Sn4.4Mo24O38

The single‐crystal structure of tetratin tetracosa­molybdenum octatriaconta­oxide, Sn_4.4Mo₂₄O₃₈, contains infinite chains of centrosymmetric dioctahedral Mo₁₀ and centrosymmetric trioctahedral Mo₁₄ clusters. These clusters, as well as the O atoms, the arrangement of which derives from a closest‐packing with the layer sequence …ABAC…, form sheets parallel to the ac plane of the monoclinic unit cell. The Mo—Mo distances range from 2.6225 (7) to 2.8212 (9) Å and from 2.6270 (7) to 2.8365 (7) Å in the Mo₁₀ and Mo₁₄ clusters, respectively. The Mo—O distances vary between 1.949 (4) and 2.151 (4) Å in the Mo₁₀ cluster and between 1.938 (4) and 2.140 (4) Å in the Mo₁₄ cluster. The three crystallographically independent Sn²⁺ ions are off the centre of distorted oxy­gen octahedra.     

New girdle‐like Mo18 polyanions linked into chains

From the reduction of heptamolybdate, a polyoxomolybdate was obtained with the formula [Na(H₂O)₁₆(NH₂CH₂­COO)]⁴⁺·{Na⁺[H₉MoMoO₅₆(NH₂CH₂COO)]^5?}^4?­·20H₂O, i.e. hepta­sodium nona­hydrogen tetra­car­bam­ate hexa­deca­aqua­hexa­penta­conta­oxa­octa­deca­molyb­date(V,VI) icosa­hydrate. The 18 Mo atoms are connected by bridging O atoms to form a centrosymmetric girdle‐like structure, in which Mo^V–Mo^V units are found. An Na⁺ cation occupies the central hole of the girdle, while four Na⁺ cations are bonded to the O atoms on the girdle edge. The girdles are linked into a one‐dimensional chain by the other Na⁺ cations.     

The First Titanium Molybdenum Antimonide: Ti5.42Mo2.58Sb9, a Substitution Variant of Zr2V6Sb9

The new ternary antimonide Ti_5.42(2)Mo_2.58Sb₉ was uncovered by a reaction of the elements under exclusion of air at 1150 °C. It crystallizes in a ternary substitution variant of the V_7.5Sb₉ type, a structure not known to exist in either the Ti/Sb or the Mo/Sb system. The crystal structure of Ti_5.42Mo_2.58Sb₉ was determined from single crystal X‐ray data: space group P4/nmm, with a = 9.8178(8) Å, c = 7.1857(8) Å, V = 692.6(1) ų, Z = 2, R1 = 0.025, wR2 = 0.052 (all data). The structure contains four metal atom sites, two thereof occupied solely by Ti atoms, and two by different Ti/Mo mixtures. The former two correspond to the Zr sites, and the latter two to the V sites of the isostructural antimonide Zr₂V₆Sb₉. The crystal structure is comprised of chains of face‐sharing TiSb₈ square antiprisms, Ti/Mo tetrahedra and Sb atom pairs and squares. The electronic structure, computed with the LMTO approximation, is indicative of metallic properties. In addition to the dominating metal–Sb bonds, strong metal–metal and Sb–Sb bonds exist as well in Ti_5.42Mo_2.58Sb₉. The Mo content per metal site increases with increasing metal–metal interactions.     

Non-Dissociative Activation of Chemisorbed Dinitrogen on One or Two Vanadium Atoms Supported by a Mo6S8 Cluster

Adsorption of N₂ on Mo₆S₈^q_V_x clusters (x=0, 1, 2; q=0, ±1) were systematically studied by density functional theory calculations with dispersion corrections. It was found that the N₂ can be chemisorbed and undergo non-dissociative activation on single or double metal atoms. The adsorption and activation are influenced by metal types (V or Mo), N₂ coordination modes and charge states of the clusters. Particularly, anionic Mo₆S₈⁻_V₂ clusters have remarkable ability to fix and activate N₂. In Mo₆S₈⁻_V₂, two V atoms prefer to adsorb on two adjacent S−Mo−S hollow sites, leading to the formation of a supported V…V unit. The N₂ is bridged side-on coordinated with these two V atoms with high adsorption energy and significant charge transfer. The bond order, bond length and vibration frequency of the adsorbed N₂ are close to those of a N−N single bond.     

