29890-05-9Relevant academic research and scientific papers
Preparation of solid-state samples of a transition metal coordination compound for synchrotron radiation photoemission studies
Crotti, Corrado,Farnetti, Erica,Celestino, Teresa,Fontana, Stefano
, p. 141 - 157 (2003)
The aim of this research was to identify a sample preparation method suitable for the study of transition metal complexes by photoemission spectroscopy with synchrotron radiation as the X-ray source, even in the case where the compound is not evaporable. Solid-phase samples of W(CO)4(dppe) [dppe=1,2-bis(diphenylphosphino)ethane] were prepared according to different methods and their synchrotron radiation XPS spectra measured. The spectra acquired from samples prepared by spin coating show core level peaks only slightly broader than the spectrum recorded from UHV evaporated samples. Moreover, for these samples the reproducibility of the binding energy values is excellent. The dependence of the spin coating technique on parameters such as solvent and solution concentration, spinning speed and support material was studied. The same preparation method also allowed the acquisition of valence band spectra, the main peaks of which were clearly resolved. The results suggest that use of the spin coating technique may allow us to reveal small differences in core level binding energies due to ligand substitution.
Transition metal complexes of (schiff base)divalent group 14 element species [(salen)M](n)=M'(CO)(6-n) (n = 1, 2; M = Ge, Sn, Pb; M'= Cr, W)
Agustin, Dominique,Rima, Ghassoub,Gornitzka, Heinz,Barrau, Jacques
, p. 693 - 702 (2000)
The syntheses, characterization, and reactivities of the new stable mono- and cis-disubstituted Group 14 metal(II) chromium and tungsten carbonyl complexes (salen)M=M'(CO)5 [salen = 2,2'-N,N'- bis(salicylidene)ethylenediamine; M' = Cr, M = Ge (4), Sn (5), Pb (6); M' = W, M = Ge (7), Sn (8), Pb (9)] and [(salen)M]2=M'(CO)4 [M' = W, M = Ge (10), Sn (11), Pb (12); M' = Cr, M = Sn (14), Ge (15)] are described. Complexes 4-9 were obtained in high yields by treatment of the M'(CO)5. THF intermediates with the stable divalent species (salen)M(II) [M = Ge (1), Sn (2), Pb (3)]. Direct irradiation of mixtures of (salen)M(II) and M'(CO)6 resulted in formation of the monosubstituted compounds 4-9 together with the disubstituted species 10-12, 14, and 15 in ratios depending on the nature of both M and M'. Pure complexes 10-12 were obtained by two different synthetic approaches starting from the (salen)M(II) species or the (salen)M=M'(CO)5 complexes. Each of the new complexes has been characterized by 1H- and 13C-NMR, and by 119Sn-NMR in the case of 5, 8, 11, and 14, as well as by IR spectroscopy in all cases. The molecular structures of 5, 8, 11, and 14, determined by X-ray structure analyses, reveal a pentacoordinated tin atom. The tin-chromium distances are among the shortest (in particular that in 5, 2.557 A) observed for transition metal divalent tin complexes and the tin lies about 0.99 A above the plane defined by the O2N2 atoms of the salen ligand. All these complexes have been found to be unreactive towards water and organic acids. Simple phosphane monosubstitution of carbonyl in 8 using Ph3P led to the new complex 13. Reactions with 1,2- bis(diphenylphosphanyl)ethane and 3,5-di-tert-butyl-1,2-benzoquinone resulted in displacement of the divalent species from the carbonyl complexes 5 and 8.
Synthesis, spectroscopy and electronic structure of the vinylidene and alkynyl complexes [W(CCHR)(dppe)(η-C7H7)]+ and [W(CCR)(dppe)(η-C7H7)]n+ (n = 0 or 1)
Lancashire, Hannah N.,Brown, Neil J.,Carthy, Laura,Collison, David,Fitzgerald, Emma C.,Edge, Ruth,Helliwell, Madeleine,Holden, Mark,Low, Paul J.,McDouall, Joseph J. W.,Whiteley, Mark W.
