Unprecedented association of [Mo6Br(i) 7Y(i)Br(a) 6]3- cluster units and [Mo(III)Br6]3- complexes: synthesis, crystal structures, and properties of the double salts Rb3[Mo6Br(i) 7Y(i)Br(a) 6](Rb3[MoBr6])3 (Y=Se, Te)

The double salts Rb(3)[Mo(6)Br(i) (7)Y(i)Br(a) (6)](Rb(3)[MoBr(6)])(3) (Y=Se, Te) result from the partial disproportionation of the Mo(6)Br(12) octahedral-cluster-based bromide, in the presence of corresponding chalcogenides and RbBr salt (crystal data: Rb(12)[MoBr(6)](3)[Mo(6)Br(i) (7)Te(i)Br(a) (6)] (1), Pm$\bar 3$m (No. 221), a=12.1558(2) A, Z=1, R(1)=0.028; wR(2)=0.050; Rb(12)[MoBr(6)](3)[Mo(6)Br(i) (7)Se(i)Br(a) (6)] (2), Pm$\bar 3$m, a=12.144(3) A, Z=1, R(1)=0.028; wR(2)=0.050). The structures of 1 and 2 are built up from [Mo(III)Br(6)](3-) complexes and [Mo(6)Br(i) (7)Y(i)Br(a) (6)](3-) cluster units characterised by a random distribution of seven bromine and one chalcogen ligands on all the eight inner positions that face cap the Mo(6) clusters. Such a distribution implies a static orientational disorder of the [Mo(6)Br(i) (7)Y(i)Br(a) (6)](3-) units around the origin of the unit cell. Close-packed anionic layers based on [Mo(III)Br(6)](3-) complexes and [Mo(6)Br(i) (7)Y(i)Br(a) (6)](3-) cluster units are stacked in the sequence ABC. This arrangement leads to very short Br(a)--Br(a) intercluster unit distances of 3.252 A, much lower than the sum of the van der Waals radii (3.70 A). The trivalent oxidation state of molybdenum in the Mo complexes and 24 valence electrons per Mo(6) cluster have been confirmed by magnetic susceptibility measurements. Salts 1 and 2 constitute the first examples of structurally characterised bromides containing discrete [Mo(III)Br(6)](3-) complexes obtained by means of solid-state synthesis.     

From simple monopyridine clusters [Mo6Br13(Py-R)][n-Bu4N] and hexapyridine clusters [Mo6X8(Py-R)6][OSO2CF3]4 (X = Br or I) to cluster-cored organometallic stars, dendrons, and dendrimers

Hexasubstitution of apical triflate ligands in the octahedral clusters [M]2[Mo6X8(CF3SO3)6] (M = n-Bu4N or Cs, X = Br or I) and monosubstitution in [n-Bu4N]2[Mo6Br13(CF3SO3)] was carried out in tetrahydrofuran at 60 degrees C with simple pyridines and then extended to organometallic pyridines, yielding cluster-cored stars, and to dendronic polyallyl- and polyferrocenylpyridines, yielding cluster-cored polyallyl and polyferrocenyl dendrimers and dendrons. The orange pyridine-substituted clusters, whose pyridine protons are deshielded in 1H NMR (a practical tool for characterization), are air-stable and thermally stable with simple pyridines, light- and air-sensitive with organometallic pyridines, and air-fragile and thermally fragile with large dendronized pyridines.     

Electronic structure and metal-metal interactions in trinuclear face-shared [M3X12]3- (M = Mo, W; X = F, Cl, Br, I) systems

The molecular and electronic structures of trinuclear face-shared [M3X12]3-species of Mo (X = F, Cl, Br, I) and W (X = Cl), containing linear chains of metal atoms, have been investigated using density functional theory. The possibility of variations in structure and bonding has been explored by considering both symmetric (D3d) and unsymmetric (C3v) forms, the latter having one long and one short metal-metal distance. Analysis of the bonding in the structurally characterized [Mo3I12]3- trimer reveals that the metal-metal interaction qualitatively corresponds to a two-electron three-center sigma bond between the Mo atoms and, consequently, a formal Mo-Mo bond order of 0.5. However, the calculated spin densities suggest that the electrons in the metal-metal sigma bond are not fully decoupled and therefore participate in the antiferromagnetic interactions of the metal cluster. Although the same observation applies to [Mo3X12]3- (X = Br, Cl, F) and [W3Cl12]3-, both the spin densities and shorter distances between the metal atoms indicate that the metal-metal interaction is stronger in these systems. The broken-symmetry approach combined with spin projection has been used to determine the energy of the low-lying spin multiplets arising from the magnetic coupling between the metal centers. Either the symmetric and unsymmetric S = 3/2 state is predicted to be the ground state for all five systems. For [Mo3X12]3- (X = Cl, Br, I), the symmetric form is more stable but the unsymmetric structure, where two metal centers are involved in a metal-metal triple bond while the third center is decoupled, lies close in energy and is thermally accessible. Consequently, at room temperature, interconversion between the two energetically equivalent configurations of the unsymmetric form should result in an averaged structure that is symmetric. This prediction is consistent with the reported structure of [Mo3I12]3-, which, although symmetric, indicates significant movement of the central Mo atom toward the terminal Mo atoms on either side. In contrast, unsymmetric structures with a triple bond between two metal centers are predicted for [Mo3F2]3- and [W3C12]3-, as the symmetric structure lies too high in energy to be thermally accessible.     

