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The solid solution Sn24AsxP19.3-xI8 in the range of compositions x from 0 to 16 was synthesized. The crystal structure was refined for seven compositions of the solid solution at —100 °C. All samples crystallize in the cubic space group Pm3 n with the unit cell parameters a = 10.9358(2)—11.1495(2) A and belong to the clathrate-I structure type. The distribution of the phosphorus and arsenic atoms over two independent crystallographic positions within the clathrate framework was analyzed. The difference in the structure of the substituted clathrates with the cationic and anionic clathrate frameworks is considered.

The reactivity of a heterobimetallic Bi−Rh trifluoroacetate paddlewheel complex toward an aromatic substrate has been tested in a solvent-free environment. As a result of the gas phase codeposition...

The crystal structure of Sn3P4, a long-known tin phosphide, has been determined. It crystallizes in the trigonal space group R3m with unit-cell parameters a = 4.4315(1) A and c = 28.393(1) A (Z = 3). The crystal structure of Sn3P4 is disordered. It consists of alternating layers of phosphorus and tin atoms that are combined into five-layer blocks and propagate along the c-axis. The major structural feature is the disordered orientation of the P24– dumbbells, which link the tin atoms. The latter possess two types of coordination. One third of the tin atoms reside inside the block and are octahedrally coordinated by phosphorus atoms. The rest of the tin atoms confine the block and possess a [3 + 3] environment made up of three close phosphorus neighbors and three rather distant (3.4 A) tin atoms of the adjacent block. The coordination of the tin atoms is confirmed by 119Sn Mossbauer spectroscopy. The electron diffraction and high-resolution electron microscopy data reveal ordered regions at the microscopic...

The photoelectron spectrum and a density functional computational analysis of the first p-block paddlewheel complex, Bi2(tfa)4, where tfa = (O2CCF3)−, are reported. The photoelectron spectrum of Bi2(tfa)4 contains an ionization band between the region of metal-based ionizations and the region of overlapping ligand ionizations that is not seen in the photoelectron spectra of d-block paddlewheel complexes. This additional ionization arises from an a1g symmetry combination of the tfa ligand orbitals that is directed for σ bonding with the metals, and the unusual energy of this ionization follows from the different interaction of this orbital with the valence s and p orbitals of Bi compared to the valence d orbitals of transition metals. There is significant mixing between the Bi–Bi σ bond and this a1g M–L σ orbital. This observation led to a re-examination of the ionization differences between Mo2(tfa)4 and W2(tfa)4, where the metal–metal σ and π ionizations are overlapping for the Mo2 molecule but a separate and sharp σ ionization is observed for the W2 molecule. The coalescing of the σ and π bond ionizations of Mo2(tfa)4 is due to greater ligand orbital character in the Mo–Mo σ bond (∼7%) versus the W–W σ bond (∼1%).

Orange-red Ag4I(PO4) crystallizes in the monoclinic system, space group P21/m (No. 11), with the unit cell dimensions a=9.0874(6) A, b=6.8809(5) A, c=11.1260(7) A, β=109.450(1)°, and Z=4. The crystal structure is fully ordered; it comprises the silver–iodine three-dimensional positively charged framework hosting the tetrahedral PO43− guest anions. The framework features high coordination numbers for iodine and manifold Ag–Ag bonds ranging from 3.01 to 3.46 A. The Ag–Ag interaction is bonding, it involves silver 4d and 5s orbitals lying, together with the orbitals of iodine, just below the Fermi level. Though the orbitals of silver and iodine define the conducting properties of the title compound, the interaction between the framework and the guest anions is also important and is responsive to the number of the silver atoms surrounding the PO43− tetrahedra. Ag4I(PO4) melts incongruently at 591 K and produces a mixture of the silver phosphate and an amorphous phase upon cooling. Pure Ag4I(PO4) is a poor conductor with a room temperature conductivity of 3×10−6 S m−1. The discrepancies between the properties observed here and those reported previously in the literature are discussed.

New synthetic approach for the preparation of heterometallic β-diketonates has been developed. Three manganese-containing diketonates, InMn(hfac)3 (1), CdMn2(hfac)6 (2), and Hg2Mn2(hfac)6 (3), have been isolated in quantitative yields by employing the solid state redox reaction of Mn(hfac)3 with transition and main group metals. The heterometallic molecules are built on Lewis acid–base interactions between diketonate oxygens of the [Mn(hfac)3]− groups and “naked” metal centers that appear in the form of In+, Cd2+, and Hg 2 2+ cations. Compounds 1–3 have been shown to retain a heterometallic structure upon sublimation–deposition procedure as well as in solutions of non-coordinating solvents.

New double mercury silver phosphide iodide Hg12Ag41P88I41 (1) was synthesized and its crystal structure was established. Compound 1 crystallizes in the cubic system. The characteristic feature of the crystal structure 1 is the presence of the anionic cage clusters P113−, which have been previously found in alkali metal compounds only. The well-ordered P113− clusters form a system of polyhedra, which encapsulate various disordered α-AgI-type fragments.

Mixed-metal molybdenum(II)/rhodium(II) tetra(trifluoroacetate) of the composition [(MoRh)(O2CCF3)4] has been obtained from the gas-phase reaction between volatile carboxylates, [Mo2(O2CCF3)4] and [Rh2(O2CCF3)4]. This is an interesting system for which a single-crystal X-ray investigation fails to provide an unambiguous evidence of whether the product consists of the initial homometallic or newly formed heterometallic paddlewheel units. In the solid-state structure both metal atoms occupy the same crystallographic position, while the M-M and M-O distances are averaged with respect to the parent homometallic compounds. Nevertheless, the results of mass-spectrometric and magnetic measurements clearly indicate that the title bimetallic carboxylate contains a statistical mixture of homometallic dimolybdenum and dirhodium units. The product can be considered as a result of cocrystallization of isomorphous paddlewheel molecules.

More than 40 new 4- to 12-membered ring heterocycles containing various combinations of Group 14 elements (Si and Sn) and Group 16 elements (S, Se, and Te) have been synthesized and fully characterized. Synthesis of these small-ring as well as medium-ring (mesocyclic) heterocycles from α, ω-dihalides was facilitated by the presence of gem-dialkylsilyl and gem-dialkylstannyl groups in the precursors. Solid-state conformations of the new ring systems have been determined by X-ray crystallography. Oxidation of mixed S(Se, Te)/Si eight-membered ring mesocycles as well as 1,5-dithia-, 1,5-diselena-, and 1,5-ditelluracyclooctane with NOPF6 gave dications, which can be characterized by NMR. On treatment with nucleophiles, mesocyclic dications or the corresponding radical cations underwent ring contraction to give five- or six-membered ring heterocycles. The ionization energies of the above conformationally constrained β-disilanyl sulfides and selenides were determined by photoelectron spectroscopy. These ionization energies reflect substantial (0.53--0.75 eV) orbital destabilizations. The basis for these destabilizations was investigated by theoretical calculations, which reveal geometry-dependent interaction between sulfur or selenium lone pair orbitals and σ-orbitals, especially Si–Si σ-orbitals. These results suggest facile redox chemistry for these compounds and significantly extend the concept of σ-stabilization of electron-deficient centers. © 2007 Wiley Periodicals, Inc. 18:509–515, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20333

More than 40 new 4- to 12-membered ring heterocycles containing various combinations of Group 14 and 16 elements Si, Sn, S, Se, and Te have been synthesized and fully characterized. Synthesis of these small-ring as well as medium-ring (mesocyclic) heterocycles from alpha,omega-dihalides is facilitated by the presence of gem-dialkylsilyl and gem-dialkylstannyl groups in the precursors. Conformations of several of the new ring systems in the solid state have been determined by X-ray crystal structure analysis. Oxidation of mixed S(Se, Te)/Si eight-membered ring mesocycles with NOPF6 or Br2 gives dications or a bicyclic dibromide, respectively, which can be characterized by NMR methods. On treatment with nucleophiles, mesocyclic dications, or the corresponding radical cations undergo ring contraction, giving five- or six-membered ring heterocycles. Photolysis of a S/Se four-membered ring heterocycle gives selenoformaldehyde, trapped in 80% yield with 2,3-dimethyl-1,3-butadiene.