, p. 1267 - 1278 (2011)
The first examples of vinylidene complexes of the cycloheptatrienyl tungsten system [W(CCHR)(dppe)(η-C7H7)]+ (dppe = Ph2PCH2CH2PPh2; R = H, 3; Ph, 4; C6H4-4
Photochemical Unmasking of 1,3-Dithiol-2-ones: An Alternative Route to Heteroleptic Dithiolene Complexes from Low-Valent Molybdenum and Tungsten Precursors
Elvers, Benedict J.,Schulzke, Carola,Fischer, Christian
, p. 2796 - 2805 (2019/05/29)
Mono-dithiolene complexes [Mo(CO)2(dt)(dppe)] and [W(CO)2(dt)(dppe)] {dt = cyclohex-1-ene-1,2-dithiol; 5,6-dihydro-2H-pyran-3,4-dithiol and dppe= 1,2-bis(diphenylphosphino)ethane} were synthesized by a photochemical procedure. The typical basic de-protection of the dithiolene ligand precursor was replaced by a light-induced opening of the 1,2-dithiole-2-one moiety. Advantages of this targeted approach comprise higher yields, cleaner transformations, and the possibility to continuously and precisely monitor the reaction progress. The light induced pericyclic reaction of the protection group releases carbon monoxide with formation of a 1,2-dithione, which is capable of oxidizing the electron rich metal precursor due to its non-innocence character. This procedure works well with molybdenum(0) and tungsten(0) precursors and particularly well with dithiolene ligands bearing aliphatic backbones, which are typically and notoriously difficult to handle when applying strictly chemical procedures.
Rapid synthesis of Group VI carbonyl complexes by coupling borohydride catalysis and microwave heating
Birdwhistell, Kurt R.,Schulz, Brian E.,Dizon, Paula M.
, p. 69 - 71 (2013/01/15)
Several Group VI tetracarbonyl phosphine and tertiary amine complexes [M(CO)4 L2, M = Cr, Mo, W, L2 = 2PPh 3, dppm, dppe, dppp, dppb, bpy, phen, dppf] were synthesized in minutes in the microwave at moderate temperature, atmospheric pressure, and utilizing NaBH4 as a catalyst. The reactions were optimized by careful solvent selection. The octahedral complexes were isolated in percent yields ranging from 17 to 95. The lower temperatures, shorter reaction times, benign solvents, and lower pressures as compared to the traditional thermal syntheses provide a rapid, eco-friendly synthetic route to these common Group VI complexes.
Branched Phospha[7]triangulanes
Slootweg, J. Chris,Schakel, Marius,De Kanter, Frans J. J.,Ehlers, Andreas W.,Kozhushkov, Sergei I.,De Meijere, Armin,Lutz, Martin,Spek, Anthony L.,Lammertsma, Koop
, p. 3050 - 3051 (2007/10/03)
A highly strained, thermally stable (up to 150 °C) branched phospha[7]triangulane was synthesized from the second-generation bicyclopropylidene and transient phosphinidene [Ph?P=W(CO)5], followed by demetalation in refluxing xylene. Bulkier transient CuCl?alkene-complexed phosphinidene gave 2-phosphabicyclo-[3.2.0]hept-1(5)-ene as an additional product. The "outer sphere" spirocyclopropanes provide a stabilizing factor for both of these novel compounds. Copyright
Microwave-assisted synthesis of group 6 (Cr, Mo, W) zerovalent organometallic carbonyl compounds
VanAtta, Sky L.,Duclos, Brian A.,Green, David B.
, p. 2397 - 2399 (2008/10/08)
The microwave-assisted synthesis of a series of compounds of the form ML(CO)4 (M = Cr, Mo, W; L = en, bipy, dppm, dppe), results in the reduction of reaction times and an increase in yields over previously published syntheses. Reaction times are reduced by a factor of 5 to over 500.
