Spectroscopy and MLCT photochemistry of [(CO)5MM′(CO)3(α-diimine] (M,M′Mn,Re) complexes

Resonance Raman (rR) and Ultraviolet Photoelectron (UP) spectra are reported for the complexes [(CO)₅MM′(CO)₃(α-diimine)] (M,M'Mn,Re) which all possess an intensive absorption band in the visible region. The rR spectra show that this band has to be reassigned to a d_Π(M′)→Π* (α-diimine) transition. These results as well as those obtained from the UP spectra have been used to derive and energy vs distortion diagram by which the various photochemical reactions can be understood.     

紫外激光诱导C60与M(CO)6(M=Cr,Mo, W)的配位反应

研究了用紫外激光(355 nm)诱导C_(60)与金属羰基化合物M(CO)_6(M＝Cr；Mo，W)的配位反应，合成了具有C_(4υ)对称性的配位络合物(η~2－C_(60))M(CO)_5，并初步讨论了C_(60)与M(CO)_6反应的动力学过程．     

金属羰基化合物M(CO)6(M=Cr,Mo, W)氧原子转移反应动力学与机理

本文研究了PPh3存在与不存在的情况下, M(CO)6(M=Cr, Mo, W)与三甲胺氧化物me3NO在CH2Cl2中的氧原子转移反应动力学. 反应速率遵循: r=k[M(CO)6][Me3NO], 并且rW>rMo>rCr, 并根据实验结果提出了反应机理, 讨论了溶剂对反应速率的影响.     

Darstellung und reaktionen von diphosphen-komplexen RPPR[M(CO)5]3 (M = Cr,Mo, W)

Decacarbonyldimetallates Na₂M₂(CO)₁₀ (M = Cr, Mo, W) react with dihalophosphanes, (R)P(Cl)₂, to yield trinuclear diphosphene complexes of the form RPPR[M(CO)₅]₃. The by-products of these reactions are diphosphane- and phosphido-bridged complexes.The trinuclear diphosphene compounds add HX (X = CH₃COO, CH₃O) or dienes to the PP double bond; in the course of these additions one M(CO)₅ group is cleaved and binuclear derivatives of diphosphanes are obtained.     

Synthesis and characterisation of [AgL(μ-PR2)M(CO)5], L= 1,10-phenanthroline or tricyclohexylphosphine; M = Cr,Mo, W

The new heterobimetallic phosphide-bridged compounds [AgL(μ-PR₂)M(CO)₅], (L = 1,10-phenanthroline or tricyclohexylphosphine: M = Cr, M, W) have been prepared from AgO₃SCF₃, M(CO)₅PR₂H and the ligand L in the presence of Et₂NH or MeO⁻ as base, and characterized by ³¹P NMR spectroscopy.     

RuH3[P(C6H5)3] 3 − as a ligand in complexes withM(CO)3 Fragments (M = Cr,Mo, W)

The reactions of RuH₃[P(C₆H₅)₃] ₃ ^– with Cr(CO)₃(CH₃CN)₃, Mo(CO)₃ (diglyme), or W(CO)₃(C₃H₂CN)₃ resulted in the formation of the appropriate [(H₅C₆)₃P]₃Ru(-H)₃ M(CO) ₃ ^– complexes, which have been characterized analytically, spectroscopically, and in one case (M = Cr) by an X-ray diffraction study of the K [N(C₂H₄OC₂H₄OCH₃)₃]⁺ salt. This complex crystallizes in the triclinic space group Pl witha = 13.666(6),b= 13.7901(7),c = 18.147(8) A,a = 93.23(3)°, = 94.07(4)° = 90.43(4)°, andV = 3405.6 A³ for Z = 2. Final discrepancy indices ofR = 0.048 and Rù = 0.056 were obtained. The hydride ligands, all of which could be located and their positional coordinates refined, completed local pseudo-octahedral coordination about both the ruthenium and thechromium centers. The Ru-H bonds are significantly shorter than the Cr-H ones, 1.65(4) vs. 1.92(4) A, and the Ru-Cr bond distance is 2.5474(9) A.     