Cs2Mo15S19: a novel ternary reduced molybdenum sulfide containing Mo6 and Mo9 clusters

The crystal structure of dicaesium pentadecamolybdenum nonadeca­sulfide, Cs₂Mo₁₅S₁₉, consists of a mixture of Mo₆S₈S₆ and Mo₉S₁₁S₆ cluster units in a 1:1 ratio. Both units are interconnected via inter‐unit Mo—S bonds. The Cs⁺ cations occupy large voids between the different cluster units. The Cs and two inner S atoms lie on sites with 3 symmetry (Wyckoff site 12c) and the Mo and S atoms of the median plane of the Mo₉S₁₁S₆ cluster unit on sites with 2 symmetry (Wyckoff site 18e).     

Rubidium dimolybdate,Rb2Mo2O7, and caesium dimolybdate,Cs2Mo2O7

The crystal structures of dirubidium hepta­oxodimolybdate, Rb₂Mo₂O₇, and dicaesium hepta­oxodimolybdate, Cs₂Mo₂O₇, in the space groups Ama2 and P2₁/c, respectively, have been determined for the first time by single‐crystal X‐ray diffraction. The structures represent two novel structure types of monovalent ion dimolybdates, A₂Mo₂O₇ (A = alkaline elements, NH₄, Ag or Tl). In the structure of Rb₂Mo₂O₇, Mo atoms are on a twofold axis, on a mirror plane and in a general position. One of the Rb atoms lies on a twofold axis, while three others are on mirror planes. Two O atoms attached to the Mo atom on a mirror plane are located on the same plane. Rubidium dimolybdate contains a new kind of infinite Mo–O chain formed from linked MoO₄ tetra­hedra and MoO₆ octa­hedra alternating along the a axis, with two terminal MoO₄ tetra­hedra sharing corners with each octa­hedron. The chains stack in the [001] direction to form channels of an approximately square section filled by ten‐coordinate Rb ions. Seven‐ and eight‐coordinate Rb atoms are located between chains connected by a c translation. In the structure of Cs₂Mo₂O₇, all atoms are in general positions. The MoO₆ octa­hedra share opposite corners to form separate infinite chains running along the c axis and strengthened by bridging MoO₄ tetra­hedra. The same Mo–O polyhedral chain occurs in the structure of Na₂Mo₂O₇. Eight‐ to eleven‐coordinate Cs atoms fill the space between the chains. The atomic arrangement of caesium dimolybdate has an ortho­rhom­bic pseudosymmetry that suggests a possible phase transition P2₁/c→Pbca at elevated temperatures.     

Synthese und Struktur von Mo2NCl7

Synthesis and Structure of Mo₂NCl₇ The reaction of VN with MoCl₅ at 175 °C in a sealed glass ampoule yields the molybdenum(V) nitride chloride Mo₂NCl₇ in form of air sensitive black crystals with the triclinic space group P1¯ and a = 905.7(8); b = 975.4((6); c = 1283.4(8) pm, α = 103.13(4)°; β = 109.83(5)° und γ = 98.58(5)°. The crystal structure is built up from dinuclear units [Mo₂N₂Cl₇]^3— and [Mo₂Cl₇]³⁺, which are connected by asymmetric nitrido bridges to form endless chains. Within both dinuclear units the Mo atoms are bridged by three Cl atoms resulting in a Mo‐Mo distance of 349.2(3) pm in the unit [Mo₂N₂Cl₇]^3—. In case of [Mo₂Cl₇]³⁺, however, a shorter Mo‐Mo distance of 289.4(3) pm is observed, which can be interpreted by a single bond. Correspondingly a reduced magnetic moment of 0.95 B.M. per Mo atom is observed.     