Synthesis and structures of Mo3Se7Te2Br10, Mo3Se7TeI6, and Mo6Te21I22 containing TeX3- (X=Br, I) ligands coordinated to a triangular cluster core

New ternary and quaternary molybdenum cluster chalcohalides were obtained by high-temperature reactions between Mo, chalcogens, and halogens in evacuated ampules. The crystal structures of [Mo3Se7(TeBr3)Br2]2[Te2Br10] (1), [Mo3Se7(TeI3)I2]I (2), and [Mo3Te7(TeI3)3]2(I)(TeI3) (3) were determined by single-crystal X-ray diffraction. The structures of 1 and 2 consist of positively charged zigzag chains infinity1 [Mo3Se7(TeX3)X4/2] (X=Br, I), with Te2Br102- and I-, respectively, as counterions. The TeI3- and TeBr3- ions function as bidentate ligands in 1 and 2. In 3, TeI3- is not coordinated to the metal but acts as a counterion to the [Mo3Te7(TeI3)3]+ cluster cation.     

Die Kristallstruktur der Hexaquomagnesiumhexahalogeno-dimercurate [Mg(OH2)6][Hg2X6] (X = Br,I)

Crystal Structure of the Hexaquomagnesiumhexahalogenodimercurates [Mg(OH₂)₆][Hg₂X₆] (X = Br, I) Hexaquodimercurates [Mg(OH₂)₆][Hg₂X₆] (X = Br, I) were obtained by crystallization from aqueous solutions of HgX₂ and MgX₂. The crystal structure of the monoclinic compounds consists of binuclear Hg₂X₆ anions and octahedral Mg(OH₂)₆ cations.     

Resonance Raman Spectra of [M(6)X(8)Y(6)](2)(-) Cluster Complexes (M = Mo, W; X, Y = Cl, Br, I)

Resonance Raman spectra of the cubic metal-halide complexes having the general formula [M(6)X(8)Y(6)](2)(-) (M = Mo or W; X, Y = Cl, Br, or I) are reported. The three totally symmetric fundamental vibrations of these complexes are identified. The extensive mixing of the symmetry coordinates that compose the symmetric normal modes expected in these systems is not observed. Instead the "group-frequency" approximation is valid. Furthermore, the force constants of both the apical and face-bridging metal-halide bonds are insensitive to the identity of either the metal or the halide. Raman spectra of related complexes with methoxy and benzenethiol groups as ligands are reported along with the structural data for [Mo(6)Cl(8)(SPh)(6)][NBu(4)](2). Crystal data for [Mo(6)Cl(8)(SPh)(6)][NBu(4)](2) at -156 degrees C: monoclinic space group P2(1)/c; a = 12.588(3), b = 17.471(5), c = 20.646(2) ?; beta = 118.53(1) degrees, V = 3223.4 ?(3); d(calcd) = 1.664 g cm(-)(3); Z = 2.     

The preparations and properties of tris(perfluoroorgano)bismuth compounds Bi(Rf)3 (Rf = CF3, C2F5, n-C3F7, n-C4F9, n-C6F13, n-C8 F17, C6F5)

Tris(perfluoroorgano)bismuth compounds Bi(R_f)₃ (R_f = CF₃, C₂F₅, n-C₃F₇, n-C₄F₉, n-C₆F₁₃, n-C₈F₁₇, C₆F₅) are easily prepared in high yields from the reactions of perfluoroorganocadmium complexes with BiCl₃, or BiBr₃ in aprotic solvents. The perfluoroorganobismuth halides intermediates in these reactions have been detected by NMR spectroscopy.     

