Reduction of [Mo2O2(mu-S)(2)(H2O)(6)](2+) with [Re(CO)(5)Cl] in 2 M HCl at 160 degrees C produces condensation of binuclear clusters with the formation of the{Mo-3(mu(3)-S)(mu-O)(3)}(4+) species, which was isolated and structurally characterized as {[Mo-3(mu(3)-S)(mu(2)-O)(3)(H2O)(6)Cl-3](2)CB[6]}Cl-2 center dot 10.88H(2)O (2) (CB[6] = C36H36N24O12) and [Mo-3(mu(3)-S)(mu(2)-O)(3)(acac)(3)(py)(3)] PF6 center dot 2C(6)H(5)CH(3) (3). Reaction of [Mo-3(mu(3)-S)(mu(2)-S)(mu(2)-O)(2)(H2O)(9)](4+) with [Re(CO)(5)Cl] produces cuboidal cluster [Mo-4(mu(3)-S)(4)(H2O)(12)](5+). (C) 2011 Published by Elsevier B.V.

The hydrosilylation reaction between silanes and various carbonyl substrates such as aldehyde, ketone, ester, and carbonate has been catalyzed by Re(CO)(5)Cl UV photolysis. Kinetic studies have shown that the reaction is favored for the least sterically hindered silanes with aldehydes followed by aliphatic ketones. The IR spectrum of the rhenium carbonyl dimer HRe2(CO)(9)(SiR3) has been recorded in the reaction mixture. This complex is believed to be the resting state of the active catalyst Re(CO)(4)SiR3, which could be released upon photactivation. A catalytic mechanism involving this species has been proposed and shown to be thermodynamically feasible using computational studies. In addition, the relative hydrosilylation rates among the various carbonyl substrates can be explained using the same mechanism.

Anisotropic structures, nanoneedles, and nanospindles of rare earth hydroxychloride (RE(OH)(2)Cl) and oxychloride (REOCl) (rare earth=Eu and Th) were synthesized. The rare earth hydroxychloride nanostructures were formed via a thermally assisted hydrolysis of the rare-earth sesquioxide nanocrystals. The morphological evolution of the nanostructures was studied using high-resolution transmission electron microscopy and scanning electron microscopy, while the structural evolution was investigated using X-ray diffraction techniques. The thermal stability of the rare earth hydroxychlorides was investigated using thermogravimetric analysis. The rare earth oxychloride nanospindles were synthesized via a simple heat-treatment of rare earth hydroxychloride nanospindles.

The structure of the [Au(Dien)Cl](2)[Re(4)Te(4)(CN)(12)]center dot 5H(2)O compound prepared in an aqueous medium by the reaction of a gold(III) complex [Au(Dien)Cl]Cl(2) with a tetranuclear tetrahedral tellurocyanide cluster complex of rhenium K(4)[Re(4)Te(4)(CN)(12)]center dot 5H(2)O is determined by single crystal X-ray diffraction.

Here, we report density functional calculations of the electronic structure and nuclear independent chemical shift (NICS) values of the Re(3)Cl(9) and Re(3)Br(9) clusters including scalar and spin-orbit relativistic effects (ADF + ZORA + SO). Our calculations have shown that both the clusters exhibit aromaticity and that spin-orbit effects decreases aromaticity due to the fact that the 5d(3/2) spinors are mostly occupied and are more contracted than the scalar 5d orbitals. (C) 2008 Elsevier B.V. All rights reserved.

A new rhenium(I) complex, Re(CO)(3)Cl(aeip) [where aeip = 2-(anthracen-9-yl)-1-lethyl-imidazo[4,5-f][1,10]phenanthroline], was designed and synthesized as a luminescence probe under visible light excitation at 410 nm for detection of singlet oxygen ((1)O(2)) in aqueous media. The new complex can specifically react with (1)O(2) in neutral and alkaline media, which results in remarkable luminescence enhancements, with 8- and 18.7-fold increases in the luminescence quantum yields, respectively. The visible light excitation may allow the complex to be useful for biosystems. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Highlights • Non-photochemical synthesis of Re(diimine)(CO)2(L)Cl compounds (L = P(OEt)3, PMe3) • Effect of ligand variation (displaying scope of synthetic method) • Characterization of three new Re(diimine)(CO)2(L)Cl compounds • X-ray crystallographic structure ReCl(4,4′-di-tertbutyl-2,2′-bipyridine)(CO)2P(OEt)3 Abstract The synthesis and characterization of a series of compounds of the type Re(diimine)(CO)2(L)Cl (where L = P(OEt)3, PMe3) is reported. The non-photochemical ligand substitution (non-PLS) utilizes the trans-labilizing effect of phosphorus ligands to facilitate carbonyl replacement. The non-PLS pathway leads to good yields (> 60%) of single isomer products, comparing favorably to the lower yield, mixed isomer products of analogous PLS pathways. The substitution of a carbonyl group by a phosphine/phosphite ligands shifts absorption further into the visible region without diminishing molar absorptivity. The synthesis presented provides a general facile ligand substitution pathway for related light-sensitive neutral rhenium/manganese carbonyl halide compounds. Graphical abstract A generalized reaction is shown for the primary products of the paper. A light bulb is crossed-out to indicate that the synthesis is non-photochemical in nature. Below this are sample UV/vis spectra (highlighting the bathochromic shift upon ligand substitution).