Synthesis and structure of an open-type trinuclear molybdenum cluster compound[Mo_3(μ_3-S)(μ-S)_2-(μ-OAc)(S_2CNC_4H_8)_3(O)_2]·0.5CH_2Cl_2·2H_2O

The title compound was prepared by the reaction of Mo_3S_4(dtp)_4(H_2O)[ctp=S_2P(OEt)_2]with NaOAc·3H_2O and C_4H_8NCS_2NH_4.Crystallographic data:[Mo_3(μ_3-S)(μ-S)_2(μ-OAc)-(S_2CNC_4H_8)_3(O)_2]·0.5CH_2CI_2·2H_2O,Mr=980.18,triclinic,space group P,α=12.360(3),b=16.653(6),c=9.206(2)A,α=101.97(2),β=108.32(2),γ=86.14(3)°.V=1759.6(9)A~3,Z=2,Dc=1.85 g/cm~3,F(000)=962,μ(Mo K_α)=16.53 cm~(-1).Final R=0.044 for 4301 reflections with I≥3σ(I).This compoundmay be regarded as a mixed-valent trinuclear molybdenum cluster{Mo_2(V)Mo(Ⅳ)(μ_3-S)(μ-S)_2-(μ-OAc)(S_2CNC_4H_8)_3(O)_2}.The Mo-Mo distances are 2.783(1),2.833(1)and 3.374(2)A in the Mo_3non-equilateral triangle and there exist only two Mo-Mo bonds.The cluster was obtained by oxi-dation and ligand substitution of{Mo_3(μ_3-S)(μ-S)_3[μ-S_2P(OEt_2)][S_2P(OEt)_2]_3(H_2O)}.     

La5Mo6O21: a novel ternary reduced molybdenum oxide containing {MoIV}3 clusters and isolated MoV centres

The crystal structure of La₅Mo₆O₂₁ (penta­lanthanum hexa­molybdenum henicosa­oxide) is made up of Mo₃O₁₃ units containing triangular {Mo^IV}₃ clusters, three distorted Mo^VO₆ octa­hedral units and six inter­stitial La^III atoms. The Mo₃O₁₃ unit consists of three edge‐sharing Mo^IVO₆ units involving Mo—Mo bonding. The three Mo^VO₆ octa­hedra share their corners or edges with each other and with the Mo₃O₁₃ units.     

The crystal structure of (NH4)2[Mo2(S2)6].8/3H2

The black crystal of (NH₄)[Mo₂(S₂)₆]* 8/3 H₂O belongs to the orthorhombic system, space group D³₂-P22₁2₁, with a = 12.064(6), b = 12.534(4), c = 19.558(9)Å, V =2957(3)ų, Z = 4 and D_c = 2.23g.cm^?3. The intensity data were collected on a Syntex R3 four-circle diffractometer. The structure was solved by Patterson method and direct method, the light atoms (except H atoms) were obtained from ΔF syntheses. The structure was refined by least-squares with anisotropic thermal parameters. The values of R and R_w were 0.092 and 0.072 respectively. The crystal structure contains discrete dimeric cluster [Mo₂(S₂)₆]^2? ions, NH₄⁺ cations and H₂O molecules. There are two crystallographically independent [Mo₂S₂)₆]^2? ions in the crystal, one locates on general position [Figure 1(a)], the other locates on two-fold axis [Figure 1(b)]. It contains one and a half [Mo₂S₂)₆]^2? ions in an asymmetric unit. In [Mo₂S₂)₆]^2? each Mo is coordinated side on by four S₂^2? groups in a distorted dodecahedral arrangement, two of which are bridging and the other two are terminal. The Mo? S bond length is 2.441 Å (mean), and S? S is 2.049 Å (mean). The Mo? Mo distance is 2.784 Å (mean), which is to be regarded as a single bond length. The formal oxidation state of Mo is five, it is probably a mixed valence Mo^IV? Mo^VI, and so shows a remarkable deep colour.     

