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Studies are reported regarding the use of Mn(CN)(bpy)(CO)3 (1) as a catalyst for CO2 reduction employing [Ru(dmb)3]2+ as a photosensitizer in mixtures of dry N,N-dimethylformamide-triethanolamine (N,N-DMF-TEOA) or acetonitrile-TEOA (MeCN-TEOA) with 1-benzyl-1,4-dihydronicotinamide as a sacrificial reductant. Irradiation with 470 nm light for up to 15 h yields both CO and HCO2H with maximum turnover numbers (TONs) as high as 21 and 127, respectively, with product preference dependent on the solvent. Further data suggests that upon single electron reduction this catalyst avoids the formation of a Mn-Mn dimer and instead undergoes a disproportionation reaction, which requires 2 equiv of [Mn(CN)(bpy)(CO)3]·- to generate 1 equiv each of the active catalyst [Mn(bpy)(CO)3]- and the starting compound 1. Additional characterization by cyclic voltammetry (CV) and infrared spectroelectrochemistry (IR-SEC) indicates that the stability of the singly reduced [Mn(CN)(bpy)(CO)3]·- differs slightly in theN,N-DMF-TEOA solvent system compared to the MeCN-TEOA system. This contributes to the observed selectivities for HCO2H vs CO production. [ABSTRACT FROM AUTHOR]

The redox series [Irn(NHx)(PNP)] (n = II–IV, x = 3–0; PNP = N(CHCHPtBu2)2) was examined with respect to electron, proton, and hydrogen atom transfer steps. The experimental and computational results suggest that the IrIII imido species [Ir(NH)(PNP)] is not stable but undergoes disproportionation to the respective IrII amido and IrIV nitrido species. N–H bond strengths are estimated upon reaction with hydrogen atom transfer reagents to rationalize this observation and are used to discuss the reactivity of these compounds toward E–H bond activation. [ABSTRACT FROM AUTHOR]

The arene-solvated indium(I) species [In(C7H8)3][CHB11Cl11] (1) and [In(C6H5Br)1.5][CHB11Cl11] (2) were obtained by a redox reaction involving the silver salt Ag[CHB11Cl11] and indium powder at 80 °C in a toluene or bromobenzene solution. These thermally stable compounds react with triphenylphosphine and the N-heterocyclic carbene 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene under reduction of indium(I) to indium metal and oxidation of the ligands to phosphonium and imidazolium cations contrary to the more commonly observed disproportionation reactions. The presence of 2 equiv of carbene led to deprotonation of the anion to give the dianion [CB11Cl11]2-. Interactions of In+ with soft donor ligands such as phosphines, olefins, alkynes, and aromatics are weak, and a crystalline solid was only obtained with the nonvolatile phosphinoacetylene Mes2PCCPh (Mes = 2,4,6-Me3C6H2). The structure of this compound displays In···C interactions involving the triple bond and the π system of one mesityl group but no In···P contact. Solutions of 2 in fluorobenzene also showed moderate activity as the catalyst for intramolecular hydroamination of primary and secondary aminopentenes. The new compounds were characterized by multinuclear NMR spectroscopy and X-ray diffraction for compounds 1, 2, and 4-6. [ABSTRACT FROM AUTHOR]

A stable trigonal bipyramidal copper(III) complex, [PPN][Cu(TMSPS3)Cl] (1, wherein PPN represents bis(triphenylphosphine)iminium), was synthesized from CuCl2/PPNCl via intramolecular copper(II) disproportionation. Under ambient conditions, the axial chloride of 1 is exchangeable in solution thus making 1 serve as an intermediate to prepare trigonal bipyramidal copper(III) derivatives, e.g., [PPN][Cu(TMSPS3)(N3)] (2) and [Cu(TMSPS3)(DABCO)] (3). Diamagnetic complexes 1-3 were fully characterized by X-ray crystallography, NMR, UV-vis, and Cu K-edge absorption spectroscopy. A series of UV-vis titrations were performed to investigate the relative ligand affinity toward the [Cu(TMSPS3)] moiety, verifying the 1:1 binding equilibrium between various ligands. Compared to known copper(III) compounds, Cu K-edge absorptions of 1-3 possess lower pre-edge energy and higher shakedown transition energy, which, respectively, attribute to the electron donation from TMSPS33- ligand and their trigonal ligand field. [ABSTRACT FROM AUTHOR]