Ligand substitution kinetics in M(CO)4(η2:2-norbornadiene) complexes (M=Cr, Mo, W): Displacement of norbornadiene by bis(diphenylphosphino)alkanes
Tekkaya, Aysin,Oezkar, Saim
, p. 208 - 216 (2007/10/03)
The thermal substitution kinetics of norbornadiene (NBD) by bis(diphenylphosphino)alkanes (PP), (C6H5)2P(CH2)nP(C 6H5)2 (n=1, 2, 3) in M(CO)4(η2:2-NBD) complexes (M=Cr, Mo, W), were studied by quantitative FT-IR spectroscopy. The reaction rate exhibits first-order dependence on the concentration of the starting complex, and the observed rate constant depends on the concentration of the leaving NBD ligand and on the concentration and the nature of the entering PP ligand. In the proposed mechanism there are two competing initial steps: an associative reaction involving the attachment of the entering PP ligand to the transition metal center and a dissociative reaction involving the stepwise detachment of the diolefin ligand from the transition metal center. A rate law is derived from the proposed mechanism. The activation parameters are obtained from the evaluation of the kinetic data. It is found that at higher concentrations of the entering ligand, the associative path is dominant, while at lower concentrations the contribution of the dissociative path becomes significant. Both the observed rate constant and the activation parameters show noticeable variation with the chain length of the diphosphine ligand.
Syntheses, characterization and facial-meridional isomerism of tungsten tricarbonyl diphosphine complexes
Hsu, Sodio C. N.,Yeh, Wen-Yann
, p. 125 - 132 (2007/10/03)
The complexes fac-[W(CO)3(η2-dppf)(η1-dppm)] 4f, fac-[W(CO)3(η2-dppm)(η1-dppf)] 5f, fac-[W(CO)3(η2-dppf)-(η1-dppe)] 6f, fac-[W(CO)3(η2-dppe)(η1-dppf)] 7f, fac-[W(CO)3(η2-dppm)(η1-dppe)] 8f and fac-[W(CO)3(η2-dPpe)-(η1-dppm)] 9f have been prepared by treating fac-[W(CO)3(η2-diphos)(NCMe)] 1-3 [diphos = 1,1′-bis(diphenylphosphino)ferrocene (dppf), dppm (Ph2PCH2PPh2) or dppe (Ph2PCH2CH2PPh2)] with the corresponding diphosphines. The initially afforded facial isomers are converted into the meridional forms (4m-9m) in a subsequent, slow rearrangement process through opening of the chelated diphosphine ligand. A five-co-ordinate, square-pyramidal intermediate is presumed. In contrast, acid-assisted facial-meridional isomerization of 4f and 6f is likely via a seven-co-ordinate hydrido species. The new compounds have been characterized by elemental analyses and IR, mass and NMR spectroscopy.
Synthesis and characterization of novel neutral σ-alkynylcarbonylnitrosyl molybdenum(0) and tungsten(0) complexes. Crystal structure of [Mo(C≡CnPR)(CO) 2(dppe)(NO)] [dppe = 1,2-bis(diphenylphosphino) ethane]
Gamasa, M. Pilar,Gimeno, Jose,Zhang, Lei,Lanfranchi, Maurizio,Tiripicchio, Antonio
, p. 287 - 297 (2007/10/03)
σ-Alkynyl dicarbonyl complexes [M(C≡CR)(CO)2(dppe)(NO)] (M = Mo, R = H, tBu, nPr, iPr, Ph, CH2OCH3, SiMe3; M = W, R = H, tBu, nPr) have been prepared by reaction of mer-[M(CO)3(dppe)(NO)][BF4] with an equimolar amount of the acetylide salt M′C≡CR (M′ = Li, Na). The complexes [M(CO)2(NCMe)(dppe)(NO)] [BF4] (M = Mo, W) and [Mo(CO)(NCMe)2(dppe)(NO)][BF4] obtained by reaction of mer-[M(CO)3(dppe)(NO)][BF4] with acetonitrile are suitable precursors for the synthesis of the complexes [M(CO)2(dppe)(PR3)(NO)][BF4] (M = Mo, W, PR3 = PMe3, PMe2Ph) and [M(CO)(NCMe)(dppe)(PR3)(NO)][BF4] (PR3 = PMe2Ph, PPh3, P(OPh)3). The reaction of [Mo(CO)2(NCMe)(dppe)(NO)][BF4] with NaS(o--C6H4Me) yields the neutral complex [Mo{S(o-C6H4Me)}(CO)2(dppe)(NO)]. The crystal structure of [Mo(C≡CnPr)(CO)2(dppe)(NO)] has been determined by X-ray diffraction methods. The Mo atom displays a distorted octahedral coordination involving the N and C atoms of the nitrosyl and the alkynyl ligands in the apical positions and the P atoms from the dppe chelating ligand and two C atoms from terminal carbonyl groups in the equatorial positions.