Thiochloroanionen von Molybdän(IV). Die Kristallstruktur von (NEt4)3[Mo3(μ3-S)(μ-S2)3Cl6]Cl · CH2Cl2 Kristallstruktur,EPR-Spektrum und magnetische Eigenschaften von (NEt4)2[Mo2(μ-S2)(μ-Cl)2Cl6]

Thiochloro Anions of Molybdenum (IV). Crystal Structure of (NEt₄)₃[Mo₃(μ₃-S)(μ-S₂)₃Cl₆]Cl μ CH₂Cl₂. Crystal Structure, Magnetic Properties, and EPR-Spectrum of (NEt₄)₂ [Mo₂(μ-S₂)(μ-Cl)₂Cl₆] From molybdenum pentachloride and tetraethylammonium hydrogensulfide in CH₂Cl₂ an insoluble product of composition (NEt₄)₂[Mo₂S₃Cl₉] was obtained along with a brown solution, from which (NEt₄)₂[Mo₂(S₂)Cl₈] was crystallized. The insoluble product and NEt₄Cl react in CH₂Cl₂ to yield, among others, (NEt₄)₃[Mo₃(S)(S₂)₃Cl₆]Cl · CH₂Cl₂. The latter crystallizes in the orthorhombic space group Pnma, a = 2495.8, b = 1501.2, c = 1295.6 pm, Z = 4. According to the crystal structure determination (3070 observed reflexions, R = 0.049) the [Mo₃(S)(S₂)₃Cl₆]^2? ion consists of an Mo₃ triangle with Mo? Mo bonds, each side of the triangle is bridged by disulfido groups and one sulfur atom is capped over the Mo₃ triangle; the single chloride ion is looseley associated to three S atoms. (NEt₄)₂[Mo₂(S₂)Cl₈] also crystallizes in the space group Pnma, a = 1425.6, b = 1129.9, c = 2004.7 pm, Z = 4; structure determination with 1703 observed reflexions, R = 0.061. In the [Mo₂(S₂)Cl₈]^2? ion the Mo atoms are bridged via one disulfido group and two chlorine atoms. There is a Mo? Mo bond, but according to the magnetic properties and the EPR spectrum each Mo atom still possesses one unpaired electron.     

The molybdenum-molybdenum triple bond—XVII. Syntheses,spectroscopic and structural characterizations of Mo4F4(O—t-Bu)8 and Mo2F2(O—t-Bu)4(PMe3)2 (MoMo)

Hydrocarbon solutions of Mo₂(O—t-Bu)₆ and PF₃ (2 equiv) yield Mo₄F₄(O—t-Bu)₈, I, and PF₂(O—t-Bu). Compound I contains a bisphenoid of molybdenum atoms with two short MoMo distances, 2.26 Å, and four long MoMo distances, 3.75 Å, corresponding to localized MoMo triple bonding and non-bonding distances, respectively. The tetranuclear compound may be viewed as a dimer, [Mo₂(μ₂-F)₂(O-t-Bu)₄]₂, and addition of PMe₃ to hydrocarbon solutions of I yields Mo₂F₂(O—t-Bu)₄(PMe₃)₂, II, which contains an unbridged MoMo triple bond of distance 2.27 Å. Each molybdenum atom is coordinated to two oxygen atoms, one fluorine atom and the phosphorus atom of the PMe₃ ligand in a roughly square planar manner. The overall central Mo₂O₄F₂P₂ skeleton has C₂ symmetry and NMR studies (¹H, ¹⁹F and ³¹P) are consistent with the maintenance of this type of structure in solution. Infrared and electronic absorption spectral data are reported. These are the first compounds containing fluorine ligands attached to the (MoMo)⁶⁺ unit.     