Thermodynamik und Kinetik der Xa-Substitution bei den Komplexen [W6Cl8]X6a(2−) und [Mo6Cl8]X6a(2−) (X = Cl,Br, J)

Thermodynamics and Kinetics of the X^a-Substitution of [W₆Cl₈]X₆^a(2?) and [Mo₆Cl₈]X₆^a(2?) Complexes; (X = Cl, Br, I) The title subject has been investigated in different solvent mixtures (see “Inhaltsübersicht”). In some cases the progress of the reaction has been followed by an emf method; in most cases the reaction was stopped after definite times by precipitation of the oxiniumsalts. Thermodynamics. For equilibria of the type (a) one finds the constant \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm C} = \frac{{[{\rm Br}^{\rm a} ][{\rm Cl}^ - ]}}{{[{\rm Cl}^{\rm a} ][{\rm Br}^ - ]}} $\end{document}, where [Br^a] and [Cl^a] mark the total number of Br or Cl occupying X^a-positions of the complex. The X^a-positions are thermodynamically equivalent, the substitution proceeds statistically, so that the steps of reaction (a) with the equilibrium constants K₁ to K₆ are given by \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm K} = \frac{{{\rm W}({\rm hin})}}{{{\rm W}({\rm r\ddot uck})}} \cdot {\rm C} $\end{document} if W(hin) and W(rück) describe the probability of the forward and the back reaction. Similarly in some simple complexes (e. g. Irx₆^2?);PdX₄^2? the statistical effect plays a dominating role. The kinetics may be described as (b) The aquotation step is rate determining. Consequently the reaction of the first order. Rate constants for the forward and the reversed reaction between 0 and 25°C have been measured. The activation energy is ≈ 18 kcal. With the molybdenum complexes the X^a-substitutions is about 10 times faster as with the tungsten complexes.     

Syntheses and structures of Tetranuclear Cluster complexes of molybdenum [Mo4(μ3-S)2(μ2-S)4 X 2-(PMe3)6] (X = SH,Cl, Br,I, SCN) and [Mo4(μ3-S)2-(μ2-S)4 (dtc)2(PMe3)4] (dtc = diethyldithiocarbamate)

A molybdenum cluster complex [Mo₄(μ₃-S)₂(μ₂-S)₄)(SH)₂(PMe_{3 6}] has been synthesized by the reaction of (NH₄)₂Mo₃S₁₃ with trimethylphosphine. The cluster core is composed of four molybdenum atoms arranged in the rhombus bridged by two capping and four bridging sulfur atoms. Two SH and six tri-methylphosphine ligands are coordinated to the terminal positions. The mean oxidation stares of molybdenum is +3.5 and there are five Mo-Mo bonds consistent with ten metal cluster electrons. The complex has been converted into [Mo₄(μ₃-S)₂(μ₂-S)₄ X ₂(PMe₃)₆] (X=Cl, Br, I, SCN) and [Mo₄μ₃-S₂(μ₂-S)₄ (die)₂(PMe₃)₄] (dtc - diethyldithiocarbamate). In the case of the dtc complex, two terminal trimetlaylphosphine ligands are displaced and dtc ligands are coordinated in chelate fashion. The structures of the SH, Cl, Br, and dtc complexes have been determined by X-ray crystallography. Molecular orbital calculations with DV-Xα method has shown large HOMO-LUMO gaps (1.52-1.74eV) for [Mo₄S₆ X ₂(PH₃)₄] (X= SH, Cl, and Br).     

Die Dihydrate [Me6X]X · 2H2O mit Me = Mo,W; X = Cl,Br, J

The dihydrates mentioned in the title are particularly suitable for the characterisation of the [Me₆X] complex groups. Reported are the preparation of known and unknown compounds of this type. Lattice constants are given. The compounds are isotypic with the known structure of [Mo₆Br₈]Br₄ · 2 H₂O. Moreover, infrared data and the thermal decomposition of the compounds are reported.     

