Mo-Mo Bond Research Articles

RESEARCH ON TRINUCLEAR MOLYBDENUM CLUSTER COMPOUNDS——CRYSTAL AND MOLECULAR STRUCTURE OF Mo 3 (μ 3 —O)(μ 2 —S 2 ) 3 [S 2 P(OEt) 2 ] 3 I

The title crystals are golden yellow rhomboic plates, belonging to the monoelinic system. The space group is P_(B_1)/n with unit cell parameters a=16.570(2), b=12.370(1), c=20.007(2), β=99.97(1)°, Z=4, D_c=1.938 g.cm~(-3). The crystal structure was solved mainly by the heavy atom method and refined by the full-matrix least-squares to a final R factor of 0.047 based on 4387 unique reflections with intensities I≥2σ(I). The results show that the crystal structure consists of neutral mono-oxo-capped trinuclear molybdenum cluster molecules with an average Mo-Mo bond length of 2.626(4) and an average Mo-O bond length of 2.036(2) respectively. Each pair of Mo atoms is further bridged by an S_2~(2-) radical, in which one S atom is essentially situated on the triangular plane formed by these three Mo atoms and the other one is situated on the side of the plane opposite to the μ_3-O atom. Besides, each Mo atom is coordinated to two S atoms belonging to an [S_2P(OEt)_2]~-radical so as to complete a nearly pentagonal bipyramidal coordination. In addition, on top of the three out-of-plane S atoms one I atom bridges these three S atoms so that a part of the atoms in the cluster entity forms a distorted pseudo-cubic configuration.

RESEARCH ON TRINUCLEAR MOLYBDENUM CLUSTER COMPOUNDS——CRYSTAL AND MOLECULAR STRUCTURES OF (Et 4 N) 2 [Mo 3 (μ 3 -O)(μ 2 -Cl) 3 (Oac) 2 Cl 5

The title compound forms black crystals shaped like pseudo-octahedrons, which belong to the orthorhombic system The space group is Pna 2_1 with unit cell parametrs of a=17.815(1), b=16.629(2), c=12.003(1), and with Z=4, D_(obs)=1.80g·cm~(-3), and D_(calc)=1.804g·cm~(-3). The crystal structure was solved by the heavy atom method and refiened by fullmatrix least-squares to a final conventional R factor of 0.048 for 2584 unique reflections with I≥σ(Ⅰ). The investigation confirms that the crystal structure consists of tetraethylammonium cations and trinuclear Mo cluster anions. The anion is a μ_3-O monocapped trinuclear cluster with an average Mo-Mo bond length of 2.60 (2). On the side of the Mo_3 triangular plane opposite to the μ_3-O atom, each two Mo atoms are bridged by a Cl atom with the result that these seven atoms (3 Me, 1 O and 3 Cl atoms)form an apex-deficient quasicubane configuration. In addition, each Mo atom is coordinated to three additional atoms resulting in a pseudo-octahedral geometry around each metal center. These additional ligating atoms arise from two acetic radicals and five Cl atoms. The two O atoms of each acetic radical are attached to two ajacent Mo atoms respectively. As a whole, the cluster anion approaches the symmetry Cs.

Synthesis, crystal structures, and properties of lithium zinc molybdenum oxide (LiZn2Mo3O8), zinc molybdenum oxide (Zn3Mo3O8), and scandium zinc molybdenum oxide (ScZnMo3O8), reduced derivatives containing the Mo3O13 cluster unit

