1,1‐Dialkoxy‐2‐azapropenylium Salze 1 können durch O‐Alkylierung am Carbonylkohlenstoff von N‐Methylencarbamidsäureestern 4 mit Trialkyloxonium‐Salzen 5 erhalten werden, falls eine N‐Alkylierung sterisch erschwert ist (4a); andernfalls werden die Iminium‐Salze 6 gebildet. Eine allgemeinere Darstellungsmethode für die Salze 1 beruht auf der Umsetzung von N‐(Alkoxymethyl)‐imidokohlensäureestern 8 mit Acylium‐Ionen (Acylspaltung). Die Salze 1 sind thermische nicht sehr beständig Phenylester‐Derivate gehen leicht in 4H‐1,3‐Benzoxazin‐Derivate 11 über. – Die Kristallstrukturanalyse von 1aa ergibt eine allenische Struktur mit orthogonalen π‐Systemen, wobei der C–N–C‐Bindungswinkel auf ca. 150° reduziert ist (sterische Effekte). – Quantenmechanische Ab‐initio‐Berechnungen sagen hohe sterische Flexibilität der Salze 1 voraus, wobei beim Grundkörper allenische Strukturen (16a) geringfügig (ca. 2–3 kcal/mol) gegenüber allylischen Formen (16d) bevorzugt sind. Thermodynamisch günstiger als die Salze 1 (bzw. 16) sind die isomeren Iminium‐Salze 6 bzw. 17. – Je nach Substitutionsmuster beobachtet man in Lösung (IR‐, dynamische NMR‐Spektroskopie) allenische (1a) oder allylische Strukturen (1b).
Suitably "push-pull"-substituted carbonyl ylides",'' or thiocarbonyl y l i d e~~~] have sufficient stability for isolation and have been the subject of several detailed investigations during the last ten years. Isolable selenocarbonyl ylides, on the other hand, were hitherto unknown.l4I We report here on the synthesis and characteristic properties of the first stable compounds of this type with cyclopropenylium and bis(methy1ene) or bis(imino)cyclopropanide functions as stabilizing termini.As we have found, the selone function in the diaminocyclopropeneselones 1, which are readily accessible from the cyclopropenylium salts 6 and sodium hydrogen selenide,15] is sufficiently nucleophilic to displace triethylamine from the zwitterions 216] or 3."] For the synthesis of 4a [yield 84%, m.p. 178°C (dec.)], one hours' heating in anhydrous dichloromethane until complete removal of triethylamine suffices; the synthesis of 5c (yield 85%, m.p. 230°C (dec.) was achieved by one hours' reaction in boiling ethanol. On cooling the reaction solution the desired selenocarbonyl ylides 4 and 5 precipitate as colorless to pale-beige, airstable crystals and can be recrystallized from nitromethane. 4c [m.p. 207°C (dec.)] could be obtained in 52% yield via another route. 2 was converted with freshly prepared sodium hydrogen selenide into the salt 7,"' which reacts smoothly with the salt 6cl9I to yield the selenocarbonyl ylide 4c.
An improved synthesis for [VCl2(N3S2)]∞, was found in the reaction of VOCl3 with (NSCl)3; when the reaction is performed in H2CCl2 and (NSCl)3 is used in excess, the thiazyl-solvate [VCl2(N3S2) · NSCl]2 is obtained. [VCl2(N3S2)] reacts with AsPh4Cl to form (AsPh4)2[VCl3(N 3S2)]2; this reacts with AgN3 in CH2Cl2 suspension to yield (AsPh4)2[V (N3)3(N3S2)]2 · CH2Cl2. The compounds were characterized by their IR and 51V NMR spectra. The latter are compared with new 51V NMR data for [VO2Cl2]⊖ and [VOCl4]⊖ ; a decrease of 51V shielding in the order [VO2Cl2]⊖ > [VOCl4]⊖ > [VX3(N3S2)]22⊖ (X - N3 > Cl) is found, which is interpreted in terms of increasing polarizability of the ligands and of ring contributions to the extreme deshielding observed with the thiazenovanadates.The crystal structure of (AsPh4)2[V(N3)3(N3S2)]2 · CH2Cl2 was determined from X-ray diffraction data (1496 observed reflexions, R = 0.058). It crystallizes in the triclinic space group P 1̄ with one formula unit per unit cell and with the lattice constants a - 1087, b = 1317, c = 1350 pm, α = 58.8, β = 85.9, γ = 68.0°. The structure consists of AsPh4⊕ ions, CH2Cl2 molecules and centrosymmetric [V(N3)3(N3S2)]22⊖ anions. In the latter. N3S2 ligands are bonded to the V atoms in a chelate manner with short V = N bonds (189 and 172 pm) forming planar VN3S2 rings. The dimerization is accomplished by V -N donor-acceptor interactions (224 pm) involving one N atom of each VN3S2 ring. The vanadium coordination number of 6 is com pleted by three azido groups with V -N bond distances of 200 to 204 pm.
HPPh3[WOCl4(OPPh3)] entsteht in Form dunkelgrüner Kristalle bei der partiellen Hydrolyse des Diphenylacetylenkomplexes [WCl4(PhCCPh)]2 bei Anwesenheit von Triphenylphosphan und Dichlormethan als Oxidations‐ und Lösungsmittel. Versuche, die Verbindung aus WOCl3, PPh3, OPPh3 und HCl in Dichlormethan direkt herzustellen, mißlangen.
HPPh3[WOCl4(OPPh3)] haben wir durch das IR‐ und das EPR‐Spektrum charakterisiert. Nach der röntgenographischen Strukturanalyse (1835 unabhängige, beobachtete, beobachtete Reflexe, R = 5,6%) kristallisiert die Verbindung monoklin in der Raumgruppe P21/n mit vier Formeleinheiten pro Elementarzelle. Sie ist aus HPPh3+‐Ionen und Anionen [WOCl4(OPPh3)]− aufgebaut, in denen das Wolframatom verzerrt oktaedrisch von vier äquatorial angeordneten Chloratomen und axial von einem terminalen O‐Atom (Bindungsabstand WO = 172 pm) und von dem O‐Atom des OPPh3‐Moleküls (WO = 206 pm) umgeben ist.
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