The geometry of Re(2)Cl(8)(2-) has been optimized for the eclipsed (D(4h)) equilibrium conformation and for the staggered (D(4d)) conformation at BP86/TZ2P. The nature of the Re-Re bond which has a formal bond order four has been studied with an energy decomposition analysis (EDA). The EDA investigation indicates that the contribution of the b(2)(delta(xy)) orbitals to the Re-Re bond in the (1)A(1g)(delta(2)delta*(0)) ground state is negligibly small. The vertical excitation of one and two electrons from the bonding delta orbital into the anti-bonding delta* orbitals yielding the singly and doubly excited states (1)A(1g)(delta(1)delta*(1)) and (1)A(1g)(delta(0)delta*(2)) gives a destabilization of 17.5 and 36.1 kcal/mol, respectively, which is nearly the same as the total excitation energies. The preference for the D(4h) geometry with eclipsing Re-Cl bonds is explained in terms of hyperconjugation rather than delta bonding. This is supported by the calculation of the triply bonded Re(2)Cl(8) which also has an eclipsed energy minimum structure. The calculations also suggest that the Re-Re triple bond in Re(2)Cl(8) is stronger than the Re-Re quadruple bond in Re(2)Cl(8)(2-). A negligible contribution of the delta orbital to the metal-metal bond strength is also calculated for Os(2)Cl(8) which is isoelectronic with Re(2)Cl(8)(2-).

Excitation by high-energy light, such as that of 313 nm wavelength, induces a photochemical ligand substitution (PLS) reaction of fac-[Re(bpy)(CO)(3)Cl] (1a) to give the solvento complexes (OC-6-34)- and (OC-6-44)-[Re(bpy)(CO)(2)(MeCN)Cl] (2 and 3) in good yields. The disappearance quantum yield of 1a was 0.01 +/- 0.001 at 313 nm. The products were isolated, and X-ray crystallographic analysis was successfully performed for 2. Time-resolved IR measurements clearly indicated that the CO ligand dissociates with subpicosecond rates after excitation, leading to vibrationally hot photoproducts, which relax within 50-100 ps. Detailed studies of the reaction mechanism show that the PLS reaction of 1a does not proceed via the lowest vibrational level in the (MLCT)-M-3 excited state. The PLS reaction gives 2 and (OC-6-24)-[Re(bpy)(CO)(2)(MeCN)Cl] (5) as primary products, and one of the products, 5, isomerizes to 3. This type of PLS reaction is more general, occurring in various fac-rhenium(I) diimine tricarbonyl complexes such as fac-[Re(X(2)bpy)(CO)(3)Cl] (X(2)bpy = 4,4'-X-2-bpy; X = MeO, NH2, CF3), fac-[Re(bpy)(CO)(3)(pyridine)](+), and fac-[Re(bpy)(CO)(3)(MeCN)](+). The stable photoproducts (OC-6-44)- and (OC-6-43)-[Re(bpy)(CO)(2)(MeCN)(pyridine)](+) and (OC-6-32)- and (OC-6-33)-[Re(bpy)(CO)(2)(MeCN)(2)](+) were isolated. The PLS reaction of rhenium tricarbonyl-diimine complexes is therefore applicable as a general synthetic method for novel dicarbonyls.

The Re-Re bonding in anion Re(2)Cl(8)((2-)), generally considered as a paradigm of quadruple metal-metal bond, was analyzed using the formalism of the analysis of domain averaged Fermi holes. The results of our analysis straightforwardly confirms the dramatic reduction of bond order of Re-Re bond reported in recent theoretical studies and provides simple chemically appealing description of the peculiarity of this bond bond. The analysis shows that although the Re-Re bond indeed involves four electron pairs, the bonding contribution of one of them, namely the one corresponding to delta bond is partially cancelled due to fractional population of antibonding delta* orbital.

A small-scale experimental braided river system has been reproduced. This experiment shows that: (i) destabilisation of the river occurs through sediment feeding; (ii) for constant input fluxes of mass, transfer by the river evolves towards a steady state in which mass fluxes at each end of the reach remain constant although instable braiding remains inside the box; (iii) instability of the braided river remains both when the system aggrades or degrades.

The annual average of the groundwater levels in 27 wells is connected to the annual climate impact on the groundwater resources in the Bani river basin (Douna, 101 600 square kilometers). The groundwater level variations are well correlated to rainfall variations, and for the lowest levels of groundwater, the runoff stops in the dry season at Douna. The humid year of 1994 caused a rise in the groundwater level to the same level as 1981, together with a reduction of the depletion coefficient. But the runoff is still weak, showing that the rainfall–runoff relationships are modified over the long term.