Modeling the Formation of Molybdenum Oxides from Alkoxides: Crystal Structures of [Mo(4)O(4)Cl(4)(&mgr;(2)-OEt)(4)(HOEt)(2)(&mgr;(3)-O)(2)] and [PPN](+)[Et(3)NH](+)[Cl(2)(O)Mo(&mgr;(2)-O)(2)Mo(O)Cl(2)](2)(-)

The reactions of the binuclear oxomolybdenum(V) complex [Cl(2)(O)Mo(&mgr;-OEt)(2)(&mgr;-HOEt)Mo(O)Cl(2)] (1) with Me(3)Si(allyl) and SbF(3) produce the compounds [Mo(6)O(6)Cl(6)(&mgr;(3)-O)(2)(&mgr;(2)-OEt)(6)(&mgr;(2)-Cl)(2)] (2) and [Mo(8)O(8)Cl(6)(&mgr;(3)-O)(4)(OH)(2)(&mgr;(2)-OH)(4)(&mgr;(2)-OEt)(4)(HOEt)(4)] (3), respectively. Treatment of 1 with the Lewis base PMe(3) affords the tetrameric complex [Mo(4)O(4)Cl(4)(&mgr;(2)-OEt)(4)(HOEt)(2)(&mgr;(3)-O)(2)] (4), which represents another link in the chain of clusters produced by the reactions of 1 and simulating the build-up of polymeric molybdenum oxides by sol-gel methods. The crystal structure of 4 has been determined [C(12)H(32)Cl(4)Mo(4)O(12), triclinic, P&onemacr;, a = 7.376(2) ?, b = 8.807(3) ?, c = 11.467(4) ?, alpha = 109.61(1) degrees, beta = 92.12(3) degrees, gamma = 103.75(2) degrees, Z = 1]. By contrast, reaction of 1 with the nitrogen base NEt(3), followed by treatment with [PPN]Cl.2H(2)O ([PPN](+) = [Ph(3)P=N=PPh(3)](+)), gives the complex [PPN](+)[Et(3)NH](+)[Cl(2)(O)Mo(&mgr;(2)-O)(2)Mo(O)Cl(2)](2)(-) (6) in 90% yield. Its crystal structure [C(36)H(30)Cl(4)MoNOP(2), triclinic, Pna2(1), a = 21.470(6) ?, b = 16.765(2) ?, c = 9.6155(14) ?, alpha = 90 degrees, beta = 90 degrees, gamma = 90 degrees, Z = 16] includes the anion [Cl(2)(O)Mo(&mgr;(2)-O)(2)Mo(O)Cl(2)](2)(-), which is a charged derivative of the species forming the gels in sol-gel processes starting from chloromolybdenum ethoxides. Furthermore, compound 1 is found to be catalytically active in esterification and dehydration reactions of alcohols.     

Isolation of a Bismuth Chloride-Iron Carbonyl Adduct: Synthesis and Structural Characterization of [PhCH(2)NMe(3)](2)[Bi(2)Cl(4)(&mgr;-Cl)(2){&mgr;-Fe(CO)(4)}

The reaction of bismuth(III) chloride with [PhCH(2)NMe(3)](2)[Fe(CO)(4)] at a ratio of 2:1 in acetonitrile yields the iron carbonyl-bismuth chloride adduct [PhCH(2)NMe(3)](2)[Bi(2)Cl(4)(&mgr;-Cl)(2){&mgr;-Fe(CO)(4)}] cleanly in high yield. The complex consists of two BiCl(3) groups bridged by an [Fe(CO)(4)](2)(-) unit. Two chloride ligands are shared between the Bi atoms, producing square-pyramidal coordination at bismuth and octahedral coordination at the iron center. The production of this complex represents the synthesis of a stable adduct of a highly nucleophilic metal carbonyl anion with a strongly Lewis acidic main group halide. The compound C(24)H(32)N(2)O(4)Bi(2)Cl(6)Fe crystallizes in the orthorhombic space group Pba2 (No. 32) with cell parameters a = 14.624(3) ?, b = 17.010(3) ?, c = 7.1990(10) ?, V = 1790.8(5) ?(3), and Z = 2.     

