Browsing by Author "Pauer, Frank"

The lithium derivative of tert-butyl(di-tert-butylfluorosilyl)-amine (1) reacts with sulfur or selenium to give the bis[(fluorosilyl)-amino]di- and -trisulfanes 2, 3 and -selane 4, respectively. The trisulfane 3 crystallizes from n-hexane and exhibits a helical structure (X-ray analysis).

A series of compounds has been prepared in which the NH proton of the sulfiniminamines Me3SiN=S(R)---NHR′ (R = Ph (mainly) or tBu, R′ = tBu or SiMe3) is replaced by Li, Na, K, Rb, or Cs. The compounds form a series of reagents of increasing reactivity which could be used, for example, to introduce chelating ligands into transition metal complexes. The structures of the compounds have been determined by X-ray diffraction. When there is a phenyl substituent on the sulfur atom, the metal derivatives are isomorphic dimers, involving three fused four-membered rings in a step-shaped structure. The higher the atomic number of the metal, the stronger is the η-coordination of the phenyl group to the metal. With a t-butyl group on the sulfur atom the structures of the lithium derivatives [(Me3SiN=S(tBu)---NR′)Li]2 are different for R′ = SiMe3 and tBu. For the former the step-shaped structure is still present, but the latter forms an eight-membered ring. Although these tBu derivatives are synthesized in diethyl ether, their lithium atoms are not coordinated by donor molecules, in contrast to those in the phenyl-substituted species.

Alkali Salts of Octamethylcyclotetrasilazane - Synthesis and Crystal Structures Octamethylcyclotetrasilazane reacts with n-butyllithium or the elements sodium and potassium to give the alkali salt 1, 2, and 3. 1-3 crystallize as dimeric THF adducts. In the dimers two eight-membered rings are connected by a planar alkali metal-nitrogen four-membered ring. Lithium is tricoordinated in 1, sodium tetracoordinated in 2, and potassium penta- and hexacoordinated in 3. The crystal structures of the alkali salts are discussed and compared with one another. The coordinatively bonded TH in the lithium compound 1 can be exchanged with the Lewis base TMEDA. The crystal structure of 4 shows a higher symmetry than that of 1.

From (ClSN)3 (1) and ClCN (2) 1,3,5-trichloro-1,3,2,4,6-dithiatriazine (ClCN)(ClSN)2 (3) was prepared in 26% yield. 3 reacts slowly further with excess 2 to give thiatriazine (ClCN)2(ClSN) (14) and triazine (ClCN)3 (16). A mechanism for the (ClSN)/(ClCN) exchange is proposed. The structures of 3, 14, and 16 have been determined by X-ray diffraction. The bonding situation in the system (ClSN)n(ClCN)3-n (n = 0 - 3) is discussed.