Carbonylmetall-verbindungen des bis(di-t-butylphosphino)schwefeldiimids: Bildung von zweikernkomplexen S{NPtBu2[MLn]}2 (MLn = Cr(CO)5), Mo(CO)5, W(CO)5, Fe(CO)4) und chelatkomplexen S(NPtBu2)2M(CO)4 (M = Cr,Mo, W). Kristall- und molekülstruktur von S(NPtBu2)2Cr(CO)4

The reaction of bis(di-t-butylphosphino) sulphur diimide, S(NP^tBu₂)₂ (1) ¹, with coordinatively unsaturated 16-electron complex fragments [M(CO)₅] leads to both binuclear 1 : 2 adducts S{NP^tBu₂[M(CO)₅]}₂ (M = Cr (2B), Mo (3B) and W (4B)) and mononuclear chelate complexes S(NP^tBu₂)₂M(CO)₄ (M = Cr (2C), Mo (3C) and W (4C)). A binuclear compound S{NP^tBu₂[Fe(CO)₄]}₂ (5B) is obtained from the reaction of 1 with Fe₂(CO)₉. The new complexes which all contain the intact sulphyr diimide 1 are characterized on the basis of their infrared, ¹H, ¹³C and ³¹P NMR spectra. An X-ray structure analysis of S(NP^tBu₂)₂Cr(CO)₄ (2C) reveals a distorted octahedral coordination sphere around the central chromium atom and an almost planar but twisted six-membered Cr(PN)₂S heterocycle with angles of 91.98(2)° at chromium (P(1)CrP(2)) and 124.6(1)° at sulphur (N(1)SN(2)).     

Photochemical reactions of M(CO)5THF (M = Cr, Mo, W) with thio Schiff bases

The hitherto unknown complexes, [M₂(CO)₆(μ-CO)(μ-L)], [M = Cr; 1, Mo; 2, W; 3] and [M₂(CO)₆(μ-CO)(μ-L′)], [M = Cr; 4, Mo; 5, W; 6] have been synthesized by the photochemical reactions of photogenerated intermediate, M(CO)₅THF (M = Cr, Mo, W) with thio Schiff base ligands, N,N′-bis(2-aminothiophenol)-1,4-bis(2-carboxaldehydephenoxy)butane (H ₂ L) and N,N′-bis(2-aminothiophenol)-1,7-bis(2-formylphenyl)-1,4,7-trioxaheptane (H ₂ L′). The complexes have been characterized by elemental analysis, LC-mass spectrometry, magnetic studies, FT-IR and ¹H NMR spectroscopy. The spectroscopic studies show that H ₂ L and H ₂ L′ ligands are converted to benzothiazole derivatives, L and L′ after UV irradiation and coordinated to the central metal as bridging ligands via the central azomethine nitrogen and sulphur atoms in 1–6.     

184(m,g)Re cross sections and isomeric ratios in181Ta(α, n) and W(α, pxn) reactions

Excitation functions and isomeric ratios for¹⁸⁴Re, from -induced reactions on¹⁸¹Ta and natural W have been measured using the stacked-foil method. The data are compared with the theoretical predictions provided by the equilibrium and pre-equilibrium reaction model; for this propose we used the code INDEX development by ERNST.     

Electronic Structure of TiAl-2M(M=V,Nb,Ta,Cr,Mo,W,Mn) Alloy

1INTRODUCTIONTitaniumaluminidesbasedonY-TiAlarereceivingconsiderableattentionaspo-tentialcandidatesformaterialsinhightemperatureaerospaceapplication.Theirlowdensity,hightemperaturescreepresistance,highoxidationresistanceandstrengthmakesthemexcellentpotentialenginematerials.Howevertheirlowductilityandlowfracturetoughnessatroom'temperaturesaremajorhindrancestotheirpracticaluti-lization.TheTiAlalloymayhaveanelongationabout2%t'},furtherimprovementisnecessarybeforethesematerialscouldbeusedin…     

SiO2负载的Pt-M(M=Cr,Mo,W)配合物双功能催化剂

过渡金属异双核金属有机化合物的研究是一个活跃的领域,人们期望从中制取对极性小分子(如CO,CO2等)具有双功能活化的催化剂.周期表前区过渡金属或稀土元素(如Ti,Zr,Mo,La,Ce等)作为添加组分可明显地增加SiO2负载的铑催化剂催化CO氢化反应的活性和含氧化合物的选择性[1].虽然一些异双核金属氢基羰基化合物已被合成和表征[2],但是关于SiO2负载的异双核金属配合物催化剂的研究还未见文献报道.我们合成、表征了(PPh3)HPt(μ-PPh2)(μ-CO)M(CO)4(M=Cr,Mo,W)异双核配合物[3](I).本文研究了SiO2负载的该配合物催化剂对CO氢化反应和对丙烯氢甲酰化反应的两种催化功能.     

