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A two-dimensional (2D) laminar multiferroic metal-organic framework (MOF) is prepared by using esterification under hydrothermal reaction conditions. This class of materials has provided a new path for examining the potential applications of MOFs as multiferroic materials.

The synthesis of six Ru2^6+ derivatives of the form Ru(L)4(C=CC6H5)2 is presented. Its electrochemical, spectroscopic, and structural properties are also examined.

The development of cutting-edge solid-state electrolytes (SSEs) entails a deep understanding of the underlying correlation between the structure and ionic conductivity. Generally, the structure of SSEs encompasses several interconnected crystal parameters, and their collective influence on Li + transport can be challenging to discern. Here, we systematically investigate the structure-function relationship of halide spinel Li x MgCl 2+ x (2 ≥ x ≥ 1) SSEs. A nonmonotonic trend in the ionic conductivity of Li x MgCl 2+ x SSEs has been observed, with the maximum value of 8.69 × 10 -6 S cm -1 achieved at x = 1.4. The Rietveld refinement analysis, based on neutron diffraction data, has revealed that the crystal parameters including cell parameters, Li + vacancies, Debye-Waller factor, and Li-Cl bond length assume diverse roles in influencing ionic conductivity of Li x MgCl 2+ x at different stages within the range of x values. Besides, mechanistic analysis demonstrates Li + transport along three-dimensional pathways, which primarily governs the contribution to ionic conductivity of Li x MgCl 2+ x SSEs. This study has shed light on the collective influence of crystal parameters on Li + transport behaviors, providing valuable insights into the intricate relationship between the structure and ionic conductivity of SSEs.

Until now, effective blue light-emitting materials are essentially needed for the creation of white light and precise color renderings in real-world applications, but the efficiency of blue light-emitting materials has lagged far behind. Here, we present a hydrothermal method to synthesize tin-based metal halide single crystals (RbCdCl 3 :Sn 2+ and Rb 3 SnCl 7 ). Two single crystal materials with different shapes and phases can simultaneously be synthesized in the same stoichiometric ratio. Rb 3 SnCl 7 has a bulk shape, while RbCdCl 3 :Sn 2+ has a needle shape. The deep blue emission (436 nm) of RbCdCl 3 :Sn 2+ can be obtained under the optimal excitation wavelength irradiation. However, pure blue emission (460 nm) to white light can be obtained by changing the excitation wavelength in Rb 3 SnCl 7 . The refinement spectra of the electronic structures of RbCdCl 3 :Sn 2+ and Rb 3 SnCl 7 are investigated by density functional theory. It is concluded that the difference in the distribution of Cl energy states leads to the existence of Cl local defect states, which is the reason for the rich luminescence of the two single crystals. These findings provide a path for realizing single-phase broadband white-emitting materials.

A series of novel tetradentate 6/6/6 Pt(II) complexes containing an 8-phenylquinoline-benzo[ d ]imidazole-carbazole ligand was designed; the Pt(II) complexes could be synthesized by metalizing the corresponding ligand with K 2 PtCl 4 in high isolated yields of 60-90%. Experimental and theoretical studies suggested that the ligand modification of the quinoline moieties of the Pt(II) complexes could tune their electrochemical, photophysical, and excited-state properties. Notably, all the Pt(II) complexes exhibited highly electrochemical stabilities with reversible redox processes except the quasi-reversible reduction of PtYL3 . The large π-conjugation of the ligand together with increased metal-to-ligand charge-transfer ( 3 MLCT) characters in T 1 states enabled the Pt(II) complexes to show broad Gaussian-type NIR emission spectra with high photoluminescence quantum efficiencies of 1.2-1.5% and short τ of 0.8-1.5 μs in dichloromethane at room temperature. This work should provide a valuable reference for the design and development of monomer NIR emitters.

