Decamethylsilicocene reactions

Alkylation, betaine, 63-64, 67 Alkynes, decamethylsilicocene reactions with, 24-25... 

In 1989 Jutzi et al. reported the reaction of decamethylsilicocene 50 with tri-n-butylphosphine selenide in benzene at room temperature, leading to almost quantitative formation of a 1,3,2,4-diselenadisiletane derivative 52, a head-to-tail [2+2] cycloaddition reaction product of the initially formed silaneselone 51.35 The intermediacy of silaneselone 51 was experimentally supported by the reaction in the presence of 2,3-dimethyl-1,3-butadiene resulting in the formation of the corresponding [2+4] cycloaddition reaction product 53 (Scheme 14). 

The influence of the acidity of the relevant protic substrates on the final reaction products is further demonstrated by two examples shown in Scheme 2. Decamethylsilicocene (1) reacts with HBF4 to yield the compound [Cp SiF]4, whereas in the reaction with PyH+BF4 (Py=pyridine) the oxidative addition product Cp 2Si(H)F is formed. Reaction of 1 with two equivalents of F3CS03H leads to an ionic species,... 

We have recently prepared some new and very thermolabile CO- and N2 comPlexes derived from titanocene [1] or decamethyltitanocene [2], and have characterized them by their vibrational spectra. As well as "classical" matrix spectroscopy, we have used spectroscopy in liquid xenon (LXe). The application of chemistry and methodology indicates the decamethylsilicocene structure, which represents the first example of a stable jt-complex of divalent silicon [3]. Reaction with CO or N2 leads to the two title complexes [4] ... 

After a decade of research the basic principles in the chemistry of decamethylsilicocene (1) seem to be understood. This compound shows the reactivity of a nucleophilic silylene due to the fact that the Tt-bonded pentamethylcyclopentadienyl ligands are easily transferred to a-bonded substituents during the reaction. The steric requirements of these substituents permit reactions with bulky substrates. The migratory aptitude and the leaving-group character of the pentamethylcyclopentadienyl groups... 

Dative bonding, 229 Decamethylmetallocenes, 1-2, 6, 8-9, 20 of silicon see Decamethylsilicocene Decamethylsilicocene, 1-34 chemistry of, 9-31 structure, 4-7 synthesis, 3 1 Decomposition betaines, 37-38, 78-87 thiobetaines, 57-63, 65 for film deposition, 304-306 Dehalosilylation reaction, 260-262 Dehydrosilylation reaction, 262-264 Density functional theory (DFT), 177 Deposition, film, 257-258, 265, 301-303 DFT (density functional theory), 177 Diazasilole derivatives, decamethylsilicocene gives, 24-25... 

Clusters of the elements aluminum to thallium containing only one or two carbon atoms and strong direct element-element interactions, similar to boron rich car-baboranes, have not yet been synthesized, and also the corresponding silicon derivatives are relatively rare. To the best of our knowledge only one aluminum-silicon and one gallium-silicon cluster (1 and 2) has been reported in the literature. The reaction of metastable aluminum(I) chloride with decamethylsilicocene or with a mixture of SiCl4 and (AlCp )4, respectively, afforded black crystals of... 

The reactions quoted in the last paragraph and partly summarized in Scheme 19, all exploit the high electrophilidty of organometallic group 14 cations, and the reactivity follows conventional routes. Quite recently, however, a novel-type of chemistry for RsE cations came into attention. The decisive step in Jutzi s synthesis of ri -Cp Si, 91, by protonation of decamethylsilicocene, Cp 2Si, 28, " is most likely the fragmentation of the intermediate Cp 2Si -H cation 29 into the neutral MesCsH and the cation ri -Cp Si (see Scheme 20). The cation 91 can be regarded as synthetic equivalent for the singly coordinated silylidynium ri -Cp sj 92. 

The reaction of decamethylsilicocene, Si(Cp )2, with Au(PPh3)Cl, in toluene, resulted in insertion of the silylene into the Au-Cl bond and isolation of (Ph3P) AuSiCl(Cp )2 77. The compound is molecular, with a -interaction between a silicon-bound Cp substituent and the central gold atom [Au(l)-Cp centroi[Pg.221]

The formation of an intermediate difluorodisilene 25 (equation 8) was proposed by Jutzi and coworkers34 in the reaction of decamethylsilicocene with tetrafluoroboric acid. The disilene which was characterized by the 29Si NMR spectrum, then formed the isolable cyclotetrasilane by [2 + 2] cycloaddition. 

