Synthesis and structure of lithium tris(trimethylsilyl)-silanide · 1,5 DME

Das aus Tetrakis(trimethylsilyl)silan 1 [6] und Lithiummethyl in 1,2-Dimethoxyethan1) zugängliche Lithium-tris(trimethylsilyl)silanid' 1,5 DME 2a kristallisiert monoklin in der Raumgruppe P21/c mit folgenden, bei einer Meßtemperatur von -120 ± 2°C bestimmten Parametern der Elementarzelle: a = 1072,9(3); b = 1408,3(4); c = 1775,1(5) pm; ß = 107,74(2)°; 4 Formeleinheiten (Z = 2). Nach den Ergebnissen der Röntgenstrukturanalyse (Rw = 0,040) baut sich die Verbindung aus zwei [Lithium-tris(trimethylsilyl}silanid]-Einheiten auf, die über ein DME-Molekül verbunden und deren vierfach koordinierte Lithiumatome von je einem weiteren DME-Liganden chelatartig umgeben sind. Mit 263 pm ist der Li-Si-Abstand wesentlich länger als die Summe der kovalenten Radien; weitere charakteristische mittlere Bindungslängen und -winkel sind: Si-Si 234, Li-O 200, O-C 144, OċO (Biß) 264 pm; Si-Si-Si 104°, Li-Si-Si 107° bis 126°, O-Li-O (im Chelatring) 83°. Das aus Di(tert-butyl)dichlorsilan 15, Chlortrimethylsilan und Lithium dargestellte Di(tert-butyl)bis(trimethylsilyl)silan 17 konnte bisher nicht in das analoge Silanid überführt werden.Lithium tris(trimethylsilyl)silanide · 1,5 DME 2a synthesized from tetrakis(trimethylsilyl)silane 1 [6] and methyllithium in 1,2-dimethoxyethane†, crystallizes in the monoclinic space group P21/c with following dimensions of the unit cell determined at a temperature of measurement of −120 ± 2°C: a = 1 072.9(3); b = 1 408.3(4); c = 1 775.1(5) pm; β = 107.74(2)°; 4 formula units (Z = 2). An X-ray structure determination (Rw = 0.040) shows the compound to be built up from two [lithium tris(trimethylsilyl)silanide] moieties which are connected via a bridging DME molecule. Two remaining sites of each four-coordinate lithium atom are occupied by a chelating DME ligand. The Li-Si distance of 263 pm is considerably longer than the sum of covalent radii; further characteristic mean bond lengths and angles are: Si-Si 234, Li-O 200, O-C 144, OċO (biß) 264 pm; Si-Si-Si 104°, Li-Si-Si 107° to 126°; O-Li-O (inside the chelate ring) 83°. Unfortunately, di(tert-butyl)bis(trimethylsilyl)silane 17 prepared from di(tert-butyl)dichlorsilane 15, chlorotrimethylsilane and lithium, does not react with alkyllithium compounds to give the analogous silanide

From 1,3-Diphosphacyclobutadiene to 1,3,5-triphosphabenzene

Alkyl- and aryldiaminodifluorophosphoranes 1 can easily be obtained by fluorination of alkyl- and aryldiaminophosphanes with sulfur tetrafluoride, SF4 1. Peralkylated alkyldiaminodifluorophosphoranes react with one mole of n-butyllithium to form P-fluoro-ylides, a class of compounds which had not been described previously. Methylbis(dimethylamino)difluorophosphorane 2, e.g., reacts with butyllithium to give methylenebis(dimethylamino)fluorophosphorane 3, a colorless liquid, b.p. 42 °C (10 Torr)2: For P-chloro-ylides such as (t-C4H9)2PCI=CHSi(CH3)3, the chloro ligand is substituted by the alkyl group upon reaction with methyl-or n-butyllithium3,4; however, P-fluoro-ylides behave in a different way. If 2 is reacted with two moles of butyllithium, the main product is the crystalline, colorless 1,1,3,3-tetrakis(dimethylamino)-1δ 5, 3δ 5-diphosphete or 1,1,3,3-tetrakis(dimethylamino)-δ 5, 3δ 5-diphosphacyclobutadiene 4 (chemical shift σ(P) = 48.9 ppm)5

Intermolecular Sb···Sb interactions in crystalline tetramethyldistibane (Element element bonds ; 3)

Tetramethyldistibane which shows a colour change from deep red to pale yellow upon melting, has been subjected to single-crystal x-ray diffraction analyses at -21° and -139°C (orthorhombic, Pnma, Z = 4, -139°C: a = 1150.9(3); b = 1136.8(2); c = 651.6(2) pm). The molecules adopt the antiperiplanar conformation with the crystallographically imposed symmetry m (c 3) and are aligned in extended linear antimony chains with short intermolecular contacts (-139 °C: Sb-Sb 283.8(1), Sb···Sb 367.8(1) pm; Sb-Sb...Sb 179.2°). The structure is compared with those of similar compounds

Molecular and crystal structure of tetramethyldiphosphane and -diarsane (Element element bonds ; 4)