Broadband emission with a large Stokes shift is important to obtain an excellent color rendering index of the solid-state lighting device. Among low-dimensional material and perovskite-like phosphors with broadband self-trapped emission, Sn-based phosphors have attracted much attention due to their high photoluminescence quantum yield (PLQY). However, the disadvantage is that the synthesis of Sn-based phosphors needs to be performed in a glovebox. Upon photoexcitation, the broadband emission of self-trapped excitons results from exciton-phonon coupling induced by the transient distortion of the lattice. Low-dimensional material structures often promote self-trapped emission because of more vibrational degrees of freedom and easier polarization under photoexcitation. Here, zero-dimensional (0D) SnX 2 (X = Br, I) single crystals are synthesized by the solvent evaporation method in the air. SnX 2 emits blue light, broadband yellow light, and deep red light, among which SnBr 2 has the best luminescence performance. The photoluminescence quantum yield (PLQY) of SnBr 2 reaches 85% and the Stokes shift reaches 265 nm. The PL intensity of SnX 2 is linearly related to excitation power, which preliminarily indicates that the origin of SnX 2 luminescence is attributed to self-trapped emission (STE). The white light-emitting diodes (WLEDs) were fabricated using yellow-emitting SnBr 2 and blue-emitting BaMgAl 10 O 17 :Eu 2+ , which has a low correlated color temperature (3160 K) and a relatively common color rendering index (79).

For the famous functional REF 3 family, there exist two typical structures, that is, orthorhombic phase and hexagonal phase. In the present work, high pressure behaviors of the orthorhombic phase REF 3 (RE = Sm to Lu and Y) were investigated by experimental methods and first-principles calculations. The pressure-induced phase transitions of GdF 3 , TbF 3 , YbF 3, and LuF 3 were studied by using in situ photoluminescence measurements in the diamond anvil cell. At room temperature, all these four compounds follow the phase transition route from orthorhombic to hexagonal phase at 5.5-20.6 GPa. The pressure ranges of phase transition are 5.5-9.3, 8.4-11.9, 13.5-20.3, and 14.8-20.6 GPa for GdF 3 , TbF 3 , YbF 3, and LuF 3 , respectively. In combination with first-principles calculations, we infer that all orthorhombic REF 3 members from Sm-Lu and Y obey the same orthorhombic-to-hexagonal phase transition rules under high pressures. For lanthanide trifluorides, the transition pressures increase as zero pressure volumes of REF 3 in the orthorhombic phase become smaller. As the calculation results show, this is because the difference in value of energy from the two structures is larger. This work not only provides precise structural change but also benefits the understanding of two typical structures for rare-earth trifluorides, which may play a significant role in the applications of REF 3 .

A series of theoretical methods, including density functional theory, multiconfiguration molecular orbital theory, and ab initio valence bond theory, are devoted to understanding the metal-ligand bonds in M-BP (BP = biphenyl; M = Sc, Y, or La) complexes. Different from most transition metal-BP complexes, the most stable metal-biphenyl conformers are not half-sandwich but clamshell. Energy decomposition analysis results reveal that the M-BP bonds in the clamshell conformers possess extra-large orbital relaxation. According to the wave function analysis, 2-fold donations and 2-fold back-donations exist in the clamshell M-BP bonds. The back-donations from M to BP are quite strong, while donations from BP to M are quite weak. Our work improves our understanding of the metal-ligand bonds, which can be considered as the "reversed" Dewar-Chatt-Duncanson model.

Molybdenum disulfide (MoS 2 ) is intrinsically inert for the hydrogen evolution reaction (HER) in alkaline media due to its electronic structures. Herein, we tune the electronic structures of MoS 2 by a combined strategy of post-N doping coupled with the synergistic effect of Ti 3 C 2 T X . The as-prepared N-doped MoS 2 /Ti 3 C 2 T X heterostructures show remarkable alkaline HER activity with an overpotential of 225 mV at 140 mA cm -2 , which ranks the N-doped MoS 2 /Ti 3 C 2 T X heterostructures among the best MoS 2 /MXene-based electrocatalysts reported for alkaline HER. The first-principles calculations indicate that the N doping can enhance the activation of nearby S sites of MoS 2 /Ti 3 C 2 T X and thus promote the HER process. This strategy provides a promising way to develop high-efficiency MoS 2 /MXene heterostructure catalysts for alkaline HER.