Spectroscopic investigation and thermal behavior of new carbonyl complexes [M(CO)4(N—N)(CuX)], (M = W,Mo; N—N = 2,2′-bipyridine, 1,10-phenanthroline; X = Cl,SCN)

[M(CO)₄(N—N)] reacts with CuCl to give new heterobimetallic metal carbonyls of the type [M(CO)₄(N—N)(CuCl)], M = W, Mo; N—N = 2,2-bipyridine (bipy), 1,10-phenanthroline (phen). Reactions of [M(CO)₄(N—N)(CuCl)] with NaSCN produced the series of complexes of general formula [M(CO)₄(N—N)(CuSCN)]. The i.r. spectral of all the bimetallic carbonyls exhibited the general four (CO) band patterns of the precursors. The u.v.–vis. spectral data for precursors and products showed bands associated with * (nitrogen ligands), dd (intrametal), as well as MLCT d* (nitrogen ligands) and MLCT d *(CO) transitions. The [M(CO)₄(N—N)(CuX)] (X = Cl, SCN) emission spectra showed only one band associated with the MLCT transition. The t.g. curves revealed a stepwise loss of CO groups. The initial decomposition temperatures of the [M(CO)₄(N—N)(CuX)] series suggest that the bimetallic compounds are indeed thermally less stable than their precursors, and the X-ray data showed the formation of MO₃, CuMO₄, Cu₂O and CuO as final decomposition products, M = W, Mo. The spectroscopic data suggests that the heterobimetallic compounds are polymeric.     

Synthesis, structures, and properties of molybdenum and tungsten chalcogenide cubane complexes (NH4)6[M4Q4(CN)12]·6H2O (M=Mo or W; Q=S or Se)

Four new chalcogenide molybdenum and tungsten cubane clusters (NH₄)₆[M₄Q₄(CN)₁₂]·6H₂O (M=Mo or W; Q=S or Se) were prepared by high-temperature reactions of the triangular M₃O₇Br₄ complexes with KCN at 430 °C followed by crystallization from aqueous solutions of ammonium acetate. The molecular and crystal structures of (NH₄)₆[Mo₄S₄(CN)₁₂]·6H₂O, (NH₄)₆[W₄S₄(CN)₁₂]·6H₂O, and (NH₄)₆[W₄Se₄(CN)₁₂]·6H₂O were established by X-ray diffraction analysis. The mixed-valence cubane clusters are diamagnetic and isostructural and have the symmetryT _d . The clusters were characterized by IR and electronic spectroscopy. The data of cyclic voltammetry demonstrated that the [M₄Q₄(CN)₁₂] ⁿ⁻ clusters exist in three oxidation states from the most oxidized (n=6; 10 cluster electrons) to the most reduced electron-precise 12-electron species (n=8). Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 18–24, January, 2000.     

Electronic Structures, (d-p)π Conjugation Effects, and Spectroscopic Properties of Polyoxometalates: M6O19 2− (M=Cr, Mo, W)

The electronic structures and bonding of isopoly oxometalates M₆O₁₉ ^2– (M=Cr, Mo, W) have been investigated by using ab initio and relativistic density functional methods. We have discussed the role of the central oxygen atom and the (d-p) conjugation interactions between the metal and bridging oxygen atoms. It is found that there exist 12 three-centered two-electron (d-p-d) bonds for the three M₄(-O)₄ planar rings in M₆O₁₉ ^2– ions and these hexametalates are considered to have quasi-aromaticity. The (d-p) conjugation effects play essential role in stabilizing these cluster compounds, and the reduced (d-p) conjugation effects account for the instability of the isopoly oxochromate ion, Cr₆O₁₉ ^2–. The vibrational spectra and electronic spectra of M₆O₁₉ ^2– ions are evaluated and assigned theoretically and the calculated spectra are in fairly good agreement with the measured experimental results.     

