Silicon compounds silane electrophilic substitution

Treatment of aryl silane 10 with the iodonium source IC1 in an iododesilylation reaction yields compound 44, which proceeds by an ipso substitution mechanism.9 Activation towards electrophilic attack arises from stabilization of resonance form 45 by Si. Silicon is arranged / to the positive charge and the carbon-silicon bond can overlap with the empty Jt orbital (hyperconjugation). 

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. 

Summary Using a new synthetic pathway, four intramolecularly donor-stabilized silenes, R(Me3Si)Si=C(SiMe3)2 (10 R = 8-dimethylamino-l-naphthyl 11 R = 2 -(dimethylaminomethyl)phenyl 14 R = 2,6-bis(dimethylaminomethyl)phenyl 15 R = 2,6-bis(diethylaminomethyl)phenyl)), were prepared by the reaction of (dichloromethyl)tris(trimethylsilyl)silane (Ic) with the respective dialkylamino substituted aryllithium compounds (molar ratio 1 2). X-ray structural analyses of the four silenes revealed strong donor-acceptor interactions between the dialkylamino groups and the electrophilic silene silicon atoms, leading to pyramidalization at the silicon centers. The configuration at the silene carbon atoms was found to be planar. The chemical behavior of the new silenes, particularly reactions with water and methanol, treatment with methyl iodide or methyl triflate and conversions with benzaldehyde, are discussed. 

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