In recent years, the demand for near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) has increased rapidly, leading to more and more attention being paid to the research of broad-band near-infrared phosphors. In this work, Cr 3+ -doped Ca 2 LuScGa 2 Ge 2 O 12 (CLSGG:Cr 3+ ) phosphors with broad-band NIR emission were prepared through traditional high-temperature solid-state reactions. The crystal structures of the phosphors were analyzed by X-ray diffraction (XRD) and Rietveld refinement. The photoluminescence excitation (PLE) spectra of the synthesized CLSGG:Cr 3+ phosphors exhibit a strong absorption band in the 400-500 nm region, which matches well with a blue-light-emitting chip. The photoluminescence (PL) spectra of the phosphors show broad-band emission ranging from 650 to 1100 nm with a full width at half-maximum (fwhm) of about 150 nm. At 423 K, the integrated emission intensity of CLSGG:0.02Cr 3+ is about 59% of that at room temperature. A NIR pc-LED device was fabricated by combining a mixture of as-synthesized CLSGG:0.02Cr 3+ phosphor and silicone with a 460 nm blue-light-emitting chip. Under a driving current of 100 mA, the output power of the device can achieve 1.213 mW, indicating that the as-prepared phosphors are promising for NIR pc-LED applications.

Degradation of saccharides is relevant to the design of catalytic therapeutics, the production of biofuels, inhibition of biofilms, as well as other applications in chemical biology. Herein, we report the design of multinuclear Cu complexes that enable cleavage of saccharides under physiological conditions. Reactivity studies with para -nitrophenyl ( p NP)-conjugated carbohydrates show that dinuclear Cu complexes exhibit a synergistic effect and promote faster and more robust cleavage of saccharide substrates, relative to the mononuclear Cu complex, while no further enhancement is observed for the tetranuclear Cu complex. The use of scavengers for reactive oxygen species confirms that saccharide cleavage is promoted by the formation of superoxide and hydroxyl radicals through Cu II/I redox chemistry, similar to that observed for native copper-containing lytic polysaccharide monooxygenases (LMPOs). Differences in selectivity for di- and tetranuclear Cu complexes are modest. However, these are the first reported small multinuclear Cu complexes that show selectivity and reactivity against mono- and disaccharide substrates and form a basis for further development of metalloglycosidases for applications in chemical biology.

Currently, the study of Mn 4+ -doped oxide red phosphor is a hot research topic to solve the lack of red component in phosphor-converted white-light-emitting diodes (pc-WLEDs). In this Article, we designed Gd 3+ /Nb 5+ cation substitution by Bi 3+ /Mn 4+ in Ba 2 GdNbO 6 with double-perovskite structure based on the radius and coordination of the cations through high-temperature solid-state reaction. The phase purity and microstructure of double-perovskite Ba 2 GdNbO 6 :Bi 3+ ,Mn 4+ phosphors were characterized by X-ray diffraction and scanning electron microscopy examination. The crystal structures were also determined by the Rietveld refinement, and the photoluminescence (PL) properties were systematically studied. Bi 3+ and Mn 4+ ions can be effectively doped in the Ba 2 GdNbO 6 matrix with an optical band gap of 3.94 eV. Upon 315 nm UV excitation, the Ba 2 GdNbO 6 :Bi 3+ ,Mn 4+ phosphor shows two emission bands at 464 nm from Bi 3+ and 689 nm from Mn 4+ , respectively. By the design of Bi 3+ → Mn 4+ energy transfer, systematic luminescence tuning from blue to red could be achieved because of spectral overlap between the emission spectrum of Bi 3+ and the excitation spectrum of Mn 4+ . The corresponding mechanism of the Bi 3+ → Mn 4+ energy-transfer process was investigated in detail by the fluorescence decays and PL spectra. The red emission intensity of Mn 4+ has been greatly improved by Bi 3+ → Mn 4+ energy transfer. Moreover, the phonon vibration and zero phonon line of Mn 4+ were studied through temperature-dependent PL. Finally, a WLED was fabricated using a 460 nm blue chip with a yellow YAG:Ce 3+ phosphor and a red Ba 2 GdNbO 6 :0.01Bi 3+ ,0.01Mn 4+ phosphor, which has a low correlated color temperature (3550 K) and a high color rendering index (89.6). The above results imply that the improved red emission phosphors have a potential application in warm pc-WLED lighting.

A cobalt triphenylcorrole (CorCo) was covalently bonded to graphene oxide (GO), and the resulting product, represented as GO-CorCo, was characterized by UV-vis, FT-IR, and micro-Raman spectroscopy as well as by HRTEM, TGA, XRD, XPS, and AFM. The electrocatalytic activity of GO-CorCo toward the oxygen reduction reaction (ORR) was then examined in air-saturated 0.1 M KOH and 0.5 M H 2 SO 4 solutions by cyclic voltammetry and linear sweep voltammetry using a rotating disk electrode and/or a rotating ring-disk electrode. An overall 4-electron reduction of O 2 is obtained in alkaline media while under acidic conditions a 2-electron process is seen. The ORR results thus indicate that covalently bonded GO-CoCor can be used as a selective catalyst for either the 2- or 4-electron reduction of oxygen, the prevailing reaction depending upon the acidity of the solution.

