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We herein report our investigations on the use of a tris-silanol-decorated polyoxotungstate, [SbW

The mixed molybdenum/tungsten Keggin-type polyoxometalate (POM) hybrid (TBA)

A new hexanuclear plutonium cluster has been stabilized in aqueous media with acetate ligands. To probe the formation of such a complex structure, visible-near infrared (vis-NIR) absorption spectroscopy, extended X-ray absorption fine structure (EXAFS) spectroscopy, and density functional theory (DFT) were combined. The presence of Pu

Uranyl binitrate complexes have a particular interest in the nuclear industry, especially in the reprocessing of spent nuclear fuel. The modified PUREX extraction process is designed to extract U(VI) in the form of UO

International audience; Various preparations of the neutral radical [CpNi(dddt)] complex (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate) were investigated with CpNi sources, [Cp2Ni], [Cp2Ni](BF4), [CpNi(CO)]2, and [CpNi(cod)](BF4), and dithiolene transfer sources, O=C(dddt), the naked dithiolate (dddt(2-)), the monoanion of square-planar Ni dithiolene complex (NBu4)[Ni(dddt)2], and the neutral complex [Ni(dddt)2]. The reaction of [CpNi(cod)](BF4) with (NBu4)[Ni(dddt)2] gave the highest yield for the preparation of [CpNi(dddt)] (86%). [CpNi(ddds)] (ddds = 5,6-dihydro-1,4-dithiin-2,3-diselenolate), [CpNi(dsdt)] (dsdt = 5,6-dihydro-1,4-diselenin-2,3-dithiolate), [CpNi(bdt)] (bdt = 1,2-benzenedithiolate), and [CpNi(bds)] (bds = 1,2-benzenediselenolate) were synthesized by the reactions of [Cp2Ni] with the corresponding neutral Ni dithiolene complexes [Ni(ddds)2]2, [Ni(dsdt)2], [Ni(bdt)2], and [Ni(bds)2], respectively. The five, formally Ni(III), radical complexes oxidize and reduce reversibly. They exhibit, in the neutral state, a strong absorption in the NIR region, from 1000 nm in the dddt/ddds/dsdt series to 720 nm in the bdt/bds series with epsilon values between 2500 and 5000 M(-1) cm(-1). The molecular and solid state structures of the five complexes were determined by X-ray structure analyses. [CpNi(dddt)] and [CpNi(ddds)] are isostructural, while [CpNi(dsdt)] exhibits a closely related structure. Similarly, [CpNi(bdt)] and [CpNi(bds)] are also isostructural. Correlations between structural data and magnetic measurements show the presence of alternated spin chains in [CpNi(dddt)], [CpNi(ddds)], and [CpNi(dsdt)], while a remarkably strong antiferromagnetic interaction in [CpNi(bdt)] and [CpNi(bds)] is attributed to a Cp...Cp face-to-face sigma overlap, an original feature in organometallic radical complexes.

The reduction products of two diphosphaalkenes (1 and 2) and a bis(diphosphene) (3) containing sterically encumbered ligands and corresponding to the general formulas Ar-X=Y-Ar'-Y=X-Ar, have been investigated by EPR spectroscopy. Due to steric constraints in these molecules, at least one of the dihedral angles between the CXYC plane and either the Ar plane or the Ar' plane is largely nonzero and, hence, discourages conformations that are optimal for maximal conjugation of P=X (or P=Y) and aromatic pi systems. Comparison of the experimental hyperfine couplings with those calculated by DFT on model systems containing no cumbersome substituents bound to the aromatic rings shows that addition of an electron to the nonplanar neutral systems causes the X=Y-Ar'-Y=X moiety to become planar. In contrast to 1 and 2, 3 can be reduced to relatively stable dianion. Surprisingly the two-electron reduction product of 3 is paramagnetic. Interpretation of its EPR spectra, in the light of DFT calculations on model dianions, shows that in [3](2)(-) the plane of the Ar' ring is perpendicular to the CXYC planes. Due to interplay between steric and electronic preferences, the Ar-X=Y-Ar'-Y=X-Ar array for 3 is therefore dependent upon its redox state and acts as a "molecular switch".

The synthesis and structural characterization of a samarium-dinitrogen complex supported by a calix[4]arene ligand in which the N-N bond distance has been stretched to 1.611(16) Angstrom are described. The central mu(3)-eta(2):eta(2):eta(2)-hydrazido tetraanion formed is bonded to three Sm(III) centers with an overall butterfly-type arrangement.