The new compounds LiZn/sub 2/Mo/sub 3/O/sub 8/(I), Zn/sub 3/Mo/sub 3/O/sub 8/(II), and ScZnMo/sub 3/O/sub 8/(III) containing the reduced cluster units Mo/sub 3/O/sub 13/ have been prepared and characterized by structure determination, magnetic susceptibilities, and infrared spectra. I and II are isomorphous and hexagonal and have space group R anti 3m, Z = 6, with a = 5.8116 (6) A, c = 31.013 (8) A and a = 5.8617 (4) A, c = 31.100 (3) A, respectively. From X-ray powder diffraction data III is hexagonal with a = 5.8050 (7) A, c = 9.996 (3) A, and Z = 2 and is isomorphous with Zn/sub 2/Mo/sub 3/O/sub 8/. I and III are paramagnetic with moments appropriate for one unpaired electron per cluster. A fit of data for I to the equation (chi/sub M/ - chi/sub TIP/)/sup -1/ = (T-theta)C/sup -1/ over the range 94-300 K gives theta = -350 (10) K, C = 0.279 (5), and ..mu.. = 1.49 (2) ..mu../sub B/. Structure refinements of I and II give Mo-Mo bond distances of 2.578 (1) and 2.580 (2) A, respectively, for the Mo/sub 3/O/sub 13/ cluster units, which may be compared to 2.254 (2) A in Zn/sub 2/Mo/sub 3/O/sub 8/. Changesmore » in the Mo-Mo and Mo-O distances upon reduction of Zn/sub 2/Mo/sub 3/O/sub 8/ to I and II are discussed in terms of population of a weakly antibonding MO of a/sub 1/ symmetry and the effects of Mo-O ..pi.. bonding, especially that involving the O atoms bridging the edges of the Mo/sub 3/ triangle. 31 references, 4 figures, 8 tables.« less

Anionische Komplexe [Mo2(O2CPh)4X2]2⊖ mit X = N3, Cl, Br. Die Kristallstruktur von (PPh4)2[Mo2(O2CPh)4Cl2] · 2CH2Cl2 / Anionic Complexes [Mo2(O2C-Ph)4X2]2⊖ with X = N3, Cl, Br. The Crystal Structure of (PPh4)2[Mo2(O2C-Ph)4Cl2] · 2CH2Cl2

The syntheses and IR spectra of the complexes [Mo2(O2C-Ph)4X2]2⊖ with X = N3, CI, Br and the counter ion PPh4 ⊕ are reported. The azido and the bromo complexes are obtained from a solution of [Mo2(O2CPh)4] with PPh4N3 in pyridine or by reaction with PPh4Br in CH2Br2, respectively. When (PPh4)2[Mo2(O2CPh)4(N3)2] is dissolved in CH2Cl2, nitrogen is evolved and the complex with X = CI is obtained. The crystal structure of (PPh4)2[Mo2(O2CPh)4Cl2] · 2CH2Cl2 was determined from X-ray diffraction data (5676 observed independent reflexions, R = 0.042). It crystallizes in the monoclinic space group P21/n with four formula units per unit cell; the lattice constants are a = 1549, b = 1400, c = 1648 pm, β = 94.6°. The centrosymmetric [Mo2(O2CPh)4Cl2]2⊖ ion has a rather short Mo-Mo bond of 213 pm, whereas the MoCl bonds are very long (288 pm)

Metal complexes of fluorophosphines. 13. Reaction of fac-tris(acetonitrile)molybdenum tricarbonyl (fac-(CH3CN)3Mo(CO)3) with (methylamino)bis(difluorophosphine). X-ray crystal structure analysis of a novel binuclear molybdenum fluorophosphine carbonyl complex with a bridging chlorine atom: (CO)2Mo[.mu.-CH3N(PF2)2]2(.mu.-PF2)(.mu.-Cl)Mo(CO)(PF2NHCH3)

Reaction of fac-(CH/sub 3/CN)/sub 3/Mo(CO)/sub 3/ with CH/sub 3/N(PF/sub 2/)/sub 2/ in acetonitrile solution at room temperature gives white, volatile, crystalline fac-(CH/sub 3/N(PF/sub 2/)/sub 2/)/sub 2/Mo(CO)/sub 3/, containing one monodentate and one bidentate CH/sub 3/N(PF/sub 2/)/sub 2/ ligand. The same reactants in boiling acetonitrile give yellow (CH/sub 3/N(PF/sub 2/)/sub 2/)/sub 4/Mo/sub 2/(CO)/sub 3/ in considerably better yield than the previously reported preparation of this binuclear complex from the cycloheptatriene complex C/sub 7/H/sub 8/Mo(CO)/sub 3/ and CH/sub 3/N(PF/sub 2/)/sub 2/ in boiling methylcyclohexane. Reaction in acetonitrile solution of fac-(CH/sub 3/CN)/sub 3/Mo(CO)/sub 3/ with CH/sub 3/N(PF/sub 2/)/sub 2/ containing about 0.2% HCl gives brown-red, volatile (CO)/sub 2/Mo(/sup +/-CH/sub 3/N(PF/sub 2/)/sub 2/)/sub 2/(..mu..-PF/sub 2/)(..mu..-Cl)-Mo(CO)(PF/sub 2/NHCH/sub 3/), whose composition and structure were established by single-crystal X-ray structure analysis. This novel quadruply bridged binuclear complex is obtained in considerably better yield from the reaction of (CH/sub 3/N(PF/sub 2/)/sub 2/)/sub 3/Mo/sub 2/(CO)/sub 5/ with ((C/sub 2/H/sub 5/)/sub 3/NH)Cl in acetonitirle solution. The complex has a Mo-Mo bond 2.975 A in length. Crystal data: monoclinic, space group P2/sub 1//c, a = 17.546 (4) A, b = 9.725 (2) A, c = 14.558 (3), ..beta.. = 107.20 (2)/sup 0/, Z = 4. 30 references, 2 figures, 3 tables.