An Approach to Heterometallic Complexes with Selenolate and Tellurolate Ligands: Crystal Structures of cis-[Mn(CO)(4)(SePh)(2)](-), [(CO)(3)Mn(&mgr;-SeMe)(3)Mn(CO)(3)](-), (CO)(4)Mn(&mgr;-TePh)(2)Co(CO)(&mgr;-SePh)(3)Mn(CO)(3), and (CO)(3)Mn(&mgr;-SePh)(3)Fe(CO)(3)

Oxidative addition of diorganyl diselenides to the coordinatively unsaturated, low-valent transition-metal-carbonyl fragment [Mn(CO)(5)](-) produced cis-[Mn(CO)(4)(SeR)(2)](-). The complex cis-[PPN][Mn(CO)(4)(SePh)(2)] crystallized in triclinic space group P&onemacr; with a = 10.892(8) ?, b = 10.992(7) ?, c = 27.021(4) ?, alpha = 101.93(4) degrees, beta = 89.79(5) degrees, gamma = 116.94(5) degrees, V = 2807(3) ?(3), and Z = 2; final R = 0.085 and R(w) = 0.094. Thermolytic transformation of cis-[Mn(CO)(4)(SeMe)(2)](-) to [(CO)(3)Mn(&mgr;-SeMe)(3)Mn(CO)(3)](-) was accomplished in high yield in THF at room temperature. Crystal data for [Na-18-crown-6-ether][(CO)(3)Mn(&mgr;-SeMe)(3)Mn(CO)(3)]: trigonal space group R&thremacr;, a = 13.533(3) ?, c = 32.292(8) ?, V = 5122(2) ?(3), Z = 6, R = 0.042, R(w) = 0.041. Oxidation of Co(2+) to Co(3+) by diphenyl diselenide in the presence of chelating metallo ligands cis-[Mn(CO)(4)(SePh)(2)](-) and cis-[Mn(CO)(4)(TePh)(2)](-), followed by a bezenselenolate ligand rearranging to bridge two metals and a labile carbonyl shift from Mn to Co, led directly to [(CO)(4)Mn(&mgr;-TePh)(2)Co(CO)(&mgr;-SePh)(3)Mn(CO)(3)]. Crystal data: triclinic space group P&onemacr;, a = 11.712(3) ?, b = 12.197(3) ?, c = 15.754(3) ?, alpha = 83.56(2) degrees, beta = 76.13(2) degrees, gamma = 72.69(2) degrees, V = 2083.8(7) ?(3), Z = 2, R = 0.040, R(w) = 0.040. Addition of fac-[Fe(CO)(3)(SePh)(3)](-) to fac-[Mn(CO)(3)(CH(3)CN)(3)](+) resulted in formation of (CO)(3)Mn(&mgr;-SePh)(3)Fe(CO)(3). This neutral heterometallic complex crystallized in monoclinic space group P2(1)/n with a = 8.707(2) ?, b = 17.413(4) ?, c = 17.541(4) ?, beta = 99.72(2) degrees, V = 2621(1) ?(3), and Z = 4; final R = 0.033 and R(w) = 0.030.     

Electronic Structure of [Pt(2)(&mgr;-O(2)CCH(3))(4)(H(2)O)(2)](2+) Using the Quasi-Relativistic Xalpha-SW Method: Analysis of Metal-Metal Bonding, Assignment of Electronic Spectra, and Comparison with Rh(2)(&mgr;-O(2)CCH(3))(4)(H(2)O)(2)