The molecular and crystal structures of the isotypic compounds tetramethyldiphosphane 1 and -diarsane 2 have been determined by single crystal X-ray diffraction (monoclinic; C2/m; Z = 2; 1/2: -155/-144 ·C°; a = 540.6(2)/555.8(2); b = 1131.0(6)/1136.7(6); c = 602.5(2)/612.8(2) pm;β = 97.31(3)/95.24(3)"; P-P 221.2(1)/As-As242.9(1) pm). In accordance with the crystallographically imposed symmetry 2/m, the molecules adopt antiperiplanar conformation. Their crystal structures are c10sely related to those of the homologues tetramethyldistibane 3 [1] and -dibismuthane 4 [3]. As found for the latter compounds, the E-E units (E = P, As) are also aligned in linear chains, but the intermolecular E···E contacts (P...P 381/As...As 370 pm) do not allow any extended interaction between molecules, which otherwise would result in thermochromic effects

Synthesis and structure of 1,3-dibenzyl- and 1,3-diethyl-2,4-bis(phenylimino)-1,3-diphosphetane (Acyl- and alkylidenephosphines ; 28)

Unter der Katalyse von wenig festem Natriumhydroxid setzen sich die aus Benzyl- oder Ethylbis(trimethylsilyl)phosphan und Phenylisocyanat gebildeten Addukte 1a und 1b bei +20°C langsam zu Hexamethyldisiloxan und oligomeren [(Phenylimino)methyliden]phosphanen um. Während die Benzyl-Verbindung in unterschiedlichen Lösungsmitteln nur als Gemisch aus [N,N′-(E)]- und [N,N′-(Z)]-isomerem 2,4-Bis(phenylimino)-1,3-diphosphetan 2a mit den beiden Alkylgruppen an den Phosphoratomen in trans-Stellung vorliegt, findet man bei dem in Cyclopentan gelösten Ethyl-Derivat 2b ein weiteres [N,N′-(E)/(Z)]-isomeres Dimerenpaar mit zueinander cisständigen Substituenten sowie die beiden trimeren Formen 3b und 4b. Die aus 1,2-Dimethoxyethan oder Cyclopentan isolierten Verbindungen [N,N′-(E)]-1r,3t-Dibenzyl- (2a) und [N,N′-(E)]-1r,3t-Diethyl-2,4-bis(phenylimino)-1,3-diphosphetan 2b kristallisieren monoklin in der Raumgruppe P21/c bzw. P21/n mit folgenden, bei Meßtemperaturen von +20 ± 3°C/−130 ± 3°C bestimmten Abmessungen der Elementarzelle: a = 2145,4(1)/569,3(1); b = 568,1(2)/719,1(2); c = 1960,2(2)/2042,6(4) pm; β 99,43(1)°/95,03(2)°; Z = (2+2) bzw. 2. Nach den Ergebnissen von Röntgenstrukturanalysen (RW = 0,034/0,041) weisen die Moleküle Inversionszentren auf. Charakteristische gemittelte Bindungslängen (pm) und -winkel (°) sind: endocycl. P-C 185/184; C-P-C 82/81; P-C-P 98/99; exocycl. P-C 186/184; C=N 127/127; C=N-C 121/11.Catalyzed by small amounts of solid sodium hydroxide, the adducts 1a and 1b formed from benzyl- or ethylbis(trimethylsilyl)phosphine and phenylisocyanate, react at +20°C slowly to give hexamethldisiloxane and oligomeric [(phenylimino)methylidene]phosphines. In different solvents the benzyl compound was found to exist only as a mixture of [N,N′-(E)/(Z)]-isomeric 2,4-bis-(phenylimino)-1,3-diphosphetanes 2a with their alkyl groups at the phosphorus atoms in trans position, whereas in case of the ethyl derivative 2b a second pair of [N,N′-(E)/(Z)]-isomeric dimers with their substituents in cis position and two trimeric forms (3b and 4b) could be detected in cyclopentane. [N,N′-(E)]-1r,3t-dibenzyl- (2a) and [N,N′-(E)]-1r,3t-diethyl-2,4-bis(phenylimino)-1,3-diphosphetane 2b isolated from 1,2-dimethoxyethane or cyclopentane, crystallize in the monoclinic space group P21/c or P21/n, resp., with following dimensions of the unit cell determined at temperatures of measurement of +20 ± 3°C/−130 ± 3°C: a = 2145.4(1)/569.3(1); b = 568.1(2)/719.1(2); c = 1960.2(2)/2042.6(4) pm; β 99.43(1)°/95.03(2)°; Z = (2+2) and 2, resp. X-ray structure determinations (Rw = 0.034/0.041) show both molecules to be centrosymmetric. Characteristic rounded bond lengths (pm) and angles (°) are: endocyclic P-C 185/184; C-P-C 82/81; P-C-P 98/99; exocyclic P-C 186/184; C=N l27/127; C=N-C 121/11

A 1λ5,3λ5,5λ3-triphosphabenzene derivative

The first ring compound containing the (P=C)3 skeleton, the title compound 3, was prepared as shown below. 13C-NMR data indicate a highly ylidic character of the C4-P5-C6 grouping