A weakly fluorescent complex derived from a binaphthol-benzimidazole ligand was designed and synthesized for hydrogen sulfide at different pH conditions. It was demonstrated that the probe showed the same reactivity to various hydrogen sulfide species in a broad range of pH values to generate highly fluorescent product through a displacement reaction mechanism, whereas the product's fluorescence spectrum exhibited a hypsochromic shift of ∼73 nm (2393 cm(-1)) as pH increased from neutral to basic, which can be used for distinguishing the various species of hydrogen sulfide. This turn-on fluorescence probe was highly selective and sensitive to hydrogen sulfide with a detection limit of 0.11 μM. It was then applied for evaluating the total content of sulfide (including hydrogen sulfide, hydrosulfide, and sulfide) as well as for the visual detection of gaseous H2S in air using a simple test paper strip.

Eu2PQC6 has been developed to detect Al(3+) by monitoring the quenching of the europium-based emission, with the lowest detection limit of ∼32 pM and the quantitative detection range to 150 μM. Eu2PQC6 is the first ever example that the europium(III) complex serves as an Al(3+) fluorescent sensor based on "competition-displacement" mode.

The planar NNN-pincer complexes [M(II)(pyN(2)(Me2))(OH)](1-) (M(II) = Ni, Cu) fix CO(2) in η(1)-OCO(2)H complexes; results for the copper system are described. Mn(II), Fe(II), Co(II), and Zn(II) behave differently, forming [M(II)(pyN(2)(Me2))(2)](2-) with N(4)O(2) coordination. Incorporation of the Ni(II) pincer into binucleating macrocycle 2 containing a triamino M(II) locus connected by two 1,3-biphenylene groups affords proximal Ni(II) and M(II) sites for investigation of the synthesis, structure, and reactivity of Ni-X-M bridge units. This ligand structure is taken as a reference for variations in M(II) atoms and binding sites and bridges X = OH(-) and CN(-) to produce additional members of the macrocyclic family with improved properties. Macrocycle 2 with a 22-membered ring is shown to bind M(II) = Mn, Fe, and Cu with hydroxo bridges. Introduction of the 4-Bu(i)O group (macrocycle 3) improves the solubility of neutral complexes such as those with Ni(II)-OH-Cu(II) and Ni(II)-CN-Fe(II) bridges. Syntheses of macrocycle 5 with a 7-Me-[12]aneSN(3) and macrocycle 6 with a 1,8-Me(2)-[14]aneN(4) M(II) binding site are described together with hydoxo-bridged Ni/Cu and cyano-bridged Ni/Fe complexes. This work was motivated by the presence of a Ni···(HO)-Fe bridge grouping in a reactive state of carbon monoxide dehydrogenase. Attempted decrease in Ni-(OH)-M distances (3.70-3.87 Å) to smaller values observed in the enzyme by use of macrocycle 4 having 1,2-biphenylene connectors led to a mononuclear octahedral Ni(II) complex. Bridge structural units are summarized, and the structures of 14 macrocyclic complexes including 8 with bridges are described.

The planar complexes [Ni(II)(pyN(2)(R2))(OH)](-), containing a terminal hydroxo group, are readily prepared from N,N'-(2,6-C(6)H(3)R(2))-2,6-pyridinedicarboxamidate(2-) tridentate pincer ligands (R(4)N)(OH), and Ni(OTf)(2). These complexes react cleanly and completely with carbon dioxide in DMF solution in a process of CO(2) fixation with formation of the bicarbonate product complexes [Ni(II)(pyN(2)(R2))(HCO(3))](-) having η(1)-OCO(2)H ligation. Fixation reactions follow second-order kinetics (rate = k(2)'[Ni(II)-OH][CO(2)]) with negative activation entropies (-17 to -28 eu). Reactions were monitored by growth and decay of metal-to-ligand charge-transfer (MLCT) bands at 350-450 nm. The rate order R = Me > macro > Et > Pr(i) > Bu(i) > Ph at 298 K (macro = macrocylic pincer ligand) reflects increasing steric hindrance at the reactive site. The inherent highly reactive nature of these complexes follows from k(2)' ≈ 10(6) M(-1) s(-1) for the R = Me system that is attenuated by only 100-fold in the R = Ph complex. A reaction mechanism is proposed based on computation of the enthalpic reaction profile for the R = Pr(i) system by DFT methods. The R = Et, Pr(i), and Bu(i) systems display biphasic kinetics in which the initial fast process is followed by a slower first order process currently of uncertain origin.