The electronic structure and metal-metal bonding in the classic d(7)d(7) tetra-bridged lantern dimer [Pt(2)(O(2)CCH(3))(4)(H(2)O)(2)](2+) has been investigated by performing quasi-relativistic Xalpha-SW molecular orbital calculations on the analogous formate-bridged complex. From the calculations, the highest occupied and lowest unoccupied metal-based levels are delta(Pt(2)) and sigma(Pt(2)), respectively, indicating a metal-metal single bond analogous to the isoelectronic Rh(II) complex. The energetic ordering of the main metal-metal bonding levels is, however, quite different from that found for the Rh(II) complex, and the upper metal-metal bonding and antibonding levels have significantly more ligand character. As found for the related complex [W(2)(O(2)CH)(4)], the inclusion of relativistic effects leads to a further strengthening of the metal-metal sigma bond as a result of the increased involvement of the higher-lying platinum 6s orbital. The low-temperature absorption spectrum of [Pt(2)(O(2)CCH(3))(4)(H(2)O)(2)](2+) is assigned on the basis of Xalpha-SW calculated transition energies and oscillator strengths. Unlike the analogous Rh(II) spectrum, the visible and near-UV absorption spectrum is dominated by charge transfer (CT) transitions. The weak, visible bands at 27 500 and 31 500 cm(-)(1) are assigned to Ow --> sigma(Pt(2)) and OAc --> sigma(Pt(2)) CT transitions, respectively, although the donor orbital in the latter transition has around 25% pi(Pt(2)) character. The intense near-UV band around 37 500 cm(-)(1) displays the typical lower energy shift as the axial substituents are changed from H(2)O to Cl and Br, indicative of significant charge transfer character. From the calculated oscillator strengths, a number of transitions, mostly OAc --> sigma(Pt-O) CT in nature, are predicted to contribute to this band, including the metal-based sigma(Pt(2)) --> sigma(Pt(2)) transition. The close similarity in the absorption spectra of the CH(3)COO(-), SO(4)(2)(-), and HPO(4)(2)(-) bridged Pt(III) complexes suggests that analogous spectral assignments should apply to [Pt(2)(SO(4))(4)(H(2)O)(2)](2)(-) and [Pt(2)(HPO(4))(4)(H(2)O)(2)](2)(-). Consequently, the anomalous MCD spectra reported recently for the intense near-UV band in the SO(4)(2)(-) and HPO(4)(2)(-) bridged Pt(III) complexes can be rationalized on the basis of contributions from either SO(4) --> sigma(Pt-O) or HPO(4) --> sigma(Pt-O) CT transitions. The electronic absorption spectrum of [Rh(2)(O(2)CCH(3))(4)(H(2)O)(2)] has been re-examined on the basis of Xalpha-SW calculated transition energies and oscillator strengths. The intense UV band at approximately 45 000 cm(-)(1) is predicted to arise from several excitations, both metal-centered and CT in origin. The lower energy shoulder at approximately 40 000 cm(-)(1) is largely attributed to the metal-based sigma(Rh(2)) --> sigma(Rh(2)) transition.     

Magnetic Susceptibility Trends in Oxo-Bridged, Dinuclear Chromium(III) Complexes. Crystal Structure of [(tmpa)Cr(&mgr;-O)(&mgr;-CO(3))Cr(tmpa)](ClO(4))(2).2H(2)O

The synthesis and physical characterization of oxo-bridged [Cr(2)(tmpa)(2)(&mgr;-O)(X)](n)()(+) complexes (tmpa = tris(2-pyridylmethyl)amine) containing a variety of complementary ligands (X = CO(3)(2)(-), PhPO(4)(2)(-), HS(-)) are described, with the objective of understanding factors underlying variations in the antiferromagnetic coupling constant J. We also present the crystal structure of [(tmpa)Cr(&mgr;-O)(&mgr;-CO(3))Cr(tmpa)](ClO(4))(2).2H(2)O, for comparison with previous findings on [(tmpa)Cr(&mgr;-O)(&mgr;-CH(3)CO(2))Cr(tmpa)](ClO(4))(3). The carbonate-bridged complex crystallizes in the monoclinic space group P2(1)/c with a = 11.286(10) ?, b = 18.12(2) ?, c = 20.592(12) ?, beta = 95.99(5) degrees, and V = 4190 ?(3) and Z = 4. Asymmetric tmpa ligation pertains, with apical N atoms situated trans to bridging oxo and acido O atoms. Key structural parameters include Cr-O(b) bond lengths of 1.818(6) and 1.838(6) ?, Cr-OCO(2) distances of 1.924(7) and 1.934(7) ?, and a bridging bond angle of 128.3(3) degrees. Several attempts to prepare oxo, amido-bridged dimers were unsuccessful, but the nearlinear [Cr(tmpa)(N(CN)(2))](2)O(ClO(4))(2).3H(2)O complex was isolated from the reaction of dicyanamide ion with [Cr(tmpa)(OH)](2)(4+). In contrast to the behavior of analogous diiron(III) complexes, antiferromagnetic coupling constants of [Cr(2)(tmpa)(2)(&mgr;-O)(X)](n)()(+) dinuclear species are highly responsive to the X group. Considering the complexes with X = CO(3)(2)(-), PhPO(4)(2)(-), HS(-), SO(4)(2)(-), and RCO(2)(-) (10 R substituents), we find a reasonably linear, empirical relationship between J and oxo bridge basicity, as measured by pK(a) (Cr(OH)Cr) values in aqueous solution. While there is no theoretical basis for such a correlation between solid-state and solution-phase properties, this relationship demonstrates that CrOCr pi-bonding contributes significantly to antiferromagnetic exchange. Thus, J tends to become less negative with increasing &mgr;-O(2)(-) basicity, showing that greater availability of a bridging oxo group lone pair toward the proton, with decreasing CrOCr pi-interaction, reduces the singlet-triplet gap.     