A three-coordinate cobalt species, IPrCoCl{N(SiMe3)2} [1; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene], was synthesized by the reaction of {IPrCoCl2}2 with NaN(SiMe3)2. Compound 1 is a useful starting material for low-coordinate (IPr)Co species. 1 reacts with 2,6-di-tert-butyl-4-methylphenol (BHT-H) via aminolysis of the Co–N bond to generate a three-coordinate phenoxide complex, IPrCoCl(O-2,6-tBu2-4-MeC6H2) (2). The reaction of 1 with 2,6-diisopropylaniline (NH2DIPP) generates IPrCoCl(NHDIPP) (4), which undergoes disproportionation to form a mixture of 4, {IPrCoCl2}2, and IPrCo(NHDIPP)2 (3). The same product mixture is formed by the reaction of 1 with Li[NH(DIPP)], which unexpectedly proceeds by amide exchange. Compound 3 was synthesized independently by the reaction of {IPrCoCl2}2 with 4 equiv of Li[NH(DIPP)]. The reaction of 1 with the bulkier lithium 2,6-dimesitylanilide (LiNHDMP) also proceeds by amide exchange to generate IPrCoCl(NHDMP) (5), which is stable toward disproportionation. Compounds 1 and 2 exhibit trigonal-planar geometries at cobalt in the solid state. The solid-state structure of 3 also contains a trigonal-planar cobalt center and exhibits close Co---H contacts involving the methine hydrogen atoms of the NH(DIPP) groups in the axial positions. The solid-state structure of 5 features an interaction between cobalt and a flanking aryl group of the anilide ligand, resulting in pyramidalization of the cobalt center. [ABSTRACT FROM AUTHOR]

A novel quadruple perovskite oxide CeCu3Fe4O12 has been synthesized under high-pressure and high-temperature conditions of 15 GPa and 1473 K. 57Fe Mössbauer spectroscopy displays a charge disproportionation transition of 4Fe3.5+ → 3Fe3+ + Fe5+ below ~270 K, whereas hard X-ray photoemission and soft X-ray absorption spectroscopy measurements confirm that the Ce and Cu valences are retained at approximately +4 and +2, respectively, over the entire temperature range measured. Electron and X-ray diffraction studies reveal that the body-centered cubic symmetry (space group Im3, No. 204) is retained at temperatures as low as 100 K, indicating the absence of any types of charge-ordering in the charge-disproportionated CeCu3Fe4O12 phase. The magnetic susceptibility and neutron powder diffraction data illustrate that the antiferromagnetic ordering of Fe ions is predominant in the charge-disproportionated CeCu3Fe4O12 phase. These findings suggest that CeCu3Fe4O12 undergoes a new type of electronic phase in the ACu3Fe4O12 series and that the melting of the charge-ordering in CeCu3Fe4O12 is caused by the substantial decrease in the Fe valence and the resulting large deviation from the ideal abundance ratio of Fe3+:Fe5+ = 1:1 for rock-salt-type charge-ordering. [ABSTRACT FROM AUTHOR]

The crystal structures of intermetallic phases offer a wealth of geometrical features (helices, multishelled dusters, and host--guest motifs) whose formation has yet to be explained or predicted by chemical theory. A recently developed extension of the acid-base concept to metallic systems, the μ3-acidity model, provides an avenue for developing this understanding for intermetallics formed from transition metals. In this Article, we illustrate how this approach can be used to understand one of the most striking geometrical entities to emerge in intermetallic chemistry, the Mackay cluster of icosahedral quasicrystals. We present μ3-acidity analyses, based on DFT-calibrated Hückel calculations, for a series of Sc-Ir intermetallics: ScIr (CsCl-type), Sc2Ir (Ti2Ni-type), Sc11Ir4, and the Mackay cluster containing phases Sc57Ir13 and Sc44Ir7. We begin by illustrating that a μ3-acidity model correctly predicts that each of these phases is stable relative to disproportionation into their neighboring compounds when a common set of Hiickel parameters and d-orbital occupancies is used. Next, we explain these results by developing a relationship between the distance distribution of homoatomic contacts within an atom's coordination sphere and the μ3-neutralization it experiences. For a given average homoatomic distance, the role of heteroatomic contacts is higher when the distribution of homoatomic contacts is narrower. This effect is key to the strength of the acid-base neutralization of the Scrichl phases, where the Sc atoms find a scarcity of Ir atoms from which to obtain neutralization. Under these circumstances, Sc-lr contacts should be maximized, whereas the number and distance variations of the Sc-Sc contacts should be minimized. These expectations are borne out by the observed crystal structures. In particular, the Mackay clusters of Sc57Irl3 and Sc44Ir7, in which a central Ir atom is icosahedrally coordinated by a pentagonal dodecahedral array of face-sharing Sc oetahedra, represent a natural way of merging the competing needs for enhancing Sc-Ir interactions while diminishing those between the Sc atoms. [ABSTRACT FROM AUTHOR]