Reactivity of [M(CO)3(NN)(thioureas)] (M = Mo,W; NN = 2,2′bipyridine, 1,10-phenanthroline) complexes towards systems with mercury-halides bonds. Trimetallic compounds with XMHgM′X (M′ = Mo,W; X = Cl,Br, I) bondings

New heterotrimetallic complexes were isolated by reaction of M(CO)₃(NN)L (M = Mo, W; NN = bipy, phen; L = thioureas) either with HgX₂ (X = Cl, Br, I) giving complexes of the formula [M(CO)₃(NN)(X)]₂Hg or with M′(CO)₃(NN′)(Cl)(HgCl) (M′ = Mo, W; NN′ = bipy, phen) producing compounds of the type (Cl)(NN)(CO)₃MHgM′(CO)₃(NN′)(Cl). These new photosensitive substances were characterized through IR spectroscopy and conductivity measurements. Structures involving XMHgM′X bonding are proposed and the reactions are discussed in terms of an insertion of the fragment M(CO)₃(NN) into the HgX bonds.     

Potassium Cationic Conduction in K3 – xP1 – xExO4 (E = S,Cr, Mo,W)

Solid solutions of cubic structure based on K₃PO₄are synthesized in the systems K_{3 – x} P_{1 – x} E _x O₄(E = S, Cr, Mo, W). Approximate boundaries of single-phase regions and the temperature and concentration dependences of electroconductivity are studied. The transport numbers, measured by a modified Tubandt method, confirm a potassium cationic character of conduction. Electric parameters of the electrolytes are compared with those of sodium and rubidium conducting solid solutions in similar systems. Factors that affect transport properties of synthesized phases are discussed.     

The photo-induced decarbonylation of Cp′M(NO)(CO)2 (M = Cr,Mo, W) with diorgano dichalcogenides (R2E2; E = S,Se; R = Me,Ph)

The photo-induced decarbonylation of CpCr(NO)(CO)₂ (1a) in MeCN solution in the presence of R₂E₂ (E = S, Se; R = Me, Ph) leads to the formation of chalcogenolato-bridged binuclear complexes Cp₂Cr₂(NO)₂(-ER)₂ [E = S; R = Me (2a), Ph (3a); E = Se, R = Me (4a), Ph (5a)] while reactions between CpM(NO)(CO)₂ [M = Mo (1b), W (1c)] and Ph₂E₂ (E = S, Se) result in mononuclear complexes CpM(NO)(EPh)₂ [M = Mo; E = S (9b), Se (10b); M = W, E = S (11c), Se (12c)]. The corresponding reactions of (1b) with Me₂E₂ (E = S, Se) yielded both mono and binuclear complexes: CpMo(NO)(SeMe)₂ (8b), Cp₂Mo₂(NO)₂(-EMe)₂ [E = S (6b), Se (7b)]. The new complexes have been characterized by i.r., ¹H-, ¹³C-n.m.r. spectra and by electron-impact mass spectrometry.     

Carbene complexes of molybdenum and tungsten Et3E-CH=M(NAr)(OR)2 (M = Mo, W; E = Si, Ge) and π-complex of molybdenum (RO)2(ArN)Mo(CH2=CH-GeEt3). Synthesis and catalytic properties

The heteroelement-containing alkylidene imide complexes with molybdenum and tungsten Et₃SiCH=Mo(NAr)(OR)₂ (I), Et₃ ECH=W(NAr)(OR)₂ (E = Si (II), Ge (III); Ar = 2,6-i-Pr₂C₆H₃; R=CMe₂ CF₃) and π-complex (RO)₂(ArN)Mo(CH₂=CH-GeEt₃) (IV) were synthesized by the reaction of Alkyl-CH=M(NAr) (OR)₂ (M=Mo, W; Alkyl = t-Bu, PhMe₂C) with organosilicon and organogermanium vinyl reagents Et₃ECH=CH₂ (E = Si, Ge). The structure of compounds I–III was determined by X-ray diffraction (XRD). The complexes I–IV are active initiators of metathesis polymerization of cycloolefins.