Synthesis and electrochemistry of new Rh-centered and conjuncto rhodium carbonyl clusters. X-ray structure of [NEt(4)](3)[Rh(15)(CO)(27)], [NEt(4)](3)[Rh(15)(CO)(25)(MeCN)(2)] x 2MeCN, and [NEt(4)](3)[Rh(17)(CO)(37)

A reinvestigation of the redox chemistry of [Rh7(CO)16]3- resulted in the finding of new alternative syntheses for a series of previously reported Rh-centered carbonyl clusters, i.e., [H4-nRh14(CO)25]n- (n = 3 and 4) and [Rh17(CO)30]3-, as well as new species such as a different isomer of [Rh15(CO)27]3-, the carbonyl-substituted [Rh15(CO)25(MeCN)2]3-, and the conjuncto [Rh17(CO)37]3- clusters. All of the above clusters are suggested to derive from oxidation of [Rh7(CO)16]3- with H+, arising from dissociation either of [M(H2O)n]2+ aquo complexes or nonoxidizing acids. The nature of the previously reported species has been confirmed by IR, electrospray ionization mass spectrometry, and complete X-ray diffraction studies. Only the molecular structures of the new clusters are reported in some details. The ready conversion of [Rh7(CO)16]3- in [HRh14(CO)25]3- upon oxidation has been confirmed by electrochemical techniques. In addition, electrochemical studies point out that the close-packed [H3Rh13(CO)24]2- dianion undergoes a reversible monoelectronic reduction followed by an irreversible reduction. The irreversibility of the second reduction is probably a consequence of H2 elimination from a purported [H3Rh13(CO)24]4- species. Conversely, the body-centered-cubic [HRh14(CO)25]3- and [Rh15(CO)27]3- trianions display several well-defined redox changes with features of electrochemical reversibility, even at low scan rate. The major conclusion of this work is that mild experimental conditions and a tailored oxidizing reagent may enable more selective conversion of [Rh7(CO)16]3- into a higher-nuclearity rhodium carbonyl cluster. It is also shown that isonuclear Rh clusters may display isomeric metal frameworks [i.e., [Rh15(CO)27]3-], as well as almost identical metal frames stabilized by a different number of carbonyl groups [i.e., [Rh15(CO)27]3- and [Rh15(CO)30]3-]. Other isonuclear Rh clusters stabilized by a different number of CO ligands more expectedly exhibit completely different metal geometries [i.e., [Rh17(CO)30]3- and [Rh17(CO)37]3-]. The first pair of isonuclear and isoskeletal clusters is particularly astonishing in that [Rh15(CO)30]3- features six valence electrons more than [Rh15(CO)27]3-. Finally, the electrochemical studies seem to suggest that interstitial Rh atoms are less effective than Ni and Pt interstitial atoms in promoting redox properties and inducing molecular capacitor behavior in carbonyl clusters.     

Mechanism of (&mgr;-H)(&mgr;-alkenyl)Re(2)(CO)(8) Formation in 350 nm Flash Irradiations of Re(2)(CO)(10)

The mechanism of (&mgr;-H)(&mgr;-alkenyl)Re(2)(CO)(8) formation upon UV irradiations of Re(2)(CO)(10) in presence of olefin (styrene, trans-stilbene, 4-methyl-1-cyclohexane, and ethylene) was investigated by laser flash photolyses. Such photoproducts result from reactions of the olefin with eq-Re(2)(CO)(9). No reactions of Re(CO)(5) leading to hydride alkenyl products were observed. Dependences of the reaction rate on olefin concentration and solvent revealed an additional intermediate formed after the addition of the olefin to eq-Re(2)(CO)(9) and before the appearance of the &mgr;-hydrido-&mgr;-alkenyl products.     

