Diazidotin Dichloride


[32006-05-6]  · Cl2N6Sn  · Diazidotin Dichloride  · (MW 273.64)

(electrophilic activating agent for thioacetals1)

Physical Data: white powder; explodes on heating without melting.

Solubility: insol CH2Cl2 and most org solvents; sparingly sol Me3SiCl.

Form Supplied in: white or slightly yellow high polymer.

Analysis of Reagent Purity: IR spectroscopy; explodes under microanalytical N2 determination.

Preparative Methods: from reaction of Me3SiN3 with SnCl4 (1:1 to 2:1) in CH2Cl2 or pentane at rt,2 or by oxidative addition of halogen azides to tin(II) chloride in CCl4 at 0 °C.3

Purification: almost analytically pure after washing with solvent and drying in vacuo; does not crystallize or sublime.

Handling, Storage, and Precautions: the dry solid is sensitive to hydrolysis and should be stored in the absence of moisture. Contact with metal (spatula) must be avoided and the reagent should be used only behind a safety shield. Use in a fume hood.

Thiophilic Electrophile.

Generated in situ from Azidotrimethylsilane and Tin(IV) Chloride, diazidotin dichloride converts thioacetals of cyclic ketones to imino thioethers (eq 1).1 This one step process involves generation of a thionium ion, subsequent formation of an a-azido sulfide, and Schmidt rearrangement of the latter.

Addition of Sodium Azide instead of Me3SiN3 gives better yields of imino thioethers (50-83%), but in this case difficulties are encountered on a large scale (>10 mmol) because of the heterogeneous nature of the process. For small-scale reactions, appreciably better yields (to 95%) can be obtained by using 0.5 equiv of preformed diazidotin dichloride and 1 equiv of SnCl4 in methylene chloride.1

Chemoselectivity of the process is reasonably high (eq 2)1 and thus it is possible to reverse the normal reactivity pattern of thioacetal and ketone groups.

Lewis Acid Adducts.

Diazidotin dichloride forms at rt a reasonably stable 1:1 adduct with neat Me3SiCl, precipitated as a white solid (eq 3).2 The complex decomposes without melting on heating with quantitative elimination of Me3SiCl and dissociates in solutions of organic solvents (by NMR).2,3

1. Trost, B. M.; Vaultier, M.; Santiago, M. L. JACS 1980, 102, 7929.
2. Wiberg, N.; Schmidt, K. H. CB 1967, 100, 748.
3. Dehnicke, K.; Ruschke, P. Z. Anorg. Allg. Chem. 1978, 444, 54 (CA 1978, 89, 208 381v).

Valerij A. Nikolaev

St. Petersburg State University, Russia

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