Untersuchungen zur Lithiierung und Substitution des HP[Si(t-Bu)2]2PH

Investigations on Lithiation and Substitution of HP[Si(t-Bu)₂]₂PH HP[Si(t-Bu)₂]₂PH 1 is monolithiated by reaction with LiPH₂ · DME or LiBu in toluene. The crystalline compound HP[Si(t-Bu)₂]₂PLi · 2 DME 2 can be isolated in DME. Reaction of 2 with Me₂SiCl₂ leads to HP[Si(t-Bu)₂]₂P? SiMe₂Cl 4 , ClMe₂Si? P[Si(t-Bu)₂]₂P? SiMe₂Cl 5 , HP[Si(t-Bu)₂]₂P? SiMe₂? P[Si(t-Bu)₂] ₂PH 6 . Isomerization by Li/H migration between 4 and 2 leads to the formation of 5 . Reaction of Li(t-Bu) with 1 or 2 yields LiP[Si(t-Bu)₂]₂PLi 3 by further lithiation. 3 could not be obtained purely, only in a mixture with 2 . These compounds favourably generate with t-BuPCl₂ in hexane Cl(t-Bu)P? P[Si(t-Bu)₂]₂P? P(t-Bu)Cl 9 , in THF HP[Si(t-Bu)₂]₂P? P(t-Bu)? P[Si(t-Bu)₂]₂ PH 12 (main product), 9 , H(t-Bu)P? P[Si(t-Bu)₂]₂P? P(t-Bu)Cl 10 , H(t-Bu)P? P[Si(t-Bu)₂]₂P? P(t-Bu)H 11 as well as HP[Si(t-Bu)₂]₂P? P(t-Bu)H 13 and HP[Si(t-Bu)₂]₂P? P(t-Bu)₂ 14 .     

2,4‐Disila‐1,3,5‐oxadiazin,Cyclodisilazan‐Carbonsäure‐silylamid und ‐silylester

The lithium salts of the Me₃Si‐ as well as Me₃Si‐ and Me₂SiF‐substituted Cyclotrisilazanes I and II react with tert‐butylacylchloride under ring contraction and formation of the cyclodisilazane‐silylester, Me₃SiN(SiMe₂–N)₂SiMe₂–O–CO–CMe₃ ( 1 ). The lithium salt of the fluorodi‐methylsilyl‐substituted cyclotrisilazan III forms with benzoylchloride primarily in the analogous reaction the carboxy‐silyl‐amide, Me₂SiF(N–SiMe₂)₂SiMe₂–NH–CO–C₆H₅⁺ ( 2 ), which can be converted with III and benzoylchloride into the cyclodisilazane‐silylester, Me₂SiF(NSiMe₂)₂SiMe₂–O–CO–C₆H₅, ( 3 ). A silylester substituted six‐membered disila‐oxadiazine ( 4 ) is the result of the reaction of the lithiated cyclotrisilazane, (Me₂SiNH)₂, (Me₂SiNLi) with tert‐butyl‐acylchloride. The reaction includes anionic ring contraction and can be rationilized by a process analogous to keto‐enol‐tautomerism. Dilithiated octamethyl‐cyclotetrasilazane, (Me₂SiNHMe₂SiNLi)₂, reacts with tert‐butyl‐acylchloride or benzoylchloride in a molar ratio 1:2 to yield symmetrically acylestersubstituted cyclodisilazanes, (RCO–O–SiMe₂–NSiMe₂)₂, R = C₆H₅ ( 5 ), CMe₃ ( 6 ). The reaction mechanisms are discussed and the crystal structures of 2 and 6 are reported.     

From New Zirconium-Phosphanide to Phosphinidene Complexes

Abstract

Lithiated primary silylphosphanes and -arsanes react with rircOnocene-chloride-hydride to give planar Zr(III)₂-E2-ringsystems (R = SiMc₂Thex (I), Si(i-Pr)₃, SiF(t-Bu)Is). However, the complexes can also be synthesized by conversion of zirconocene-dichloride with lithiated silylphosphanes. Reductive dehydrogenation of 1 through heating with Pd on activated charcoal or [(Ph₃P)₂Pt(C₂H₄)] in toluene leads to 2.     