The arsenate ion as an intra- and inter-molecular bridging ligand: Crystal structure and spectroscopic studies of the tetrakis(Hydrogen arsenato)dimolybdenum(III) ion

Dimolybdenum tetraacetate Mo2 (OAc)4 reacts with concentrated solutions of arsenic acid in air to form [Mo2(HAsO4)4]2− and some related ions which can be isolated with caesium or pyridinium cations: Cs2[Mo2(HAsO4)4]3 H2O (1), (C5NH6)3[Mo2(HAsO4)Cl] (2), (C5NH6)3 [Mo2(HAsO4)4Br] (3) and (C5NH6)2[Mo2(HAsO4)4]2H2O (4). The four compounds are stable indefinitely in air at room temperature. The last compound has been fully characterized structurally. It crystallizes in the space group P21/a witha = 11.057(2)A,b = 10.720(2)A,c = 10.303(4)A, β = 91.56(3)°, V = 1220.8(6)A3 and Z = 2. Interestingly, the overall structure can be described in terms of molybdenum-containing layers stacked in the c direction, in which arsenato ligands equatorially coordinating the Mo26+ unit play the role of an axial ligand for the next closest unit. The [Mo2(HAsO4)4]2− ion has a paddlewheel structure very similar to that of [Mo2(HPO4)4]2− and [Mo2(SO4)4]4−, 3−. The length of the Mo-Mo triple bond of (4) is 2.265(1)A. Comparing the HPO42− and HAsO42− complexes, the electronic spectra have been found to be very similar, but the Raman spectra show a noticeable decrease of frequency from phosphato to arsenato-complexes for the Mo-Mo stretching modes. This decrease may come from a mechanical coupling between HAsO42− deformation modes and ν(Mo-Mo) and ν(Mo-O) vibrations, but is more likely due to a weakening of the Mo-Mo bond strained by the bridging ligand.

The formation of a cyclohexadienone at a dimolybdenum centre; X-ray crystal structure of [Mo2(µ-{η4-CMe2·CH·CH·CH·C(But)CO})-(CO)2(η-C5H5)2], and evidence for an unusual bonding mode for a bridging 1,3-diene ligand

Reaction of [Mo2(CO)4(µ-CH·CH·CMe2)(η-C5H5)2] with ButC2H affords [Mo2(µ-{η4-[graphic omitted]O})(CO)2(η-C5H5)2] containing a bridging 1,3-diene ligand with an unusual bonding mode and an η3-allylic complex in which the Mo-Mo bond has been broken, whereas but-2-yne afords only the η3-allylic type of complex, and C2(CO2Me)2 gives a vinyl substituted µ-allylidene complex.