New tetrathiapentalene-derived charge transfer salts with paramagnetic transition metal complex anion: kappa-(EDDH-TTP)(3)[Cr(phen)(NCS)(4)] x 2CH(2)Cl(2) and kappa(21)-(BDH-TTP)(5)[Cr(phen)(NCS)(4)](2) x 2CH(2)Cl(2)

The preparation, crystal structures, and optical and magnetic properties of two new charge-transfer salts kappa-(EDDH-TTP)(3)[Cr(phen)(NCS)(4)] x 2CH(2)Cl(2) (1) and kappa(21)-(BDH-TTP)(5)[Cr(phen)(NCS)(4)](2) x 2CH(2)Cl(2) (2), where phen = 1,10- phenanthroline, EDDH-TTP = 2-(4,5-ethylenedithio-1,3-dithiol-2-ylidene)-5-(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene, and BDH-TTP = 2,5-bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene, are reported. Crystal data: (1) monoclinic P2(1)/a, a = 25.0752(5) A, b = 10.6732(3) A, c = 28.1601(6) A, beta = 95.195(2) degrees, Z = 4, R = 0.0585 for 6741 independent reflections with I > 3 sigma(I); (2) monoclinic P2(1)/a, a = 23.8275(4) A, b = 9.1015 (2) A, c = 27.0420(1) A, beta = 99.9297(8) degrees, Z = 4, R = 0.0530 for 4565 independent reflections with I > 2 sigma(I). The crystal structures for both compounds consist of alternating organic and inorganic layers. The organic layer in compound 1 is characterized as kappa-type, while the organic layer in 2 resembles the kappa-type but it contains orthogonal dimers and monomers, and it is therefore called kappa(21). Compound 1 shows metallic behavior down to low temperature. Salt 2 shows semiconductive behavior, which is explained as the result of either charge ordering owing to the kappa(21)-type structure or Peierls distortion due to the one-dimensional electronic nature. However, weak metallic behavior could be observed at 10 kbar above ca. 150 K and at 15 kbar above 170 K. The magnetic susceptibilities for both compounds show Curie-Weiss behavior, showing that the exchange interactions between the magnetic anions are weak. Polarized reflectance spectra of single crystals were measured over the spectral range from 650 to 7000 cm(-1). Moreover, absorption and diffusion reflectance spectra of powdered crystals dispersed in KBr (from 400 to 7000 cm(-1)) were recorded. Vibrational and electronic features are discussed.     

Direct Lanthanide-Transition Metal Interactions: Synthesis of (NH(3))(2)YbFe(CO)(4) and Crystal Structures of {[(CH(3)CN)(3)YbFe(CO)(4)](2).CH(3)CN}(infinity) and [(CH(3)CN)(3)YbFe(CO)(4)](infinity)

The heterometallic complex (NH(3))(2)YbFe(CO)(4) was prepared from the reduction of Fe(3)(CO)(12) by Yb in liquid ammonia. Ammonia was displaced from (NH(3))(2)YbFe(CO)(4) by acetonitrile in acetonitrile solution, and the crystalline compounds {[(CH(3)CN)(3)YbFe(CO)(4))](2).CH(3)CN}(infinity) and [(CH(3)CN)(3)YbFe(CO)(4)](infinity) were obtained. An earlier X-ray study of {[(CH(3)CN)(3)YbFe(CO)(4)](2).CH(3)CN}(infinity) showed that it is a ladder polymer with direct Yb-Fe bonds. In the present study, an X-ray crystal structure analysis also showed that [(CH(3)CN)(3)YbFe(CO)(4)](infinity) is a sheetlike array with direct Yb-Fe bonds. Crystal data for {[(CH(3)CN)(3)YbFe(CO)(4)](2).CH(3)CN}(infinity): monoclinic space group P2(1)/c, a = 21.515(8) ?, b = 7.838(2) ?, c = 19.866(6) ?, beta = 105.47(2) degrees, Z = 4. Crystal data for [(CH(3)CN)(3)YbFe(CO)(4)](infinity): monoclinic space group P2(1)/n, a = 8.364(3) ?, b = 9.605(5) ?, c = 17.240(6) ?, beta = 92.22(3) degrees, Z = 4. Electrical conductivity measurements in acetonitrile show that these acetonitrile complexes are partially dissociated into ionic species. IR and NMR spectra of the solutions reveal the presence of [HFe(CO)(4)](-). However, upon recrystallization, the acetonitrile complexes show no evidence for the presence of [HFe(CO)(4)](-) on the basis of their IR spectra. The solid state MAS (2)H NMR spectra of deuterated acetonitrile complexes give no evidence for [(2)HFe(CO)(4)](-). It appears that rupture of the Yb-Fe bond could occur in solution to generate the ion pair [L(n)Yb](2+)[Fe(CO)(4)](2-), but then the highly basic [Fe(CO)(4)](2-) anion could abstract a proton from a coordinated acetonitrile ligand to form [HFe(CO)(4)](-). However, upon crystallization, the proton could be transferred back to the ligand, which results in the neutral polymeric species.     