Synthese,Charakterisierung und Struktur von P7(t-Bu3Si)3 („Tris(supersilyl)heptaphosphan(3)”︁)

Synthesis, Characterization, and Structure of P₇(t-Bu₃Si)₃ (?Tris(supersilyl)heptaphosphane(3)”? Tris(tri-tert-butylsilyl)heptaphosphanortricyclane P₇(t-Bu₃Si)₃ 1 is obtained from the reaction of (t-Bu)₃Si? Si(t-Bu)₃ with white phosphorus and forms colorless to pale yellow thermostable crystals. 1 is identified by the complete analysis of its ³¹P{¹H} NMR spectrum (A[MX]₃ spin system) as well as by a single crystal structure determination (space group Pca2₁, a = 170.76(2)pm, b = 131.14(3)pm, c = 426.61(5)pm, α = β = γ= 90°, Z = 8 formula units in the elementary cell). The steric demand of the (t-Bu)₃Si-Groups causes an increase of the exocyclic bond angles at the equatorial phosphorus atoms P^e, while it does not particularly influence the P₇-skeleton. Chlorine (r.t.) and bromine (70°C) degrade the P₇-cage of 1 with formation of PX₃ and (t-Bu)₃SiX (X = Cl, Br).     

Die CuCl-katalysierte Reaktion von Trimethylsilyl(t-butyl)chlorphosphan mit Dimethylzirconocen: Ein Beispiel der Tandem-Katalyse

The CuCl-catalyzed Reaction of Trimethylsilyl(t-butyl)chlorophosphane with Dimethylzirconocene: An Example for Tandem Catalysis t-BuP(SiMe₃)Cl was prepared from t-BuP(SiMe₃)₂ and hexachloroethane and reacted in situ with Cp₂ZrMe₂ in the presence of catalytic amounts of copper(I) chloride yielding t-Bu(Me)P? P(Cl)t-Bu ( 1 ) (2 : 1 reaction) or t-Bu(Me)P? P · (Me)t-Bu ( 2 ) (1 : 1 reaction) and Cp₂ZrCl(Me). To understand the course of reaction, the reaction of dimethylzirconocene with CuCl and the decomposition of t-BuP(SiMe₃)Cl in the presence of CuCl and tetrachloroethene were studied. The results suggest that CuCl reacts with t-BuP(SiMe₃)Cl in the presence of C₂Cl₄ to give t-Bu(Cl)P? P(Cl)t-Bu ( 3 ); simultaneously, CuCl reacts with Cp₂ZrMe₂ with formation of methylcopper, which reacts with 3 to give 1 or 2 , respectively.     

Cyclische Titanamide mit Sila-titana-diazacyclobutan-Struktur

Cyclic Titanium Amides with Sila-titana-diazacyclobutane Structure N,N′ dilithiated diaminosilanes Me₂Si(NHR)₂, R = i-Pr, t-Bu and Me₃Si, react with TiCl₄ in a 2:1 ratio to form spirocyclic titanium amides ( B, C 1 ; see Inhaltsübersicht). In a 1:1 ratio or upon reaction with (R′₂N)₂TiBr₂, R′ = Me, Et, titanacyclobutanes ( C 2—C 6 ) are obtained. Compounds with R = Me₃Si exhibit particularly high thermal stability.     

Steric Effects of Alkylmagnesium Chlorides in the Grignard Reaction with Silanes

Rate constants for the reactions of methylvinyldichlorosilane and tetraethoxysilane with alkylmagnesium chlorides RMgCl (R = Et, n-Bu, i-Bu, i-Pr, s-Bu, t-Bu) in diethyl ether were determined. Excellent correlations of rate data with steric constants E_S(Si) by Cartledge and v′ by Charton were found for the reaction of methylvinyldichlorosilane. Linear correlations with break points were obtained for the tetraethoxysilane reaction. It was assumed that this could be referred to a change in the reaction mechanism.     

Zur Bildung cyclischer Silylphosphane Umsetzung von Li-Phosphiden mit R2SiCl2 (R = Me,Et, t-Bu)