Die Produktbildung in der Reaktion von 1-Trimethylsilyl-2,2,4,4,6,6-hexamethylcyclotrisilazan 1 mit Butyllithium und Fluorsilanen ist durch die Reaktionsbedingungen steuerbar. Lithiiertes 1 reagiert mit F3SiN(SiMe3)2 bei tiefen Temperaturen unter Bildung der Mono- und Disubstitutionsverbindungen 2, 3 sowie des 1,3,5,7-Tetraaza-2,4,6,8-tetrasilabicyclo [4.2.0] octans 4. Ein permethylierter Bicyclus (5) entsteht in analoger Reaktion mit MeSiF2N(SiMe3)2. Bei Raumtemperatur reagiert das Monolithiumsalz von 1 mit F3SiN(SiMe3)2 unter Kontraktion zum Cyclodisilazan 6. 6 bildet mit Butyllithium das Lithiumderivat 7. 7 reagiert mit F3SiN(SiMe3)2 zu 8, dem zu 3 isomeren Cyclodisilazan. In der Reaktion von lithiiertem 1 mit Me2SiF2 wird das silylverbrückte Cyclodisilazan 9 erhalten, das in Pyrolysereaktionen ein geeignetes Ausgangsmaterial für Si3N4-Keramiken darstellt. Die Resultate der Röntgenstrukturanalyse von 7 und der Pyrolyse von 9 werden mitgeteilt. Translated Abstract: The products obtained in the reaction of 1-trimethylsilyl-2,2,4,4,6,6-hexamethylcyclotrisilazane 1 with butyllithium and fluorosilanes depend on the reaction conditions. Lithiated 1 reacts with SiF3N(SiMe3)2 at low temperatures to give the mono- and disubstituted compounds (2, 3) and the 1,3,5,7-tetraaza-2,4,6,8-tetrasilabicyclo-[4.2.0] octane 4. The permethylated bicyclus 5 is formed in the analogous reaction with MeSiF2N(SiMe3)2. At room temperature the monolithium salt of 1 reacts with SiF3N(SiMe3)2 to give the cyclodisilazane 6. 6 forms with butyllithium the lithium derivate 7. 7 reacts with SiF3N(SiMe3)2 to give 8, an isomeric cyclodisilazane of 3. In the reaction of lithiated 1 with Me2SiF2 the silylcoupled cyclodisilazane 9 is obtained, which is a suitable precursor of Si3N4 ceramics. The results of the crystal structure determination of 7 and the results of the pyrolysis of 9 are reported.

From the reaction of the sulfenyl chloride 1 with the monosilylated amines 2a, b the sulfenamides 3a, b are obtained in good yields. 1,3-Dehydrohalogenation of 3a, b with sodium hexamethyldisilazanide yields the thione S-imides 5a, b. Imide 5a reacts with norbornene (6) to produce the isothiazolidine derivative 7. The structures of 5b and 7 are confirmed by X-ray analyses.

Mono- und dilithiiertes Octamethylcyclotetrasilazan (1, 6) reagieren mit Fluorsilanen bzw. F2BN(SiMe3)2 unter Erhalt des Cyclotetrasilazangerüstes zu den mono- und disubstituierten Verbindungen 2-5 und 7-13. Bei der Umsetzung des Dilithiumsalzes (6) mit einem Fluorsilan im Molverhältnis von 1:1 werden die Bicyclen 14 und 15 erhalten. Kristallographische Untersuchungen von 2, 3, 8 und 9 zeigen, daß der monosilylierte Achtring in einer Wannen-, der disilylierte Achtring in einer Sesselkonformation vorliegt. In der Kristallstruktur des Bicyclus 14 zeigen die Stickstoffatome der Si3N-Einheiten eine pyramidale Umgebung. Translated Abstract: Fluorosilyl and Fluoroboryl Substituted Cyclotetrasilazanes. Synthesis and Crystal Structures Mono- and dilithiated octamethylcyclotetrasilazanes (1, 6) react with fluorosilanes and F2BN(SiMe3)2, respectively, under retention of the cyclotetrasilazane structure yielding the mono- and disubstituted compounds 2-5 and 7-13. In the reaction of the dilithium compound 6 with a fluorsilane in equivalent amounts, the bicyclic compounds 14 and 15 are obtained. Crystallographic investigations of the compounds 2, 3, 8, and 9 indicate that the monosilylated eight-membered ring has a cradle conformation while the disilylated ring has a chair conformation. The X-ray structure of the bicyclic system 14 indicates that the nitrogen atoms of the Si3N-units have a pyramidal environment.

Alkali- and alkaline-earth-metal iminoaminosulfinates have been synthesised and characterized by X-ray diffraction and solid-state NMR investigations. The viability of metal-exchange reactions has been demonstrated resulting in a magnesium and a copper(I) derivative. The structural investigations reveal the presence of different structures, which can be classified into four types. Phase transitions between different structural types involving the loss of donor solvent have been observed by solid-state magic angle spinning experiments.

Syntheses and structures of novel inorganic heterocycles containing two or three transition metal atoms are reported. Examples include the first triazatrimetallabenzene derivative, [Cp Ta(Cl)N]3, as well as eight-membered phosphazene rings containing two vanadium atoms.