The crystal structures of new sodium vanadylphosphate, Na4.35VO(PO4)2 ( a = 15.4450 ( 11 ) A , b = 14.7690 ( 10 ) A , c = 6.9870 ( 5 ) A , Z = 8 , S.G. Ibam), and new (γ-) modification of Na4VO(PO4)2 ( a = 15.4455 ( 15 ) A , b = 14.8433 ( 10 ) A , c = 7.0081 ( 5 ) A , Z = 8 , S.G. Pbc21) have been investigated by X-ray single-crystal diffraction. Both structures contain isolated infinite chains of the corner-sharing VO6 octahedra. The octahedra within the chains are additionally linked to each other by the tetrahedral PO4 groups. Sodium atoms are situated in the positions between the chains. Depending on the conditions of synthesis, the number of sodium atoms in the unit cell of the Na4+xVO(PO4)2 compounds may vary resulting in a change of the oxidation state of vanadium atoms and a change of their coordination environment. In Na4.35VO(PO4)2 vanadium atoms have almost regular octahedral coordination with six close V–O separations and all chains in the structure are equivalent. The crystal structure of γ-Na4VO(PO4)2 contains two non-equivalent chain types: the first one is similar to that found in Na4.35VO(PO4)2 whereas the second one contains VO6 octahedra with the short vanadyl bonds. The charge re-distribution was supposed in the new γ-modification of Na4VO(PO4)2 where the V4+δ and V4−δ cations orderly occupy octahedral positions in different chains. The origin of this phenomena is discussed.

The title compound, [Ru2(O2CCF3)4] (1), has been obtained without any exogenous ligands and crystallized by deposition from the gas phase at 170 C. Its crystal structure has been determined for the first time to confirm an infinite chain motif built on axial Ru···O interactions of the diruthenium(II,II) units. The X-ray diffraction studies at variable temperatures showed no phase transitions in the range of 295-100 K but revealed a significant decrease in the volume per atom from 14.2 to 13.3 Å3. This noticeable thermal compressibility effect is discussed in connection with the solid-state packing of the [Ru2(O2CCF3)4] chains. The highly electrophilic character of the diruthenium(II,II) units has been shown by the gas-phase deposition reaction of [Ru2(O2CCF3)4] with an aromatic donor substrate, namely [2.2]paracyclophane (C16H16). As a result of the above reaction, a new arene adduct [Ru2(O2CCF3)4·C16H16] (2) has been isolated in crystalline form. It has an extended one-dimensional (1D) chain structure comprised of alternating building units and based on the rare bridging mode of [2.2]paracyclophane, [Ru2(O2CCF3)4·(2-2:2-C16H16)]. The magnetic susceptibility of 1 and 2 has been measured and compared in the range of 1.8-300 K. In addition, in the course of synthesis of 1 by the carboxylate exchange reactions, a new mixed-carboxylate diruthenium(II,II) core complex [Ru2(O2CCF3)3(O2CC2H5)] (3), bearing no exogenous ligands, has also been isolated and structurally characterized. It exhibits an interesting polymeric structure in which the ruthenium(II) centers selectively form axial interdimer contacts with the O-atoms of the propionate groups only.The title compound, [Ru2(O2CCF3)4] (1), has been obtained without any exogenous ligands and crystallized by deposition from the gas phase at 170 C. Its crystal structure has been determined for the first time to confirm an infinite chain motif built on axial Ru···O interactions of the diruthenium(II,II) units. The X-ray diffraction studies at variable temperatures showed no phase transitions in the range of 295-100 K but revealed a significant decrease in the volume per atom from 14.2 to 13.3 Å3. This noticeable thermal compressibility effect is discussed in connection with the solid-state packing of the [Ru2(O2CCF3)4] chains. The highly electrophilic character of the diruthenium(II,II) units has been shown by the gas-phase deposition reaction of [Ru2(O2CCF3)4] with an aromatic donor substrate, namely [2.2]paracyclophane (C16H16). As a result of the above reaction, a new arene adduct [Ru2(O2CCF3)4·C16H16] (2) has been isolated in crystalline form. It has an extended one-dimensional (1D) chain structure comprised of alternating building units and based on the rare bridging mode of [2.2]paracyclophane, [Ru2(O2CCF3)4·(2-2:2-C16H16)]. The magnetic susceptibility of 1 and 2 has been measured and compared in the range of 1.8-300 K. In addition, in the course of synthesis of 1 by the carboxylate exchange reactions, a new mixed-carboxylate diruthenium(II,II) core complex [Ru2(O2CCF3)3(O2CC2H5)] (3), bearing no exogenous ligands, has also been isolated and structurally characterized. It exhibits an interesting polymeric structure in which the ruthenium(II) centers selectively form axial interdimer contacts with the O-atoms of the propionate groups only.

Tin–zinc pnictidehalides Sn20Zn4P22−vI8 ( v = 1.2 ), Sn17Zn7P22I8, and Sn17Zn7P22Br8 have been prepared as single-phase samples by a standard ampoule procedure. The compounds are isotypic and possess the structure of type-I gas hydrate (clathrate-I type). They all crystallize in the cubic space group Pm 3 ¯ n (no. 223) with the unit cell parameters a = 10.883 ( 2 ) A (Sn20Zn4P22−vI8), a = 10.8458 ( 3 ) A (Sn17Zn7P22I8), a = 10.7449 ( 2 ) A (Sn17Zn7P22Br8), and Z = 1 . The crystal structures of all compounds have been solved from single-crystal X-ray diffraction data sets and refined to R = 0.032 (Sn20Zn4P22−vI8), R = 0.027 (Sn17Zn7P22I8), and R = 0.020 (Sn17Zn7P22Br8). In all structures tin, zinc, and phosphorus atoms form the clathrate-I framework while the guest halogen atoms are encapsulated in the cavities of the framework. The compositions of the synthesized compounds are in agreement with those predicted by using the Zintl–Klemm concept. Sn20Zn4P22−vI8 contains two partially filled metal sites and vacancies in one of the phosphorus sites and can be formulated as Sn20Zn4P20.8□1.2I8 (or Sn20Zn4P22−1.2I8). Sn17Zn7P22I8 and Sn17Zn7P22Br8 are vacancy-free and reveal three partially filled positions of metal atoms. Thus, Sn17Zn7P22X8 and Sn20Zn4P20.8□1.2I8, being the limiting and the intermediate compositions, respectively, of the solid solutions of a general formula Sn24−nZnnP22−vX8 ( v = ( 14 − 2 n ) / 5 , X=Br, I), show different mechanisms of the structural stabilization. The 119Sn Mossbauer together with the 31P and 119Sn NMR spectra confirm the local environment of tin and phosphorus atoms in the structures of Sn17Zn7P22I8 and Sn17Zn7P22Br8. The compounds Sn17Zn7P22I8 and Sn17Zn7P22Br8 display diamagnetic and semiconducting behavior. The heat capacity has been measured for Sn17Zn7P22I8 in a temperature range of 6 K to 400 K. No low-temperature phase transitions have been detected in the measurements.