The existence of new compounds is often postulated by solid state chemists by replacing an ion in the crystal structure of a known compound by a chemically similar ion. In this work, we present how this new compound discovery process through ionic substitutions can be formulated in a mathematical framework. We propose a probabilistic model assessing the likelihood for ionic species to substitute for each other while retaining the crystal structure. This model is trained on an experimental database of crystal structures, and can be used to quantitatively suggest novel compounds and their structures. The predictive power of the model is demonstrated using cross-validation on quaternary ionic compounds. The different substitution rules embedded in the model are analyzed and compared to some of the traditional rules used by solid state chemists to propose new compounds (e.g., ionic size).

The complexes [tmtaa]Ti=O and [tmtaa]Ti=S have highly reactive Ti=O and Ti=S linkages and are demonstrated to undergo a number of new addition and cycloaddition reactions, and complex 1 has been found to be involved in a series of acid-base equilibria. Treatment with excess RO 3 SCF 3 (R=H, Me, SiMc 3 ) yields the bis(triflate) complex [tmtaa]Ti(O 3 SCF 3 ) 2 .

The compounds Fe[sub 3]([mu][sub 3]-PBu[sup t])([mu][sub 3]-NR)(CO)[sub 9] (R = Ph (2a), Et (2b)), which are the first examples of clusters possessing both capping imido and phosphinidene ligands, have been prepared in good yield by the photochemical reaction of the corresponding H[sub 2]Fe[sub 3]([mu][sub 3]-NR)(CO)[sub 9] cluster with Bu[sup t]PCl[sub 2]. Cluster 2a has been crystallographically characterized: C[sub 19]H[sub 14]NO[sub 9]PFe[sub 3], orthorhombic,. Like Fe[sub 3]([mu][sub 3]-NPh)[sub 2](CO)[sub 9], the cluster consists of an isosceles triangle of iron atoms with two Fe-Fe bonds and with capping phosphinidene and imido ligands above and below the metal triangle. Both clusters have been observed to react with alkynes to give a variety of products, the most interesting of which is the binuclear compound Fe[sub 2]([mu][sub 2],[eta][sup 3]-PhNC(Ph) [double bond] C(Ph)PBu[sup t])([mu][sub 2],[eta][sup 4]PhC [double bond] C(Ph)C(Ph) [double bond] CPh)(CO)[sub 4] (3) which results from the reaction of PhC [triple bond] C(Ph)PBu[sup t] ligand formed by insertion of the alkyne between the phosphinidene and imido ligands and also has a ferracyclopentadiene ligand formed by coupling of two additional alkynes: C[sub 56]H[sub 44]NO[sub 4]PFe[sub 2], triclinic.

The μ-oxo complexes [Cp 2 M=O-M'(PPh 3 ) 2 (CO)] + (M=Mo,W;M'=Rh,Ir) have been prepared by solvent displacement from [M'(CO)(PPh 3 ) 2 (CH 3 CN)] + by the oxo ligand of Cp 2 M=O. Crystallographic analysis of the salt [Cp 2 Mo=O−Rh-(PPh 3 ) 2 (CO)][BF 4 ]•1/2C 3 H 6 O•1/2C 5 H 12 [P2 1 /c

Oxidation of the square planar Rh(I) complex [Rh(SPS(Me))(PPh3)] (SPS(Me) = 1-methyl-1-P-2.6-bis(diphenylphosphinosulfide)-3,5-(bisphenyl)-phosphinine) (1) based on mixed SPS-pincer ligand with hexachloroethane yielded the Rh(III) dichloride complex [Rh(SPS(Me))(PPh3)Cl2] (2), which was structurally characterized. The homoleptic Rh(III) complex [Rh(SPS(Me))2][Cl] (4) was obtained via the stoichiometric reaction of SPS(Me) anion (3) with [Rh(tht)3Cl3] (tht = tetrahydrothiophene). Complex 4, which was characterized by X-ray diffraction, was also studied by cyclic voltammetry. Complex 4 can be reversibly reduced at E = -1.16 V (vs SCE) to give the neutral 19-electron Rh(II) complex [Rh(SPS(Me))2] (5). Accordingly, complex 5 could be synthesized via chemical reduction of 4 with zinc dust. EPR spectra of complex 5 were obtained after electrochemical or chemical reduction of 4 in THF or CH2Cl2. Hyperfine interaction with two equivalent 31P nuclei was observed in liquid solution, while an additional coupling with a spin 1/2 nucleus, probably 103Rh, was detected in frozen solution. The 31P couplings are consistent with DFT calculations that predict a drastic increase in the axial P-S bond lengths when reducing (SPS(Me))2Rh(III). In the reduced complex, the unpaired electron is mainly localized in a rhodium d(z2) orbital, consistent with the g-anisotropy measured at 100 K.