RR'SF2 reacts with Me3SiNCO to give the corresponding N-(fluoroformyl)sulfur imides FC(O)NSRR' [R = NMe2, R' = F (7); R' = CF3 (9)]. From these AsF5 abstracts F- with formation of isocyanatosulfonium salts ONC - SRR' + AsF-6 [R = F, R' = CF3 (6); R = NMe2, R' = F (8); R = NMe2, R' = CF3 (10)]. The spectroscopic properties of the fluoroformyl derivatives and of the isocyanato salts are discussed. The structures of 8 and 10 are determined by X-ray analyses.

N,N-Dilithiobis(alkylamino)phenylboranes as Starting Materials for Four-Membered Metallacycles Reactions of N,N-Dilithiobis(alkylamino)phenylboranes with tetrachlorides MCl4 (M = Ge, Sn, Ti, Zr) produce the 4,4-spirobi(1,3-dialkyl-2-phenyl-1,3-diaza-2-bora-4-metalla-cyclobutane) derivatives 1a, 1b, 2b, 3a, and 3b. With diorganylmetal dihalides R2MX2(M = Sn, Zr; X = Cl, Br), the 1,3-diaza-2-bora-4-metallacyclobutanes 2a and 4 are obtained. For 3a an X-ray structure analysis has been performed.

MeN = S(CF3)2 (5) is alkylated by Me3O AsF6 to Me2N-S(CF3)2 AsF6 (4). From 5 and MeOp. AsF6 (6) MeOS(O)-N(Me)S(CF3)2 AsF6 (7) is formed as a relatively stable primary product. Decomposition of 7 gives the expected 4 only in poor yield. Nucleophilic substitution of the sulfur-bonded fluorine in CF3SF2 AsF6 (8) by Me3SiNMe2 yields CF3S(NMe2)2 AsF6 (9). Similarly, (CF3)2CFSF2 AsF6 (10) reacts with dimethyl(trimethylsilyl)amine to give (CF3)2CFS(NMe2)2 AsF6 (11). The structures of 4 and 9 are elucidated by X-ray analyses, and the influence of the substituents on the bonding is discussed.

Unsolvated RbN(SiMe3)z (1) and CsN(SiMe3)z (2) have been prepared from rubidium and cesium metal respectively and excess hexamethyldisilazane. The molecular structures of the polymeric dioxane adducts NaN(SiMes) .C4HsO2 (3) and [MN(S~M~~)~~.~C~H~(4O, M~ ]=. ROb; .5, ~MC =~ CHs)~ haOveZ been determined by low-temperature single-crystal X-ray diffraction.

The new compounds Se[N(SiMe3)2]a2n d Te[N(SiMe3)2]h2a ve been prepared in relatively good yields and their crystal structures determined by X-ray crystallography at low temperature. The p. compound crystallizes in the monoclinic system, space group C2/c, with Z = 4 and unit cell dimensions u = 1705.4 (3) pm, b = 642.2 (2) pm, c = 21 16.7 (4) pm, and j3 = 108.19 (2)O. The Te compound crystallizes in the triclinic system, space group Pi, with Z = 2 and unit cell dimensions a = 903.9 (3) pm, b = I 1 11.7 (4) pm, c = 1241.0 (4) pm, CY = 88.67 (2)O, 0 = 73.68 (3)O, and y = 69.10 (2)’. The crystals of both compounds consist of isolated Ch[N(SiMe3)J2 (Ch = Se, Te) molecules containing V-shaped ChN2 units with Se-N distances of 186.9 (2) pm and Te-N distances of 205.3 (2) and 204.5 (2) pm. The NChN bond angles were found to be 108.0 ( I ) and 105.8 ( 1 ) O for the Se and Te compounds, respectively. No significant intermolecular Ch-N interactions were found in the two compounds, but an intermolecular Te-Te distance of 377 pm, substantially less than the corresponding van der Waals distance, is present in the Te compound.

