Decarbonylation of a cyclic bis-phosphaethynolatostannylene (ADC)Sn(PCO)2 based on an anionic dicarbene framework (ADC = PhC{N(Dipp)C}2 ; Dipp = 2,6-iPr2 C6 H3 ) under UV light results in the ...formation of a Sn2 P2 cluster compound (ADC)SnP2 as a green crystalline solid. The electronic structure of (ADC)SnP2 is analyzed by quantum-chemical calculations. At room temperature, (ADC)SnP2 reversibly binds with CO2 and forms (ADC)2 {SnOC(O)P}SnP. (ADC)SnP2 enables catalytic hydroboration of CO2 and reacts with elemental selenium and Fe2 (CO)9 to afford (ADC)2 {Sn(Se)P2 }SnSe and (ADC)Sn{Fe(CO)4 }P2 , respectively. All compounds are characterized by multinuclear NMR spectroscopy and their solid-state molecular structures are determined by single-crystal X-ray diffraction.
Reaction of the carbyne complexes Tp‘(CO)2M⋮C−PC(NR2)2 (1, 2) Tp‘ = HB(3,5-Me2C3HN2)3; M = Mo (1, 3); W (2, 4); R = Me (a); Et (b) with methyl trifluoromethanesulfonate afforded the orange-red salts ...Tp‘(CO)2M⋮C−P(Me)C(NR2)2SO3CF3 (3, 4), the cations of which can be considered as methylphosphines featuring additional bisaminocarbenium- and metallaalkynyl substituents. Analogously, complex Tp‘(CO)2W⋮C−PC(NEt2)2 (2b) was protonated with ethereal HBF4 in ether at the phosphorus atom to give Tp‘W⋮C−P(H)−C(NEt2)2BF4 (5), which in CH2Cl2 solution experienced a clean rearrangement to the metallaphosphirene (6). Treatment of 2b with F3CSO3H led directly to (6‘). The molecular structures of 4b and 6‘ were established by X-ray structure analysis.
Abstract
C
15
H
16
Cl
2
N
4
O
2
, monoclinic,
P
2
1
/
c
(no. 14),
a
= 26.2014(7) Å,
b
= 7.59320(10) Å,
c
= 17.9766(4) Å,
β
= 109.217(3)°,
V
= 3377.20(14) Å
3
,
Z
= 8,
R
gt
(
F
) = 0.0503,
wR
...ref
(
F
2
) = 0.1411, T = 100.0(1) K.
The Front Cover shows the solid‐state structure of a syn‐biconcave tribenzotriquinacene dimer synthesized by chirality‐controlled two‐fold crosswise Ullmann‐type condensation of an enantiomerically ...pure TBTQ‐based ortho‐iodophenol with (M)‐configuration (X = I, Y = OH). Such highly bowl‐shaped building blocks with single‐wing functionalization at the aromatic periphery were obtained on a gram‐scale via enantioselective enzyme‐catalyzed ester hydrolysis in the key step. More information can be found in the Full Paper by H. Gröger, D. Kuck et al.
Ein zweizähniges Pniktogenbrücken‐Wirtsystem auf der Basis von 1,8‐Diethinylanthracen wurde mittels einer selektiven Zinn‐Antimon‐Austauschreaktion hergestellt und auf seine Fähigkeit untersucht, als ...Lewis‐saure Wirtskomponente für die Komplexierung von Lewis‐basischen oder anionischen Gästen zu fungieren. In dieser Arbeit wurde mit der C≡C−Sb(C2F5)2‐Gruppe eine neuartige Akzeptorfunktion etabliert, mit der das Potenzial von Antimon(III)‐Funktionen als Vertreter der kaum erforschten Pniktogenbrücken‐Donatoren untersucht werden kann. Die Akzeptorfähigkeit dieses teilfluorierten Wirtsystems wurde gegenüber Halogenidanionen (Cl−, Br−, I−), Dimethylchalkogeniden Me2Y (Y = O, S, Se, Te) und Stickstoffheterozyklen (Pyridin, Pyrimidin) untersucht. Einblicke in das Adduktbildungsverhalten sowie die Bindungssituation solcher E⋅⋅⋅Sb−CF‐Einheiten wurden in Lösung mittels NMR‐Spektroskopie, im festen Zustand durch Röntgenbeugung, durch Elementaranalysen sowie durch rechnerische Methoden (DFT, QTAIM, IQA) gewonnen.
Ein zweizähniges Pniktogenbrücken‐Wirtsystem wurde auf der Grundlage von Sb(C2F5)2‐Funktionen konstruiert und seine Wirt‐Gast‐Chemie gegenüber einer Vielzahl von Substraten getestet, darunter Me2O und seine höheren Homologen, Halogenidionen und N‐heterozyklische Basen. Das neue Wirtsystem zeigt eine Kooperativität der beiden C≡C−Sb(C2F5)2‐Funktionen bei der Adduktbildung. Die Komplexe wurden sowohl experimentell (XRD, NMR) als auch mit Berechnungen (DFT, QTAIM, IQA) analysiert.
Triterpenes from Maesopsis eminii Fokou, P.A; Stammler, H.G; Neumann, B ...
Journal of natural products (Washington, D.C.),
12/2004, Letnik:
67, Številka:
12
Journal Article
Recenzirano
Two pentacyclic triterpenes, 1alpha,3beta-dihydroxybauer-7-en-28-oic acid (1) and 3beta-hydroxybauer-7-en-28-oic acid (2), together with sitosterol-3-beta-O-d-glucopyranoside and stigmasterol have ...been isolated from the bark of the plant Maesopsis eminii. Their structures have been elucidated by spectroscopic methods. One of the triterpenes (1) is new, and its structure was confirmed by X-ray crystallographic analysis. This new triterpene displayed moderate antibacterial activity against Bacillus subtilis ATCC 6633.
In the reaction of the nucleophilic decamethylsilicocene, ((Me5C5)2Si (1), with the electrophilic heterocumulenes CO2, COS, CS2, and RNCS, multistep processes are observed, which in most cases ...proceed via several highly reactive intermediates. In all reactions, the formal oxidation state of the silicon atom changes from +2 in 1 to +4, and the hapticity of the pentamethylcyclopentadienyl ligands changes from η5 to η1. In the reaction of 1 with CO2, COS, or RNCS, double-bond species of the type (Me5C5)2SiX (X = O, S) are formed, which are stabilized via different routes. Thus, reaction of 1 with CO2 in toluene as solvent finally leads to the spiro compound (Me5C5)2SiO22C (4), whereas in pyridine as solvent, the eight-membered heterocycle (Me5C5)2SiO2CO2 (5) is formed. The dithiadisiletane (Me5C5)2SiS2 (9) results from the reaction of 1 with COS. Dithiasiletane derivates of the type (Me5C5)2SiS2CNR (10, 11) are the final products from the reaction of 1 with RNCS (R = CH3, C6H5). Multistep rearrangement processes have to be postulated to explain the formation of the dithiadisiletane derivate 15 in the surprising reaction of 1 with CS2; ligands that initially are bonded to the silicon (Me5C5) and to the carbon atom (S) have to be completely exchanged to build up the final product. The silaheterocycles 4, 5, 10, and 15 and also some of the basic molecular framework have been unknown in the literature. The crystal strucutres of 4, 5, 10, and 15 were determined by X-ray crystallography and are presented.
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