Reactions of an Isolable Dialkylstannylene with Carbon Disulfide and Related Heterocumulenes

The reaction of isolable dialkylstannylene <b>1</b> with an excess amount of CS₂ produces an isomeric mixture of 3,3′-distanna-2,2′,4,4′-tetra­thia­bicyclo­butylidene <b>8</b> and 3,7-distanna-2,4,6,8-tetra­thia­bicyclo­[3.3.0]­oct-1(5)-ene <b>9</b> with a ratio depending on the reaction conditions. Compounds <b>8</b> and <b>9</b> are separated by column chromatography and characterized by NMR spectroscopy and X-ray crystallography. Detailed investigation of the reaction has revealed that the initial product is <b>8</b>, which isomerizes to <b>9</b> irreversibly under the catalytic influence of <b>1</b> as a Lewis acid. The above view is supported by the theoretical DFT calculations. Treatment of <b>1</b> with ArNCO [Ar = 2,6-<i>i</i>Pr₂C₆H₃] affords the corresponding carbamoyl­(hydroxyl)­stannane <b>11</b> via the hydrolysis of the corresponding sila­aziridinone formed by the [1 + 2] cycloaddition reaction of <b>1</b> with the NC double bond of the isocyanate. Stannylene <b>1</b> reacts with ArNCS, giving a mixture of complex products, while <b>1</b> does not react with CO₂

Reactions of an Isolable Dialkylstannylene with Propynoates and Benzyne

The reactions of stable monomeric dialkylstannylene <b>1</b> with methyl and ethyl propynoates give the corresponding 1:2 adducts, alkenyl­(alkynyl)­stannane <b>2</b> and <b>3</b> in high yields, while <b>1</b> does not react with parent acetylene or common mono- and disubstituted acetylenes such as phenylacetylene, trimethylsilylacetylene, diethyl 2-butynedioate, etc. Notably, <b>2</b> and <b>3</b> have the <i>Z</i>-configuration of the alkenyl moieties, in contrast to similar adducts obtained by the known reactions of silylenes with terminal acetylenes. It is suggested that the formation of a carbonyl oxygen-coordinate cyclic zwitterion as a key intermediate is essential for the reactions. Stannylene <b>1</b> adds to in situ generated benzyne, forming a 1:1 adduct having a unique 3-stanna-1-silaindane ring system

Reactions of an Isolable Dialkylstannylene with Propynoates and Benzyne

The reactions of stable monomeric dialkylstannylene <b>1</b> with methyl and ethyl propynoates give the corresponding 1:2 adducts, alkenyl­(alkynyl)­stannane <b>2</b> and <b>3</b> in high yields, while <b>1</b> does not react with parent acetylene or common mono- and disubstituted acetylenes such as phenylacetylene, trimethylsilylacetylene, diethyl 2-butynedioate, etc. Notably, <b>2</b> and <b>3</b> have the <i>Z</i>-configuration of the alkenyl moieties, in contrast to similar adducts obtained by the known reactions of silylenes with terminal acetylenes. It is suggested that the formation of a carbonyl oxygen-coordinate cyclic zwitterion as a key intermediate is essential for the reactions. Stannylene <b>1</b> adds to in situ generated benzyne, forming a 1:1 adduct having a unique 3-stanna-1-silaindane ring system

Reactions of an Isolable Dialkylsilylene with Carbon Dioxide and Related Heterocumulenes

An isolable dicoordinate dialkylsilylene, 2,2,5,5-tetrakis­(trimethylsilyl)­silacyclopentane-1,1-diyl (<b>6</b>), was found to react with CO₂ and ArNCX (X = O, S) smoothly to give the corresponding bis­(silyl)­carbonate, 4-imino-1,3-dioxasiletane and 4-imino-1,3-dithiasiletane derivatives in high yields, respectively. The molecular structures of these products were determined by X-ray crystallography. All these reactions are parallel to those of a hypercoordinate silylene with η⁵-pentamethylcyclopentadienyl ligands, decamethylsilicocene, reported by Jutzi et al. and are suggested to involve similarly the formation of the corresponding SiX doubly bonded compounds (X = O, S) at the initial steps. Mechanistic details of the multistep reaction of a model dialkylsilylene with CO₂ were investigated using DFT calculations