The oxidative addition of hydrogen sulfide to the electron-rich triple bond: The isolation and characterization of compounds that contain the Re2(μ-H)(μ-SH) cluster unit

The reactions of Re₂X₄(-dppm)₂ (X=Cl or Br; dppm=Ph₂PCH₂PPh₂) with H₂S in THF afford the dirhenium (III) complexes Re₂(-H)(-SH)X₄(-dppm)₂, the first examples of the oxidative addition of an S-H unit across an electron-rich metal-metal triple bond. The bromide complex Re₂(-H)(-SH)Br₄(-dppm)₂ (C₂H₅)₂O crystallizes in the space group P2₁/n witha=16.631(2) Å,b=15.967(3) Å,c=19.904(2) Å, =92.698(7)°,V=5279(2) ų, andZ=4. The structure which was refined toR=0.053 (R _w=0.070) for 4903 data withI>3.0(I), shows the presence of an edge-shared bioctahedral geometry with a very short Re-Re distance of 2.4566(7) Å. While the hydrogen atoms of the -H and -SH ligands were not located in the X-ray structure determination, their presence is confirmed by IR and¹H NMR spectroscopy.     

The oxidative conversion of the N,S-bridged complexes [{RhLL'(μ-X)}2] to [(RhLL')3)(μ-X)2]+ (X = mt or taz): a comparison with the oxidation of N,N-bridged analogues

The structures of [{RhLL'(μ-X)}(2)] [LL' = cod, (CO)(2), (CO)(PPh(3)) or {P(OPh)(3)}(2); X = mt or taz], prepared from [{RhLL'(μ-Cl)}(2)] and HX in the presence of NEt(3), depend on the auxiliary ligands LL'. The head-to-tail arrangement of the two N,S-bridges is accompanied by a rhodium-eclipsed conformation for the majority but the most hindered complex, [{Rh[P(OPh)(3)](2)(μ-taz)}(2)], uniquely adopts a sulfur-eclipsed structure. The least hindered complex, [{Rh(CO)(2)(μ-mt)}(2)], shows intermolecular stacking of mt rings in the solid state. The complexes [{RhLL'(μ-X)}(2)] are chemically oxidised to trinuclear cations, [(RhLL')(3)(μ-X)(2)](+), most probably via reaction of one molecule of the dimer, in the sulfur-eclipsed form, with the fragment [RhLL'](+) formed by oxidative cleavage of a second.     

The isolation and characterization of the first examples of pairs of α- and β-isomers of dirhenium(II) of type Re2X4(LL)2 (X = Cl or Br,LL = bidentate phosphine ligand)

The complexes Re₂Br₄(depe)₂ and Re₂X₄(dppee)₂ (X = Cl or Br, depe = Et₂PCH₂CH₂PEt₂, dppee = cis-Ph₂PCHCHPPh₂) have been prepared in their α- (eclipsed rotational geometry, chelating phosphine ligands) and β- (staggered rotational geometry, bridging phosphine ligands) isomeric forms. The chloro complex β-Re₂Cl₄(depe)₂ has also been isolated. In the case of α- and β- Re₂Br₄(depe)₂, the preparations involve the reactions of Re₂Br₄(P-n-Pr₃)₄ with depe in toluene-ethanol. While α-Re₂X₄(dppee)₂ are prepared from the reactions of (n-Bu₄N)₂Re₂X₈ with dppee in various solvents, the β-isomers are obtained upon reacting Re₂X₄(PR₃)₄ (R = Et or n-Pr) with dppee in benzene. These are the first examples of triply bonded dirhenium(II) complexes that have been isolated in both their α- and β-forms. β-Re₂X₄(dppee)₂ (X = Cl or Br) constitute the first examples of complexes of this structural type which contain both CC and MM units within the same fused decalin-like ring system. The isomers β-Re₂Cl₄(depe)₂ and β-Re₂X₄(dppee)₂ (X = Cl or Br) are oxidized by NOPF₆ in acetonitrile to give paramagnetic β-[Re₂Cl₄(depe)₂]PF₆ and β-[Re₂X₄(dppee)₂]PF₆. These oxidized complexes in turn react with CH₃CN in the presence of T1PF₆ to afford β-[Re₂Cl₃(depe)₂(NCMe)](PF₆)₂ and β-[Re₂X₃(dppee)₂(NCMe)](PF₆)₂, respectively. The cleavage of the ReRe bonds of α- and β-Re₂Cl₄(dppee)₂ occurs upon their reaction with CCl₄-CH₂Cl₂ to give cis-ReCl₄(dppee). The related bromo complex cis-ReBr₄(dppee) is formed when β-Re₂Br₄(dppee)₂ is reacted with CH₂Cl₂-Br₂.     