The sequential linking of alkynes at dichromium and dimolybdenum centres; X-ray crystal structure of [Cr2(CO)(µ-C4Ph4)(η-C5H5)2

In heptane at reflux, the alkynes RCCR (R = Ph, H, or CO2Me) react with [Cr2(CO)4(η-C5H5)2] to give complexes [Cr2(CO)(µ-C4R4)(η-C5H5)2]. An X-ray diffraction study on the product from PhCCPh shows that the crystals of [Cr2(CO)(µ-C4Ph4)(η-C5H5)2] when grown from dichloromethane–hexane incorporate ¼CH2Cl2 per molecule of complex and are orthorhombic, with Z= 8 in a unit cell of dimensions a= 19.569(4), b= 19.731(5), c= 16.637(2)A, and space group Pbcn(no. 60). The structure has been solved by heavy-atom methods from 3 166 data for which l 3.0σ(l), collected on a four-circle diffractometer, and refined to R 0.066. The axis of the molecule comprises a (η-C5H5)CrCr(η-C5H5) moiety which is non-linear, with the cyclopentadienyl rings in an unsymmetrical trans relationship to one another, and with a carbonyl ligand semi-bridging in a plane which is effectively a mirror plane for the whole molecule. Two PhCCPh molecules have joined to form a four-carbon chain, of which the two terminal atoms form a quasi-tetrahedral group with the two chromium atoms [CrCr 2.337(2), Cr–C 2.025(7) mean, C ⋯ C(non-bonded)ca. 2.7 A], and the two central atoms are π-bonded to that Cr atom which does not carry the carbonyl ligand. The two metal atoms lie on opposite sides of the plane through the four-carbon portion of the CrC4Ph4 ring. The alkynes RCCH (R = Ph or Me) react with [Cr2(CO)4(η-C5H5)2] to yield as major products the complexes [Cr2(CO)(η-C4H2R2)(η-C5H5)2] in which there is a head-to-tail arrangement of the Ph or Me groups in the C4Cr rings. However, with phenylacetylene the isomer containing the ring system [graphic omitted]Ph was also detected. The compounds [Mo2(CO)n(η-C5H5)2](n= 4 or 6) react with PhCCPh in octane at reflux to give [Mo2(CO)(µ-C4Ph4)(η-C5H5)2], and similarly [Mo2(CO)4(η-HC2H)(η-C5H5)2] affords [Mo2(HC2H)(PhC2Ph)2(η-C5H5)2], a ‘fly-over’ complex containing a six-carbon chain bridging a MoMo bond. Reaction of [Mo2(CO)4(η-HC2H)(η-C5H5)2] with RCCR (R = CO2Me) yields the complexes [Mo2(CO)2(µ-C6H2R4)(η-C5H5)2](two isomers) and [Mo2(η-C8H2R6)(η-C5H5)2](two isomers) in which C6 and C8 chains bridge Mo–Mo and MoMo bonds respectively. The structures of these species were deduced from 1H and 13C n.m.r. spectra. Reaction of [Mo2(CO)4(µ-RC2R)(η-C5H5)2] with RCCR (R = CO2Me) gives [Mo2(CO)2(µ-C6R6)(η-C5H5)2] and [Mo2(µ-C8R8)(η-C5H5)2](two isomers), characterised inter alia by their 1H and 13C n.m.r. spectra. Treatment of [Mo2(HC2H)(PhC2Ph)2(η-C5H5)2] with MeO2CCCCo2Me gives two isomers of compositon [Mo2(HC2H)(PhC2Ph)2(MeO2CC2CO2Me)(η-C5H5)2], thereby establishing that the complexes with four linearly linked alkynes are formed from the species with three such linked groups. Possible mechanisms for carbon-chain growth on the dichromium and dimolybdenum centres are discussed and are related to the changes in multiplicities of the metal–metal bonds.

Trimolybdenum cluster compounds with two capping ethylidyne groups

Three Compounds containing equilateral-triangular trimolybdenum clusters capped on both sides by ethylidyne (CCH3) groups are described: (I) , [MO~(CCH~)~(~~CCH~)~(H~~)~] (CF3S03)2 (2), and [MO~(CCH~)~(~~CCH~)~(H~~)~](P-CH~C~H~S~~)~~~OH~~ (3). All three are obtained by suitable workup of the reaction mixture after refluxing M o ( C O ) ~ with a 1O:l v/v mixture of acetic acid and acetic anhydride. For the last two permanganate oxidation is used. The crystal structures of the three compounds have been solved and refined. In 1, where there are five electrons for the M o ~ cluster, the Mo-Mo bond orders are 5 / 6 and the mean Mo-Mo distance is 2.814 ( 5 ) A; this is about 0.06 A longer than that in a closely related cluster with Mo-Mo bond orders of 1.0. In 2 and 3, which each contain a bicapped M o ~ cluster with only four electrons, and hence a bond order of 2/3, the mean Mo-Mo distances are 2.883 (1) 8, and 2.892 (1) A, Le., about 0.13 A longer than for the Mo-Mo bonds of order 1.0. The cation in 1 has one unpaired electron showing an essentially constant g factor slightly above 2.0 in the range 4-300 K according to bulk susceptibility measurements. It shows no EPR spectrum but has a sharp 360-MHz IH NMR spectrum in which the resonance of the 02CCH3 protons is shifted to 14 ppm downfield while that of the CCH3 protons is broadened and shifted 85 ppm downfield. The cations in 2 and 3 appear to be paramagnetic, but the temperature dependence is unusual and still under study. The cation gives an 'H NMR spectrum with lines at 15.6 and 27.1 ppm with relative intensities of 3.3 to 1.0.

