Synthesis, reactivity, and x-ray structure of fac-(acetonitrile)tricarbonyl[bis(diphenylphosphino)methane]tungsten. Stereoselective preparation of fac-W(CO)3(13CO)(dppm) and subsequent intramolecular rearrangement processes

1987 ◽  
Vol 26 (22) ◽  
pp. 3727-3732 ◽  
Author(s):  
Donald J. Darensbourg ◽  
David J. Zalewski ◽  
Christine Plepys ◽  
Charles Campana
Keyword(s):  
Intramolecular Rearrangement ◽  
X Ray ◽  
Rearrangement Processes

Silaheterocyclen, XX Aminosubstituierte Vinylchlorsilane und Silaethene: Bausteine zur Synthese von 1,3-Diaza-2-silacyclopentanen / Silaheterocycles, XX Aminosubstituted Vinylchlorosilanes and Silenes: Building Blocks for the Synthesis of 1,3-Diaza-2-silacyclopentanes

1992 ◽  
Vol 47 (10) ◽  
pp. 1377-1385 ◽  
Author(s):  
Norbert Auner ◽  
Erika Penzenstadler ◽  
Eberhardt Herdtweck
Keyword(s):  
Reaction Pathway ◽  
Addition Product ◽  
Building Blocks ◽  
Diels Alder ◽  
Main Reaction ◽  
Intramolecular Rearrangement ◽  
X Ray Diffraction ◽  
Great Tendency ◽  
X Ray ◽  
Frame Work

The amino-substituted vinylchlorosilanes 4-7 are synthesized from N,N,N′-trimethylethylenediamine (8a) or tris(trimethylsilyl)ethylenediamine (8b), Li Bun and organodichlorovinylsilanes. 5 eliminates trimethylchlorosilane when distilled and yields 1,3-diaza-2-silacyclopentane 9, whereas the compounds 6 and 7 show a great tendency to oligomerize. The reaction of 4 with LiBut gives a neopentylsilene intermediate 10 a which can be trapped by isoprene or 1,3-butadiene yielding small amounts of the Diels-Alder products 11 and 12, respectively. The main reaction pathway for 10 a is rearrangement with migration of a Me3Sigroup from nitrogen to the silene’s carbon atom and a new N—Si bond formation to give the diazasilacyclopentane 10 which has been characterized by X-ray diffraction analysis. This intramolecular rearrangement appears to involve a pentacoordinated silene Si-atom. No dimerisation of 10a to a disilacyclobutane is observed. The introduction of a second Si-tris(trimethylsilyl)ethylenediamine substituent at the SiC frame work does not result in silene stabilisation: there is no evidence for Si-hexacoordination in silene 15 nor in the [4+2] cyclo-addition product with isoprene (14).

scholarly journals (2,3-Bis(methylen)bicycIo[2.2.2]octan)zirconocen: Synthese, Struktur und elektrochemische Reduktion/(2,3-Bis(methylene)bicyclo[2.2.2]octane)zirconocene: Synthesis, Structure, and Electrochemical Reduction

1985 ◽  
Vol 40 (2) ◽  
pp. 150-157 ◽  
Author(s):  
Gerhard Erker ◽  
Klaus Engel ◽  
Carl Krüger ◽  
Yi-Hung Tsay ◽  
Edmond Samuel ◽  
...  
Keyword(s):  
Electrochemical Reduction ◽  
Structure Determination ◽  
Radical Anion ◽  
Nmr Spectra ◽  
Activation Barrier ◽  
Intramolecular Rearrangement ◽  
Dynamic Nmr ◽  
Space Group ◽  
X Ray

Photolysis of diphenylzirconocene and 2,3-bis(methylene)bicyclo[2.2.2]octane in toluene at -25 °C yields biphenyl and (2,3-bis(methylene)bicyclo[2.2.2]octane)zirconocene (lg) (67.5% isolated yield).1g exhibits dynamic NMR spectra indicating rapid alternation of diene faces coordinated to zirconium (ring-flip mechanism). This degenerate intramolecular rearrangement is characterized by an extremely low activation barrier (⊿G≠-131°C = 7.1 ± 0.3 kcal/mol). 1g crystallizes in space group P1̄with a = 7.215(1) Å, b = 9.654(1) Å, c = 11.831(1) Å, α = 94.97(1)°, β = 91.81(1)°, and γ = 103.22(1)°. The X-ray structure determination reveals a pronounced metal alkyl character of the (diene)ZrCp2 moiety. Accordingly, 1g is easily reduced electrochemically to give a Zr(III) radical anion (7) observed by esr (g = 1.990; a(H) = 2.976 G; a(Zr) = 18.36 G).

The synthesis and characterization of 3,3-disubstituted pent-4-enals and their 2,2-(trimethylenedithio)pent-4-enal precursors, including the X-ray crystal structure of (R)-3-ethyl-3-phenyl-2,2-(trimethylenedithio)pent-4-enal

1985 ◽  
Vol 63 (5) ◽  
pp. 1035-1040 ◽  
Author(s):  
Charles G. Young ◽  
Brian R. James ◽  
Steven J. Rettig
Keyword(s):  
Molecular Structure ◽  
Crystal Structure ◽  
Crystal And Molecular Structure ◽  
Synthesis And Characterization ◽  
Intramolecular Rearrangement ◽  
X Ray ◽  
X Ray Crystallography ◽  
New Compounds ◽  
Allylic Bromide

A variety of 3,3-disubstituted pent-4-enals (5a, R = Me, R′ = Et; 5b, R = Me, R′ = Ph; 5c, R = Et, R′ = Ph) has been prepared by the Raney nickel desulfurization of the corresponding 3,3-disubstituted 2,2-(trimethylenedithio)pent-4-enal precursors 4a–4c. The precursor compounds were prepared by the alkylation of 2-formyl-1,3-dithiane with the appropriate 3,3-disubstituted allylic bromide. The new compounds have been characterized by elemental analysis, infrared and nmr spectroscopy, and mass spectrometry. The crystal and molecular structure of (R)-4c has also been determined by X-ray crystallography. At temperatures of ca. 130 °C, compounds 4a–4c undergo intramolecular rearrangement to form the tri-substituted alkenes 6a–6c, which have also been characterized by the present study.