Synthesis, NMR Study, and Reactivity of Isomeric Early-Late Heterobimetallic Dihydrides. X-ray Crystal Structure of (PPh(3))HRu(&mgr;-H)(&mgr;-PMe(2)C(5)Me(4))(2)(&mgr;-Cl)ZrCl

The new isomeric ruthenium/zirconium dihydrides of the formula (PPh(3))HRuH(&mgr;-PMe(2)Cp)(2)ClZrCl (1, 2) (Cp = C(5)Me(4)) have been characterized by elemental analysis and NMR ((1)H, (31)P and (1)H relaxation data). Complex 1, stabilized by Cl and H bridges, has been isolated from the room temperature reaction between RuH(2)(H(2))(PPh(3))(3) and (PMe(2)Cp)(2)ZrCl(2). The X-ray crystallographic study of 1 revealed a bimetallic complex. The six-coordinate Ru atom and the five-coordinate Zr atom are held together by two bifunctional phosphinocyclopentadienyl ligands and by H and Cl bridges. Crystal data for 1: monoclinic space group P2(1)/c, a = 13.901(2) ?, b = 18.205(6) ?, c = 16.633(3) ?, beta = 92.43(1) degrees, V = 4206 ?(3), Z = 4, d(calc) = 1.472 g cm(-)(3), R(F) = 0.056, R(w)(F) = 0.058. Complex 2 with two H bridges and terminal Cl ligands at Ru and Zr has been obtained by an irreversible isomerization of 1 in the presence of HNEt(3)BPh(4). This transformation has been proposed to occur through slow protonation of one of the phosphorus ligands with the five-coordinate Ru center formed by undergoing rapid pseudorotation. Complexes 1 and 2 do not react with H(2), N(2), or 3,3-dimethyl-but-1-ene. Treatment of 1 with 1 equiv of NaHBEt(3) in C(6)D(6) gives a mixture of new trihydrides (PPh(3))HRu(&mgr;-Cl)(&mgr;-H)(&mgr;-PMe(2)Cp)(2)ZrH (3) and (PPh(3))HRu(&mgr;-H)(2)(&mgr;-PMe(2)Cp)(2)ZrCl (4). Complex 3 transforms to 4 upon standing in solution for a period of several days. Under the same conditions, complex 2 leads smoothly to trihydride 4. Both trihydrides are new and have been characterized by (1)H, (31)P NMR, and (1)H NMR relaxation data. Complexes 1 and 4 are fluxional in solution at room temperature, showing hydride exchange between the terminal and bridging positions. The variable-temperature (1)H NMR spectra allowed determinations of the DeltaG() values of 16.4 (313 K, THF-d(8)) and 13.5 kcal/mol (295 K, toluene-d(8)) for the exchange in complexes 1 and 4, respectively. Possible exchange mechanisms have been discussed. Complex 2 is rigid on the NMR time scale.     

The preparation and crystal structure of trinuclear molybdenum compound (Me4N)[Mo3(μ3-O)(μ-Cl)3(μ-O2CH)3Cl3]

The title compound was prepared by the oxidation of MoCl₃ in liquid phase. The crystal belongs to the orthorhombic system with space group D-Pmnb and unit cell parameters: a = 11.403 (1), b = 12.345 (2), c = 14.292 (2) Å; V = 2011.8 ų; Z = 4, D_c = 2.396g/cm³. Altogether 2303 independent reflections were collected on a CAD-4 four-circle diffractometer with Mo Kα radiation in range 2° ≤ θ ≤ 27°. The crystal structure was solved by heavy-atoms method and refined by full-matrix least-squares technique to final discrepancy factors R = 0.050 and R_w= 0.056 for 1513 reflections of I ≥ 3σ (I). The configuration of the cluster anion was characterized to be of the same Ml type structure as presented in the previous paper. The average bond lengths of Mo—Mo and Mo-(μ₃-O) are 2.577 Å and 1.982 Å respectively. In addition, the effects of bridging atoms, other ligands and bond orders on Mo—Mo bonds are discussed briefly.