Two new, "user-friendly" derivatives of triptycene containing AsH(2) and SiH(3) fragments were synthesized. Both solids are crystalline, air-stable compounds characterized by elevated melting points and resistance toward moisture. The highly reactive As-H and Si-H bonds are protected by the presence of the surrounding phenylene hydrogen atoms, which ensure a remarkable kinetic stabilization of these primary hydrides. After X-ray irradiation of a single crystal of triptycenesilane, a persistent silyl radical was trapped and characterized.

The reaction of HCoRu3(CO)13 with H2 in refluxing hexane gives the new cluster H3CoRu3(CO)12 in 75% yield. Infrared and H(1) NMR spectra indicate that the cluster exists in two isomeric forms. The structure of one isomer has determined by single-crystal x-ray diffraction. The CoRu3 core of the molecule defines a distorted tetrahedron with three carbonyls terminally bound to each metal atom. The hydride ligands were located by difference Fourier techniques and bridge the three Ru-Ru bonds. The overall symmetry of the cluster is approximately C sub 3v. Spectral evidence indicates that the second isomer contains a bridging CO ligand and three non-equivalent hydrogens. The interconversion of the two isomers and the various hydrogen exchange processes have been monitored by H(1) NMR spectroscopy and the exchange mechanisms are discussed.

Reaction of ((Ph/sub 3/P)/sub 2/N) (HFe(CO)/sub 4/) with Ru/sub 3/(CO)/sub 12/ and Fe/sub 2/Ru(CO)/sub 12/ in refluxing THF gives the new clusters ((Ph/sub 3/P)/sub 2/N)(HFeRu/sub 3/(CO)/sub 13/) and ((Ph/sub 3/P)/sub 2/N)(HFe/sub 2/Ru/sub 2/(CO)/sub 13/) in 47% and 4% yields, respectively. ((Ph/sub 3/P)/sub 2/N)-(HFeRu/sub 3/(CO)/sub 13/) has been characterized by its spectroscopic properties and by complete single-crystal x-ray and neutron diffraction studies. ((Ph/sub 3/P)/sub 2/N)(HFeRu/sub 3/(CO)/sub 13/) crystallizes in the space group P1 with Z = 2. Unit cell dimensions from the neutron diffraction study at 15 K are a = 15.053 (2) A, b = 9.073 (1) A, c = 18.992 (3) A, ..cap alpha.. = 104.75 (2)/sup 0/, ..beta.. = 109.58 (2)/sup 0/, and ..gamma.. = 86.95 (2)/sup 0/. The structure was refined to R(F/sup 2/) = 0.052 and R(wF/sup 2/) = 0.057 with measured intensities of 8354 independent reflections. The (HFeRu/sub 3/(CO)/sub 13/)/sup -/ anion has a closed pseudotetrahedral structure with each Ru bearing three terminal carbonyls. Two terminal carbonyls are attached to Fe with two additional carbonyls occupying semibridging positions between Fe and two Ru atoms. The hydride ligand symmetrically bridges one of the Ru-Ru bonds. ((Ph/sub 3/P)/sub 2/N)(HFe/sub 2/Ru/sub 2/(CO)/sub 13/) has also been characterized crystallographically.more » It crystallizes in the space group P1 with Z=2. The unit cell dimensions at room temperature are a= 14.955 (2) A, b = 18.144 (3) A, c = 9.290 (2) A, ..cap alpha.. = 101.54 (2)/sup 0/, ..beta.. = 95.03 (4)/sup 0/, and ..gamma.. = 84.04 (3)/sup 0/. The structure was solved and refined to R(F) = 0.056 and R(wF) = 0.042 for 5886 independent reflections with I greater than or equal to 3.0sigma(I). The structure of (HFe/sub 2/Ru/sub 2/(CO)/sub 13/)/sup -/ is similar to that of (HFeRu/sub 3/(CO)/sub 13/)/sup -/ except that the anion possesses a full-bridging CO between the two Fe atoms and no semibridging CO's.« less