Two complex layered uranyl borates, K10[(UO2)16(B2O5)2(BO3)6O8]̣7H2O (1) and K13[(UO2)15(UO4)-(B2O5)2(BO3)6(OH)2Os]̣H2O (2), were isolated from supercritical water reactions. Within these compounds, borate exists only as BO3 unite and is found as either isolated BO3 triangles or B2Os dimers, the latter being formed from corner sharing of two BO3 units. These anions, along with oxide and hydroxide, bridge between uranyl centers to create the complex layers in these compounds. U(VI) cations are found within uranyl, UO22+ units, that are bound by four or five oxygen atoms to create tetragonal and pentagonal bipyramidal environments. The most striking feature in this system is found in 2, where a [UO4(OH)2] unit exists that contains U(V) within a tetraoxo core with trans hydroxide anions; therefore, this compound is a mixed-valent U(VI)/U(V) borate. The presence of a 5f¹ uranium site within 2 leads to unusual optical properties. [ABSTRACT FROM AUTHOR]

Reaction of [Ni(NO)(bipy)(Me2phen)][PF6] with 1 equiv of nitric oxide (NO) in CH2Cl2 results in the formation of N2O and [{(Me2phen)Ni(NO)}2(µ-η¹-N:η¹-O)-NO2)][PF6] (3), along with the known complex, [Ni(bipy)3][PF6]2 (4). The isolation of complex 3, which contains a nitrite ligand, demonstrates that the reaction of [Ni(NO)(bipy)(Me2phen)][PF6] with exogenous NO results in NO disproportionation and not NO reduction. Complex 3 could also be accessed by reaction of [Ni(NO)(Me2phen)][PF6] (5) with (Me2phen)Ni(NO)(NO2) (7) in good yield. Complexes 3, 5, and 7 were fully characterized, including analysis by X-ray crystallography in the case of 3 and 7. Furthermore, addition of 0.5 equiv of bipy to [Ni(NO)(bipy)][PF6] results in formation of the hyponitrite complex, [{(bipy)Ni(η2-O2N2)}η¹:η¹-N,N-{Ni(NO)(bipy)}2][PF6]2 (9), in modest yield. Importantly, the hyponitrite ligand in 9 is thought to form via coupling of two NO- ligands and not by coupling of a nucleophilic nitrosyl ligand (NO-) with an electrophilic nitrosyl ligand (NO+). X-ray crystallography reveals that complex 9 features a new binding mode of the cis-hyponitrite ligand. [ABSTRACT FROM AUTHOR]

Unusual electronic phase transitions in the A-site ordered perovskites LnCu3Fe4O12 (Ln: trivalent lanthanide ion) are investigated. All LnCu3Fe4O12 compounds are in identical valence states of Ln3+Cu2+³Fe3.75+4O12 at high temperature. LnCu3Fe4O12 with larger Ln ions (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb) show an intersite charge transfer transition (3Cu2+ + 4Fe3.75+ → 3Cu3+ + 4Fe3+) in which the transition temperature decreases from 360 to 240 K with decreasing Ln ion size. In contrast, LnCu3Fe4O12 with smaller Ln ions (Ln = Dy, Ho, Er, Tm Yb, Lu) transform into a charge-disproportionated (8Fe3.75+ → 5Fe3+ + 3Fe5+) and charge-ordered phase below 250-260 K. The former series exhibits metal-to-insulator, antiferromagnetic, and isostructural volume expansion transitions simultaneously with intersite charge transfer. The latter shows metal-to-semiconductor, ferrimagnetic, and structural phase transitions simultaneously with charge disproportionation. Bond valence calculation reveals that the metal-oxygen bond strains in these compounds are classified into two types: overbonding or compression stress (underbonding or tensile stress) in the Ln-O (Fe-O) bond is dominant in the former series, while the opposite stresses or bond strains are found in the latter. Intersite charge transfer transition temperatures are strongly dependent upon the global instability indices that represent the structural instability calculated from the bond valence sum, whereas the charge disproportionation occurs at almost identical temperatures, regardless of the magnitude of structural instability. These findings provide a new aspect of the structure-property relationship in transition metal oxides and enable precise control of electronic states by bond strains. [ABSTRACT FROM AUTHOR]

