[15576-81-5] · C2H6I2Si · Diiododimethylsilane · (MW 311.96)
(reducing agent; preparation of N-(iododimethylsilyl)trialkylphosphinimines, bis(2,2´-bipyridine) complexes of silicon, di-m-iodo-bis(tetracarbonyltungsten); chemistry of 7-silanorbornadienes and dimethylsilylene)
Alternate Name: dimethylsilyl diiodide.
Physical Data: bp 170 °C; d 2.203 g cm-3.
Solubility: sol most organic solvents.
Preparative Method: 8.2 g (21 mmol) of Boron Triiodide and 7.4 g (57 mmol) of Dichlorodimethylsilane are refluxed for 3 days at 120 °C; the crude product is then isolated by adding Copper powder until the color disappears followed by fractional distillation in a spinning band column apparatus (65% yield).1
Handling, Storage, and Precautions: reacts vigorously with water, but without spattering; highly toxic, flammable liquid; use in a fume hood.
This reaction can be accomplished in CH2Cl2 at rt with 1 equiv of diiododimethylsilane (eq 1).2
The reaction is far milder and more effective than comparative reductions of alcohols with Aluminum Chloride-palladium and Lithium-Ammonia. This method also permits reduction in the presence of other functional groups. A neighboring b-keto group, for example, is not reduced by diiododimethylsilane. The reaction is rapid, and reduction occurs best with secondary and tertiary a-aryl alkanols to give the corresponding alkanes in good yields.
Diiododimethylsilane reacts with various ketones in the presence of Zinc to give the corresponding reductive condensation products in good yield (eq 2).3
Reductive condensation products have been obtained from this reaction for t-BuCOMe, MeCOMe, EtCOEt, and cyclohexanone. The reaction of Me2SiI2 with Ph2CO in the presence of zinc gave benzopinacolone.
N-(Iododimethylsilyl)trialkylphosphinimines are accessible by transsilylation of the corresponding N-trimethylsilyl compounds or by the reaction of bis(trialkylphosphinimino)dimethylsilane with diiododimethylsilane (eq 3).4
In a subsequent reaction, most of the compounds undergo dimerization to form dicationic four-membered systems (eq 4). Only compounds with bulky groups at the phosphorus atom are stable as monomers.
A bis(2,2´-bipyridine) complex of silicon was synthesized by the direct reaction of 2,2´-bipyridine with diiododimethylsilane in chloroform (eq 5).5 An ionic compound is formed. In solution it contains the cis-octahedral [SiMe2(bipy)]2+ cation (1).
Hexacarbonyltungsten reacts with diiododimethylsilane to give [(CO)4WI]2 (eq 6).6 The dinuclear complex (2) is diamagnetic. The iodine atoms serve as bridging ligands between metal atoms.
7-Silanorbornadienes react rapidly with halogens at -20 °C to +20 °C to yield Me2SiX2 (X = Cl, Br, I) and the naphthalene or benzene derivatives (eq 7).7
Halogen can be abstracted from the C-Hal bond in benzyl iodide (or bromide), leading to Me2SiX2 and toluene (eq 8).7
Alkali metal halides are refined by reaction in the gas phase with alkyl-, aryl-, or alkoxyhalosilanes.8 This brings about an exchange between the Si-bound halogen and the anion of the contaminant, while the C-containing radical has a reducing effect. Diiododimethylsilane is used to purify Sodium Iodide in this manner.
Harowin O'Dowd, Laurent Deloux & Morris Srebnik
University of Toledo, OH, USA