The strongly near-IR-active mixed-valence diruthenium complex [Ru(2)TIEDCl(4)]Cl, where TIED = tetraiminoethylenedimacrocycle, was found to be a highly active catalyst for air oxidation of HS(-) forming polysulfide species and H(2)O(2). The reaction provides a convenient method for the detection of the HS(-) generation rate of a H(2)S donor of medical importance., (© 2011 American Chemical Society)

Pyridine-2,6-dimethanethiolate and pyridine-2,6-dithiocarboxylate form sparingly soluble Ni(II) pincer complexes formulated as [Ni(pdmt)](2) and [Ni(pdtc)](2), respectively, with two Ni-(mu(2)-S)-Ni bridges. In acetonitrile reaction systems, the latter undergoes the facile bridge cleavage reactions [Ni(pdtc)](2) + 2L(0,-) --> 2[Ni(pdtc)L](0,-) with an extensive set of nucleophiles to afford planar mononuclear products with L(-) = halide, CN, Me(3)SiO(-), RS(-) and L(0) = Et(3)P and a N-heterocyclic carbene. [Ni(pdmt)](2) is considerably less reactive toward bridge disruption. Cleavage products support several reactions of interest leading to other mononuclear species and to di- and trinuclear complexes. [Ni(pdtc)(OSiMe(3))](1-) deprotonates acetonitrile and acetone to form [Ni(pdtc)(CH(2)R)](1-) (R = CN, COMe). Reaction of [Ni(pdtc)SEt](1-) with Fe(II) yields the thiolate-bridged dimer {[Ni(pdtc)](2)(SEt)}(1-). Refluxing an acetonitrile solution of [Ni(pdtc)SH](1-) in air results in formation of trinuclear [Ni(pdtc)](3)S](2-) containing the rare unsupported Ni(3)(mu(3)-S) bridge core. Reaction of [Ni(pdtc)CN](1-) with [Fe(Me(6)tren)(OTf)](1+) forms the complex [Ni(pdtc)CNFe(Me(6)tren)](1+), the only example of a single Ni-C[triple bond]N-Fe bridge within a molecule. Structures of the various types of reaction products are presented. This work demonstrates the potential utility of bridge cleavage of polynuclear Ni(II) thiolates, an extensive family of compounds, to produce mononuclear products.