Mechanism of CO exchange on cis-[M(CO)2X2]- complexes (M=Rh,Ir;X=Cl, Br, or I)

The CO exchange on cis-[M(CO)2X2]- with M = Ir (X = Cl, la; X = Br, 1b; X = I, 1c) and M = Rh (X = Cl, 2a; X = Br, 2b; X = I, 2c) was studied in dichloromethane. The exchange reaction [cis-[M(CO)2X2]- + 2*CO is in equilibrium cis-[M(*CO)2X2]- + 2CO (exchange rate constant: kobs)] was followed as a function of temperature and carbon monoxide concentration (up to 6 MPa) using homemade high gas pressure NMR sapphire tubes. The reaction is first order for both CO and cis-[M(CO)2X2]- concentrations. The second-order rate constant, k2(298) (=kobs)[CO]), the enthalpy, deltaH*, and the entropy of activation, deltaS*, obtained for the six complexes are respectively as follows: la, (1.08 +/- 0.01) x 10(3) L mol(-1) s(-1), 15.37 +/- 0.3 kJ mol(-1), -135.3 +/- 1 J mol(-1) K(-1); 1b, (12.7 +/- 0.2) x 10(3) L mol(-1) s(-1), 13.26 +/- 0.5 kJ mol(-1), -121.9 +/- 2 J mol(-1) K(-1); 1c, (98.9 +/- 1.4) x 10(3) L mol(-1) s(-1), 12.50 +/- 0.6 kJ mol(-1), -107.4 +/- 2 J mol(-1) K(-1); 2a, (1.62 +/- 0.02) x 10(3) L mol(-1) s(-1), 17.47 +/- 0.4 kJ mol(-1), -124.9 +/- 1 J mol(-1) K(-1); 2b, (24.8 +/- 0.2) x 10(3) L mol(-1) s(-1), 11.35 +/- 0.4 kJ mol(-1), -122.7 +/- 1 J mol(-1) K(-1); 2c, (850 +/- 120) x 10(3) L mol(-1), s(-1), 9.87 +/- 0.8 kJ mol(-1), -98.3 +/- 4 J mol(-1) K(-1). For complexes la and 2a, the volumes of activation were measured and are -20.9 +/- 1.2 cm3 mol(-1) (332.0 K) and -17.2 +/- 1.0 cm3 mol(-1) (330.8 K), respectively. The second-order kinetics and the large negative values of the entropies and volumes of activation point to a limiting associative, A, exchange mechanism. The reactivity of CO exchange follows the increasing trans effect of the halogens (Cl < Br < I), and this is observed on both metal centers. For the same halogen, the rhodium complex is more reactive than the iridium complex. This reactivity difference between rhodium and iridium is less marked for chloride (1.5: 1) than for iodide (8.6:1) at 298 K.     

Trigonal-planare CuX3-Gruppen in Cu2Mo6X14, X = Cl,Br, I

Trigonal Planar CuX₃-Groups in Cu₂Mo₆X₁₄, X = Cl, Br, I Cu₂Mo₆Cl₁₄ (I), Cu₂Mo₆Br₁₄ (II) and Cu₂Mo₆I₁₄ (III) were synthesized by thermal treatment of corresponding mixtures of copper(I) and molybdenum(II) halides. The crystal structures were determined by single crystal X-ray analyses. I and II show isotypism, cubic, Pn3 (no. 201, sec. setting), Z = 4, I: a = 12.772(3) Å, II: a = 13.350(2) Å. III shows a new structural type, orthorhombic, Pbca (No. 61), Z = 4, a = 16.058(3) Å, b = 10.643(2) Å, c = 16.963(3) Å. Trigonal planar CuX₃ units were found in I? III. Structural behaviour relations are discussed, especially with regard to ionic conductivity.     

Influence of the ligand on the coupling between the metal-based electrons in face-shared [M2X9]3- (M = Mo,W; X = F,Cl, Br,I) systems

Orbital overlap and spin polarization effects in Mo and W [M(2)X(9)](3)(-) halide and in [M(2)X'(3)X' '(6)](3)(-) mixed-halide systems have been investigated by means of density-functional calculations performed on the S = 0, S = 3, and reference states of these species. For the regular [M(2)X(9)](3)(-) systems, a strong linear correlation between the two factors has been obtained, and decreasing trends in both the overlap energy and the spin polarization energy upon descending the halide group have been observed. These trends can be related to the changes in the size and covalency of the ligands and in the nature of the metal-bridge interaction. For the mixed-ligand [M(2)X'(3)X' '(6)](3)(-) systems, important deviations (from the behavior of the regular systems), which are apparently the result of particular structural and energetic characteristics, have been observed.     