Two new supramolecular complexes, [Hg6As4](CuBr3)2 (1) and [Hg6As4](CuCl3)2 (2), have been synthesized and their crystal structures have been determined. Compound 1 crystallizes in the monoclinic system, space group I2/a (No. 15), with the unit cell dimensions a = 14.884(3), b = 9.358(2), c = 20.413(4) A, β=92.88(3)°, and Z = 6. The crystal structure is comprised of the three-dimensional \(_{\infty}^{3}\)[Hg6As4]4+ polycationic framework hosting one-dimensional 6-step helical \(_{\infty}^{1}\)(CuBr\(_{3})^{2-}\) guest chains built of the [CuBr4] tetrahedra sharing two of their vertexes. The complex 2 exhibits a distorted variant of the same type of crystal structure (space group I2/a, a = 14.690(1), b = 9.1851(7), c = 20.285(1) A, β=92.170(1), and Z = 6) that is characterized by a multifarious positioning of the guest anions in the cavities of the perfectly ordered \(_{\infty}^{3}\)[Hg6As4]4+ host framework. Structures of the title supramolecular assemblies and the previously reported silver-containing analogue [Hg6As4](AgCl3)2 are discussed taking into account the principles of host–guest complementarity.

Recent chemistry of four-membered ring selenium compounds is reviewed followed by a summary of work in our laboratories in this area. 2-Thia-6-selenaspiro[3.3]heptane has been synthesized for the first time. X-ray structures for the latter compound as well as for 2,6-dithiaspiro[3.3]heptane and 2,6-diselenaspiro[3.3]heptane have been determined. These compounds are useful as "rigid-rod" ligands for coordination to transition-metal complexes.

The structural investigation of Sn2P2O7 was carried out for the first time by means of single crystal and powder X-ray diffraction. The crystal structure of β-Sn2P2O7 pyrophosphate was solved using...

The disproportionation of the mixed-valence diruthenium(II, III) trifluoroacetate, [Ru2(O2CCF3)5] (1), is reported. The overall conversion leads to the triruthenium(II, III, III) and diruthenium(II, II) species according to the scheme: 4 Ru2 5+→ 2 Ru3 8+ + Ru2 4+. Both disproportionation products have been isolated and structurally characterized as they cocrystallize in a 2:1 ratio in the form of the acetone adducts to give the complex [Ru3O(O2CCF3)6·(OCMe2)3]2 [Ru2(O2CCF3)4·(OCMe2)2] (2). Compound 2 conforms to the triclinic space group, P 1 (No. 2), with the parameters a = 9. 9238(5) A, b = 12. 8388(7) A, c = 20. 1188(10) A, α = 103. 1390(10)°, β = 103. 1210(10)°, γ = 98. 1650(10)°, V = 2379. 8(2) A3, and Z = 1. The refinement of 747 parameters and 90 restraints resulted in the final R 1 value of 0. 0454 and wR 2 = 0. 0971 for 8003 reflections with I ≥ 2σ(I), and R 1 value of 0. 0697 and wR 2 = 0. 1071 for all 10, 755 data. The oxidized form is represented by a mixed-valence trinuclear ruthenium complex, [Ru3O(O2CCF3)6·(OCMe2 )3] (2a). This neutral complex possesses a μ3-oxo-centered Ru3O unit with peripheral ligands provided by bridging carboxylates and terminal acetone groups. The core dimensions of 2a indicate a valence-detrapped state in the range of temperatures 295–90 K. The central unit consists of a nearly equilateral triangular array with the Ru–O(oxo) bond distances of 1. 909(3), 1. 905(3), and 1. 910(3) A. The reduced form, [Ru2(O2CCF3)4·(OCMe2)2] (2b), is a typical tetrabridged diruthenium(II, II) carboxylate having coordinated acetone molecules at both axial sites. The Ru–Ru double bond in the paddlewheel unit is measured at 2. 2858(8) A. The mechanistic aspects of the disproportionation and the core conversion in 1 as well as in similar metal trifluoroacetates are discussed.

A novel supramolecular assembly [Hg6As4](AgCl3)2 has been prepared and its structure determined. It crystallizes in the monoclinic system, space group I2/a (no. 15), with the unit-cell dimensions a = 14.690(1), b = 9.1851(7), c = 20.285(1) A, β = 93.17(1)°, and Z = 4. The crystal structure comprises a three-dimensional cationic host framework, [Hg6As4]4+, built of mercury and arsenic atoms and one-dimensional ∞1(AgCl3)2− guest anions built of corner-sharing [AgCl4] tetrahedra. The title compound is the first example of a perfectly ordered supramolecular architecture having an infinite chain anion as a guest moiety embedded into a mercury−pnicogen cationic framework. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

The crystal structure of a new hybrid product comprised of two rigid building blocks, namely dirhodium(II) tetraacetate, [Rh(2)(O(2)CCH(3))(4)] (1), and 2,6-diselenaspiro[3.3]heptane, Se(2)C(5)H(8) (2), has been solved ab initio using laboratory source X-ray powder diffraction (XRPD) data. The rigid body refinement approach has been applied to assist in finding an adequate model and to reduce the number of the refined parameters. Complex [Rh(2)(O(2)CCH(3))(4).mu(2)-Se(2)C(5)H(8)-Se,Se'] (3) conforms to the triclinic unit cell with lattice parameters of a = 8.1357(4), b = 8.7736(4), and c = 15.2183(8) A, alpha = 77.417(3), beta = 88.837(3), and gamma = 69.276(4) degrees, V = 989.66(8) A(3), and Z = 2. The centrosymmetric P space group was selected for calculations. The final values of the reduced wR(p), R(p), and chi(2) were calculated at 0.0579, 0.0433, and 5.95, respectively. The structure of 3 is a one-dimensional zigzag polymer built on axial Rh...Se interactions at 2.632(6) A. The 2,6-diselenaspiro[3.3]heptane ligand acts as a bidentate linker bridging dirhodium units via both selenium atoms. The geometrical parameters of individual groups for rigid body refinement have been obtained from X-ray powder data for dirhodium(II) tetraacetate (1) and from single-crystal X-ray diffraction for diselenium molecule 2. The crystal structures of 1 and 2 are reported here for the first time. For 1 indexing based on XRPD data has resulted in the triclinic unit cell P with lattice parameters of a = 8.3392(7), b = 5.2216(5), and c = 7.5264(6) A, alpha = 95.547(10), beta = 78.101(6), and gamma = 104.714(13) degrees, V = 309.51(5) A(3), and Z = 1. The final values were wR(p) = 0.0452, R(p) = 0.0340, and chi(2) = 1.99. The 1D polymeric motif built on axial Rh.O interactions of the centrosymmetric dirhodium units has been confirmed for the solid-state structure of 1. Compound 2,6-diselenaspiro[3.3]heptane (2) conforms to the monoclinic space group P2(1)/c with the unit cell parameters of a = 5.9123(4), b = 19.6400(13), and c = 5.8877(4) A, beta = 108.5500(10) degrees, V = 648.15(8) A(3), and Z = 4.