Oxygen transfer reactions were also examined by Jutzi and coworkers41 for the nucleophilic decamethylsilicocene 41. Silicocene 41 reacts with carbon dioxide under mild conditions to give two types of products, 46 and 47, depending on the solvent used, as shown in Scheme 17. 

In analogy to the reaction of decamethylsilicocene 41 with carbon dioxide leading to the generation of intermediary silanone 44, silicocene 41 was allowed to react with carbon oxysulfide under very mild conditions (—78 °C/toluene) to give the corresponding 1,3,2,4-dithiadisiletane derivative 81, a formal head-to-tail [2 + 2] cycloaddition reaction product of the initially formed silanethione 80 (Scheme 29)41b. 

Reaction of dichloro(pentamethylcyclopentadienyl)silane with lithium, sodium or potassium naphthalenide gives a mixture of elemental silicon, the corresponding alkali metal pentamethylcyclopentadienide and decamethylsilicocene (82) (equation 64)181. Compound 82 is formed as the only product in the reduction of dibromo-bis(pentamethylcyclopentadienyl)silane with potassium anthracenide (equation 65)182. 

The formal oxidation state of silicon changes from +11 to +IV in nearly all of the reactions with decamethylsilicocene (82) described so far, and the hapticity of the cyclopentadienyl ligand changes from /j5 to jj1. The latter phenomenon raises the question about the possibility of a haptotropic shift in the ground state molecule, which should lead to quite different silicon species in equilibrium, as shown in equation 81. 

Tetramesityldisilene quantitatively desulfurizes cyclohexene sulfide at room temperature <1993CC1348>. Products with Si-S bonds were obtained from a reaction between cyclohexene sulfide and decamethylsilicocene (Scheme 43) <1989AGE1518>. 

Although silylenes have been known for a long time as transient intermediates in thermal, photochemical or dehalogenation reactions, stable species have become available only recently. Si(II) compounds with coordination number larger than two have already been isolated in the late eighties, i.e., decamethylsilicocene prepared by Jutzi et al [1] and the tetracoordinated phosphine derivative obtained by Karsch et al [2]. 

Summary Decamethylsilicocene (1), the first Si(II) compound stable under ordinary conditions [1], is a h5 ercoordinated nucleophilic silylene, which reacts preferentially with electrophilic substrates [2], In the reaction of 1 with the electrophilic heterocumulenes CO2, COS and RNCS (R = Me, Ph), double bond species of the type Cp 2Si=X (X = O, S) are formed, which are stabilized via different routes to the silaheterocycles I-IV [3], Multistep rearrangement processes are postulated to explain the formation of the dithiasiletane derivatives V and VI in the reaction of 1 with CS2. A surprising polycyclic silaheterocycle VII is obtained in the reaction of 1 with hexafluorobutyne. With HMn(CO)s 1 reacts to the dimanganese-substituted silane VIII. In all reactions, the lone pair at silicon is involved, an r) -ri - rearrangement of the Cp ligands take place, and the formal oxidation state at Si changes to +4 in the final products. 

Decamethylsilicocene (1) reacts with carbon dioxide already under mild conditions. Surprisingly, the products obtained depend on the solvent used. Bubbling CO2 at room temperature for about 3 through a solution of 1 in pyridine led to the eight-membered cyclic compound 1 in about 65 % yield, whereas in toluene as solvent the spiro heterocyclic compound II was formed in about 70 % yield. 1 reacts with carbon oxysulfide already under very mild conditions A toluene solution of 1 was added to liquid COS at -78°C. The dithiadisiletane III was isolated in about 50 % yield after a reaction time of 2 at this temperature. Compound III, already known in the literature as the reaction product of 1 with sulfur [6], is poorly soluble in organic solvents. 

In the reaction of decamethylsilicocene (1) with methyl isothiocyanate, the dithiasiletane IV was isolated in about 60% yield after a reaction time of 16 h at room temperature (see Scheme 2). Slightly more drastic conditions (5 h, 65°C) were necessary for the reaction of 1 with phenyl isothiocyanate, which led to the corresponding dithiasiletane IV in 65 % yield. The formation of the IV was independent of the stoichiometry of the reactands. 

Decamethylsilicocene (1) reacts with alkynes having electron-withdrawing substituents (Me02CC=CC02Me, Me3SiC=CS02Ph) under formation of silacyclopropene derivatives [12] A surprising reaction is observed between 1 and hexafluorobutyne. 

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