Aqueous redox chemistry of dinuclear clusters. A mechanistic study of proton oxidative addition to the Mo2Cl84− ion and the homogeneous reduction of Mo2(μ-X)(μ-Cl)2 Cl63−, X = H,Cl by aqueous chromium(II)

The kinetics of the oxidative addition of hydrochloric acid (6–12 M) to the quadruply bonded Mo₂Cl₈⁴⁻ ion, 1, to produce the triply bonded hydride Mo₂(μ-H) (μ-Cl)₂(Cl)₆³⁻, 2, are first order in the concentration of the acid, and first order in the Mo₂⁴⁺ reactant. The rate is strongly affected by axial coordination. At lower acid concentrations (< 6 M) the reaction is complicated by hydrolysis. The hydride 2 and the analogous nonachlorodimolybdate Mo₂(μ-Cl)₃Cl₆³⁻, 3, undergo a two-electron reduction by chromous chloride in HCl (6M) to give 1 ; the Mo₂⁶⁺/Mo₂⁴⁺ couple catalyses the anaerobic oxidation of Cr(II) to Cr(III).     

Co-ordinatively unsaturated metal cluster compounds: Facile reactivity of the phosphinidene-capped phosphido-bridged triruthenium cluster [Ru3(μ3-PPh)(μ2-PPh2)2(CO)7]

The purple, phosphinidene-capped, phosphido-bridged triruthenium cluster [Ru₃(μ₃-PPh)(μ₂-PPh₂)₂(CO)₇] reacts readily with carbon monoxide, trimethylphosphite, sodium borohydride and diphenylacetylene under mild conditions to afford product mixtures from which [Ru₃(μ-PPh)(μ₂-PPh₂)₂(CO)_7+n] (n = 1, 2 or 3), [Ru₃(μ₃-PPh)(μ₂-PPh₂)₂(CO)₆{P(OMe)₃}], [Ru₃(μ₃-η³-PhPCPhCPh)(μ₂-PPh₂)₂(CO)₆], respectively, can be isolated. The structure of [Ru₃(μ₃-PPh)(μ₂-PPh₂)₂(CO)₆{P(OMe)₃}] has been established X-ray crystallographically.     

Preparation and structural characterization of the isomorphous compounds: [Bu4N][Mo3(μ3-O)(μ-X)3(μ-OAc)3 X 3]·(CH3)2CO,X=Cl,Br

The reaction of MoCl₃(H₂O)₃ with a mixture of acetic acid and acetic anhydride in the presence of [N(C₄H₉)₄][BF₄] followed by crystallization from acetone/hexane gives a 77% yield of dark purple [NBu₄][Mo₃OCl₆(OAc)₃]·Me₂CO (1). A similar reaction employing MoBr₃(H₂O)₃ gives purple [NBu₄][Mo₃OBr₆(OAc)₃]·Me₂CO (2) in 50% yield. Also produced in this reaction in low (10–20%) yields are [NBu₄]₂[Mo₄OBr₁₂] · 0.5Me₂CO and [NBu₄]₂[Mo₃OBr₆(OAc)₃] · Me₂CO which will be discussed elsewhere Compounds (1) and (2) are isomorphous, space groupP2₁/n,Z=4 with the following unit cell dimensions, where the values for (1) and (2) are given in that order for each one:a=13.406(4), 13.726(5) Å;b=15.701(4), 15.839(5) Å;c=19.250(5), 19.831(6) Å; =101.61(2), 102.92(3)°. Both (1) and (2) are eight-electron species in which the mean Mo-Mo distances are 2.578(1) Å and 2.597(1) Å, respectively.     