A novel tin phosphide bromide, Sn24P19.3(2)Br8, and Sn24P19.3(2)BrxI8-x (x = 0−8) solid solution have been prepared and structurally characterized. All compounds crystallize with the type-I clathra...

The sila-β-diketone, 2,2,6,6-tetramethyl-2-silaheptane-3,5-dione (tmshdH), was synthesized by the condensation of the anion of 2-trimethylsilyl-1,3-dithiane with 1-bromo-3,3-dimethylbutan-2-one, followed by unmasking of the latent carbonyl moiety with HgO/HgCl 2 . A monoclinic polymorph of the known copper(II) complex, Cu(tmshd) 2 , was crystallized and studied by X-ray diffraction methods and found to be disordered like the orthorhombic one. Attempts to synthesize the disilylated β-diketone, 2,2,6,6-tetramethyl-2,6-disilaheptane-3,5-dione and monosilylated 4,4-dimethyl-4-sila-3-oxo-pentanal using the dithiane method were not successful. However, the 1,3-dithianyl precursors, along with the impurity 2,2 ′ -bis(trimethylsilyl)-2,2 ′ -bi-1,3-dithiane, were studied crystallographically. Large stereoelectronic and steric effects on the solid-state bonding parameters were observed for these molecules.

The use of the acetone monoadduct, [Rh2(O2CCF3)4·(OCMe2)], instead of unligated dirhodium(II) tetrakis(trifluoroacetate) in sublimation–deposition reactions allowed us to study coordination of thermally sensitive 1,4-diiodo-1,3-butadiyne. A new mixed-ligand organometallic compound, [Rh2(O2CCF3)4·(OCMe2)]2·(C4I2), has been isolated in crystalline form and shown by X-ray diffraction study to have an η2(1,2):η2(3,4)-bridging mode of diyne. This has demonstrated the donor ability of the diiodobutadiyne that was previously known to act as a π-acceptor through the Lewis acidic iodine atoms. This work has expanded the temperature limits of the solvent-free synthesis strategy for potential study of thermally unstable species.

A series of Co(III) diphenylglyoximato (dpgh) complexes, pyCo(dpgh)2R, with R=Cl (2a), CH3 (3a), CH2Me (4a), (CH2)2Me (5a), (CH2)3Me (6a), CHMe2 (7a), CH2SiMe3 (8a), CH2CMe3 (9a), CH2CHCH2 (10a), CH2Ph (11a), and CF3 (12a) were prepared, using Co(dpgh)(dpgh2)Cl2 (1a) as an entry to this system. The compounds were thoroughly characterized by 1H and 13C NMR spectroscopy, the spectra of which were compared to the corresponding Co(III) dimethylglyoximato (DH) complexes, pyCo(DH)2R (2b–12b). The NMR results suggest that the dpgh ligand is less electron-donating than DH. X-ray diffraction studies of complexes 8a, 9a and 12a demonstrate that subtle, but detectable structural changes occur upon substitution of dpgh for DH, due to increased interactions of the axial alkyl ligand with the equatorial ligand set.

For the first time the structural characterization of dimethyl selenoxide coordinated to metal complexes has been performed confirming the Me(2)SeO arrangement assigned by spectroscopic techniques for the molecule in solution and solid state. The structure of Me(2)SeO is trigonal pyramidal with Se-O and Se-C bond lengths of 1.70 and 1.92 A, respectively, and sigma(X-Se-Y) = 301 degrees. As a ligand, dimethyl selenoxide was found to bind to the rhodium centers of various Lewis acidity strengths by using only its oxo functionality in both terminal and bridging fashions. This O-directed coordination preference contrasts with an ambidentate (-S and -O) binding character revealed by dimethyl sulfoxide upon formation of analogous donor-acceptor complexes. The study of dimethyl selenoxide in the gas phase at 135-140 degrees C resulted in a thermal degradation of this molecule. The major decomposition product has been entrapped by a metal complex and identified as dimethyl selenide. The isolation of the coordinated Me(2)Se fragment clearly demonstrates that the Me(2)SeO molecule is less thermally stable than Me(2)SO, which under similar reaction conditions shows no sign of decomposition at temperatures up to 160 degrees C.

The reaction of Re 2 (O 2 CC 6 H 5 ) 4 Cl 2 with PMe 3 in ethanol in the presence of traces of air or a small amount of H 2 O 2 affords the unusual compound [Cl(PMe 3 ) 3 Re(μ-O 2 CC 6 H 5 )Re(O)] 2 (μ-O) 2 ( 1 ). The crystal structure of this new rhenium ‘dimer of dimers’ type compound has been established by X-ray crystallography. In this centrosymmetric molecule each dirhenium unit is supported by one benzoate ligand and further ligated by Cl, PMe 3 and O-ligands; the two dinuclear units are united by two μ-O atoms. Interestingly, the rhenium centers have rarely observed distinctly different coordination environments within the dimers, namely ReClOP 3 ReO 4 , which can be formally considered as Re(II)Re(IV) or Re(I)Re(V).

New dinuclear TiIV and TiIII complexes with the calix[4]arene ligand C28H20O4H4 (H4L) have been isolated from the reaction of Ti(NMe2)4, H4L, and Na (or KC8) in THF. X-ray analyses revealed a similar core structure for the two complexes Na4(THF)8[TiIV 2(μ-O)2L2] (1) and K4(THF)8[TiIII 2(μ-NMe2)2L2] (2). Two titanium atoms are bridged by two oxygen atoms in 1 and by two dimethylamido groups in 2 and are also supported by two deprotonated calix[4]arene ligands in a cone conformation. This resulted in a similar Ti⋯Ti separation of about 3.29 A in 1 and 3.28 A in 2 and in a distorted octahedral environment for each Ti center in both complexes. In contrast, in a novel complex 3, Na2(THF)6[TiIII 2L2], two TiIII atoms are supported only by two deprotonated ligands. This results in a five-coordinate environment for both titanium(III) centers with the separation between them being 3.133(1) A.

The reaction between the dirhenium(III,III) anion, [Re2Cl8]2−, and the secondary phosphine, PCy2H, yields a mixture of products as a result of disproportionation, namely, a dirhenium(II,III) chloride–phosphine complex 1,3,6-Re2Cl5(PCy2H)3 (1) and a dirhenium(IV) face-sharing bioctahedral compound with bridging phosphido groups, [Bun 4N][Re2(μ-PCy2)3Cl6] (2). The diphenylphosphine analogue of 2, [Bun 4N][Re2(μ-PPh2)3Cl6] (3) has been similarly prepared from the reaction of [Re2Cl8]2− with PPh2H. An interesting dirhenium(III,III) complex, [Bun 4N]2[Re2(μ-PPh2)2(PPh2H)2Cl6] (4) having both neutral terminal phosphines and anionic phosphido bridges, has also been isolated as an intermediate in the latter system. Crystal structures of 1–4 have been determined by X-ray crystallography. The compounds were also characterized by cyclic voltammetry, IR and 31P NMR spectroscopy.