Bis­(tetra­methyl­ammonium) nona­decaoxohexamolybdenum(VI) mono­hydrate

The six Mo atoms in the title compound, (C₄H₁₂N)₂[Mo₆O₁₉].H₂O, form a standard octahedral cage through bridging O atoms. The [Mo₆O₁₉]^2? anion as a whole has O_h symmetry with three crystallographic fourfold axes aligned along Mo—O—Mo. There exist weak O?O hydrogen bonds (O100?O3 2.951 Å) between the terminal O3 atoms of the anions and O100 atoms of the solvate hydrates in the unit cell.     

Bis(μ‐hexa­methyl­enetetr­amine)­bis(aqua­di­bromo­cadmium)­di­aqua­di­bromo­cadmium dihydrate

The title compound, poly­[[di­aqua­di­bromo­cadmium‐μ‐(1,3,5,7‐tetra­aza­tri­cyclo[3.3.1.1^3,7]decane‐N¹:N⁵)‐aqua­cad­mium‐di‐μ‐bromo‐aqua­cadmium‐μ‐(1,3,5,7‐tetra­aza­tri­cyclo[3.3.1.1^3,7]decane‐N¹:N⁵)‐di‐μ‐bromo] dihydrate], [Cd₃­Br₆­(C₆­H₁₂­N₄)₂­(H₂O)₄]·­2H₂O, is made up of two‐dimensional neutral rectangular coordination layers. Each rectangular subunit is enclosed by a pair of Cd₃(μ₂‐Br)₆(H₂O)₃ fragments and a pair of (μ₂‐hmt)Cd(H₂O)₂Br₂(μ₂‐hmt) fragments as sides (hmt is hexa­methyl­enetetr­amine). The unique Cd^II atom in the Cd₂Br₂ ring in the Cd₃(μ₂‐Br)₆(H₂O)₃ fragment is in a slightly distorted octahedral CdNOBr₄ geometry, surrounded by one hmt ligand [2.433 (5) Å], one aqua ligand [2.273 (4) Å] and four Br atoms [2.6409 (11)–3.0270 (14) Å]. The Cd^II atom in the (μ₂‐hmt)Cd(H₂O)₂Br₂(μ₂‐hmt) fragment lies on an inversion center and is in a highly distorted octahedral CdN₂O₂Br₂ geometry, surrounded by two trans‐related N atoms of two hmt ligands [2.479 (5) Å], two trans‐related aqua ligands [2.294 (4) Å] and two trans‐related Br atoms [2.6755 (12) Å]. Adjacent two‐dimensional coordination sheets are connected into a three‐dimensional network by hydrogen bonds involving lattice water mol­ecules, and the aqua, bromo and hmt ligands belonging to different layers.     

A binuclear rhodium(I) complex with two tetraphosphine ligands at 100 K

Bis(μ‐3,11‐diethyl‐6,8‐di­phenyl‐3,6,8,11‐tetraphosphatri­dec­ane‐κ⁴P³,P⁶:P⁸,P¹¹)­dirhodium(I) bis­(tetra­fluoro­borate), [Rh₂(C₂₅H₄₀P₄)₂](BF₄)₂, is a bimetallic complex containing two binucleating tetra‐tertiary phosphine ligands. The distance between the metal centers is 5.4555 (11) Å, with no metal–metal bond. The Rh—P bond distances range from 2.2483 (14) to 2.3295 (14) Å. The geometry about the Rh^I atoms is tetrahedrally distorted square planar and the dihedral angle between the two coordination planes is 66.28 (5)°.     