Synthesis, spectroscopy, and structures of the seven-coordinate complexes (CH3)2AsC(CF3)== C(CF3)As(CH3)2W(CO)2I2P(OC6H5)3 and [(CH3)2AsC(CF3)== C(CF3)As(CH3)2]2W(CO)Br2 and spectroscopy of related seven-coordinate complexes

1998 ◽  
Vol 76 (3) ◽  
pp. 245-253
Author(s):  
Richard J Barton ◽  
Sushil K Manocha ◽  
Beverly E Robertson ◽  
Lynn M Mihichuk
Keyword(s):  
Chemical Shifts ◽  
Spectroscopic Properties ◽  
Intramolecular Rearrangement ◽  
X Ray Diffraction ◽  
Tungsten Atom ◽  
X Ray ◽  
Nmr Data ◽  
Octahedral Environment ◽  
Rearrangement Process ◽  
Coordinate Geometry

(L-L)W(CO)3I2 (L-L = (CH3)2AsC(CF3)== C(CF3)As(CH3)2) reacts with the monodentate phosphite P(OC6H5)3 and (L-L)W(CO)3Br2 reacts with L-L to form new seven-coordinate complexes (L-L)W(CO)2I2P(OC6H5)3 and (L-L)2W(CO)Br2. Low-temperature X-ray diffraction analyses show the tungsten atom to be seven coordinate in both complexes, with the geometry most closely approximated by a monocapped octahedral environment, the capping group being a carbonyl in the dicarbonyl complex; the geometry is most closely approximated by a pentagonal bipyramidal environment in the monocarbonyl complex. The 1H, 13C, and 19F NMR data indicate that the dicarbonyl complex is stereochemically nonrigid at 298 K and rigid at lower temperatures, while the monocarbonyl is nonrigid both at 298 K and at lower temperatures. ΔG not equal values calculated at coalescence temperatures are consistent with an intramolecular rearrangement process for both complexes. The 13C chemical shifts and 2J(13C-31P) values provide important structural considerations in the assignment of a seven-coordinate geometry. Spectroscopic properties for the related seven-coordinate dicarbonyl complexes (L-L)W(CO)2PX2 (P = P(OC6H5)3; X = Br; P = P(OCH3)3, P(C6H5)3; X = Br, I) and monocarbonyl complexes (L-L)2W(CO)I2 and (L-L)W(CO)X2[P(OCH3)3]2 (X = Br, I) are presented and compared to those of the two title complexes.Key words: seven-coordination, X-ray, NMR analysis.

Structural studies on dioxan-2-ylium ions; intramolecular attack of an oxygen atom on a carbenium ion centre

1994 ◽  
Vol 72 (10) ◽  
pp. 2084-2093 ◽  
Author(s):  
Ronald F. Childs ◽  
Guogong J. Kang ◽  
Teresa A. Wark ◽  
Christopher S. Frampton
Keyword(s):  
Carbon Chain ◽  
Intramolecular Rearrangement ◽  
Carbon Chain Length ◽  
Monoclinic Crystal ◽  
Space Group ◽  
X Ray ◽  
X Ray Crystallography ◽  
Ether Oxygen ◽  
Carbenium Ion ◽  
C Nmr

As models for the ionization of orthoesters, a series of 1,3-dioxan-2-ylium salts have been prepared and characterized. The properties of 1,3-dioxan-2-ylium hexachloroantimonate 1, 5-ethoxymethyl-1,3-dioxan-2-ylium hexachloroantimonate 2, 2-methyl-5-ethoxymethyl-1,3-dioxan-2-ylium hexachloroantimonate 3, and 2-phenyl-5-ethoxymethyl-1,3-dioxan-2-ylium hexachloroantimonate 4, have been studied by 1H and 13C NMR spectroscopy. The structures of 3 and 4 have been determined using X-ray crystallography. Salts 3 and 4 both crystallize in monoclinic crystal systems. For 3, the space group is C2/c, with a = 30.192(4) Å, b = 9.613(2) Å, c = 12.742(2) Å, β = 109.71(1)°, V = 3482(1) Å3, and Z = 8. Complex 4 crystallizes in the space group P21/n, with a = 10.638(2) Å, b = 11.849(2) Å, c = 16.970(3) Å, β = 106.84(1)°, V = 2047(1) Å3, and Z = 4. The geometries of 3 and 4 are similar with the ether oxygen disposed over the dioxan-2-ylium ring. However, the interaction between the ether oxygen and the cationic centre is not significant due to the large internuclear distance observed. The cation 5, in which the carbon chain length between the ether oxygen and C(5) was increased, was prepared. This ion was found to undergo a reversible, intramolecular rearrangement resulting in the formation of 1-methyl-4-acetoxymethyl-tetrahydrofuranyl oxonium hexachloroantimonate 11.

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