A unique series of mixed-valent transition metal complexes (MIII = Fe; MII = Fe, Mn, Ni) have been designed using a combination of diketonate ligands with electron-withdrawing (blue) and electron-donating (pink) substituents., A novel series of mixed-valent, heteroleptic transition metal diketonates that can be utilized as prospective single-source precursors for the low-temperature preparation of oxide materials are reported. The first mixed-valent iron β-diketonates with different FeIII/FeII ratios have been synthesized by applying the mixed-ligand approach. Based on nearly quantitative reaction yields and analysis of iron–oxygen bonds, these compounds were formulated as [FeIII(acac)3][FeII(hfac)2] (1) and [FeII(hfac)2][FeIII(acac)3][FeII(hfac)2] (2). In the above heteroleptic complexes, the Lewis acidic, coordinatively unsaturated FeII centers chelated by two hfac (hexafluoroacetylacetonate) ligands with electron-withdrawing substituents maintain bridging interactions with oxygen atoms of electron-donating acac (acetylacetonate) groups that chelate the neighboring FeIII atoms. Switching the ligands on FeIII and FeII atoms in starting reagents resulted in the instant ligand exchange between iron centers and in yet another polynuclear homometallic diketonate [FeII(hfac)2][FeIII(acac)2(hfac)][FeII(hfac)2] (3) that adheres to the same bonding pattern as in complexes 1 and 2. The proposed synthetic methodology has been extended to design heterometallic diketonates with different M : M′ ratios. Homometallic parent molecules have been used as templates to obtain heterometallic mixed-valent [FeIII(acac)3][MnII(hfac)2] (4) and [NiII(hfac)2][FeIII(acac)3][NiII(hfac)2] (5) complexes. The combination of two different diketonate ligands with electron-donating and electron-withdrawing substituents was found to be crucial for maintaining the above mixed-valent heterometallic assemblies. Theoretical investigation of two possible “isomers”, [FeIII(acac)3][MnII(hfac)2] (4) and [MnIII(acac)3][FeII(hfac)2] (4′) provided an additional support for the metal site assignment giving a preference of 9.78 kcal mol–1 for the molecule 4. Heterometallic complexes obtained in the course of this study have been found to act as effective single-source precursors for the synthesis of mixed-transition metal oxide materials MxM′2–xO3 and MxM′1–xO. The title highly volatile precursors can be used for the low-temperature preparation of both amorphous and crystalline heterometallic oxides in the form of thin films or nanosized particles that are known to operate as efficient catalysts in oxygen evolution reaction.

Reactions of the octaiododirhenate anion [Re2I8]2− with monodentate phosphines (PR3=PMe3 (1), PMe2Ph (2), PEt3 (3), and PEt2Ph (4)) have been studied in two different solvents, ethanol and benzene, at room temperature. The reactions in ethanol resulted in two-electron reduction products having the Re2 4+ core, Re2I4(PR3)4 (R3=Me3 (1a) and Me2Ph (2a)), for which X-ray diffraction study revealed a 1,3,6,8 isomer type. The reaction of [Re2I8]2− with PMe3 in benzene led to an intermediate edge-sharing bioctahedral dirhenium(III) complex, Re2(μ-I)2I4(PMe3)4 (1b), with no metal–metal bond. The interaction of PEt3 with [Re2I8]2− in benzene again yielded a kinetic product with a different stoichiometry and a Re2 5+ core, [Bun4N][Re2I6(PEt3)2] (3c). The analogous reactions of [Re2I8]2− with PMe2Ph and PEt2Ph in benzene involved two-electron reductions and gave complex 2a and Re2I4(PEt2Ph)4 (4a), as products. Reduction of 1b with KC8 gave 1a as the main product along with a few crystals of 1,3,6-Re2I5(PMe3)3 (1d). Mixed iodide/phosphine complexes of the dirhenium core Re2 n+, where n=4 (1a, 2a, 4a), 5 (1d, 3c), and 6 (1b) have for the first time been characterized by X-ray crystallography. In addition, these products have been further identified by a combination of mass spectrometry and cyclic voltammetric measurements.

New mixed bismuth monohalides Bi4BrxI4–x (x = 1, 2, or 3) were prepared for the first time by the reactions of bismuth metal with bismuth trihalides taken in stoichiometric amounts. Their crystal structures were established by single-crystal X-ray diffraction analysis. The Bi4Br3I and Bi4BrI3 compounds are isostructural and crystallize in the orthorhombic system, and Bi4Br2I2 crystallizes in the monoclinic system. The crystal structures of all three phases contain one-dimensionally infinite molecular chains consisting of the [Bi4X4] fragments whose structures are identical with those of the individual Bi4I4 and Bi4Br4 molecules. The molecules are packed in layers. Different packing modes of the layers were found for different bismuth monohalides. The Bi4ClI3 compound, which is apparently structurally similar to Bi4Br3I and Bi4BrI3, was also prepared.

Two extremely unstable copper trifluoroacetates with no exogenous ligands, namely, Cu(O2CCF3) (1) and Cu(O2CCF3)2 (2), are prepared for the first time and obtained in crystalline form by deposition from the vapor phase. Their structures are determined by X-ray crystallography. The crystallographic parameters are as follows: for 1, monoclinic space group P2(1)/c, with a = 9.7937(6) A, b = 15.322(1) A, c = 12.002(1) A, beta = 106.493(9) degrees, and Z = 4; for 2, orthorhombic space group Pcca, with a = 16.911(1) A, b = 10.5063(9) A, c = 9.0357(6) A, and Z = 4. Both structures are unique among other CuI and CuII carboxylates, as well as among metal carboxylates in general. Compound 1 consists of a planar rhombus of four copper atoms with sides of 2.719(1)-2.833(1) A and trifluoroacetate ligands bridging the pairs of adjacent metal atoms alternately above and below the plane. The tetrameric units are further aggregated in a polymeric zigzag ribbon [Cu4(O2CCF3)4]infinity by virtue of intermolecular Cu...O contacts. The structure of 2 is built on cis bis-bridged dimers in which every metal atom is also connected with two copper atoms of the neighboring units. The stacking planes in this extended chain are almost perpendicular to one another. The Cu...Cu distance inside the dimer is 3.086(2) A, indicating a nonbonding interaction.

The interaction of benzene, p-xylene, and naphthalene with a strong two-ended Lewis acid, Rh2(O2CCF3)4, led to one-dimensional linear polymers of 1:1 composition, [Rh2(O2CCF3)4·L], where L C6H6 (1), p-(CH3)2C6H4 (2), and C10H8 (3). Compounds 1‐3 have been characterized by elemental analysis and IR spectroscopy and their structures have been determined by X-ray diffraction. In the crystal structures of the compounds the alternating arrangement of the dirhodium(II) tetrakis(trifluoroacetate) units with the aromatic ligands coordinated to their axial positions forms infinite chains extended along one direction of the unit cell. The rare bridging off-centered, h 2 :h 2 coordination of arene groups by the Rh(II) centers was found to be preferred in all three cases with the two closest RhCarene distances averaged to 2.662(6) A, in the benzene complex (1), to 2.684(7) A, in the p-xylene analogue (2), and to 2.588(9) A, in the naphthalene product (3). © 2000 Elsevier Science Ltd. All rights reserved.