Experimental and Computational Studies on Quadruply Bonded Dimolybdenum Complexes with Terminal and Bridging Hydride Ligands

This contribution focuses on complex [Mo₂(H)₂(μ-Ad^Dipp2)₂] ( 1 ) and tetrahydrofuran and pyridine adducts [Mo₂(H)₂(μ-Ad^Dipp2)₂(L)₂] ( 1⋅thf and 1⋅py ), which contain a trans-(H)Mo≣Mo(H) core (Ad^Dipp2=HC(NDipp₂)₂; Dipp=2,6-iPr₂C₆H₃). Computational studies provide insights into the coordination and electronic characteristics of the central trans-Mo₂H₂ unit of 1 , with four-coordinate, fourteen-electron Mo atoms and ϵ-agostic interactions with Dipp methyl groups. Small size C- and N-donors give rise to related complexes 1⋅L but only one molecule of P-donors, for example, PMe₃, can bind to 1 , causing one of the hydrides to form a three-centered, two-electron (3c-2e) Mo-H→Mo bond ( 2⋅PMe₃ ). A DFT analysis of the terminal and bridging hydride coordination to the Mo≣Mo bond is also reported, along with reactivity studies of the Mo−H bonds of these complexes. Reactions investigated include oxidation of 1⋅thf by silver triflimidate, AgNTf₂, to afford a monohydride [Mo₂(μ-H)(μ-NTf₂)(μ-Ad^Dipp2)₂] ( 4 ), with an O,O’-bridging triflimidate ligand.     

Pentafluorobenzoato‐dimolybdenum(II) Solvate and Co‐crystal Complexes with Benzene and Naphthalin

The quadruply bonded Mo₂⁴⁺ complex Mo₂(DAniF)₃(OOCC₆F₅) ( 1 ) [DAniF = N,N′‐bis(4‐methoxyphenyl)formamidinate] was synthesized. The solvate Mo₂(DAniF)₃(OOCC₆F₅) · (C₆H₆) ( 2 ) and co‐crystal Mo₂(DAniF)₃(OOCC₆F₅) · (C₁₀H₈) ( 3 ) complexes were obtained by self‐assembly of crystals of 1 with benzene and naphthalin, respectively. Compounds 1 , 2 , and 3 were structurally characterized by single‐crystal X‐ray diffraction. In monomer 1 , the Mo–Mo bond length of 2.0874(6) Å is typical for dimolybdenum quadruple bonds. The solvate complex 2 was stabilized by weak π–π stacking interactions between the benzene molecule and the pentafluorophenyl ring (as indicated by a center‐to‐center distance of 3.838(10) Å and a center‐to‐plane distance of 3.712(4) Å between phenyl and pentafluorophenyl ring) and intermolecular C–H ··· F–C interactions (the shortest F ··· H distance is 2.560(2) Å). In complex 3 , a one‐dimensional chain was formed by C–H ··· F–C interactions between the hydrogen atoms in naphthalin and the fluorine atoms in the monomer (H ··· F distances of 2.582(2) Å). Information on the structures in solution of the three crystals was obtained by ¹H NMR spectroscopy.     

Compounds with Cluster Cations together with Cluster Anions [(M6X12)(EtOH)6]2+ besides [(Mo6Cl8)Cl4X2]2– (M = Nb,Ta; X = Cl,Br) – Synthesis and Crystal Structures

