78907-56-9Relevant academic research and scientific papers
Dimere der Ethene Me2E=C(SiMe3)2 (E=Si, Ge, Sn): Auf welchem Wege entstehen sie aus Me2EX-CM(SiMe3)2? Wie sind sie strukturiert?
Wiberg,Passler,Wagner,Polborn
, p. 292 - 303 (2007/10/03)
Alkali metal organyls or silyls MR (e.g. LiMe, LinBu, LitBu, LiPh, LiCH(SiMe3)2, LiC(SiMe3)3, NaSitBu3) convert equimolar amounts of bromomethanes Me2EX-CBr(SiMe3)2 with E=Si, Ge, Sn and electronegative substituents X (e.g. F, Br, OPh) in organic solvents (e.g. pentane, diethyl ether, tetrahydrofuran) (i) by a very fast Br/M exchange into the 'metalation products' Me2EX-CM(SiMe3)2, which thermolyze under formation of 'cyclobutanes' [-Me2E-C(SiMe3)2-]2, and (ii) to a lesser extent by X/R exchange into 'substitution products' Me2ER-CBr(SiMe3)2. As shown by trapping experiments, the unsaturated compounds Me2E=C(SiMe3)2 play the role of short-lived intermediates in both reactions. They are formed from Me2EX-CM(SiMe3)2 by MX elimination and add the present alkalimetal compounds Me2EX-CM(SiMe3)2≡MR′ or MR, respectively. The products Me2ER′-CM(SiMe3)2 with R′=C(EXMe2)(SiMe3)2, obtained in this way, eliminate MX under formation of the mentioned 'cyclobutanes'. On the other hand, the compounds Me2ER-CM(SiMe3)2 convert unreacted Me2EX-CBr(SiMe3)2 in Me2EX-CM(SiMe3)2 under formation of Me2ER-CBr(SiMe3)2. Relative rates of both the metalation reactions and the salt eliminations are determined. X-ray structure analyses of [-Me2E-C(SiMe3)2-]2 (E=Si, Ge, Sn) prove their 1,3-dielementacyclobutane structure with planar four-membered ECEC rings.
Reactivity of the Labile Silaethene Me2Si=C(SiMe3)2, Stored as Ph2C=NSiMe3 Adducts
Wiberg, N.,Preiner, G.,Wagner, G.,Koepf, H.
, p. 1062 - 1074 (2007/10/02)
Silaethene Me2Si=C(SiMe3)2 (1), stored as Ph2C=NSiMe3 adducts and regenerated from the adducts at about 100 deg C as a reaction intermediate, combines with reactants a-b (e.g.HO-H, RO-H, RCOO-H, RS-H, RHN-H, Ph2CN-H, RO-SiR3, R2N-SiR3, Ph2CN-SiR3, Cl-GeR3, Cl-SnR3) with insertion into the a-b bond, with a=b (e.g.O=CPh2, Me3SiN=CPh2, CH2=CHOMe, cis-piperylene), a=b=c (e.g.RN=N=N, O=N=N), a=b-c=d (e.g. butadiene, isoprene, trans-piperylene, 2,3-dimethylbutadiene, cyclopentadiene, anthracene, benzophenone, N-trimethylsilylbenzophenoneimine) under -, - as well as -c ycloaddition and with a=b-c-H (e.g. propene, butenes, isoprene, 2,3-dimethylbutadiene, acetone) under ene reaction.According to relative reaction rates, insertion and -cycloadditions seem to proceed in two reaction steps, whereas -cycloadditions and ene reactions with organic dienes and enes obviously are one step reactions.For reactivities cf.Table I. - Key words: Silaethene Me2Si=C(SiMe3)2, Insertions, Cycloadditions, Relative Reactivities
Ungesaettigte Silicium- und Germaniumverbindungen XVI. Stabilisierung des Labilen Silaethens Me2Si=C(SiMe3)2 durch Adduktbildung mit Donoren. Reaktivitaet von Me2Si=C(Si(Me3)2NMe3
Wiberg, Nils,Koepf, Hubert
, p. 9 - 18 (2007/10/02)
Silaethene Me2Si=C(SiMe3)3 (1), unstable at -100 degC with regard to dimerization, forms an adduct Me2Si=C(SiMe3)2NMe3 (3) with trimethyl amine, metastable at 0 degC.It decomposes thermally to give 1 and NMe3 and can, therefore, serve as a source of 1.With 1 as an intermediate, the adduct 3 reacts with butadiene, cyclopentadiene, 2,3-dimethylbutadiene, Ph2C=NSiMe3, t-BuN3, isobutene, or acetone giving either cycloadducts or ene reaction products.Adduct 3 reacts with ROH (R0H, Me, t-Bu, Ph) to yield insertion products, probably by way of a proton adduct of 3, but not via 1.Other donors (D) of which NMe3 is an example form adducts 1D, producing a new class of silicon compounds.As the Lewis basicity of D, relative to 1, decrease (F- >NMe3>NEt3>Br->THF), the resistance to decomposition of the adducts 1D to the dimer of 1 and D also decreases.
On the Way to Silaethene Me2Si=C(SiMe3)2: Trisilylated Methanes (Me3Si)2(Me2XSi)CY (X=e. g. Hal, RO, RS; Y e. g. Br, Li)
Wiberg, Nils,Preiner, Gerhard,Schieda, Oswald
, p. 2087 - 2103 (2007/10/02)
Bromotrisilylmethanes (Me3Si)2(Me2XSi)CBr (1 - 15) are formed as a result of the reaction of (Me3Si)2(Me2PhSi)CBr (16) with iodine monochloride, bromine and iodine (X = Cl, Br, I) respectively, and also through the reaction of (Me3Si)2(Me2BrSi)CBr (1) with AgX (X = F, p-TolSO2, p-TolSO3, MesSO3, Ph2PO2, Ph2PO3, Ph2PO4) or MX (M = H, Li, Na; X = HO, RO, RS, Bu, Ph).Butyl- as well as phenyllithium convert bromotrisilylmethanes 1 - 16 at low temperatures into lithium derivatives (Me3Si)2(Me2XSi)CLi (1a - 16a).These are in some cases (X = R, RO) thermostable, whereas, in other cases they decompose more or less readily under LiX elimination and lead (in many cases via silaethene Me2Si=C(SiMe3)2) to the disilacyclobutane derivative 2 (17).Acids HZ (e. g.HCl, HOMe, Me3CBr) protonate the lithium compounds into (Me3Si)2(Me2XSi)CH as well as (Me3Si)2(Me2ZSi)CH.Butyl bromide converts the more stable lithium compounds (Me3Si)2(Me2XSi)CLi (X = R, RO, F, Ph2POn) into butyl derivatives (Me3Si)2(Me2XSi)CBu.