The ambidentate character of dimethyl sulfoxide, already known for dirhodium carboxylates, has been remarkably manifested in new ways. Three novel complexes of dirhodium(II) tetra(trifluoroacetate) with the DMSO ligand, namely, [Rh2(O2CCF3)4]m(DMSO)n with m:n = 7:8 (1), 1:1 (2), and 3:2 (3), have been obtained by deposition from the vapor phase, and their crystal structures have been determined by X-ray crystallography. The crystallographic parameters are as follows: for 1, monoclinic space group P2(1)/c with a = 28.261(2) A, b = 16.059(4) A, c = 17.636(2) A, beta = 92.40(4) degrees, and Z = 2; for 2, triclinic space group P1 with a = 8.915(2) A, b = 10.592(2) A, c = 11.916(2) A, alpha = 84.85(1) degrees, beta = 88.86(1) degrees, and gamma = 65.187(8) degrees, and Z = 2; and for 3, triclinic space group P1 with a = 8.876(2) A, b = 9.017(2) A, c = 19.841(3) A, alpha = 101.91(2) degrees, beta = 97.144(8) degrees, gamma = 100.206(9) degrees, and Z = 1. In the oligomeric molecule of 1, six DMSO ligands bridge seven dirhodium tetra(trifluoroacetate) units in a bidentate fashion via S and O atoms, and two additional DMSO molecules terminate the chain. In the structure of the monoadduct Rh2(O2CCF3)4(DMSO) (2), the dirhodium blocks are bridged through the O atoms of DMSO ligands, forming a one-dimensional polymeric chain. Compound 3 also has an infinite chain structure with the molecules of dimethyl sulfoxide acting in a bidentate mu-DMSO-S,O mode. Every second DMSO molecule is missing in 3, so that two of every three Rh2(O2CCF3)4 units are associated through the O atoms of carboxylate groups to give the overall composition [Rh2(O2CCF3)4]3(DMSO)2.

The substitution reactions of primary amines by tertiary phosphines in quadruply bonded dimolybdenum(II,II) complexes Mo2Cl4(NH2R)4 have been studied. The exchange reaction has been shown to result at room temperature in disubstituted species Mo2Cl4(NH2R)2(PR3)2 (PR3 = PMe3, NH2R = NH2Prn (1a), NH2But (2a), NH2Cy (3a); PR3 = PMe2Ph, NH2R = NH2Cy (4a)), while heating is needed to obtain fully substituted complexes Mo2Cl4(PR3)4. The crystal structure of disubstituted products has been investigated by X-ray crystallography and revealed that they all belong to the alpha-isomer, having both phosphine groups at the same Mo atom. Crystal data are as follows: for 1a, tetragonal space group I4(1/a) with a = 17.737(2) A, c = 15.6915(6) A, and Z = 8; for 3a, monoclinic space group P2(1) with a = 10.963(3) A, b = 10.117(2) A, c = 13.323(4) A, beta = 90.05(2) degrees, and Z = 2; for 4a, triclinic space group P1 with a = 9.329(3) A, b = 10.206(2) A, c = 18.975(3) A, alpha = 85.45(2) degrees, beta = 87.10(1) degrees, gamma = 80.88(1) degrees, and Z = 2. The substitution processes for the direct and reverse reactions have been monitored by 31P NMR. They both proceed in a stepwise manner; however, a stereochemical hysteresis is taking place, i.e., the back reaction, the substitution of phosphines by amines, goes through another isomer of Mo2Cl4(NH2R)2(PR3)2, having phosphine ligands on different Mo atoms. This beta-isomer is more thermodynamically stable and can be obtained by thermal conversion of the alpha-form. All chemical equilibria studied in the paper have been explained as governed by a higher trans effect of PR3 groups compared to NH2R groups.

The relative stabilities of rotation conformational isomers of Mo2Cl4(R-py)4 molecules in solution have been studied. R-py represents a substituted pyridine, 4-tert-butylpyridine, 4-picoline, or 3,...

The monoadduct of dirhodium tetra(trifluoroacetate) with THF has been obtained by deposition from the vapor phase. The compound Rh(2)(O(2)CCF(3))(4)(THF) crystallizes in two isomeric forms, 1 and 2, whose structures have been determined by X-ray crystallography. The crystallographic parameters are as follows: for 1, triclinic space group Ponemacr; with a = 9.557(2) Å, b = 10.126(2) Å, c = 11.840(4) Å, alpha = 95.97(2) degrees, beta = 90.40(2) degrees, gamma = 115.58(1) degrees, and Z = 2; for 2, triclinic space group Ponemacr; with a = 8.6347(3) Å, b = 9.678(1) Å, c = 13.773(4) Å, alpha = 73.182(5) degrees, beta = 74.622(5) degrees, gamma = 89.76(1) degrees, and Z = 2. Compound 1 is unique as the only extended structure where dirhodium carboxylate molecules are bridged by a single exogenous atom. The oxygen atom of the THF ligand coordinates to the axial positions of two Rh(2) units so that a one-dimensional zigzag chain is formed. The bridging is slightly asymmetric with Rh-O(THF) distances of 2.363(6) and 2.407(6) Å, and the Rh-O(THF)-Rh angle is 111.8(3) degrees. The crystal structure of 2 is not polymeric. Pairs of Rh(2)(O(2)CCF(3))(4)(THF) units are associated through O atoms of carboxylate groups to produce a dimer of dimers. The lengths of the terminal Rh-O(THF) and axial bridging Rh.O(Ac) interactions are 2.214(7) and 2.406(6) Å, respectively.

Several new paramagnetic dirhenium(II,III) anions of the formula [Re2Cl6P2]- (P2 = (PPrn3)2 (1), (PEt2Ph)2 (2), dppp (3)) have been isolated in the form of their tetrabutylammonium salts as the kinetic products in reactions of [Re2Cl8]2- with an appropriate phosphine ligand. All three complexes have been characterized in solution by cyclic voltammetry, ESR, and mass spectroscopy. Three different isomeric forms of the [Re2Cl6P2] core have been recognized in the solid state by X-ray crystallography. The known 1,7-isomer (C2h) with a centrosymmetric disposition of phosphine groups was found for PPrn3 (1a) and PEt2Ph (2) ligands. The compound [Bun4N][Re2Cl6(PPrn3)2] was also crystallized in the unprecedented form of a 1,6-isomer (C2) (1b) which can be derived from 1a by a 90° rotation of the ligands around the metal−metal bond. For the diphosphine, a Cs isomer of [Re2Cl6(dppp)]- (3) was discovered having the dppp ligand chelating on one rhenium atom. Crystallographic data are as follows: for 1a, monoclinic s...

Four new quadruply-bonded dimolybdenum(II) complexes of the formula Mo2Cl4(NH2R)4 (R = Et (1), Prn (2), But (3), Cy (4)) have been prepared in excellent yield by reduction of the dimolybdenum(III) ...

A tetrameric complex [Re(CO)3(μ-CH3CO2)(THF)]4 (1) is formed in high yield when the reaction product of Re(CO)5Cl with acetic acid in refluxing 1,2-dichlorobenzene is dissolved in THF. The use of Re2(CO)10 instead of rhenium pentacarbonyl chloride also affords 1. The characterization of 1·3THF·0.5C6H14 has been accomplished by X-ray crystallography. The structure of the tetrameric molecule 1 consists of four rhenium(I) atoms bridged by four acetate ligands. The coordination of each metal center is fulfilled by three CO groups and one THF molecule in a way that all carbonyls are trans to oxygen atoms. The geometry of each acetate bridge is anti–syn providing a Re to Re separation of 5.40 A. This bonding mode is seen here for the first time in rhenium carboxylates. Different coordination types for Re–RCO2 interaction are also discussed in the paper.