Ring Contractions of Octamethylcyclotetrasilazanes to Silyl-Substituted Cyclotrisilazanes Reaction of the mono- and dilithium derivatives of bis(fluorsilyl)-substituted cyclotetrasilazanes with fluorosilanes and fluoroboranes leads to ring contraction with formation of cyclotrisilazanes (1 - 8). The isomerisation is proved by the crystal structure determination of 1 and by NMR spectroscopy.

The bidentate sulfinimidamide ligand has almost the same bulk as the cyclopentadienyl l&and. Two distinct structural types of highly reactive lithium sulfinimidamides, commonly used reagents, have been identified by X-ray diffraction and solution NMR studies. In the crystalline state the diethyl ether adducts [(Me,SiN),S(C,H,)Li],.Et,O and [(Me,S~X’BuN)S(C,H,)Lil,.EtzO adopt a twisted tricyclic structure with both a four coordinate and a three coordinate lithium atom in the same aggregate. The ‘H NMR spectra at various temperatures and the low temperature phase-sensitive 6Li, ‘H HOEp. NMR experiment show that this structure is essentially retained in solution. The smaller bulk and higher polarity of tetrahydrofuran compared with diethyl ether results in the coordination of two solvent molecules to give [(Me,S~) S(C,H,)Li.THF],, which has a centrosymmetric stair-shaped tricyclic structure consisting of three fused four-membered rings.

Die Lithiumverbindungen der Aminofluorsilane (1-7) reagieren mit MHal4 (M = Si, Ge, Sn; Hal = Cl, Br) zu Verbindungen des Typs (8-10, 12, 14: M = Si, 13, 15, 16: M = Ge, 17: M = Sn). Unter intermolekularem Halogenaustausch werden 11, 12 und 14 erhalten, R2SiHal SiHal2F (11, 12: Hal = Cl, 14: Hal = Br). Der Halogenaustausch ist substituentenabhängig und wird nur an halogenierten Disilazanen mit den Substituenten R = Alkyl und Aryl beobachtet. Von 8 und 12 wurde eine Kristallstrukturanalyse durchgeführt. Translated Abstract: Syntheses, Halogeno-Exchange Reactions, and Crystal Structures of Functional Silylamines Lithium compounds of aminofluorosilanes (1-7) react with MHal4 (M = Si, Ge, Sn; Hal = Cl, Br) to give compounds of the type (8-10, 12, 14: M = Si, 13, 15, 16: M = Ge, 17: M = Sn). 11, 12, 14, R2SiHal SiHal2F (11, 12: Hal = Cl, 14. Hal = Br), are obtained by an intermolecular halogeno exchange. The halogeno exchange depends on the substituents and is only observed by halogenated disilazanes with the substituents R = alkyl and aryl. The crystal structures of 8 and 12 were determined.

Li(12-crown-4)2]+[Li({N(SiMe3)}2SPh)2]–1 is the product of the reaction of Me3SiNSNSiMe3 with phenyllithium using 12-crown-4 as a donor and has an ion-separated structure which is unique for alkali metal sulphinamidino derivatives; at room temperature 1 undergoes a phase transformation, and a preliminary examination of this process by high-resolution solid-state 7Li NMR spectroscopy shows, for the first time, the presence of three resolvable resonances.

Depending on the reaction conditions, Ph2P(NSiMe3)[N(SiMe3)2]reacts with TiCl4 to form the titanadiazaphosphetidines Ph2P[µ-N(SiMe3)]2TiCl3MeCN (1) and Ph2P[µ-N(SiMe3)]2TiCl2,[NPPh2N(SiMe3)2](2). Compound (1) dimerises slowly in solution with elimination of Me3SiCl to yield a tricyclic system containing a central Ti2N2 ring (3). X-Ray analyses of these compounds show (1) and (3) to be monoclinic, space group P21/n, while (2) is triclinic, space group P. Compound (2) has a Ti–N–P angle of 170.3(7)° and a short exocyclic Ti–N bond of 179.2(9) pm.