- Photochemical reaction of W(CO)6 with SnCl4. III. Synthesis of some novel seven-coordinate tungsten(II) complexes (LN- and P-donor ligands)
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The photochemical reaction of W(CO)6 with SnCl4 gives the oxidation addition product (1).Compound 1 reacts with ligands LCH3CN, bipy, PPh3 or dppe to give the seven-coordinated species and .These W(II) compounds can be prepared in a one-pot two-step manner, without isolating the intermediate (1).Keywords: Tungsten; Tin; Carbonyls; Seven-coordinate
- Szymanska-Buzar, Teresa
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- An update on WII and MoII carbonyl precursors and their application in the synthesis of potentially bio-inspired thiophenolate-oxazoline complexes
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The synthesis of two new low-valent dicarbonyl complexes of tungsten [W(CO)2(SPh-oz)2] (3b) and molybdenum [Mo(CO) 2(SPh-oz)2] (4b) coordinated by a bidentate thiolate-oxazoline ligand SPh-oz is reported. The thereby created coordination via two anionic sulfur atoms can be seen as biologically inspired as it reflects the first coordination sphere of the pterin cofactor found in molybdenum and tungsten enzymes. The in-situ preparation of the lithium salt Li(SPh-oz) (1) was described previously in literature, but analytical data was not available. A similar situation was found for the published syntheses of the low-valent metal precursors [W(CO)3(PPh3)2Cl2] (2a), [W2(CO)7Br4] (3a) and [Mo(CO) 4Br2] where experimental procedures were unreliable and experimental data was inadequate or missing.To the best of our knowledge this is the first report of a full characterization of the literature known compounds Li(SPh-oz) (1), [W(CO)3(PPh3)2Cl2] (2a) and [W2(CO)7Br4] (3a). Furthermore the novel tetranuclear Mo-precursor [Mo4(CO)7Br10] (4a) was synthesized. The symmetric and asymmetric IR stretching frequencies of its seven carbonyl ligands were calculated using DFT and related to the experimental values. The molecular structures of the novel precursor compounds [W(CO)2(PPh3)2Cl2] (2a'), [PPh 3Cl]2[WCl6] (2b), [Mo4(CO) 7Br10] (4a), the two complexes with the SPh-oz ligand [W(CO)2(SPh-oz)2] (3b), [Mo(CO)2(SPh-oz) 2] (4b) and a new modification of [W2(CO) 7Br4] (3a) were determined by single-crystal X-ray diffraction analysis. Copyright
- Peschel, Lydia M.,Schachner, Joerg A.,Sala, Chris H.,Belaj, Ferdinand,Moesch-Zanetti, Nadia C.
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p. 1559 - 1567
(2013/08/23)
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- The oxidative addition of SnCl4 to [W(CO)4(NCMe)(PPh3)]. The X-ray crystal structure of [WH(CO)3(NCMe)(PPh3)2]- [SnCl5·MeOH]
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The oxidative addition reaction of SnCl4 with [W(CO)4(NCMe)(PPh3)] in acetonitrile gives a mixture of seven-]coordinate tungsten(II) compounds: [WCl(SnCl3)(CO)3(NCMe)(PPh3)] (1), [WCl2(CO)3(NCMe)(PPh3)] (2), [WCl(SnCl3)(CO)2(NC-Me)2(PPh3)] (3), and [WCl2(CO)2(NCMe)2(PPh3)] (4) identified by IR and NMR (1H, 13C{1H}, and 31P{1H}) studies. Treatment of [W(CO)4(NCMe)(PPh3)] with 1 equiv. of SnCl4 in CH2Cl2 solution besides compounds 1 and 2 also gives ionic species such as [HPPh3]+ and [SnCl6]2- and cationic tungsten(II) complexes. The crystal structure of one of these, [WH(CO)3(NCMe)(PPh3)2][SnCl5 ·MeOH] (5), has been established by single-crystal X-ray diffraction. The IR, 1H, 13C{1H} and 31P{1H} spectra of 5 are also described and can be correlated with the crystallographically observed geometry. A notable feature of 5 is the presence of an agostic interaction of the hydride ligand with one of the carbonyl ligands.
- Szymańska-Buzar, Teresa,G?owiak, Tadeusz,Czelu?niak, Izabela
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p. 1817 - 1823
(2008/10/08)
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- Synthesis, structure and reactivity of novel W-Ge chlorocarbonyl compounds. X-raycrystal structure of [WCl(GeCl3)(CO)3(NCEt)2]
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The reaction of GeCl4 with tungsten(0) compounds yielded heterobimetallic W-Ge complexes. The novel dinuclear complex [(CO)4W(μ-Cl)3W(GeCl3)(CO)3] 1 was obtained together with [W(CO)5(GeCl2)] 2 in a photochemical reaction of W(CO)6 with GeCl4. The mononuclear seven-coordinate complex [WCl(GeCl3)(CO)3(NCMe)2] 3 was formed in a reaction of complex 1 with acetonitrile or in a reaction of [W(CO)4(NCMe)2] with GeCl4 in dichloromethane. A single-crystal X-ray diffraction study of the complex [WCl(GeCl3)(CO)3(NCEt)2] 4 showed that the environment of the tungsten atom is a distorted capped octahedron with the GeCl3 anionic ligand occupying the unique capping position above an octahedral face defined by the three carbonyl groups. The position of the GeCl3 ligand is approximately trans to the W-Cl bond. The dinuclear complex 1 and the mononuclear complex 3 show similar behavior in reaction with alkynes. Complexes were isolated in which CO or/and acetonitrile ligands were replaced by alkyne ligands. The alkyne tungsten(II) complexes 7-13 formed were structurally characterized by IR and NMR spectroscopy. However, the reaction of 1 and 3 with phenylacetylene (PA) leads to polymerization and formation of a high molecular weight polyphenylacetylene (PPA). The structures and mechanisms of the formation of various new types of complexes and their role in the catalytic process are discussed.
- Szymanska-Buzar, Teresa,GlLowiak, Tadeusz
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p. 143 - 153
(2007/10/03)
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- Tungsten(II) chlorocarbonyls as alkene metathesis, arene alkylation and alkyne polymerization catalysts
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Tungsten(II) chlorocarbonyl compound obtained by photochemical oxidation of W(CO)6 with CCl4 is an active alkene metathesis catalyst, free of any organometallic component. This indicates that the initially formed alkylidene ligand must come from the alkene. In toluene solution the same tungsten(II) compound also acts as a highly active catalyst for the transformation of alkenes to alkyltoluenes. Tungsten(II) compounds, which are formed in photochemical oxidation of W(CO)6 with Group 14 tetrahalides, are extremely reactive at 25°C in phenylacetylene polymerization. The results reported here clearly demonstrate that the formation of tungsten(II) might be an important event in the creation by Lewis acids (Group 14 tetrachlorides) of the catalytic activity of tungsten(0) compounds.
- Szymanska-Buzar, Teresa
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p. 113 - 122
(2008/10/09)
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- New Gold Carbene Complexes via Carbene Transfer Reactions
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Tungsten aryl- and alkylcarbene complexes on reaction with HAuCl4 give good yields of the corresponding gold carbene complexes (2a - e, 4).The reaction involves a redox process for which a mechanism is dicussed.The transfer of the carbene ligand proceeds by retention of its configuration.
- Aumann, Rudolf,Fischer, Ernst Otto
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p. 1853 - 1857
(2007/10/02)
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