Compounds consisting of both cluster cations and cluster anions of the composition [(M₆X₁₂)(EtOH)₆][(Mo₆Cl₈)Cl₄X₂] · n EtOH · m Et₂O (M = Nb, Ta; X = Cl, Br) have been prepared by the reaction of (M₆X₁₂)X₂ · 6 EtOH with (Mo₆Cl₈)Cl₄. IR data are given for three compounds. The structures of [(Nb₆Cl₁₂)(EtOH)₆][(Mo₆Cl₈)Cl₆] · 3 EtOH · 3 Et₂O 1 and [(Ta₆Cl₁₂)(EtOH)₆][(Mo₆Cl₈)Cl₆] · 6 EtOH 2 have been solved in the triclinic space group P1 (No. 2). Crystal data: 1 , a = 10.641(2) Å, b = 13.947(2) Å, c = 15.460(3) Å, α = 65.71(2)°, β = 73.61(2)°, γ = 85.11(2)°, V = 2005.1(8) ų and Z = 1; 2 , a = 11.218(2) Å, b = 12.723(3) Å, c = 14.134(3) Å, α = 108.06(2)°, β = 101.13(2)°, γ = 91.18(2)°, V = 1874.8(7) ų and Z = 1. Both structures are built of octahedral [(M₆Cl₁₂)(EtOH)₆]²⁺ cluster cations and [(Mo₆Cl₈)Cl₆]^2– cluster anions, forming distorted CsCl structure types. The Nb–Nb and Ta–Ta bond lengths of 2.904 Å and 2.872 Å (mean values), respectively, are rather short, indicating weak M–O bonds. All O atoms of coordinated EtOH molecules are involved in H bridges. The Mo–Mo distances of 2.603 Å and 2.609 Å (on average) are characteristic for the [(Mo₆Cl₈)Cl₆]^2– anion, but there is a clear correlation between the number of hydrogen bridges to the terminal Cl and the corresponding Mo–Cl distances.     

X-ray absorption spectroscopy study of the electronic structure and local coordination of 1st row transition metal-promoted Chevrel-phase sulfides

Abstract

The electronic structures of S and Mo as well as the local coordination of Mo are investigated as a function of metal promotion Chevrel-phase (CP) sulfides. We observe the effect of metal promoter-induced electron donation into the stoichiometric range M_xMo₆S₈ (M?=?Fe, Ni, Cu; x?=?0–2) through analysis of X-ray absorption near-edge structure regions. We further observe the effect of this promotion on the bonding environment of Mo₆ metal centers through extended X-ray absorption fine structure analysis. We monitor expansion and contraction of Mo₆ octahedra with and without metal promotion, as has been predicted by Hückel molecular orbital theory. We further observe a marked tunability in the electronic structure of sulfur upon charge transfer between promoting species and Mo₆S₈ units. Average Mo₆ octahedron Mo–Mo bond contraction from 2.76 Å to as short as 2.69 Å was observed upon incorporation of metal promoters, while intercluster separation displays a pronounced increase for promoter-host lattices compared to un-promoted Mo₆S₈. To corroborate spectroscopically observed phenomena, we performed computational analyses of spin-polarized densities of state for the CP materials investigated herein, where a detectable increase in sulfur-based frontier orbital population is observed in accordance with experimentally validated orbital filling.     

Synthesis and crystal structure of a cubanelike tetranuclear molybdenum cluster compound {Mo4)(μ3-S)3)(μ3-O)[S2P(OEt)2]6} · 3CH3CN

A tetranuclear molybdenum cluster compound {Mo₄(μ₃-S)₃(μ₃-O)[S₂P(OEt)₂]₅} · 3CH₃CN was obtained by the reaction of MoCl₃ · 3H₂O with P₂S₅ in ethanol and then recrystallization from acetonitrile. The compound crystallizes in the trigonal system belonging to the space group R3 with the following cell dimensions: a = b = c = 12.852 (3) Å, α = β = γ = 108.37 (2)°, V =1697.3ų Z = 1, D_c. = 1.693g.cm^?3. The structure was solved by heavy atom method and refined by full-matrix least-squares to R = 0.072 for 1781 reflections with I≥3σ(I). The results of the structure determination indicate that the cluster skeleton possesses a cubanelike cluster core formed by four Mo atoms located in a distored tetrahedron with three S atoms and one O atom as its triple bridging atoms. There are two sets of bond distances, i.e. 2.700 (1) and 2.831(1) Å in the six Mo—Mo bonds. Taking the Mo cluster core as a whole, it has a formal oxidation state of +14, leaving ten electrons to form the metal-metal bonds. Thus each Mo—Mo bond has an average bond order of 5/6.