Chemistry of iridium carbonyl cluster complexes. Synthesis,characterization and solid state structure of the phosphido carbonyl cluster [Ir6(CO)12(μ-CO)2(μ-PPh2)−

The phosphido-bridged cluster [Ir₆(CO)₁₄ PPh2]^– has been obtained by reaction of [Ir₆(CO)₁₅]^2– with PHPh₂, in the presence of ferrocenium cation, followed by deprotonation. The anion was isolated as a salt of [N(PPh₃)₂]⁺ or K⁺ and its structure was determined by single crystal X-ray data analysis. The salt [N(PPh₃)₂][Ir₆(CO)₁₄PPh₂] crystallizes in the triclinic space group P witha = 11.835(1) Å,b = 15.007(1) Å,c = 18.766(2)_ Å; = 78.779(7)°, = 87.260(8)°, = 75.794(6)°,V = 3169.3(7) Å,Z = 2. The structure was solved by Direct Methods and Difference Fourier techniques and refined down toR andR _w values of 0.034 and 0.036, respectively, for 8003 observed reflections havingl > 3(I). The octahedral anion, of idealized C₂ symmetry, possesses two distance Ir-P = 2.284 Å, formally acting as a three electron donor. Average bond distances (Å) and angles (degrees) are: Ir-Ir = 2.776, Ir-C _t = 1.87, Ir-C _b = 2.05, C _t -O _t = 1.14, C _b -O_b= 1.17, Ir-P-Ir = 74.3°, Ir-C _t -O _t = 177°, Ir-C _b -O _b = 138°, Ir-C _b -Ir = 84° (t = terminal,b = bridging).     

The effects of redox-inactive metal ions on the activation of dioxygen: isolation and characterization of a heterobimetallic complex containing a Mn(III)-(μ-OH)-Ca(II) core

Rate enhancements for the reduction of dioxygen by a Mn(II) complex were observed in the presence of redox-inactive group 2 metal ions. The rate changes were correlated with an increase in the Lewis acidity of the group 2 metal ions. These studies led to the isolation of heterobimetallic complexes containing Mn(III)-(μ-OH)-M(II) cores (M(II) = Ca(II), Ba(II)) in which the hydroxo oxygen atom is derived from O(2). This type of core structure has relevance to the oxygen-evolving complex within photosystem II.     

Further Aspects of the Chemistry of the Dirhenium Complexes [(triphos)Re(μ-X)3Re(triphos)]n+ (n=1 or 0), Where triphos=CH3C(CH2PPh2)3 and X=Cl or Br

The dirhenium(II) complexes [Re₂(-X)₃(triphos)₂]O₃SCF₃ (X=Cl or Br) have been prepared by anion exchange reactions. These salts show well defined simple electron-transfer redox chemistry (two reversible one-electron oxidations and two one-electron reductions) but the [Re(-X)₃Re] unit is remarkably stable to reactions with donor molecules such as monodentate tertiary phosphines which can often induce cleavage of M-X-M bridges. The crystallographic characterization of these two salts show that Re–Re bonds are not present, the Re...Re distances being 3.274(1) Å for X=Cl and 3.277(1) Å for X=Br.     

Microwave Promoted Oxidative Addition Reactions of Os3(CO)12: Efficient Syntheses of Triosmium Clusters of the Type Os3(μ-X)2(CO)10 and Os3(μ-H)(μ-OR)(CO)10

Microwave heating allows for the high-yield, one-step synthesis of the known triosmium complexes Os₃(μ-Br)₂(CO)₁₀ (1), Os₃(μ-I)₂(CO)₁₀ (2), and Os₃(μ-H)(μ-OR)(CO)₁₀ with R = methyl (3), ethyl (4), isopropyl (5), n-butyl (6), and phenyl (7). In addition, the new clusters Os₃(μ-H)(μ-OR)(CO)₁₀ with R = n-propyl (8), sec-butyl (9), isobutyl (10), and tert-butyl (11) are synthesized in a microwave reactor. The preparation of these complexes is easily accomplished without the need to first prepare an activated derivative of Os₃(CO)₁₂, and without the need to exclude air from the reaction vessel. The syntheses of complexes 1 and 2 are carried out in less than 15 min by heating stoichiometric mixtures of Os₃(CO)₁₂ and the appropriate halogen in cyclohexane. Clusters 3–6 and 8–10 are prepared by the microwave irradiation of Os₃(CO)₁₂ in neat alcohols, while clusters 7 and 11 are prepared from mixtures of Os₃(CO)₁₂, alcohol and 1,2-dichlorobenzene. Structural characterization of clusters 2, 4, and 5 was carried out by X-ray crystallographic analysis. High resolution X-ray crystal structures of two other oxidative addition products, Os₃(CO)₁₂I₂ (12) and Os₃(μ-H)(μ-O₂CC₆H₅)(CO)₁₀ (13), are also presented.     