Formation of Cyclic Silylphosphanes. Reaction of Li-Phosphides with R₂SiCl₂ (R? Me, Et, t-Bu) The reaction of Me₂SiCl₂ with Li-phosphides (mixture of LiPH₂, Li₂PH) leads to the formation of Me₂Si(PH₂)Cl 1 , Me₂Si(PH₂)₂ 2 , H₂P? SiMe₂? PH? SiMe₂Cl 3 , (H₂P? SiMe₂)₂PH 4 , (HP? SiMe₂)₃ 6 , 5 , 7 , 8 , 9 , 10 , 40 . Excess of phosphides in Et₂O – as well as excess of LiPH₂ – favourably forms 10 . Li₂PH (virtually free of Li₃P and LiPH₂) is obtained by reaction of LiPH₂ · DME with LiBu; Li₃P by reaction of PH₃ with LiBu in toluene. Isomerization by Li/H migration determines the course of reaction of the PH-bearing compounds with Li-phosphides. With Me₂SiCl₂ Li₃P mainly generates compound 10 . The reaction of the Li-phosphides with Et₂SiCl₂ mainly leads to (HP? SiEt₂)₃ 18 and (HP? SiEt₂)₂ 17 as well as to Et₂Si(PH₂)Cl 11 , Et₂Si(PH₂)₂ 12 , (ClEt₂Si)₂PH 13 , H₂P? SiEt₂? PH? SiEt₂Cl 14 , (H₂P? SiEt₂)₂PH 15 and 16 . In the reaction with LiPH₂ · DME the same compounds are obtained and isomerization by Li/H migration (formation of PH₃) already begins at ?70°C. In toluene ClEt₂Si? P(SiEt₂)₂P? SiEt₂Cl is additionally formed. Derivatives of 9, 10, 40 are not observed. The reaction of (t-Bu)₂SiCl₂ with LiPH₂ leads to HP[Si(t-Bu)₂]₂PH 20 (yield 76%) and formation of PH₃, the reaction with Li₂PH to 20 (54%) besides HP[Si(t-Bu)₂]₂PLi 21 .     

Reactions of dodecamethylcyclohexasilane and polydimethylsilane with metal chlorides

The reactions of dodecamethylcyclohexasilane and high-molecular-weight polydimethylsilane with chlorides of I, II, IV-VI and VIII Group metals at high temperature in the absence of a solvent were studied. The interaction of (Me₂Si)₆ with metal chlorides proceeds with the cleavage of SiSi and SiC bonds with the formation of chloro derivatives of linear and cyclic permethyloligosilanes. The reactions of polydimethylsilane with metal chlorides afford mixtures of α,ω-dichlorooligosilanes, Cl(Me₂Si)_nCl (n=2-9). The influence of the reaction conditions (temperature, reaction time and the reagent ratio) on the composition and yields of the reaction products was examined.     

On the Reactivity of Disilylphosphido Complexes of Transition Metals Towards Acid Chlorides

Abstract

The first phosphaalkenyl complex Cp(CO)₂Fe-P=C (OSiMe₃)(t-Bu) was generated from Cp(CO)₂FeP(SiMe₃)₂ and t-Bu(CO)Cl. In order to test the validity of this synthetic approach, we varied the ring ligand (Cp, C₅Me₅), the metal (Fe, Ru, Os), the main group element (P, As), and the carbonyl chlorides. The diphosphenyl complexes (C₅Me₅)(CO)₂M-P=P-[2,4,6-t-Bu₃C₆H₂] were obtained from (C₅Me₅)(CO)₂M-P(SiMe₃)₂ and the corresponding phosphonous chloride. These metallated diphosphenes are easily converted to diphospho-ureas by treatment with Fe₂(CO)₉.     

Condensation chlorure d'acide-organomagnesien en presence d'halogenure cuivreux: Competition des reactions heterolytique et homolytique. synthese de cetones aliphatiques ramifiees

The reactivity of seven sterically hindered acid chlorides RCOCl towards ethylmagnesium bromide in the presence of cuprous chloride has been studied. In addition to the ketones RCOEt, the compounds RCOCOR, RCOR, RR, RH and R(H) are produced by a radical reaction. The condensation of R′MgX with iPr₂CHCOCl in the presence of cuprous halide proceeds via alkylcopper species R′Cu.MgXX′ which reacts with the acid chloride to produce the ketone RCOR′. The radical process is initiated by the decomposition of the alkylcopper intermediate. The effect of temperature, solvent and structure on the stability of the alkylcopper on optimal conditions for ketonisation has been studied; this is demonstrated specifically by the synthesis of 9 hindered ketones iPr₂CHCOR′, where Me? R′ ? Et₃C and Tr.     

Übergangsmetall-substituierte acylphosphane und phosphaalkene: VIII. Dicarbonylcyclopentadienyleisen-substituierte phosphaalkene mit Fe-P-einfachbindung: synthese und struktur

Phosphaalkenyliron complexes with covalent metal-phosphorus bonds are synthesized from (η⁵-C₅H₅)(CO)₂FeP(SiMe₃)₂ and acid chlorides RC(O)Cl (R = Ph, 2,4,6-Me₃C₆H₂, t-Bu). The molecular structure of (Z)-(η⁵-C₅H₅)(CO)₂FePC(OSi-Me₃)(t-Bu) is established by X-ray structure analysis.     