The bis-bidentate ligand, obtained from Schiff base condensation of RR-1,2-cyclohexanediamine and 8-naphthylmethoxyquinoline-2-carbaldehyde (L-L), forms with [CuI(MeCN)4]ClO4 a double strand helicate complex, made especially stable by the presence of four definite interstrand π-π interactions involving a quinoline subunit and a naphthylmethoxy substituent of the two strands. The [CuI2(L-L)2]2+ complex, which does not decompose even on excess addition of either L-L or CuI, undergoes a two electron oxidation in MeCN, through two one-electron fully reversible steps, separated by 260 mV, as shown by cyclic voltammetry (CV) studies. The high stability of the mixed valence complex [CuICuII(L-L)2]3+ with respect to disproportionation to [CuI2(L-L)2]2+ and [CuII2(L-L)2]4+ is essentially due to a favorable electrostatic term. CuII forms with L-L a stable species, with a 1:1 stoichiometric ratio, but, in the absence of crystallographic data, it was impossible to assess whether it is of mono- or dinuclear nature. However, CV studies on an MeCN solution containing equimolar amounts of CuII and L-L showed the presence in the reduction scan of two fully reversible waves, separated by about 250 mV, which indicated the presence in solution of a dicopper(II) double strand helicate complex, [CuII2(L-L)2]4+. This work demonstrates that additional interstrand π-π interactions can favor the formation of unusually stable dicopper(I) and dicopper(II) helicate complexes. [ABSTRACT FROM AUTHOR]

Drawing the analogy to BaBiO3, we investigate via ab initio electronic structure calculations potential new superconductors of the type AT1X3 with A = Rb and Cs and X = F, CI, and Br, with a particular emphasis on RbTlCl3. On the basis of chemical reasoning, supported by the calculations, we show that Tl-based perovskites have structural and charge instabilities driven by the lone pair effect, similar to the case of BaBi03, effectively becoming A2T1+T13+X6. We find that upon hole doping of RbTlCl3, structures without T1+ and T13+ charge disproportionation become more stable, although the ideal cubic perovskite, often viewed as the best host for superconductivity, should not be the most stable phase in the system. The known superconductor (Sr,K)BiO3 and hole doped RbTlCl3, predicted to be most stable in the same tetragonal structure, display highly analogous calculated electronic band structures. [ABSTRACT FROM AUTHOR]

Interaction of NO (15NO) with amorphous layers of Ru(II) carbonyl porphyrin (Ru(TPP)(CO), TPP2- = meso-tetraphenylporphyrinato dianion) was monitored by FTIR spectroscopy from 80 K to room temperature. An intermediate spectrally characterized at very low temperatures (110 K) with ν(CO) at 2001 cm-1 and ν(NO) at 1810 cm-1 (1777 cm-1 for 15NO isotopomer) was readily assigned to the mixed carbonyl--nitrosyl complex Ru(TPP)(CO)(NO), which is the logical precursor to CO labilization. Remarkably, Ru(TPP)-mediated disproportionation of NO is seen even at 110 K, an indication of how facile this reaction is. By varying the quantity of supplied NO, it was also demonstrated that the key intermediate responsible for NO disproportionation is the dinitrosyl complex Ru(TPP)(NO)2, supporting the conclusion previously made from solution experiments. [ABSTRACT FROM AUTHOR]

Reaction of alkali metals (Li, Na, K) with mesityldichlorophosphane (MesPClv Mes = 2,4,6-Me3C6H2) in ethereal solvents leads to formation of the corresponding mesitylphosphanides MPHMes in good purity and yield. 31P NMR spectroscopic studies in deuterated solvents strongly support a mechanism of the reaction that involves protonation/ disproportionation steps in which the solvent is the only possible proton source. Li(thf)(tmeda)PHMes (l), [Na(tmeda)(//-PHMes)]∞ (2), and [K(pmdeta)(μ-PHMes)]2 (3) (tmeda = N,N,N',N'-tetramethylethylenediamine, pmdeta = N,N,N';N",N"-pentamethyldiethylenetriamine) were obtained; in the solid state, 2 forms zigzag chains while 3 is a dimeric compound. [ABSTRACT FROM AUTHOR]