The preparation and structure of the tetranuclear ruthenium cluster [Ru4(CO)10(μ2-Cl)2(μ3-OEt)2]

The tetranuclear ruthenium cluster [Ru₄(CO)₁₀Cl₂(OEt)₂] has been prepared in low yield by the reaction of [Ru₃(CO)₁₂] with [N(PPh₃)₂]Cl in refluxing EtOH, followed by oxidation with either [NO][BF₄] or Ag[ClO₄]. A single-crystal X-ray analysis of the complex shows that the four metal atoms adopt a planar geometry with one ruthenium bonded by two μ₂-Cl ligands and two μ₃-OEt ligands to a trinuclear fragment. This complex crystallises in the monoclinic space group I2/c, with a 14.458(3), b 22.073(6), c 15.302(4) Å, β 99.54(2)°, Z = 8; 3113 observed data with F > 3σ(F) were refined by blocked full-matrix least squares to R = 0.031, R_w = 0.034.     

Synthesis of Co3(CO)7(μ-η3-Allyl)(μ3-X) Complexes (X=S, Se) and Structure of the Selenium Derivative

The complexes Co₃(CO)₉( ₃-X) (X=S, Se) can be reduced to the corresponding anionic species [Co₃(CO)₉( ₃-X)]^–, which react with allyl bromide to give Co₃(CO)₇(- ³-C₃H₅)( ₃-X) (X=S, Se). These are the first two cobalt complexes containing the bridging - ³-allyl ligand. The structure of the selenium complex was determined by X-ray crystallography. Crystal data for Co₃(CO)₇(- ³-C₃H₅)( ₃-Se) are as follows: space group P2₁/c, a=9.051(2) Å, b=8.102(2) Å, c=21.27(4) Å, =93.82(3)°, Z=4, and R=0.0565 for 2491 observed reflections.     

Synthesis and characterization of the new mixed-metal,mixed-chalcogen clusters Fe2 M(CO)10(μ3-S)(μ3-Te) (M=W,Mo). crystal structure of Fe2W(CO)10(μ3-S)(μ3-Te)

The new clusters Fe₂ M(CO)₁₀(µ₃-S)(µ₃-Te), I (M=W) and 2 (M=Mo) have been isolated from the room temperature reaction of Fe₂(CO)₆(µ-STe) andM(CO)₅(THF) (M=W, Mo), respectively. Compounds1 and2 have been characterized by IR, 125 Te NMR spectroscopy, and elemental analysis. The structure of compound1 has been established by X-ray crystallography. It belongs to the triclinic space groupP witha=6.844(2) Å,b=9.397(2) Å,c=13.681(10) Å, =81.64(2)°,=81360r,=812(2)°,V=861.2(3) ų,Z=2,D _e =2.835 g cm^–3. Full-matrix least-squares refinement of1 converged to R=0.043, andR _w .=0.115. The structure consists of a Fe₂ WSTe square pyramid and the W atom occupies the apical site of the square pyramid.     

The applications of hypervalent iodine(Ⅲ) reagents in the constructions of heterocyclic compounds through oxidative coupling reactions

Hypervalent iodine(Ⅲ)reagents have been vastly used in many useful organic transformations.In this review article,we highlight the strategies that used the common hypervalent iodine(Ⅲ)reagents as oxidants to synthesize the heterocyclic compounds,based on the patterns of bond formation during the construction of the heterocyclic backbones.     

Synthesis of the gold-dirhenium ferrocenylacetylide cluster. The crystal structure of Re2(μ-C≡CFc){Au(PPh3)}(CO)8

The thermal reaction of Re₂(CO)₈(NCMe)₂ with Au(CCFc)PPh₃ afforded the cluster Re₂(-CCFc){Au(PPh₃)}(CO)₈, which was characterized by X-ray diffraction analysis.     

The oxidative addition of 1-haloalkanes to monomeric trans-[Rh(X(CO)(PR3)2] (X  Cl,Br; R  aryl) and dimeric trans-[Rh(μ-X)(CO)(PPh3)]2 (XCl,I)

The oxidative addition of 1-bromopropane to trans-[RhBr(CO){P(p-EtC₆H₄)₃}₂] has been found to follow pseudo first-order kinetics and give only an acylrhodium(III) product. The reaction is not catalysed by added bromide ion in chloroform solution, indicating that an anionic intermediate such as [RhBr₂(CO){P(p-EtC₆H₄)₃}]⁻ does not play an important part in this reaction. The oxidative addition of iodomethane to trans-[Rh(μ-X)(CO)(PPh₃)]₂ (X  Cl and I) is pseudo first-order, the reactivity increasing on replacing chloride by iodide.     