Reactivity of [Mo(NHNRPh)(NNRPh)(acac)X2] (R=Ph,Me; X=Br,I) toward tertiary phosphines

The reactivity of mixed [organohydrazido(1-)][organohydrazido(2-)]molybdenum(VI) complexes [Mo(NHNRPh)(NNRPh)(acac)X₂] {R?=?Ph, X?=?Br (1); R?=?Ph, X?=?I (2) and R?=?Me; X?=?I (3)} with tertiary phosphines as PPh₃, PMePh₂ and PMe₂Ph are examined. The syntheses of [Mo(NNPh₂)₂Br₂(PPh₃)] (4), [Mo(NNPh₂)₂Br₂(PMePh₂)₂] (5), [Mo(NNPh₂)₂Br₂(PMe₂Ph)₂] (6), [Mo(NNPh₂)₂(acac)I(PPh₃)] (7), [Mo(NNPh₂)₂(acac)(PMePh₂)₂]⁺I^? (8) and [Mo(NNMePh)₂(acac)(PMePh₂)₂]⁺I^? (9) are reported. All complexes were characterized by elemental analysis, UV-visible, IR, ¹H and ³¹P{H} NMR spectroscopy.     

Darstellung,Kristallstruktur und spektroskopische Eigenschaften der Clusteranionen [(Mo6Br)X]2− mit Xa = F,Cl, Br,I

Synthesis, Crystal Structure and Spectroscopic Properties of the Cluster Anions [(Mo₆Br )X ]^2? with X^a = F, Cl, Br, I The tetrabutylammonium (TBA), tetraphenylphosphonium (TPP) and tetraphenylarsonium (TPAs) salts of the octa-μ₃-bromo-hexahalogeno-octahedro-hexamolybdate(2?) anions [(Mo₆Br)X]^2? (X^a = F, Cl, Br, I) are synthesized from solutions of the free acids H₂[(Mo₆Br)X] · 8 H₂O with X^a = Cl, Br, I. The crystal structures show systematic stretchings in the Mo? Mo bond length and a slight compression of the Brⁱ₈ cube in the F^a to I^a series. The cations do not change much. The i.r. and Raman spectra show at 10 K almost constant frequencies of the (Mo₆Brⁱ₈) cluster vibrations, whereas all modes with X^a ligand contribution are characteristically shifted. The most important bands are assigned by polarization measurements and the force constants are derived from normal coordinate analysis. The ⁹⁵Mo nmr signals are shifted to lower field with increasing electronegativity of the X^a ligands. The fluorine compound shows a sharp ¹⁹F nmr singlet at ?184.5 ppm.     

Reactions of halogens with platinum(IV) triamine complexes [PtEnPyX3]X (X = Cl, Br)

Platinum(IV) complexes of the tetramine type [PtEnPy₂X₂]X₂ · H₂O (X = Cl, Br) have been found to lose a coordinated pyridine molecule at 125–135°C, thereby transforming into triamines [PtEnPyX₃]X. The complex [PtEnPyCl₃]NO₃ has been isolated. Dissolution of the product of [PtEnPy₂Cl₂]Cl₂ chlorination in HCl results in complete destruction of the five-membered chelate ring. The complex [Pt(NH₃)₂Py₂Cl₂](NO₃)₂ has been isolated. A number of compounds have been studied by X-ray diffraction: [PtEnPy₂Cl₂]Cl₂ · 2H₂O (I) (monoclinic, space group P2₁/c, a = 15.418(2) Å, b = 9.203(1) Å, c = 13.762(3) Å, β = 104.18(2)°, Z = 4, R _hkl = 0.25), [PtEnPyCl₃]NO₃ (II) (monoclinic, space group P2₁/c, a = 8.194(1) Å, b = 8.846(1) Å, c = 19.855(2) Å, β = 97.10(1)°, Z = 4, R _hkl = 0.048), and [Pt(NH₃)₂Py₂Cl₂](NO₃)₂ (III) (orthorhombic, space group Pbca, a = 12.316(2) Å, b = 13.250(3) Å, c = 21.868(4) Å, Z = 8, R _hkl = 0.027). The reaction of [PtEnPyBr₃]Br with bromine gives the polybromide [PtEnPyBr₃]Br · Br₂ · 0.5 H₂O. The chlorination of [PtEnPyCl₃]Cl gives the chloramine complex [Pt(NH₂-CH₂-NH(Cl)PyCl₃]Cl · H₂O.     

Vibrational studies of [Ni(II)(DIARS)2X]X, (DIARS=o-C6H4(As(CH3)2)2 and X=Cl, Br, I).

Infrared and laser Raman spectra of [Ni(II)(diars)2X]X, (X=Cl, Br and I) have been used as probes to determine the structures of chelated diarsine molecules. It has been observed that the effects of metal chelation and coordination geometry give rise to frequency shifts in these complexes. The variation in vibrational spectroscopic features indicates reduction in the symmetry of the complexes in the crystalline environment. The effect of halogen on the Ni-halogen stretching frequency of these square pyramidal complexes is not as significant as observed in the case of octahedral complexes.