The complex Ruu(NH3)2(o-benzoquinonediimine)Cl2 under-goes a reversible apparent acid/base reaction, although it has no obvious basic lone pairs. The reaction is a proton-assisted disproportionation yielding an oxidant ([RuIII(NH3)2(o-benzoquinonediimine)Cl3]+) and a reductant ([Ru",(NH3)2(o-phenylenediamine)a2]+). These species were characterized by electrochemistry, ultraviolet--visible light (UV-vis), vibrational (infrared (IR) and Raman), mass and electron paramagnetic resonance (EPR) spectroscopy, and X-ray structural analysis. The reaction is shown to be dewnhill from an isodesmic calculation. Three different isosbestic interconversions of die parent and product species are demonstrated. The electronic structures of these species were analyzed, and their optical spectra assigned, using density functional theory (DFT) and time-dependent DFT. This disproportionation of a noninnocent ligand complex may be relevant to the application of noninnocent ligands in organometallic catalysis and in the biological milieu. [ABSTRACT FROM AUTHOR]

The disproportionation reaction of the subvalent metastable halide SnCl proved to be a powerful synthetic method for the synthesis of metalloid cluster compounds of tin. Now we present the synthesis and structural characterization of the anionic metalloid cluster compound [Sn9[Si(SiMe3)3]2]2-3 where the oxidation state of the tin atoms is zero. Quantum chemical calculations as well as Mössbauer spectroscopic investigations show that three different kinds of tin atoms are present within the cluster core. Compound 3 is highly reactive as shown by NMR investigations, thus being a good starting material for further ongoing research on the reactivity of such partly shielded metalloid cluster compounds. [ABSTRACT FROM AUTHOR]

Syntheses of the intramoleculariy coordinated organotin(I) compound {4-t-Bu-2,6-[P(0)(0-t-Pf)2]2C6,H2Sn}2 (2), which crystallized in two different pseudopolymorphs 2 and 2-C7H8, of the diorganostannylene {4-t-Bu-2,6-[P(0)(0-i-Pr)2]2C6H2}2Sn (3) and of the organotin(II) acetate 4-t-Bu-2,6-[P(0)(0-i-Pr)2]2C6H2SnOAc (4) are reported. The compounds were characterized by multinuclear NMR, IR (3 and 4), UV--vis spectroscopy (2), electrospray ionization mass spectrometry (3 and 4), and single-crystal X-ray diffiraction analyses. Density functional theory calculations on compound 2 revealed the stabilizing effect of the intramolecular P=0 → Sn coordination. [ABSTRACT FROM AUTHOR]

High-pressure structural phase transitions in NaNiF3 and NaCoF3 were investigated by conducting in situ synchrotron powder X-ray diffiaction experiments using a diamond anvil cell. The perovskite phases (GdFeO3 type) started to transform into postperovskite phases (CaIrO3, type) at about 11 -- 14 GPa, even at room temperature. The transition pressure is much lower than those of oxide perovskites. The anisotropic compression behavior led to heavily tilted octahedra that triggered the transition. Unlike oxide postperovskites, fiuoropostperovskites remained after decompression to 1 atm. The postperovskite phase in NaCoF3 broke down into a mixture of unknown phases after laser heating above 26 GPa, and the phases changed into amorphous ones when the pressure was released. High-pressure and high-temperature experiments using a tnultianvil apparatus were also conducted to elucidate the phase relations in in NaCoF3. Elemental analysis of the recovered amorphous samples indicated that the NaCoF3 postperovskite disproportionated into two phases. This kind of disproportionation was not evident in NaNiF3 even after laser heating at 54 GPa. In contrast to the single postpostperovskite phase reported in NaMgF3, such a postpostperovskite phase was not found in the present compounds. [ABSTRACT FROM AUTHOR]

The disproportionation reaction of the subvalent metastable halide SnBr proved to be a powerful synthetic method for the synthesis of metalloid cluster compounds of tin. Hence, the neutral metalloid cluster compound Sn10[Si(SiMe3)3]6 (3) was synthesized from the reaction of SnBr with LiSi(SiMe3)3. In the course of the reaction anionic clusters might also be present, and we now present the first anionic cluster compound {Sn8E[Si(SiMe3)3]3}- (E = Si, Sn), where one position in the cluster core is occupied by a silicon or a tin atom, giving further insight into structural variations of E9 cages in metalloid group 14 cluster compounds. [ABSTRACT FROM AUTHOR]