[4656-04-6]  · C6H18HgSi2  · Bis(trimethylsilyl)mercury  · (MW 346.97)

(precursor to trimethylsilyllithium;2 debrominates 1,2- and 1,3-dibromides;3 source of trimethylsilyl radical;4 useful reagent for preparation of metal-silicon bonds5)

Physical Data: mp 102-104 °C.

Solubility: sol diethyl ether, tetrahydrofuran, benzene, hexane, and carbon disulfide.

Form Supplied in: yellow crystals.

Preparative Methods: original procedure involves shaking Sodium Amalgam with Bromotrimethylsilane.6 The resulting bis(trimethylsilyl)mercury is readily purified by sublimation at 60 °C in vacuo. Several alternative procedures have been described.7

Handling, Storage, and Precautions: mercury and its organic derivatives are highly toxic and should be handled in an efficient fume hood. Bis(trimethylsilyl)mercury is air sensitive.

Treatment of bis(trimethylsilyl)mercury with Lithium metal in an ether or hydrocarbon solvent provides Trimethylsilyllithium (eq 1).2 This method has proved particularly useful for the generation of this lithium reagent free from additives such as HMPA.8

Bis(trimethylsilyl)mercury can be utilized for the conversion of 1,2- and 1,3-dibromoalkanes into alkenes and cyclopropanes respectively (eqs 2 and 3).3 1,2-Diiodides react in a similar fashion. Adamantene has been generated and trapped in situ with dienes using this methodology.9

Photolysis of bis(trimethylsilyl)mercury with UV light leads to the formation of a trimethylsilyl radical.4 Generation of this species in the presence of imines leads to the production of 1,2-diamines via an addition-dimerization process (eq 4).10 Under similar conditions, polyfluorinated alkenes undergo an addition-elimination reaction, producing the corresponding vinyl silanes (eq 5).11 The dealkylation of ethers such as anisole with bis(trimethylsilyl)mercury was originally speculated to involve the trimethylsilyl radical. However, more recent evidence suggests that this reaction proceeds predominantly via direct attack of the reagent on the ether linkage (eq 6).12

A number of organometallic complexes containing metal-silicon bonds have been prepared using bis(trimethylsilyl)mercury as a source of the trimethylsilyl ligand.5 Complexes derived from transition metal, lanthanide, and main group elements have all been synthesized using this chemistry.

1. (a) Fleming, I. In Comprehensive Organic Chemistry; Pergamon: Oxford, 1979; Vol. 3, p 541. (b) FF 1981, 9, 55.
2. (a) Hengge, E.; Holtschmidt, N. JOM 1968, 12, P5. (b) Hengge, E.; Holtschmidt, N. M 1968, 99, 340. (c) Schaaf, T. F.; Oliver, J. P. JACS 1969, 91, 4327.
3. Bennett, S. W.; Eaborn, C.; Jackson, R. A.; Walsingham, R. W. JOM 1971, 27, 195.
4. Gammie, L.; Safarik, I.; Strausz, O. P.; Roberge, R.; Sandorfy, C. JACS 1980, 102, 378.
5. (a) Rösch, L. AG(E) 1977, 16, 247. (b) Rösch, L. AG(E) 1977, 16, 480. (c) Blakeney, A. J.; Gladysz, J. A. JOM 1980, 202, 263. (d) Aylett, B. J. Adv. Inorg. Chem. Radiochem. 1982, 25, 1. (e) Arnold, J.; Tilley, T. D.; Rheingold, A. L.; Geib, S. J. OM 1987, 6, 473. (f) Clark, G. R.; Rickard, C. E. F.; Roper, W. R.; Salter, D. M.; Wright, L. J. PAC 1990, 62, 1039.
6. Wiberg, E.; Stecher, O.; Andrascheck, H. J.; Kreuzbichler, L.; Staude, E. AG(E) 1963, 2, 507.
7. (a) Fields, R.; Haszeldine, R. N.; Hutton, R. E. JCS(C) 1967, 2559. (b) Rösch, L; Erb, W. CB 1979, 394. (c) Eisch, J. J. Organomet. Synth., 1981, 2, 115. (d) Biffar, W.; Nöth, H.; Schwerthöffer, R. LA 1981, 2067. (e) Roesch, L.; Altnau, G.; Hahn, E.; Havemann, H. ZN(B) 1981, 36, 1234.
8. Ager, D. J.; Fleming, I.; Patel, S. K. JCS(P1) 1981, 2520.
9. Cadogan, J. I. G.; Leardini, R. CC 1979, 783.
10. Neumann, W. P.; Werner, F. CB 1978, 111, 3905.
11. (a) Fields, R.; Haszeldine, R. N.; Hubbard, A. F. JCS(C) 1971, 3838. (b) Datta, A. K.; Fields, R.; Haszeldine, R. N. JCR(S) 1980, 2.
12. Eaborn, C.; Jackson, R. A.; Walsingham, R. W. JCS(C) 1967, 2188.

Michael Shipman

Loughborough University of Technology, UK

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