Synthese von Bis- und Tris(trimethylsilyl)methyl-aminofluorsilanen

Synthesis of Bis- and Tris(trimethylsilyl)-methyl-aminofluorosilanes Lithium-tris(trimethylsilyl)methane reacts with fluoro-silanes to give (Me₃Si)₃C—SiF₂R ( 1—3 , R = F, C₆H₅, CMe₃). 1 and 2 react with lithiated amines to aminofluorosilanes 4 a, 5 a, 6 a , and with a 1, 3-migration of a silyl group to the structure isomeric trimethylsilylaminofluorsilanes 4 b, 5 b, 6 b, 7, 8 . The disubstituted NH-compound 9 is obtained in the reaction of 1 with LiNH₂.     

Zur Reaktivität von Disilylarsenido-Eisenkomplexen gegenüber Carbonsäurechloriden Die ersten Arsaalkenyl- und Diacylarsenidokomplexe. Röntgen-Strukturanalyse von Z-[(η5-C5H5)(CO)2Fe?AsC(OSiMe3)(t-Bu)]

On the Reactivity of Disilylarsenido Iron Complexes towards Carbonyl Chlorides: The First Arsaalkenyl- and Diacylarsenido Complexes. X-Ray Structure Analysis of Z-[(η⁵-C₅H₅)(CO)₂Fe? As?C(OSiMe₃)(t-Bu)] The reaction of equimolar amounts of (η⁵-C₅H₅)(CO)₂FeAs(SiMe₃)₂ ( 1a ) with the carbonyl chlorides RC(O)Cl (R = t-Bu, 2,4,6-Me₃C₆H₂ and 2,4,6-t-Bu₃C₆H₂) yields the arsaalkenyl complexes Z-[(η⁵-C₅H₅)(CO)₂Fe? As?;C(OSiMe₃)R ( 2–4 )]. The diacylarsenido complexes (η⁵-C₅H₅)(CO)₂Fe? As[C(O)R]₂ ( 5, 6 ) are generated by treatment of 1a with two equivalents of pivaloyl chloride or mesitoyl chloride, respectively. The As?C-double bond length of 2 (1.821(2) Å) was determined by single crystal x-ray analysis.     

Aspects of tautomerism. 8. Solvolysis of some pseudo and normal acid chlorides

Pseudo acid chlorides derived from levulinic acid ando-benzoyl-benzoic acid, solvolyse in aqueous acetone, aqueous dioxane and aqueous dimethylformamide by aS _Nl process. Their reaction pattern is distinct from that of typical normal acid chlorides, viz.,p-benzoylbenzoyl chloride and fluorene-9-one-1-carboxylic acid chloride, which solvolyse by aS _N2 pathway. No evidence for tautomerism could be obtained either between the normal and pseudo forms of the acid chlorides or the derived ion pairs.     

Highly efficient synthesis of capsaicin analogues by condensation of vanillylamine and acyl chlorides in a biphase H2O/CHCl3 system

Highly efficient synthesis of capsaicin analogues was developed using condensation of vanillylamine with acyl chlorides in a biphase H₂O/CHCl₃ system under mild conditions. For C4-C18 aliphatic or aromatic acyl chlorides, the yields were up to 93-96% with high purity after a simple work-up procedure, and only 1-1.16 equiv of acyl chloride was needed in the reaction.     

Zinc enolates: C- or O-metallation?

Two methods have been used for the generation of zinc enolates: the reaction of EtZnOMe with enol acetates, and that of lithium enolates with zinc chloride. Most of the zinc compounds prepared proved to be very reactive towards carbonyl functions, and so they cannot be isolated from the EtZnOMe/enol acetate system. The final products of these reactions are polymerisation and self-condensation products and β-diketonates, the latter being formed by condensation reactions of the zinc enolates with an acetate molecule. The structure of [EtZnOMe·Zn(Pac)₂]₂ (HPac = pivaloylacetone, (CH₃)₃CCOCH₂COCH₃), isolated in 20% yield from the reaction of EtZnOMe with CH₃COOC(t-Bu)CH₂, was determined by X-ray diffraction analysis. The compound forms monoclinic crystals, space group P2₁/c, with two dimers in a cell of dimensions a 11.677(4), b 18.299(9) and c 12.719(5) Å and β 117.26(3)°. The structure closely resembles that of the known complex [PhZnOPh·Zn(Pac)₂]₂.The complications involving reactions of zinc enolates with enol acetates were avoided by treating lithium enolates with zinc chloride. Polymerization and self-condensation could be prevented by using the very bulky enolate LiOC(t-Bu)CMe₂. In this way, the corresponding stable zinc enolate RZnCl·THF was obtained as a dissociating dimer. No replacement of the second chlorine atom by an enolate group occurred even when a large excess of lithium enolate was used.The reactivity of the zinc enolates suggests that they contain both zinccarbon and zincoxygen bonds. They are assumed to have a cyclic structure which resembles that of the Reformatsky reagent.     