The interaction between octachlorodirhenium anions and diethylphosphine has been shown to strongly depend on reaction conditions, mainly the nature of the solvent and the amount of phosphine. As a result, novel dirhenium products with oxidation states ranging from Re(II) to Re(IV) have been obtained. The reaction of [Re(2)Cl(8)](2)(-) with an excess of PEt(2)H in dichloromethane or acetonitrile led to the first example of a face-sharing complex of rhenium(IV) with three phosphido-bridges, namely [Bu(n)(4)N][Re(2)(mgr;-PEt(2))(3)Cl(6)] (1). The unusual edge-sharing Re(2)(mgr;-PEt(2))(2)Cl(4)(PEt(2)H)(4) (2) complex of rhenium(III) with C(i)() core symmetry, containing both terminal phosphines and phosphido-bridges, has been obtained by carrying out the reaction with an excess of PEt(2)H in a benzene (or propanol) - HCl mixture at room temperature. A new example of the 1,2,7,8-type of dirhenium(II) complex, Re(2)Cl(4)(PEt(2)H)(4) (3), having diethylphosphine ligands located cis on each Re atom, has been isolated from the reaction of [Re(2)Cl(8)](2)(-) with PEt(2)H in an ethanol-HCl medium. The solid-state structures of complexes 1-3 have been investigated by X-ray crystallography. Complexes 1 and 2 both crystallized in two forms: [Bu(n)(4)N][Re(2)(mgr;-PEt(2))(3)Cl(6)] 1a, P2(1)/n with a = 10.482(1) Å, b = 16.512(2) Å, c = 23.986(2) Å, beta = 93.637(8) degrees, and Z = 4; [Bu(n)(4)N][Re(2)(mgr;-PEt(2))(3)Cl(6)].1.5 C(7)H(8) 1b, C2/c with a = 38.746(9) Å, b = 10.322(2) Å, c = 27.277(3) Å, beta = 110.35(1) degrees, and Z = 8; Re(2)(mgr;-PEt(2))(2)Cl(4)(PEt(2)H)(4) 2a, P2(1)/n with a = 11.081(3) Å, b = 11.029(3) Å, c = 15.627(2) Å, beta = 90.05(1) degrees, and Z = 2; 2b, P2(1)/c with a = 16.094(3) Å, b = 15.193(3) Å, c = 15.548(3) Å, beta = 100.98(3) degrees, and Z = 4. X-ray data for complex Re(2)Cl(4)(PEt(2)H)(4) 3 are as follows: P2(1)/n with a = 10.445(2) Å, b = 10.113(3) Å, c = 13.473(2) Å, beta = 102.17(2) degrees, and Z = 2. Three bridgingmgr;-PEt(2) groups in the face-sharing complex 1 span a short metal-metal distance of 2.4060(6) Å, averaged over 1a and 1b, with a small Re-PEt(2)-Re angle of 61.34(7) degrees. The rhenium-rhenium bond length in the edge-sharing complex 2 is 2.7545(7) Å, averaged over 2a and 2b, while the bridging Re-PEt(2)-Re angle is 72.16(6) degrees, and the P-Re-P angle for the terminal phosphine ligands is 87.11(7) degrees. The Re-Re bond distance in 3, 2.2533(8) Å, is typical for triply bonded dirhenium complexes, and the P-Re-P angle for the cis phosphine groups is 93.12(6) degrees.

Reaction of the molybdenum(III) complex Mo2Cl6(THF)3 with diethylamine at room temperature causes reduction of the starting compound to produce the dimolybdenum(II) complex Mo2Cl4(NHEt2)4 (1). It was shown that the Cl- anions released by the substitution with amine can react with more of the starting material to give side products of molybdenum(III). Four such products were isolated and characterized: [NH2Et2][MoCl4(NHEt2)2] (2), [NH2Et2][Mo2Cl7(NHEt2)2] (3), [NH2Et2]2[MoCl5(NHEt2)] (4), and [NH2Et2]3[Mo2Cl8(NEt2)] (5). The crystal structures of all complexes 1−5 have been investigated by X-ray diffraction. The structure of 1 consists of two trans-MoCl2(NHEt2)2 units joined by a quadruple Mo−Mo bond (2.1330(6) A). The crystallographic parameters for compounds 1−5 are as follows: for 1, monoclinic space group C2/c with a = 20.846(1) A, b = 7.044(1) A, c = 19.868(3) A, β = 118.72(2)°, and Z = 4; for 2, triclinic space group P1 with a = 9.820(3) A, b = 10.305(1) A, c = 11.510(1) A, α = 95.779(8)°, β = 97....

Two geometrical isomers of the composition Re2Cl5(PMe2Ph)3, namely 1,2,7 and 1,3,6, have been prepared. The unusual paramagnetic 1,2,7-Re2Cl5(PMe2Ph)3 (1a), the first analogue of the previously reported trimethylphosphine complex 1,2,7-Re2Cl5(PMe3)3, has been synthesized by carrying out the reaction of octachlorodirhenium anions with PMe2Ph in benzene at room temperature. A different reaction product, 1,3,6-Re2Cl5(PMe2Ph)3 (1b), was obtained when [Bun4N]2Re2Cl8 was reacted with PMe2Ph under the same conditions in acetonitrile. Electrochemical studies revealed that both 1a and 1b, as expected for the Re25+ core, are capable of undergoing a one-electron reduction and a one-electron oxidation to yield the respective Re24+ and Re26+ dinuclear complexes. Both processes have been accomplished chemically for the 1,2,7-isomer in the present work. One-electron reduction of 1a by cobaltocene followed by nonredox substitution of a chloride ligand in the resulting anionic species by PMe2Ph affords triply bonded 1,2,7...

Single crystals of a new complex phosphate, calcium sodium vanadium phosphate, Ca8.42Na1.16V(PO4)7, have been grown from a melt under an inert atmosphere. The crystal structure has rhombohedral (R3c) symmetry and belongs to the whitlockite structure type. Vanadium(III) ions occupy nearly regular octahedral sites (M5 with 3 point symmetry), which share corners with six PO4 tetrahedra to form isolated units. The calcium ions occupy eight- and nine-coordinated sites. The sodium ions partially occupy one octahedral position and share one nine-coordinated position with a Ca atom.

The unusual 1,2,7-isomer of Re2Cl5(PMe3)3 (1) has been used as a starting material to prepare previously unknown dirhenium complexes. One-electron reduction of 1 by cobaltocene followed by nonredox substitution of the resulting anionic species with PMe3 led to the formation of a triply bonded 1,2,7,8-Re2Cl4(PMe3)4 (2). In the crystal structure of 2, phosphine ligands on both metal centers exhibit a cis arrangement with a P−Re−P angle of 93.3° in contrast to the well-known type of 1,3,6,8-isomers with a trans arrangement of the monodentate phosphines connected to each metal atom. Complex 2 represents the first example of an isomer of this type in the large M2X4(PR3)4 class of compounds (M = Re, Tc, W, Mo; X = Cl, Br, I; PR3 = monodentate phosphine). The one-electron oxidation product of 1 cocrystallized with one molecule of tetrabutylammonium chloride afforded Re2Cl6(PMe3)2 (3), for which all previous synthetic attempts had failed. This quadruply bonded complex exhibits an unusual 3-fold disorder of the Re...