Synthesis and structural characterization of the first transition metal cluster containing a PPh2AuPPh3 ligand,Ir4(CO)8(μ-CO)3(PPh2AuPPh3), and its conversion into Ir4(CO)9(μ-CO)(μ-PPh2)(μ-AuPPh3)

Deprotonation of Ir₄(CO)₁₁PPh₂H (1) in the presence of [AuPPh₃][PF₆] yields the novel species Ir₄(CO)₁₁(PPh₂AuPPh₃) (2), which possesses a tetrahedral framework bearing a terminally bound PPh₂AuPPh₃ ligand. When heated in toluene, 2 is converted into the phosphido species Ir₄(CO)₁₀(μ-PPh₂)(μ-AuPPh₃).     

Hydride addition to Ru3(CO)12. Synthesis and characterization of the transient formyl cluster complex Ru3(CO)11(CHO)−

The reaction of Ru₃(CO)₁₂ (1) with LiEt₃BH at −78°C affords the transient cluster formyl complex Ru₃(CO)₁₁(CHO)⁻ (2) which is observed to decompose by CO loss to give the known hydride cluster Ru₃(CO)₁₁(H)⁻ (3) rapidly at temperatures above −50°C. The formyl cluster has been characterized by low temperature FT-IR, ¹H and ¹³C NMR measurements. Formyl trapping experiments and the effect of Bu₃SnH on the rate of formyl decomposition are briefly described.     

Synthesis and X-ray crystal structure of the electron-deficient metal carbonyl cluster [Os3(CO)5(μ3-H)(μ-H)(μ-PtBu2)2(μ-Ph2PCH2PPh2)]

The reaction of [Os₃(CO)₁₀(μ-dppm)] (1) with ^tBu₂PH in refluxing diglyme results in the electron-deficient metal cluster complex [Os₃(CO)₅(μ₃-H)(μ-P^tBu₂)₂(μ-dppm)] (2) (dppm = Ph₂PCH₂PPh₂) in good yields. The molecular structure of 2 has been established by a single crystal X-ray structure analysis. In contrast to the known homologue [Ru₃(μ-CO)(CO)₄(μ₃-H)(μ-H)(μ-P^tBu₂)₂(μ-dppm)] (3), no bridging carbonyl ligand was found in 2. The electronically unsaturated cluster 2 does not react with carbon monoxide under elevated pressure, therefore 2 seems to be coordinatively saturated by reason of the high steric demands of the phosphido ligands.     

Selective two-step oxidation of μ2-S ligands in trigonal prismatic unit {Re3(μ6-C)(μ2-S)3Re3} of the bioctahedral cluster anion [Re12CS17(CN)6]6–

An oxidation of cluster anion [Re(12)CS(17)(CN)(6)](6-) by H(2)O(2) in water has been investigated. It was shown that selective two-step oxidation of bridging μ(2)-S-ligands in trigonal prismatic unit {Re(3)(μ(6)-C)(μ(2)-S)(3)Re(3)} takes place. The first stage runs rapidly, whereas the speed of the second stage depends on intensity of ultraviolet irradiation of the reaction mixture. Each stage of the reaction is accompanied by a change in the solution's color. In the first stage of the oxidation, the cluster anion [Re(12)CS(14)(SO(2))(3)(CN)(6)](6-) is produced, in which all bridging S-ligands are turned into bridging SO(2)-ligands. The second stage of the oxidation leads to formation of the anion [Re(12)CS(14)(SO(2))(2)(SO(3))(CN)(6)](6-), in which one of the SO(2)-ligands underwent further oxidation forming the bridging SO(3)-ligand. Seven compounds containing these anions were synthesized and characterized by a set of different methods, elemental analyses, IR and UV/vis spectroscopy, and quantum-chemical calculations. Structures of some compounds based on similar cluster anions, [Cu(NH(3))(5)](3)[Re(12)CS(14)(SO(2))(3)(CN)(6)]·9.5H(2)O, [Ni(NH(3))(6)](3)[Re(12)CS(14)(SO(2))(3)(CN)(6)]·4H(2)O, and [Cu(NH(3))(5)](2.6)[Re(12)CS(14)(SO(2))(3)(CN)(6)](0.6)[{Re(12)CS(14)(SO(2))(2)(SO(3))(CN)(5)(μ-CN)}{Cu(NH(3))(4)}](0.4)·5H(2)O, were investigated by X-ray analysis of single crystals.