The mononuclear macrocyclic complexes [Au(I)([9]aneS2O)2]BF4 x MeCN 1a, [Au(II)([9]aneS2O)2](BF4)2 x 2 MeCN 2a, and [Au(III)([9]aneS2O)2](ClO4)6(H5O2)(H3O)2 3 ([9]aneS2O = 1-oxa-4,7-dithiacyclononane) have been prepared and structurally characterized by single crystal X-ray crystallography. The oxidation of [Au([9]aneS2O)2](+) to [Au([9]aneS2O)2](2+) involves a significant reorganization of the co-ordination sphere from a distorted tetrahedral geometry in [Au([9]aneS2O)2](+) [Au-S 2.3363(12), 2.3877(12), 2.6630(11), 2.7597(13) A] to a distorted square-planar co-ordination geometry in [Au([9]aneS2O)2](2+). The O-donors in [Au([9]aneS2O)2](2+) occupy the axial positions about the Au(II) center [Au...O = 2.718(2) A] with the S-donors occupying the equatorial plane [Au-S 2.428(8) and 2.484(8) A]. [Au([9]aneS2O)2](3+) shows a co-ordination sphere similar to that of [Au([9]aneS2O)2](2+) but with significantly shorter axial Au...O interactions [2.688(2) A] and equatorial Au-S bond lengths [2.340(4) and 2.355(6) A]. The cyclic voltammogram of 1 in MeCN (0.2 M NBu4PF6, 253 K) at a scan rate of 100 mV s(-1) shows an oxidation process at E(p)(a) = +0.74 V and a reduction process at E(p)(c) = +0.41 V versus Fc(+)/Fc assigned to the two-electron Au(III/I) couple and a second reduction process at E(p)(c) = +0.19 V assigned to the Au(I/0) couple. This electrochemical assignment is confirmed by coulometric and UV-vis spectroelectrochemical measurements. Multifrequency EPR studies of the mononuclear Au(II) complex [Au([9]aneS2O)2](2+) in a fluid solution at X-band and as frozen solutions at L-, S-, X-, K-, and Q-band reveal g(iso) = 2.0182 and A(iso) = -44 x 10(-4) cm(-1); g(xx) = 2.010, g(yy) = 2.006, g(zz) = 2.037; A(xx) = -47 x 10(-4) cm(-1), A(yy) = -47 x 10(-4) cm(-1), A(zz) = -47 x 10(-4) cm(-1); P(xx) = -18 x 10(-4) cm(-1), P(yy) = -10 x 10(-4) cm(-1), and P(zz) = 28 x 10(-4) cm(-1). DFT calculations predict a singly occupied molecular orbital (SOMO) with 27.2% Au 5d(xy) character, consistent with the upper limit derived from the uncertainties in the (197)Au hyperfine parameters. Comparison with [Au([9]aneS3)2](2+) reveals that the nuclear quadrupole parameters, P(ii) (i = x, y, z) are very sensitive to the nature of the Au(II) co-ordination sphere in these macrocyclic complexes. The observed geometries and bond lengths for the cations [Au([9]aneS2O)2](+/2+/3+) reflect the preferred stereochemistries of d(10), d(9), and d(8) metal ions, respectively, with the higher oxidation state centers being generated at higher anodic potentials compared to the related complexes [Au([9]aneS3)2](+/2+/3+).

A reaction system consisting of terephthalic acid, NaOH, inorganic Mn(II) or Mn(III) salt, and salicylidene alkylimine resulted in dinuclear manganese complexes (salpn)(2)Mn(2)(mu-phth)(CH(3)OH)(2) (1, salpn = N,N'-1,3-propylene-bis(salicylideneiminato); phth = terephthalate dianion), (salen)(2)Mn(2)(mu-phth)(CH(3)OH)(2) (2, salen = N,N'-ethylene-bis(salicylideneiminato)), (salen)(2)Mn(2)(mu-phth)(CH(3)OH)(H(2)O) (3), and (salen)(2)Mn(2)(mu-phth) (4), while the absence of NaOH in the reaction led to a mononuclear Mn complex (salph)Mn(CH(3)OH)(NO(3)) (5, salph = N,N'-1,2-phenylene-bis(salicylideneiminato)). In addition, a trinuclear mixed metal complex H[Mn(2)Na(salpn)(2)(mu-OAc)(2)(H(2)O)(2)](OAc)(2) (6) was obtained from the reaction system by using maleic acid instead of terephthalic acid. Five-coordinate Mn ions were found in 4 giving rise to an intermolecular interaction and constructing a one-dimensional linear structure. Antiferromagnetic exchange interactions were observed for 1-3, and a total ferromagnetic exchange of 4 was considered to stem from intermolecular magnetic coupling. (1)H NMR signals of phenolate ring and alkylene (or phenylene) backbone of the diamine are similar to those reported in the literature, and the phth protons are at -2.3 to -10.1 ppm. Studies on structure, bond valence sum analysis, and magnetic properties indicate the oxidation states of the Mn ions in 6 to be +3, which are also indicated by ESR spectra in dual mode. Ferromagnetic exchange interaction between the Mn(III) sites was observed with J = 1.74 cm(-1). A quasireversible redox pair at -0.29V/-0.12V has been assigned to the redox of Mn(2)(III)/Mn(III)Mn(II), implying the intactness of the complex backbone in solution.