The triply-bonded ditungsten(III) species trans,trans-W2Cl4(NBu2n)2(dppp) (1) and a new mixed-valent WIII/WIV complex (dppp)ClW(μ-Cl)3WCl2(NBu2n) (3) have been isolated from the reaction of W2Cl4(NBu2n)2(NHBu2n)2 with 1,3-bis(diphenylphosphino)propane (dppp). A complex similar to 3, (dppp)ClW(μ-Cl)3WCl2(NEt2) (2), has also been prepared. Both 2 and 3 are characterized by a W27+ core and they adopt face-sharing bioctahedral geometry with a chelating dppp ligand. The WW distances in 2 and 3 are both 2.660(1) A and each of them shows an EPR signal at g = 1.88. The structure of 1 contains a W26+ core with a WW distance of 2.3055(8) A. It has a bridging dppp ligand and a trans,trans stereochemistry.

The reactions of W 2 Cl 4 (NR 2 ) 2 (NHR 2 ) 2 (R=Et, Bu n ) with a stoichiometric amount of bis(diphenylphosphino)methane (dppm) readily resulted in the isolation of two new triply-bonded ditungsten(III) compounds cis,cis -W 2 Cl 4 (NR 2 ) 2 (dppm) (R=Et ( 1 ), R=Bu n ( 2 )) in moderate yields. The molecular structures of both compounds have been determined by X-ray crystallography and their crystallographic data are as follows: 1 ·CH 2 Cl 2 , monoclinic, space group C 2/ c , a =38.729(5), b =11.662(1), c =19.045(2) A, β =113.57(1)°, V =7884(2) A 3 , Z =8, R =0.026, wR 2=0.055; 2 , monoclinic, space group P 2 1 / n , a =14.4962(5), b =18.6305(8), c =17.1667(6) A, β =97.974(4)°, V =4591.4(3) A 3 , Z =4, R =0.043, wR 2=0.102. Both molecules are characterized by a W 2 6+ core with a σ 2 π 4 bond of order three and the W–W distances are 2.3350(3) and 2.3463(4) A, respectively, for 1 and 2 . They entail an essentially staggered rotational geometry and exhibit significant torsion angles in the solid state. Similar procedure has also been used to prepare similar W 2 6+ complexes containing bis(diphenylphosphino)amine (dppa) ligands and complexes of the type W 2 Cl 4 (NR 2 ) 2 (dppa) (R=Et ( 3 ), R=Bu n ( 4 )) have been characterized by 31 P{ 1 H} NMR spectroscopy at room temperature. In leading to the reaction pathway of complexes of this kind, the time sequences for the formation of 1 and 2 have been followed by variable temperature 31 P{ 1 H} NMR spectroscopic method. In all cases, the trans,trans -isomers of W 2 Cl 4 (NR 2 ) 2 (L–L) (R=Et, Bu n ; L–L=dppm, dppa) are the kinetically favored products while the cis,cis -isomers are the thermodynamic products. The corresponding cis,trans compounds are believed to be the likely intermediate complexes. In the course of a synthetic program directed towards the preparation of a dppa substitution complex of W 2 Cl 4 (NHCMe 3 ) 2 (NH 2 CMe 3 ) 2 , an unexpected ditungsten compound W 2 Cl 3 (NHCMe 3 ) 2 (NH 2 CMe 3 )(PPh 2 NPOPh 2 ) ( 5 ) has been prepared and structurally characterized. Compound 5 crystallizes in the triclinic space group P 1 , a =11.269(2), b =12.020(5), c =18.182(2) A, α =93.27(1), β =89.72(1), γ =93.275(2)°, V =2455(1) A 3 , Z =2, R =0.068, wR 2=0.153. The W–W distance in 5 is 2.3030(8) A and the molecule consists of an anionic bridging ligand [N(OPPh 2 )PPh 2 ] − , forming a six-membered metallacycle with the ditungsten unit.

Treatment of W2Cl6(THF)4 with alkylamine NH2R (R = Bus, Cy) affords a dinuclear species having the stoichiometry W2Cl4(NHR)2(NH2R)2 (R = Bus (1), Cy (2)). This has been confirmed by single-crystal X-ray diffraction studies for 2 with the following crystal data: tetragonal space group P421c, a = 12.774(2) A, c = 9.934(2) A, Z = 2. The molecule possesses an eclipsed structure with strong NH···Cl intramolecular hydrogen bonding, with disordering of the whole set of ligands containing the amide, amine, and chlorine ligands. Attempts have been made to treat and refine both ligand sets separately for this molecule, and the final refinement converges with reasonable bond distances and angles to R = 0.028 and wR2 = 0.066. In both orientations, the ligand arrangements are the same. Each W atom is surrounded by a trans set of two Cl and two N atoms with a W−W separation of 2.2884(9) A. Substitution of the amine ligands in 1 and 2 by the monodentate phosphine PMe3 proceeds smoothly to produce trans-W2Cl4(NHR)2(PMe...

The triply-bonded ditungsten(III) complexes of stoichiometry W2Cl4(NHR)2(PMe3)2 (R = Et, Prn, Bun) are formed by a two-step, one-pot, synthesis from the reaction of W2Cl6(THF)4 with the appropriate alkylamines NH2R (R = Et, Prn, Bun), followed by phosphine substitution. The dinuclear species W2Cl4(NHR)2(NH2R)2 are the probable intermediate complexes for such reactions. In each case, three isomeric forms have been detected in solution by 31P{1H}NMR spectroscopy, and they are formulated as the trans isomers and the two types of cis isomers possessing Ci and C2 symmetries. It has also been shown that the trans isomers are the initial (kinetic) products irrespective of the R group. The X-ray crystallographic characterization of the Ci isomer of cis-W2Cl4(NHEt)2(PMe3)2 (1), the C2 isomer of cis-W2Cl4(NHPrn)2(PMe3)2 (2), and the C2 isomer of cis-W2Cl4(NHBun)2(PMe3)2 (3a,b) has been accomplished. Crystallographic data are as follows: compound 1, triclinic space group P1, a = 7.4366(2) A, b = 8.8618(6) A, c = 9...

A new and convenient synthetic route to a series of W⋮W compounds with the general formula W2Cl4(NR2)2(PR‘3)2 has been developed. The method has been used in the preparation of W2Cl4(NR2)2(PMe3)2 (R = Et (2), Bu (3), Hex (4)) and W2Cl4(NR2)2(PEt2H)2 (R = Et (5), Bu (6), Hex (7)). Treatment of W2Cl6(THF)4 with the appropriate dialkylamine NHR2 (R = Et, Bu, Hex) affords an intermediate species having the stoichiometry W2Cl4(NR2)2(NHR2)2. This has been verified by single-crystal X-ray diffraction studies for W2Cl4(NEt2)2(NHEt2)2 (1) with the following crystallographic parameters: orthorhombic space group Iba2, a = 11.6704(9) A, b = 13.336(1) A, c = 17.321(2) A, Z = 4. The structure of 1 reveals that the molecule itself deviates from an eclipsed conformation with retention of a strong intramolecular N−H···Cl hydrogen bonding and the torsion angle involving the hydrogen bonded N and Cl atoms is 27.0°. Each W atom is coordinated by a cis set of two Cl and two N atoms with a W−W distance of 2.3084(5) A. There i...