Poly(vinyl chloride) stabilisation with organo-tin compounds—Part II: Catalysis of the dehydrochlorination by butyl-tin chlorides

The catalytic effect of the various butyl-tin chlorides on the dehydrochlorination reaction of chlorohexene, used as a model compound for allylic chlorides in poly(vinyl chloride), has been studied in tetrahydrofuran and dichloroethane solutions. The reaction follows an E2 mechanism, the rate determining step being the formation of a delocalised allylic carbocation. The catalytic power is directly related to the Lewis acidity of the tin chlorides and, further, RSnCl₃ is comparable with ZnCl₂, although it is more sensitive to complexing with weak Lewis bases. In the presence of poly(vinyl chloride) at 180°C, these butyl-tin chlorides show a retardation effect on dehydrochlorination, superimposed on a catalytic effect which increases with the Lewis acidity; however, in these conditions, RSnCl₃ is much less efficient than ZnCl₂ in catalysing the dehydrochlorination reaction.     

Acyclische und cyclische Silylhydrazone und Hydrazonylsilane

Acyclic and Cyclic Silylhydrazones and Hydrazonylsilanes Dimethylketone-di-tert-butylmethylsilylhydrazone ( 1 ) is obtained in the reaction of the silylhydrazine and dimethylketone by condensation. Di-tert-butyldifluorosilane reacts with lithiated hydrazones to give fluorosilylhydrazones 2–4 , (CMe₃)₂SiF? NH? N = CRR′, ( 2 : R=Me, R′=CMe₃; 3 : R,R′=CHMe₂; 4 : R,R′=Ph). The bis(hydrazonyl)silane 5 , (CMe₃)₂Si(NH? N=CPh₂)₂, is formed in a molar ratio 1:2. Tris( 6 )- and tetrakis(hydrazonyl)silanes ( 7 ) are obtained from CMe₃SiF₃ ( 6 ), SiF₄ ( 7 ), and lithiated tert-butylmethylketon-hydrazone. The lithium derivatives 8–11 are formed in the reaction of 1–4 with butyllithium. Bis(silyl)hydrazones ( 12–15 ) are the result of the reaction of halogensilanes and the lithium derivatives of 1(8), 2(9) and 3(10); 12 : (CMe₃)₂SiMe(CMe₃SiF₂)-N? N=CMe₂, 13 : (CMe₃)₂MeSi(PhSiF₂)N? N=CMe₂, 14 : (CMe₃)₂SiF(Me₃Si)N? N=C(Me)(CMe₃), 15 : (CMe₃)₂SiF (SiMe₃)N? N=C(CHMe₂)₂. Saltelimination out of 10 und 11 leads to the formation of the first bis(imino)-2,2,4,4-cyclodisilazanes, 16 :[(CMe₃)₂ SiN? N=C(CHMe₂)₂]₂, 17 : [(CMe₃)₂SiN? N=CPh₂]₂. Cyclisation occurs in the reaction of 12 und 14 with tert-butyllithium, 2-silyl-1,2-diaza-3-sila-5-cyclopentenes ( 18 and 19 ) are formed. Dilithiated 1 reacts with SiF₄ to give the spirocyclic compound 20 . HF-elimination from 18 and dimerisation of the intermediate diazasilacyclopentadiens lead to the formation of the tricyclus 21 .     

Synthesis and desilylation of some bis(trimethylsilyl)alkenes and polymers bearing bis(silyl)alkenyl groups

The synthesis of various vinylbis(silanes) from some aryl and heteroaryl aldehydes and (Me₃Si)₃CLi in Et₂O is described. Friedel-Crafts reaction of 1,1-bis(trimethylsilyl)-2-(2-naphthyl)ethene with various acyl chlorides (RCOCl, R = Me, Et, i-Pr, i-Bu, n-pent) gave the corresponding α-silyl-α,β-unsaturated enones with high E steroselectivity. Moreover, poly(styrene)-co-[2,2-bis(trimethylsilyl)ethenyl(styrene)] obtained via the reaction of polymers bearing pendant enone functions and (Me₃Si)₃CLi, reacts with the same acyl chlorides in the presence of catalytic amount of AlCl₃ to give the new macromolecules bearing α-silyl-α,β-unsaturated enones and α,β-unsaturated enones.