Molecules of the type mer-M(H)3(NO)L2 [M = Ru (1), Os (2); L = PR3] are characterized on the basis of 1H NMR T1min values and IR spectra as pseudo-octahedral trihydrides significantly distorted by compression of the cis H-M-H angles to approximately 75 degrees. The distortion, uncharacteristic of six-coordinate d6 complexes, is rationalized with DFT (B3LYP) calculations as being driven by increased H-to-M sigma donation and by the exceptional pi-accepting ability of linear NO+. In both 1 and 2, hydrides undergo intramolecular site exchange with delta HHH++(1) = 10-11 kcal/mol and delta HHH++(2) = 16-20 kcal/mol, depending on L, whereas for mer-Ru(H)3(NO)(PtBu2Me)2 (1b), moderate exchange couplings (up to 77 Hz) are featured in the low-temperature 1H NMR spectra, in addition to chemical exchange. On the basis of experimental and theoretical results, a dihydrogen intermediate is suggested to mediate hydride site exchange in 1. The cis H-M-H distortion shortens the tunneling path for the exchanging hydrides in 1, thereby increasing the tunneling rate; diminishes the "conflict" between trans hydrides in the mer geometry; and decreases the nucleophilicity of the hydrides. The generality of the observed structural distortion and its dependence on the ligand environment in late transition metal tri- and dihydrides are discussed. A less reducing metal center is generally characterized by greater distortion.

Reactions of the component elements at 1050 degrees C and then 400 degrees C in Ta containers generate the black title phase in good yield. Single-crystal X-ray characterization (monoclinic, C2/c, Z = 4, a = 15.101(3) Å, b = 6.6925(9) Å, c = 14.389(3) Å, beta = 118.61(1) degrees ) revealed a novel infinite chain structure in which approximately D(2)(d)() units are made from tetrahedra of disordered Tl + 3Sn that are bridged at opposite edges by four-bonded Au atoms, and vice versa. The chains have the electron count of a classical Zintl phase in which all elements are four-bonded. The MOs of the chain fragment and the band structure of the chains are described. A relatively large gap appears to arise because of the similar energies of Au 6s and the TlSn(3)(4)(-) units.

Reactions of the Rb-Tl-As system near 500 degrees C in tantalum containers always lead to the formation of Rb(5)TaAs(4)Tl(2) because of reactions with the container wall. On-stoichiometry reactions of these three elements in Ta, or of the four components in SiO(2), afford the pure compound. Rb(5)TaAs(4)Tl(2) crystallizes in orthorhombic system, space group Pnma (No. 62), Z = 4, a = 19.196(5) Å, b = 11.104(3) Å, c = 7.894(4) Å. The isostructural K(5)TaAs(4)Tl(2) also exists. The main structural feature is the closed-shell polyanion TaAs(4)Tl(2)(5)(-) which can be viewed as the result of a reaction of a TaAs(4)(7)(-) tetrahedron with two Tl(+) so as to bridge opposed edges of the former. EHMO calculations for TaAs(4)(7)(-) (T(d)()) and TaAs(4)Tl(2)(5)(-) (D(2)(h)()) demonstrate the character of the bonding of Tl s and p to the electron-rich As. Two kinds of multicentered bonds are evident: pi( perpendicular) and sigma plus pi( parallel) in the plane of the TlAs(2)Ta portions and 5c-4e d-p bonds within TaAs(4).

Reaction of H(2) with RuCl(2)(CO)L(2) (L = P(t)()Bu(2)Me) in benzene forms RuHCl(CO)L(2) and HCl. The latter reacts with RuCl(2)(CO)L(2) to give [LH][Ru(2)Cl(5)(CO)(2)L(2)] and [LH]Cl. The Ru(2)Cl(5)(CO)(2)L(2)(-) ion is detected (NMR) as several isomers, and is shown by X-ray diffraction to have a face-shared bioctahedral structure: LCl(OC)Ru(&mgr;-Cl)(3)Ru(CO)ClL(-). The loss of phosphine from Ru(II) is triggered by electrophilic attack, but not directly on P or on the Ru-P bond. It is shown (low-temperature NMR studies) that HCl reacts with RuHCl(CO)L(2) to give initially RuCl(2)(H(2))(CO)L(2), in which H(2) is trans to Cl. From this study, and also direct observation of the reaction of HCl with RuCl(2)(CO)L(2) to produce Ru(2)Cl(5)(CO)(2)L(2)(-), the Brønsted basicity of chloride in RuCl(2)(CO)L(2) is established. This accounts for its reaction with PhC(2)H and NEt(3) to give Ru(C(2)Ph)Cl(CO)L(2). Crystallographic data (-173 degrees C) for [P(t)()Bu(2)MeH][Ru(2)Cl(5)(CO)(2)(P(t)()Bu(2)Me)(2)]: a = 16.418(2)Å, b = 12.578(2)Å, c = 20.044(3)Å, beta = 103.38(1) degrees with Z = 4 in space group P2(1)/a.