The new clusters HCoRu3 (CO)13, HCoRu2Os(CO)13, HCoRuOs2(CO)13, and HCoOs3(CO)13 have been synthesized by allowing K(Co(CO)4) to react with Ru3(CO)12, Ru2Os(CO)12, RuOs2(CO)12, and Os3(CO)12, respectively, followed by protonation. Reaction of KCo(CO)4 with Fe3(CO)12, Fe2Ru(CO)12, and FeRu2(CO)12 followed by acidification did not lead to the desired hydrido mixed-metal clusters but instead to various other products. Reaction of (PPN) (Co(CO)4) (PPN= (Ph3P)2N) with Fe3(CO)12 and Ru3(CO)12 without subsequent acidification gave the salts (PPN) (CoFe3(CO)13) and (PPN) (CoRu3(CO)13). The latter was structurally characterized by single crystal X-ray. It crystallizes in the space group P1 with Z= 2 and unit cell dimensions a = 9.783(5) Angstrons, b = 14.768(5) Angstrons, c = 18.675(5) Angstons, Alpha = 110.39(3) deg, Beta = 99.02(4) deg, Gamma = 91.44(4) deg, and V = 2489(4) Angstrons 3. Diffraction data (0 deg 20 50 deg) were collectedwith an Enraf-Nonius CAD4 automated diffractometer, using graphite-monochromat ized MoK Alpha radiation, and the structure was refined to R = 0.036 and RW = 0.044 for 6150 independent reflections with I greater than or equal to 3.0 sigma (I). The molecule contains a tetrahedral CoRu3 core with each Ru atom bonded to three terminal carbonyls, the Co atom bonded to one terminal carbonyl, and with a carbonyl ligand bridging each of the three Co-Ru bonds. Analogous reactions of (PPN) (Co(CO)4) with Fe2Ru(CO)12 and FeRu2(CO)12 gave products formulated as (PPN) (CoFe2Ru(CO)13) and (PPN) (CoFeRu2(CO)13) but these salts were not obtained pure. (Author)

Reaction of the mixed-metal tetranuclear clusters H/sub 2/FeRu/sub 3/(CO)/sub 13/, H/sub 2/FeRu/sub 2/Os(CO)/sub 13/, H/sub 2/FeRuOs/sub 2/(CO)/sub 13/, HCoRu/sub 3/(CO)/sub 13/, H/sub 2/FeRu/sub 3/(CO)/sub 12/L (L = PMe/sub 2/Ph, PPh/sub 3/), (HFeRu/sub 3/(CO)/sub 13/)/sup -/, and (CoRu/sub 3/(CO)/sub 13/)/sup -/ with CO under relatively mild conditions (P(CO) = 1 atm, t = 0-80/sup 0/C) results in their fragmentation to give trimeric and monomeric products. The fragmentation reactions are generally quite selective: H/sub 2/FeRu/sub 2/Os(CO)/sub 13/, for example, reacts with CO to give Ru/sub 2/Os(CO)/sub 12/, Fe(CO)/sub 5/, and H/sub 2/ with no RuOs/sub 2/(CO)/sub 12/, FeRu/sub 2/(CO)/sub 12/, or FeRuOs(CO)/sub 12/ detected in the product mixture. This reaction and the corresponding fragmentation of H/sub 2/FeRuOs/sub 2/(CO)/sub 13/ provide a convenient means of separating and isolating the mixed-metal trimers Ru/sub 2/Os(CO)/sub 12/ and RuOs/sub 2/(CO)/sub 12/. The reactivity of a particular cluster toward CO is greatly dependent on its metal composition and/or its structure. For example, H/sub 2/FeRu/sub 2/Os(CO)/sub 13/ reacts slowly over a period of several days while the breakdown of HCoRu/sub 3/(CO)/sub 13/ is complete within 1h. The tetrahydride clusters H/sub 4/FeRu/sub 3/(CO)/sub 12/ and H/sub 4/Ru/sub 4/(CO)/sub 12/ first react with CO to displace H/sub 2/ and formmore » the corresponding dihydride clusters which subsequently fragment under the reaction conditions. Kinetic measurements indicate that the fragmentation of H/sub 2/FeRu/sub 3/(CO)/sub 13/ to produceRu/sub 3/(CO)/sub 12/, Fe(CO)/sub 5/, and H/sub 2/ proceeds largely by a second-order, (CO)-dependent path with activation parameters ..delta..H/sup 0/ not equal to = 20.0 +- 2.0 kcal/mol and ..delta..S/sup 0/ not equal to = -25.4 +- 5.8 cal/(mol K). Likewise, fragmentation of H/sub 2/Ru/sub 4/(CO)/sub 13/ to form Ru/sub 3/(CO)/sub 12/, Ru(CO)/sub 5/, and H/sub 2/ proceeds via a second-order, (CO)-dependent path with ..delta..H/sup 0/ not equal to = 12.5 +- 0.5 kcal/mol and ..delta..S/sup 0/ not equal to = -36.6 +- 1.6 cal/(mol K).« less