SCF-SW-Xα Calculations on molybdenum—halogen cluster compounds

The electronic structures of the cluster cations Mo 6 X 4+ 8 (X = F, Cl, Br, I) have been calculated using the SCF—SW—Xα method. The eigenvalue spectra obtained are discussed and compared with results of other quantum-chemical studies of such systems. The results of population analysis are used to discuss the charge distribution in the clusters studied. A qualitative discussion of the Mo-Mo and Mo-X bond strengths is also presented. Finally, calculated bond energies are compared with adsorption energies.

An Easily Prepared, Air‐Stable Compound with a Triple Metal‐to‐Metal (MoMo) Bond

A “simple” fourfold bridged MoMo triple bond is present in the purple-red complex (1) which is formed by slow mixing of the reactants listed below. “Simple” MM bonds do not contain δ bonding (σ4 π4).

The molybdenum iodide cluster anion undecaiodotetramolybdate(2-). A new cluster type structurally related to the octaiodohexamolybdenum(4+) octahedral cluster

Crystalline ((n-Bu)/sub 4/N)/sub 2/Mo/sub 4/I/sub 11/ has been prepared in high yield. Synthesis is described elsewhere. From data obtained at -75/sup 0/C with MoK ..cap alpha..-radiation, the cell parameters are a = 19.99(3), b = 12.49(3), c = 23.67(2)A; ..cap alpha.. = 89.89(6), ..beta.. = 105.80(5), and ..gamma.. = 90.27(8)A; z = 4, P/sub 1//sup -/. The structure is described from two perspectives. (1) It is viewed as a severely distorted tetrahedral cluster of molybdenum atoms bridged on two faces by triply bridging iodine atoms, and on five edges by doubly bridging iodine atoms. The coordination sphere of each Mo atom is completed by one bond attached to a terminal I atom so that each metal atom attains the coordination number 8- by bonding to five I atoms and three Mo atoms. The anion has approximate C/sub 2v/ symmetry. Bond lengths and bond angles are included. (2) The structure may also be considered to be a fragment of the octahedral cluster Mo/sub 6/X/sub 8//sup 4 +/ by removing two adjacent Mo atoms from the Mo/sub 6/ octahedron and one I atom from the I/sub 8/ cube. The I atom remaining on the cube edge adjacent to the positions of themore » two removed Mo atoms is then shifted to the midpoint of that edge, and becomes the unique atom which bridges the long Mo-Mo bond. Bond lengths are compared with compounds which exhibit similar structure.« less

Preparative and structural studies of halodimolybdates (II), III. Crystal and molecular structure of bis(4-methylpyridinium)hexaiododiaquo-dimolybdate(II)

The title compound (C6H8N)2Mo2I6(H2O)2 crystallizes in theP¯1 space group, witha = 8.127(3),b = 8.337(3),c = 10.415(4) A, α = 73.99(2), β = 84.35(2), γ = 73.91(2) ° andZ = 1. The structure was solved by direct methods and refined to the unweighted and weighted residuals of 0.044 and 0.052. The structure is characterized by the eclipsed configuration of the iodide ions and water molecules within Mo2I6(H2O) 2 2− ion and very short Mo-Mo bond distance 2.115(1) A. Three independent Mo-I distances are 2.784(1), 2.760(2) and 2.797(1) A. 4-Methylpyridinium ion is planar within 0.02° A. The compound is isostructural with (C6H8N)2Mo2Br6(H2O)2.