salts M(O 3 PCH 3 ) react with ammonia and primary amines to form intercalation compounds M(O 3 PCH 3 ) (RNH 2 ), R=H to n-C 8 H 17

Journal ArticleDOI
TL;DR: In this article, the crystal structure of (Ru(trpy)(bpy)(py))(PF{sub 6}), sub 2{center dot}(CH{sub 3})-CO has been determined with a diffractometer, and the structure was solved by the full-matrix least-squares method, and after the final stage of refinement, R = 00055
Abstract: In acetonitrile and in the presence of appropriate nucleophiles, the complex (Ru(trpy)(bpy)(NCCH{sub 3})){sup 2+} undergoes a ligand substitution reaction when irradiated into the metal-to-ligand absorption band system (trpy = 2,2{prime}:6{prime},2{double prime}-terpyridine, and bpy = 2,2{prime}-bipyridine) At 25C quantum yields for displacement of the acetonitrile ligand are 00013 (1), 00013 (1), and 00026 (5) for 10 M solutions of pyridine, 4-phenylpyridine, and 2-methylpyridine, respectively No photochemistry is observed for the osmium(II) analogue, and all findings can be understood in terms of a dissociative reaction mechanism involving a reactive {sup 3}d-d state The {sup 3}d-d state is accessed from a {sup 3}CT state, which is emissive below ca 180 K From measurements of the temperature dependence of the emission lifetime, the barrier to population of the {sup 3}d-d state is approximately 1,500 cm{sup {minus}} Finally, the crystal structure of (Ru(trpy)(bpy)(py))(PF{sub 6}){sub 2}{center dot}(CH{sub 3}){sub 2}CO has been determined with a diffractometer The compound crystallizes with two independent formula units in a triclinic unit cell, and the crystal structure is reported The structure was solved by the full-matrix least-squares method, and after the final stage of refinement, R = 00055 There is evidence of interligand steric strain within the coordination sphere, and themore » bpy ligand is coordinated asymmetrically with a difference in Ru-N bond lengths of about 004 {Angstrom} The internal strain probably explains why the authors have been unable to prepare the 2-methylpyridine analogue by standard methods« less


Journal ArticleDOI
TL;DR: In this paper, the pK[sub a] values of the mixed-valence dinuclear complexes are quite close to those of each M(II) and M(III) component, which suggests that the bridging ligand can be used to serve as a trigger signal for switching the metal-metal interaction.
Abstract: New dinuclear complexes [M(L)[sub 2](bpbimH[sub 2])M(L)[sub 2]][sup 4+] (M = Ru, Os; L = bpy, phen; bpbimH[sub 2] = 2,2[prime]-bis(2-pyridyl)bibenzimidazole) act as dibasic acids. Both the absorption spectra and oxidation potentials are strongly dependent on the solution pH, which is responsible for the deprotonation of the N-H group on the coordinated bridging ligand. The pK[sub a] values reflect the metal oxidation states, M(II) and M(III). The pK[sub a] values of the mixed-valence dinuclear complexes are quite close to those of each M(II) and M(III) component, which suggests that mixed-valence complexes bridged by the protonated ligand bpbimH[sub 2] exhibit the intervalence (IT) band at 7300 cm[sup [minus]1] for M = Ru and at 9100 cm[sup [minus]1] for M = Os, respectively. When the bridging ligand is deprotonated, this IT band is shifted to lower energy at 5880 cm[sup [minus]1] for M = Ru and 7700 cm[sup [minus]1] for M = Os and intensified. The degree of metal-metal interaction of the deprotonated dinuclear complexes becomes 4-6 times larger than that of the protonated complexes. This proton-induced change of metal-metal interaction can be rationalized by change of HOMO energy levels on deprotonation or protonation in the bridging ligands. Thus, proton transfer in themore » bpbimH[sub 2] bridging dinuclear complexes can be utilized to serve as a trigger signal for switching the metal-metal interaction.« less

PatentDOI
TL;DR: A process for producing a refractory material having the form TB o, e.g. zirconium nitride (ZrN), is described in this paper.
Abstract: A process for producing a refractory material having the form TB o , e.g. zirconium nitride (ZrN), includes a first step of mixing a first salt having the form TX n , e.g. zirconium tetrachloride (ZrCl 4 ) and a second salt having the form A m B, e.g. lithium nitride (Li 3 N) in a ratio of n/m in a container. The process also includes a second step of igniting the mixture of the first and second salts, e.g. ZrCl 4 and Li 3 N, whereby the refractory material, e.g. ZrN, is produced along with byproducts having forms nAX and (n/m-o)B, e.g. 4LiCl and (1/6)N 2 , respectively. The process further includes a third step of separating the refractory material from the byproducts by solvent extraction. The stoichiometric ratio of the second salt to the first salt is n/m, e.g. 4/3. T is selected from the group consisting of transition metals, e.g. zirconium, and tetrelides, i.e. carbon, silicon, germanium, tin and lead. X is selected from the halide group consisting of fluorine, chlorine, bromine and iodine. A is selected from the group consisting of alkali metals, i.e. lithium, sodium, potassium, rubidium and cesium, and alkaline earth metals, i.e. beryllium, magnesium, calcium, strontium and barium. B is a base selected from the group consisting of pnictides, i.e. nitrogen, hosphorus, arsenic, antimony and bismuth, and tetrelides, i.e. carbon, silicon, germanium, tin and lead, m and n are integers and o is a fraction, e.g. 3/3=1.

Journal ArticleDOI
TL;DR: BarBarium hexamethyldisilazide tetrahydrofuranate, Ba(N(SiMe{sub 3}){sub 2}(THF)), is synthesized from barium granules and 1,1,3,3-hexamethylldisiliazane at 25{degree}C in THF.
Abstract: Barium hexamethyldisilazide tetrahydrofuranate, Ba(N(SiMe{sub 3}){sub 2}){sub 2}(THF){sub 2} (1), is synthesized from barium granules and 1,1,1,3,3,3-hexamethyldisiliazane at 25{degree}C in THF. Gaseous ammonia is a necessary catalyst. In the solid state, the compound is a monomer containing a tetrahedral four-coordinate barium center. One of the coordinated THF molecules is removed from 1 by stripping a toluene solution of 1 to dryness in vacuo, yielding (Ba(N(SiMe{sub 3}){sub 2}){sub 2}(THF)){sub 2} (2). In the solid state, 2 is a dimer containing two bridging and two terminal hexamethyldisilamido groups. The four-coordinate, tetrahedral geometry at each barium is completed by terminal THF molecules. The solvent-free compound (Ba(N(SiMe{sub 3}){sub 2}){sub 2}){sub 2} (3) is obtained by sublimation of 1. This compound is a dimer in the solid state, with three-coordinate barium centers. Crystal data are reported for all these compounds 14 refs., 3 figs., 9 tabs.